The Recycling Code is used to identify various materials for return to the reuse cycle (recycling). The code consists of the recycling symbol: three (often green) arrows – intended to reflect the recovery cycle – and a number identifying the material. In most cases, an abbreviation indicating the material group is also given underneath. Because this abbreviation can vary (e.g. PET but also PETE is possible), the number is the decisive factor.
The identification codes for plastics (numbers 01 to 07) were first published under the name SPI resin identification coding system in 1988 by the Society of the Plastics Industry (SPI). The letter abbreviations for plastics are based on the standardised abbreviations for plastics.
Shorthands or shorthands for polymers are abbreviations of chemical names of important polymers used for plastics . The capital letter sequences used for this purpose are standardised in ISO 1043-1:2016-09 (Plastics – Code letters and abbreviations), DIN ISO 1629:2015-03 (Rubber and latices) and DIN EN ISO 18064:2015-03 (Thermoplastic elastomers). There is extensive compliance with the US standard ASTM D 1418-79.