Silicone elastomers have long been a popular material for medical devices and medical device components due to their durability, ease of molding by many methods, wide temperature range, chemical inertness, high tensile strength, vast range of available durometers, low toxicity, and compatibility with many sterilization methods. Furthermore, silicone is compatible with human tissue and body fluids, has a very low tissue response when implanted, and does not support bacteria growth – making it a perfect option for implants due to its excellent biocompatibility. Additionally, medical-grade silicones have undergone stringent purity and biocompatibility testing that make them suitable for short and long-term usage.

Why is Silicone a Great Molding Material?

Silicone elastomers are available in two commercial forms: Liquid Silicone Rubber (LSR) and High Consistency Rubber (HCR). LSR has a lower viscosity than HCR and is, therefore, often processed via injection molding. Due to its higher viscosity and more challenging handling properties, HCR is typically processed using compression and transfer molding methods, which are more labor-intensive. LSR is often the preferred choice given the lower capital costs and labor associated with processing this elastomer. For this reason, this article will focus on the properties that make LSR a great molding material.

LSR has excellent properties and material handling characteristics that make it a great choice for molding. Below is a deeper dive into some of these key properties. It should be noted that there are different grades of silicones with varying material properties; however, the following generally represents most LSR formulations.

  • Low Viscosity: the low viscosity of LSR makes it a great silicone material for making medical devices via injection molding, since the LSR can easily flow into and completely fill molds with relatively low injection pressures, even those with small, complex, or high-tolerance features. A lower viscosity also makes it easier for manufacturers to mix in additives including colorants, desiccants, barium, and pharmaceuticals such as hormones or steroids. For these reasons, LSR is a great option for medical devices such as combination products.
  • Quick Cure Rate: one of the benefits of LSR is that it cures faster than most other rubber materials – in some cases in only seconds. Additionally, due to the highly automated nature of injection molding and the potential for 24/7 manufacturing, high volumes of LSR products can be produced in a short period of time – adding to its popularity.
  • Low Compression Set: this property is a measure of how well a material can resist permanent deformation under a constant strain. LSR has low compression set, meaning LSR products are able to retain their original shape and elasticity even when compressed for long durations.
  • Electrical Resistance: LSR formulations are often used in high-voltage and electrical equipment due to its electrical resistance and ability to act as an insulator. Many materials degrade when exposed to electrical and other environmental stresses over time, however, this is not the case for LSR.
  • Broad Temperature Range: compared to other materials, LSR has excellent thermal stability. LSR blends are able to withstand high temperatures without deforming or melting, making them a great choice for parts for the automotive sector. As for low temperatures, LSR maintains its flexibility and does not become brittle and vulnerable to breaking like thermoplastic elastomers.
  • Chemical Resistance: LSR is chemically inert and is resistant to a variety of chemicals. Its biocompatibility is unmatched, making LSR a great option for medical devices, implantables, and other healthcare applications.
  • Longevity: LSR is known for its resistance to UV, weather, and other environmental conditions that tend to age materials, leading to longer life spans for LSR products.

ProMed’s Silicone Molding Capabilities

ProMed was founded in 1989 to address an industry need for cleanroom manufacturing of silicone components, specifically those having a medical application. We have garnered a reputation as the world benchmark of implantable silicone components and assemblies – and are one of few companies in the world to provide contract manufacturing of drug-eluting products.

ProMed has expertise in working with the full spectrum of silicones covering a wide range of properties and characteristics. We will assist in your material selection to help ensure all design requirements are met. Our manufacturing facilities and equipment are designed for a single purpose—to mold medical and implantable silicone, combination components, and bio-material grade plastics with uncompromising quality and service. We currently have four divisions that are located within two manufacturing sites. All are certified class 10,000 / ISO Class 7 cleanrooms.

We can identify the right manufacturing solution for any project. We have extensive experience in a wide range of injection molding techniques including:

  • Automated Injection Molding
  • Multi-cavity tooling
  • Micro molds and micro molding
  • Servo-controlled de-molding capabilities
  • Insert molds, overmolds, and automation integration
  • Transfer molding
  • Compression molding

Contact ProMed today at 763-331-3800 to discuss your next medical molding project.

Why is Silicone a Great Molding Material?
Article Name
Why is Silicone a Great Molding Material?
Why silicone is a great molding material including quick cure times, low viscosity, superb longevity, and strong chemical and electrical resistance.
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ProMed Molding
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