塑料 高温下氯乙烯均聚物和共聚物及其制品释放氯化氢及其他酸性产物倾向的测定 第3部分：电导率测定法

This document specifies a method for the determination of the thermal stability at elevated temperature of compounds and products based on vinyl chloride homopolymers and copolymers (in the following text abbreviated as PVC) which undergo dehydrochlorination (the evolution of hydrogen chloride). This document is applicable to the characterization of PVC compounds and products, especially with regard to the effectiveness of their heat-stabilizing systems. It is applicable to coloured PVC compounds and products where a discolouration test under the action of heat can be unsatisfactory. This document is applicable to compounded PVC materials and products. It can be applicable to polymers in powder form under appropriate conditions, depending on the agreement between the interested parties. This document does not apply to PVC compounds in the form of dry blends, since such materials might not be sufficiently homogeneous. This document does not apply to PVC compounds and products which evolve other decomposition products, in addition to hydrogen chloride, at elevated temperatures that can affect the conductivity of water when they are absorbed into it. NOTE In this case, ISO 182-4 [2] provides the suitable method for the determination of chloride ion (Cl−) in the absorbing solution. This document can also be applied to other plastics materials which can evolve hydrogen chloride or other hydrogen halides when heated under the conditions prescribed by the relevant specifications, or as agreed upon between the interested parties.