(UiTM ) Shah Alam Selangor, Malaysia. Kebangsaan Malaysia, Bangi, Selangor, Malaysia.

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1 Advanced Materials Research Online: ISSN: , Vol. 576, pp doi: / Trans Tech Publications, Switzerland Mechanical Properties and Environmental Stress Cracking Resistance of Rubber Toughened Polyester/Clay Composite N. N. Bonnia 1,a, S. H. Ahmad 2,b, S. N. Surip 1,c, S. S. Nurul, H. N. Azlina 3,d and H. Anuar 3,e 1,a Material Technology Programme,Faculty of Applied Sciences, Universiti Teknologi Mara 1,c Programme of Biocomposite Technology,Faculty of Applied Sciences,Universiti Teknologi Mara (UiTM ) Shah Alam Selangor, Malaysia 2 Department of Material Science, School of Applied Physics, Faculty of Science, Universiti Kebangsaan Malaysia, Bangi, Selangor, Malaysia. 3 Department of Manufacturing and Materials Engineering, Faculty of Engineering, International Islamic University Malaysia, P.O. Box 10, Kuala Lumpur 50728, Malaysia a noornajmi@salam.uitm.edu.my/najlinn@yahoo.com, b sahrim@ukm.my, c snorasmah@salam.uitm.edu.my, d noorazlina_hassan@iium.edu.my, e hazleen@iium.edu.my Keywords: Polyester, Rubber Toughened, Thermoset,nanoclay Abstract.Crosslinked polyester clay nanocomposites were prepared by dispersing originically modified montmorillonite in prepromoted polyester resin and subsequently crosslinked using methyl ethyl ketone peroxide catalyst at different clay concentration. Cure process and the mechanical properties of rubber toughened polyester clay composite have been studied. Rubber toughened thermoset polyester composite were prepared by adding 3 per hundred rubber (phr) of liquid natural rubber (LNR) was used in the mixing of producing this composite. Modification of polyester matrix was done due to the brittle problem of polyester composite. Addition of LNR will increase the toughness of composite and produce ductile polyester. Two types of composites were produced which is clay-lnr polyester composite and clay polyester composite. Addition of liquid natural rubber significantly increased the impact strength and flexural properties. Result shows that addition of 6% of clay-lnr composite give good properties on impact, strength and flexural. From the ESCR test, both composites showed good resistance to environmental. Introduction Polymer nanocomposites, especially polymer-layered silicate nanocomposite, represent a rational alternative to conventionally filled polymers. Because of their nanometerscale dispersion, it exhibit markedly improved properties such as lighter weight, outstanding barrier and good mechanical properties when compared with the pure polymers or conventional composites [1]. Polymer layered nanocomposites can be classified into three types; (i) intercalated (ii) flocculated (iii) exfoliated nanocomposites [2]. Thermoset unsaturated polyester (UP) can be dissolved in a polymerizable monomer such as styrene monomer. Polyester resins are widely used as a matrix in polymer composites, but polymerization of this resin will result in brittleness due to high crosslinking level. The addition of a low molecular weight reactive liquid rubber can improve fracture toughness and impact strength of cured epoxy resin [3]. The purpose of introducing dispersed rubber particles from LNR into the primary phase in the polyester resin systems is to enhance it toughness. It is known that both the rubber particle size and volume fraction affect the degree to which the polyester is toughened [4]. Liquid natural rubber (LNR) will increase strength of produced composite [5].This study was undertaken to investigate the mechanical and morphological properties of rubber toughened polyester nanocomposite. Two types of composite were produced which is toughened nanoparticles Cloisite 30B polyester composite and non toughened nanoparticles polyester composite. Liquid natural rubber (LNR) was produced using degradation photo oxidation reaction of natural rubber. All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of Trans Tech Publications, (ID: , Pennsylvania State University, University Park, USA-04/03/16,02:57:44)

2 Advanced Materials Research Vol Apparatus and procedures Sample Preparation a) Neat Polyester Unsaturated polyester (Reversol UN 8100 P-8542CSH) from Revertex Sdn.Bhd. Malaysia was used in this research. Polyester resin mixed together with catalyst [methyl ethyl ketone peroxide (MEKP)].The stirring process took about 30 minutes before mix with the harderner which is cobalt octanoate 1%. b) Toughened polyester + Cloisite 30B Toughened composite is prepare by adding polyester resin with LNR and the stirred the mixture for 1 hour. After that addition of Cloisite 30B with composition of 2-8 % and stir it for 4 hours. Then MEKP and harderner were added to the mixture. After the stirring process, mixture was put into the mould and leave at room temperature for 24 hours. The resulting board was post cured at 60 C for 2 hours, 90 C for 90 minutes, 120 C for hours and 150 C for 30 minutes. The mechanical and morphological properties and effect on environment then evaluated. Result and Discussion Impact Strength. Impact strength of the toughened composite is higher compare to non-toughened composite. Fig. 1 shows the impact strength of toughened polyester filled Cloisite 30B and non toughened polyester filled Cloisite 30B. It shows that addition of LNR reduced brittleness of the composite and enhanced ductility of toughened polyester. Fig. 1: Impact strength of composite Increasing percentage of Cloisite 30B in the composite increased the impact strength of both type of composite until 6 % clay and the value decreased at 8 % of clay. This is due to the agglomeration of clay in the composite and reduces the percentage of clay dispersion inside the composite. Increasing of nanoclay percentage will increase degree of dispersion and decrease degree of cross-linking process [6].Addition of LNR had improved impact strength of composite. Flexural Strength. Toughened composite give higher flexural strength compared to non toughened composite. Figures 2 and 3 shows that addition of nanoclay has increased the flexural strength and flexural modulus of composite.

3 320 Advances in Manufacturing and Materials Engineering Fig. 2: Flexural modulus of composite Fig. 3: Flexural strength of composite Maximum flexural strength is on 4 % clay with LNR, which is 70 MPa, while flexural modulus is MPa. The increasing and decreasing strength of the composite is related to the intercalation and exfoliation of clay in the polyester resin which is effectively decrease number of crosslink in the composite [7]. Environmental Stress Cracking resistance (ESCR). Environmental stress cracking resistance (ESCR) is the premature initiation of cracking and embrittlement of a plastic due to the simultaneous action of stress and strain in contact with a specific fluid. It is also described as environmentally assisted cracking [8]. Figures 4 and 5 show that stress value decreased slowly, whether the composites had acid or base medium.the test was undertaken in control medium (Air), 1% sodium hydroxide (ph 13.5) and 1% hydrochloride acid (ph 2.5) medium. Figures 4 and 5 indicates that over time (3000s) polyester composite without clay decreased the stress more compare to polyester clay composite. Both type of composite shows decreased in stress about 17% over a time. However, acid medium weakened the composite more rapidly than base medium. Fig. 4: ESCR of Polyester Fig. 5: ESCR of polyester clay Fig. 4 and 5 reveals that when the stressed composite is exposed to a chemical environment, the polymer resistance to acid and base varies with time. Since micro crazes, crack the polymer exposed to chemicals, it will tend to have both a shorter time to rupture and a lower stress value, compared to those of a control specimen without medium.

4 Advanced Materials Research Vol Conclusions Liquid natural rubber is a potential material as toughening agent for polyester resin. Impact and flexural properties were improved significantly with increasing filler volume fraction and liquid natural rubber. ESCR study shows that the composites are more affected on acid medium followed by base medium. Acknowledgement We acknowledged Ministry of Higher Education, Malaysia for the financial support under project: 600 RMI / ST / FRGS 5/ 3FST (40/2010) Material Technology Laboratory FSG UiTM, Universiti Teknologi Mara (UiTM), and Universiti Kebangsaan Malaysia. References [1] Suh, D. J., Lim, Y. T. & Park, O. O..The property and formation mechanism of unsaturated polyester-layered silicate nanocomposite depending on the fabrication methods. Poly. 41(2000) [2] William Gacitua E., Ballerina Aldo A., 2005, Polymer Nanocomposites: Synthetic and natural fillers a review. [3] Ismail Z.,Ahmad, I.B.,Zakaria, F. A., Ramli, A., Ahmad Marzuki, H.F., Abdul Aziz, A. Modification of epoxy resin using liquid natural rubber. Material Science Forum. 517(2006) [4] Russell B. & Chartoff R. The influence of cure conditions on the morphology and phase distribution in a rubber modified epoxy resin using scanning electron microscopy and atomic force microscopy. Polymer. 46 (2005) [5] Dahlan H.M., Khairul Zaman, M.D., Ibrahim A..Liquid Natural Rubber (LNR) as a compatibiliser in NR/LLDPE blends 11: The effect of electron-beam (EB) irradiation. Radiation Physics & Chemistry 64 (2002) [6] Bharadwaj, R.K., Mehrabi, A.R., Hamilton,C.,Trujillo,C.,Murga,M.,Fan,R.,Chavira, A. & Thomson, A.K.. Structure-property relationships in cross-linked polyester-clay nanocomposites. Polymer 43(2002) [7] Kim B. C., Park S.W., & Lee D.G Fracture toughness of the nana-particle reinforced epoxy composite, Composites Structures. [8] Wright D.R: Environmental stress cracking of plastic. Rapra Technology,Shawbury (1996)

5 Advances in Manufacturing and Materials Engineering / Mechanical Properties and Environmental Stress Cracking Resistance of Rubber Toughened Polyester/Clay Composite /