Materials and Design 54 (2014) 644–651

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Materials and Design

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Technical Report

Development of coir pith/nylon fabric/epoxy hybrid composites:Mechanical and ageing studies

0261-3069/$ - see front matter � 2013 Elsevier Ltd. All rights reserved.http://dx.doi.org/10.1016/j.matdes.2013.08.080

⇑ Corresponding author. Tel.: +91 416 2202696; fax: +91 416 2243092.E-mail address: k.priya@vit.ac.in (K. Priya Dasan).

R. Narendar a, K. Priya Dasan a,⇑, Muraleedharan Nair b

a Material Chemistry Division, SAS, VIT University, Tamil Nadu 632014, Indiab Common Facility Service Centre, Malappuram, Kerala 676124, India

a r t i c l e i n f o a b s t r a c t

Article history:Received 8 July 2013Accepted 22 August 2013Available online 30 August 2013

The coir pith epoxy composites were hybridized with nylon fabric/epoxy resin by hand lay up techniquefollowed by compression moulding. A set of composites of same composition having chemically treatedcoir pith was also prepared. Mechanical properties of composites such as tensile strength, flexuralstrength, impact strength and hardness were evaluated. Though coir pith acts as a good reinforcementin epoxy resin, the incorporation of nylon fabric and the chemical treatment of coir pith were found toenhance the properties of the composites further. Chemical resistance and flame resistance of compositesystems were also found to be improved with hybrid composites. Since water uptake and retentionsproperty of coir pith is a major drawback when it comes to its application in composites, the ageing ofcomposite panels in moist environment was investigated. The results suggested that the presence ofnylon fabric and chemically treated pith can contribute to longer durability of the panels in moistconditions.

� 2013 Elsevier Ltd. All rights reserved.

1. Introduction

The use of lignocellulosic materials as reinforcing fillers in poly-meric products has increased recently. These natural fillers are eco-friendly, have low density, low-cost, non-abrasive in nature andare biodegradable. Sisal [1], banana fiber [2], cotton [3], flax [4],hemp [5], jute [6] and ramie [7] have been well recognized as rein-forcements for natural filler composites. Most of these fillers arecategorized under agro wastes and their disposal is a huge respon-sibility for the government. They pose severe environmental pollu-tion problems and occupy fertile useful land. Therefore developingengineering end use such as building materials and structural partsout of these materials has become a requirement. Application ofagro-wastes as particle boards, thermal insulators, building mate-rial composites/bricks, cementitious/binder and aggregates [8–12] have been well studied.

Coir pith is one of the major agro wastes found in the southerncoastal regions of India. Coir pith is generated in the separationprocess of the fiber from the coconut husk and is generally dumpedas an agro waste. Because of its low degradation in the environ-ment, the hillocks of coir pith collected or dumped pause serioushealth hazards and loss of fertile lands. Because of the high lignincontent left it takes decades to decompose; it only begins to breakdown when it is 10 years old. The tannins and phenols from coirpith leach out into the soil and water bodies causing pollution. It

is estimated that at present there is an accumulated stock of10 � 106 metric tons of coir pith in the southern states of Indiaand about 7.5 � 105 tons of coir pith is produced annually in India[13]. Developing alternate ways to dispose of coir pith is of criticalimportance. Cost effective technologies that address the develop-ment of value added products from coir pith therefore become rel-evant for countries producing coir pith. The application of coir pithas reinforcement in polymer has not been reported so far.

One factor that has prevented a more extended utilization of theagro-wastes in composite industry is the lack of compatibility ofthese fillers in most polymeric matrices. The hydrophilic natureof natural fillers adversely affects adhesion to hydrophobic matrixand as a result, causes poor mechanical properties. One of the mostcommonly adopted methods to overcome this issue is the chemicaltreatment of natural fillers. The effect of chemical treatments onthe mechanical and other properties of composites are well docu-mented. Gassan and Bledzki [14] studied the mechanical proper-ties of jute/epoxy composites. Composite strength and stiffnessincreased as a consequence of the improved mechanical propertiesof the fibers by alkali treatment. Kenaf/epoxy composites were pre-pared after subjecting the fiber to mercerization. The failure mech-anism and damage features of the materials revealed thatreinforcement of epoxy with treated kenaf fibers increased theflexural strength of the composite compare to untreated fibersYousif et al. [15]. Bachtiar et al. [16] reported the mechanical prop-erties of sugar palm fiber treated with sodium hydroxide. Tensilemodulus of composites was much higher than untreated fibercomposite specimens, which proved the effectiveness of the

R. Narendar et al. / Materials and Design 54 (2014) 644–651 645

treatment. Min Zhi Rong et al. [17] studied the sisal fiber reinforcedepoxy composites. Results showed that alkali treatment removedcementing materials which were partially replaced by epoxy resin.This greatly improved fiber bundle/matrix bonding and also en-hanced mechanical strength of composite.

Hybrid composites are made by the incorporation of several dif-ferent types of reinforcements into a single matrix. They imply astep beyond in the search for novel materials with improvedmechanical properties and/or reduced cost. Hybrid polymer com-posites have been studied many researchers in the past [18–22].The use of synthetic reinforcements in combination with naturalfillers has been shown to exhibit excellent performance and atthe same time reduce the environmental impact. The hybrid effectof glass fiber and oil palm empty fruit bunch (OPEFB) fiber on themechanical properties of phenol–formaldehyde composites wasstudied by Sreekala et al. [23]. The introduction of small amountof glass fiber improved the impact strength of the composites.Meanwhile density of the hybrid composite decreased as the vol-ume fraction of the OPEFB fiber increased. Mechanical propertiesof jute/glass fiber reinforced epoxy composites were studied byKoradiya et al. [24]. Experimental results showed that hybrid com-posites have good mechanical properties than those of jute andglass composites. Jarukumjorn and Suppakarn [25] investigatedthe effect of glass fiber hybridization on the physico-mechanicalproperties of sisal–polypropylene composites. Incorporation ofglass fiber into sisal/polypropylene composites enhanced tensile,flexural and impact strength.

In the present work coir pith/epoxy composites were hybrid-ized with nylon fabric impregnated with epoxy resin. The compos-ites were prepared by hand lay up technique and than compressionmoulded. A set of composites with same composition havingchemically treated coir pith was also fabricated. Mechanical prop-erties, chemical resistance and flame resistance of composites wereinvestigated in detail. Research investigations showed that theexposure of natural filler composites in a wet environment leadsto a decrease of the mechanical properties when water spreadsin the material [26–30]. Since coir pith has a higher tendency to ab-sorb and retain water, it becomes essential to know how the com-posites made of coir pith behave in a wet environment. Hence thecomposite panels were subjected to wet environment and theirmechanical properties were evaluated.

2. Materials and methods

2.1. Materials

Coir pith was collected from a local coir processing unit(Gudiyathum, Tamilnadu, India). Sodium hydroxide was purchasedfrom Sigma–Aldrich, epoxy resin (LY556) and hardener (HY951)were purchased from Huntsman. Maaxil 402 mould release spraywas purchased from Maax lubrication.

2.2. Methods

2.2.1. Chemical treatmentCoir pith was soaked in 5% concentration of NaOH solution for

1 h at room temperature followed by washing with distilled water.Afterwards, the samples were oven dried at 70 �C for 2 h.

2.2.2. Composites preparationA square steel plate mould with dimension of 450 � 450 mm

assembled with top plate and base plate was used for the fabrica-tion of composites. To help the complete removal of compositesfrom the mould and to avoid sticking, a polyethylene sheetssprayed with mould release agent is layered on the top and base

plate. Nylon fabric with a uniform coating of epoxy and hardenerwas spread on the polyethylene sheet. The pith/resin mixture(mixed in an internal mixer) is spread on this followed by anotherlayer of resin coated nylon fabric. The samples were compressionmolded and cured over-night as shown (Fig. 1a and b). The resinhardener ratio is maintained at 10:1 in all formulations. The com-posites thus fabricated are denoted as given in Table 1.

3. Characterization

3.1. Fourier transform infrared (FTIR) spectroscopy

FT-IR spectroscopy was used to investigate the surface modifi-cation in treated and untreated coir pith. FT-IR analysis was carriedout in the range of 4000–400 cm�1 with a resolution of 2 cm�1

using a JASCO 400 Infrared spectrometer.

3.2. Morphology analysis

Scanning electron microscope (SEM) of Carl Ziess, EVO makewas used to analyze the morphology of coir pith and impact failuresurface of epoxy composites. Optical microscopic image of treatedand untreated coir pith were obtained using Brucker Carl Zeissoptical microscopy.

3.3. Mechanical properties

Tensile test was carried out according to ASTM: D 638-10 usinga universal testing machine of AG-IS Shimadzu, TMI make. Flexuraltests were performed according to ASTM: D 790-10 using InstronUTM, USA. Impact Izod test was done according to ASTM: D 256-10 using Tinius Olsen Model impact analyzer. Hardness was mea-sured by using Shore A hardness tester (Durometer-MitutoyoShore A meter).

3.4. Chemical resistance test

The chemical resistance properties of the epoxy resin/coir pith/nylon composites in CCl4, water, NaOH and HNO3 were studiedaccording to ASTM: D543-06. In each case, five pre-weighed sam-ples were dipped in the respective chemical reagents for 24 h. Theywere then removed and immediately washed in distilled water anddried by pressing them on both sides with a tissue paper at roomtemperature. The samples were then weighed and the percentageweight loss/gain was determined using the following equation.

Weight loss=gainð%Þ ¼ Final weight� Original weightOrginal weight

ð1Þ

3.5. Ageing studies

The ageing of composites on exposure to water was evaluatedby keeping the samples immersed in water. Five specimens of eachsample were kept immersed in distilled water at 30 �C for 31 days.The samples were taken out, dried at room temperature and theimpact strength was measured as mentioned above.

3.6. Flammability test

Flammability of polymer composites were evaluated as men-tioned in a previous report [31]. The tests closely simulate the Fed-eral Aviation Regulation, FAR 25.853 60 s vertical burn testspecification [46]. 290 mm � 70 mm sized samples were sus-pended vertically using a clamp on a lab stand. An LPG Bunsenflame was applied to the leading edge of the bottom surface of

Fig. 1. (a) Schematic representation of composite fabrication (b) composites panel.

Table 1Material code and its abbreviation.

Materialscode

Materials abbreviations

BLANK Epoxy resinEN2L Epoxy resin/nylon two layerEN3L Epoxy resin/nylon three layerERCP Epoxy resin/raw coir pithENA Epoxy resin/sodium hydroxide treated coir pithERCPN2L Epoxy resin/raw coir pith/nylon two layerENAN2L Epoxy resin/sodium hydroxide treated coir pith/nylon two

layersERCPN3L Epoxy resin/raw coir pith/nylon three layersENAN3L Epoxy resin/sodium hydroxide treated coir pith/nylon three

layers

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composite. The time required to catch fire is taken as ignition time.The flame time from the first mark (25 mm from the ignition end)until the second mark (100 mm from the ignition end) was mea-sured to determine the linear burning rate (V) of the sample. Thelinear burning rate (V), was calculated in millimeters per secondusing the equation

V ¼ 60L=t ð2Þ

L is the burned length in millimeters and t is the time inseconds.

4. Results and discussion

4.1. Tensile strength

The tensile strength of pure epoxy and different composite sam-ples are given in Table 2. The composite samples exhibit better ten-sile strength than the pure epoxy resin. The incorporation of rawcoir pith increased the tensile strength of epoxy resin by 19.34%.Meanwhile two and three layered nylon/epoxy composites showed25.74% and 30.49% higher tensile strength than the raw coir pith/epoxy composites. This indicates nylon fabric as better reinforce-ment for epoxy resin. Nylon fabric forms chemical bonding withepoxy resin and provides superior mechanical properties

(Scheme 1). The hybrid composites showed higher tensile valuesthan the individual composites samples with the two layered hy-brid composites showing almost similar tensile strength as thatof three layered nylon/epoxy composites. The presence of nylonfabric enhances the tensile properties in hybrid composites also.Three layered composites samples showed 33.00% higher tensilestrength than two layered composites samples. Henceforth it canbe concluded that the hybrid composites system with coir pith/ny-lon fabric/epoxy composites exhibits maximum tensile strengthand the property improves with number of nylon fabrics. In thepresent case nylon fabric act as skin and coir pith as the core mate-rial. The tensile strength will be higher, when the high strengthmaterial is used as the skin, which is the main load bearing compo-nent in the tensile measurements [32].

4.1.1. Effect of chemical treatmentThe tensile strength of composite samples with treated and raw

coir pith is also given in Table 2. Pure wettability of natural fillerdue to its hydrophilic nature is one of the major reasons for themechanical failure of natural filler reinforced composites. This re-sults in increased void content and structural flaws resulting inlow stress transfer between the polymer and filler. To prevent this,the filler surface has to be modified in order to encourage adhesion.Chemical treatment results in surface modification and gives riseto more groups on the filler surface and thus facilitates efficientcoupling with the matrix [16]. Many authors have indicated an in-crease in mechanical properties with chemical treatment [33,34].In a recent work on coir fiber reinforced polypropylene, the authorsobserved an increase in mechanical properties and fiber wettabilitywith chemical treatment [35]. For the present experiment, com-posite samples with chemically treated coir pith showed bettertensile strength values compared to the samples with untreatedcoir pith. Compared to ERCP composite, tensile strength for ENAcomposites increase by 19.44%. When coir pith is subjected toalkaline environment, the waxy material gets removed from thepith surface and increases its surface roughness. And also itpromotes the activation of hydroxyl groups of cellulose unit bybreaking hydrogen bonds, which in turn makes it less hydrophilic[36]. The chemically treated coir pith shows a rougher surface

Table 2Mechanical strength of composites.

Sample code Tensile strength (MPa) Flexural strength (MPa) Impact strength (J/m) Impact retention (%) Hardness (shore A)

BLANK 4.21 ± 0.2 27.32 ± 0.4 83.14 ± 0.5 95.1 ± 0.2 94.00 ± 0.3ERCP 5.22 ± 0.3 32.87 ± 0.3 101.35 ± 0.4 85.7 ± 0.2 95.60 ± 0.4ENA 6.48 ± 0.2 38.95 ± 0.3 132.64 ± 0.5 96.7 ± 0.3 96.09 ± 0.4EN2L 7.03 ± 0.3 42.31 ± 0.4 167.38 ± 0.5 96.8 ± 0.4 94.50 ± 0.4EN3L 7.51 ± 0.2 48.90 ± 0.3 189.97 ± 0.4 97.0 ± 0.2 95.56 ± 0.3ERCPN2L 7.57 ± 0.3 53.19 ± 0.4 214.29 ± 0.6 87.6 ± 0.3 96.62 ± 0.3ENAN2L 8.51 ± 0.2 68.56 ± 0.2 248.13 ± 0.5 91.3 ± 0.2 97.58 ± 0.2ERCPN3L 11.3 ± 0.2 75.22 ± 0.3 311.52 ± 0.4 93.1 ± 0.4 98.61 ± 0.3ENAN3L 12.5 ± 0.2 106.52 ± 0.4 359.88 ± 0.5 97.8 ± 0.3 99.73 ± 0.4

Coir pith

CH2

C6H5-C(CH3)2-C6H4-O-CH2

Epoxy resin

Nylon fabric

Treated Coir pith

Scheme 1. Hydrogen bonding interaction between treated coir pith/nylon 6 fabric/epoxy resin.

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morphology as is evident from the SEM photographs (Fig. 2a andb). The optical photographs support this further as shown inFig. 2c and d. The rougher morphology of treated coir pith resultsin enhanced mechanical bonding by an interlocking method [16].This results in better stress transfer among the components incomposites systems. Factually, epoxy is able to fill up the apparentflaws in treated coir pith and results in better load sharing.

4.2. Flexural strength

Flexural strength of epoxy composites are shown in Table 2. Thereinforcement increases the flexural strength of epoxy resin. Theincorporation of coir pith increased the flexural strength of epoxyby 16.88%. Meanwhile the incorporation of nylon fabric enhancedthe flexural strength of resin by 35.42%. The three layered nylonfabric had 7.94% higher flexural strength that two layered nylonepoxy composites. The presence of double and triple layer fabricplays an important role in sandwich composites. In three layersof nylon fabric composites, the upper layer is put into compression,the lower layer into tension and the core or middle layer of nylonact as shear. Upper and lower layer of nylon fabric are subjected tocompression/tension and are largely responsible for the strength ofthe sandwich laminate. Though the usage of middle layer of nylonis to support the upper and lower layer of nylon, so that theydrastically reduce the maximum stress and deformation of outerlayer by increasing the moment of inertia of the sandwich beam.Based on the sandwich theory, it can be expected that triple layerof nylon fabric epoxy composites withstand high stress duringbending and good resistance to propagation of cracks compare to

double layer of nylon fabric epoxy composites [20,21]. The hybridcomposites showed maximum flexural properties. The three lay-ered hybrid composites showed a flexural strength value of75.22 MPa which is 34.99% higher than nylon/epoxy composites.Composite samples with chemically treated coir pith showed bet-ter flexural properties than the samples with raw coir pith. The en-hanced interfacial interaction among the composites constituentsis expected to be responsible for this.

4.3. Impact strength

Impact properties of materials are directly related to the overalltoughness of the material. Toughness means the ability of thematerial to absorb applied energy. Impact strength of compositesis given in Table 2. The composites showed higher impact strengththan pure epoxy resin. The impact strength of composite increasedwith increasing number of nylon fabric. It is also clear from the Ta-ble 2 that sodium hydroxide treated coir pith increases the rein-forcement efficiency of the pith in epoxy matrix.

SEM observation of impact fracture surface of ERCPN2L andENAN2L composites is shown in Fig. 3a and b. The involvementof fillers in the failure is due to the separation of fillers and matrixand loss of stress transferring capability. Fig. 3a. indicates pooradhesion between the filler and matrix. This may be due to hydro-philic nature of coir pith resulting in fragile bond formation withhydrophobic epoxy resin. SEM photograph of fractured surfaceshows pith ejection at a number of places giving rise to holes.The presence of voids, debris and air entrapment visible in theSEM photographs indicates poor bonding between the pith and

Fig. 2. (a) Scanning electron microscope photographs of raw coir pith (b) scanning electron microscope photographs of sodium hydroxide treated coir pith (c) opticalmicroscopic images of raw coir pith and (d) optical microscopic images of sodium hydroxide treated coir pith.

Fig. 3. SEM images of (a) impact failure fracture surface of ERCPN2L composites and (b) impact failure fracture surface of ENAN2L composites.

648 R. Narendar et al. / Materials and Design 54 (2014) 644–651

matrix, ultimately effecting the composite properties. The fracturesurface of ENAN2L composites appears smooth with lesser numberof holes, when compared to ERCPN2L composite fracture surface.This is an evidence of good bond existing between coir pith andmatrix due to chemical treatment.

4.4. Hardness properties

Hardness of composite samples is given in Table 2. Compared toblank sample, the composite samples show higher hardness values.

The presence of nylon fabric slightly enhances the hardness ofcomposites further. The hybrid composite shows the highesthardness values. An increase in hardness is observed withchemically treated coir pith. Raw coir pith is highly amorphousand fluffy material because of its high lignin content. Chemicaltreatment results in the formation of cellulose rich product whichis more crystalline nature [37,38]. During chemical treatment, thelignin part of the coir pith gets removed resulting in cellulose richproduct. The FTIR spectra of treated and untreated coir pith areshown in Fig. 4. The peak at 1732.16 cm�1 in untreated coir pith

R. Narendar et al. / Materials and Design 54 (2014) 644–651 649

is attributed to acetyl or uronic ester linkage of hemicelluloses andor ester linkage of carboxylic group of ferulic or p-coumeric acidsof lignin or hemicelluloses [39]. The aromatic peak C@C stretchfrom aromatic ring of lignin gives two peaks at 1612 cm�1 and1456 cm�1. The peak at 1240.11 cm�1 in untreated coir pith isdue to hemicelluloses; the intensity of peak decreased in treatedcoir pith indicating the removal of hemicelluloses content in trea-ted coir pith. The peak at 1388.36 cm�1 in raw coir pith corre-sponds to ACH symmetric stretching of aromatic lignin and thispeak is shifted in treated coir pith, indicating the deformation oflignin in treated pith. NaOH treated coir pith shows a peak at3444 cm�1 corresponding to cellulose-OH. The increased intensityof this peak in treated samples indicates increased cellulose con-tent with treatment.

4.5. Ageing studies – in water

The composites samples were subjected to ageing to ascertaintheir utility during applications. The percentage retention of im-pact strength of composites after exposing to water is given in Ta-ble 2. The composites samples with coir pith showed a slightdecrease in impact strength on exposure to water. This result indi-cates that the presence of coir pith do not favor application of com-posites samples in moist environment. The hygroscopic nature ofcoir pith results in high water uptake by the composites samples.Water filled voids at the interface results in interfacial de-bonding.This causes cracks and micro-voids in the surface of composites[40]. The water filled voids at the interface results in interfacialde-bonding. Once water penetrates inside composites materials,pith start swelling and matrix tend to chain reorientation resultingin poor mechanical properties. However, the composites with trea-ted pith showed improved water resistance and retention ofmechanical properties even on being exposed to water environ-ment. The chemical treatment of coir pith effectively improvedpith–matrix adhesion. The alkaline sensitive hydroxyl groups pres-ent among the molecules are broken down. They react with watermolecules and move out from the coir pith structure. The remain-ing reactive molecules from pith–cell–ONa groups between thecellulose molecular chains (Scheme 1). Due to this, hydrophilic hy-droxyl groups are reduced and increase the coir pith moistureresistance properties [36]. The nylon/epoxy composites were al-most not affected on exposure to water. This may be due to thehydrophobic nature of nylon fabric. The nylon/coir pith/epoxy hy-brid composites with treated coir pith showed maximum retentionof impact strength which is almost same as 3 layered nylon/epoxy

4000 3500 3000 2500 2000 1500 1000 50070

75

80

85

90

95

100

105

Tra

nsm

itta

nce

%

Wave number (Cm-1)

Treated coir pith

Raw coir pith

Fig. 4. FTIR spectra of raw and treated coir pith.

composites. These results indicate the importance of incorporationof nylon fabric and chemical treatment of coir pith in the presentinvestigation.

4.6. Flammability of composites

Composite materials are increasingly being used in applicationsin which their fire response is a critical consideration. Combustibil-ity of a natural fiber composite depends on a number of factorssuch as the type of natural fibers and polymers used for prepara-tion of composite, its density, structure, thermal conductivity andhumidity. Table 3 shows the quantitative results from the verticalburn experiments. The addition of coir pith increased the ignitiontime of composite. The decreased flammability with natural fibershas been reported earlier also [31,41]. The ignition time for coirpith/epoxy composites is found to be higher than the nylon/epoxycomposite. The hybrid composite with treated coir pith showedmaximum ignition time. This may be due the low percentage of lig-nin present in the composites systems due to the chemical treat-ment of pith. Manfredi et al. [42] in his work on polyesterreinforced with different natural fibers have indicated better ther-mal stability for fibers with low lignin content. The same trend isobserved for rate of burning. The composites samples with coirpith showed lower flammability than pure epoxy and nylon/epoxycomposites. The hybrid samples with coir pith and nylon showedleast rate of burning.

4.7. Chemical resistance

The ability of the composite samples to resist chemical environ-ment such as acid, alkali, solvent and water were tested and is gi-ven in Table 4. This clearly indicates that all composites have notlost the weight. The incorporation of raw coir pith decreased thechemical resistance of epoxy resin. The presence of nylon fabricwas found to overcome this to some extent though the values werefound to be higher than blank epoxy. The hybrid compositesshowed a lesser solvent uptake or increased chemical resistancecompared to coir pith/epoxy composite. Though the compositesamples with chemically treated samples showed better solventresistance, it was found to be still higher than pure epoxy resin.This may be due to increased interfacial bonding between pithand epoxy on chemical treatment resulting in reduced void con-tent. This increased interfacial interaction makes the polymericsegments around the filler immobile. These factors offer higherresistance to the movement of solvent molecules into the compos-ites system [43]. Restricted equilibrium technique has been used asa tool by many researchers to analyze the filler–matrix bonding inthe composites system [44,45]. It is reported that increased inter-facial interaction results in lower solvent uptake by compositessystems. Therefore the solvent uptake in solvent resistance forcomposites systems with treated coir pith may due to the in-creased interfacial interaction between filler and matrix.

Table 3Flammability test results.

Sample code Ignition time (s) Linear burning rate (mm/s)

BLANK 9.0 ± 0.2 64.28 ± 0.2EN2L 11.0 ± 0.2 61.43 ± 0.3EN3L 12.3 ± 0.1 59.36 ± 0.2ERCP 13.4 ± 0.2 58.35 ± 0.3ENA 14.1 ± 0.3 57.69 ± 0.1ERCPN2L 13.3 ± 0.2 58.87 ± 0.2ENAN2L 15.7 ± 0.1 56.16 ± 0.3ERCPN3L 14.8 ± 0.2 57.58 ± 0.2ENAN3L 16.4 ± 0.3 53.35 ± 0.2

Table 4Chemical resistance of epoxy composites.

Samples code HNO2 (%) H2O (%) NaOH (%) CCl4 (%)

BLANK 0.603 0.506 0.598 0.583EN2L 0.616 0.515 0.612 0.598EN3L 0.618 0.514 0.616 0.599ERCP 0.711 1.012 0.781 0.652ENA 0.651 0.616 0.583 0.628ERCPN2L 0.687 0.865 0.728 0.641ENAN2L 0.651 0.575 0.678 0.620ERCPN3L 0.648 0.732 0.709 0.630ENAN3L 0.635 0.566 0.644 0.621

650 R. Narendar et al. / Materials and Design 54 (2014) 644–651

5. Conclusion

The results of present study showed that composites with goodmechanical strength could be developed successfully by hybridiz-ing coir pith and nylon fabric in epoxy resin. Tensile strength, flex-ural strength, impact strength and hardness of hybrid compositeswere much higher than the composites. The mechanical strength,chemical resistance and flammability of composites were foundto be improved with chemical treatment. The properties of com-posites were considerably increased due to alkali treatment of pith.Thus in coir pith reinforced nylon/epoxy composite, improvementin bonding between the pith/nylon/epoxy resin could be achievedby surface treatment of the pith by alkali environment, whichcould promote its application in light weight materials industry.

Acknowledgements

The authors thank the management of VIT University, Vellorefor their whole heart support to research activities.

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