Effect of Vinyl-Terminated Silicone Oil Chain Length and Reinforcing Agent on the Properties of Silicone Rubber

To solve the problems of low strength and high viscosity of room temperature vulcanized liquid silicone rubber, a series of terminated vinyl silicone oil were designed and synthesized, and low viscosity and high strength silicone rubber were prepared by the mechanical reinforcing agent. the results show that the molecular structure of the vinyl-terminated silicone oil has a significant effect on the mechanical properties and viscosity of the silicone rubber, and the best performance is found when the content of vinyl-terminated silicone oil is 0.16%. The low viscosity and high strength silicone rubber prepared from it was reinforced by vinyl MQ resin and fumed silica, which had a significant effect on improving the performance. Its tensile strength increased to 5.03 MPa, elongation at break to 338.90%, and tear strength to 7.15 kN/m compared to conventional silicone rubber, while the hardness increased to 43°. The viscosity is 34.9 Pa•s. The compression modulus is 7.48 MPa.

In Vitro Study of the Interaction of Innate Immune Cells with Liquid Silicone Rubber Coated with Zwitterionic Methyl Methacrylate and Thermoplastic Polyurethanes

The biocompatibility of medical devices, such as implants and prostheses, is strongly determined by the host’s immune response to the implanted material. Monocytes and macrophages are main actors of the so-called foreign body reaction. The innate immune system macrophages (M) can be broadly classified into the pro-inflammatory M1-type and the anti-inflammatory, pro-healing M2-type. While a transient inflammatory initial state can be helpful during an infection, persistent inflammation interferes with proper healing and subsequent regeneration. The functional orientation of the immune response, mirrored by monocyte polarization, during interaction with different biomaterials has not yet been sufficiently explored. In implant manufacturing, thermoplastic polyurethane (TPU) represents the state-of-the-art material. The constantly growing areas of application and the associated necessary adaptations make the optimization of these materials indispensable. In the present study, modified liquid silicone rubber (LSR) were compared with two of the most commonly used TPUs, in terms of monocyte adhesion and M1/M2 polarization in vitro. Human monocytes isolated from venous blood were evaluated for their ability to adhere to various biomaterials, their gene expression profile, and their cytokine release. Based on the results, the different polymers exhibit different potential to bias monocytes with respect to early pro-inflammatory cytokine production and gene transcription. Furthermore, none of our test materials showed a clear trend towards M1 or M2 polarization. However, we were able to evaluate the inflammatory potential of the materials, with the classic TPUs appearing to be the most unreactive compared to the silicone-based materials.

Preparation of one-component addition-cure liquid silicone rubber coating with enhanced storage stability and bond strength

It is of great interest and challenge to simultaneously improve the storage stability and bond strength of one-component addition-cure liquid silicone rubber (OLSR) coating for electronic circuit board. In this work, we proposed an efficient approach to address this issue by incorporating both cyano-modification platinum catalyst (CN-PT) and urethane-containing poly(hydromethylsiloxane) (N-PHMS) into OLSR coating using a mechanical mixer. The CN-PT and N-PHMS were synthesized through thermal polymerization reaction and hydrosilylation reaction, respectively. The OLSR coating containing 0.3 phr CN-PT and 3 phr N-PHMS showed the best properties, with a tensile bond strength of 1.63 MPa, a storage period > 180 d at 25°C, and a curing rate < 2 h at 80°C. The salt-spray resistance and continuous power-on performance of OLSR coating were also improved, compared with pure OLSR coating. The synergism of CN-Pt and N-PHMS on the enhancement both the storage stability and bond strength of OLSR coating was also explored. Our findings exhibited great potentials for fabricating OLSR coating with excellent long-term stable service performance including high storage stability and protective ability.

The Use of Zwitterionic Methylmethacrylat Coated Silicone Inhibits Bacterial Adhesion and Biofilm Formation of Staphylococcus aureus

In recent decades, biofilm-associated infections have become a major problem in many medical fields, leading to a high burden on patients and enormous costs for the healthcare system. Microbial infestations are caused by opportunistic pathogens which often enter the incision already during implantation. In the subsequently formed biofilm bacteria are protected from the hosts immune system and antibiotic action. Therefore, the development of modified, anti-microbial implant materials displays an indispensable task. Thermoplastic polyurethane (TPU) represents the state-of-the-art material in implant manufacturing. Due to the constantly growing areas of application and the associated necessary adjustments, the optimization of these materials is essential. In the present study, modified liquid silicone rubber (LSR) surfaces were compared with two of the most commonly used TPUs in terms of bacterial colonization and biofilm formation. The tests were conducted with the clinically relevant bacterial strains Staphylococcus aureus and Staphylococcus epidermidis. Crystal violet staining and scanning electron microscopy showed reduced adhesion of bacteria and thus biofilm formation on these new materials, suggesting that the investigated materials are promising candidates for implant manufacturing.