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Quantitative Thermomechanical Analysis of Polyvinylchloride Compounds

Peter Hedvig ; Research Institute for Plastics, Budapest 1950, Hungary

Puni tekst: engleski pdf 11.548 Kb

str. 21-51

preuzimanja: 325



Unplasticized, plasticized PVC-compounds and PVC-plasticizer-
ethylene vinylacetate copolymer blends were studied by a new differential thermomechanical technique measuring thermally stimulated and isothermal creep, recovery or stress relaxation
simultaneously with an unloaded reference sample. The possibilities
of quantitative interpretation of such differential thermomechanical
curves ins ide and outside the physical age ing temperature-range is discussed. By the differential technique creep was separated from thermal dilatation and recovery; by a pulsed-load technique recoverable creep was separated from irreversible flow. By these methods plasticized PVC-compounds were found to exhibit multiple glass transition which could not be detected by the conventional techniques, such as differential scanning calorimetry, dynamic mechanical analysis or nuclear magnetic resonance. By using the Kohlrausch reponse function and the effective (reduced) time method, thermomechanical »temperature-domain« curves could be transformed into the time-domain ones which, in turn, could be transformed into frequency-domain spectra. In order to do this, besides thermomechanical curves, some isotherms were also needed. In the physical ageing temperature-range thermal stimulation was overwhelmed by the effect of the storageand elapsed time, which would shift the distribution to long er times. In this range the pulsed-load technique with stepwise temperature control was found useful by considering that temperature steps would erase previous history-effects, partly or totally. The differential techniques was also used to study multiple glass-transitions in blends of PVC di-iso-octyl phthalate and ethylene vinylacetate copolymer.

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