Polyolefin polyethylene comonomers

Eaves (92) distinguished between polyolefin plastomers (POP) with density >910 kg m and polyolefin (POE) elastomers with densities <910 kg m-3. The density of a polyethylene at 20 °C is a linear function of the crystallinity, with limiting values of 854 kg m 2 for zero crystallinity and 1000 kg m for 100% crystallinity. The polyolefin elastomer foams compete with EVA copolymer foams. Metallocene chemistry also allows the production of copolymers with a larger comonomer content in the high molecular weight part than in the low molecular weight part this... 

Since the discovery of olefin polymerization using the Ziegler-Natta eatalyst, polyolefin has become one of the most important polymers produeed industrially. In particular, polyethylene, polypropylene and ethylene-propylene copolymers have been widely used as commercial products. High resolution solution NMR has become the most powerful analytieal method used to investigate the microstructures of these polymers. It is well known that the tacticity and comonomer sequence distribution are important factors for determining the mechanical properties of these copolymers. Furthermore, information on polymer microstructures from the analysis of solution NMR has added to an understanding of the mechanism of polymerization. 

In the 1990s, a new family of polyethylenes based on metallocene catalysts emerged. These catalysts offered significant new ability to tailor the properties of linear polyethylenes and other polyolefins. In particular, they have the ability to provide more uniform incorporation of comonomers. 

We have seen the development of polyethylene, from low molecular weight polymers first mentioned by name in the literature in 1869, to the first reported solid polymers of linear polyethylene by Prof. Marvel in 1930 then the unintentional synthesis and chance observation of 0.4 g of solid polyethylene in March 1933 by ICI (prepared under high pressure, later described as LDPE) the onset of catalyst technology in the industry, from the simultaneous discoveries of transition metal catalysts a few decades later, that created the HOPE industry the development of LLDPE copolymers and the discovery in 1979 of metallocene catalysts for polyolefin polymerization - all of which are now part of the mainstream polyethylene industry. Post-metaUocene catalysts offer the promise of branching without high pressure or comonomers the potential to incorporate polar groups without high pressure, and to control this copolymer microstructure. 

Iron catalysts [20-24] have been used to make polyethylene-clay nanocomposites where the polyethylene had very broad molecular weight distribution (MWD). Ziegler-Natta [25, 26], organo-chromium (Phillips) [27], and bis(imino)pyridine iron and cobalt catalysts [28] have also been used to make polyolefin-late transition metal catalysts [29, 30], capable of producing highly branched polyethylene from only ethylene and of promoting the copolymerization of ethylene with polar comonomers, have also been apphed to make polyolefin-clay nanocomposites. 

The polyolefins are those polymers based only on carbon and hydrogen, originating from monomers containing a double bond in the 1-position, sometimes called a-olefins. Principally, these include polyethylene, polypropylene, copolymers of polyethylene containing various comonomers such as 1-butene, 1-hexene, and 1-octene, ethylene-propylene monomer (EPM), and ethylene-propylene-diene-monomer (EPDM). All of these are plastics except EPM and EPDM, which are elastomers. 

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