The poor compatibility between a thermoplastic matrix and natural fiber reinforcement has been a limitation in the optimization of natural fiber-filled composites. Electron beam irradiation is used to modify the structure of materials. However, most researches have focused on the effect of irradiation after the fabrication of composites. Hence, this study was aimed at investigating the effect of irradiated recycled polypropylene (i-rPP) as a compatibilizer in recycled polypropylene (rPP) composites. The rPP were irradiated at different doses before the compounding process. The rPP matrices were prepared by mixing the unirradiated and irradiated rPP at ratios of 90:10 and 50:50, before they were compounded with different amounts of microcrystalline cellulose (MCC) fibers (5, 20, and 40 wt%). Radiation crosslinking, functional groups, radical formations, thermal, and impact strength characterizations were carried out. The results showed that the simultaneous incorporation of the i-rPP and MCC fibers significantly improved the impact resistance of the rPP. The synergistic combination of a higher MCC content (40 wt%) and low irradiation dose (10 kGy) at a ratio of 50:50 caused a higher degree of crosslinking and a lower radical concentration. The thermal stability was acceptable and the sub-impact fracture surface analysis revealed the effects of crack blunting. POLYM. COMPOS., 00:000-000,

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Effects of irradiated rPP compatibilizer, on the mechanical and thermal properties of recycled polypropylene/microcrystalline cellulose composites (rPP/MCC), are investigated. rPP is irradiated with an electron beam at dosages ranging from 10, 20, 30 to 50kGy. A matrix, containing of unirradiated and irradiated rPP (50:50 by ratio), is then added to 5, 20 and 40wt% MCC fibres. The composites are prepared using a twin screw extruder, followed by injection moulding. The properties are then characterized using tensile and thermal degradation tests. The improvement of Young’s modulus by up to about 45% suggests a compatibilising effect of the irradiated rPP. Fracture surface observations reveal an adhesion between rPP matrix and MCC fibres. However, the thermal stability deteriorated with the addition of MCC and irradiated rPP.

Natural rubber latex (NRL) is a natural polymer with versatile properties.However, uncured NRL has low strength and limited practical use. Therefore, we utilized low-dose gamma irradiation to induce cross-linking in blended NRL/poly(styrene-block-isoprene-block-styrene) (SIS). Blends were prepared in various ratios, and the 70 NRL /30 SIS blend gave optimal mechanical properties. The 70 NRL /30 SIS blend was then irradiated from 4 to 16 kGy. An exposure of 12 kGy led to the highest tensile strength (4.49 MPa), Young's modulus (0.41 MPa), gel content (45%), and cross-link density (12.18 Â 10 À5 molÁcm À3 ).The results of study show irradiation has improved the crystallinity of the polymer blend, which has been determined by the formation of a new NRL crystal peak at 31.2 and the decrease of the crystallization temperature from 58 to 19 C due to strain-induced crystallization. Moreover, the radiation has trans-

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Natural rubber (NR) is a renewable natural resource that has been utilized in many applications. Due to its low tensile strength, NR is commonly blended with another polymer to improve the properties of NR. However, most of the blended NR has miscibility issue, leading to poor mechanical properties. Gamma irradiation (GR) is a safe and green alternative than conventional chemical method for inducing crosslinking in blended NR. This study was aimed at investigating the mechanical and thermal properties of NR/liquid natural rubber/polystyrene-block-polyisoprene block copolymer (NR/LNR/PS-b-PI) blend using GR method. The polymer blend is prepared according to the ratio of NR:LNR:PS-b-PI of 6:1:3 using an internal mixer. The NR/LNR/PS-b-PI blends are irradiated with gamma ray at doses of 0, 5, 6, 7, 8 and 9 kGy. Tensile and thermal tests are conducted to evaluate the properties of unirradiated and irradiated polymer blend. The tensile strength and modulus of the irradiated blend are increased with increasing irradiation dose before decrease at 9 kGy. Lower melting point of blend indicates that PS-b-PI are compatible in NR/LNR blend. The improvement in tensile properties of irradiated NR/LNR/PS-b-PI blend is related to the radiation-induced crosslinking.

Abstract. Polypropylene (PP) is a thermoplastic that is used in many applications. Hence, the recycling of PP is very important for the sustainability of the environment. However, the properties of recycled PP (rPP) are lower compared to virgin polypropylene due to the rupturing of its structure during the recycling process. One of the techniques that can be used to modify the polymer structures is electron radiation. This study was aimed at investigating the compatibility of irradiated rPP in rPP composites reinforced with microcrystalline cellulose (MCC). The rPP/MCC composites were prepared according to the ratio of 70/30 wt% (unirradiated/irradiated) rPP, before the addition of various compositions of MCC at 5, 20 and 40 wt%. The rPP resin pellets were irradiated with 5, 20 and 50 kGy before the compounding process. Mechanical and water resistance tests were conducted to evaluate the compatibility of the composites. The results showed that the mechanical properties were improved at a certain electron radiation dosage and MCC loading. Although the water resistance deteriorated at higher MCC loadings, the radiation dosage did not influence this property.

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