Determination of PVC in Presence of Reactive Fillers

Abstract

Abstract PVC content in thermoplastic materials can be determined from the total chlorine or more specifically from organic chlorine content. Organic chlorine content can be determined by ASTM D 1551 using the described modifications. Presence of reactive fillers such as CaCO3 results in large negative errors. When reactive fillers are expected to be present, the quantity of PVC should be determined with methods measuring total chlorine or by TGA. TGA can be used successfully for the analysis of such samples. Plasticizers and PVC stabilizers are extracted before analysis to eliminate interfering or variable mass loss in PVC thermograms. This technique can also be used for the analysis of PVC/NBR mixtures. In unknown compounds, the technique should be used in conjunction with FTIR analysis to facilitate polymer identification and to rule out interference by other halogenated polymers. Excess of unreacted CaCO3 can be observed and the amount determined from thermograms. Remaining CaCO3 can be determined from mass loss due to elimination of CO2. If a cooling step is introduced before the atmosphere is switched from nitrogen to air, a clearer separation of residue oxidation and CO2 elimination are obtained. On reheating, residue oxidation then takes place between 450 and 500°C, well separated from CO2 elimination at about 700°C. Variation of thermograms using PVC obtained by different polymerization procedures needs to be further investigated. Structural differences and thermal stability of PVC samples made by emulsion, suspension, and bulk polymerization have been examined by various techniques, but no thermogravimetric data are given.