Jj. Kennan et al., EFFECT OF SALINE EXPOSURE ON THE SURFACE AND BULK PROPERTIES OF MEDICAL GRADE SILICONE ELASTOMERS, Journal of biomedical materials research, 36(4), 1997, pp. 487-497
Medical-grade silicone elastomers were subjected to accelerated aging
in saline to verify the hydrolytic stability of the elastomer. Tensile
strength, elongation at break, and the elastomer stress measured at 1
00% or 200% elongation did not change significantly for peroxide-cured
sheeting aged in 37 degrees C or 100 degrees C saline for 45 h. Under
similar condition, hydrosilylation cured sheeting behaved similarly;
however, increases in stresses measured at 100% and 200% elongation we
re observed after the first hour of treatment. After the first hour, t
he physical properties remained relatively constant. On either elastom
er, initial liquid drop advancing contact angles for water ranged from
110 degrees to 115 degrees, and in no case was a change of >6 degrees
observed as a result of aging in saline for 45 h at temperatures up t
o 97 degrees C. The high advancing angles indicated that the surface r
emained largely hydrophobic. Initial liquid drop receding contact angl
es ranged from 48 degrees to 64 degrees, with receding contact angles
being more sensitive to accelerated aging, in one case decreasing to 1
4 degrees. Similar decreases in receding contact angle were observed o
n polyethylene subjected to the same accelerated aging conditions. Dec
reases in receding contact angle were not considered to be indicative
of extensive hydrolysis. The observed contact angle phenomena are cons
istent with current views of contact angle hysteresis being caused by
surface heterogeneity. There was no evidence of significant surface or
bulk siloxane hydrolysis under these accelerated aging conditions. (C
) 1997 John Wiley & Sons, Inc.