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Magazines & Newsletters / ASTM Standardization News


September/October 2008

Resin Identification Codes

New ASTM Standard Based on Society of the Plastics Industry Code Will Facilitate Recycling

recycleablesNearly all of us are familiar with the symbol of a number enclosed in a triangle of arrows that is often found on the bottom of plastic containers, although we may not always specifically know the meaning behind the symbol. Developed in 1988 by the Society of the Plastics Industry Inc., the symbol identifies the resin content of the container on which has been placed. For 20 years SPI’s resin identification code system has facilitated the recycling of post-consumer plastics in the United States.

SPI Code History

As a growing number of communities were implementing recycling programs in the 1980s, the need for a consistent and uniform code that would identify the resin(s) contained in each plastic container became apparent. Quality control sorting prior to recycling is important to ensure that recycled plastic is as homogenous as possible for end users. This is an important point because plastic is not limited to any one particular material. Instead, plastics are a group of related materials with different properties. These materials can be engineered individually or in combinations to be used effectively in a variety of applications.

Since its development, 39 states have adopted legislation on the use of resin identification codes that is consistent with the SPI system. Variations of the code have been adapted for use in the United Kingdom and China, and use of the SPI code is recommended by the British Plastics Federation and Plastics- Europe (formerly the Association of Plastics Manufacturers in Europe). With recycling more important than ever, SPI’s resin identification code continues to play a crucial role in the process, providing manufacturers a uniform system that can be universally applied.

Now the SPI code for resin identification is the basis for a proposed new ASTM International standard, WK20632, Practice for Marking Plastic Products for Identification in Reuse and Recycling. The proposed standard is being developed by Subcommittee D20.95 on Recycled Plastics, part of ASTM International Committee D20 on Plastics.

“SPI is pleased to be working with ASTM International, as well as industry and government experts on this important endeavor and looks forward to developing an updated resin coding system so that everyone can more easily identify, reuse and recycle all types of plastics,” said SPI President William R. Carteaux. “Being environmentally responsible is something that we all need to do, and the plastics industry is continuously striving to do its part.”

Purposes of the Code

The purposes of the original SPI code were to:

  • Provide a consistent national system to facilitate recycling of post-consumer plastics;
  • Target plastic containers;
  • Offer a means of identifying the resin content of bottles and containers commonly found in the residential waste stream; and
  • Provide coding for the six most commonly found resin types, with a seventh category created for all other types not found within codes 1-6.

Categories 1-7 are: 1) polyethylene terephthalate (PETE); 2) high density polyethylene (HDPE); polyvinyl chloride (PVC or vinyl); 4) low density polyethylene (LDPE); 5) polypropylene (PP); 6) polystyrene (PS); and 7) other, including materials made with more than one resin from categories 1-6.

The Proposed ASTM Standard

While originally intended to aid in the recycling of post-consumer plastic bottles and rigid containers, the use of the SPI code has expanded to potentially include packaging films and finished products that are reusable and/or recyclable. This will be reflected in the proposed standard, as WK20632 will expand on the original SPI system by providing for additional codes for resin types not covered in codes 1-6, potentially adding to the list of materials currently available for recycling.

In addition to expanding the range of material covered, the proposed ASTM standard will allow for containers to be coded with numbers as they stand in the original SPI code and/or the “zero plus number” (for example, 01) system that is used in similar
coding systems in the United Kingdom and China.

By providing for the addition of new types of resin and allowing all stakeholders to participate in future revisions to the proposed standard, WK20632 will give the original SPI codes a means of changing as recycling and/or reuse needs change.

For Further Information

For more information on the Society of the Plastics Industry and SPI’s Resin Identification Code, click here. Subcommittee D20.95 welcomes all interested parties from the plastic container and resin industries, as well as from the recycling community, to participate in the ongoing development of WK20632. For technical information on WK20632, contact Alan D. Kupfer, Georgia Gulf Corp., Plaquemine, La. (phone: 225-685-1257). Committee D20 meets Nov. 16-19 during the November committee week in St. Louis, Mo. For meeting or membership information, contact Brynn Murphy (phone: 610-832-9640).