Olefin branching copolymers Ethylene-propylene copolymer

Ethylene/propylene copolymers made with these nickel catalysts contain up to 6 mol % propylene. When the nickel catalysts were combined with supported chromium catalysts, branched polyethylene (5.0 methyl-ended branches per 1000 carbon atoms) was produced by the chromium copolymerizing ethylene with the a-olefins that were produced in situ by the nickel catalyst. Like the catalysts above, nickel catalysts with anionic ligands may themselves be supported on inorganic supports and polymeric supports. " ... 

Branching in Olefin Copolymers 10.2.1 Ethylene-propylene Copolymer... 

Copolymers of ethylene with a-olefins, such as the short-chain branched LLDPE (linear low-density polyethylene) impact materials or the EPD (ethylene-propylene-diene copolymer) rubbers represent major percentages of the total polyolefin production, due to their desirable mechanical properties. Solid-state MgCl2-supported Ziegler-Natta catalysts however, have unfavourable reactivity... 

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. 

The poly(alkylene oxide)s are linear or branched-chain polymers that contain ether linkages in their main polymer chain structure and are derived from monomers that are vicinal cyclic oxides, or epoxides, of aliphatic olefins, principally ethylene and propylene and, to a much lesser extent, butylene. These polyethers are commercially produced over a range of molecular weights from a few hundred to several million for use as functional materials and as intermediates. Lower polymers are liquids, increasing in viscosity with molecular weight. The high polymers can be thermoplastic. Solubilities range from hydrophilic water-soluble polymers that are principally derived from ethylene oxide, to hydrophobic, oil-soluble polymers of propylene oxide and butylene oxide. A wide variety of copolymers is produced, both random copolymers and block copolymers. The latter may be used for their surface-active characteristics. 

In the 1980s, the fluidized bed process was modified to produce a copolymer similar in density to polyethylene produced by the older, high-pressure process. Copolymerization of ethylene with 1-butene or other normal alpha olefins introduces short pendant chains that decrease crystallinity. In the plastics business, the terms high-density, or linear, polyethylene and LDPE (or branched polyethylene) are now supplemented by linear LDPE (LLDPE). While all the properties of the high-pressure polymer are not achieved by the newer material, the economics of the low-pressure, solvent-free process are such that LLDPE competes successfully in many of the markets once dominated by branched LDPE. The fluidized bed itself is only one of several gas-phase polyolefin processes. Stirred beds, arranged either horizontally or vertically, do not depend on gas velocity and are less sensitive to uniformity of gas flow. The stirred beds have been used primarily for polypropylene [19]. However, the fluidized bed has also been adapted for production of polypropylene and propylene copolymers. 

Hydrogenation pyrolysis has been applied to the determination of the composition of copolymers of a-olefins, the sequence of monomer units and the manner in which they are added (head-to-head and head-to-tail) [253]. Mikhailov et al. [251] used Py—GC to investigate the structure of low- and high-density polyethylenes and copolymers of ethylene with propylene. The pyrolysis products were hydrogenated. The method made it possible to examine alkanes up to Cjo, which facilitates the investigation of the polymer chain structure. The isoalkanes identified corresponded to the branched polyethylene structure. It has been established that the ethyl and butyl side-chains occur most frequently in polyethylenes. 

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