Before the silicone rubber is formally filled, encapsulated or vulcanized, it is vacuumed. It seems to be just “one more process”, but it is actually a key step in determining the final quality and reliability.Its benefits can be summarized as four aspects: “defoaming, improving quality, prolonging life, and reducing costs”.
First of all, defoaming-completely eliminate the hidden dangers of internal gas.The viscosity of silicone rubber is usually as high as tens of thousands of centipoise, and it is easy to absorb air to form bubbles when stirring or transferring.These air bubbles cannot escape on their own during the curing process, leaving pores or surface needle holes in the product.Vacuuming causes the air bubbles to rapidly expand, rupture and be extracted under negative pressure, which can reduce the residual air bubble rate from 5% of the traditional process to less than 0.1%.Especially in high-demand applications such as LED packaging, automobile ignition coils, and medical catheters, trace amounts of air bubbles can cause light loss, partial discharge, or decreased biocompatibility. Vacuum defoaming has become a mandatory requirement.
Secondly, quality improvement-simultaneous improvement of mechanics and appearance quality.The vacuum environment not only sucks away air, but also takes away small molecules of volatiles, moisture and side reaction products.If these small molecules remain in the colloid during vulcanization, they will reduce the crosslinking density, causing the surface to become sticky, hardness drift, rebound attenuation and yellowing.Studies have shown that the tensile strength of vacuum defoamed silicone rubber can be increased by more than 10%, the tear strength can be increased by 15%, the thermal conductivity can be increased by 18%, and the surface finish can be significantly improved.For products that require a transparent or high-gloss appearance, such as optical lenses and consumer electronics waterproof rings, vacuum treatment is almost the only way to obtain A grade A surface.
Third, longevity-significantly extend service life and reliability.The presence of air bubbles will form a stress concentration point inside the product, which will induce microcracks under high and low temperature circulation, vibration or long-term compression conditions, which will eventually lead to sealing failure or functional attenuation.After the sealing ring of the power battery is vacuum defoamed, the temperature resistance level is increased from 120℃ to 150℃, and the aging life is extended by 2 times.In medical implantable silicone, thorough removal of air bubbles can also avoid local inflammation caused by body fluid penetration and improve long-term biological stability.
Finally, cost reduction-reduce overall costs and improve process efficiency.The reduction of surface defects directly brought about a jump in the yield rate. After a catheter company reduced the bubble residue rate from 12% to 0.05%, the yield rate increased from 87% to 99.3%, and the rework and scrap were almost cleared.The vacuum stirring and defoaming machine shortens the traditional 30-minute stirring and exhaust time to 5-8 minutes, reduces energy consumption by 15%, and increases production capacity by more than 40%.In addition, since the vacuum treatment can eliminate low molecular impurities in advance, the subsequent vulcanization mold pollution is reduced, and the cleaning frequency can be reduced from once a day to once a week, further saving maintenance labor and solvent consumption.
Taken together, vacuuming is not simply defoaming, but through the knock—on effect of “removing gas—purifying system-optimizing structure”, the reliability, consistency, life and economy of silicone rubber products are pushed to a higher level at the same time.In high-end application scenarios such as new energy vehicles, semiconductor packaging, and medical devices, this process has changed from “optional” to “must-do”, becoming the threshold technology for silicone rubber to enter the era of precision manufacturing.
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Ethyl Silicone Rubber IOTA 2056 HTV - IOTA CORPORATION LTD.
