Silicone is composed of high-performance materials with a unique molecular structure. It comes in different forms, including solids, liquids, semi-viscous pastes, greases, oil, and rubber. The most common type that we are familiar with is silicone rubber.
Most silicone products are made through silicone molding. The process has two types: compression molding and liquid silicone rubber molding. Compression molding uses heat and pressure to create a part. Liquid silicone rubber molding, on the other hand, uses a two-part silicone-based polymer that has a strong chemical bond. This creates parts that are heat resistant and used mainly in automotive, appliances, food, textiles, and consumer goods.
Facts About Silicone Rubber
Silicone is a versatile material. It is a semi-organic synthetic material that consists of chains of silicon and oxygen atoms. It is different from rubber, which is made of carbon and hydrogen atoms.
Silicone is different from the chemical element, silicon. Its molecular structure contributes to the material’s properties. The backbone of siloxane bonds in silicone is responsible for its thermal conductivity. Thus making it extremely heat resistant and thermally stable during silicone molding. On the downside, while it is flexible and stable, the silicone chain is weak and tears easily.
Silicone parts
Types of Silicone Rubber Used in Silicone Molding
The most common application of silicone molding is in creating medical components. The silicone rubber used in this application can be categorized based on the size, volume, and molding techniques. Here are the two types specifically used in silicone molding.
High Consistency Rubber or HCR
HCR is like peanut butter and uses platinum or peroxide as catalysts. This material can be formed into a part using compression molding or transfer molding. In compression molding, the material is placed between two plates. It may be old technology but still effective in low volume production.
Transfer molding is somewhat the same as compression molding. The only difference is the press transfers the material through a runner, sprue, and gate system to the cavity of the mold. It is more efficient and less prone to contamination. That is why this technique is used for low to mid-range production.
Liquid Silicone Rubber or LSR
Liquid injection molding is a fairly recent addition to silicone molding that uses liquid silicone rubber. LSR has a syrupy consistency and uses a platinum catalyst. LIM can be further categorized into associated technologies like overmolding, two-shot molding, and micromolding based on how silicone molding is done.
Advantages of Silicone Rubber
Here are some of the advantages of silicone rubber:
- Heat resistant – silicone rubber offers outstanding high-temperature resistance. This thermal suitability means it can retain its structure and properties through a wide temperature range.
- Hygienic – there is a reason why silicone rubber is used in kitchen utensils and medical devices. It is a non-porous material that is resistant to bacterial build-up. Silicone is also non-toxic and recyclable.
Disadvantages of Silicone Rubber
While silicone rubber presents numerous benefits, it also has some drawbacks, including the following:
- Tear Strength – one of the disadvantages of silicone rubber is its poor tear strength. However, this can be remedied by adding another material that could offer strength and abrasion resistance.
- Cost – Since Silicone elastomer is a premium product, it also comes with a premium price tag. This, however, can be offset with improvements in its turnaround time and quality.
Conclusion
Like all other materials used in creating parts, silicone rubber has its benefits and shortcomings. Although it possesses impressive qualities, it does not mean that you can use it with every application.