Effect of fusion level on the Demattia flex crack resistance of calcium carbonate filed plasticized poly(vinyl chloride)

Abstract

PVC compounds of a vinyl leather formulation containing various amounts of calcium carbonate filler were reported. The influences of moulding time and temperature on PVC fusion level were determined. The correlation of fusion level to the behavior during Demattia flex cracking and crack growth testing was investigated. Optimum flex cracking resistance occurred at fusion levels of 53% and 63.5%, for unified and filled compounds, respectively, for the same PVC formulation . The slowed crack growth rate occurred in the fusion level of 53% for both compounds. The flex cracking behavior was characteristic of the thermal softening of PVC during gature. On flexing, the polymer temperature rose rapidly from 27°C to 50°C and then levelled off. The presence of filler led to accelerated failure due to voiding at the polymer-filler interface and stress concentration effects The heat build-up during flexing was not significantly different between the unfilled and filled polymer because of the lack of interfacial interaction between the filler particles and the polymer matrix.