Wide variations often exist within each type of polymer used in surgical implants, blood conduits, and other biomedical devices. Careful, explicit characterization of the particular materials of construction can minimize difficulties in understanding anomalous behavior. For example, merely listing the generic name of a specific material does not necessarily indicate important differences in crystallinity, molecular weight, chain branching, crosslinking, end-group structure, or additives that can exist from batch to batch or from manufacturer to manufacturer. Difficulties in obtaining performance suggested by the work of others may result from just such unrecognized differences. Though attributing success or failure to materials described only by generic names has long been recognized as misleading,* the practice continues. Furthermore, undefined methods of processing substances, inadequate analyses and reporting of the tissue pathology surrounding implants, and lack of standard in vivo and in vitro test protocols add to confusion. Also, the occasional publication of toxicological data in which only code names appear deprives the scientific community of potentially valuable data.
An adequate characterization of commercial polymers should include at least the following: (1) Generic name (polyethylene, polytetrafluoroethylene, silicone rubber, etc.); ( 2 ) trade name and number (Marlex 50, Teflon TFE, Medical Silrtstic 382, etc.); (3) manufacturer's lot or batch number; (4) processing details (method of fabrication, sterilization, etc.). All experimental materials from noncommercial sources and, if possible, commercial materials should be described, a t least, by the following: ( 5 ) Source (investigator, institution, etc.) ; (6) composition (basic formula, additives, etc.) ; (7) physical state (solid, amorphous, etc.) ; (8) tissue pathology (if available).