Skip to main content

Stabilization and Processing of Recycled Plastics

The demand for recycled plastics continues to grow, driven by the global regulatory and environmental pressure on plastic waste and single-use plastics. 

Plastics manufacturers and end users are creating sustainability stories and environmental initiatives to reduce plastic waste and the use of virgin resins and polymers. Across many industries and end markets, manufacturers and users of plastic materials are switching to recyclable plastic films and parts. These industries and end markets include automotive, packaging, and consumer plastic products.

Environmental concerns with the plastic waste


Why use recycled plastic?

Plastic waste and chemical pollutants raise many environmental concerns and threaten aquatic life, wildlife, and humans. Sustainability is also one of the main drivers for increasing plastic recycling and decreasing the use of nonrecyclable plastic materials. Reducing plastic waste through recycling provides the following:

  • Reduces landfill waste

  • Reduces carbon footprint

  • Lowers energy needed to produce more plastics

  • Complies with the evolving environmental regulatory restrictions involving single-use plastics and plastic waste

  • Decreases the overall cost of plastics parts through the use of less expensive reused materials or recycling plastic scrap back into production cycles

These benefits encourage plastic compounders to alter their manufacturing processes and find solutions for the typical performance issues faced with the recycling and compounding of plastic materials. The most common recycled materials are post-consumer and post-industrial plastic resins, depending on the source of the plastic waste and processability. These resins include polyolefins, polyamides, low-density polyethylene (LDPE), high-density polyethylene (HDPE), polyvinyl chloride (PVC), polypropylene (PP), polyethylene terephthalate (PET), and other thermoplastic materials.

 A wide range of polymer additives is used in masterbatches and plastic recycling processes to reuse flexible and rigid plastics and recycle scrap and waste produced from plastic manufacturing processes.

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.

Melt stability 

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:

Plastic additives for automotive plastics


Examples: Automotive bumpers, roof racks, internal plastic parts, and lightweight accessories

Process types: Mostly injection molding

Plastic bottles and recycling of plastics

Plastic Packaging


Examples: Plastic containers, bottles, sheets, films, bags, cans, and other packaging materials

Process types: Extrusion, co-extrusion, blow molding, thermoforming, and calendaring

Consumer plastic bins and recycling of plastics

Consumer Products

Examples: sporting goods, appliances, flooring, carpeting, shoes, clothing, flowerpots, toys, and recycling bins

Process types: Injection molding, extrusion, and rotational molding


SI Group Recommended Solutions for Recycled Plastics:

Explore our recommended specialty polymer and plastic additives from SI Group that stabilize recycling streams and plastics. Find a suitable product by type of polymer or plastic and application.

Recycled Polypropylene (PP):


  • Recycle stream types: PIR and PCR
  • Typical challenges/problems solved: Compatibility, degradation from heat, melt stability, gas fading, maintaining mechanical properties, color stability, and FDA clearance for specific applications

  • Applications: BOPP films, packaging, consumer products, non-structure automotive parts

  • Recommended solutions:


Recycled Polypropylene/ Nylon (PP/PA6):


  • Recycle stream types: PCR
  • Typical challenges/problems solved: Compatibility, heat stability, melt stability, and impact resistance

  • Applications: Automotive parts, outdoor goods, and high-resistance consumer products

  • Recommended solutions:


Recycled Polyamide or Nylon (PA6 and PA66):


  • Recycle stream types: PIR and PCR
  • Typical challenges/problems solved: Compatibility, heat stability, melt stability, impact resistance, and weathering

  • Applications: Automotive parts, outdoor and high resistance consumer products

  • Recommended solutions:


Recycled High-Density Polyethylene (HDPE):


  • Recycle stream types: PIR and PCR
  • Typical challenges/problems solved: Compatibility, heat stabilization, melt stabilization, gas-fading resistance, color stabilization, plate-out, and FDA clearances

  • Applications: Packaging, pipes, and consumer products

  • Recommended solutions:

    • ANOX™ 20: Heat stability and weathering resistance additive

    • ANOX™ PP18: Heat stability and weathering resistance

    • ULTRANOX™ 626: High-performance, gas fading, and color stability

    • LOWINOX™ 1790: Plastic gas fading

    • ETHANOX™ 330: Heat stability, hydrolytic stability, migration, and FDA clearances for plastics

    • WESTON™ 705T: Melt stability, colorant stabilizer, hydrolytic stability, and reducing plate-out in plastics

    • POLYBOND™ PE coupling agents: Compatibility, retain critical mechanical properties, and compatibility with the use of filler materials and reinforcement fibers

Recycled Polyethylene Terephthalate (PET):


  • Recycle stream types: PIR and PCR
  • Typical challenges/problems solved: Heat stability, molecular weight retention, GHS compliance, color stability, availability in liquid form, and FDA clearances

  • Applications: Packaging and POY filament for clothing, shoes, and furniture

  • Recommended solutions:

    • ULTRANOX™ 626: Color control, thermal stability, molecular weight retention, FDA clearance, and low loading rate for packaging

    • WESTON™ 705T: Color control, thermal stability, molecular weight retention, FDA clearance, and liquid form for POY filaments

Many other plastic additives compound and reuse plastic polymers, such as plasticizers, internal lubricants, impact modifiers, flame retardants, antistatic additives, and others.

You can click below to explore our range of plastic stabilization additives from the SI Group. Find your solution by application and polymer type. Specialists are available for assistance and product recommendations.

Contact us today!

Get a Sample

PHONE  425.372.9328

Hi, let us know if you have any questions as you visit our website.

ChemPoint reps are here to assist you