| Abstract: | This work is concerned with the change of viscoelastic properties of poly(vinyl chloride) (PVC) plastisol during heating. The system changes from a suspension of solid particles in a liquid medium to a swollen gel and further to a fused state as the temperature is raised. The Rheometrics mechanical spectrometer was used in the oscillatory mode at 0.1 Hz. The temperature of the sample was raised in a controlled manner to 195°C. During gelation, the viscosity increased rapidly about three decades. There was a similar increase of the elastic modulus. After reaching a maximum, both viscosity and elastic modulus decreased rapidly with the progress of fusion. The viscoelastic properties depended somewhat on the heating rate. At 170-195°C, it took a few minutes for the moduli to reach steady values. Continued heating, for several minutes at 195°C, did not change the moduli any further. The temperature range of the decomposition of a blowing agent in the plastisol foam formulation was determined. Over this temperature range, the viscoelastic properties change very rapidly. Quantitative estimates were made for the decrease of moduli during this period. |
