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Shrinkage and retractive force of drawn isotactic polypropylene during heating
Author(s) -
De Candia F.,
Romano G.,
Vittoria V.,
Peterlin A.
Publication year - 1985
Publication title -
journal of applied polymer science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.575
H-Index - 166
eISSN - 1097-4628
pISSN - 0021-8995
DOI - 10.1002/app.1985.070301017
Subject(s) - materials science , composite material , limiting , maximum temperature , shrinkage , drop (telecommunication) , melting temperature , tacticity , thermal , melting point , thermodynamics , physics , polymer , computer science , engineering , polymerization , mechanical engineering , telecommunications
The semi‐crystalline isotactic polypropylene was drawn to λ = 6,7,8,9,11 and the drawn samples heated to temperatures between 40 and 160°C. The shrinkage of the sample with λ = 7 and 11 was measured as function of time and temperature. The effect of shrinkage is higher with the smaller draw ratio as if the drawing increased the thermal stability of the sample. With fixed ends the drawn samples were heated at a constant rate and the retractive stress observed. It increases with λ and the heating rate. At the same drawing ratio λ, the curves of the retractive stress show a maximum and subsequently drop to a substantially smaller value that increases with the draw ratio and the distance of the highest temperature of the heating from the melting point of the sample. The cooling curve of the first run almost coincides with the heating and cooling curve of the next runs if one does not surpass the maximum temperature of heating of the first run. The time dependence of the retractive stress after an inital maximum decays more rapidly to the limiting value σ ∞ ( T ) the higher the temperature of the experiment. The limiting value σ ∞ ( T ) rapidly decreases with T and increases with λ.