title: The effect of cyclic swelling (octamethylcyclotetrasiloxane) on the physical properties of silicone breast implant shells.
abstract: Changes in the physical and mechanical properties of silica filled silicone elastomeric films were studied as a function of repeated sorption extraction cycling. The sorption of octamethylcyclotetrasiloxane (D4) on the properties of three silicone filled elastomeric films was analyzed. Two of the films, SILASTIC I and SILASTIC II, were shells of explanted breast implants and the third, a calendered film, prepared with similar composition to the elastomer used for the breast prosthesis were studied. The as-received (AR) SILASTIC I and II films contained 20 and 26.5 wt% non-cross-linked material that was removed by extraction with hexane. The failure properties of the extracted films are significantly higher than those of the AR films. The amount of swelling, weight gain, volumetric change, and the stress- and strain-to-fail of the films were measured in the as-received condition, and after a series of extractions and swellings. Repeated cycling (up to 5 cycles) of extraction-swelling had essentially no effect on the failure properties of films when all the diluent was removed. The effect of diluent on the failure properties of all three films was quite large. The stress-to fail of the swollen film was reduced a factor of 6 compared to baseline extracted samples while the corresponding strain values were reduced a factor of 5. The energy to fail of the swollen compared to baseline films was reduced almost a factor of 50. However, the overall mechanical properties of the films are restored when the diluent was removed. The mechanical forces involved in the swelling process do not degrade the polymer even when cycled through five swell-extract cycles.
authors: Department of Chemical Engineering, Center for Materials Research, Washington University, St. Louis, Missouri 63130, USA.
authors: Clarence J
authors: CJ
authors: Wolf
authors: Kenneth L
authors: KL
authors: Jerina
authors: Harold J
authors: HJ
authors: Brandon
authors: V L
authors: VL
authors: Young
mesh_terms: D000042:Absorption; D019928:Breast Implantation / Q000295:instrumentation* / Q000379:methods*; D006801:Humans; D008422:Materials Testing; D011474:Prosthesis Design; D012826:Silicone Elastomers / Q000737:chemistry*; D012833:Siloxanes / Q000494:pharmacology*; D013718:Tensile Strength; D013997:Time Factors
chemical_list: D012826:Silicone Elastomers; D012833:Siloxanes; C024064:octamethylcyclotetrasiloxane