Medical Grade Liquid Silicone Rubber (LSR) – What Makes It Safe for the Medical Field?

The medical device industry strives to reduce costs, improve product quality and extend product lifespan. Material selection is an important consideration for engineers in the medical industry due to the impact of material performance on patient health.

Liquid Silicone Rubber (LSR) has become a popular choice for medical device manufacturers due to its biocompatibility, durability, and resistance to high temperatures, pressure, and chemical exposure.

LSR can be easily molded to meet the specific needs of different medical applications, making it an attractive option for custom silicone molded components and assemblies.

What Is Liquid Silicone Rubber?

Liquid Silicone Rubber (LSR), which has been available since the 1970s, has become a preferred material for manufacturing medical products and devices due to its highly flexible thermosetting plastic composition. The variety of LSR materials available allows designers and engineers to select the most appropriate material with the required characteristics for a specific application. Unlike thermoplastics, which melt when heated, LSR is a thermosetting material that solidifies when cured and remains in a solid state. This feature makes LSR an ideal material choice for many medical applications.

Medical grade Liquid Silicone Rubber (LSR) is selected for its multiple benefits:

High Biocompatibility: Medical-grade Liquid Silicone Rubber (LSR) is a material that is biologically inert. This means it does not release any harmful chemicals when it comes into contact with organic substances. LSR is inorganic, hypoallergenic, and it does not have any odor or taste. These properties make it suitable for various applications in the medical and food industries. Importantly, medical-grade LSR materials meet the requirements and standards set by ISO-10993, USP Class VI, and RoHS.

Sterilization Options: The ability to sterilize a medical device is vital in reusable medical applications. LSR components offer multiple sterilization options, including Autoclave, E-beam, Ethylene Oxide (ETO), and Gamma radiation processes.

Thermal Stability: LSR exhibits exceptional thermal stability when compared to other injection-molding materials used in medical devices. It maintains its stability across a broad temperature range, from -150°F to 450°F (-101°C to 232°C). Even in extreme temperatures, LSR retains its resiliency, flexibility, and ability to transmit mechanical force effectively. This makes it a reliable choice for medical applications where temperature variations are encountered.

Electrical Insulation: LSR materials demonstrate outstanding electrical insulation properties that remain uncompromised even under harsh environmental conditions. They retain their excellent insulation capabilities despite extreme temperatures, moisture, UV exposure, and ozone. This quality ensures reliable electrical isolation and protection in medical applications. By preventing electrical conductivity issues and minimizing the risk of malfunctions or failures, LSR proves to be an ideal choice for medical silicone rubber products that necessitate effective electrical insulation.

Pleasant Texture: LSR medical-injection molding procedures result in products with surfaces that feel dry and non-tacky to the touch. This characteristic enhances overall comfort. Moreover, LSR can be customized to achieve a variety of textures by modifying the surfaces within the mold cavity. This versatility allows for the creation of medical products with different tactile experiences, catering to specific user preferences and optimizing patient comfort

The advantages make LSR an excellent material for medical industry injection molding.

Medical grade Liquid Silicone Rubber (LSR) for Healthcare applications

In the realm of medical device manufacturing, there is a wide range of silicone materials available that meet various standards. These include medically non-implantable, medically restricted implantable, and medically unrestricted implantable materials.

Advancements in material science have made non-implantable materials more accessible at different hardness levels. This enables the fabrication of medical devices with varying degrees of hardness.

Medical grade LSR is divided into three categories: limited exposure, prolonged exposure, and permanent contact.

Limited exposure: refers to devices that make contact with the skin, mucosal membranes, or compromised and breached surfaces. It has a short service life of 24 hours or less.

Prolonged exposure: Also known as “healthcare grade,” this material undergoes tests such as hemolysis, genotoxicity, toxicity, and intramuscular implantation with histopathology. It is designed for surface or implant contact lasting more than 24 hours and up to 30 days.

Permanent contact: Referred to as “long-term implantable,” this medical silicone rubber undergoes physicochemical and biological testing that surpasses the protocols for prolonged exposure. It includes testing for carcinogenicity, chronic toxicity, and developmental toxicity. Due to its high level of purity and specialized properties, this type of silicone is generally more expensive and not typically used in food-grade applications.

What is the difference between Medical Grade Liquid Silicone Rubber and alternative materials?

Let’s explore the key differences between medical grade LSR and other options.

Stability and Water Repellency: Medical grade LSR offers tremendous stability and water repellency. This means that the cured material remains unaffected even when it comes into contact with the skin or other fluids. Unlike materials like latex, LSR is non-allergenic, making it safer for patients.

Hygienic Qualities: Medical Grade LSR has inherent hygienic qualities that help resist the growth of bacteria and fungi. This is crucial in medical applications where maintaining a sterile environment is essential. The hygienic properties of LSR contribute to the overall safety and reliability of medical devices.

Flexibility and Softness: Medical Grade LSR is known for its exceptional flexibility and softness. These qualities ensure patient comfort, especially when the material is used in medical devices that come into direct contact with the skin. LSR’s flexibility also prevents the material from sticking to wounds, promoting easier wound care and reducing patient discomfort.

Temperature Resistance and Elasticity: Medical grade LSR can withstand a wide range of temperatures. It remains stable and functional even in high-temperature environments, making it suitable for various medical applications. Additionally, LSR maintains its elasticity at very low temperatures, allowing it to retain its flexibility and performance in extreme conditions.

Compression Set and UV Resistance: Medical Grade LSR exhibits a low compression set, meaning it resists permanent deformation when subjected to force or pressure. This ensures the long-term durability and reliability of LSR-based medical products. Moreover, LSR shows excellent resistance to ultraviolet (UV) radiation, protecting it from degradation and ensuring its stability over time.

Comparison with Alternative Materials: When compared to alternative materials like thermoplastic elastomers (TPEs), LSR has distinct advantages. While LSR may have a higher cost and longer cycle time for the molding process, it offers unique benefits. LSR allows the combination of multiple components, reducing production costs and complexity. It also provides superior strength, elongation, tear strength, and compression at temperature extremes, making it an ideal choice for high-precision medical components.

The benefits of selecting medical-grade LSR over other options include:

  • FDA biocompatibility
  • Resistance to chemical and bacteria
  • Excellent transparency, which allows light transmittance and illumination
  • Gas permeability
  • Clarity
  • Used as a no-slip surface
  • High elongation
  • Superior dielectric strength
  • Superior tensile strength, elongation, tear strength, and compression at temperature extremes
  • Ability to function in extreme temperatures
  • Low compression set at wide temperature ranges

LSR is a superior material choice for producing high-precision medical components and devices with intricate geometries that demand exceptional accuracy, surpassing high-consistency rubber (HCR) and other elastomers.

LSR Injection Molding For Medical Devices

Liquid Silicone Rubber (LSR) can undergo liquid injection molding (LIM) to facilitate its processing. The liquid raw material is formed by combining two separate components in a 1:1 ratio, and it is injected into a hot mold through a cold-runner system. Curing occurs rapidly, taking only a few seconds, which enables quick cycling and high-volume production.

LSR injection molding is well-suited for manufacturing intricate geometries due to its design and tooling flexibility. It allows for the consolidation of multiple functional features into a single part. Additionally, it provides notable advantages in terms of product reliability and overall cost-effectiveness.

LSR is chosen by product designers for the design and manufacture of medical silicone parts and devices across a wide range of applications. Some specialty medical fields that utilize LSR medical injection molding include Pacemakers, defibrillators, shunt systems, Respiratory care products, inhalers, infusion therapy, drug delivery systems, peristaltic pump sets, diabetes care, diagnostic equipment, dental care devices, medical devices, blood dialysis, catheters, disposable fluid transfer manifolds and closure assemblies, breastfeeding, bioreactors, pharmaceutical applications. general surgery, plastic surgery, ophthalmology, wearable health monitoring devices, dialysis, neurosurgery, and ear, nose, and throat procedures.

When selecting a material for medical projects, the cost of LSR may be a concern. However, many medical product and device manufacturers compromise on product design and performance in order to save on up-front tooling costs.

Choosing medical-grade LSR ultimately pays off in terms of improved quality and better performance.

Over time, medical products and devices molded from LSR can withstand challenging conditions and maintain their integrity.

Over-molding Liquid Silicone Rubber for medical devices

Overmolding is a manufacturing process that involves using liquid injection molding to apply a layer of LSR onto a finished component made of a different material, typically a thermoplastic or metal substrate. This process can be performed semi-automatically or fully automatically. Overmolding is suitable for smaller production quantities or situations where an additional step is required to incorporate bonding technology due to the nature of the substrates.

  • Advantages of Overmolding:
  • Composite products can be customized by combining thermoplastic, metal, LSR components, and silicone tubing.
  • Suited for medium size production runs
  • Eliminates the risk and cost associated with secondary assembly
  • Greater design latitude in applications
  • Cost-effective solutions

In the medical market and healthcare industry, manufacturers need materials and processes that enable them to produce products with precise tolerances, sterilization capabilities, and surfaces with a soft-touch feel and various colors.

Surgeons and other clinicians have shown a growing interest in medical devices and surgical instruments with soft-touch handles, as they improve grip and ergonomics. Overmolding enables the creation of handles that are specifically shaped to fit comfortably in the hands of the end user or interact with attachments.

The overmolding process begins by applying Liquid Silicone Rubber (LSR) over a metal shaft to achieve the desired shape. Additionally, a thermoplastic material is used to create the soft-touch handle.

This manufacturing method allows product designers to create parts with smooth and seamless surfaces, eliminating gaps that can trap contaminants. The transparent nature of LSR enables surgeons to see through the instrument and work with enhanced precision hermoplastic material is used to create the soft-touch handle.

The overmolding technique has gained popularity in the medical market as device manufacturers recognize its potential advantages.

This process is particularly well-suited for products or devices that require handles, biocompatibility, heat resistance, or chemical resistance. While certain soft thermoplastics like TPE can mimic some characteristics, LSR surpasses other materials in terms of durability, biocompatibility, resistance to cold, heat, chemicals, and UV light. LSR also offers unparalleled flexibility and moldability, making it an ideal choice for medical applications.

Cost Savings Manufacturing with LSR

Manufacturing with Liquid Silicone Rubber (LSR) can lead to significant cost savings. Here are several ways in which using LSR in the manufacturing process can be cost-effective:

Reduced Production Time: LSR has a fast curing time compared to other materials used in manufacturing. It can be cured in a matter of minutes, allowing for shorter production cycles and faster turnaround times. This efficiency translates into increased productivity and reduced labor costs.

Simplified Production Process: LSR can be processed using injection molding, which allows for high-volume production, minimizing manual labor and reducing the overall production costs. The simplicity of the process also reduces the chances of errors or defects, resulting in less waste and rework.

Simplified Assembly: LSR’s flexibility and compatibility with other materials simplify the assembly process. Components made from LSR can be easily integrated with different parts, reducing the number of assembly steps and minimizing labor costs. The seamless integration of LSR components also enhances the overall product quality and reliability.

Long-term Cost Benefits: Products manufactured with LSR exhibit durability and longevity, reducing the need for frequent replacements or repairs. This translates into cost savings over time, as maintenance and replacement expenses are minimized.

Regulatory Compliance: Utilizing medical-grade LSR can help streamline the regulatory approval process for medical devices and products. By meeting the stringent requirements and standards, manufacturers can avoid costly delays and rework associated with non-compliance. The upfront investment in using medical-grade LSR can result in long-term cost savings by avoiding potential regulatory setbacks.

By taking advantage of these cost-saving benefits offered by LSR, manufacturers can optimize their production processes, increase profitability, and gain a competitive edge in the market.

To learn more about medical-grade Liquid Silicone Rubber or receive a free quote, contact a A1 Silicones representative today.

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