Institute of Applied Materials: Focke Research Groups...Alkali-assisted coal extraction with polar aproticsolvents. Fuel Processing Technology 90 (2009) 591-598. 2. G Papole, WW Focke,

Institute of Applied Materials: Focke Research Groups Contributions made during the review period, i.e. 1 January 2009 to 31 December 2016, are shown in highlighted text.

Research theme 1: Carbon technology The initial objective of our research in carbon technology was on the synthesis and characterisation of nuclear-grade graphite from local South African raw materials in support of the now defunct Pebble-Bed reactor project. Since then the focus has shifted to the use of graphite for solar energy applications, in particular thermal energy storage. In this application the high thermal conductivity of graphite is of specific interest. My own research considers graphite as a functional additive for polymers to improve fire resistance or electrical conductivity.

1.1 Synthesis & characterization of carbon precursor materials and modified graphite materials.

1. MH Makgato, LJ Moitsheki, L Shoko, BL Kgobane, DL Morgan, WW Focke. Alkali-assisted coal extraction with polar aprotic solvents. Fuel Processing Technology 90 (2009) 591-598.

2. G Papole, WW Focke, N Manyala. Characterization of medium-temperature Sasol-Lurgi gasifier coal tar pitch. Fuel 98 (2012) 243-248

3. PP Magampa, N Manyala, WW Focke. Properties of graphite composites based on natural and synthetic graphite powders and a phenolic novolac binder. Journal of Nuclear Materials 436(1–3) (2013) 76–83

4. SR Hlatshwayo, S Ramjee, WW Focke, B Rand, N Manyala. Rheological behavior and thermal properties of pitch/poly(vinyl chloride) blends. Carbon 51 (2013) 64-71.

5. WW Focke, H Badenhorst, S Ramjee, HJ Kruger, R Van Schalkwyk, Brian Rand. Graphite foam from pitch and expandable graphite. Carbon 73 (2014) 41-50.

6. S Ramjee, B Rand, WW Focke. Low Shear Rheological Behaviour of Two-Phase Mesophase Pitch. Carbon 82 (2015) 368-380.

Various carbon and graphite precursor routes were evaluated and the materials characterised (Makgato et al., 2009, Papole et al., 2012, Ramjee et al., 2015, Hlatshwayo et al., 2013).

Carbon/graphite composites were prepared and tested (Magampa et al., 2013).

A novel process, for making graphite foam, was developed (Focke et al., 2014b). It is based on the exfoliation of expandable graphite in a pitch precursor. The resulting low-cost foams feature a reasonably high thermal conductivity.

3.2 Characterising the high-temperature

Information on the oxidation behaviour of nuclear graphite

1. H Badenhorst, B Rand and WW Focke. Modelling of natural graphite oxidation using thermal analysis techniques. J Therm Anal Calorim 99 (2010) 211–228.

Meticulous use of high resolution electron microscopy and thermal analysis techniques revealed that the oxidation of even the highest purity graphite is dominated by the

oxidation of graphite

was considered important for the simulation of accident scenarios

2. H Badenhorst, B Rand and WW Focke. Geometric effects control isothermal oxidation of graphite flakes. Journal of Thermal Analysis and Calorimetry 108(3) (2012) 1141-1150.

3. H Badenhorst, B Rand, W Focke, A generalized solid state kinetic expression for reaction interface-controlled reactivity. Thermochimica Acta 562 (2013) 1-10.

4. Heinrich Badenhorst, Walter Focke. Comparative analysis of graphite oxidation behaviour based on microstructure. Journal of Nuclear Materials 442 (1-3) (2013) 75-82.

effect of catalytic impurities (Badenhorst and Focke, 2012). Mathematical models were developed for the oxidation rate of graphite materials (Badenhorst et al., 2010, Badenhorst and Focke, 2012, Badenhorst and Focke, 2013, Badenhorst et al., 2013).

3.3 Improving the fire resistance, mechanical and antistatic properties of polymers with clays and graphite

Rotomoulded, extruded and injection moulded polyolefin products used in deep level mining applications. The target in imparting fire resistance is to drive the polymer degradation reactions towards char formation as this reduces the generation of flammable fuel.

1. WW Focke, CA Strydom, N Bartie. Thermal analysis of commercial inorganic flame retardants. SA J Chem. Eng. 9(2) (1997) 41-51.

2. FJW Labuschagne, WW Focke, CA Strydom. Strong base catalysed intumescent flame retardants, J. Mat. Sci. Let. 19 (2000) 617.

3. FJWJ Labuschagné, WW Focke, CA Strydom. Metal catalyzed intumescent flame retardant systems, PMSE 220 (2000) 2.

4. K Bisschoff, WW Focke. Oxygenated Hydrocarbon Compounds as Flame Retardants for Polyester Fabric, in GL Nelson and CA Wilkie (Eds.), Fire and Polymers: Materials and Solutions for Hazard Prevention, ACS Symp. Ser. No. 297, Oxford University Press, Oxford, 2001, pp 240-250.

5. FJWJ Labuschagné, WW Focke. Metal Catalysed Intumescence: Characterisation of the thermal decomposition of calcium gluconate monohydrate. J. Mat. Sci. 38(6) (2003) 1249-1254.

6. FJWJ Labuschagné, SMC Verryn, WW Focke. X-ray powder diffraction data for ammonium d-gluconate, C6H11O7NH4+. Powder Diffr. 18(2) (2003) 162-164.

7. M Burns, U Wagenknecht, B Kretzschmar, WW Focke. Effect of hydrated fillers and red phosphorus on the limiting oxygen index (LOI) of EVA-PVB and LDPE-EVAL blends. Journal of Vinyl and Additive Technology 14 (2008) 113-119.

8. W Mhike, WW Focke and AS Luyt. Thermally conductive phase-change materials for energy storage based on low-density polyethylene, soft wax and graphite. Thermochimica Acta 527 (2012) 75-82.

9. WW Focke, H Badenhorst, W Mhike, HJ Kruger, D Lombaard. Characterization of commercial expandable graphite fire retardants. Thermochimica Acta 584 (2014) 8–16.

Incorporation of graphite, specifically expandable and graphite nanoplatelets, significantly improves the antistatic properties/electrical conductivity of polyethylene (Mhike, 2013). Graphite addition improved the thermal conductivity of thermal energy storage materials (Mhike et al., 2012). These additives also have positive effects on fire resistance of polyethylene (Mhike et al., 2015, Kruger et al., 2016, Focke et al., 2014c, Kruger, 2014, Focke, 2014, Focke et al., 2014a) and PVC (Focke et al., 2014e) in particular when used in combination with intumescent flame retardants. The problem is that the use of graphite always results in black components. Therefore, vermiculite was considered as an alternative (Muiambo et al., 2010). It also exfoliates explosively just like expandable graphite but this happens at temperatures above the degradation temperature of the polymers. It proved possible to reduce the the exfoliation onset temperature of the vermiculite (Muiambo et al., 2015, Muiambo et al., 2010) and this resulted in it providing improved flame

10. WW Focke, H Kruger, W Mhike, A Taute, A Roberson, O Ofosu. Polyethylene flame retarded with expandable graphite and a novel intumescent additive. Journal of Applied Polymer Science 131(13) (2014) 40493.

11. W Mhike, IVW Ferreira, J Li, SI Stoliarov and WW Focke. Flame retarding effect of graphite in rotationally molded polyethylene/graphite composites. J. Appl. Polym. Sci. 131 (2014) 41472.

12. H Kruger, WW Focke, W Mhike, A Taute, A Roberson, O Ofosu. Cone calorimeter study of polyethylene flame retarded with expandable graphite and intumescent fire retardant additives. Journal of Fire Sciences 32(6) (2014) 498–517.

13. W Mhike, WW Focke. Surface resistivity and mechanical properties of rotationally molded polyethylene/graphite composites. Journal of Vinyl and Additive Technology 19(4) (2013) 258-270.

14. WW Focke, H Muiambo, W Mhike, H Kruger, O Ofosu. Flexible PVC flame retarded with expandable graphite. Polymer Degradation and Stability 100 (2014) 63–69.

15. HF Muiambo, WW Focke, M Atanasova, A Benhamida. Characterization of urea-modified Palabora vermiculite. Applied Clay Science 105–106 (2015) 14-20.

16. DM Molefe, FJWJ Labuschagne, WW Focke, I van der Westhuizen, O Ofosu. Magnesium hydroxide derivatives as fire retardants for plasticized PVC. Journal of Fire Sciences 33(6) (2015) 493-510.

17. HJ Kruger, WW Focke, W Mhike, A Taute, A Roberson. Thermal properties of polyethylene flame retarded with expandable graphite and intumescent fire retardant additives. In Press: Fire and Materials.

18. W Mhike, WW Focke, JKO Asante, NI Manyala. Rotomoulded antistatic and flame retarded graphite nanocomposites. Submitted for review.

retardancy to selected polymers (Muiambo et al., 2010). Incorporating graphite into polyethylene reduces the impact strength. Good impact strength can be retained using a double dumping technique to make laminated products in which a thin outer layer, based on graphite filled EVA covers the main body made from polyethylene. Such sheets also showed excellent fire resistance in cone calorimeter tests (Mhike et al., 2016). It turned out that layered double hydroxides provide a dual function to PVC simultaneously improving heat stability and fire retardancy (Focke et al., 2009, Molefe et al., 2015, Labuschagne et al., 2015).

Research theme 2. Chemical and polymer technology

Thermal analysis techniques are used to study (a) the oxidation behaviour of materials targeting either the inhibition or enhancement of the rates of degradation or combustion; and (b) the release rates of migrating or volatile actives such as volatile corrosion inhibitors and insect repellents. The synthesis, purification and processing of clays, carbons, graphite is targeted towards additive applications in polymers. They are used to prepare and characterise polymers and polymer macro- & nanocomposites with improved properties. Of particular interest are improvements in thermo-oxidative stability, flame retardancy and controlled release of actives. Much of my research funding comes from industry and it is therefore obvious that there are market needs that the sponsors would like to address.

Technology Market need Publications Key results/findings 1.1 Volatile corrosion inhibitors

Protective film packaging for metals subjected to atmospheric corrosion. In South Africa the largest application is the use of VCI’s in polyethylene film used to wrap steel rolls. We have developed new proprietary VCI’s that are in current use for

1. WW Focke. A revised equation for estimating the vapour pressure of low-volatility substances from isothermal thermogravimetric data. J. Therm. Anal. Cal. 74 (2003) 1107-1118.

2. N Pieterse, WW Focke. Diffusion controlled evaporation through a stagnant gas: Estimating low vapour pressures from thermogravimetric data. Thermochimica Acta 406(1-2) (2003) 191-198.

3. E Vuorinen, E Kálmán, WW Focke. Introduction to vapour phase corrosion inhibitors in metal packaging. Surface Engineering 20(4) (2004) 281-284.

4. Niel Pieterse, Walter W. Focke, Eino Vuorinen and Ilona Rácz. Estimating the Vapour Pressures of Volatile Corrosion Inhibitors from Isothermal Thermogravimetric Data. Corrosion Science 48(8) (2006)1986-1995.

5. NS Nhlapo, WW Focke, E Vuorinen. TGA-FTIR study of the vapors released by triethylamine-acetic acid mixtures. Thermochimica Acta 546 (2012) 113-119.

A simple thermogravimetric technique was previously developed for the estimation of the air permeability (i.e. the product of the vapour pressure and the diffusion coefficient in air) of organic compounds (Pieterse et al., 2006, Pieterse and Focke, 2003). This knowledge is important for designing systems that rely on the release of vapours into air, e.g. volatile corrosion inhibitors and insect repellents. This TGA technique was used to develop an understanding of the evaporation mechanism of volatile corrosion inhibitors (VCI’s) (Focke et al., 2013, Nhlapo et al., 2012).

this application. For obvious reasons the nature of these additives cannot be disclosed.

6. WW Focke, NS Nhlapo, E Vuorinen. Thermal analysis and FTIR studies of volatile corrosion inhibitor model systems. Corrosion Science 77 (2013) 88-96.

1.2 Synthesis and chemical and/or physical modification of clays and other micro- or nano-sized particles

Convert synthetic & natural clays into effective polymer additives for improved physical properties. The objective here was to add value to local and Mozambiquan clay deposits as well as anionic clays synthesized by local company.

1. N Nhlapo, T Motumi, E Landman, SMC Verryn, WW Focke. Hydrotalcite: surfactant-assisted fatty acid intercalation of layered double hydroxides. Journal of Materials Science 43(3) (2008) 1033-1043.

2. L Moyo, N Nhlapo, WW Focke. A critical assessment of methods for intercalating anionic surfactants in layered double hydroxides. Journal of Materials Science 43 (2008) 6144-6158.

3. WW Focke, D Molefe, FJW Labuschagne, S Ramjee. The influence of stearic acid coating on the properties of magnesium hydroxide, hydromagnesite and hydrotalcite powders. J. Mat. Sci. 44 (2009) 6100-6109.

4. WW Focke, NS Nhlapo, L Moyo and SMC Verryn. Thermal Properties of Lauric- and Stearic Acid Intercalated Layered Double Hydroxides. Molecular Crystals and Liquid Crystals 521 (2010) 168.

5. PH Massinga Jr., WW Focke, PL de Vaal, M Atanasova. Alkyl ammonium intercalation of Mozambican bentonite. Applied Clay Science 49 (2010) 142–148.

6. HF Muiambo, WW Focke, M Atanasova, I van der Westhuizen, LR Tiedt. Thermal properties of sodium-exchanged Palabora vermiculite. Applied Clay Science 50 (2010) 51–57.

7. PJ Oberholster, N Musee, A-M Botha, PK Chelule, WW Focke, P Ashton. Assessment of the effect of nanomaterials on sediment-dwelling invertebrate Chironomus tentans larvae. Ecotoxicology and Environmental Safety 74 (2011) 416–423.

8. L Moyo, WW Focke, FJWJ Labuschagne, S Verryn. Layered Double Hydroxide Intercalated with Sodium Dodecyl Sulfate. Molecular Crystals and Liquid Crystals 555(1) (2012) 51-64.

9. HF Muiambo, WW Focke. Ion Exchanged Vermiculites with Lower Expansion Onset Temperatures. Molecular Crystals and Liquid Crystals 555(1) (2012) 65-75.

10. PH Massinga Jr., WW Focke. Intercalating Cationic Surfactants in Koppies Bentonite. Molecular Crystals and Liquid Crystals 555(1) (2012) 85-93.

New methods for the purification and synthesis of organoclays were developed. These clays were developed for use as additives in order to modify oil- and polymer properties (Focke et al., 2009, Focke et al., 2010, Massinga et al., 2010, Massinga and Focke, 2012, Moyo et al., 2012, Muiambo et al., 2015, Muiambo et al., 2010, Atanasova et al., 2016).

11. MT Atanasova, A Vyalikh, U Scheler, WW Focke. Characterization of rectorite from the Beatrix Gold Mine in South Africa. Applied Clay Science 126 (2016) 7–16.

12. R Morekhure-Mphahlele, WW Focke. Characterization of vumba and ubumba clays used for cosmetic purposes. Accepted for publication: South African Journal of Science.

1.3 Polymer nanocomposites

Improving the mechanical and other physical properties of polymers

1. EP Landman, WW Focke. Stearate intercalated layered double hydroxides: effect on the physical properties of dextrin-alginate films. Journal of Materials Science 41(8) (2006) 2271-2279.

2. EP Landman, WW Focke. Poly(vinyl sulfonate) intercalation into stearate intercalated layered double hydroxides. SAJS 102(11/12) (2007) 581-584.

3. T Gcwabaza, S Sinha Ray, WW Focke, A Maity. Morphology and properties of nanostructured materials based on polypropylene/poly(butylene succinate) blend and organoclay. European Polymer Journal 45 (2009) 353–367

4. S Joseph, WW Focke. Poly (ethylene-vinyl co-vinyl acetate) /clay nanocomposites: mechanical, morphology and thermal behavior. Polymer Composites 32(2) (2011) 252-258.

5. W Mhike, WW Focke and AS Luyt. Thermally conductive phase-change materials for energy storage based on low-density polyethylene, soft wax and graphite. Thermochimica Acta 527 (2012) 75-82.

6. A Manhique and WW Focke. Layered double hydroxides as nano additives in poly(ε-caprolactone). Mol. Cryst. Liq. Cryst. 556 (2012) 114-123.

7. L Moyo, W.W. Focke, D. Heidenreich, F.J.W.J. Labuschagne and H.-J. Radusch. Properties of layered double hydroxide micro- and nanocomposites. Materials Research Bulletin 48 (2013) 1218–1227.

8. A Mollova, I Kolesov, R Androsch, J Labuschagne, W Focke, SS Funari. Crystallization of nanocomposites of an isotactic random butene-1/ethylene copolymer and layered double hydroxide. Polym. Bull. 70 (2013) 3115-3128.

9. D Kolesov, R Androsch, D Mileva, W Lebek, A Benhamida, M Kaci, W Focke, Crystallization of a polyamide 11/organo-modified montmorillonite nanocomposite at rapid cooling. Colloid and Polymer Science 291(11) (2013) 2541-2549

10. W Focke, L Moyo, FJWJ Labuschagne, NG Hoosen, S Ramjee, M Saphiannikova. Anomalous shear viscosity-temperature behaviour of jojoba

Polymer nanocomposites with improved functional and mechanical properties were prepared and characterised (Joseph and Focke, 2011, Manhique et al., 2012, Mhike et al., 2012, Moyo et al., 2013, Massinga et al., 2014, MacHeca et al., 2016, Macheca et al., 2013).

Some nanoparticles acted as excellent nucleating agents facilitating rapid crystallization of selected polymers even at extremely high cooling rates (Mollova et al., 2013, Kolesov et al., 2013).

Organo-modification of clays with the matric polymer itself proved feasible for polyamides and led to materials with significantly improved stiffness (Focke et al., 2016a, MacHeca et al., 2016, Macheca et al., 2013, Jariyavidyanont et al., 2016).

oil-LDH-stearate suspensions. Colloids and Surfaces A: Physicochemical and Engineering Aspects 443C (2014) 391-397.

11. A Macheca, D Gnanasekaran, WW Focke. Surfactant-free dimer fatty acid polyamide/montmorillonite bio-nanocomposites. Colloid and Polymer Science 292(3) (2014) 669-676 .

12. PH Massinga Jr., WW Focke, O del Fabbro, H-J Radusch. EVA nanocomposites based on South African Koppies clay. Journal of Vinyl and Additive Technology 20(3) (2014) 143–151.

13. D Gnanasekaran, A Shanavas, WW Focke WW, R Sadiku. Polyhedral oligomeric silsesquioxane/polyamide bio-nanocomposite membranes: Structure-gas transport properties. RSC Advances 5(15) (2015) 11272-11283.

14. D Gnanasekaran, PH Massinga Jr, WW Focke. Chapter 3. EVA (Ethylene-Co-Vinyl Acetate) Composites in Nanoscale: Research Methodology and Developments. In: Nekane Guarrotxena (Ed.) Research Methodology in Physics and Chemistry of Surfaces and Interfaces. August 4, 2014. Apple Academic Press: Oakville ISBN 9781771880114.

15. AD Macheca, WW Focke, HF Muiambo, M Kaci. Stiffening mechanisms in vermiculite–amorphous polyamide bio-nanocomposites. European Polymer Journal 74 (2016) 51-63.

16. K Jariyavidyanont, W Focke, R Androsch. Crystallization kinetics of polyamide 11 in the presence of sepiolite and montmorillonite nanofillers. Colloid Polym Sci 294 (2016) 1143–1151.

1.4 Characterising and modulating the heat stability of PVC and the thermal- and UV degradation of polyolefins and biodiesel

Stabilisation of polymers, carbon materials or biodiesel and against oxidative degradation mediated by heat or UV radiation. An important focus was to reduce the visual impact of litter

1. WW Focke, I van der Westhuizen. Oxidation induction time (OIT) and oxidation onset temperature (OOT) of polyethylene in air. Testing Gimzewski's postulate. J Therm Anal Calorim 99 (2010) 285–293.

2. WW Focke, I van der Westhuizen, ABL Grobler, KT Ntshoane, JK Reddy and AS Luyt. The effect of synthetic antioxidants on the oxidative stability of biodiesel. Fuel 94 (2012) 227–233.

3. WW Focke, I van der Westhuizen, X Oosthuysen. Biodiesel oxidative stability from Rancimat data. Thermochimica Acta 633 (2016) 116–121.

4. II Eyenga, WW Focke, LC Prinsloo, AT Tolmay. Photodegradation: A Solution for the Shopping Bag Visual Pollution Problem? S. A. Journal of Science, 97 (2001) 359-362.

For quality control purposes it is common to use either the isothermal oxidation induction times (OIT) or the dynamically evaluated oxidation onset temperatures (OOT) as measures of the oxidative stability of a polyethylene and polypropylene. It was found that these quantities are related in that they correspond to the similar level of antioxidant depletion (Focke and Van Der Westhuizen, 2010).

from plastic packaging and plastic shopping bags. This was achieved by enhancing the UV degradation rate of polyolefin films but also required their restabilisation to facilitate recycling

5. II Eyenga, WW Focke, LC Prinsloo, AT Tolmay. Photodegradation: A solution for the shopping bag "visual pollution" problem? Macromolecular Symposia 178 (2002) 139-152.

6. WW Focke. Plastic film litter: Is there really a role for oxo-(bio)degradation? Journal of Vinyl and Additive Technology 14 (2008) 153-154.

7. B Magagula, N Nhlapo, WW Focke. Mn2Al-LDH- and Co2Al-LDH-stearate as photo degradants for LDPE film. Polymer Degradation and Stability 94 (2009) 947-954.

8. WW Focke, RP Mashele and NS Nhlapo. Stabilization of LDPE films containing metal stearates as photodegradants. Journal of Vinyl and Additive Technology 17 (2011) 21-27.

9. F Labuschagne, DM Molefe, WW Focke, I van der Westhuizen I, HC Wright, MD Royeppen. Heat stabilising flexible PVC with layered double hydroxide derivatives. Polymer Degradation and Stability 113 (2015) 46–54.

10. M Kaci, WW Focke, EM van der Merwe. The Effects of Various Clays on Photo-oxidation of Polyamide 11 Bio-nanocomposites under Accelerated UV Test. Submitted for review in 2016.

It was found that sunflower-derived biodiesel is particularly prone to oxidative degradation (Focke et al., 2012b). A new method for estimating the oxidative stability of biodiesel from Rancimat data was proposed (Focke et al., 2016b). Fatty acid intercalated transition metal layered double hydroxides and metal stearates were found to be effective photo-prodegradants (Focke et al., 2011, Magagula et al., 2009). It also proved possible to re-stabilise polyethylene containing the latter by adding phosphite-based anti-oxidants (Focke et al., 2011). This means that the use of oxo-prodegradants does not preclude the recycling of the polymers.

1.5 Adhesives, binders, polymers, resins and polymer blends

1. WA Germishuizen, WW Focke and AT Visser. A laboratory study of soil stabilisation with an urea-formaldehyde resin. Journal of the South African Institution of Civil Engineers 44 (2002) 9-12.

2. M Govender, WW Focke, AT Tolmay, D Graefe. Evaluation of commercial plastics purging compounds on a laboratory film blower. SA J Chem. Eng. 14(1) (2002) 16-27.

3. E Vuorinen, WW Focke, A Gandini, M Govender. Sythesis of adhesive polyethylene polymers using free radical grafting in a compounding extruder. SA J Chem. Eng. 14(2) (2002) 1-5.

4. E Karakatsanis, WW Focke, G Summers. Low Molecular Mass Poly(styrene-co-acrylic acid) Amphiphilic Block Copolymers: Synthesis and Characterization. Macromol. Symp. 193 (2003) 187-193.

5. WA Germishuizen, WW Focke, AT Visser, A Laboratory Optimisation of a urea-formaldehyde Soil Stabiliser. SA J Chem. Eng. 15(1) (2003) 1-16.

6. FS Moolman, H Rolfes, SW Van der Merwe, WW Focke. Optimization of perfluorocarbon emulsion properties for enhancing mass transfer in a bio-artificial liver support system. Biochem. Eng. J. 19(3) (2004) 237-250.

A urea-formaldehyde resins system was optimised for soil binder application. This allows rapid and cost effective road construction when asphalt is not available. Biopolymers were

7. E Karakatsanis, WW Focke, G Summers. Surfactant-assisted micro-mixing of melamine and wax particles. Journal of Applied Polymer Science 99(5) (2006) 2554-2557.

8. C Sita, M Burns, WW Focke. Tensile properties of thermoplastic starch-PVB blends. J. Appl. Polym. Sci. 101(3) (2006) 1751-1755.

9. S Pecku, TL van der Merwe, H Rolfes, WW Focke. Starch as antiblocking agent in breathable polyurethane membranes. Journal of Vinyl and Additive Technology 13(4) (2007) 215-220.

10. SS Ochigbo, AS Luyt, WW Focke. Latex derived blends of poly(vinyl acetate) and natural rubber: thermal and mechanical properties. Journal of Materials Science 44(12) (2009) 3248 - 3254

11. WW Focke, S Joseph, J Grimbeek, G Summers, B Kretzschmar. Mechanical properties of ternary blends of ABS + HIPS + PETG. Polymer-Plastics Technology and Engineering 48 (2009) 814-820.

12. WE Cloete and WW Focke. Photoinitiated Cyanoacrylates for Fast Underwater Bonding. International Journal of Adhesion & Adhesives 30 (2010) 208–213.

13. S Joseph, WW Focke and S Thomas. Compatibilizing action of a poly(styrene-butadiene) triblock copolymer in ABS/PET-G blends. Composite Interfaces 17 (2010) 175-196.

14. AS Chetty, V Vargha, A Maity, FS Moolman, C Rossouw, R Anandjiwala, L Boguslavsky, D Mancama, WW Focke. Development of thermoresponsive poly(propylene-g-N-isopropylacrylamide) non-woven 3D scaffold for smart cell culture using oxyfluorination-assisted graft polymerisation. Colloids and Surfaces A: Physicochemical and Engineering Aspects 419 (2013) 37-45.

1.6 Metal extraction & processing

Moulding compound for investment casting. Metal injection moulding.

1. WJ de Wet, WW Focke, Improved Sulphuric Acid Sulphation of Refractory Zirconia by Addition of Sodium Sulphate. SA J Chem. Eng. 11(2) (1999) 29-37.

2. A Kruger, WW Focke, Z Kwela, R Fowles. Effect of Ionic Impurities on the Crystallization of Gypsum in Wet-Process Phosphoric Acid. Ind. Eng. Chem. Res. 40 (2001) 1364-1369.

3. A Kruger, WW Focke, Z Kwela, R Fowles. Effect of Ferrous and Ferric Iron Impurities on the Crystallization of Gypsum and Sludge formation in Wet-Process Phosphoric Acid. Chemical Engineering Communications 189 (2002) 684 – 694.

4. A Manhique, Z Kwela, WW Focke, The De Wet Process for the Beneficiation of Zircon: Optimization of the Alkali Fusion Step. Ind. Eng. Chem. Res. 42 (2003) 777-783.

5. H Rutto, WW Focke. Thermo-Mechanical Properties of Urea-Based Pattern Molding Compounds for Investment Casting. International Polymer Processing 25(1) (2010) 15-22.

6. AJ Manhique, WW Focke, C Madivate. Titania recovery from low-grade titanoferous minerals. Hydrometallurgy 109 (2011) 230–236.

7. M Seerane, H Chikwanda, W Focke, R Machaka. A Study of Solvent Debinding Variables on Ti6Al4V Green Bodies. Advanced Materials Research 1019 (2014) 204-209.

Research theme 3. Malaria vector control

Controlled release of actives such as insecticides and repellents from polymer matrices 4.1 Controlled release of insecticides and insect repellents for malaria vector control

My malaria research group collaborates with several researchers in the UP Institute of Sustainable Malaria Control. Our research focus is informed by the research results on public health researchers and entomologists. We form part of

1. MM Sibanda, WW Focke, FJ Labuschagne, L Moyo, NS Nhlapo, A Maity, H Muiambo, P Massinga, NA Crowther, M Coetzee, GW Brindley. Degradation of insecticides used for indoor spraying in malaria control and possible solutions. Malaria Journal 10 (2011) 307.

2. WW Focke, W van Pareen. Polypropylene-based long-life insecticide-treated mosquito netting. Journal of Polymer Engineering 31(6-7) (2011) 521-529.

3. RD Merckel, WW Focke, MM Sibanda, P Massinga, NAS Crowther. Co-Intercalation of Insecticides with Hexadecyltrimethylammonium Chloride in Mozambican Bentonite. Molecular Crystals and Liquid Crystals 555(1) (2012) 76-84.

4. L Birkholtz, R Bornman, W Focke, C Mutero, C Jager. Sustainable malaria control: transdisciplinary approaches for translational applications. Malaria Journal 11 (2012) 431.

New approaches for both indoor and outdoor protection against malaria transmission were developed (Sibanda et al., 2016, Kruger et al., 2015, Sibanda et al., 2011, Merckel et al., 2012, Focke and Van Pareen, 2011, Akhtar and Focke, 2015). A polypropylene bed net based on betacyflutrin is able to withstand the large number of washes prescribed by WHO specifications (Focke and Van Pareen, 2011). The trick is the use of crystalline insecticide that does not melt at wash temperatures. Despite serious health concerns, indoor spraying of DDT is still practised in Southern Africa. The reason is the poor environmental stability of safer insecticides. Through a Bill & Melinda Gates Foundation grant, it was found that this is mainly caused by catalytic hydrolysis (Sibanda et al., 2011). It was found possible to stabilise WHO-approved pyrethroid insecticides by absorbing them on a low pH

the malaria vector control activity in this large multidisciplinary research activity of the University of Pretoria

5. M Sibanda, WW Focke. Development of an insecticide impregnated polymer wall lining for malaria vector control. Malaria Journal 13(Suppl 1) (2014) P80.

6. T Kruger T, MM Sibanda, WW Focke, MS Bornman, C de Jager. Acceptability and effectiveness of a monofilament, polyethylene insecticide-treated wall lining for malaria control after six months in dwellings in Vhembe District, Limpopo Province, South Africa. Malaria Journal 14 (2015) 485.

7. MU Akhtar, WW Focke. Trapping citronellal in a microporous polyethylene matrix. Thermochimica Acta 613 (2015) 61-65.

8. H Izadi, WW Focke, R Maharaj, J Pretorius. A promising azeotrope-like mosquito repellent blend. Submitted for review in 2016.

9. IVW Ferreira, EL Du Toit, WW Focke. Micro-encapsulation of the essential oil component, geraniol, in zein. submitted for review in 2016

filler such as phosphogypsum (Sibanda et al., 2016) or by co-intercalating them in clays (Merckel et al., 2012). In laboratory tests such materials outperformed DDT even on cow dung coated surfaces. Even better performance was achieved by incorporating the insecticides into a low-cost polyethylene wall lining (Kruger et al., 2015). Field trials and bioassays have shown that the efficacy of these linings is retained for several years (Kruger et al., 2015). This technology is now being licenced to a commercial company for wider application. A novel approach for improved topical mosquito repellents was found. It relies on the formulation of blends that show negative azeotrope behaviour (Izadi et al., Submitted for review in 2016). In that way the vapour pressure is reduced and therefore the release rate into ambient is decreased and the repellence effect is retained for a longer time period. Two such blends were discovered to date. Surprisingly, a welcome side effect was observed during repellence testing: the azeotropic blend did not just repel but actually also caused mosquitoes mortality!

Research theme 4. Mixture models

Mathematical models for the description of multicomponent mixture properties 5.1 Mixture models

This is my hobby subject!

1. WW Focke. A New Three-parameter Activity Coefficient Correlation for Modelling Liquid Phase Behaviour. Part 1: Theory. SA J Chem. Eng. 12(1) (2000) 35-46.

2. WW Focke. Local Composition Structured Fluid Model for the Excess Gibbs Energy of Liquid Mixtures. Ind. Eng. Chem. Res. 40 (2001) 2971-2981.

3. WW Focke, A Manhique, R Carter. Lattice Model for Estimating the Opacity of White Coatings. J. Am. Ceram. Soc. 85(5) (2002) 1139-44.

Novel mixture models were developed that show improved data correlation properties (Ackermann et al., 2012, Focke et al., 2012a). It was shown that most of the thermodynamic activity coefficient models are just special cases of the Weighted-Power-Mean Mixture model (Focke, 2009).

4. WW Focke. A New Three-parameter Activity Coefficient Correlation for Modelling Liquid Phase Behaviour. Part 2: Application to binary Vapour-Liquid Equilibrium at low Pressures. SA J Chem. Eng. 13(1) (2001) 1-16.

5. WW Focke. Excess Gibbs Energy of Binary Liquid Mixtures and the Wong-Sandler Postulates. AIChE J. 50(12) (2004) 3284-3289.

6. CJR Verbeek, WW Focke. Modelling the Young’s modulus of platelet reinforced thermoplastic sheet composites. Composites: Part A 33 (2003) 1697-1704.

7. WW Focke, B Du Plessis. Correlating Multicomponent Mixture Properties with Homogeneous Rational Functions. Industrial and Engineering Chemistry Research 43(26) (2004) 8369-8377.

8. WW Focke. Neural network averaging. Neural Computation 18 (2005) 1-9.

9. WW Focke, M Grobler. Low-pressure vapor-liquid data reduction using only equilibrium composition data. J. Chem. Eng. Japan 39(2) (2006) 114-120

10. C Sandrock, WW Focke, S Kok. Weighted-power-mean mixture model: Empirical mixing laws for liquid viscosity. Ind. Eng. Chem. Res. 46 (2007) 4660-4666.

11. WW Focke. Mixture model for correlating excess enthalpy data. J. Chem. Eng. Jpn. 40 (2007) 295-303.

12. WW Focke. Correlating Thermal Conductivity Data for Ternary Liquid Mixtures. International Journal of Thermophysics 29(4) (2008) 1342-1360

13. WW Focke. Weighted-Power-Mean Mixture Model for the Gibbs Energy of Fluid Mixtures. Ind. Eng. Chem. Res. 48 (2009) 5537–5541.

14. RLJ Coetzer, WW Focke. Optimal designs for estimating the parameters in weighted power-mean-mixture models. Journal of Chemometrics 24(1) (2010) 34- 42.

15. WW Focke, MH Ackermann, RLJ Coetzer. Mixture rules based on power means and generalized q-fractions. Journal of Chemical Engineering of Japan 25(1) (2012) 1-8

Optimal experimental designs were derived for estimating the parameters in weighted power-mean-mixture models (Coetzer and Focke, 2010).

The single-step chemical approximation approach was used to derive a full dose-time-response model that could have wide-ranging application in applications dealing with the effects of fertiliser on agricultural yield, toxins or therapeutics on survival, stress on component reliability, etc. Biodiesel “survival” curves were used as a proxy to test the applicability of the empirical model to describe the effects of inhibitor dosage and binary inhibitor mixtures (Focke et al., Submitted for review in 2016).

16. MH Ackermann, WW Focke, RLJ Coetzer. Analysis of the q-fractions weighted power mean mixture models. Journal of Chemical Engineering of Japan 25(1) (2012) 9-20

17. WW Focke, I van der Westhuizen, N Musee, MT Loots. Kinetic interpretation of log-logistic dose-time response curves. Submitted for review in 2016.

5. Pyrotechnics

2.1 Develop “green” pyrotechnic compositions

Green time delays and initiating compositions for chemical mine detonators

1. IMM Ricco, C Conradie, WW Focke, Alternative Oxidants for Silicon Fuel in Time Delay Detonators. Combustion Science and Technology 176 (9) (2004) 1565-1575.

2. L Kalombo, O Del Fabbro, C Conradie, WW Focke. Sb6O13 and Bi2O3 as oxidants for Si in pyrotechnic time delay compositions. Propellants, Explosives, Pyrotechnics 32(6) (2007) 454-460.

3. D Swanepoel, O Del Fabbro, WW Focke and C Conradie. Manganese as Fuel in Slow-Burning Pyrotechnic Time Delay Compositions. Propellants Explos. Pyrotech. 35 (2010) 105 - 113.

4. K Ilunga, O del Fabbro, L Yapi and WW Focke. The effect of Si-Bi2O3 on the ignition of the Al-CuO thermite. Powder Technology 205 (2011) 97–102.

5. SM Tichapondwa, WW Focke, O Del Fabbro, S Mkhize and E Muller. Suppressing H2 Evolution by Silicon Powder Dispersions. J Energetic Materials 29(4) (2011) 326-343.

New “green” pyrotechnic formulations suitable for short-, medium- and long-time delay applications were developed (Tichapondwa et al., 2016a, Tichapondwa et al., 2016b, Montgomery et al., 2016, Tichapondwa et al., 2015, Ilunga et al., 2011, Swanepoel et al., 2010). The Mn-MnO2 system (Swanepoel et al., 2010) was patented as a “green” medium burning rate system. It is unique in that it features a metal reacting with its own “rust”! Three novel approaches to reduce the evolution of hydrogen gas by aqueous

6. SM Tichapondwa, WW Focke, O Del Fabbro, E Muller. Suppressing Hydrogen Evolution by Aqueous Silicon Powder Dispersions by Controlled Silicon Surface Oxidation. Propellants, Explosives, Pyrotechnics 38(1) (2013) 48–55

7. SM Tichapondwa, WW Focke, O Del Fabbro, RF Sandenbergh. Suppressing hydrogen evolution by aqueous silicon powder dispersions through the introduction of additional cathodic reaction. Chemical Engineering Communications 201(4) (2014) 501-515.

8. WW Focke, M Atanasova, SS Mkhize, R Storey, O Del Fabbro, E Muller. Facile synthesis of copper antimonite. Chemical Engineering Communications 201(2) (2014) 153-159.

9. MT Atanasova, AM Strydom, CJH Schutte, LC Prinsloo, WW Focke. Crystal structure and magnetic properties of CuSb2O4. Journal of Materials Science 49(9) (2014) 3497-3510.

10. SM Tichapondwa, WW Focke, O Del Fabbro, C Kelly. Calcium Sulfate as a Possible Oxidant in “Green” Silicon-based Pyrotechnic Time Delay Compositions. Propellants, Explosives, Pyrotechnics 40(4) (2015) 518-525.

11. SM Tichapondwa, WW Focke, O del Fabbro, J Gisby, C Kelly. A Comparative Study of Si-BaSO4 and Si-CaSO4 Pyrotechnic Time-Delay Compositions. Journal of Energetic Materials 34(3) (2016) 342-356.

12. SM Tichapondwa, WW Focke, O Del Fabbro. The effect of additives on the burning rate of the silicon-calcium sulfate pyrotechnic delay compositions. Propellants, Explosives, Pyrotechnics 41 (2016) 732-739

13. YC Montgomery, WW Focke, M Atanasova, O Del Fabbro, C Kelly. Mn + Sb2O3 thermite/intermetallic delay compositions. Propellants, Explosives, Pyrotechnics 41 (2017) 919-925.

14. G Potgieter, WW Focke, O Del Fabbro, GD Labuschagné, C Kelly. Fluoroelastomer pyrotechnic time delay compositions. Journal of Thermal Analysis and Calorimetry 126 (2016) 1363-1370.

15. YC Montgomery, WW Focke, C Kelly. Measurement and Modelling of Pyrotechnic Time Delay burn rates: Method and Model development. Submitted for review.

silicon dispersion were found (Tichapondwa et al., 2013, Tichapondwa et al., 2011, Tichapondwa et al., 2014). A novel approach to prepare a robust pyrotechnic formulation was found. In this system both a redox and an intermetallic reaction keep the energy output at a plateau value over a relatively wide stoichiometric range (Montgomery et al., 2016). A sophisticated numerical model for the prediction of burn rates of time delays was developed (Montgomery et al., 2017). It makes it possible to optimise such systems. The apparent chemical reaction kinetics of both slow and fast burning compositions were indirectly inferred from the temporal evolution of surface temperature on the outside of burning columns. Copper antimonite with silicon as fuel gives particularly insensitive pyrotechnic formulations. A new way of synthesising this interesting oxidiser was developed (Focke et al., 2014d). Its unique crystal structure and unusual magnetic properties were studied (Atanasova et al., 2014).

http://www.scopus.com/source/sourceInfo.url?sourceId=16393&origin=resultslist

Best five papers 2009 to present based on one each from

Carbon technology:

WW Focke, H Badenhorst, S Ramjee, HJ Kruger, R Van Schalkwyk, Brian Rand. Graphite foam from pitch and expandable graphite. Carbon 73 (2014) 41-50.

Chemical and Polymer technology:

N Nhlapo, T Motumi, E Landman, SMC Verryn, WW Focke. Surfactant-assisted fatty acid intercalation of layered double hydroxides. Journal of Materials Science 43 (3), 1033-1043

Malaria vector control:

MM Sibanda, WW Focke, FJ Labuschagne, L Moyo, NS Nhlapo, A Maity, H Muiambo, P Massinga, NA Crowther, M Coetzee, GW Brindley. Degradation of insecticides used for indoor spraying in malaria control and possible solutions. Malaria Journal 10 (2011) 307.

Mixture models:

WW Focke. Weighted-Power-Mean Mixture Model for the Gibbs Energy of Fluid Mixtures. Ind. Eng. Chem. Res. 48 (2009) 5537–5541.

Pyrotechnics:

YC Montgomery, WW Focke, M Atanasova, O Del Fabbro, C Kelly. Mn + Sb2O3 thermite/intermetallic delay compositions. Propellants, Explosives, Pyrotechnics 41 (2017) 919-925.

Most cited documents in each category

Google Scholar most cited articles Field Reference Citations Year Chemical & polymer technology

Influence of oxidation state, pH, and counterion on the conductivity of polyaniline WW Focke, GE Wnek, Y Wei Journal of Physical Chemistry 91 (22), 5813-5818

416 1987

Chemical & polymer technology

Flow visualization in parallel-plate ducts with corrugated walls WW Focke, PG Knibbe Journal of Fluid Mechanics 165, 73-77

130 1986


Conduction mechanisms in polyaniline (emeraldine salt) WW Focke, GE Wnek Journal of electroanalytical chemistry and interfacial electrochemistry 256 ...

88 1988


The effect of synthetic antioxidants on the oxidative stability of biodiesel WW Focke, I Van der Westhuizen, ABL Grobler, KT Nshoane, JK Reddy, ... Fuel 94, 227-233

56 2012


Surfactant-assisted fatty acid intercalation of layered double hydroxides N Nhlapo, T Motumi, E Landman, SMC Verryn, WW Focke Journal of Materials Science 43 (3), 1033-1043

47 2008


Mn 2 Al-LDH-and Co 2 Al-LDH-stearate as photodegradants for LDPE film B Magagula, N Nhlapo, WW Focke Polymer Degradation and Stability 94 (6), 947-954

42 2009


Diffusion-controlled evaporation through a stagnant gas: estimating low vapour pressures from thermogravimetric data N Pieterse, WW Focke Thermochimica acta 406 (1), 191-198

39 2003


A critical assessment of the methods for intercalating anionic surfactants in layered double hydroxides L Moyo, N Nhlapo, WW Focke Journal of materials science 43 (18), 6144-6158

38 2008

Carbon technology

Thermally conductive phase-change materials for energy storage based on low-density polyethylene, soft Fischer–Tropsch wax and graphite W Mhike, WW Focke, JP Mofokeng, AS Luyt Thermochimica acta 527, 75-82

37 2012


Thermal properties of sodium-exchanged palabora vermiculite HF Muiambo, WW Focke, M Atanasova, I Van der Westhuizen, LR Tiedt Applied Clay Science 50 (1), 51-57

35 2010


Morphology and properties of nanostructured materials based on polypropylene/poly (butylene succinate) blend and organoclay T Gcwabaza, SS Ray, WW Focke, A Maity

33 2009

https://scholar.google.co.za/scholar?oi=bibs&hl=en&cites=15878198109468722614https://scholar.google.co.za/scholar?oi=bibs&hl=en&cites=15266494397410464154https://scholar.google.co.za/scholar?oi=bibs&hl=en&cites=12334019013500449476https://scholar.google.co.za/citations?view_op=view_citation&hl=en&user=INwHJUx8QW8C&citation_for_view=INwHJUx8QW8C:roLk4NBRz8UChttps://scholar.google.co.za/scholar?oi=bibs&hl=en&cites=8208055228326504351https://scholar.google.co.za/scholar?oi=bibs&hl=en&cites=7979063613220413482https://scholar.google.co.za/scholar?oi=bibs&hl=en&cites=14188448493288886283https://scholar.google.co.za/citations?view_op=view_citation&hl=en&user=INwHJUx8QW8C&citation_for_view=INwHJUx8QW8C:Y0pCki6q_DkChttps://scholar.google.co.za/scholar?oi=bibs&hl=en&cites=13522334497691493932https://scholar.google.co.za/scholar?oi=bibs&hl=en&cites=8885028318205056775https://scholar.google.co.za/scholar?oi=bibs&hl=en&cites=11076490769506433812https://scholar.google.co.za/scholar?oi=bibs&hl=en&cites=2643306984903018955

European Polymer Journal 45 (2), 353-367 Chemical & polymer technology

Photodegradation: a solution for the shopping bag “visual pollution” problem? II Eyenga, WW Focke, LC Prinsloo, AT Tolmay Macromolecular Symposia 178 (1), 139-152

26 2002


Alkyl ammonium intercalation of Mozambican bentonite PH Massinga, WW Focke, PL De Vaal, M Atanasova Applied Clay Science 49 (3), 142-148

25 2010


Titania recovery from low-grade titanoferrous minerals AJ Manhique, WW Focke, C Madivate Hydrometallurgy 109 (3), 230-236

24 2011

Pyrotechnics The effect of Si–Bi2O3 on the ignition of the Al–CuO thermite K Ilunga, O Del Fabbro, L Yapi, WW Focke Powder Technology 205 (1), 97-102

22 2011


A revised equation for estimating the vapour pressure of low-volatility substances from isothermal TG data W Focke Journal of thermal analysis and calorimetry 74 (1), 97-107

20 2003


De Wet process for the beneficiation of zircon: optimization of the alkali fusion step A Manhique, Z Kwela, WW Focke Industrial & engineering chemistry research 42 (4), 777-783

20 2003


Differential scanning calorimetry analysis of thermoset cure kinetics: phenolic resole resin WW Focke, MS Smit, AT Tolmay, LS Van der Walt, WL Van Wyk Polymer Engineering & Science 31 (23), 1665-1669

20 1991

Carbon technology

Alkali-assisted coal extraction with polar aprotic solvents MH Makgato, LJ Moitsheki, L Shoko, BL Kgobane, DL Morgan, WW Focke Fuel Processing Technology 90 (4), 591-598

19 2009


The influence of stearic acid coating on the properties of magnesium hydroxide, hydromagnesite, and hydrotalcite powders WW Focke, D Molefe, FJW Labuschagne, S Ramjee Journal of materials science 44 (22), 6100-6109

18 2009


Latex derived blends of poly (vinyl acetate) and natural rubber: thermal and mechanical properties SS Ochigbo, AS Luyt, WW Focke Journal of materials science 44 (12), 3248-3254

18 2009


Introduction to vapour phase corrosion inhibitors in metal packaging E Vuorinen, E Kalman, W Focke Surface engineering

17 2013

Carbon technology

Graphite foam from pitch and expandable graphite WW Focke, H Badenhorst, S Ramjee, HJ Kruger, R Van Schalkwyk, ... Carbon 73, 41-50

16 2014

https://scholar.google.co.za/scholar?oi=bibs&hl=en&cites=2950866747443859898https://scholar.google.co.za/scholar?oi=bibs&hl=en&cites=5674136911163958952https://scholar.google.co.za/scholar?oi=bibs&hl=en&cites=12415648828405552931https://scholar.google.co.za/scholar?oi=bibs&hl=en&cites=13754328438465396379https://scholar.google.co.za/scholar?oi=bibs&hl=en&cites=1446341088747604057https://scholar.google.co.za/scholar?oi=bibs&hl=en&cites=17617557474388417577https://scholar.google.co.za/scholar?oi=bibs&hl=en&cites=13733000313090676898https://scholar.google.co.za/scholar?oi=bibs&hl=en&cites=16003307761448706586https://scholar.google.co.za/scholar?oi=bibs&hl=en&cites=9631911823202019174https://scholar.google.co.za/citations?view_op=view_citation&hl=en&user=INwHJUx8QW8C&cstart=20&citation_for_view=INwHJUx8QW8C:_FxGoFyzp5QChttps://scholar.google.co.za/scholar?oi=bibs&hl=en&cites=18209218506390338540https://scholar.google.co.za/scholar?oi=bibs&hl=en&cites=6417441212148296059https://scholar.google.co.za/scholar?oi=bibs&hl=en&cites=5010575844778340225

Pyrotechnics Sb6O13 and Bi2O3 as oxidants for Si in pyrotechnic time delay compositions L Kalombo, O Del Fabbro, C Conradie, WW Focke Propellants, Explosives, Pyrotechnics 32 (6), 454-460

15 2007

Mixture models Correlating multicomponent mixture properties with homogeneous rational functions WW Focke, B Du Plessis Industrial & engineering chemistry research 43 (26), 8369-8377

15 2004


Effect of ionic impurities on the crystallization of gypsum in wet-process phosphoric acid A Kruger, WW Focke, Z Kwela, R Fowles Industrial & Engineering Chemistry Research 40 (5), 1364-1369

15 2001

Pyrotechnics Alternative oxidants for silicon fuel in time-delay compositions IMM Ricco, WW Focke, C Conradie Combustion science and technology 176 (9), 1565-1575

14 2004


Optimization of perfluorocarbon emulsion properties for enhancing oxygen mass transfer in a bio-artificial liver support system FS Moolman, H Rolfes, SW Van der Merwe, WW Focke Biochemical engineering journal 19 (3), 237-250

14 2004


Modelling the Young's modulus of platelet reinforced thermoplastic sheet composites CJR Verbeek, WW Focke Composites Part A: Applied Science and Manufacturing 33 (12), 1697-1704

14 2002

Carbon technology

Flexible PVC flame retarded with expandable graphite WW Focke, H Muiambo, W Mhike, HJ Kruger, O Ofosu Polymer Degradation and Stability 100, 63-69

13 2014

Pyrotechnics Manganese as Fuel in Slow‐Burning Pyrotechnic Time Delay Compositions D Swanepoel, O Del Fabbro, WW Focke, C Conradie Propellants, Explosives, Pyrotechnics 35 (2), 105-113

13 2010


Oxidation induction time and oxidation onset temperature of polyethylene in air WW Focke, I Van Der Westhuizen Journal of thermal analysis and calorimetry 99 (1), 285-293

13 2010


Metathesis of fatty esters derived from South African sunflower oil CP Nicolaides, JH Opperman, MS Scurrell, WW Focke Journal of the American Oil Chemists’ Society 67 (6), 362-363

13 1990

Carbon technology

Modelling of natural graphite oxidation using thermal analysis techniques H Badenhorst, B Rand, WW Focke Journal of thermal analysis and calorimetry 99 (1), 211-228

12 2010


Tensile properties of thermoplastic starch‐PVB blends C Sita, M Burns, R Häβler, WW Focke Journal of applied polymer science 101 (3), 1751-1755

12 2006

https://scholar.google.co.za/scholar?oi=bibs&hl=en&cites=219279164713938587https://scholar.google.co.za/scholar?oi=bibs&hl=en&cites=7647983433388667160https://scholar.google.co.za/scholar?oi=bibs&hl=en&cites=14095478272297369354https://scholar.google.co.za/scholar?oi=bibs&hl=en&cites=13751934205606501656https://scholar.google.co.za/scholar?oi=bibs&hl=en&cites=2836717872745024422https://scholar.google.co.za/scholar?oi=bibs&hl=en&cites=5627647065917186039https://scholar.google.co.za/scholar?oi=bibs&hl=en&cites=3139862868582606493https://scholar.google.co.za/scholar?oi=bibs&hl=en&cites=15480528639601722869https://scholar.google.co.za/scholar?oi=bibs&hl=en&cites=13554712073966168747https://scholar.google.co.za/scholar?oi=bibs&hl=en&cites=17449249761812660416https://scholar.google.co.za/scholar?oi=bibs&hl=en&cites=6671636190010166166https://scholar.google.co.za/scholar?oi=bibs&hl=en&cites=9093473801846167345


Properties of layered double hydroxide micro-and nanocomposites L Moyo, WW Focke, D Heidenreich, FJWJ Labuschagne, HJ Radusch Materials Research Bulletin 48 (3), 1218-1227

11 2013

Mixture models Weighted-power-mean mixture model: application to multicomponent liquid viscosity WW Focke, C Sandrock, S Kok Industrial & engineering chemistry research 46 (13), 4660-4666

11 2007


Estimating the gas permeability of commercial volatile corrosion inhibitors at elevated temperatures with thermo-gravimetry N Pieterse, WW Focke, E Vuorinen, I Rácz Corrosion science 48 (8), 1986-1995

11 2006

Carbon technology

Metal catalysed intumescence: characterisation of the thermal decomposition of calcium gluconate monohydrate F Labuschagne, WW Focke Journal of materials science 38 (6), 1249-1254

11 2003

Carbon technology

Characterization of commercial expandable graphite fire retardants WW Focke, H Badenhorst, W Mhike, HJ Kruger, D Lombaard Thermochimica Acta 584, 8-16

10 2014

Carbon technology

Surface resistivity and mechanical properties of rotationally molded polyethylene/graphite composites W Mhike, WW Focke Journal of Vinyl and Additive Technology 19 (4), 258-270

10 2013


Crystallization of a polyamide 11/organo-modified montmorillonite nanocomposite at rapid cooling I Kolesov, R Androsch, D Mileva, W Lebek, A Benhamida, M Kaci, ... Colloid and Polymer Science 291 (11), 2541-2549

10 2013

Malaria vector control

Sustainable malaria control: transdisciplinary approaches for translational applications LM Birkholtz, R Bornman, W Focke, C Mutero, C De Jager Malaria journal 11 (1), 1

10 2012

Malaria vector control

Degradation of insecticides used for indoor spraying in malaria control and possible solutions MM Sibanda, WW Focke, FJWJ Labuschagne, L Moyo, NS Nhlapo, ... Malaria journal 10 (1), 1

10 2011


Fast underwater bonding to polycarbonate using photoinitiated cyanoacrylate WE Cloete, WW Focke International Journal of Adhesion and Adhesives 30 (4), 208-213

9 2010


TGA–FTIR study of the vapors released by triethylamine–acetic acid mixtures NS Nhlapo, WW Focke, E Vuorinen Thermochimica acta 546, 113-119

8 2012


Stearate intercalated layered double hydroxides: effect on the physical properties of dextrin-alginate films EP Landman, WW Focke Journal of materials science 41 (8), 2271-2279

8 2006

https://scholar.google.co.za/scholar?oi=bibs&hl=en&cites=13890359238651512827https://scholar.google.co.za/scholar?oi=bibs&hl=en&cites=1740033019214801597https://scholar.google.co.za/scholar?oi=bibs&hl=en&cites=2835704537730769538https://scholar.google.co.za/scholar?oi=bibs&hl=en&cites=11123840048399194236https://scholar.google.co.za/scholar?oi=bibs&hl=en&cites=12499434834978483298https://scholar.google.co.za/scholar?oi=bibs&hl=en&cites=17459683782165098397https://scholar.google.co.za/scholar?oi=bibs&hl=en&cites=7495149259592425727https://scholar.google.co.za/scholar?oi=bibs&hl=en&cites=5507854496615714480https://scholar.google.co.za/scholar?oi=bibs&hl=en&cites=17904109846225666451https://scholar.google.co.za/scholar?oi=bibs&hl=en&cites=4389585340157400612https://scholar.google.co.za/scholar?oi=bibs&hl=en&cites=6199087504938680923https://scholar.google.co.za/scholar?oi=bibs&hl=en&cites=2709367295133482985

Carbon technology

Thermal analysis of commercial inorganic flame retardants WW Focke, CA Strydom, N Bartie South African Journal of Chemical Engineering 9, 41-51

8 1997


Rheological behavior and thermal properties of pitch/poly (vinyl chloride) blends SR Hlatshwayo, WW Focke, S Ramjee, B Rand, N Manyala Carbon 51, 64-71

7 2013

Pyrotechnics Suppressing H2 evolution by silicon powder dispersions SM Tichapondwa, WW Focke, O Del Fabbro, S Mkhize, E Muller Journal of Energetic Materials 29 (4), 326-343

7 2011


Poly (ethylene‐vinyl co‐vinyl acetate)/clay nanocomposites: Mechanical, morphology, and thermal behavior S Joseph, WW Focke Polymer Composites 32 (2), 252-258

7 2011


Thermal properties of lauric-and stearic acid intercalated layered double hydroxides WW Focke, NS Nhlapo, L Moyo, SMC Verryn Molecular Crystals and Liquid Crystals 521 (1), 168-178

7 2010


Effect of hydrated fillers and red phosphorus on the limiting oxygen index of poly (ethylene‐co‐vinyl actate)‐poly (vinyl butyral) and low density polyethylene‐poly (ethylene‐co‐vinyl alcohol) blends M Burns, U Wagenknecht, B Kretzschmar, WW Focke Journal of Vinyl and Additive Technology 14 (3), 113-119

7 2008


Heat stabilising flexible PVC with layered double hydroxide derivatives FJ Labuschagne, DM Molefe, WW Focke, I Van der Westhuizen, ... Polymer Degradation and Stability 113, 46-54

6 2015


Characterization of urea-modified Palabora vermiculite HF Muiambo, WW Focke, M Atanasova, A Benhamida Applied Clay Science 105, 14-20

6 2015

Carbon technology

Flame retarding effect of graphite in rotationally molded polyethylene/graphite composites W Mhike, IVW Ferreira, J Li, SI Stoliarov, WW Focke Journal of Applied Polymer Science 132 (7)

6 2015

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Contributions to a paper: • Conceptualised idea for research • Responsible for data analysis/design • Lead author writing up of article • Wrote first draft, editorial input • Postgraduate supervisor of the lead author • Co-developed and executed research • Project leader/budget owner

1. Macheca AD, Focke WW, Muiambo HF, Kaci M. Stiffening mechanisms in vermiculite–amorphous polyamide bio-nanocomposites. European Polymer Journal. 2016;74:51-63. doi:10.1016/j.eurpolymj.2015.11.013 http://dx.doi.org/10.1016/j.eurpolymj.2015.11.013

2. Maria T. Atanasova, Anastasia Vyalikh, Ulrich Scheler and Walter W. Focke. Characterization of rectorite from the Beatrix Gold Mine in South Africa. Accepted by Applied Clay Science Applied Clay Science Volume 126, June 2016, Pages 7–16 doi:10.1016/j.clay.2016.02.028 http://www.sciencedirect.com/science/article/pii/S0169131716300928

3. Walter W Focke, Isbe van der Westhuizen, Xander Oosthuysen. Biodiesel oxidative stability from Rancimat data. Thermochimica Acta 633 (2016) 116–121. http://dx.doi.org/10.1016/j.tca.2016.03.023

4. Katalee Jariyavidyanont, Walter Focke & René Androsch. Crystallization kinetics of polyamide 11 in the presence of sepiolite and montmorillonite nanofillers. Colloid Polym Sci (2016) 294:1143–1151. DOI 10.1007/s00396-016-3874-y

5. Shepherd M. Tichapondwa, Walter W. Focke, Olinto del Fabbro, John Gisby & Cheryl Kelly. A Comparative Study of Si-BaSO4 and Si-CaSO4 Pyrotechnic Time-Delay Compositions. Journal of Energetic Materials, Volume 34, Issue 3, 2016 pages 342-356. DOI:10.1080/07370652.2015.1077907 http://www.tandfonline.com/doi/abs/10.1080/07370652.2015.1077907?journalCode=uegm20

6. Shepherd M. Tichapondwa, Walter W. Focke, Olinto Del Fabbro. The effect of additives on the burning rate of the silicon-calcium sulfate pyrotechnic delay compositions. Propellants, Explosives, Pyrotechnics. 41, 732-739. DOI: 10.1002/prep.201500243

http://dx.doi.org/10.1016/j.eurpolymj.2015.11.013http://dx.doi.org/10.1016/j.eurpolymj.2015.11.013http://www.sciencedirect.com/science/journal/01691317http://www.sciencedirect.com/science/journal/01691317/126/supp/Chttp://dx.doi.org/10.1016/j.clay.2016.02.028http://www.sciencedirect.com/science/article/pii/S0169131716300928http://dx.doi.org/10.1016/j.tca.2016.03.023http://www.tandfonline.com/doi/abs/10.1080/07370652.2015.1077907?journalCode=uegm20

7. Y. C. Montgomery, W. W. Focke, M. Atanasova, O. Del Fabbro, C. Kelly, Mn + Sb2O3 thermite/intermetallic delay compositions. Propellants, Explosives, Pyrotechnics 2016, 41, 919 – 925.

8. Potgieter, G., Focke, W. W., Del Fabbro, O., Labuschagné, G. D. & Kelly, C. 2016b. Fluoroelastomer pyrotechnic time delay compositions. Journal of Thermal Analysis and Calorimetry, 126, 1363-1370.

2015

1. Characterization of urea-modified Palabora vermiculite 2015 2. Polyhedral oligomeric silsesquioxane/polyamide bio-nanocomposite membranes: structure-gas transport properties 2015 3. Heat stabilising flexible PVC with layered double hydroxide derivatives 2015 4. Low Shear Rheological Behaviour of Two-Phase Mesophase Pitch 2015 5. Trapping citronellal in a microporous polyethylene matrix 2015 6. Calcium Sulfate as a Possible Oxidant in “Green” Silicon-based Pyrotechnic Time Delay Compositions 2015 7. Advanced EVA nanocomposites: Developments and new opportunities 2015 8. Polyhedral oligomeric silsesquioxane/polyamide bio-nanocomposite membranes: structure-gas transport properties 2015 9. The effect of magnesium hydroxide, hydromagnesite and layered double hydroxide on the heat stability and fire performance of plasticized poly(vinyl chloride) 10. Acceptability and effectiveness of a monofilament, polyethylene insecticide-treated wall lining for malaria control after six months in dwellings in Vhembe District,

Limpopo Province, South Africa 2015

2014

1. Facile synthesis of copper antimonite 2014 2. Anomalous shear viscosity-temperature behaviour of jojoba oil LDH-stearate suspensions 2014 3. Flexible PVC flame retarded with expandable graphite 2014 4. Suppressing hydrogen evolution by aqueous silicon powder dispersions through the introduction of additional cathodic reaction 2014 5. Crystal structure and magnetic properties of CuSb2O4 2014 6. Surfactant-free dimer fatty acid polyamide/montmorillonite bio-nanocomposites 2014 7. Characterization of commercial expandable graphite fire retardants 2014 8. Graphite foam from pitch and expandable graphite 2014 9. Polyethylene flame retarded with expandable graphite and a novel intumescent additive 2014

10. EVA nanocomposites based on South African Koppies clay 2014 11. Study of Solvent Debinding Variables on Ti6Al4V Green Bodies 2014 12. Flame retarding effect of graphite in rotationally molded polyethylene/graphite composites 2014 13. Cone calorimeter study of polyethylene flame retarded with expandable graphite and intumescent fire retardant additives. 2014 14. Development of an insecticide impregnated polymer wall lining for malaria vector control 2014

2013

1. Rheological behavior and thermal properties of pitch/poly(vinyl chloride) blends 2013 2. Development of thermoresponsive poly(propylene-g-N-isopropylacrylamide) non-woven 3D scaffold for smart cell culture using oxyfluorination-assisted graft

polymerisation 2013 3. Properties of layered double hydroxide micro- and nanocomposites 2013 4. Properties of graphite composites based on natural and synthetic graphite powders and a phenolic novolac binder 2013 5. Crystallization of nanocomposites of an isotactic random butene-1/ethylene copolymer and layered double hydroxide 2013 6. A generalized solid state kinetic expression for reaction interface-controlled reactivity 2013 7. Thermal analysis and FTIR studies of volatile corrosion inhibitor model systems 2013 8. Crystallization of a polyamide 11/organo-modified montmorillonite nanocomposite at rapid cooling 2013 9. Suppressing hydrogen evolution by aqueous silicon powder dispersions by controlled silicon surface oxidation 2013 10. Comparative analysis of graphite oxidation behaviour based on microstructure 2013 11. Surface resistivity and mechanical properties of rotationally molded polyethylene/graphite composites 2013

2012

1. Analysis of the q-fractions weighted power mean mixture rules 2012 2. Geometric effects control isothermal oxidation of graphite flakes 2012 3. Mixing rules based on power means and generalized q-fractions 2012 4. The effect of synthetic antioxidants on the oxidative stability of biodiesel 2012 5. Layered double hydroxides as nano additives in poly(ε-caprolactone) 2012 6. Thermally conductive phase-change materials for energy storage based on low-density polyethylene, soft Fischer-Tropsch wax and graphite 2012 7. Layered double hydroxide intercalated with sodium dodecyl sulfate 2012 8. TGA-FTIR study of the vapors released by triethylamine-acetic acid mixtures 2012 9. Characterization of medium-temperature Sasol-Lurgi gasifier coal tar pitch 2012 10. Sustainable malaria control: transdisciplinary approaches for translational applications 2012 11. Ion Exchanged Vermiculites with Lower Expansion Onset Temperatures 2012 12. Co-Intercalation of Insecticides with Hexadecyltrimethylammonium Chloride in Mozambican Bentonite 2012

13. Intercalating Cationic Surfactants in Koppies Bentonite 2012

2011

1. The effect of Si-Bi2O3 on the ignition of the Al-CuO thermite 2011 2. Polypropylene-based long-life insecticide-treated mosquito netting 2011 3. Assessment of the effect of nanomaterials on sediment-dwelling invertebrate Chironomus tentans larvae 2011 4. Degradation of insecticides used for indoor spraying in malaria control and possible solutions 2011 5. Suppressing H 2 evolution by silicon powder dispersions 2011 6. Poly (Ethylene-vinyl co-vinyl acetate) /Clay nanocomposites: mechanical, morphology and thermal behaviour 2011 7. Stabilization of LDPE films containing metal stearates as photodegradants 2011 8. Titania recovery from low-grade titanoferrous minerals 2011

2010

1. Oxidation induction time (OIT) and oxidation onset temperature (OOT) of polyethylene in air. Testing Gimzewski's postulate 2010 2. Compatibilizing action of a poly(styrene-butadiene) triblock copolymer in ABS/PET-G blends 2010 3. Thermal properties of sodium-exchanged Palabora vermiculite 2010 4. Modelling of natural graphite oxidation using thermal analysis techniques 2010 5. Alkyl ammonium intercalation of Mozambican bentonite 2010 6. Manganese as Fuel in Slow-Burning Pyrotechnic Time Delay Compositions 2010 7. Optimal designs for estimating the parameters in weighted power-mean-mixture models 2010 8. Photoinitiated Cyanoacrylates for Fast Underwater Bonding 2010 9. Thermal Properties of Lauric- and Stearic Acid Intercalated Layered Double Hydroxides 2010

2009

1. Thermo-Mechanical Properties of urea-based pattern molding compounds for investment casting 2009 2. Morphology and properties of nanostructured materials based on polypropylene/poly(butylene succinate) blend and organoclay 2009 3. Mn2Al-LDH- and Co2Al-LDH-stearate as photo degradants for LDPE film 2009 4. Latex derived blends of poly(vinyl acetate) and natural rubber: thermal and mechanical properties 2009 5. Weighted-Power-Mean mixture model for the Gibbs energy of Fluid mixtures 2009 6. Mechanical properties of ternary blends of ABS + HIPS + PETG 2009 7. The influence of stearic acid coating on the properties of magnesium hydroxide, hydromagnesite and hydrotalcite powders 2009 8. Alkali-assisted coal extraction with polar aprotic solvents 2009

ACKERMANN, M. H., FOCKE, W. W. & COETZER, R. L. J. 2012. Analysis of the q-fractions weighted power mean mixture rules. Journal of Chemical Engineering of Japan, 45, 9-20.

AKHTAR, M. U. & FOCKE, W. W. 2015. Trapping citronellal in a microporous polyethylene matrix. Thermochimica Acta, 613, 61-65. ATANASOVA, M. T., STRYDOM, A. M., SCHUTTE, C. J. H., PRINSLOO, L. C. & FOCKE, W. W. 2014. Crystal structure and magnetic properties of CuSb2O4. Journal

of Materials Science, 49, 3497-3510. ATANASOVA, M. T., VYALIKH, A., SCHELER, U. & FOCKE, W. W. 2016. Characterization of rectorite from the Beatrix Gold Mine in South Africa. Applied Clay

Science, 126, 7-16. BADENHORST, H. & FOCKE, W. 2013. Comparative analysis of graphite oxidation behaviour based on microstructure. Journal of Nuclear Materials, 442, 75-

82. BADENHORST, H. & FOCKE, W. W. 2012. Geometric effects control isothermal oxidation of graphite flakes. Journal of Thermal Analysis and Calorimetry, 108,

1141-1150. BADENHORST, H., RAND, B. & FOCKE, W. 2013. A generalized solid state kinetic expression for reaction interface-controlled reactivity. Thermochimica Acta,

562, 1-10. BADENHORST, H., RAND, B. & FOCKE, W. W. 2010. Modelling of natural graphite oxidation using thermal analysis techniques. Journal of Thermal Analysis and

Calorimetry, 99, 211-228. COETZER, R. L. J. & FOCKE, W. W. 2010. Optimal designs for estimating the parameters in weighted power-mean-mixture models. Journal of Chemometrics,

24, 34-42. FOCKE, W. W. 2009. Weighted-power-mean mixture model for the Gibbs energy of fluid mixtures. Industrial and Engineering Chemistry Research, 48, 5537-

5541. FOCKE, W. W., ACKERMANN, M. H. & COETZER, R. L. J. 2012a. Mixing rules based on power means and generalized q-fractions. Journal of Chemical Engineering

of Japan, 45, 1-8. FOCKE, W. W., BADENHORST, H., MHIKE, W., KRUGER, H. J. & LOMBAARD, D. 2014a. Characterization of commercial expandable graphite fire retardants.

Thermochimica Acta, 584, 8-16. FOCKE, W. W., BADENHORST, H., RAMJEE, S., KRUGER, H. J., VAN SCHALKWYK, R. & RAND, B. 2014b. Graphite foam from pitch and expandable graphite.

Carbon, 73, 41-50. FOCKE, W. W., KRUGER, H. J., MHIKE, W., TAUTE, A., ROBERSON, A. & OFOSU, O. 2014c. Polyethylene flame retarded with expandable graphite and a novel

intumescent additive. Journal of Applied Polymer Science, n/a-n/a.

FOCKE, W. W., MACHECA, A. D., BENHAMIDA, A. & KACI, M. Stiffening mechanisms in amorphous polyamide bio-nanocomposites. AIP Conference Proceedings, 2016a.

FOCKE, W. W., MASHELE, R. P. & NHLAPO, N. S. 2011. Stabilization of low-density polyethylene films containing metal stearates as photodegradants. Journal of Vinyl and Additive Technology, 17, 21-27.

FOCKE, W. W., MKHIZE, S. S., STOREY, R., FABBRO, O. D. & MULLER, E. 2014d. Facile synthesis of copper antimonite. Chemical Engineering Communications, 201, 153-159.

FOCKE, W. W., MOLEFE, D., LABUSCHAGNE, F. J. W. & RAMJEE, S. 2009. The influence of stearic acid coating on the properties of magnesium hydroxide, hydromagnesite, and hydrotalcite powders. Journal of Materials Science, 44, 6100-6109.

FOCKE, W. W., MUIAMBO, H., MHIKE, W., KRUGER, H. J. & OFOSU, O. 2014e. Flexible PVC flame retarded with expandable graphite. Polymer Degradation and Stability, 100, 63-69.

FOCKE, W. W., NHLAPO, N. S., MOYO, L. & VERRYN, S. M. C. 2010. Thermal properties of lauric- and stearic acid intercalated layered double hydroxides. Molecular Crystals and Liquid Crystals, 521, 168-178.

FOCKE, W. W., NHLAPO, N. S. & VUORINEN, E. 2013. Thermal analysis and FTIR studies of volatile corrosion inhibitor model systems. Corrosion Science. FOCKE, W. W. & VAN DER WESTHUIZEN, I. 2010. Oxidation induction time and oxidation onset temperature of polyethylene in air: Testing Gimzewski's

postulate. Journal of Thermal Analysis and Calorimetry, 99, 285-293. FOCKE, W. W., VAN DER WESTHUIZEN, I., MUSEE, N. & LOOTS, M. T. Submitted for review in 2016. Kinetic interpretation of log-logistic dose-time response

curves. FOCKE, W. W. & VAN PAREEN, W. 2011. Polypropylene-based long-life insecticide-treated mosquito netting. Journal of Polymer Engineering, 31, 521-529. FOCKE, W. W., WESTHUIZEN, I. V. D., GROBLER, A. B. L., NSHOANE, K. T., REDDY, J. K. & LUYT, A. S. 2012b. The effect of synthetic antioxidants on the oxidative

stability of biodiesel. Fuel, 94, 227-233. FOCKE, W. W., WESTHUIZEN, I. V. D. & OOSTHUYSEN, X. 2016b. Biodiesel oxidative stability from Rancimat data. Thermochimica Acta, 633, 116-121. FOCKE, W. W. M., W.; KRUGER, H. J.; VAN SCHALKWYK, R.; LOMBAARD, D.; BADENHORST, H. 2014. Thermal Analysis of Commercial Expandable Graphite

Flame Retardants. HLATSHWAYO, S. R., FOCKE, W. W., RAMJEE, S., RAND, B. & MANYALA, N. 2013. Rheological behavior and thermal properties of pitch/poly(vinyl chloride)

blends. Carbon, 51, 64-71. ILUNGA, K., DEL FABBRO, O., YAPI, L. & FOCKE, W. W. 2011. The effect of Si-Bi2O3 on the ignition of the Al-CuO thermite. Powder Technology, 205, 97-102. IZADI, H., FOCKE, W. W., MAHARAJ, R. & PRETORIUS, J. A. Submitted for review in 2016. A promising azeotrope-like mosquito repellent blend. JARIYAVIDYANONT, K., FOCKE, W. & ANDROSCH, R. 2016. Crystallization kinetics of polyamide 11 in the presence of sepiolite and montmorillonite nanofillers.

Colloid and Polymer Science, 294, 1143-1151. JOSEPH, S. & FOCKE, W. W. 2011. Poly(ethylene-vinyl co-vinyl acetate)/clay nanocomposites: Mechanical, morphology, and thermal behavior. Polymer

Composites, 32, 252-258. KOLESOV, I., ANDROSCH, R., MILEVA, D., LEBEK, W., BENHAMIDA, A., KACI, M. & FOCKE, W. 2013. Crystallization of a polyamide 11/organo-modified

montmorillonite nanocomposite at rapid cooling. Colloid and Polymer Science, 1-9.

KRUGER, H. J., FOCKE, W. W., MHIKE, W., TAUTE, A. & ROBERSON, A. 2016. Thermal properties of polyethylene flame retarded with expandable graphite and intumescent fire retardant additives. Fire and Materials.

KRUGER, H. J. F., W.W.; MHIKE, W.; TAUTE, A.; OFOSU, O. 2014. Cone calorimeter study of polyethylene flame retarded with expandable graphite and intumescent fire retardant additives.

KRUGER, T., SIBANDA, M. M., FOCKE, W. W., BORNMAN, M. S. & DE JAGER, C. 2015. Acceptability and effectiveness of a monofilament, polyethylene insecticide-treated wall lining for malaria control after six months in dwellings in Vhembe District, Limpopo Province, South Africa. Malaria Journal, 14.

LABUSCHAGNE, F. J. W. J., MOLEFE, D. M., FOCKE, W. W., VAN DER WESTHUIZEN, I., WRIGHT, H. C. & ROYEPPEN, M. D. 2015. Heat stabilising flexible PVC with layered double hydroxide derivatives. Polymer Degradation and Stability, 113, 46-54.

MACHECA, A., GNANASEKARAN, D. & FOCKE, W. W. 2013. Surfactant-free dimer fatty acid polyamide/montmorillonite bio-nanocomposites. Colloid and Polymer Science, 1-8.

MACHECA, A. D., FOCKE, W. W., MUIAMBO, H. F. & KACI, M. 2016. Stiffening mechanisms in vermiculite-amorphous polyamide bio-nanocomposites. European Polymer Journal, 74, 51-63.

MAGAGULA, B., NHLAPO, N. & FOCKE, W. W. 2009. Mn2Al-LDH- and Co2Al-LDH-stearate as photodegradants for LDPE film. Polymer Degradation and Stability, 94, 947-954.

MAGAMPA, P. P., MANYALA, N. & FOCKE, W. W. 2013. Properties of graphite composites based on natural and synthetic graphite powders and a phenolic novolac binder. Journal of Nuclear Materials, 436, 76-83.

MAKGATO, M. H., MOITSHEKI, L. J., SHOKO, L., KGOBANE, B. L., MORGAN, D. L. & FOCKE, W. W. 2009. Alkali-assisted coal extraction with polar aprotic solvents. Fuel Processing Technology, 90, 591-598.

MANHIQUE, A., FOCKE, W. W., LEUTERITZ, A. & MADIVATE, C. 2012. Layered double hydroxides as nano additives in poly(ε-caprolactone). Molecular Crystals and Liquid Crystals, 556, 114-123.

MASSINGA, P. H. & FOCKE, W. W. 2012. Intercalating Cationic Surfactants in Koppies Bentonite. Molecular Crystals and Liquid Crystals, 555, 85-93. MASSINGA, P. H., FOCKE, W. W., DE VAAL, P. L. & ATANASOVA, M. 2010. Alkyl ammonium intercalation of Mozambican bentonite. Applied Clay Science, 49,

142-148. MASSINGA, P. H., FOCKE, W. W., DEL FABBRO, O. & RADUSCH, H.-J. 2014. EVA nanocomposites based on South African Koppies clay. Journal of Vinyl and

Additive Technology, 20, 143-151. MERCKEL, R. D., FOCKE, W. W., SIBANDA, M. M., MASSINGA, P. & CROWTHER, N. A. S. 2012. Co-Intercalation of Insecticides with

Hexadecyltrimethylammonium Chloride in Mozambican Bentonite. Molecular Crystals and Liquid Crystals, 555, 76-84. MHIKE, W., FERREIRA, I. V. W., LI, J., STOLIAROV, S. I. & FOCKE, W. W. 2015. Flame retarding effect of graphite in rotationally molded polyethylene/graphite

composites. Journal of Applied Polymer Science, 132. MHIKE, W., FOCKE, W. W., MOFOKENG, J. P. & LUYT, A. S. 2012. Thermally conductive phase-change materials for energy storage based on low-density

polyethylene, soft Fischer-Tropsch wax and graphite. Thermochimica Acta, 527, 75-82. MHIKE, W., W FOCKE, W. W., ASANTE, J. K. O. & MANYALA, N. I. 2016. Rotomoulded antistatic and flame retarded graphite nanocomposites.

MHIKE, W. F., W.W. 2013. Surface resistivity and mechanical properties of rotationally molded polyethylene/graphite composites. Journal of Vinyl and Additive Technology.

MOLEFE, D. M., LABUSCHAGNE, J., FOCKE, W. W., WESTHUIZEN, I. V. D. & OFOSU, O. 2015. The effect of magnesium hydroxide, hydromagnesite and layered double hydroxide on the heat stability and fire performance of plasticized poly(vinyl chloride). Journal of Fire Sciences, 33, 493-510.

MOLLOVA, A., KOLESOV, I., ANDROSCH, R., LABUSCHAGNE, J., FOCKE, W. & FUNARI, S. S. 2013. Crystallization of nanocomposites of an isotactic random butene-1/ethylene copolymer and layered double hydroxide. Polymer Bulletin, 1-14.

MONTGOMERY, Y. C., FOCKE, W. W., ATANASOVA, M., DEL FABBRO, O. & KELLY, C. 2016. Mn+Sb2O3 Thermite/Intermetallic Delay Compositions. Propellants, Explosives, Pyrotechnics, n/a-n/a.

MONTGOMERY, Y. C., FOCKE, W. W. & KELLY, C. 2017. Measurement and modelling of pyrotechnic time delay burn rates: Method and model development. Submitted for consideration as a publication in Propellants, Explosives, Pyrotecnics.

MOYO, L., FOCKE, W. W., HEIDENREICH, D., LABUSCHAGNE, F. J. W. J. & RADUSCH, H. J. 2013. Properties of layered double hydroxide micro- and nanocomposites. Materials Research Bulletin, 48, 1218-1227.

MOYO, L., FOCKE, W. W., LABUSCHAGNE, F. J. W. J. & VERRYN, S. 2012. Layered double hydroxide intercalated with sodium dodecyl sulfate. Molecular Crystals and Liquid Crystals, 555, 51-64.

MUIAMBO, H. F., FOCKE, W. W., ATANASOVA, M. & BENHAMIDA, A. 2015. Characterization of urea-modified Palabora vermiculite. Applied Clay Science, 105–106, 14-20.

MUIAMBO, H. F., FOCKE, W. W., ATANASOVA, M., DER WESTHUIZEN, I. V. & TIEDT, L. R. 2010. Thermal properties of sodium-exchanged palabora vermiculite. Applied Clay Science, 50, 51-57.

NHLAPO, N. S., FOCKE, W. W. & VUORINEN, E. 2012. TGA-FTIR study of the vapors released by triethylamine-acetic acid mixtures. Thermochimica Acta, 546, 113-119.

PAPOLE, G., FOCKE, W. W. & MANYALA, N. 2012. Characterization of medium-temperature Sasol-Lurgi gasifier coal tar pitch. Fuel, 98, 243-248. PIETERSE, N. & FOCKE, W. W. 2003. Diffusion-controlled evaporation through a stagnant gas: Estimating low vapour pressures from thermogravimetric data.

Thermochimica Acta, 406, 191-198. PIETERSE, N., FOCKE, W. W., VUORINEN, E. & RÁCZ, I. 2006. Estimating the gas permeability of commercial volatile corrosion inhibitors at elevated

temperatures with thermo-gravimetry. Corrosion Science, 48, 1986-1995. RAMJEE, S., RAND, B. & FOCKE, W. W. 2015. Low shear rheological behaviour of two-phase mesophase pitch. Carbon, 82, 368-380. SIBANDA, M., LEUTERITZ, A., BRÜNIG, H. & FOCKE, W. 2016. The development of slow-release filaments to control malaria. Innovate. Pretoria, South Africa:

Graduate School of Technology Management, University of Pretoria. SIBANDA, M. M., FOCKE, W. W., LABUSCHAGNE, F. J. W. J., MOYO, L., NHLAPO, N. S., MAITY, A., MUIAMBO, H., MASSINGA, P., CROWTHER, N. A. S., COETZEE,

M. & BRINDLEY, G. W. A. 2011. Degradation of insecticides used for indoor spraying in malaria control and possible solutions. Malaria Journal, 10. SWANEPOEL, D., DEL FABBRO, O., FOCKE, W. W. & CONRADIE, C. 2010. Manganese as fuel in slow-burning pyrotechnic time delay compositions. Propellants,

Explosives, Pyrotechnics, 35, 105-113.

TICHAPONDWA, S. M., FOCKE, W. W., DEL FABBRO, O., GISBY, J. & KELLY, C. 2016a. A Comparative Study of Si-BaSO4 and Si-CaSO4 Pyrotechnic Time-Delay Compositions. Journal of Energetic Materials, 34, 342-356.

TICHAPONDWA, S. M., FOCKE, W. W., DEL FABBRO, O., MKHIZE, S. & MULLER, E. 2011. Suppressing H 2 evolution by silicon powder dispersions. Journal of Energetic Materials, 29, 326-343.

TICHAPONDWA, S. M., FOCKE, W. W., DEL FABBRO, O. & MULLER, E. 2013. Suppressing hydrogen evolution by aqueous silicon powder dispersions by controlled silicon surface oxidation. Propellants, Explosives, Pyrotechnics, 38, 48-55.

TICHAPONDWA, S. M., FOCKE, W. W., DEL FABBRO, O. & KELLY, C. 2015. Calcium Sulfate as a Possible Oxidant in “Green” Silicon-based Pyrotechnic Time Delay Compositions. Propellants, Explosives, Pyrotechnics, 40, 518-525.

TICHAPONDWA, S. M., FOCKE, W. W., DEL FABBRO, O. & LABUSCHAGNE, G. 2016b. The Effect of Additives on the Burning Rate of Silicon-Calcium Sulfate Pyrotechnic Delay Compositions. Propellants, Explosives, Pyrotechnics, n/a-n/a.

TICHAPONDWA, S. M., FOCKE, W. W., FABBRO, O. D., SANDENBERGH, R. W. & MULLER, E. 2014. SUPPRESSING HYDROGEN EVOLUTION BY AQUEOUS SILICON POWDER DISPERSIONS THROUGH THE INTRODUCTION OF AN ADDITIONAL CATHODIC REACTION. Chemical Engineering Communications, 201, 501-515.

Documents

Institute of Applied Materials: Focke Research Groups...Alkali-assisted coal extraction with polar aproticsolvents. Fuel Processing Technology 90 (2009) 591-598. 2. G Papole, WW Focke,