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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