Polyethylene high molecular weight linear

High molecular weight linear polyethylene was obtained from ethylene polymerization by TiCl2 (146) this polymer contained only vinyl-type double bonds (less than 0.1 per 1000 carbon atoms). 

Figure 8 Plot of low frequency Raman spectra of a high molecular weight linear polyethylene that was initially quenched at —70°C as a function of temperature. Spectra obtained at (a) room temperature, (b) 57°C, (c) 87°C and (d) 147°C. Reprinted with permission from Ref. [102]. Copyright 1986 American Chemical Society.

The 1 hour treatment at 160°C will be more severe than necessary for some samples and Inadquate for others. We have observed that storage at 160°C for as much as a day may be required to remove detectable aggregates in solutions of very high molecular weight linear polyethylene samples. In any event, the appropriate duration of such treatments can be assessed by the method discrlbed here. That is to say, the solution history should be adjusted so that direct measurements of by LALLS (without the SEC columns) yields clean recorder traces (as in Figure 1) and second vlrlal coefficients which are in accord with Kok-Rudin predictions of such values for the measured... 

Proton NMR relaxation parameters have also been determined for polyethylene ( ) and polyethylene oxide (39) in the melting region. The apparent contradiction between the proton spin-lattice relaxation parameter for a high molecular weight linear polyethylene sample at its melting point, with the relaxation measurements, has previously been pointed out. (17) This discrepancy is still maintained with the more detailed results reported here for both types of polyethylene. For the proton relaxation a small, but distinct, discontinuity is reported at the melting teirperature. (38)... 

The influence of solvent was especially shown by using nickel-containing catalysts based on nickelphosphine complexes. These compounds dissolved in toluene without cocatalysts, oligomerize ethylene to linear a-olefins. Using a suspension in H-hexane, high-molecular-weight linear polyethylene is formed (183). 

Within the family of polyolefins there are many individual families that include low density polyethylenes, linear low density polyethylenes, very low polyethylenes, ultra low polyethylenes, high molecular weight polyethylenes, ultra high molecular weight polyethylenes, polyethylene terephthalates, ethylene-vinyl acetate polyethylenes, chlorinated polyethylenes, crosslinked polyethylenes, polypropylenes, polybutylenes, polyisobutylene, ionomers, polymethylpentene, thermoplastic polyolefin elastomers (polyolefin elastomers, TP), and many others. 

Complexes 3-7 oligomerize ethylene in toluene at 80 °C and 5 MPa to 99 % linear olefins with 98 % a-olefins. Complex 4 reaches an activity of 6000 mol ethylene per mol of catalyst [43]. Applying the reaction in suspension in n-hex-ane, high-molecular-weight linear polyethylene is obtained. 

A derivative of the Ziegler ethylene polymerization process (Alfene process producing 2-linear olefins), this technique is used to produce high molecular weight linear alcohols with an even number of carbon atoms (C4 to C2 -). It was developed by Continental Oil Company, and employs the growth reaction of polyethylene from triethytahinrimim. The rupture of the chain is caused by oxidation of the product ... 

Figure 1.1 The molecular weight-melting temperature relationship for the alkane series. An asymptotic value of about 145°C is reached for very high molecular weight linear polyethylenes.

An intense P transition is universally observed for all branched polyethylenes (short and long chains). However, this transition is found only for a very high molecular weight linear polyethylene. The data plotted in Fig. 4.48 show that, in contrast to the a transition, the temperature of the P transition does not depend on the crystallite thickness. The location of the P transition, Tp, depends on the chemical nature and concentration of the co-unit. Thus, each copolymer has its own p transition [244]. 

S. K. Bhateja, and E. H. Andrews. Effect of high-energy radiation on the uniaxial tensile creep behaviour of ultra-high molecular weight linear polyethylene. Polymer 24 (2), 160-166 (1983). 

Increased orientation Increase Greatest effect on high molecular weight linear polyethylene. 

Fig. 9.5 Plot of V(f)/ VlCO) against log time for an unfractionated very high molecular weight linear polyethylene at indicated crystallization temperatures. Insert at right demonstrates a common superposed isotherm.(18)...

Since 1900 other methods have been devised for producing polymethylene , including the use of boron trifluoride-diethyl ether catalysts at 0°C. Some of these methods give unbranched linear polymers, often of very high molecular weight, which are useful for comparing commercial polyethylenes which have molecules that are branched to varying extents. 

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