Physical properties of a silicone prosthetic elastomer stored in simulated skin secretions.

STATEMENT OF PROBLEM

Facial prostheses worn over an extended time are exposed to various environmental factors, including sebaceous oils (sebum) and perspiration.

PURPOSE

This study investigated the physical properties of tensile strength and modulus, elongation, tear strength, hardness, weight, and color change, of a silicone facial elastomer after immersion for 6 months in simulated sebum and perspiration at 37 degrees C.

MATERIAL AND METHODS

Specimens made of Episil silicone elastomer were immersed in simulated alkaline or acidic perspiration as well as in sebum. Tensile and tear tests were conducted according to ISO specifications no. 37 and 39, respectively, in a Monsanto testing machine. Shore A hardness measurements were run according to ASTM D 2240. Weight changes were followed at 5, 15, 30, and 180 days, and color changes were determined in the CIE LAB system using a tristimulus colorimeter.

RESULTS

An improvement of mechanical properties for specimens immersed in acidic perspiration was attributed to facilitation of the propagation of cross-linking reaction during aging of the silicone samples. Some weight increase was observed for the specimens immersed into the aqueous solution, whereas for those immersed in sebum, weight loss was recorded, probably because of extraction of some compounds. In this latter case, the color change was lower than that corresponding to simulated perspiration.

CONCLUSION

The silicone specimens aged for a period, which simulates 1.5 years of clinical service, showed minimal changes with respect to the properties studied.