No abstract

No abstract

Transparent flexible silicone materials are useful in electronics, sensors, coatings, and so forth. However, to the best of our knowledge, the tensile strength of unreinforced silicone rubber is lower than 0.4 MPa, and the highest tensile strength of highly transparent silicone-modified materials is no more than 1.5 MPa. The poor mechanical property limits their further application in electronic devices. Here, a kind of UV-cured transparent flexible silicone materials with tensile strength as high as 2.2 MPa were prepared by a UV-initiated thiol−ene reaction of a sulfur-containing hyperbranched polycarbosilane and a thiol silicone resin. Interestingly, their tensile strength can increase from 2.2 to 5.6 and 5.7 MPa after being immersed in an aqueous solution of 10 wt % hydrochloric acid and 10 wt % NaCl for 7 days, respectively. It is argued that the increase of the tensile strength of cured films may be attributed to the −SiOCH 3 of the residual 3-trimethoxysilylpropanethiol in the sulfur-containing hyperbranched polycarbosilane. The performances of the cured materials were investigated in detail. These silicone materials exhibit transparency higher than 95% (wavenumber in the range of 400−800 nm), and the initial thermal decomposition temperatures of the cured materials are about 340 °C. These materials also show good anticorrosion property, and the mass loss of the materials immersed in the aqueous solution mediums is no more than 0.39 wt % even for 15 days.

Flexibility and mechanical performance are essential for transparent silicone materials applied in some optical and electronic devices; however, the tensile strength of transparent silicone materials is fairly low. To overcome this problem, a kind of UV-cured transparent flexible silicone material with quite a high tensile strength and elongation at break was developed through UV-initiated thiol− ene reaction by hyperbranched silicon-containing polymers (HBPs) with a thiol substitute and acrylate-terminated polyurethanes. Unexpectedly, it is found that both the tensile strength and elongation at break of the transparent silicone materials are extraordinarily high, which can reach 3.40 MPa and 270.0%, respectively. The UV-cured materials have good UV resistance ability because their transmittance is still as high as 93.4% (800 nm) even when aged for 40 min in a UV chamber of 10.6 mW cm −2 . They exhibit outstanding adhesion to substrates, and the adhesion to a glass slide, wood, and a tin plate is grade 1. The promising results encourage us to further improve the mechanical performance of flexible transparent silicone materials by effective chemical modification strategies with HBPs. An attempt was made to apply the UV-cured materials in a Gel-Pak box and it could be proved that the UV-cured materials may be one of the good candidates for use as packaging or protecting materials of optical or electronics devices such as the Gel-Pak product.

The conventional polyurethane (PU) coatings have poor heat resistance, which will undergo severe pyrolysis when the temperature exceeds 200 °C. To overcome the shortcoming of conventional PU coatings, an ultraviolet (UV)-cured solvent-free hyperbranched polycarbosilane modified PU coatings was prepared by sulfhydryl-terminated polyurethane and allyl-terminated hyperbranched polycarbosilane. The initial decomposition temperature (Td5%) of the UV-cured coating ranges from 258 to 268 °C, which is obviously higher than those of the conventional PU coatings reported. The coating shows fairly low water absorption in the range of 0.6–1.36 wt% and exhibits grade 1, grade 2 and grade 3 adhesion to glass, tin plate and aluminum sheet, respectively.