Four-Step DMT Quality Control: Raw Material Screening, Decolorization, Precision Drying and COA Batch Management

TL;DR

• High-purity DMT quality depends on raw material screening, decolorization, drying control and batch testing. Learn how Dimethyl Terephthalate suppliers stabilize purity, color, acid value and COA delivery.
• Keywords: DMT quality control · high-purity DMT · Dimethyl Terephthalate purity · DMT COA report · DMT purity parameter >99.9%

"Garbage in, garbage out" — this iron law of engineering is particularly pronounced in waste plastic chemical recycling. Even with the most advanced methanolysis reactor, if raw material pre-treatment is inadequate, impurities, color, and foreign polymer content in the final product will exceed standards. ResourceCycle has developed a systematic waste PET pre-treatment technology system through years of industrial practice.

Step 1: Fine Sorting Waste plastics come from complex sources, containing various polymers such as PVC, PE, PP, and ABS. Chlorine in PVC corrodes equipment and contaminates products during methanolysis; PE/PP remains in solid form, increasing filtration burden. ResourceCycle uses near-infrared spectroscopy (NIR) automatic sorting systems combined with manual re-sorting to improve PET purity to above 97%, effectively reducing subsequent processing loads.

Step 2: Hot Alkali Washing Sorted waste PET flakes contain labels, adhesives, inks, food residues, and other contaminants. ResourceCycle uses a three-stage hot alkali washing process (70-85°C, NaOH concentration 1-2%) with mechanical stirring and high-pressure spraying, with removal rate exceeding 99%. Washing wastewater meets discharge standards after biochemical treatment, with COD removal rate ≥95%.

Step 3: Decolorization and Impurity Removal Dyes and carbon black additives in colored PET (blue, green bottles) are the main factors affecting R-DMT color. ResourceCycle has developed a proprietary activated carbon adsorption-filtration combined decolorization process, reducing the Hazen color of the methanolysis solution from 50+ to below 10, ensuring R-DMT products reach superior grade color specifications.

Step 4: Drying and Particle Size Control The moisture content of pre-treated PET fragments needs to be reduced to below 0.02%, otherwise moisture will undergo side reactions with ester bonds during methanolysis, reducing DMT yield. ResourceCycle uses dehumidifying dryers (dew point -40°C) for precise drying, controlling fragment particle size in the 5-15mm range to optimize mass transfer efficiency.

A sound pre-treatment system is the basic guarantee for high-quality R-DMT and one of the core competencies of ResourceCycle's product quality stability.