When choosing materials for water-related products and waterproof seals, you need to understand silicone’s flotation characteristics. This can help you avoid potential issues that may affect the consumer experience due to floating or sinking. This guide will provide you with detailed explanations on the factors and types that influence the flotation of silicone.
Factors Affecting the Floating Performance of Silicone
Silicone Density Factors
The density of silicone is the most crucial factor determining whether it floats or sinks.
Foaming Degree
The foaming rate of the silicone foam is also an important factor affecting density. The higher the foaming rate you choose, the lower the density will be, and the easier it will be for it to achieve stable floating when submerged in water.
Filler Type and Content
If you purchase silicone with fillers such as quartz powder, carbon powder or mineral additives, the density of the silicone will increase. However, if low-density fillers like hollow glass microbeads are added, this may cause its density to decrease.
Environmental Factors
Apart from the density of your silicone products themselves, the environmental factors in which the products are used can also have an impact.
Water Temperature
The density of hot water is slightly lower, so silicone of the same density sinks more easily in hot water. Although the difference is very small, if your product is often used in hot water, it is still recommended to choose silicone materials with a lower density.
Water Type
The density of seawater is greater than that of fresh water. Therefore, when manufacturing water-related products for use in freshwater environments, you need to consider the floating capacity of this type of silicone.
UV and Chemical
Long-term exposure to ultraviolet rays or contact with chemicals can cause the aging of silicone, resulting in an increase in surface degradation, which enhances the hydrophilicity of the silicone and slightly increases its weight.
Silicone Types Compared: Which Ones Float?
Solid Molded Silicone
Solid molded silicone does not have the ability to float. The density of this type of silicone ranges from 1.15g/cm³ to 1.22g/cm³. However, due to its high density, it will slowly sink to the bottom.
If you want to produce products such as kitchen scrapers, baking pans, cake molds, sealing rings, and phone cases, we recommend that you use this type of silicone.
However, if the product you purchase needs to have a floating function, such as bathtub toys, then this solid molded silicone is completely unsuitable. A wrong choice of materials can significantly affect the usability of the product.
Solid LSR
The floating property of Solid LSR is similar to that of solid molded silicone. When in a solid state, it does not float; when placed in water, solid LSR generally will sink in water because
its density is typically greater than water. The density of this type of silicone ranges from 1.12g/cm³ to 1.20g/cm³.
Moreover, it is soft in texture and highly safe, so you can use it to produce items such as pacifiers, breathing masks, baby products, and precision seals – all of which have strict requirements for material quality.
However, the mold of LSR has high precision and LSR can be made into hollow parts with extremely thin walls. For example, with a float ball, if the average density of the product is less than 1g/cm³, it will be able to float. This point can be taken into consideration when you select the materials.
Silicone Foam or Sponge Silicone
Silicone foam or sponge silicone is the ideal material for you to look for in floating silicone products, as it possesses excellent floating capabilities.
If you want to produce swimming goggles pads, heat insulation pads, shock absorption pads and floating toys, we suggest that you use this type of silicone more frequently. However, its bubble structure is divided into closed pores and open pores.
Closed-Pore Foamed Silicone
The density of this type of silicone is only 0.40g/cm³ to 0.80g/cm³, which is much lower than that of water. The closed-pore foamed silicone has non-connecting air holes and does not absorb water, enabling long-lasting floating.
Open-Pore Foamed Silicone
The density of the open-pore foamed silicone is only 0.50g/cm³ to 0.90g/cm³. The open-pore foamed silicone has connected air holes and may absorb water. After prolonged soaking, it may sink.
So when making the purchase, you need to pay particular attention to the foaming rate, the uniformity of the pores, and the water absorption capacity of the silicone provided by the suppliers.
Hollow Silicone
Hollow silicone is a type of silicone specifically designed for floating needs, featuring stable floating capabilities. Its typical products include floating spoons, floating boards, bathtub toys, and water safety floating balls, etc.
This type of silicone is designed with a thin wall and an internal cavity, which results in an overall density of less than 1, enabling the product to float. When purchasing and using this type of product, you need to avoid puncturing it. Because if water enters the cavity, the product will lose its floating ability and become ineffective during use.
Test Methods for Silicone Floating Performance
Static Water Flotation Test
This floating test method is the simplest one. You cut out a sample of silicone no smaller than 2×2 cm, place it in a transparent container filled with room-temperature water, and observe it statically to intuitively determine the floating state of the sample.
This allows for a quick verification of the floating performance of the silicone itself. For specific judgment, you can refer to the following:
- If the silicone immediately sinks to the bottom, then its density is significantly greater than 1 g/cm³, and the silicone will not float.
- If the silicone sinks slowly, it indicates that its density is slightly greater than 1 g/cm³, approaching suspension.
- If the silicone remains on the water surface or partially exposed, it means its density is less than 1 g/cm³, and the silicone will float.
- If the silicone is suspended at a certain depth in the water, it indicates that its density is similar to that of water. With special design, it can float.
Accurate Density Testing
This measurement method is generally the water displacement method. First, you weigh the silicone sample in the air (W_air), then measure its weight when it is completely submerged in water (W_water). Use the density calculation formula: W_air ÷ (W_air – W_water) × water density.
If the value is greater than 1.00, it will sink; if it is less than 1.00, it will float naturally, helping you accurately determine the floating and sinking properties of the silicone.
Long-term Immersion Test
This testing method is only applicable to silicone foam. You should completely immerse the silicone sample in water and leave it to stand for 7 days. After removing it and drying the surface moisture, retest its floating state.
If the originally floating sample sinks, it indicates that the perforated silicone foam is prone to absorbing water. Such silicone is not suitable for making marine-use products.
Practical Tips to Control Silicone Flotation
Choose the Right Materials
You can choose the low-density silicone material and appropriately reduce the fillers in the formula, thereby effectively lowering the overall density and steadily enhancing the floating of the silicone products, making them suitable for various water-related applications.
Hollow Structure Design
Designing a hollow structure is also a simple way to significantly enhance the floating ability. You can use it to create internal cavities within the product, effectively reducing the overall density of the silicone item.
Layered Structure Design
You can adopt a layered structure design, combining the high-density and low-density silicone layers with each other. This enables precise control of the overall density and flexible adjustment of the floating size, making it suitable for a wider range of precise industrial applications.
Prototype Testing
Prototype testing involves conducting small-scale immersion tests before large-scale production. Through this process, you can preliminarily assess the floating performance of the silicone products and promptly identify potential structural and formulation design issues. This can help you avoid mistakes and losses that may occur during mass production.
Surface Treatment
When performing surface treatment on silicone products, you should avoid using coatings that will significantly increase the product’s weight or have strong adhesion to water.
Coatings that are too heavy will increase the overall density, while strong hydrophilic coatings will cause the silicone surface to firmly absorb water after the product is immersed in water, thereby affecting the original floating performance of the product.
FAQ
What Certifications Do I Need for Regulated Floating Silicone Procurement?
This depends on the application of your final product. For instance, if your product is a kitchenware item, then you need to follow FDA 21 CFR 177.2600; if your product is used in the medical industry, then ISO 10993 is even more necessary.
Is Floating Silicone More Expensive Than Standard Solid Silicone?
Yes. Because the floating silicone requires more processing steps, such as the use of chemical or physical foaming agents; or the hollow structure design requires more precise molds. All these will lead to an increase in costs.
Can I Require Floating Silicone Suppliers to Meet Specific Density Requirements?
Yes. The density of silicone can be controlled. As long as your supplier has sufficient manufacturing experience and your requirements are within a reasonable range, this can be achieved.
How Long Can Silicone Maintain Its Flotation in Outdoor Environments?
High-quality silicone products can maintain stable flotation for several years. However, prolonged exposure to outdoor ultraviolet rays, chemical erosion, and continuous immersion in water will gradually reduce their floating performance.
Is There a Difference in Flotation Between Recycled or Reprocessed Silicone and Virgin Silicone?
Yes. Because the recycled or reprocessed silicone contains different fillers, the density of this type of silicone is difficult to predict. You will need to conduct precise density measurements to know its exact density.
Final Thoughts
Legensilico is a silicone supplier with professional manufacturing experience and a wide range of product categories. We can also provide you with specialized silicone customization services. If you are interested in our silicone products, please feel free to contact us at any time.
