Polyethylene number average molecular weight

Fig. 10.41 Plot of reciprocal half-time as a function of crystallization temperature for sol fraction of cross-linked linear polyethylene. Number average molecular weight, Afni o original non-cross-linked polymer 7106 7077 6422 A 4561 A 5634 o 4150. (From Phillips and Lambert (95))...

One thousand kilograms of 99.6% pure ethylene is polymerized in a heterogeneous process to 850 kg of polyethylene (HDPE) of 80,000 number average molecular weight. Ethylene (99%) totaling 148 kg is recovered. 

Commercial polyethylenes also vary in their molecular weight distribution (MWD). Whilst for some purposes a full description of the distribution is required, the ratio of weight average molecular weight to number average molecular weight provides a useful parameter. Its main deficiency is... 

The most common commercial grades of polyethylene have number average molecular weights of the order of 10000—40000 (with corresponding values in the range 50 000-300 000). There are, however, a number of special purpose... 

The model chosen to describe the degradation of polyethylene was random chain scission. Lenz (3,) in his section on degradation reactions of polymers cites work which supports the contention that polyethylene does thermally degrade in a random chain scission manner as opposed to depolymerization. For this model a statistical treatment has been developed by Montroll and Simha (). The extent of reaction may be related to the number average molecular weight by ... 

The identification of both short chain and long chain branches in polyethylene at concentrations of 1 per 10,000 carbon atoms has become feasible with the availability of improved probes and improved computer hardware/ software capabilities. Reviewed in this chapter are the methods and computations as well as the basic requirements for sound quantitative analyses namely, correct choice of solvent, a consideration of concentration effect on line widths and satisfying nuclear Overhauser effects and spin lattice relaxation time requirements. Finally, the NMR generated structural information is put to use in correlations with polyethylene physical properties and measurements of number average molecular weight. 

The number average molecular weight of the polyethylene corresponds to a p value of 0.021. Table VIII compares the / values of ethyl-... 

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