Long term natural ageing of silicone elastomers

Oldfield, D.; Symes, Theodore E. F.

doi:10.1016/0142-9418(95)00018-6

Cited by 50 publications

(27 citation statements)

References 2 publications

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“…Medical grade silicone is considered to be a material with good biostability8, 9 in that it is not expected to degrade once implanted. However, several studies show evidence of a change in mechanical properties of silicones after implantation or artificial ageing,9–15 while other studies claim that no changes occur 16–18…”

Section: Introductionmentioning

confidence: 99%

The effect of the environment on the mechanical properties of medical grade silicones

et al. 2008

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Silicone spacers have been in use as replacement joints in the human hand for over 30 years. Since they were first used there has been a number of designs all of which have had problems with fracture. This may be due to a defect in the material caused during implantation, or by bony intrusions within the arthritic hand after implantation. The aim of this research was to investigate the effect of the environment on the mechanical properties of medical grade silicones used for human implantation. The materials were subjected to static tensile testing after various forms of ageing. The environmental conditions included temperatures of 37 and 80 degrees C and the environments of Ringer's solution, distilled water, and air. The environmental conditions employed resulted in reduced mechanical strength with ageing time of the silicones. This research supports the view that failure of silicone implants in the hand could be partly attributed to the effects of environmental ageing of the material.

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Section: Introductionmentioning

confidence: 99%

The effect of the environment on the mechanical properties of medical grade silicones

et al. 2008

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“…Poly(dimethylsiloxane) (PDMS) is a commonly used elastomeric material, which requires the addition of a filler phase to produce a material with many useful physical properties. When such materials are placed in a harsh environment certifying component performance becomes exceedingly challenging as many trends in properties are complex [2,3].…”

Section: Introductionmentioning

confidence: 99%

The stability of polysiloxanes incorporating nano-scale physical property modifiers

Lewicki

Patel

Morrell

et al. 2008

Science and Technology of Advanced Materials

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Reported here is the synthesis and subsequent characterization of the physical and chemical properties of novel polysiloxane elastomers modified with a series of polyhedraloligomericsilsequioxane (POSS) molecular silicas. The physical properties of the formulated nanocomposite systems have been characterized with a combination of dynamic mechanical analysis (DMA), broadband dielectric spectroscopy (BDS) and confocal Raman microscopy. The results of the physical property characterization demonstrate that the incorporation of low levels (1-4% by wt.) of POSS particles into the polysiloxane network leads to significant improvements in the mechanical properties of the elastomer and significantly alters the motional chain dynamics of the system as a whole. The results of studies performed to assess the long-term stability of these novel nanocomposite systems have demonstrated that POSS physical property modifiers can significantly alter the thermal stability of polysiloxane elastomers. Physically dispersed POSS has also been shown in some cases to be both mobile and disruptive within the polysiloxane networks, agglomerating into domains on a micron scale and migrating to the surface of the elastomers. This work demonstrates both the potential of POSS nanoparticles as physical property modifiers and describes the effects of POSS on the physical and chemical stability of polysiloxane systems.

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“…These IVR designs utilize non-degradable polymers as the ring material [9,21]. Disposal of non-degradable IVRs could become a significant environmental issue if IVRs are used by millions of women each year in the developed and developing world.…”

Section: Introductionmentioning

confidence: 99%

Engineering a degradable polyurethane intravaginal ring for sustained delivery of dapivirine

Kaur

Gupta

Poursaid

et al. 2011

Drug Deliv. and Transl. Res.

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We describe the engineering of a degradable intravaginal ring (IVR) for the delivery of the potent HIV-1 reverse transcriptase inhibitor dapivirine. The degradable polymer used in fabricating the device incorporated poly(caprolactone) ester blocks in a poly(tetramethylene ether) glycol ABA type polyurethane backbone. The polymer was designed to maintain its structure for 1 month during usage and then degrade in the environment post-disposal. In vitro release of dapivirine showed zero-order kinetics for up to 1 month and significant levels of drug release into engineered vaginal tissue. The mechanical properties of the degradable IVR were comparable to those of a widely used contraceptive intravaginal ring upon exposure to simulated vaginal conditions. Incubation under simulated vaginal conditions for a month caused minimal degradation with minimal effect on the mechanical properties of the ring and polymer. The cytotoxicity evaluation of the drug-loaded IVRs against Vk2/E6E7 human vaginal epithelial cells, Lactobacillus jensenii, and engineered vaginal tissue constructs showed the degradable polyurethane to be non-toxic. In vitro evaluation of inflammatory potential monitored through the levels of inflammatory cytokines IL-8, IL-1α, IL-6, IL-1β, and MIP-3α when engineered EpiVaginal™ tissue was incubated with the polyurethanes suggested that the degradable polyurethane was comparable to commercial medical grade polyurethane. These results are encouraging for further development of this degradable IVR for topical vaginal delivery of microbicides.

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Long term natural ageing of silicone elastomers

Cited by 50 publications

References 2 publications

The effect of the environment on the mechanical properties of medical grade silicones

The effect of the environment on the mechanical properties of medical grade silicones

The stability of polysiloxanes incorporating nano-scale physical property modifiers

Engineering a degradable polyurethane intravaginal ring for sustained delivery of dapivirine

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