Background CONCLUSION AND RECOMMENDATION 114

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1.1 Background

Polyolefins are the largest group of thermoplastics, the two most important and common types of polyolefins are polyethylene and polypropylene. They are very popular due to their low cost and wide range of applications. Polyolefins are usually processed by extrusion, injection molding, blow molding, and rotational molding methods. Polyolefin elastomers POEs are a relatively new class of polymers that emerged with recent advances in metallocene polymerisation catalysts. Representing one of the fastest growing synthetic polymers, POE’s can be substituted for a number of generic polymers including ethylene propylene rubbers EPR or EPDM, ethylene vinyl acetate EVA, styrene-block copolymers SBCs, and poly vinyl chloride PVC. Polyolefin elastomers are compatible with most olefinic materials, are an excellent impact modifier for plastics, and offer unique performance capabilities for compounded products. Thermoplastic elastomers based on natural rubber and thermoplastic blends are classified as thermoplastic natural rubber TPNR blends. There are two types of thermoplastic natural rubber. Blending of NR with thermoplastic i.e., polyolefins to get co-continuous phase morphology is technologically classified as thermoplastic polyolefin TPO. The other class is known as thermoplastic vulcanizate TPV, which is prepared by blending NR with polyolefins and involve vulcanization process. In type two, the rubber phase is vulcanized during the mixing process at INTRODUCTION CHAPTER 1 2 high temperature, and the process is known as dynamic vulcanization. Dynamic vulcanization of epoxidized natural rubber ENR and polypropylene PP are also performed by using either a sulfur based system or peroxide. The sulfur cured system showed superior mechanical properties in term of tensile strength, elongation at break and tension set compared to the peroxide system due to the polypropylene degradation during dynamic vulcanization.

1.2 Problem Statement