Polypropylene, polyolefin elastomers

Lee, S. H., Kontopoulou, M., and Park, C. B. 2010. Effect of nanosilica on the co-continuous morphology of polypropylene/polyolefin elastomer blends. Polymer 51 1147-1155. 

In the early stages of development of polypropylene rubbers, particularly butyl rubber, were used to reduce the brittleness of polypropylene. Their use declined for some years with the development of the polypropylene copolymers but interest was greatly renewed in the 1970s. This interest has been centred largely around the ethylene-propylene rubbers which are reasonably compatible in all proportions with polypropylene. At first the main interest was with blends in which the rubber content exceeded 50% of the blend and such materials have been designated as thermoplastic polyolefin elastomers (discussed in Section 11.9.1). There is also increasing interest in compounds with less than 50% rubber, often referred to as elastomer-modified thermoplastics. It is of interest to note... 

If polypropylene is too hard for the purpose envisaged, then the user should consider, progressively, polyethylene, ethylene-vinyl acetate and plasticised PVC. If more rubberiness is required, then a vulcanising rubber such as natural rubber or SBR or a thermoplastic polyolefin elastomer may be considered. If the material requires to be rubbery and oil and/or heat resistant, vulcanising rubbers such as the polychloroprenes, nitrile rubbers, acrylic rubbers or hydrin rubbers or a thermoplastic elastomer such as a thermoplastic polyester elastomer, thermoplastic polyurethane elastomer or thermoplastic polyamide elastomer may be considered. Where it is important that the elastomer remain rubbery at very low temperatures, then NR, SBR, BR or TPO rubbers may be considered where oil resistance is not a consideration. If, however, oil resistance is important, a polypropylene oxide or hydrin rubber may be preferred. Where a wide temperature service range is paramount, a silicone rubber may be indicated. The selection of rubbery materials has been dealt with by the author elsewhere. ... 

RECYCLING TECHNOLOGY FOR LAMINATES COMPOSED OF THERMOPLASTIC POLYOLEFIN ELASTOMER AND CROSSLINKED POLYPROPYLENE FOAM... 

Within the family of polyolefins there are many individual families that include low density polyethylenes, linear low density polyethylenes, very low polyethylenes, ultra low polyethylenes, high molecular weight polyethylenes, ultra high molecular weight polyethylenes, polyethylene terephthalates, ethylene-vinyl acetate polyethylenes, chlorinated polyethylenes, crosslinked polyethylenes, polypropylenes, polybutylenes, polyisobutylene, ionomers, polymethylpentene, thermoplastic polyolefin elastomers (polyolefin elastomers, TP), and many others. 

The choice of date range is arbitrary. The number of journal articles for each year was obtained from a search of electronic version of English-based polymer and polymer-related journals using the keywords polyolefin and blends. Within polyolefin keyword, the subkeywords used in the search were polyethylene (PE, LLDPE, LDPE, HDPE, UHMWPE, PE, etc.), polypropylene (PP, iPP, sPP, aPP, etc.), polybutene-1, poly-4-methylpentene-l, ethylene-diene monomer, ethylene-propylene-diene terpolymer, ethylene propylene rubber, thermoplastic olefins, natural rubber (NR), polybutadiene, polyisobutylene (PIB), polyisoprene, and polyolefin elastomer. For the polyolefin blends patent search, polymer indexing codes and manual codes were used to search for the patents in Derwent World Patent Index based on the above keywords listed in the search strategy. 

Their potential to polymerize prochiral olefins, such as propylene, to give stereospecific polymers (isotactic. syndiotactic. hemitactic polypropylene). This variety opens the door to polyolefin elastomers. 

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. 

Polypropylene (PP) in various forms (filled, unfilled, reinforced, rubber blended) finds the greatest usage of all automotive plastics. Its consumption is likely to accelerate as a result of new laws requiring recyclability, and because of the weight and cost reductions it offers. New fabrication techniques may also contribute to growth. For example, the monomaterial sandwich construction techniques developed by fabricators yield rugged and lightweight PP-based instrument and door panels. These parts consist of a sandwich of reinforced or neat PP substrate, a cross-linked PP foam, and a thermoplastic polyolefin elastomer (TPO) cover. 

The flame-retarding of HDPE and PP is not so complex. 4.25 phr. of Saytex BN 451 and 2 phr. of antimony trioxide yield the rating V-2 for polypropylene. 6 per cent of octabromodiphenyl oxide and 3.5 per cent of antimony trioxide in 90.5 per cent of HDPE is rated B2 according to DIN 4102 (cf. Section 3.2.1) while the flammability of a compound with 9 per cent of decabromodiphenyl oxide and 4 per cent of antimony trioxide to 87 per cent of HDPE is rated B1. For reaching the classification V-0, a rather high portion of flame-retardants should be admixed, for example 30 phr of decabromodiphenyl oxide and/or BT 93 is recommended with 10 phr. of antimony trioxide to polypropylene. Masterbatches with these flame-retardants facilitate processing (cf. Table 5.15). The same systems are also used for polyolefin elastomers (such as EPDM) . 

The compatibilizer as such may be compatible with the clay surfaces and hence easily intercalates into the interlayer spacing of the clay platelets and separates the clay platelets, and with bulk polymer it leads to the formation of well-dispersed nanocomposites. The compatibilizer widely used for polypropylene (PP) is maleic anhydride grafted PP (PP-g-MA) [15-16], Other compatibilizers used are diethyl maleate (DEM-g-PP) and polyolefin elastomer grafted maleic anhydride (POE-g-MA),... 

Austin, J. R. and Kontopoulou, M. 2006. Effect of organoclay content on the rheology, morphology, and physical properties of polyolefin elastomers and their blends with polypropylene. Polymer Engineering and Science 46 1491-1501. 

Generally, the TPOs are produced by extruder compounding processes in which the polypropylene resin is blended with an ethylene copolymer mbber (EPR or other polyolefin elastomers or POEs), along with a desired level of reinforcing fillers. The components are blended together at 210-270 °C imder high shear using a twin-screw extmder or a continuous mixer. 

Thermoplastic polyolefin (TPO) blends of metallocene-based polyolefin elastomers (POE) with polypropylenes have gained commercial significance because of the improved melt flow and toughness compared to the conventional TPOs based oti EPR or EPDM blends made with high melt-flow PP (Toensmeier 1994). in comparative tests with 70/30 PP/elastomer blends, the blends with POE maintained ductile behavior at —29 °C even with high melt flow index PP (MFl = 35), while the corresponding EPR-based blends were brittle with PP of MFl = 20. In addition, they showed improved knit-line strengths. 

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. 

These trends are illustrated by DuPont Dow Elastomers range of Engage polyolefin elastomers, intended as impact modifiers for polypropylene in automotive bumpers and fascias. They combine stiffness with ductility, and are claimed to give very good low temperature impact strength. Engage 8842 is said to have a particularly wide range of applications. 

A hot melt adhesive composition made from polypropylene copolymer or polypropylene impact copolymer, a polyolefin elastomer, a low density polyethylene, a tackilying resin, a plasticizer, and a nucleating agent The 0.2 to 1 wt% of nucleating agent is... 

Uniroyal, Inc. (see W. K. Fischer), Thermoplastic Blend of Partially Cured Monoolefin Copolymer Rubber and Polyolefin Plastic, Br. Pat. 1,384,261 (1975). Partially cured EPDM or EPM blended with polyethylene or polypropylene. Thermoplastic elastomers. Sequential partial cure and blending. 

SFM studies of low crystallinity thermoplastic polyolefin elastomers based on polyethylene-alkene copolymers or stereoblock polypropylenes highlighted the importance of the crystalline regions as physical cross-links in these systems (173, 174). Even though crystallinity was very low in these materials, SFM provided sufficient contrast to interrogate the size and distribution of crystallites in the as-prepared and deformed materials (175). As will be discussed in the section under Polymer Crystallization, the crystallization process in such materials was also imaged in real time (176). 

Polymeric hindered amine light stabilizer is excellent for protection against ultraviolet degradation. Applications include polyolefins (polypropylene, polyethylene), olefin copolymers such as EVA as well as blends of polypropylene with elastomers. Also effective in polyacetals, polyamides, polyurethanes, flexible and rigid PVC, and PVC blends. 

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