Search

In this work, a facile in situ precuring and supercritical CO2 (sc‐CO2) foaming technology is proposed to fabricate silicone rubber foam (SRF) with a tunable cell structure. Uncured silicone rubber is put into the autoclave to saturate sc‐CO2 directly, which not only shorts the saturation time but also accelerates the curing reaction in the precuring process. In the foaming process, cell nucleation is triggered by rapid release of pressure. The cell structure of SRF samples with cell size range of 9.45 to 128.09 μm, cell density range of 3.5 × 105 cells/cm3 to 5.7 × 108 cells/cm3, and porosity range of 28.35% to 77.28% are successfully fabricated by controlling of precuring time, saturation pressure and foaming temperature. To guarantee the dimensional stability and optimize surface quality of SRF samples, in situ post‐curing process is implemented within the foaming mold. With the increase of cell size from 9.91 to 128.09 μm, the compressive stress at strain of 75% decreases from 2.19 to 0.61 MPa, while the energy loss coefficient reduces from 35.4% to 16.9%, exhibiting excellent compression recovery steady. The new technique integrates the precuring, foaming process and post‐curing into an autoclave to simplify the SRF procedure. [ABSTRACT FROM AUTHOR]

ABSTRACT A new high-ultraviolet (UV)-transmission silicone-resin polymeric material was prepared via curing during hydrosilylation of tetramethyltetravinylcyclotetrasiloxane with tetramethylcyclotetrasiloxane by a liquid-surface supernatant method, using a stepwise heating program to avoid spontaneous combustion of the reaction mixture. The relationships were investigated in detail between reactive groups, cross-linking density, mechanical and UV-transmission properties. For this purpose, UV transmittance and dynamic mechanical properties, respectively, of the silicone resin were measured with UV-visible spectrophotometry and dynamic mechanical thermal analysis. In addition, surface roughness was evaluated with an atomic force microscope as well as an interferometer. The curing process was monitored by Fourier transform infrared spectroscopy and rotational rheometry. The cyclic silicone oils were compared with linear ones in structure and product properties. The results indicated that stepwise temperature control during curing process was particularly indispensible due to the presence of active SiH bonds, and that the silicone resin of high modulus, high UV transmittance (92.7%) and low surface-roughness was largely homogeneous in cross-linking points distribution. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 43308. [ABSTRACT FROM AUTHOR]