When sourcing silicone gaskets, you may worry that they will leak or fail. The compression percentage is an important factor used to control the quality of sealing and prevent the silicone gasket from leaking water. This article will talk about the compression percentage of silicone gaskets.
What Is Compression Percentage
Compression Set
A compression set means that when a silicone gasket is pressed for a long time and cannot fully go back to its original shape if the pressure is removed. When purchasing a silicone gasket, it refers to the ability of the gasket to keep its shape after being used under pressure or stored.
Compression Percentage
Compression percentage refers to the difference between the silicone gasket’s original thickness and its thickness under compression, divided by the silicone gasket’s original thickness, usually expressed as a percentage. Its calculation formula is as follows:
If there’s a 3mm silicone pad here, and its thickness is 2.25mm after compression, then its compression percentage is:
Compression percentage is generally used to show how much a silicone gasket gets compressed when two parts are assembled together, such as how much the thickness is reduced in a silicone gasket. It can show how tightly the seal is pressed in the product, such as in boxes, housings, or the sealing structures inside electronic equipment.
The Significance of Silicone Gasket Compression Percentage
The compression percentage is very important because it can influence the silicone gaskets’ performance in the devices and products. When sourcing silicone gaskets, you may often find problems if you have chosen the wrong figures.
If the compression is too low, the gasket might not fit the surface well, and will produce small gaps. In daily use, these gaps may let water, air, or dust get into products like boxes, lamps, or equipment.
If the compression is too high, the gasket will get squished too tightly. At first, it looks like it is tight and there’s no small gap, but after a while, it might lose its ability to rebound, and its shape could worsen. This influences the sealing effect during use, especially after long-term storage or repeated closing and opening.
Therefore, when you’re buying silicone gaskets, you usually need a suitable compression range to make sure the sealing can stay stable during transport while also lasting in long-term use, instead of just caring about whether it is tight at the beginning.
Factors Affecting Silicone Gasket Compression Percentage
Thickness and Installation Gap
When the gasket is thicker but the gap stays the same, it gets compressed more tightly after being assembled, and the compression percentage goes up. When the gasket is thinner, but the gap hasn’t changed, the amount of deformation after being compressed will be smaller, and the compression percentage drops.
The influence of the installation gap is opposite. The smaller this space is, the more the gasket will be compressed, so the compression percentage rises. When the space is larger, the gasket doesn’t come into enough contact, so the compression percentage goes down.
When purchasing silicone gaskets, if you need to change the design of the silicone gasket, you also have to change the gasket size as well. Because a small change in the gap can largely influence the sealing performance. Sometimes a small gap can cause over-compression, while a large gap can cause insufficient contact.
Thickness and gap together determine the working space of the gasket and influence the sealing stability of the silicone gasket in the market directly. So, if you’re buying silicone gaskets, you have to think about thickness as well as installation gap.
Assembly Clamping Force
Assembly clamping force refers to the stress applied when two parts of a product or a device are pressed together in final assembly. This force directly influences the compression percentage of silicone gaskets because it can determine how tightly the gasket is actually pressed when used.
When the clamping force is high, the gasket is pressed more tightly, and the compression percentage increases. When the clamping force is low, the gasket isn’t fully pressed, and the compression percentage will be lower than the designed value.
In business, this often occurs when different workers or factories make the same silicone gasket. Even if the gasket design is the same, different assembly clamping forces can lead to different final compression results.
For example, if screws are not tightened properly, the silicone gasket might look assembled, but there may be small gaps in it, which can cause leaks during use. At the same time, if the force is too strong, the gasket might be over-compressed, and its rebound ability could be reduced over time.
So, if you want to choose a silicone gasket with a suitable compression percentage, you need to think about the assembly clamping force during the installation and use of the gasket.
Surface Flatness
Surface flatness means whether the two surfaces that come into contact with the silicone seal are smooth enough. This factor directly influences the compression percentage because it can change whether the pressure on the seal is even.
When the surface is very flat, the seal gets compressed evenly, and the compression percentage is close to the design value. In this case, the sealing performance can usually stay stable in transport and long-term use.
However, when the surface is uneven, the silicone gasket may not work normally. Some areas will touch first and get compressed more, while other areas might not be compressed at all. This will cause the seal to have different compression levels in different areas.
When people use products or devices, such as metal casings, plastic boxes, or electronic device enclosures, surface flatness can make the same seal have different pressure levels, and one side could be too tight while the other side still has gaps. This can make weak sides during transport or long-term use, and may influence the user’s experience.
So, when you’re sourcing silicone gaskets, you also need to care about the surface flatness and its influence on the silicone gasket.
How to Choose the Right Compression Percentage for Silicone Gasket
Sealing Requirements
When you are choosing the compression percentage for a silicone gasket, the sealing rating is the most important point to think about. You’d better not pick a number first, but think about the sealing goal of the silicone gasket, such as dustproof, waterproof, or use in high-pressure environments. You need to choose a compression percentage suitable for it.
If the silicone gasket only needs basic dust protection or indoor use, you can choose a lower compression range. This makes it easier to assemble and will not put extra stress on the material.
But if the silicone gasket needs to be waterproof or used outdoors, you have to choose a higher compression range to make sure that the contact is tighter. And for IP65 and above or high-pressure sealings, you need a more stable and higher compression range to make sure that it can be used and stay stable for a long time.
You can choose the suitable compression percentage according to the following table:
| Sealing level | Compression Percentage |
| Dust Sealing | 10% – 20% |
| Water Sealing | 20% – 30% |
| IP65–IP67 | 25% – 35% |
| High-Pressure Sealing | 20% – 25% |
Long-Term Reliability
When choosing the compression percentage, long-term reliability is very important, and it influences whether you can reduce after-sales problems. Many products have no problems when tested, but after a few months of use, there may be problems. So, when choosing, you should make sure that it can stay stable for a long time.
If the silicone gasket does not need a long lifespan, such as disposable or short-cycle use, a low or medium compression range is fine. But if the product is designed for long-term use or export sales, you should choose the stable range of 20%–35%, and this range is less likely to have problems of performance and properties in use.
You can choose a suitable compression percentage according to how long you use it:
- Below 15%: Easy to leak because of insufficient compression
- 20%–35%: Optimal and most stable range for long-term performance
- Above 40%: High risk of compression set and sealing failure over time
Hardness of the material
When choosing the compression percentage, material hardness is very important as well. It is a good choice for you to choose the hardness first and then check if the compression range is suitable.
Soft materials (like 20 Shore A) are easy to deform and don’t need too much compression to form a seal, but they are very likely to get over-squeezed.
Medium hardness (40–60 Shore A) is usually the common choice for many industrial products, and the corresponding compression range is the most stable as well.
Harder materials (70 Shore A) need higher compression to make full contact, so this may cause leaks in some areas.
So, you should choose the compression percentage according to the hardness of the silicone gasket material:
| Hardness | Compression Percentage |
| 20 Shore A | 15%-20% |
| 40 Shore A | 20%-30% |
| 60 Shore A | 25%-35% |
| 70 Shore A | 30%-40% |
FAQ
Can Working Temperatures Influence the Compression Performance of a Silicone Gasket?
Yes. Temperature changes can influence the hardness and flexibility of silicone materials slightly, which in turn can influence how a silicone gasket performs under compression in tests and daily use.
How to Test the Compression Performance of a Silicone Gasket?
Usually, we use the ASTM (American Society for Testing and Materials) method B for compression set testing.
First, measure the original thickness of a gasket. Then place it in a compression device and compressed by 25% of its original height. Next, place the device and gasket in an oven and bake them for 22 or 70 hours according to the type of elastomer. At last, take out the gasket, cool it for 30 minutes, and measure its final thickness.
Can the Compression Percentage of a Silicone Gasket Be Adjusted During Production?
Yes, the compression percentage can be adjusted by changing the silicone gasket’s thickness, groove depth, or overall assembly design. However, once the mold is finished and mass production starts, the compression range is fixed, and it is generally hard to change without redesigning the structure.
What Are the Common Causes of Silicone Gasket Failure?
Common causes include improper compression, poor contact surfaces, and long-term material aging. Moreover, incorrect installation or design mismatches can cause seal failure as well.
Can Silicone Gaskets Be Customized?
Yes, silicone gaskets can be fully customized. You can choose different shapes, sizes, hardness, and colors according to your needs. What’s more, you can design a silicone gasket specifically for compression performance as well.
Final Thoughts
The compression percentage of a silicone gasket largely influences its sealing performance and its stability. Choosing the right range can prevent leaks and many problems. If you’re sourcing silicone gaskets, feel free to contact us for more information, and we will provide professional advice.
