Improved Mechanical and Sound Absorption Properties of Open Cell Silicone Rubber Foam with NaCl as the Pore-Forming Agent

Abstract

Porous materials hold great potential in the field of sound absorption, but the most abundantly used materials, such as Polyurethane (PU) foam and polyvinyl chloride (PVC) foam, would inevitably bring environmental harms during fabrication. In this study, the nontoxic addition-molded room temperature vulcanized silicone rubber is chosen as the matrix, and NaCl particles are chosen as the pore forming agent to prepare open cell foams via the dissolve-separating foaming method. The effect of different amounts of NaCl (0–100 phr) on the cell structure, mechanical and sound absorption properties is investigated and analyzed. The results indicate that the cell structure could be tailored via changing the addition amount of NaCl, and open cell silicon rubber foams could be achieved with more than 20 phr NaCl addition. Open cell silicon foams show the most effective sound absorption for sound waves in middle frequency (1000–2000 Hz), which should be attributed to the improved impedance matching caused by the open cell structures. Additionally, the mechanical properties, including hardness, tensile strength and corresponding elastic properties, gradually decay to a steady value with the increasing addition amount of NaCl. Therefore, open cell silicone rubber foams are capable of sound absorption in middle frequency.

Chemistry, Processing, Properties, and Applications of Rubber Foams

“…[2], so the production of synthetic cellular materials was devoted to mimic nature leading to the development of one of the most important and widely used man-made class of materials with a wide range of applications in automobiles, aeronautics, packaging, medicine, construction, etc. [3][4][5][6][7][8][9].…”

Preparation of porous β-SiAlON ceramics using corn starch as pore-forming agent

“…The porous Si 3 N 4 -based ceramics are potential radome materials due to their high strength and porosity; thus, these ceramics have received a considerable research attention in recent years [11,12]. A number of research studies have focused on preparing porous Si 3 N 4 -based ceramics using different methods, such as addition of pore-forming agent, organic foam impregnation, and sol-gel methods [13][14][15]. Zhang [16] reported the successful synthesis of porous Si 2 N 2 O-Si 3 N 4 multiphase ceramics by using the silica-hollow microspheres as the source of SiO 2 and pore-forming agent.…”

Improved low-frequency sound absorption of porous silicone rubber resonance sheet with periodic cavities

“…Compared with traditional indoor sound absorption and noise reduction materials, such as polyurethane foam and polyvinyl chloride foam, addition liquid silicone rubber 15 develops faster than free radical cross-linked liquid silicone rubber and polycondensation liquid silicone rubber, and has the advantages of simple preparation process, easy implementation, and no by-products of vulcanization. 13,16 Additionally, liquid silicone rubber has better fluidity than mixed silicone rubber, and can be injection molded and compression molded, and the vulcanization rate is controllable.…”

“…The porous liquid silicone rubber material prepared by introducing a foaming agent into the liquid silicone rubber has the advantages of softness, light weight, high resilience rate, controllable cell size and density, easy implementation, corrosion resistance, weather resistance, etc., which is suitable for sound absorption and noise reduction in most indoor and outdoor environments. 13,15,16,[18][19][20][21] Additionally, introducing chemical foaming agents into the liquid silicone rubber, such as foaming agents or pore formers, foamed material with countless cells could be prepared after different processes. Different types of cell structures (closed, open, and mixed cell structures) could be achieved by adjusting the hydrogen-containing silicone oil, and the cell size can also be tailored.…”

“…Different types of cell structures (closed, open, and mixed cell structures) could be achieved by adjusting the hydrogen-containing silicone oil, and the cell size can also be tailored. 15 Therefore, silicone rubber is suitable for preparing sound absorption foams with easy implementing process.…”