Both silicone and rubber are commonly used elastic materials, but they have quite different structures and properties. When selecting materials for seals or parts, it is important to consider factors such as temperature, exposure to chemicals and mechanical pressure. If you are unclear about these differences, it is easy to select the wrong material, which can affect product performance. This article will help you understand the main differences between silicone and rubber, making it easier for you to make the right choice when designing or manufacturing.
What Is Silicone
Silicone is a polymer material consisting of silicon and oxygen in the main chain, as well as carbon and hydrogen. Its molecular structure consists of alternating silicon and oxygen atoms, determining its basic performance in terms of high-temperature resistance, chemical stability, and flexibility. This is significantly different from that of ordinary organic rubber.
Silicone exhibits high and low temperature resistance, allowing for prolonged use within a temperature range of -60°C to 250°C. At low temperatures, the molecular chains remain active, so the material does not harden or become brittle. At high temperatures, the silicone-oxygen main-chain structure is stable and not susceptible to thermal deformation or performance degradation.
What Is Rubber
Rubber is an elastic material composed of long-chain polymers, with a C-C main chain at the core of its molecular structure. This structure is based on the C-C main chain. Although the molecular chain is soft, the bonding energy is lower than that of the Si-O main chain of silicone. Therefore, only through vulcanisation or cross-linking can rubber obtain stable elasticity and reliable performance.
Differences Between Silicone and Rubber
Molecular Structure
The main chain of silicone consists of alternating silicon and oxygen atoms, along with some organic side groups. This more stable structure enables it to withstand high temperatures without becoming hard or brittle at low temperatures. The side groups keep the material soft and also affect its hydrophobicity and processability, meaning silicone usually maintains relatively stable performance in different environments.
The main chain of rubber is made up entirely of carbon-carbon bonds. As the bond energy is lower than that of silicone, the molecular chain is soft but has limited resistance to high temperatures. Rubber must be vulcanised or cross-linked to maintain stable elasticity; otherwise, it can easily harden at low temperatures, soften or age at high temperatures, resulting in less stable performance during use.
Temperature Resistance
Silicone can withstand a wide range of temperatures without losing its properties. It remains soft in cold environments and does not harden, and it does not soften or degrade at high temperatures. It can typically be used for long periods of time at temperatures ranging from -60°C to 200-250°C with little change in its properties.
Rubber is more sensitive to temperature. Higher temperatures soften it and accelerate wear, while lower temperatures harden it and cause it to lose its elasticity. Most rubbers operate at temperatures ranging from approximately -30°C to 120-130°C, depending on the formulation.
Weather and Ageing Resistance
If the product needs to be exposed to air or outdoor environments for a long period of time, ageing resistance is more important than initial performance. Silicone has stable molecular chains, is insensitive to UV, ozone and oxidation, and has a slow decay of performance.
Rubber is not as good as silicone in this respect. It is susceptible to UV, ozone and oxidation and may harden, crack or lose its elasticity with long-term use. In order to extend the service life, anti-ageing agents are usually added, but this can only slow down the decline and cannot completely change the nature of the material itself. Therefore, if the product is exposed for a long period of time or is difficult to maintain, silicone is more secure, while rubber needs extra protection.
Chemical Resistance
Silicone is chemically very stable in air, water and alcohol and therefore does not decompose easily. However, its intermolecular forces are not very strong. If silica gel comes into contact with oil or certain organic solvents, these substances will penetrate into the structure of the silica gel, causing it to swell and reduce its mechanical strength. Prolonged exposure to strong acids or bases can also damage its molecular structure, thus affecting the material’s performance.
Rubber is different in that its chemical resistance depends on the type of rubber. Nitrile rubber (NBR) handles mineral oils, fuels and lubricants well. Ethylene propylene diene diene (EPDM) is resistant to acids, alkalis and water, but does not perform well in oil environments. Natural rubber is the least chemically stable and is susceptible to organic solvents. That’s why, where oil or fuel is involved, NBR is preferred to ensure reliable material performance.
Mechanical Properties and Wear Resistance
Silicone rubber is flexible and can stretch without breaking. Its molecular structure lets it spring back to its original shape after being stretched or compressed. But the bonds between its chains aren’t very strong. So if the surface is constantly exposed to friction or shear, it will eventually wear out.
When a force is applied, the molecular chains of rubber can be elongated or compressed, which disperses the stress and slows down wear and crack expansion. Consequently, rubber has good load-bearing capacity and fatigue resistance. It also maintains stable performance in dynamic working environments or environments with a lot of friction.
Biocompatibility and Safety
The molecular structure of silicone is stable, meaning it does not readily release small molecules or volatiles. It also leaves no harmful residues after sterilisation or disinfection. These properties make silicone safe for use in the food and medical industries, as well as for direct skin contact. Medical catheters, intimate products and cutlery, for example, can be used with confidence.
Natural rubber contains latex proteins that can cause allergic reactions, while synthetic rubber usually contains additives that can migrate, rendering it unsuitable for direct food or medical use.
Electrical Insulation Properties
Silicone has a very low electrical conductivity and stable insulation. It maintains its properties even at high temperatures, so electronic components, cables or protective parts are well suited to use it. Things like sensor housings, wire insulation sleeves, and even miniature electronic components are many times made of silicone. Processed by injection moulding, not only can the dimensions be controlled accurately, but they are also consistent when mass produced.
Rubber also provides some insulation in normal times, but is less stable over time. Ageing, heat, and humidity all affect it, allowing insulation to slowly decline. Rubber is often used in anti-vibration gaskets, seals, or keypads. These parts don’t require much in the way of heat or insulation, but they must be flexible and wear-resistant. Because of this, rubber is better suited in this application.
Processing Methods and Cost Considerations
Silicone can be processed by injection moulding, compression moulding or transfer moulding. Injection moulding is particularly suitable for high-precision parts because the dimensional control is more stable. But the raw materials and moulds for silicone are quite expensive, and the productivity is a bit lower than that of rubber. But don’t forget that silicone is resistant to high and low temperatures, doesn’t age easily, has a long life, and requires little maintenance. In the long run, it’s actually quite cost-effective.
Rubber can also be processed in a number of ways, such as compression moulding, extrusion or transfer moulding. It’s low-cost and efficient, so rubber is better suited for high-volume or large-sized industrial parts. It has a shorter lifespan, though, and requires more maintenance, which can make it more costly than silicone in long time.
Main Types of Silicone & Rubber
Main Types of Silicone
Liquid Silicone Rubber (LSR)
During injection moulding, these materials are mixed and vulcanised within the mould. As LSR has a better flow rate, it can more easily fill complex mould cavities. This is why it is often used to produce complex parts with exacting dimensional requirements. The process is stable and repeatable, making it ideal for producing silicone products that require precision and consistency.
High-temperature Vulcanised Silicone (HTV/HCR)
HTV, also known as HCR, is usually in solid or gel form. It is primarily processed through compression or transfer moulding. Compared to LSR, it is tougher and more resistant to tearing. Therefore, it is more suitable for relatively simple, larger-sized silicone parts. Common applications include seals, gaskets and various industrial silicone components.
Main Types of Rubber
Natural Rubber (NR)
Natural rubber comes from the latex of the rubber tree. It is highly elastic and can withstand repeated stress, making it ideal for use with moving parts or under friction. However, its performance is limited in extreme temperatures: it softens when hot and hardens and loses elasticity when cold. Although latex is non-toxic, some people can be sensitive to latex proteins, so safety measures are required for certain applications.
Synthetic Rubber
Nitrile rubber (NBR) is made from acrylonitrile and butadiene. It is more resistant to oils and fuels than natural rubber, as well as being mechanically stronger and resistant to a wide range of chemicals. Due to these characteristics, NBR is commonly used in oil seals and fuel lines. It can be used in temperatures ranging from about -30°C to 120°C.
Ethylene propylene diene monomer (EPDM) is made from ethylene, propylene, and a small amount of non-conjugated diene. It can be used over a wide temperature range for long periods of time, from approximately -50°C to 150°C. It is also resistant to ozone, oxidation, acids and bases. However, it is important to note that it is not resistant to mineral or fuel oils. This is why EPDM is commonly used for automotive seals, roof waterproofing and other industrial parts requiring high weather resistance.
Application Comparison: Silicone vs Rubber
Medical & Health
Silicone is safe for humans, causes little skin irritation and contains no toxic substances. This makes it suitable for use in medical catheters, silicone patches and food-grade appliances. It can withstand high-temperature sterilisation and does not deteriorate in performance when stored at low temperatures.
There are more diverse types of rubber. Natural rubber contains latex proteins, which can cause allergies; synthetic rubber requires additional additives and certifications before it can be used in medical or food scenarios. As a result, these types of rubber are often used for parts that do not come into direct contact, disposable products, or lower-risk accessories.
Automotive
Silicone rubber is resistant to heat, ageing, and chemicals, making it ideal for engine seals, vacuum lines and fuel lines, which are often exposed to high temperatures or chemicals.
Rubber, on the other hand, is more abrasion-resistant and tough, making it suitable for tyres, seals, belts and other parts that are subject to friction or dynamic loads. The performance needs of different parts determine whether silicone or rubber is used.
Electronics
Silicone is suitable for sensor housings, wire insulation sleeves, and miniature electronic components. Injection moulding ensures dimensional accuracy and high consistency in mass production.
Rubber is commonly used for parts such as anti-vibration gaskets, seals or key gaskets. These parts do not require high temperature resistance or high insulation, but need to maintain a certain degree of elasticity and abrasion resistance.
When to Choose Silicone & Rubber
Next is a table for silicone vs rubber from different angles.
| Material Choice | Suitable Scenarios | Description |
| Silicone
| High-temperature environments | Can withstand a wide temperature range, suitable for engine components, electronic parts, etc. |
| Long-term outdoor use | Resistant to UV, ozone, and ageing, maintains stable performance over time. | |
| High cleanliness / Medical / Food | High biocompatibility, non-toxic, can withstand sterilisation, suitable for medical devices and food-contact parts. | |
| Rubber
| Cost-sensitive projects | Low raw material and production costs, suitable for large-scale industrial parts. |
| High wear / Heavy mechanical stress | Good toughness and fatigue resistance, suitable for tyres, seals, belts, and other dynamic load components. | |
| Non-high-temperature environments | Suitable for medium- to low-temperature conditions, not ideal for prolonged high-temperature use. |
FAQ
Is Silicone Better Than Rubber?
Strictly speaking, silicone is not necessarily better than rubber. It really depends on your needs. Silicone copes well with high and low temperatures. It also resists ageing and UV damage, so it remains flexible and is less likely to crack, even in extreme or outdoor conditions. However, silicone is not ideal for parts that will come into contact with oil, as the oil can penetrate the material. In this case, rubber is usually a better option.
Rubber is not as tough as silicone. However, it is hard-wearing, strong and cheap. This makes it suitable for everyday items such as tyres, seals and belts, particularly in moderate temperatures. So, in summary, if you need heat resistance, long-term outdoor use or high cleanliness, silicone is the better choice. For parts that need to withstand friction or mechanical stress, or that are more costly, rubber is a solid choice.
Which Lasts Longer, Silicone or Rubber?
This question is difficult to summarise in a single sentence, as it depends crucially on the environment in which the material will be used. Silicone is generally more durable in harsh conditions, such as extreme temperature fluctuations or when exposed to the outdoors for extended periods. It is more resistant to high and low temperatures, UV rays and ageing, so it performs more consistently in these environments.
However, rubber can also have a long lifespan in general working conditions, provided the right type is selected and used wisely. It is important to note that rubber is more susceptible to ageing. If it is exposed to high temperatures for a prolonged period, its elasticity will decrease, and its service life will be shortened.
Is Silicone More Expensive Than Rubber?
In general, silicone is more expensive than rubber. This is primarily due to the high cost of the raw materials and the complexity of the production process. In addition, high-grade applications require extra controls and certifications, which increase the initial investment.
However, the situation is not quite the same in the long term. Silicone is resistant to high and low temperatures, and it does not age easily. Maintenance and replacement requirements are relatively low during use. While rubber is initially low-cost, it may require more frequent maintenance or replacement over the long term, which can increase the overall expense.
Final Thoughts
Although silicone and rubber have a similar appearance and feel, and both are tough and resilient, they are not equally suitable for all working conditions or able to withstand the same range of environmental conditions. Therefore, it is difficult to simply say which is ‘better’; the key is to determine whether it is suitable for a specific application. Before choosing a material, you need to be clear about your production methods and the temperature, environment and performance requirements that the product will face in use.
If these factors are difficult to determine, Legensilicone can provide more systematic support. We can help you develop suitable materials and processes that take into account temperature resistance, ageing resistance, cleanliness, mechanical strength and flexibility. This will help you balance performance, cost and service life while reducing the risks associated with maintenance and replacement. We are waiting for you!
