Versatility and economy in liquid silicone rubber injection molding

The demand and developments in the processing of RSLs are increasing concerning other materials and applying them in different fields.

Today liquid silicone rubber (LSR) injection molding has grown in importance in the marketplace thanks to the growing demand for better properties for finished rubber parts. Furthermore, its high levels of automation and productivity make it attractive.

The LSR’s ability to flow simplifies tool design, lowering costs. Its low viscosity also allows the material to flow through the mold cavity quickly and fill it. This gives the possibility of molding parts even if their perimeter has complicated shapes, such as several turns and different radii. LSR injection molding also makes it possible to consistently obtain part cross-sectional dimensions with very tight tolerances, such as diameters up to 0.76mm. Therefore, this material is a good candidate for seals or gaskets in portable communication systems, data acquisition systems, and electronic systems. Likewise, LSR has no volatiles or plasticizers that migrate.

LSR’s best property performance and short cure times make it a good choice for small molded parts. Unlike Plastic Molding Manufacturing, LSR maintains its flexibility and elasticity below -60 ºC and maintains its properties up to 232 ºC. It has resistance to environmental conditions and UV resistance.

Thanks to LSR’s liquid injection process’s economic benefits, its applications have spread to various areas. It is used in diaphragms, valves, isolators, bellows, grommets, environmental seals in electronics, cable ties in electrical/electronic equipment. It is also utilized in shock isolators, gaskets in the laboratory, and medical diagnostic equipment, among many others.

The process

Thanks to their low viscosity, LSRs can be pumped through pipes into the vulcanization process. The components (colorants, catalysts, LSR, additives, etc.) are passed through a static mixer using metering pumps. After mixing well, the material passes to the cold dosing section of the injection machine.

From the injection machine’s dosing section, the composite material is passed through a cold casting system into a hot cavity where it is vulcanized. The cold system avoids material losses in the feed, which means production with almost zero waste. It eliminates making cuts to finished parts and achieves significant savings in material costs.

The growing trend towards Silicone Injection Molding applications is demonstrated in the exhibitions and presentations that different injection machinery manufacturers have carried out in recent months.

Characteristics

  • High-temperature resistance: Outstanding material property in high-temperature conditions (more than 200 ° C) for a long time.
  • Low-temperature resistance: Excellent flexibility in low-temperature conditions (-70 ° C).
  • Low compression set: Possible to be used for applications such as sealing and gaskets due to outstanding compressed permanent stress.
  • Electrical property: with hydrophobic for water and excellent electrical insulation.

APPLICATIONS

LSR / LSM injection molding could be applied in computer/communications/consumer electronics: earplugs, smartwatch bands, bracelets, medical products.

The advantages of LSR

  • Resistant to temperatures between -50 ° C and +250 ° C preserving elastic properties
  • Neutral to smell and taste
  • Free of plasticizers
  • Excellent biocompatibility (suitable for the pharmaceutical and food industries)
  • The transparent material can be colored if desired
  • High resistance to temperatures and flashpoint
  • Beneficial reaction to fire
  • Good electrical insulation
  • Very good resistance to weather and the passage of time
  • Good compatibility with the environment

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