What does the Plastic Recycling Codes Indicate?
To facilitate correct plastic waste sorting of bottles and containers commonly found in the residential waste stream for the purposes of recycling, the SPI Resin Identification Symbol System, also known as the material container coding system, was created The Society of Plastics Industry (SPI) in 1988. At the same time, the overwhelming majority of plastic packaging was made with one of six resins：
polyethylene terephthalate (PET or PETE);
high density polyethylene(HDPE);
vinyl (Polyvinyl Chloride or PVC), low density polyethylene(LDPE);
low density polyethylene (LDPE);
SPI accounts for these six plastic types, assigning each a number from 1 to 6 as a uniform, nationwide and international voluntary labeling system. SPI also includes a seventh code, identified as “7-OTHER,’’ to be used when the product in question is made with a plastic other than the common six, or is made of more than one plastic used in combination as the plastic industry has evolved, many new plastics have been invented that do not meet the specific criteria to be labeled 1 through 6.
The generic SPI code “7-OTHER’ should not be used to determine whether an article is safe or unsafe both because the code was not designed as a means for determining the particular type of plastic used to manufacture the article bearing the code. Polycarbonate (PC) is a newer petroleum-based with the generic SPI code of “7-OTHER’.