How to Choose? An In-Depth Analysis of Silicone and TPE

作者luxeforgeyan@gmail.com

1. Difference in Tactile Feel Between Silicone and TPE

Generally, silicone has a harder feel, whereas TPE can be very soft. Of course, silicone can also be made quite soft, but this significantly increases the cost.

Therefore, at present, it can be squeezed, but it will feel harder than TPE.

2. Difference in Material Properties Between Silicone and TPE

Silicone has better performance than TPE. Because the material is slightly harder, silicone is superior in some aspects; certain artificial skin textures and details can only be rendered with silicone, while TPE does not perform as well.

3. Difference in Tensile Strength Between Silicone and TPE

Depending on the formulation, silicone can be stretched 3-5 times its original size, while TPE can be stretched 6-8 times. Therefore, TPE has better tensile strength and allows for more extreme movements.

4. Difference in Weight Between Silicone and TPE

For the same volume, silicone is heavier than TPE. The specific weight depends on the manufacturer’s process level and internal structure.

5. Difference in Aging Resistance Between Silicone and TPE

Silicone is resistant to high and low temperatures, as well as acids and alkalis. Apart from strongly corrosive substances, silicone reacts with almost no other material. TPE is not resistant to high temperatures, and its aging resistance is inferior to that of silicone products.

6. Difference in Odor Between Silicone and TPE

Silicone is completely odorless. TPE will have a slight smell of chewing gum or added fragrances. If it has a strong fragrance, it is not recommended for purchase due to the risk of fragrance allergies.

7. Difference in Composition Between Silicone and TPE

  • 7.1 Silicone is divided into inorganic silica gel and organic silicone compounds.
    • Inorganic silica gel is a highly active adsorption material, typically prepared from sodium silicate and sulfuric acid through a series of post-treatment processes like aging and acid washing.
    • Silica gel is an amorphous substance with the chemical formula mSiO₂·nH₂O. It is insoluble in water and any solvents, non-toxic, tasteless, and chemically stable. It does not react with any substance except for strong alkalis and hydrofluoric acid.
    • Organic silicone refers to organosilicon compounds, which are compounds containing Si-C bonds where at least one organic group is directly attached to a silicon atom.
    • It is also customary to consider compounds where organic groups are linked to silicon atoms through oxygen, sulfur, nitrogen, etc., as organosilicon compounds.
    • Organosilicon is mainly divided into three categories: silicone rubber, silicone resin, and silicone oil.
  • 7.2 TPE has many varieties, usually modified from styrenic elastomers.
    • What is commonly referred to as TPE is a blend-modified material, TPES, based on styrenic block copolymers (SBC).
    • In fact, there are many types of TPE (including TPES, TPV, TPU, TPEE, TPO, etc.). The TPE discussed in this text mainly refers to TPES elastomers modified from SBC.

8. Difference in Appearance Between Silicone and TPE

  • 8.1 The chemical formula for inorganic silica gel is xSiO₂·yH₂O. It appears as transparent or milky-white granular or bead-like solids.
    • There are many types of silicone, including silicone oil, silicone rubber, and silicone resin, so their appearances vary, ranging from liquid to solid blocks or granules.
  • 8.2 TPE is a composite material with no fixed composition. However, its appearance is generally transparent or white pellets.

9. Difference in Performance Between Silicone and TPE

  • 9.1 Heat Resistance
    • TPE is generally heat resistant up to 80-100°C.
    • Silicone is generally heat resistant up to 100-150°C.
  • 9.2 Resilience and Compression Set
    • TPE has a physically cross-linked structure. No matter how good its physical properties are, TPE will exhibit some degree of permanent deformation (compression set).
    • Silicone is usually cross-linked by adding a coupling agent. Both solid and liquid silicones are chemically cross-linked and have excellent resistance to permanent deformation. In other words, silicone has higher elasticity and better resistance to deformation than TPE.
  • 9.3 Food-Grade Properties
    • For food-grade materials, specific testing methods vary by country and region. However, the current basic understanding is as follows:
      • The composition of silicone is relatively simple. Most silicones can pass residual tests with oily solvents (like olive oil, n-hexane, etc.) and comply with the US food-grade standard FDA 21CFR 177.2600 and the German food contact material standard LFGB.
      • TPE is a multi-component blended system. The TPE base resin and softening oil may contain residual small organic molecules that are easily soluble in oily liquids.
      • Currently, except for a few specific material formulations that can meet 21CFR 177.2600 and LFGB, most TPEs, especially those with low hardness, cannot pass these two food-grade tests.

10. Molding Equipment for Silicone and TPE

  • 10.1 Silicone is thermosetting. Most liquid silicone rubbers (LSR) can be molded using a hydraulic press, and some LSRs can be molded using an injection molding machine.
  • 10.2 TPE is thermoplastic. It is mostly molded using injection molding machines or extruded using extruders.

11. Scrap and Recycling of Silicone and TPE

  • 11.1 TPE scrap can be 100% recycled.
  • 11.2 Waste silicone is difficult to recycle.

12. Overmolding of Silicone and TPE

  • 12.1 TPE can be effectively overmolded and bonded with most hard plastics such as PP, ABS, PC, PA, PS, PE, SAN, etc., without the need for adhesives.
  • 12.2 For overmolding silicone onto hard plastics, an adhesive is typically applied first, followed by injection molding for bonding. However, it is said that modified silicones are now available abroad that can be directly overmolded and bonded without prior application of adhesive.

13. Cost Comparison of Silicone and TPE

  • 13.1 The price of low-end solid silicone is comparable to that of low-end TPE, around 20,000 RMB/ton or less.
  • 13.2 The price of mid-to-high-end (liquid) silicone rubber is close to that of high-end TPE, approximately 30,000-50,000 RMB/ton.