Polyolefin copolymers Ethylene-propylene-diene monomer elastomers

TPO materials are defined as compounds (mixtures) of various polyolefin polymers, semicrystalline thermoplastics, and amorphous elastomers. Most TPOs are composed of polypropylene and a copolymer of ethylene and propylene called ethylene—propylene rubber (EPR) [2]. A common rubber of this type is called ethylene propylene diene monomer rubber (EPDM), which has a small amount of a third monomer, a diene (two carbon-carbon double bonds in it). The diene monomer leaves a small amount of unsaturation in the polymer chain that can be used for sulfur cross-linking. Like most TPEs, TPO products are composed of hard and soft segments. TPO compounds include fillers, reinforcements, lubricants, heat stabilizers, antioxidants, UV stabilizers, colorants, and processing aids. They are characterized by high impact strength, low density, and good chemical resistance they are used when durability and reliability are primary concerns. 

The polyolefins are those polymers based only on carbon and hydrogen, originating from monomers containing a double bond in the 1-position, sometimes called a-olefins. Principally, these include polyethylene, polypropylene, copolymers of polyethylene containing various comonomers such as 1-butene, 1-hexene, and 1-octene, ethylene-propylene monomer (EPM), and ethylene-propylene-diene-monomer (EPDM). All of these are plastics except EPM and EPDM, which are elastomers. 

Polyolefins, PO. First impact modification of PO, by addition of elastomers, was patented independently by Bayer A.-G. and Standard Oil Co. in 1937. The isotactic polypropylene, PP, was commercialized in 1957, and its first blends (with polyisobutylene, PIB, and polyethylene, PE) were patented in 1958. In 1960, du Pont started manufacturing ethylene-propylene, EPR, and three years later ethylene-propylene-diene, EPDM, copolymers [Gresham and Hunt, I960]. The first patent on impact modification of PP by addition of EPR dates from 1960. Direct reactor blending of PE/PP/EPR resulting in a thermoplastic polyolefin, R-TPO, dates from 1979. The newest (introduced in 1992) single-site metallocene catalysts generate polymers with controlled tacticity, co-monomer sequences, molecular... 

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