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Dynamic mechanical properties determined with a torsion pendulum were used to ascertain the glass transition temperature Tg of poly‐ε‐caprolactone. By measurements on compatible blends of poly‐ε‐caprolactone and poly(vinyl chloride), the Tg of amorphous poly‐ε‐caprolactone was shown to be 202°K at about 1 cps. This is 16°K lower than the Tg of annealed, crystalline polymer. The blend transition data were well fitted by both the Fox and the Gordon‐Taylor expressions. The Fox expression was also used to describe the decrease from 233°K of the secondary low‐temperature relaxation due to poly(vinyl chloride) by assuming the low temperature relaxation of poly‐ε‐caprolactone, 138°K, was responsible for the decrease in the blends. The 138°K relaxation due to poly‐ε‐caprolactone was decreased when more than 50% poly(vinyl chloride) was present.

Glass transition temperatures of a very wide molecular-weight range of ethylene oxide polymers were measured by mechanical loss and by broadline NMR. Starting at about -95°C for ethylene glycol, the glass transition rises to a maximum of -17° for molecular weight 6000 and then drops off to -53° for polymers with molecular weights greater than 200 000. This unusual behavior is probably caused by the high crystallinity of the intermediate molecular-weight polymers.

SynopsisThe dynamic mechanical properties of thermoplastic urethane elastomers have been characterized for polymers composed of varying hard-segment concentrations and for two different molecular weight polyester diols as soft segments. The urethane polymers based on an 830 an polycaprolactone diol exhibited a progressive increase in glass transition temperature at increased levels of hard segments. In contrast, a similar series of polymers prepared with a 2100 an polycaprolactone diol as the soft segment maintained a relatively constant glass transition temperature. These differences are attributed to the relative degree of phase separation between the constitutive blocks of the copolymer. The polymers of both series possessed two lower-temperature, secondary relaxations,'which are ascribed to methylene sequence mobility within the polycaprolactone units and to possible disruption of interfacial associations between the hard-and soft-segment structures.