Premium
New Perspective on Heat Deflection Temperature of Glassy Polycarbonate
Author(s) -
Li Xiangyang,
Mason James
Publication year - 2009
Publication title -
macromolecular materials and engineering
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.913
H-Index - 96
eISSN - 1439-2054
pISSN - 1438-7492
DOI - 10.1002/mame.200800334
Subject(s) - creep , materials science , vicat softening point , polycarbonate , amorphous solid , deflection (physics) , residual stress , stress relaxation , composite material , thermodynamics , softening point , optics , crystallography , chemistry , physics
For polycarbonate, the HDT values can vary over 20 °C. Many factors affect the test results. Among these, thermal dilatation and creep were discussed in detail. Quantitatively, the contribution from thermal dilatation to HDT values varies little with physical aging time, but the contribution from creep to HDT values changes greatly. When creep is insignificant, the HDT values can be calculated from an elastic beam deflection equation and are close to the T g values. This paper qualitatively disputes the claims of the effect of residual stress on HDT values. It is argued that changes in residual stress level and HDT values with physical aging are symptoms of the structural relaxation, but no causal effect exists between these two symptoms. As a test method for amorphous polymers, Vicat or T g can provide more reliable results than HDT.