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Molecular weight and rheology of acetal copolymers

1965; Wiley; Volume: 81; Issue: 1 Linguagem: Inglês

10.1002/macp.1965.020810102

0025-116X

Herman L. Wagner, Kurt F. Wissbrun,

Scientific Measurement and Uncertainty Evaluation

Abstract Methods have been developed for the determination of weight and number average molecular weights of copolymers of trioxane containing oxyethylene units by light scattering and osmotic pressure measurements, respectively. The ratio M w /M n for a number of whole polymers is close to 2, in good agreement with the estimate of this ratio indirectly determined from the effect of chain transfer agent. Dilute solution and melt viscosity measurements have also been made. The melt viscosity at zero shear rate is approximately proportional to the 3.4 power of M w , both for polymers as polymerized and for a blend of two such polymers. The dependence of melt viscosity on shear rate can be fitted to the B UECHE ‐H ARDING emperical equation, but the values of M R calculated from this equation are much smaller than M w . For the blend M R is higher than that of either component. All of the results are in accord with those found for other polymers of about the same molecular weight distribution.