EPDM-polyolefin compositions

Excellent elastomeric NBR-nylon compositions have also been prepared by dynamic vulcanization during the melt-mixing of intimate blends of NBR with various nylons. In this case, the effect of curatives was complicated by the fact that some nitrile rubbers tend to self-cure at temperatures of mixing. Sulfur, phenolic, maleimide, or peroxide curatives can be used. The thermoplastic elastomeric compositions prepared by the dynamic vulcanization of nylon-NBR blends are highly resistant to hot oil. As in the case of the EPDM-polyolefin blends, increases in the amount of rubber in the composition reduce stiffness but increase resistance to permanent set. 

The use of TAG as a curing agent continues to grow for polyolefins and olefin copolymer plastics and mbbers. Examples include polyethylene (109), chlorosulfonated polyethylene (110), polypropylene (111), ethylene—vinyl acetate (112), ethylene—propylene copolymer (113), acrylonitrile copolymers (114), and methylstyrene polymers (115). In ethylene—propylene copolymer mbber compositions. TAG has been used for injection molding of fenders (116). Unsaturated elastomers, such as EPDM, cross link with TAG by hydrogen abstraction and addition to double bonds in the presence of peroxyketal catalysts (117) (see Elastol rs, synthetic). 

In order to improve properties and compatibility of PP/EPDM blends, ternary blends and composites are sometimes prepared from the PP/EPDM blends. For instance, Sanchez et al. (10) prepared ternary blends of PP, high density polyethylene and EPDM with several blending ratios and investigated the melt rheological behaviors. They discussed the effect of the shear rate on the viscosity and flow curve in terms of the exponent of low power for a non-Newtonian liquid. They showed that addition of an elastomer to the polyolefin blends changes the shape of the viscosity-composition curve, and they discussed it in terms of the possible morphology of the blend. Similar works have been also reported by Ha et al. (11,12). 

Like binary blends, PA6/(g-PE/g-EPDM) composites are two-phased. Irrespective of the components ratio, their individual effects of melting and crystallization in blends are shown on the DSC curve. The comparative analysis of structure-morphology features for ternary blends, PA6/(g-PE/g-EPDM), and binary blends indicated that g-EPDM added to PA6/g-PE affects crystallization of the polyolefin as well as polyamide components. The results of DSC on the two types of blends, PA6/ (g-LDPE/g-EPDM) and PA6/(g-HDPE/g-EPDM), show increased crystallinity in g-PE against a binary blend (108,109). This effect results, most likely, from easier crystallization of g-HDPE in the presence of g-EPDM owing to raised molecular mobility because of plasticization by the elastomeric phase. 

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. 

The dynamic vulcanization of blends of EPDM rubber with polyolefins (PP or PE) has been described (Coran and Patel, 1980). The rubber-plastic proportions and the extents of vulcanization were varied. In a few instances the rubber was first press-cured and then ground to various particle sizes. The ground rubber particles were then mixed with molten polypropylene. It was found that the ultimate properties (UE and UTS) varied inversely with rubber particle size. Since the smallest particle sizes of vulcanized rubber were obtained by dynamic vulcanization (not by grinding of cured rubber), the more durable compositions were obtained by dynamic vulcanization. 

While most of the literature cited above deals with composites containing nanoclays, nanosilica has also been used as a reinforcing agent, especially in polyolefin-based systems. Yang et al. [40] studied PP/EPDM/silica composites at various compositions, up to 40 wt%... 

Uses of Ethylene-Propylene Rubbers. EPDM and EPR vulcanizates are used in extruded profiles, cable insulation and jacketing, and roofing membranes. There are many automotive uses radiator hose, door and trunk seals, insulation, jacketing, and others. These elastomers are also used in applications such as window and architectural profiles, dock fenders, and washing-machine hoses. In short, their applications are extensive and diverse. Ethylene-propylene rubbers may be the most versatile of general-purpose rubbers. In addition, EP rubbers are added to polyolefin plastics as impact modifiers and as components of certain thermoplastic elastomer compositions (e.g., thermoplastic vulcanizates, which are discussed later in this chapter). 

Polyolefine blends are group of versatile materials, which properties can be tailored to specific applications already at the stage of compounding and further processing. Our previous papers on elastomer/plastomer blends were devoted to phenomenon of co crystallization in isotactic poly-propylene/ethylene-propylene-diene rubber (iPP/EPDM) [1] or surface segregation in low-density polyethylene/ethylene-propylene-diene rubber (LDPE/EPDM) [2, 3] systems. Composition and structure of the materials were related to their properties. Recently, we have described the influence... 

EPM [poly(ethylene-co-propylene)] and EPDM [poly(ethylene-co-propylene-co-5-ethylidene-2-norbomene)P can be metallocene catalyst polymerized. Metallocene catalyst technologies include (1) Insite, a constrained geometry group of catalysts used to produce AfiGnity polyolefin plastomers (POP), Elite PE, Nordel EPDM, and Engage polyolefin elastomers (POP) and (2) Exxpol ionic metallocene catalyst compositions used to produce Exact plastomer octene copolymers.2 Insite technology produces EPDM-based Nordel IP with property consistency and predictability (see Sec. 3.2.2). 

The elastomer-modified and filled polyolefin blend composition is as follows PPBC = 75-95, EPDM = 5-25, fillers = 2-10 phr, initiator, sulphur, and additives 0.01 to 0.1 phr each. STRUCTURE... 

Metallocene based polyolefins and polyolefin elastomeric compositions (POE) are often noted in supplier product literature to exhibit useful (and commercially viable) properties in blends with other polyolefins. Metallocene based polyethylene has also been noted to have the potential to replace the LLDPE/LDPE blends that are employed in a myriad of film applications [32 ]. PP/metaUocene ethylene-a-olefin copolymer blends for car interior applications have been noted [33 ]. MetaUocene-LLDPE blends with HDPE have been proposed for heavy-duty industrial grade bags as well as food packaging films [34]. Exxon-Mobil product literature notes the utility and ease of blending the metallocene LLDPE Exceed with other polyolefins. PP/POE blends showed similar mechanical properties and lower viscosity than the more conventional PP/EPDM blends [35]. Polyolefin plastomers (POP) imder the tradename Affinity GA were introduced by Dow as a polymer blend additive to improve the flow without loss of... 

Thermoplastic polyolefins (TPOs) are composite blends of semicrystalline polypropylene and ethylene propylene copolymer (EPR) or ethylene propylene diene monomer (EPDM), widely used in the automotive industry for the production of plastic car parts such as bumper fascia [1]. Polypropylene, which is the major component in such blends, is an inexpensive, easily proccessible polymer, although its poor mechanical properties necessitate the addition of a rubber-dispersed phase. The added rubber acts as an impact modifier by imparting improved ductility, crack resistance, and impact strength to the resulting TPO [1-4]. The cost-effectiveness, light weight, processability, and resilience of TPOs have made them increasingly viable alternatives to steel for bumpers and other car parts. 

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