Comparing Elastomers for Medical Applications: TPE vs. Silicone

Application in the medical industry in recent years has become a major development trend and direction of TPE materials, traditional rubber (silicone) material processing cycle is long, the safety of PVC is questioned, which for the TPE in the medical industry to show its prominence in the history and industry opportunities. In recent years, the industry’s demand for medical grade TPE is also on the rise.

Manufacturers have a variety of materials to choose from when designing parts, but the most popular and widely used material (especially in the medical industry) is liquid silicone rubber (LSR), more commonly but somewhat inaccurately referred to as silicone. This is because this versatile material is durable and pliable, soft to the touch and, most importantly, biocompatible (assuming it is medical grade LSR). For many, it is the preferred choice for a variety of components.

Why is LSR the material of choice for medical applications?

Medical grade liquid silicone rubber (LSR) is the material of choice for medical applications due to its flexibility, heat resistance, chemical resistance, and biocompatibility.LSR is widely used in prosthetic devices, medical equipment such as catheters, syringes, and breathing tubes, as well as in wearable devices and consumer products. Unlike commercial LSR, medical LSR is cured with a platinum-based catalyst to ensure safe use by eliminating harmful byproducts. Medical device manufacturers are required to obtain approval based on the type of human exposure and duration of use as specified by the FDA, in accordance with ISO standards.

3D-Printed Silicone vs. LSR

	Shore A Hardness	Tensile Strength	Elongation in %	Tear Strength
3D-Printed Silicone	20A	623.7 psi (4.3 MPa)	815	33.1 lbf/in (5.8 N/mm)
	35A	1,508.1 psi (10.4 MPa)	1,000	58.2 lbf/in (10.2 N/mm)
	50A	1,290.8 psi (8.9 MPa)	650	57.1 lbf/in (10 N/mm)
	60A	1,363.4 psi (9.4 MPa)	360	85.7 lbf/in (15 N/mm)
LSR	51A	1,200 psi (8.3 MPa)	500	271 lbf/in (47.5 N/mm)

Table source for 3D-printed silicone data: Spectroplast.com

Designing Silicone Parts for Manufacturability

Deciding between injection-molded LSR parts and those 3D-printed with SAM depends on several factors in your medical application. The good news is that product designers seeking quick turnarounds no longer need to resort to alternative polymers, as both options can offer high performance and part quality.

However, even with a robust material, success hinges on adhering to recommended guidelines for the specific manufacturing process. SAM, like most 3D printing technologies, requires attention to temporary support structures to prevent curling and deformation on horizontal surfaces. Issues with tall, skinny walls and small-diameter holes, especially those with long aspect ratios under 0.040 in. (1mm), may arise.

Injection-molding LSR, while different from traditional thermoplastic molding, is relatively straightforward. The material flows freely, making thin walls less of a concern compared to plastics like polyamide and PEEK. Sink, common in thick sections of other materials, is not an issue, but flash at parting lines can occur more readily with LSR. Designers should be cautious of sharp edges, as LSR does not favor them; delicate parts, in particular, may tear during mold removal, necessitating rounded internal corners. Despite these considerations, the flexibility of LSR allows for easy accommodation of moderate undercuts and ‘bump off’ features. Injection-molded LSR also offers versatility in color options, providing designers with a wide range of choices