Why Recycled Plastics Vary in Quality: A Practical Guide for Moulders

Where grading differences arise

Source sets the ceiling: post-industrial recyclate (PIR) is usually clean, single-polymer and close to virgin properties, while post-consumer recyclate (PCR) is complex and may carry multiple polymers, fillers, flame retardants and residual additives.

Pre-treatment sets the floor: sorting by floatation or near-infrared, washing, melt filtration mesh size and homogenising pelletising — skimping on any of these drags performance down.

Four checks before use

1. Melt flow comparison: large deviation from the virgin MFR causes filling and appearance problems.

2. Ash and contamination: a direct read on filtration and washing quality, with high ash usually accompanied by black specks and lower mechanical properties.

3. Odour: particularly for automotive interiors and appliances, residual odour in recyclate is hard to remove.

4. Lot consistency: ask for three consecutive lot reports rather than a single certificate.

Practical blending guidance

For non-critical internal parts without appearance requirements, PCR content can be high; for cosmetic or load-bearing parts keep it low or use PIR only.

Adjust hold pressure and temperature together when blending — recyclate viscosity is usually lower, so virgin parameters tend to produce sink marks.

For flame retardant, food contact or toy applications, do not blend on site; use certified dedicated grades.