B-value L value and black point measurement of polyester slice PET--interpretation of national standard
Waste Plastics Recycling Equipment Department
Polyethylene terephthalate is the most important type of thermoplastic polyester, commonly known as polyester resin. It is obtained by transesterification of dimethyl terephthalate with ethylene glycol or esterification of terephthalic acid with ethylene glycol to synthesize bishydroxyethyl terephthalate, followed by polycondensation. Together with PBT is collectively referred to as thermoplastic polyester, or saturated polyester.
PET is divided into fiber grade polyester chips and non-fibrous polyester chips：
①Fiber-grade polyester is used in the manufacture of polyester staple fiber and polyester filament yarn. It is a raw material for processing fiber and related products of polyester fiber enterprises. Polyester is the largest variety of chemical fiber。
②Non-fibrous grade polyesters are also used in bottles, films, etc., and are widely used in the packaging industry, electronic appliances, medical and health, construction, automotive and other fields. Among them, packaging is the largest non-fiber application market for polyester, and it is also the fastest growing PET. field of。
GB17931-1993 (PET resin for bottles) specifies the test method, which describes the concepts of b value, L value, heterochromatic particles, and impurities. The technical requirements for PET are as follows：
b value ≤ 2 (for food packaging)
b value ≤ 3 (for non-food packaging)
L value ≥ 80
45/0 illumination, D65/10°, Hunter color system。
14189-2015, the b value is specified within the range of M4 ± 2-4, M4 is ≤ 8, the supply and demand are determined, and may not be arbitrarily changed. The range of 2-4 varies because the product itself has light, semi-dull or full extinction.
14190-08 regulations: D65/10 °, HunterLab color system. Quartz sample cup.
PTA as the upstream of PET, GB/T30921.7-2016 specifies that the measured b* value, 45/0 or 0/45 instrument, D65/10°, 400-700nm.
Not all colorimeter on the market can measure PET, and the characteristics and intersection of the standard are summarized. We recommend the most suitable PET PET colorimeter, LabScan XE.
The heterochromatic particles are less than one particle per 500 g, and the heterochromatic particles are defined as yellow or other color particles visible to the naked eye.
The appearance of powder particles requires ≤100 mg per kg.
SH/T1541-2016 test (plastic particle appearance test method) stipulates that: black particles are black and dark brown particles, black spots are black particles, black or dark brown spots are visible, color particles It is a particle of other colors than the color that black particles, black plaques, and resins should have.