Microbiological testing of plastics: Ongoing activities of IBRG plastics project group to improve standard test procedures

The early development of standard test procedures for plastics was based primarily upon results of plasticised PVC. Ring tests carried out in the sixties used this material and provided the basis for national and international test specifications. In the meantime a large variety of plastics formulations has been developed which are chemically and structurally different from the formerly used PVC. This has prompted a re-examination of existing test specifications. For this reason the IBRG established a Plastics Working Group in 1984 to study the mechanism of the deterioration of plastics in relation to current standard test protocols. Fifteen laboratories from several European countries participated in a first international ring test (see Appendix). Two polyurethanes — a polyester and a polyether type — were chosen as test materials. A plasticized PVC was included for comparison with earlier interlaboratory experiments. Petri dish tests were carried out for four weeks and biodeterioration was assessed by visual examination and by weight loss. It was concluded that visual assessment as the sole criterion for the biodeterioration of polyurethanes was insufficient and that a test period of four weeks was too short for weight loss determination. In a second ring test with 12 participants, soil burial tests with the same test materials have been started. They will be conducted over a two-year period. Weight loss determinations and tensile tests will be carried out at six-month intervals. Provisional results are presented and are supplemented by joint experiments of some participants to examine the effects of special test parameters on the biodeterioration of plastics.