Polyolefin thermoplastic olefins TPOs

Thermoplastic olefin (TPO) compositions typically consist of an immiscible blend of an isotactic polypropylene mixed with a polyolefin elastomer that acts as an impact modifier. It is possible to toughen these compositions further by using ethylene-propylene, ethylene-octene or ethylene-hexene impact modifiers. 

TPEs which are prepared by physical blending of an elastomer with a thermoplastic. Such TPEs are categorized into two types depending on rubber vulcanization (i) thermoplastic olefins (TPOs) or thermoplastic elastomer polyolefins (TEOs) (ii) thermoplastic vulcanizates (TPVs). 

TPEs are blends of various amorphous rubbers such as ethylene-propylene and of polyolefin semicrystalline plastics such as PP. They are part of the family of TP olefins (TPOs). TPOs are mechanical blends consisting of a hard plastic and softer rubber. They are considered different from blends that are dynamically thermoplastic vulcanized (TPV) a process in which the elastomer phase is cured during mixing of the polymers.84 94... 

In 1979 UNIPOL process for gas-phase production of LLDPE was introduced by the UCC. Since the new resins were difficult to process on the LDPE processing lines, several patents were issued for LLDPE blends with, e.g., LDPE or PP, which had better processability In 1982 a number of patent applications for blends of LLDPE, with other polyolefins, co-polyolefins, and olefinic elastomers, for example, ethylene copolymers and thermoplastic elastomers (e.g., TPO, EPDM, EPR, EVAc, PP-MA,), have been filed... 

Thermoplastic polyolefin (TPO) is a generic name that refers to polyolefin blends usually consisting of some fraction of polypropylene (PP), polyethylene (PE) or polypropylene block copolymer (PP-b-EP or BCPP ), and a thermoplastic olefinic rubber, with or without a mineral reinforcing filler such as talc or wollastonite. Common rubbers include ethylene propylene rubber (EPR), EPDM rubber, ethylene-octene (EO) copolymer mbber, ethylene-butadiene (EB), and styrene-ethylene-butadiene-styrene (SEBS) block copolymer rubbers. Currently, there are a great variety of commercial polypropylene homopolymers, PP block copolymers, and olefinic rubbers available to make a wide range of TPO blends with densities ranging from 0.92 to 1.1. 

Thermoplastic Elastomers (TPE) are classes of heterophasic polymers, characterized by thermo-reversible interaction among the polymeric chains. The new polymeric materials that are considered to produce easy recyclable automotive systems, can be defined as a sort of a new generation of Olefinic Thermoplastic Elastomers (TPO), belonging to a broad family of polyolefinic alloys that can now be produced directly dining the polymerization phase. These completely new materials, resulting from advanced research and development carried out by HIMONT, can be tailored in order to meet different requirements of most of car apphcations. The basic partly finished components suitable for the constructions of the main automotive composite structru-es will be described. 

Olefinic thermoplastic elastomer (TPO) materials are defined as compounds (mixfures) of various polyolefin polymers, semicrysfalline thermoplastics, and amorphous elastomers. Most TPOs are composed of polypropylene and a copolymer of ethylene and propylene called ethylene-propylene rubber (EPR) [10]. A common rubber of this type is called ethylene-propylene diene monomer (EPDM) rubber, 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. 

Obviously, there exists severe interplastics competition, e.g. PP vs. ABS, clarified PP vs. PS, PA, PVC, HDPE and PS (Table 10.7). A wide range of cross-linked and thermoplastic elastomer applications, from footware to automotive parts and toothbrushes, are adopting new metallocene-catalysed polyolefin elastomers (POEs). These low-density copolymers of ethylene and octene were first accepted as impact modifiers for TPOs, but now displace EPDM, (foamed) EVA, flexible PVC, and olefinic thermoplastic vulcanisates (TPVs). Interpolymer competition may also result from... 

Plastic types are variable, ranging from flexible to rigid and from thermoplastic to thermoset. Because of these variations, the type of coating applied to them also varies, depending on cure response, solvent sensitivity, and modulus. The type of coating also depends upon the end use of the coated plastic. For example, topcoats can be applied directly to the plastic without the use of a conductive primer if two-toning or blackout areas are not part of the styling latitude. Adhesion promoters also are often utilized if a particularly difficult-to-adhere-to plastic is encountered (i.e., polypropylenes or thermoplastic polyolefins (TPOs), a blend of elastomer and olefin). 

The first reactor-type thermoplastic polyolefin (R-TPO) was LLDPE/PP [Yamazaki and Eujimaki, 1970, 1972]. The three-component R-TPO s (PE with PP and EPR) soon followed [Strametz et al, 1975]. PE was also polymerized in the presence of active catalyst and an olefinic copolymer [Morita and Kashiwa, 1981]. Blending amorphous co-polyolefins with crystalline PO s (HDPE, LLDPE, PP), and a filler resulted in moldable blends, characterized by excellent sets of properties [Davis and Valaitis, 1993, 1994]. Blends of polycycloolefin (PCO) with a block copolymer (both polymerized in metallocene catalyzed process) and PE, were reported to show outstanding properties, viz. strength, modulus, heat resistance and toughness [Epple and Brekner, 1994]. 

Blends of EPDM rubbers with polypropylene in suitable ratios have been marketed as thermoplastic elastomers (TPE), also commercially known as thermoplastic polyolefin elastomers (TPO). These heterophasic polymers, characterized by thermoreversible interaction among the polymeric chains, belong to a broad family of olefinic alloys that can now be produced directly during the polymerization phase, unlike blended TPE and TPO, and various compositions (with various compounding additives) can be formulated which are primarily tailored to meet different requirements of most of car applications. The TPE-based synthetic leather and foam sheets are typical examples. 

Figure 9.2 A stamping identifying the plastic used in an automotive bumper. The resin used in the production of this Daimler-Chrysler part is identified as TEO (Olefinic Thermoplastic Elastomer), more commonly known as TPO (thermoplastic polyolefin) [126],...

From here on out, I will use the terms polyolefin or TPO to mean a thermoplastic polyolefin that is a blend (mechanical or so-called reactive types) of a plastic phase, primarily polypropylene, and an amorphous or elastomeric phase, consisting of truly ethylene-propylene copolymers or copolymers of ethylene with other a-olefins, such as butene or hexene. Considerations that must be addressed from both a commercial or practical point of view, as well as a theoretical or scientific point of view follow. 

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