Thermal Stability of Nanosilica-Modified Poly(vinyl chloride)

The thermal stability of PVC with 1 wt % of spherical porous nanosilica, prepared by roll milling at processing time varied from 1 to 20 min, was investigated by means of visual color changes, Congo red, and thermogravimetric tests (TGA and DTG), as a function of rolling time and composition of PVC matrix. The melt flow rate (MFR) measurements were realized to identify the degradation-induced changes of processing properties. A high level of gelation of the PVC matrix for all samples was verified by DSC (differential scanning calorimetry). It was found that the addition of porous nanosilica to absorb a certain volume of HCl, produced by dehydrochlorination reaction, leads to an improvement of thermal stability, an effect observed in a form of minor color changes of the samples, lower evolution of gas hydrogen chloride, and slight changes of the MFR value. It was demonstrated that the TGA measurements are not sufficiently sensible to detect the degradation of PVC at the processing conditions, i.e., at the temperature equal to 220 degrees C and below this temperature.

Automated summary

The study investigated the thermal stability of PVC with 1 wt % of spherical porous nanosilica prepared by roll milling at various processing times. The addition of porous nanosilica was found to improve thermal stability by absorbing HCl gas produced during dehydrochlorination reaction, resulting in minor color changes and lower evolution of hydrogen chloride gas. The results showed that TGA measurements were not sensitive enough to detect PVC degradation at processing conditions below 220 degrees C.