Thermoplastic elastomers (TPEs) are a family of repeatable melt-processable rubber-like materials that become soft when given enough heat and harden again when cooled. Liquid silicone rubber (LSR) is a liquid product based on silicone resin, which forms a fixed shape after being heated and vulcanized. In short, TPE is a thermoplastic polymer material and LSR is a thermoset polymer material. So, what is the difference between TPE and LSR?

1. Design
Touch, color and shape are important factors that need to be considered in design and development, so that the product can meet the aesthetic needs while being comfortable to grip and easy to shape, so that it can stand out among many competing products (1) Touch:
TPE can make the surface of the product have different touch such as silky smooth, slightly sticky or easy to grasp; LSR has a skin-like touch such as dry, smooth, soft and elastic. LSR can reflect fine surface texture better than TPE.
(2) Color:
Both TPE and LSR are available with full spectrum color options for transparent, translucent and opaque colors. LSR can prevent dust adsorption and is suitable for wearable devices. And TPE can achieve a variety of color effects, including metallic, pearlescent, wood texture, marble and other multiple effects.
(3) Shape:
LSR flows easily into molds with different wall thicknesses and can fill longer, thinner parts of the mold. Although TPE can reduce material viscosity when processed at high shear rates, TPE must be "extruded" into the mold to be fully filled, especially for formulations with a hardness greater than Shore 50A. When designing parts with TPE, try to keep the wall thickness of the part uniform and avoid sharp corners.

2. Production
Product design and development also need to consider raw material costs, technological processes and comprehensive production costs to balance cost-effectiveness and improve competitiveness:
(1) Raw material cost:
Typically the unit cost of LSR and other engineering elastomers is higher than that of standard elastomers, and the specific gravity of LSR is 20% higher than that of TPE (±1.12g/cm³ vs. ±0.89g/cm³). LSR is a suitable choice when product applications require materials that do not easily soften at sustained high temperatures. However, TPE has more advantages than LSR in recycling and reprocessing, and is more environmentally friendly and economical.
(2) Overmolding:
Since LSR needs to be cured at high temperature, the overmolded substrate needs to be a high temperature resistant thermoplastic material, or surface treatment with primer and adhesive is used to coat LSR on the substrate. TPE products, on the other hand, can be firmly bonded to thermoplastic substrates by direct overmolding without the need for primers or adhesives.
(3) Mold cost:
Molds used to make LSR parts require more precision and expertise than those used to make TPE parts to avoid flash. In addition, the mold needs to have a precise vent design or vacuum so that the gas generated during the chemical vulcanization process can be discharged in time. TPE processing uses conventional in-line single-screw injection molding equipment in the industry, which allows more flexibility in the technical design of products and molds.
(4) Cycle time:
The cooling time of TPE is faster and does not require secondary processing or vulcanization, which can improve the efficiency of manufacturing. LSR products require post-vulcanization treatment, which is shaped in a high temperature environment and maintained for a certain period of time to achieve the final design result. However, based on the size of the part, the low viscosity of LSR enables injection filling of a multi-cavity mold, which greatly compensates for the lack of production efficiency.

3. Performance
(1) Chemical resistance:
LSR is resistant to cleaning and disinfecting chemicals, but not concentrated solvents (gasoline, mineral spirits) and acids (sulfuric, carbonic, citric). TPE is resistant to a variety of chemicals, and different formulations can resist different chemicals.
(2) Heat resistance:
The LSR can withstand continuous high temperatures in excess of 200 degrees Celsius, making it an excellent choice for the medical industry for use on cautery instruments or any equipment isolation panels that are exposed to repeated autoclaving. Some medical-grade TPEs can be sterilized in high-pressure steam at up to 135 degrees Celsius for 15 minutes, but most TPEs tend to soften at extremely high temperatures due to their inherent thermoplasticity. At room temperature, the compression set properties of LSR and TPE are comparable. LSR has better compression resilience as the temperature rises under compressive loads, such as dishwasher seals.
(3) Barrier performance:
TPE has excellent air and moisture barrier properties, can effectively prevent microorganisms and pathogens, and is suitable for disposable gloves, IV bags, beer metal bottle cap liners and other applications. Silicone itself is a breathable material and is suitable for applications such as wound coverings and contact lenses.
(4) Tear resistance:
The tear and tensile strengths of LSR are relatively low, and even a small tear can cause problems with product performance. And TPE can meet the high tear strength required for diapers, sports elastic belts and other products.
(5) Anti-ultraviolet:
LSR itself has excellent UV resistance, and TPE, with the help of UV stabilizers, can also resist the negative effects of UV rays.
(6) Biocompatibility:
LSR has excellent biocompatibility and purity, and is suitable for medical devices and FDA Class III, USP Class VI implantable products (including catheters, gastric feeding tubes, heart valves and stents, etc.). The biocompatibility of medical-grade TPE is comparable to that of LSR, but in some cases, TPE is less expensive to produce and an economical alternative for many disposable and drug delivery products.