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 recyclable plastic materials are sourced from consumer product waste, carpeting, and 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.
Here are some common challenges with processing post-consumer plastics:
In recycling processing, multiple polymer types, fillers, and other ingredients are mixed in the production stream due to the application or sorting process. For that reason, compatibilization is necessary for compounders to achieve mechanical properties and desired specifications.
Impact strength, heat aging, gas-fading, and resistance to weatherability
Due to variability with the recycling of PCR, a compounder must be able to develop robust formulations that meet the broad specifications 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 offers a set of challenges different from processing virgin polymers. Therefore, compounders must optimize their processes and utilize additives to stabilize the melt-flow processing, reduce scrap, avoid degradation, and reduce plastic waste in the environment.
2. Post-Industrial Resins:
This recyclable material is made from recycling the scrap from production streams. PIRs are preferred over PCRs as they have a tighter spec range and are completely traceable; in other words, you precisely know the exact plastic resins. However, this is still more challenging to process than virgin materials. Therefore, in-house recycling is also a way to control the specs by reintroducing scrap into production streams at a certain percentage of the formulation.
Although recycling post-industrial plastics is more controlled, there are several challenges with processing:
When creating specific colors or shades using recycled plastics (excluding black), color shifts are significant and difficult to control.
Degradation of physical and mechanical properties
Recycled industrial plastics go through multiple heat cycles, from the initial creation of the material to several production cycles, including extrusion and pelletizing, to creating the new compound. Plastic additives, antioxidants, polymer modifiers, and chemical additives stabilize the recycling process. During recycling, an additional thermal cycle will require heat stability to prevent the degradation of physical, chemical, and mechanical properties in the manufactured plastic parts.
Other physical and mechanical properties
Compounders face other challenges depending on the desired specs of the end-use application, including protection against thermal degradation, gas fading, improved impact resistance, weatherability, stiffness, stabilization, mechanical properties, and strength.
Plastic Recycling Materials by Application: