AIR IMPURITIES IN THE PVC PLASTICS PROCESSING-INDUSTRY

Polyvinylchloride (PVC) is a common thermoplastic and one which often contains plasticizers. The most important plasticizer is di-2-ethylhexylphthalate (DEHP). Hygienic conditions in the PVC processing industry were surveyed by measuring the air concentrations of hydrogen chloride, DEHP and phthalic anhydride (PA) in different conditions of actual processing. Methods of sampling and analysis were developed and tested for these measurements. As measured at nine plants hydrogen chloride concentrations, which indicate the degradation of the polymer chain, ranged from less than 0.03 to 0.3 mg m-3. The mean concentrations of DEHP ranged from less than 0.02 to 0.5 mg m-3 and the highest single value was 1.1 mg m-3, which is about 20% of the current hygienic standard. Trace concentrations of PA-a sensitizer which is a degradation product of DEHP-ranged from less than 0.02 to 5-mu-g m-3 at six plants. The results show that the PVC polymer was efficiently stabilized in normal processing conditions (usually 150-200-degrees-C), but that plasticizers, which are not chemically bonded to the polymer, may volatilize more easily.