Plastics, Information

Plastic Recycling Processes

Plastic Recycling Processes

There are three distinct approaches to the recycling of post-consumer plastic packaging materials.Related Resources
• Introduction
• Plastics & Microwaves
• Production
• Recycling Rates
• Renewable Plastics
• Types

• Recycling CenterThe packaging may:
* be reused directly
* undergo physical reprocessing (e.g., grinding and melting) and reformation
* be subjected to chemical treatment whereby its components are isolated and reprocessed for use in manufacture

Reuse

The reuse of plastic bottles presents several special concerns. Plastic bottles are more likely than glass to absorb contaminants that could be released back into food when the bottle is refilled. Analytical protocols may need to be developed to demonstrate that, after cleaning, contaminant levels are sufficiently low so that the contents of the refilled bottle would not be adulterated.

In addition, while washing and sanitizing or sterilizing the bottles must be shown to be effective for removing contaminants to an acceptable level, the cleansing operation should not have an adverse effect on the integrity of the bottles. Bottles must retain structural integrity and be functional after each cycle of washing and reuse. Plans for reuse of plastic bottles could include, for example, a limit on the number of use cycles a bottle will undergo, an expiration date for the use of such articles, a visual inspection system for gross contamination and damaged bottles, or some combination of these approaches. A limit on the number of use cycles could be difficult to implement, requiring a method for monitoring the number of times a bottle has been reused.

Physical Reprocessing

Physical reprocessing involves grinding, melting, and reforming plastic packaging material. The basic polymer is not altered during the process. Prior to melting and reforming the polymer, the ground, flaked, or pelletized resin is washed to remove contaminants. The size of the resin flakes or pellets could influence the effectiveness of the washing. Smaller particles would provide a greater surface area for enhancing the effectiveness of the wash. Different resins may also undergo different reforming conditions, such as different processing temperatures, the use of vacuum stripping, or other procedures, that could influence contaminant levels. During the grinding or melting phases, the reprocessed material may be blended with virgin polymer.

Chemical Reprocessing

Chemical reprocessing may involve depolymerization of the used packaging material with subsequent regeneration and purification of resulting monomers (or oligomers). The monomers are then repolymerized and the regenerated or reconstituted polymer is formed into new packaging. Regenerated monomer, polymer, or both may be blended with virgin materials. The regeneration process may involve a variety of monomer/polymer purification steps in addition to washings, such as distillation, crystallization, and additional chemical reaction.

Source: Edited version of Points to Consider for the Use of Recycled Plastics in Food Packaging, US Food and Drug Administration.

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