Thermal Stability of Nanosilica-Modified Poly(vinyl chloride)

Abstract

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 °C and below this temperature.

Modification of Laser Marking Ability and Properties of Polypropylene Using Silica Waste as a Filler

“…This effect was obtained mainly due to the presence of carbon in the powder filler, which commonly acts as a black dye. Similar observations in the case of aged PVC modified with nanosilica were recently published by Tomaszewska et al [16], wherein a gradual change in color (lowering the L* parameter value by ~50%) was achieved by extending the mixing of the sample melt (rolling time). In the tests carried out with waste silica (with the value of the L* parameter similar to the value obtained in the study by Tomaszewska et al), a more intense change in the L* parameter was obtained (change of 71% to the initial value).…”

“…The introduction of powder fillers to the thermoplastic matrix, in addition to enhancing mechanical properties, usually improves processing properties (shrinkage reduction), and increases thermal stability and thermal conductivity [15,16]. In addition, the consumption of plastics is reduced, which in some cases reduces the cost of the material.…”

Waste Eggshells as a Natural Filler for the Poly(Vinyl Chloride) Composites

“…The first step in the temperature range of 230–350 °C is associated with the dechlorination of the PVC macromolecules and the creation of conjugated polyene structures. The second step in the temperature range of 350–500 °C relates to another further thermal decomposition of the carbonaceous conjugated polyene sequences following the formation of residual chars [ 36 , 60 , 61 ]. When analyzing the TG thermograms of the PVC/ES composites, an additional stage of weight loss in the range of 650–770 °C related to biofiller presence was observed.…”

“…In industrial practice, this polymer is often subject to the modification of its properties, e.g., by using plasticizers, process agents, and various fillers, including waste fillers [ 33 , 34 ]. It is essential to obtain materials with improved thermal stability [ 35 , 36 ]. A commonly used additive in PVC-based plastics is calcium carbonate.…”

Effects of Organic Based Heat Stabilizer on Properties of Polyvinyl Chloride for Pipe Applications: A Comparative Study with Pb and CaZn Systems

“…In principle, the thermal degradation process of PVC involves three major steps: (1) the initiation of dehydrochlorination, (2) the elimination of hydrochloride (HCl) and simultaneous formation of conjugated double bonds, and (3) termination of the dehydrochlorination process. The exact mechanism of the thermal degradation of PVC is still controversial, but it is generally accepted that the thermal degradation process with the evolution of HCl via chain reaction called zipper elimination or unzipping process takes place [ 1 , 17 , 18 , 19 , 20 ]. Color change of the PVC from the thermal degradation process has been attributed to the formation of a conjugated polyene sequence of 5 to 25 double bonds.…”