The waterproof performance of silicone is the core selling point of your product. Understanding the waterproof performance of silicone can help you enhance the competitiveness of your product. This guide will explain the waterproof performance of silicone from multiple aspects.
What Does Waterproof Performance Mean for Silicone Products?
It is well known that silicone has hydrophobic properties, but it is not suitable for all situations. The hydrophobicity of silicone does not equate to waterproofing; waterproofing also has multiple levels and ratings.
Silicone materials have waterproof performance. However, if the design of your silicone products has seams, thin walls or poor mating surfaces, leakage may occur. We hope the following content can give you a clearer understanding of the waterproofing requirements for the silicone products you need.
3 Levels of Silicone Waterproofing
Water-Resistant
“Water-resistant” means it can withstand minor water droplets and rain splashes in daily life, but it cannot be submerged.
When you choose silicone products, the regular material itself can easily meet the water-resistant standard. You can be assured of protection against daily water splashes and surface water splashes, and there is no need to adjust the silicone formula and structure additionally.
Waterproof
The waterproof level offers a stronger protection than the water-resistant level. You can submerge the product in water for a short period of time, and it can also withstand certain water pressure impacts.
Because silicone has hydrophobic properties, most silicone products can meet the standards. However, whether they can maintain waterproof performance depends on the product structure, thickness and process design.
Watertight or Airtight
The protective requirements for the watertight level are the most stringent among these three levels. This means that the product must be completely waterproof and airtight even when exposed to prolonged immersion and high pressure.
Silicone materials alone do not determine airtight performance. If you want silicone products to reach this level, they must be equipped with a dedicated sealing structure, high-end silicone formula and precise production process. Only through the combination of these elements can they achieve long-lasting sealing without any leakage.
Waterproof Rating Standard (IP Rating)
The waterproof ratings of silicone have different protective capabilities. You can refer to the following table for details:
| IP Rating | Protection Capability |
| IP67 | Temporary immersion (1m water depth for 30 minutes) |
| IP68 | Continuous immersion (the manufacturer specifies the depth and time) |
| IP69K | High-temperature and high-pressure flushing |
Key Waterproof Properties of Silicone
Hydrophobicity
The hydrophobicity of silicone causes water molecules to form droplets and roll off the surface, without adhering to or penetrating into the surface.
Moreover, silicone has a built-in self-cleaning effect, with a water contact angle ranging from 100° to 120°, and its hydrophobicity is superior to that of most polymers. This enables your silicone products to dry quickly and avoid moisture seepage.
Water Absorption Rate
Solid silicone is one of the elastomers with extremely low water absorption rate. The water absorption rate within 24 hours is less than 0.1%. This means that if your product is made with solid silicone, even after being soaked for 24 hours, it will hardly increase in weight, deform, or lose its mechanical properties.
Although the long-term water absorption rate of solid silicone remains below 1–2%, silicone foam has many pores and its water absorption rate will significantly increase. When purchasing, you should pay attention to distinguishing between these two materials.
Compression Set
Compression set is the key factor determining the long-term sealing and waterproofing performance of silicone. It measures the material’s ability to rebound and recover after being compressed.
If you choose silicone with low compression set, your product will have a longer sealing lifespan, and can maintain waterproofing stability even under harsh conditions.
Water Pressure Resistance
If you are developing underwater products, water pressure resistance is a key indicator that you need to pay attention to. Once the water pressure resistance limit of the silicone parts is exceeded, the waterproofing performance will also fail.
The pressure resistance of ordinary silicone seals depends on design factors including geometry, compression ratio and support structure. And the hardness, cross-sectional structure, filling ratio and retaining ring of your product will all affect the water pressure resistance.
Temperature Stability
Silicone has excellent temperature stability and can maintain its waterproof performance even under extreme high and low temperatures. When in a low-temperature environment, your silicone sealing component can remain flexible without cracking and the sealing function will not fail.
Silicone maintains stable performance across a wide temperature range and can maintain its hydrophobic property even in high-temperature conditions.
Chemical Stability
In humid environments, silicone maintains excellent chemical stability. For instance, it can stably perform its waterproofing function in various water qualities such as fresh water, seawater, chlorine-containing water in swimming pools, and boiling water, and will not fail due to chemical corrosion.
You can use silicone for drinking water and various water-related applications. However, in a long-term continuous steam environment, silicone will age.
Silicone vs Other Materials in Waterproof Performance
Silicone is an excellent waterproof material, but it is not your only option. You can compare different elastomer materials based on your actual requirements for temperature resistance, chemical contact environment, budget, etc.
Through multi-dimensional performance comparisons, we have compiled the following table. We hope it can help you precisely match your waterproof product needs. Whether you choose silicone or other alternative materials, you can make an appropriate purchasing decision.
| Property | Silicone | EPDM | TPE | TPU | Natural Rubber |
| Water Absorption (24h) | ＜0.1% | ＜0.1% | 0.2–1.0% | 0.3–0.8% | 0.1–0.5% |
| Temperature Range | -50°C to +220°C | -40°C to +125°C | -40°C to +120°C | -40°C to +120°C | -50°C to +80°C |
| Compression Set | Low (10–30%) | Moderate | Moderate-High | Moderate | High |
| Chemical Resistance | Good | Excellent | Moderate | Good | Moderate |
| Relative Cost | Medium-High | Low-Medium | Low-Medium | Medium | Low |
Waterproof Applications of Silicone
Silicone Kitchenware
In the application of kitchenware, you can use silicone to make sealing rings, baking molds and storage covers.
Because it does not absorb water, does not deform, is waterproof, moisture-proof and heat-resistant, and most silicone products can be washed in the dishwasher, they are very suitable for daily kitchen use. However, in this application, your product should have FDA certification.
Electronic Accessories
Silicone is highly suitable for manufacturing electronic accessories such as phone cases, smartwatch straps, and earphone covers, as it has excellent elasticity and a comfortable feel. Moreover, silicone molds have high precision and small errors, which meet the requirements of small electronic components in your industry.
If your electronic accessories have passed the IP67 or IP68 waterproof rating certification, they can effectively protect electronic products from water and dust.
Medical Devices
In the medical devices industry, silicone is commonly used to manufacture medical tubes, seals and components of medical pumps due to its excellent airtight and waterproof properties.
If you are going to produce such silicone products, your products must meet the strict protection and compliance requirements of medical devices, such as complying with the ISO10993 biocompatibility standard and being resistant to repeated sterilization.
Outdoor Gear
If you are involved in the production of outdoor gear, you can use silicone for items such as diving lights, camping gear, and waterproof bag seals. Silicone has excellent UV resistance, weather resistance and salt spray resistance. It can be used in both mountain climbing and diving.
Moreover, it has long-lasting waterproof sealing performance and is stable. It can support long-term underwater immersion and ensure the long-term safe use of the equipment.
Baby and Maternity Products
In the application of baby and maternity products, you can use silicone to make baby bottle nipples, teething toys, suction pump accessories, etc. The high-quality silicone material is non-toxic, odorless, waterproof and non-absorbent. It can also be repeatedly boiled for disinfection.
Thus, your products will be safer and more skin-friendly, allowing your customers to feel at ease when using them for their babies’ daily needs.
Industrial Sealing
Due to the excellent waterproof sealing ability of silicone, along with its resistance to chemicals and high pressure, you can use silicone to make industrial gaskets, O-rings and flange seals.
Moreover, silicone has strong chemical resistance and is unlikely to react with your industrial raw materials. High-quality silicone products have low permanent deformation during compression and can still maintain sealing and waterproof properties under long-term working conditions, making them suitable for demanding industrial environments.
FAQ
Does Silicone Lose Its Waterproof Performance Over Time?
Generally speaking, the waterproof performance of silicone can last for several years or even over ten years. However, factors such as ultraviolet rays, ozone, high temperature and humidity environments, chemical cleaners, and mechanical wear can all affect its waterproof effect. Therefore, over time, the waterproof performance of silicone will decline.
Is the Waterproof Performance of LSR the Same as Solid Silicone?
Yes. The cured LSR has basically the same waterproof performance as solid silicone. The water absorption rate is both below 0.1% and they both have hydrophobic properties. These two types of silicone differ only in their molding processes, and there is no significant difference in their own waterproof performance.
How Does Temperature Affect the Waterproof Performance of Silicone?
Within the normal temperature range of silicone, temperature does not affect the waterproof performance.
Between -50℃ and -20℃, silicone can remain flexible and free from cracking; between -20℃ and 100℃, the performance of silicone is optimal; between 100℃ and 200℃, silicone can still maintain stable hydrophobicity; but when exposed to temperatures ranging from 200℃ to 230℃, a temperature-resistant silicone with a specific formula may be required.
Does Silicone Hardness Affect Its Waterproof Performance?
No. Within the normal hardness range, the water absorption rate and hydrophobicity of silicone remain consistent. The hardness affects the wear resistance and sealing ability of silicone.
Can Silicone Be Recycled After Use in Waterproof Products?
Recycling silicone is more difficult than recycling TPE, as silicone does not melt and remold like thermoplastics. However, silicone has a longer service life, which can reduce the frequency of replacement for your consumers. Silicone can also be recycled by being ground mechanically into a filler form.
Final Thoughts
Legensilico is a professional silicone manufacturer in China, capable of providing you with high-quality and various types of silicone products. If you are interested in learning more about silicone waterproofing, please feel free to contact us at any time.
