Heat deflection characteristics of polypropylene and polypropylene/polyethylene binary systems

The effects of mould temperature and normal load on the heat deflection characteristics of PP were extensively investigated. The measurements of the heat deflection temperature (HDT) of PP suggested that the polymer appeared to have gone through some specific forms of morphological changes at mould temperature around 20-30 degreesC. This was evidenced by the increase in its melting point and degree of crystallinity determined from the DSC thermograms. It was further demonstrated that rate of deflection (R-DF) and initial deflection temperature (T-1) were important parameters to reflect the heat deflection behaviour of a polymer. On the study of PP/PE binary systems (PP/LDPE, PP/LLDPE and PP/HDPE), the validity of the additivity rule for the prediction of HDT of the blends,was demonstrated. RDF Of PP/LDPE and PP/LLDPE systems was found to be affected by the PP blend ratio in a strong exponential decaying manner, whereas RDF Of PP/HDPE system and the PP blend ratio had a more gentle exponential relationship. The measurements of T, of the blends revealed that T, appeared to be independent of the effect of the blend ratio. (C) 2003 Elsevier Science Ltd. All rights reserved.