Ethylene-Based Copolymers

Aliphatic Polyolefins other than Polyethylene, and Diene Rubbers Table 11.11 Comparison of major propenies of ethylene-based copolymers with polyethylene ... 

Vanadium catalysts have also been developed for polyethylene and ethylene-based copolymers, particularly ethylene-propylene-diene rubbers (EPDM). Homogeneous (soluble) vanadium catalysts produce relatively narrow molecular weight distribution polyethylene, whereas supported V catalysts give broad MWD. ... 

Figure 8.10 demonstrates that to a good approximation the reduced cell volume at F = 0 is constant for all copolymers, W = co/v 0.96. In Figures 8.11 and 8.12 the van der Waals parameters of Eq. (8.9) are plotted versus copolymer composition. One observes marked changes in the internal pressure parameter, AIV, with copolymer composition for EVOH and SAN. The ethylene-based copolymers have approximately the same value of the parameter B. For SAN, it does not change markedly in the range where styrene is in excess. Selected examples of the internal pressure parameter and characteristic specific volume B of copolymers are listed in Table 8.4 and... 

In contrast, HDPE is a translucent polymerized film with higher crystallinity than LDPE, and it provides a good barrier against gas and water. The mass density of HDPE ranges between 0.93 and 0.97 g/cm. HDPE has a high stiffness and hardness. Ethylene-based copolymers, such as ethylene acrylic acid and ethylene... 

An interior adhesive tie layer, preferably an ethylene based copolymer with grafted functional groups... 

An interesting case of polymer modification involves generation of functional groups on ethylene based copolymers [36]. Recently, a methodology has been described to convert the functional groups of ethylene-acrylate, -CH (COOR) - ethylene-acrylamide -CH (CONH2) - and ethylene-acrylonitrile -CH (CN) - copolymers into an ethylene acrylic acid -CH(COOH)- type copolymer using near critical water (at temperatures of 250 and 300 °C... 

A different approach of modeling ethylene-based copolymers is presented using acyclic diene metathesis (ADMEl) polymerization. Monomer s)mtiiesis dictates final polymer structure due to step-growth chemistry yielding only to olefin metathesis. While copolymerization of ethylene with a-olefins produces random distribution of alkyl branches along the PE backbone, polymerization of one kind of symmetric macromonomer produces PE with a perfectly known primary structure, as seen in Figure 1. 

The introduction of single-site catalyst technology has expanded the polyethylene product space to densities as low as about 0.86 g/cc with traditional comonomers such as 1-butene, 1-hexene and 1-octene. In addition, single-site catalysts have provided new ethylene-based copolymers with comonomers based on styrene and cyclic olefins such as norbomene. 

Although ethylene/1-olefin copolymers were well documented in the late 1950s with the discovery of the chromium-based Phillips catalyst and the titanimn-based Ziegler catalyst, it was the discovery of metallocene-based single-site catalysts and the constrained geometry catalyst system that significantly increased the various types of new ethylene-based copolymers that are available for commercial applications. These new catalysts created new products, applications and markets for the polyethylene industry. 

This limitation changed with the introduction of single-site catalysts. Two commercial examples of new ethylene-based copolymers with novel olefins are ethylene copolymers based on norbornene and styrene. 

Unlike typical ethylene-based copolymers available in the polyethylene industry, which are semicrystalline materials, the ethylene norbornene copolymers are amorphous thermoplastic materials with a high heat distortion temperature of up to 170°C. They have a glossy, crystal clear appearance, with a high modulus (stiff material) and low shrinkage, which are important in the processability of the molten material. The high modulus of this copolymer is not unexpected. The polymer backbone due to the... 

Real-Time Crystallization and Melting Study of Ethylene-Based Copolymers by SAXS, WAXD, and DSC Techniques... 

V aisman et al. [52] reported the effect of bromination of the surface of commercial UHMWPE fibres in order to polarise the surface of the fibres. This bromination process was shown to result in an increase in the degree of order of the transcrystalline zone when these fibres were combined with HDPE to produce a self-reinforced polymer model composite. While these pubUcations report the use of different types of PE to create self-reinforced polymer composites, UHMWPE fibres have also been combined with ethylene-based copolymers. Kazanci et al. [53, 54] reported the creation of commercial UHMWPE fibre-reinforced ethylene-butene copolymers. Filament wormd structiues were produced, with fibre volume fractions of 65%, with the suggestirm of a potential application for these materials in unspecified medical devices. 

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