Comparison of TPE and Silicone for Medical Applications

When designing components for medical applications, manufacturers face a variety of material choices. However, liquid silicone rubber (LSR), often referred to simply as “silicone,” stands out as one of the most popular and versatile materials, particularly in the medical industry. Known for its durability, flexibility, and softness, LSR also boasts a critical characteristic for medical applications: biocompatibility, assuming it is medical-grade. At YJCPolymer, we specialize in LSR production, ensuring high-quality silicone solutions that meet the stringent requirements of the medical sector.

For manufacturers and designers considering LSR, a common question arises: should they choose plastic injection molding or opt for 3D printing when producing silicone parts? This decision is influenced by several factors, including production volume, part geometry, desired accuracy, and surface finish. While traditional plastic injection molding is widely used for LSR, advancements in 3D printing technologies are beginning to open new possibilities for low-volume production and prototyping. In this article, we will explore the pros and cons of each approach, compare the available materials, and provide guidance on selecting the most appropriate process for specific medical applications.

Why Choose LSR for Medical Applications?

In the medical field, LSR is a material of choice due to its outstanding properties. Its flexibility, chemical resistance, heat tolerance, and biocompatibility make it ideal for a wide range of medical devices and components. Medical-grade LSR is commonly used for prosthetics, including breast and ear implants, as well as orthotics like braces and arch supports. Intravenous tubing, catheters, syringes, breathing tubes, and insulin pumps are also frequently manufactured using LSR. Additionally, silicone is a key material in wound dressings, valve seals, and gaskets for medical equipment, providing an essential solution where durability and performance are critical.

What distinguishes medical-grade LSR from other types of silicone is primarily the curing process. While commercial LSR may utilize hydrogen peroxide and high temperatures, which can leave behind by-products harmful to human health, medical-grade LSR uses a platinum-based catalyst and a secondary treatment such as UV light or baking to remove harmful residues. This ensures that the material is safe for use in contact with the human body, though sterilization is still required for most medical applications.

Manufacturers of medical devices must carefully specify the type of human contact their products will have, as this impacts the regulatory approval process, including FDA clearance. The specific use case—whether the device will have direct, prolonged, or permanent contact with the human body—determines the required biocompatibility testing, as outlined in ISO 10993-1: 2018 and other international standards.

Comparing Silicone with Other Thermoplastic Materials

When it comes to choosing between silicone and other thermoplastic elastomers (TPEs), manufacturers often compare LSR with materials like thermoplastic polyurethane (TPU) and thermoplastic elastomers (TPE). Each material has its own strengths and weaknesses, but none can fully replicate the performance and properties of LSR.

Below is a comparison of LSR, TPE, and TPU in terms of key properties relevant to medical applications:

As demonstrated in the table, LSR outperforms TPE and TPU in several areas, particularly biocompatibility, chemical resistance, and temperature resistance. However, the lower cost and ease of processing of TPE and TPU make them attractive alternatives in specific applications where the extreme properties of LSR are not required. Additionally, proprietary 3D printing resins have been developed that mimic some of the qualities of LSR, providing manufacturers with more affordable options.

Despite these alternatives, LSR remains the material of choice for many medical applications due to its superior properties and ability to withstand the rigors of both human contact and the medical environment.

Choosing the Right Manufacturing Process for LSR Parts

The decision to produce LSR parts using plastic injection molding or 3D printing depends on a variety of factors, including the volume of parts needed, the complexity of the design, and the required lead time. For high-volume production, injection molding is the preferred method due to its speed, accuracy, and cost-effectiveness. Molding can produce high-quality parts with fine surface finishes and is ideal for producing large quantities of consistent components. However, injection molding can be less cost-effective for small runs or prototyping, and the setup costs associated with tooling can be substantial.

For low-volume production or rapid prototyping, 3D printing has emerged as a promising alternative. Additive manufacturing enables quick production of functional prototypes, allowing designers to iterate on their designs rapidly. It also offers greater design freedom, allowing the creation of complex geometries and customized features that may be difficult or costly to achieve using injection molding.

At YJCPolymer, we understand the challenges that manufacturers face when choosing between injection molding and 3D printing. We provide expert advice and support to ensure that our customers select the right materials and manufacturing processes for their specific needs. Whether you’re developing a new medical device or producing a small batch of parts, we are here to help.

Designing for Manufacturability in Silicone

When designing silicone parts for medical applications, manufacturability plays a critical role in ensuring that the parts meet both functional and regulatory requirements. Whether you’re using injection molding or 3D printing, it’s essential to follow best practices for part design.

For 3D printing, one of the main concerns is the need for temporary support structures. These structures are necessary to prevent parts from curling or deforming during the printing process, especially for horizontal or near-horizontal surfaces. Additionally, designs with tall, thin walls or small holes under 0.040 inches (1mm) in diameter can be problematic due to limitations in additive manufacturing technologies.

Injection molding, on the other hand, has its own set of design considerations. LSR flows more freely than thermoplastics, which makes thin walls less of a concern compared to materials like nylon or PEEK. However, care must be taken to avoid excessive flash at parting lines, as LSR is more prone to flashing than other materials. Additionally, LSR does not handle sharp edges well, so rounded corners and internal features are recommended to reduce the risk of tearing during the molding process.

Despite these challenges, both manufacturing methods can produce high-quality silicone parts when designed properly. At YJCPolymer, we provide comprehensive design support to help our customers optimize their silicone parts for manufacturability, ensuring both functionality and cost-effectiveness.

Conclusion

In the medical industry, liquid silicone rubber (LSR) is a material of exceptional value due to its biocompatibility, durability, and versatility. Whether you choose to manufacture LSR parts using traditional injection molding or opt for innovative 3D printing methods, the decision ultimately depends on the specific requirements of your project. At YJCPolymer, we offer a wealth of expertise in both manufacturing processes and materials selection, guiding our clients toward the best solutions for their medical applications. If you are looking for high-quality LSR parts or assistance with material selection, don’t hesitate to reach out to our team for personalized guidance and support.