How to reduce internal air bubbles to enhance structural density during silicone pad manufacturing?
Release Time : 2026-01-26
In the manufacturing process of silicone pads, the presence of internal air bubbles significantly weakens their structural density, thereby affecting the product's physical properties, sealing performance, and lifespan. Bubble formation mainly stems from uneven raw material mixing, molding process defects, or environmental interference, requiring systematic optimization measures for control. The following analysis focuses on raw material handling, process improvement, equipment upgrades, and environmental control.
Raw material mixing is the primary step in bubble formation. When mixing silicone substrate with additives such as curing agents and thermally conductive fillers, excessively fast stirring speeds or inconsistent stirring directions can easily trap air, forming microbubbles. Furthermore, uneven particle size distribution or untreated surfaces of thermally conductive fillers such as alumina and boron nitride can lead to poor dispersion within the silicone matrix, resulting in localized voids. To address this issue, efficient mixing equipment, such as twin-roll mills or internal mixers, is required. Low-speed, directional stirring ensures uniform mixing of raw materials. Simultaneously, surface coatings or chemical modifications of the thermally conductive fillers can reduce their surface energy, improve compatibility with the silicone matrix, and reduce void formation.
The molding process is crucial for bubble removal. Compression molding is a common method for silicone pads, but improper mold design, such as insufficient number or improper placement of vents, can lead to gas retention. Optimizing the mold structure, increasing the number of vents, and arranging them appropriately can significantly improve gas venting efficiency. Furthermore, precise control of molding temperature and pressure is crucial: too low a temperature results in poor silicone flow, making it difficult for gas to escape; too high a temperature may cause premature curing of the silicone, blocking gas channels. Therefore, optimal molding parameters must be determined experimentally based on the type of silicone and filler characteristics to ensure uniform silicone flow and sufficient venting within the mold.
The vulcanization process is a critical stage in the formation of the silicone pad structure. Controlling the vulcanization temperature and time directly affects the degree of cross-linking of the silicone and the effectiveness of bubble removal. Too low a vulcanization temperature leads to incomplete cross-linking of the silicone, easily resulting in residual bubbles; too high a temperature may cause silicone decomposition, generating gas. Simultaneously, insufficient vulcanization time will result in incomplete curing of the silicone, preventing the release of internal stress and leading to microcracks. Therefore, strict monitoring of vulcanization temperature and time is necessary, employing a segmented vulcanization process, such as low-temperature pre-vulcanization followed by high-temperature formal vulcanization, to ensure sufficient cross-linking of the silicone and complete bubble removal. Vacuum degassing is an effective auxiliary method for reducing air bubbles. After mixing the silicone and before molding, it is placed in a vacuum environment. By reducing the pressure, the air bubbles expand and escape. The vacuum degassing equipment must have sufficient vacuum and degassing time to ensure complete bubble removal. For high thermal conductivity silicone pads, due to the high filler density and difficulty in bubble removal, centrifugal degassing can be combined. The centrifugal force generated by high-speed rotation accelerates the bubbles to float, further improving the degassing effect.
Environmental control also has a significant impact on bubble formation. Humidity, dust, and impurities in the production environment may mix into the silicone raw material, forming bubbles or defects. Therefore, it is necessary to keep the production workshop clean and control humidity within a reasonable range to avoid moisture absorption or contamination of the raw material. At the same time, operators must operate according to regulations, such as wearing gloves and using cleaning tools, to reduce the introduction of air bubbles due to human factors.
Post-processing can further repair minor defects in silicone pads. For silicone pads that have been molded but have a small number of air bubbles, a hot-pressing repair process can be used. By reheating and pressurizing, the air bubbles are compressed and closed, improving the structural density. Furthermore, surface coating treatment can seal the micropores on the silicone pad surface, preventing gas penetration and improving its wear resistance and corrosion resistance.
Through systematic measures such as optimized raw material mixing, improved molding processes, precise control of vulcanization parameters, vacuum degassing assistance, strict environmental control, and post-treatment repair, internal air bubbles in silicone pad manufacturing can be significantly reduced, enhancing its structural density and thus improving the overall performance and reliability of the product.