Olefin copolymers ethylene-propylene-elastomer

The category of elastomers includes a wide range of products, such as natural rubber (NR), styrene-butadiene rubber (SBR), styrene-butadiene-styrene copolymer (SBS known as thermoplastic rubber), styrene-isoprene-styrene copolymer (SIS), polyurethane rubber, polyether-polyester copolymer, olefinic copolymers, ethylene-propylene rubber (EPR) and so on (see also Table 3.16). 

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). 

The isoprene units in the copolymer impart the ability to crosslink the product. Polystyrene is far too rigid to be used as an elastomer but styrene copolymers with 1,3-butadiene (SBR rubber) are quite flexible and rubbery. Polyethylene is a crystalline plastic while ethylene-propylene copolymers and terpolymers of ethylene, propylene and diene (e.g., dicyclopentadiene, hexa-1,4-diene, 2-ethylidenenorborn-5-ene) are elastomers (EPR and EPDM rubbers). Nitrile or NBR rubber is a copolymer of acrylonitrile and 1,3-butadiene. Vinylidene fluoride-chlorotrifluoroethylene and olefin-acrylic ester copolymers and 1,3-butadiene-styrene-vinyl pyridine terpolymer are examples of specialty elastomers. 

Another contrarian, DSM in the Netherlands, had been a state-owned company before it became privatized, a process that began in 1989 and was completed in 1996. From its past it had inherited positions in fertilizers, industrial chemicals, and such intermediates as melamine and caprolactam as well as polyolefins, with access to basic olefins through its own crackers in Geleen, Netherlands. In 1997 DSM acquired the polyethylene and polypropylene operations of FIuls (VEBA) with the Gelsenkirchen site. The company had also diversified into elastomers, having purchased in the United States the Copolymer Rubber and Chemical Corporation, which contributed to DSM s expansion into the fields of ethylene propylene, styrene butadiene, and nitrile rubbers. DSM is also a supplier of industrial resins and engineering... 

Applications of ethylene-propylene copolymers and terpolymers include automotive (the major use area), thermoplastic olefin elastomers, single-ply roofing, viscosity index improvers for lube oils, wire and cable insulation, hose, appliance parts, and polymer modification. 

Thermoplastic Olefin. These thermoplastic elastomers are primarily blends, or block or graft copolymers, of ethylene/propylene rubber with polypropylene. 

Low-temperature solution processes are state-of-the-art for the production of ethylene/propylene or ethylene/propylene/diene elastomers (EPDR or EPDM). A continuous stirred-tank reactor (CSTR) or a series of two or even more such reactors is used [2]. n-Hexane, n-heptane, or Ce, C7 fractions are the solvents. Catalyst, co-catalyst and other compounds are introduced with the solvent into the reactor. The monomers (ethylene, propylene) are injected as gases other olefins are introduced in liquid form. The polymerization process runs around 50 °C and at pressures up to 2 MPa. Downstream the catalyst/co-catalyst system is deactivated and their residues are dissolved in dilute acid or aqueous NaOH. The copolymer is stabilized with an antioxidant. Steam treatment removes the rest of the solvent and monomers, and agglomerates the product to crumbs. These crumbs are then dried and finished to bales or pellets. 

The addition copolymerization of norbornene-type monomers with a-olefins [21] forms the basis of EPDM (ethylene propylene diene monomer) technology. Incorporation of smaU amounts of DCPD or ethylidene norbornene (ENB) in olefinic vinyl addition polymers provides latent crosslink sites in EPDM elastomers. It is weU known in the hterature that incorporation of higher amounts of rigid, bulky multicychc olefins results in materials with higher TgS [22]. In fact, more recent work has concentrated on increasing the Tg of norbornene-type monomer/a-olefin copolymers [23]. The use of late transition metal catalysts to prepare such copolymers is reviewed in Section 4.3. 

It is claimed that styrene/butadiene diblock polymers bring about an improvement in the hardness, strength, and processability of polybutadiene elastomers (27), as well as an improvement in the ozone resistance of neoprene rubber (28). Styrene diblock polymers have also been made with isoprene, a-methyIstyrene, methyl methacrylate, vinylpyridine, and a-olefins. Block copolymers of ethylene, propylene, and other a-olefins with each other have been made as well. Heteroatom block copolymers based on styrene or other hydrocarbons and alkylene oxides, phenylene oxides, lactones, amides, imides, sulfides, or slloxanes have been prepared. 

The blends of EPDM terpolymers and isotactic PP with curing agents, such as peroxide, phenol resins, and sulfur, are termed as thermoplastic vulcanized elastomer (TPV) since the rubber domains are vulcanized. Polyolefin copolymers, such as random copolymer of propylene with ethylene, copolymers of other olefins, elastomeric PP, and elastomeric PE, are developed with recent advances of... 

Nowadays commercial mixtures of bitumens with uncured synthetic elastomers are produced, e.g. ethylene-propylene-diene terpolymers (EPDM), styrene-butadiene sequence copolymers (SBS), and ethylene-acrylic ester-acrylic acid terpolymers (AECM). Mixtures with some thermoplastics are also commercial products, e.g. polyethylene (PE), ethylene-propylene copolymers (EPM), alpha-olefinic copolymers, atactic polypropylene (aPP), and ethylene-vinyl acetate copolymers (EVA). 

Ziegler-Natta catalyst makes it possible to polymerize a-olefins into elastomers with controlled degree of crystallinity and cross-likability. The first EPR s were manufactured in 1960, 3 years later, the first EPDM. It is advantageous to produce block copolymers with PP being the rigid and PE the soft block. A direct sequential polymerization of propylene and ethylene-propylene mixture leads to the reactor blends (R-TPO) (Cecchin and Guglielmi 1990). 

As a consequence, before 1953, the only possible blends were those of LDPE with other polymers than PO or with elastomers (e.g., chlorosulfonated polyethylene rubber, CSR chlorinated butyl mbber, CBR ethylene/propylene/diene copolymers, EPR, EPDM thermoplastic olefinic elastomer TPE, TPO). However, in addition to the original autoclave polymerization, already in 1938, a tubular reactor was introduced and its product had different properties than that from the autoclave. Also varying the reaction condition affected the degree of short- and long-chain branching in LDPE thus, blending different LDPEs offered a way for optimizing the resin to specific applications. 

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