Recycling Methods by Resin Type:
Before we get to the recycling and compounding solutions, let's explore the sources of plastic waste, recyclability, and common challenges faced by the plastic recycling industry:
1. Post-Consumer Resins:
These are recyclable plastic materials that are sourced from consumer products waste, from carpeting waste to packaging plastics. PCR can be FDA compliant and commonly used on its own or in conjunction with virgin resins in various applications depending on the level of sorting and cleaning.
Common challenges faced with the processing of post-consumer plastics (PCR):
In recycling processing, multiple types of polymer types, fillers, and other ingredients are mixed in the production stream due to the application or sorting process. For that reason, compatibilization is a necessity for compounders to achieve the mechanical properties and desired specifications.
Since there is so much variability from lot to lot with the recycling of PCR base resin, a compounder must be able to respond instantly to the changing specs. Compounders must be able to respond to the changing specs by developing robust formulations that meet the broad specs of recycled plastic materials. This requires using a variety of plastic additives including, antioxidants, heat stabilizers, UV stabilizers, impact modifiers, processing aids, and more.
Maintaining the melt stability of recycled materials is more challenging than virgin polymers. Therefore, compounders optimize their processes and utilize additives to increase melt stability, reduce scrap, and limit plastic waste.
2. Post-Industrial Resins:
This type of recyclable material is made from recycling the scrap off production streams. PIRs are preferred over PCRs as they have a tighter spec range and are completely traceable; in other words, you know precisely the plastic types in the lot. However, this is still more challenging to process compared to virgin materials. Therefore, in-house recycling is also a way to control the specs by re-introducing scrap into production steams at a certain percentage of the formulation. Although recycling of post-industrial resins is more controlled, there are several challenges faced with the processing of PIRs:
When trying to create specific colors or shades using recycled plastics, excluding black, color shifts are significant and difficult to control.
Recycled industrial plastics have been through multiple heat cycles from the initial creation of the material, several production cycles, including extrusion and pelletizing, to the heat cycle for creating the new compound. Plastic additives, anti-oxidants, polymer modifiers, and chemical additives are used to improve stability throughout the recycling process. The recycling here will be an additional heat cycle that requires heat stability to prevent the deterioration of physical and mechanical properties in the produced plastic parts.
Compounders face other challenges depending on the desired specs of the end-use application, including melt stability, gas fading, impact resistance, weatherability, stiffness, and mechanical strength.
Plastic Recycling Materials by Application: