Using post-industrial resin (PIR), commonly referred to as regrind, is a common practice in injection molding to reduce material costs, minimize scrap, and improve material efficiency. Many injection molders routinely blend regrind with virgin resin to optimize sustainability and production economics.

However, as regrind is reprocessed multiple times, polymer degradation can occur due to repeated heat history and shear. This can impact key performance characteristics such as impact strength, melt flow consistency, color stability, and overall part-to-part repeatability, especially at higher regrind usage levels.

Key Challenges When Using Regrind in Injection Molding

• Maintaining consistent material properties across multiple processing cycles
• Managing color variation between regrind streams
• Controlling odors associated with reprocessed materials
• Balancing regrind utilization with part quality requirements

Colortech's Solutions for Managing Regrind in Injection Molding

Antioxidant Additives to Protect Polymer Performance

Antioxidant additives help reduce further polymer degradation during reprocessing, improving retention of mechanical properties and maintaining more stable melt flow behavior when using higher levels of regrind.

Color Masterbatch for Consistent Appearance with Mixed Regrind Streams

When combining multiple regrind sources, color variation can become difficult to control. Color masterbatch helps stabilize the appearance of the final part and reduce batch-to-batch variation in injection-molded products.

Odor Absorbers for Reprocessed Injection Molding Materials

Odor issues can arise when reprocessing post-industrial resin depending on prior application history. Odor absorbers help mitigate residual smells and improve end-product acceptability in consumer-facing applications.

Making Regrind Work for Your Process

While post-industrial regrind offers significant cost and sustainability benefits, successfully incorporating it into an injection molding process requires careful attention to material performance, color consistency, and odor management. By selecting the right additive and color solutions, injection molders can increase regrind utilization while maintaining part quality and process stability. Colortech works with customers to develop customized solutions that help maximize the value of regrind without compromising performance