regrinds

Regrind, in manufacturing, refers to material that has been ground or shredded after initial use or production and is reintroduced into the production process. It typically comes from process scrap such as sprues, runners, flashed parts, trim from sheet or film, and post-consumer scrap. Regrind is used across industries including plastics, rubber, wood composites, and certain metal powders, though the term is most often associated with plastics.

In plastics, regrind is usually supplied as pellets or powder and is blended with virgin resin to reduce material cost and waste. The suitability of regrind depends on polymer type, contamination level, moisture content, color, and molecular integrity. Engineering polymers may require lower regrind ratios or specialized cleaning; commodity polymers can tolerate higher regrind content.

Processing and handling involve sorting and cleaning sources, grinding or shredding, and screening to control particle size. For moisture-sensitive materials, washing and drying may be necessary before pelletizing to standard resin form. Quality control may monitor melt flow index, contaminant content, color, and bulk density to ensure compatibility with the target process.

Benefits and limitations include potential for significant material-cost reductions and waste reduction, balanced against impurities, property variability, and possible degradation from thermal history. Not all materials or products are suitable for high regrind content, and careful specification of acceptable impurity levels is important to maintain performance.

Economics and practice are driven by the product requirements, available equipment, and downstream processes. Effective use often requires drying, sorting, and monitoring to maintain consistent quality in the final product.