The medical device industry has a wide range of products and applications that suit medical molding, and choosing the right material from the start will save significant time and resources.
Often, it’s easy to be confused about which “soft material” you should choose for your application when there are so many options, especially when comparing TPE to LSR. The best first step for medical applications is to consider the intended environment of the application. Understanding those conditions will quickly help you narrow your material choices.
What does your molded part require: TPE or LSR?
TPE: A great choice for a variety of medical device applications and some implantable devices, cost effective process, recyclable during the molding process, and has a high range of “softness”.
LSR: With high chemical and heat resistant properties as well as less diverse reactions to skin contact, this material is ideal for implantable device applications.
TPE material basics
TPE stands for Thermoplastic Elastomer and is a flexible material that can be stretched repeatedly to over twice its length with a range of softness on a durometer scale. The most common general application for TPE is to “over-mold” it onto a substrate for a “soft touch” feel. Typically, TPE’s are most commonly used on handles or areas that would be physically touched.
Traditionally, there were 6 primary TPE types categorized into two generic classes,
- Block copolymers (styrenics, copolyesters, polyurethanes, and polyamides),
- Thermoplastic/elastomer blends & alloys (thermoplastic polyolefins and thermoplastic vulcanizates).
However, over the past few years, there have been two additional emerging technologies;
- Metallocene-catalyzed polyolefin plastomers & elastomers
- Reactor-made thermoplastic polyolefin elastomers.
A major benefit of TPE over LSR is its recyclability. This allows a “re-molding” opportunity with the TPE without chemically changing the material; this differentiator, along with a less expensive molding process than LSR, typically results in lower production costs.
Medical device manufacturers increasingly turn to thermoplastic elastomers (TPEs) for applications that require flexibility or rubber-like elasticity. These compounds have replaced alternative materials such as thermoset rubber and PVC in standard applications, including tubing, bags, pouches, drip chambers, masks, cushions, syringe tips, ventilator bags, luers, stoppers, gaskets, seals, and dropper bulbs. As designers have come to appreciate the value of TPEs, more and more are using these elastomers for new applications.
TPE growth in medical devices stems from its advantages over alternative materials. The most obvious advantages stem from the fact that TPEs are thermoplastics. They process more efficiently and economically than thermoset rubber, provide greater design freedom, exhibit a wider range of color options, and, unlike rubber, can be recycled.
At the same time, TPEs provide device manufacturers with a means of obtaining comparable or even superior properties while avoiding problems associated with certain alternative materials.
LSR material Basics
LSR stands for Liquid Silicone Rubber and is typically either injection molded or compression molded. LSR is a thermosetting polymer, which means that once it’s molded, it cannot be recycled like the thermoplastic counterpart in TPE. The main raw material is sand, or silicon dioxide, which is then combined with methyl chloride to create different types of silicone, including liquid silicone rubber.
Unlike TPE, LSR uses a two-component reactive chemical that is mixed, heated, and then cured into a rubber form. Because the LSR components are shipped in sealed containers and processed with a closed system, there are fewer issues with dust and moisture contaminants.
In medical molding, LSR use has increased over the years for implantable devices, mainly because it cures completely during the molding process. This means that the device will not leach chemicals and potentially cause adverse reactions in the patient. Because LSR has extremely high heat and chemical resistance, it can handle rigorous sterilization processes, making it a good fit for many medical applications.
Choosing the right supplier for tpe or lsr
Because of the key differences between thermoplastic elastomers (TPE) and thermosets (LSR), choosing the right supplier for your application can be difficult, depending on how many implantable vs. non-implantable products your company produces. Often, the molding supplier will focus on either thermoplastic or thermoset materials for the majority of their business, with some companies having a few machines/processes for their non-dominant material.
If your company mainly produces non-implantable products, then it’s a good idea to focus on a TPE molding expert who has all of the certifications and cleanroom facilities to handle most of your product needs. This also means that implantable products ideal for an LSR application should be sourced from a company that focuses primarily on LSR molding.
Crescent’s Medical molding capabilities
Crescent Industries has been providing TPE and thermoplastic solutions to the medical industry for over 80 years. Our application expertise spans a wide range of uses in the medical, dental, and pharma industries, leveraging ISO 13485 certification and Class 7 clean room operations, providing assembly and packaging services. Crescent Industries continues to expand its technology and is dedicated to providing the markets we serve with the highest-quality products that solve some of the most challenging applications.
Contact us today to discover how Crescent can help with your next injection molding project!