INFLUENCE OF REGRIND ON PROPERTIES OF ...fstroj.uniza.sk/journal-mi/PDF/2011/08-2011.pdfĽ. Dulebová, F. Greškovi č: Influence of regrind on properties of plastics processing by

Ľ. Dulebová, F. Greškovič: Influence of regrind on properties of plastics processing by injection moulding

Materials Engineering - Materiálové inžinierstvo 18 (2011) 44-48

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INFLUENCE OF REGRIND ON PROPERTIES OF

PLASTICS PRODUCED BY INJECTION MOULDING Ľudmila Dulebová1,*, František Greškovič1

1Department Technologies and Materials, Faculty of Mechanical Engineering, Technical University of Košice, Mäsiarska 74, 040 01 Košice, Slovak Republic

*corresponding author: Tel.: +421 55 602 3544, e-mail: [email protected]

Resume The contribution deals with the evaluation of results of selected mechanical tests. Materials Crastin® PBT (with 30 % glass fibre) and Celanex® 2004-2 PBT (without filler) were used at tests with various percentage of added regrind into basic material. The mechanical properties were obtained by tensile test and Shore hardness test. Utilization of regrind at the production of new moulded parts is important from aspect of reduction plastics waste and pollution abatement of environment.

Available online: http://fstroj.uniza.sk/PDF/2011/08-2011.pdf

Article info

Article history:

Received 30 May 2011 Accepted 29 June 2011 Online 14 July 2011

Keywords:

Plastics Regrind Injection moulding Tensile test Hardness test ISSN 1335-0803

1. Introduction

Plastics are nowadays the most important segment of production and consumption by volume among the all technical material. Ever since the emergence of plastics and more frequent application in all aspects of industry, this material has the necessary respect and a unique place on the world market for used materials [1].

Involvement in the production of this material also has negative aspects. In environmental terms, plastic is too burdensome for the ecosystem. Their decomposition takes a long time and when burning a very large number of harmful emissions [2]. Therefore places a high priority on the ecological and especially effective recycling of used waste from these materials. Great development of plastic products also brought with it the problem of waste management. In practice, therefore, a need to make more recycled plastics and this material was used to production of new products [3].

Mixing the primary material with recycled material are often occurs, although with an identical designation as the primary material, but the value of some of its properties may be altered [4, 5].

The benefits of plastic recycling:

• important saving of primary materials,

• use of recycled product for new applications,

• new possibilities for products made from recycled materials,

• minimization, mainly communal waste,

• creation of new employment,

• conservation of matter (as opposed to energy assessment).

Restrictions of plastic recycling:

• not all waste can be reused for the original use of products - e.g. packages,



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• recycled product often has new features, and recycled once the product becomes waste,

• recycling of recycled product may no longer be effective and justified,

• plastic parts and products of foreign production are also on the market, where recycling in view of their quantity, specifications may not be effective and realizable [6,7].

The article aims to investigate the influence of regrind on selected mechanical properties of plastics with and without filler. Materials are used in the automotive industry. It was further of experiments to determine whether there was a change in the coefficient of relationship strength - hardness of materials with various % regrind.

2. Experimental material and methods

Influence of regrind added into the basic material on the change of the mechanical properties of plastic was determined by tensile test and Shore hardness test. Tests were conducted on the test specimens with a 0%, 20%, 40%, 70% and 100% regrind in the basic material.

Material PBT (polybutylentereftalat) was used for experimental testing:

• DUPONT Crastin® LW9330 PBT – No. 899921002, mineral composite with 30% glass fibre.

• TICONA Celanex® 2004-2 PBT - No. 899921006 colour NATURAL, without filler.

Material PBT belong to group of polyester plastics. It is semicrystalic polymer what utility properties belong into group of engineering plastics and both testing materials have used in the automotive industry [7].

The samples were made by injection moulding, with using of the injection press type

Battenfeld, type HM 1000/350 according to STN EN ISO 294-1 in the Department of Technologies and Materials, Faculty of Mechanical Engineering, Technical University in Košice. The tested samples were made in multiple ISO injection mould [8].

The experimental verification of the influence of regrind on mechanical properties was tested according to STN EN ISO 527 – tensile test. The tensile machine TIRA- test 2300 was used for the test. Five samples were tested for each material.

Shore hardness test was done according to STN ISO 868 (64 0129). The test was performed on the Shore Hardness Tester type D producer HARDMATIC Mitutoyo. Shore hardness was measured on samples with dimensions 60 mm x 60 mm x 2 mm. It was used for testing of five pieces of samples of each material. On the samples were performed for five measurements in the direction and vertically to the direction of melt flow.

3. Results and discussion

In the tensile test were evaluated parameters yield strength and tensile strength. In the Figure 1 are presented σY for samples with various % regrind of experimental materials. Graphic dependence measured values σM of test samples shown in Figure 2. Average values of Shore hardness of tested materials shown in Figure 3.

Fig. 1. Average values of yield strength

of tested material



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Fig. 2. Average values of tensile strength

of tested material

Fig. 3. Shore hardness of tested materials

with various % regrind

Break planes of testing samples were observed on scanning electron microscope JEOL JSM – 7000F, Japan. Structure of polymeric material Crastin® PBT after tensile test is shown in the Figure 4 (basic material). Structure of material with 100% regrind is shown in Figure 5.

Fig. 4. Structure of testing material Crastin® PBT

matrix of basic material (0 % regrind)


matrix of material with 100% regrind

Structure of material Crastin® PBT after tensile test is shown in the Figure 6 and failure of glass fibre is shown in Figure 7.


after tensile test, failure of basic material (0 %

regrind)


after tensile test, - detail (100 % regrind)



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Hardness tests are effective and simple means for estimating the mechanical strength of materials. The paper studied the relationship between hardness and strength of experimental material. The ratio of tensile strength to hardness of experimental materials as a factor “k” is shown in Table 1 and Table 2.

Tab. 1

Comparison of the values of strength and hardness

of material Crastin® PBT

Material Crastin® LW 9330 PBT

regrind (%)

0 20 40 70 100

σM (MPa) 47 50 50 50 50

ShD 85 85 85 85 84

k 0.55 0.59 0.59 0.59 0.59

Tab. 2

Comparison of the values of strength and hardness of

material Celanex® PBT

Material Celanex® 2004-2 PBT

regrind (%)

0% 20% 40% 70% 100%

σM (MPa) 119 119 112 108 110

ShD 79 79 80 79 78

k 1.51 1.51 1.4 1.37 1.41

On the basis of experimental tensile test and Shore hardness test of tested materials were reached the following conclusions:

• The value σY of tested material with glass fibre has tendency to decline about 8%. For the material without glass fibre there wasn´t found change of this value.

• At evaluation of the parameter σM we draw conclusion to similar results i.e. with increasing the percentage of regrind to material there was the decrease of value σM

(material with glass fibre). For the material without glass fibre there wasn´t found change of this value.

• Shore hardness test hasn’t determined the influence of added regrind into the basic material (scilicet in the direction and vertically to the direction of melt flow).

• On the basis of compared values of measurements listed in Table 1 and Table 2, we can conclude that the hardness of the surface

• layers of moulded samples of tested materials showed no variation depending on the percentage of regrind.

4. Conclusion

Requirements that are imposed for plastic products can only be met with a good knowledge of mechanical, physical, electrical, chemical, optical and biological properties. Anisotropy of mechanical and physical properties of molding products of fiber-reinforced plastics is considerably greater than the unreinforced. The presence of different additives in the basic material, for example glass fibers can sometimes completely change dependence that apply for unreinforced plastics.

Growing applications of plastics for technically demanding parts ever put greater demands on the level of knowledge about the behavior of these materials, particularly in conditions of mechanical stress.

Before application of completed parts moulded with regrind it is necessary to verify technological moulding conditions with additional technological tests in conditions of application in praxis.

Acknowledgements

This contribution is the result of the

project implementation: Center for research of

control of technical, environmental and human

risks for permanent development of production



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and products in mechanical engineering ( ITMS:

26220120060) supported by the Research

&Development Operational Programme funded

by the ERDF.

References

[1] F. Greškovič, Ľ. Dulebová, J. Varga: Technológie spracovania plastov. Vstrekovanie. (Plastics Processing Technologies. Injection

Moulding), SjF TU v Košiciach Košice, 2010 (in

Slovak).

[2] T. Forss, M. Puide, B. Terselius: International J. Environmentally Conscious Design & Manufacturing 10(4) (2001) 23-36.

[3] E. Gondár, M. Knap, S. Žuffová: In. Technológia 2009, SjF STU Bratislava, Bratislava 2009, pp.36-42 (in Slovak).

[4] L.Běhálek: Acta Mechanica Slovaca 12(3a) (2008) 39-44.

[5] R. Syang-Pen, J. Zhi-Feng, , L.Ch. Frank: Polymer Eng. and Sci. 44(2) (2004) 331-344.

[6] P.A. Eriksson, A.C. Albertsson, P. Boydell, G. Prautzsch, J.-A. E. Månson: Polymer Composites 17 (1996) 830-839

[7] Ľ. Dulebová: Vplyv regranulátu na vlastnosti výliskov vyrábaných vstrekovaním. (The

Influence of Regrind on the Properties of

Moldings Parts produced by Injection Molding.

SjF TU v Košiciach Košice 2008 (Disertation

thesis), (in Slovak).

[8] F. Greškovič, Ľ. Dulebová, J. Varga: Mater.Eng./Mater.inž. 14(2) (2007) 77-80.

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INFLUENCE OF REGRIND ON PROPERTIES OF ...fstroj.uniza.sk/journal-mi/PDF/2011/08-2011.pdfĽ. Dulebová, F. Greškovi č: Influence of regrind on properties of plastics processing by