Ethylene-alkene copolymers

Ethylene can be copolymerized with alkene compounds or monomers containing polar functional groups, such as vinyl acetate and acrylic acid. Branched ethylene/ alkene copolymers are essentially the same as LDPE, since in commercial practice a certain amount of propylene or hexene is always added to aid in the control of molecular weight. 

Materials that typify thermoresponsive behavior are polyethylene—poly (ethylene glycol) copolymers that are used to functionalize the surfaces of polyethylene films (smart surfaces) (20). When the copolymer is immersed in water, the poly(ethylene glycol) functionaUties at the surfaces have solvation behavior similar to poly(ethylene glycol) itself. The abiUty to design a smart surface in these cases is based on the observed behavior of inverse temperature-dependent solubiUty of poly(alkene oxide)s in water. The behavior is used to produce surface-modified polymers that reversibly change their hydrophilicity and solvation with changes in temperatures. Similar behaviors have been observed as a function of changes in pH (21—24). 

In some very recent work by Karssenberg et al. [130], attempts have been made to improve the analytical ability of a technique like NMR spectroscopy to effectively predict the distribution of sequence lengths in polyethylene-alkene copolymers. They analyzed the entire [ C-NMR spectrum for homogeneous ethylene-propene copolymers. They used quantitative methods based on Markov statistics to obtain sequence length distributions as shown in Figure 22 [130]. The... 

With the sole exception of the random ethylene-propylene copolymers, for industrial applications heterogeneous catalysts have been used for alkene polymerisations. Ethylene-propylene statistical copolymerisation has been carried out using homogeneous vanadium-based catalysts [28]. 

Coordination polymerizations are often accompanied by isomerization. By means of the ternary catalytic system VC14, (acac)3Fe, and Et3Al, propene can yield crystalline polyethylene and the amorphous ethylene—propene copolymer. Many more such cases have, of course, been observed. Probably of greatest importance are those where a non-polymerizing 2-alkene is is-omerized to 1-alkene prior to propagation [355]. 

Random copolymers of ethylene and a-olefins (l-aUcenes) can be obtained with Ziegler-Natta catalysts, the most important being those of ethylene and 1-butene (LLDPE) and of ethylene and propylene (EPM or EPR and EPDM). Some reactivity ratios are listed in Table 9.5. Tha ratios vary with the nature and physical state of the catalyst and in most instances, r r2 is close to unity. However, all these values show that ethylene is much more reactive than higher alkenes. Copolymers produced using Ziegler-Natta catalysts usually have a wide range of compositions. This may be due to the presence of different active sites in the catalyst giving rise... 

Low density polyethylene is one of the most widely used packaging plastics. It is a member of the polyolefin family. Olefin, which means oil-forming, is an old synonym for alkene, and was, originally, the name given to ethylene. Alkenes are hydrocarbons containing carbon-carbon double bonds, such as ethylene and propylene. In the plastics industry, olefin is a common term that refers to the family of plastics based on ethylene and propylene. The term polyolefin strictly applies to polymers made of alkenes, whether homopolymers or copolymers. It includes the family of polyethylene, and the family of polypropylene. 

Figure 5.12 represents a compilation of melting temperature relations for rapidly crystallized ethylene copolymers with a set of 1-alkenes and norbomene as comonomers.(74-76,78) The melting temperatures of ethylene copolymers with bulkier side-group comonomers such as 1-decene, 4-methyl-1-pentene, cyclopen-tadiene and dicyclopentadiene follow the same curve as in Fig. 5.12.(78a) The plot clearly indicates that the melting points are independent of co-unit type under these crystallization conditions. Since observed melting temperatures of copolymers are known to depend on chain length the results shown have been limited to molecular weights of about 90000.(21) Studies of ethylene-octene copolymers with much higher comonomer content indicate a continuation of the curve shown in Fig. 5.12...

Fig. 28 Dependence of elution volume on average chemical composition of copolymers, (a) ethylene-1-butene copolymers, (b) propylene-1-alkene copolymers stationary phase Hypercarb mobile phase gradient 1-decanol/TCB temperature 160°C detector ELSD. (Reprinted fi om [161] and [162] with permission of Springer Science -l- Business Media and Elsevier Limited)...

The method involves measurements between 10 and 50 ppm. Figure 4.6 shows the NMR spectrum obtained for an ethylene - propylene copolymer. The method is valid for products containing 1-10 mol % of the second alkene-1 excluding products containing an extraordinary amount of blocky alkene-1. 

One of the unique features of the alkene/CO copolymer is the existence of multiple carbonyl groups in the main chain. Thus, versatile chemical transformations of the carbonyl groups were examined to provide new polymers (Scheme 16). The 1,4-diketone structure ethylene/CO copolymers can be transformed into pyrroles, thiophenes, and furans upon treatment with primary amines,phosphorus pentasulfide, and phosphorus pentoxide, respectively. ... 

Partitioning of branches in both polyethylene and isotactic polypropylene copolymers was also investigated by Hosoda et al. [41, 42]. Ethylene-alkene and propylene-alkene statistical copolymers were degraded by fuming nitric acid to selectively remove their amorphous phase. The degree of branch inclusion in the residual crystalline phase was then determined by solid-... 

The tensile properties of homogeneous ethylene-alkene statistical copolymers were further explored by Kennedy et al. [64]. It has been shown that the yield stress of a semicrystalline polymer is dependent on its crystal thickness [65, 66]. During uniaxial compression, the yield stress of polyethylene was observed to increase with crystal thickness up to 40 nm, whereas for thicker crystals it leveled off [66]. Since the crystal thickness in homogeneous copolymers decreases with increasing counit concentration, not surprisingly, an inverse correlation was also found between yield stress and counit content [64]. 

The extensive overall crystallization kinetics that have been reported for blends of linear polyethylene with random ethylene-1-alkene copolymers cannot be analyzed in a consistent manner.(40) Hence, they are not reported here. The reason is that the crystallization temperatures were expressed in terms of an arbitrarily defined undercooling, Tq — Tq, where To is the peak crystallization temperature obtained by dynamic cooling. 

Poly(esters) and rubbers Poly(alkenes) and rubbers Cellulosic polymers, ethylene-vinyl acetate copolymers, poly(alkenes), PVC, rubbers, and poly(styrene) Cellulosic polymers, poly(esters), poly(alkenes), polyurethanes, PVC, rubbers, and poly(styrene)... 

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