Structure and properties of closed‐cell foam prepared from irradiation crosslinked silicone rubber

Abstract

Silicone rubber foam was prepared through crosslinking with electron beam irradiation and foaming by the decomposing of blowing agent azobisformamide (AC) in hot air. The crosslinking and foaming of silicone rubber was carried out separately, which was different from the conventional method of chemical crosslinking and foaming. After foaming, the silicone rubber foam was irradiated again to stabilize the foam structure and further improve its mechanical properties. The effects of irradiation dose before and after foaming, and the amount of blowing agents on the structure and properties of silicone rubber foam were studied. The experimental results show that with the increase of AC content, the average cell diameter of silicone rubber foam increases a little, the foam density decreases to a minimum value when AC content is 10 phr. With the increase of irradiation dose before foaming from 10 to 17.5 kGy, the cell nucleation density of silicone rubber foam increases, the average cell diameter decreases, and the foam density increases. With the increase of irradiation before foaming, the tensile strength, tensile modulus, and the elongation at break of the silicone rubber foam increase. Through irradiation crosslinking again after foaming, the foam density is decreased and the mechanical properties of silicone foam are further improved.

Influence of the irradiation dose in the cellular structure of natural rubber foams cross-linked by electron beam irradiation

“…Therefore, it was projected that a free foaming process occurred, which usually resulted in the formation of isotropic cells (R = 1) as obtained in this work. Similar results to this work were previously reported in other works but they employed different types of polymers: silicon and polyethylene (Liu et al, 2009;Wang et al, 2007).…”

“…The most significant contribution to the formation of these homogeneous cellular structures with very low cell sizes came from the nucleation mechanisms, which were clearly intensified by applying these IDs. This is a phenomenon which has been previously reported in literature (Liu et al, 2009). …”

“…These mechanisms are directly connected with the obtained final cellular structures. For instance, an increase of the nucleation rate (higher cell nucleation densities/N 0 ) should lead to higher cell densities (N v ) as already observed in previous works (Liu et al, 2009). In the same way, the use of polymers with higher stabilities in the molten state should lead to lower degeneration rates of the cellular structure, as proven by the presence of cells with lower sizes and more homogenous cellular structures.…”

Surface-active copolymer formation stabilizes PEG droplets and bubbles in silicone foams

“…Bubbles were generated primarily from dissolved gases within the silicone and, to a much lesser extent, by hydrogen generated from the reaction of adventitious moisture with the curing agent (R 3 SiH + H 2 O ? R 3 SiOH + H 2 ) [12,13].…”

Effects of platinum compounds/superfine aluminum hydroxide/ultrafine calcium carbonate on the flame retardation and smoke suppression of silicone foams

“…1 They possess outstanding characteristics, such as nontoxicity, chemical stability, electrical insulation, durability in myriad weather conditions, resistance to ultrahigh and ultralow temperatures; they are lightweight, heatproof, soundproof, and sound shock absorbing. [4][5][6] However, because of the abundant hydrocarbon groups on its side chain, SR is a combustible material; it can combust and release choking smoke once ignited. [4][5][6] However, because of the abundant hydrocarbon groups on its side chain, SR is a combustible material; it can combust and release choking smoke once ignited.…”