Thermoplastic olefin

Thermoplastic olefin (TPO), or olefinic thermoplastic elastomers refer to polymer/filler blends usually consisting of some fraction of a thermoplastic, an elastomer or rubber, and usually a filler. Thermoplastics may include polypropylene (PP), polyethylene (PE), block copolymer polypropylene (BCPP), and others. Common fillers include, though are not restricted to talc, fiberglass, carbon fiber, wollastonite, and MOS (Metal Oxy Sulfate). Common elastomers include ethylene propylene rubber (EPR), EPDM (EP-diene rubber), ethylene-octene (EO), ethylbenzene (EB), and styrene ethylene butadiene styrene (SEBS). Currently there are a great variety of commercially available rubbers and BCPP's. They are produced using regioselective and stereoselective catalysts known as metallocenes. The metallocene catalyst becomes embedded in the polymer and cannot be recovered.

The geometry of the metallocene catalyst will determine the sequence of chirality in the chain, as in, atactic, syndiotactic, isotactic, as well as average block length, molecular weight and distribution. These characteristics will in turn govern the microstructure of the blend.

Components for TPO are blended together at 210 - 270 °C under high shear. A twin screw extruder or a continuous mixer may be employed to achieve a continuous stream, or a Banbury compounder may be employed for batch production. A higher degree of mixing and dispersion is achieved in the batch process, but the superheat batch must immediately be processed through an extruder to be pelletized into a transportable intermediate. Thus batch production essentially adds an additional cost step.

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