【国外标准】 Standard Practice for Determination of Contamination in Recycled Poly(Ethylene Terephthalate) (PET) Flakes and Chips Using a Plaque Test

5.1 Presence of paper, metal, or incompatible polymer contamination in poly(ethylene terephthalate) renders the recycled polymer unfit for use in secondary product manufacturing operations. This procedure is useful for identifying different types of contamination in recycled PET flakes.1.1 This practice covers an indication of the quality of recycled transparent poly(ethylene terephthalate) by examination of a wafer or plaque formed by melting a representative sample and quenching it to prevent crystallization.1.2 Specific contaminants and impurities such as aluminum particles, dirt particles, paper, and fibers are identified in the transparent wafer. This method is only limited to contamination observable through visual methods. If there are low levels (0–200 ppm) of certain types of contamination, which are transparent and partially/wholly miscible with PET, they will not be apparent through this method.1.3 The overall color of the plaque is indicative of oxidizable contaminants such as ethylene-vinyl acetate (EVA) glue residue and the number of bubbles present in the plaque gives an indication of the moisture content of the sample.1.4 Units—The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use. Specific precautionary statements are given in Section 8.NOTE 1: There is no known ISO equivalent to this standard.1.6 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.