Silicone and EPDM are often used in a wide range of consumer goods fields, such as HVAC, the outer layer of wires and cables, sealing rings, etc. Understanding the differences between EPDM and silicone is crucial for choosing the appropriate material based on specific applications. Let’s delve into their respective characteristics and differences together to select the most suitable material for your product.
Silicone vs EPDM: Similarities
- Excellent weather resistance: Both EPDM and silicone are resistant to ultraviolet rays and ozone. These two types of materials are often used in making outdoor products, and they will not discolor or decompose.
- Good electrical insulation performance: EPDM and silicone have very high resistivity and are excellent electrical insulators. It is suitable for use as the outer insulation layer of wires and cables and the sealing parts of electronic devices.
- Flame-retardant performance: Both are resistant to polar solvents, water, dilute acids, dilute alkalis, and salt solutions.
- Overlap in application fields: Both can be used as seals, waterproof materials, and protective layers for wires and cables. If your product mainly requires weather resistance and elasticity, you can freely choose between EPDM and silicone according to your personal budget.
- Resist certain chemical substances: Both EPDM and silica gel can tolerate weak acids and weak bases, certain polar solvents. Similarly, neither of them is resistant to non-polar oil solvents and will swell rapidly when exposed to an oily environment.
Silicone vs EPDM: Differences
Water Resistance
EPDM has the strongest waterproof performance among all rubbers. The crosslinking density of EPDM is relatively high, and it is not easy for water to penetrate even after long-term immersion in water. In high-temperature steam, the performance of EPDM is also very stable, so EPDM is often used as a roof waterproofing membrane and sealing parts for high-temperature steam devices in construction.
Silicone also has water resistance. However, due to its lower cross-linking density of chain segments compared to EPDM, water molecules will seep in during long-term immersion in water, causing the silicone product to expand. Moreover, in a high-temperature steam environment, the decomposition of silica gel will be faster. In environments with short-term contact with water, the water resistance of silicone is sufficient.
If you want to make household silicone molds, silicone is completely fine. Silicone products are not suitable for waterproofing in the construction industry. Of course, silicone can also be modified to enhance its water resistance. For instance, after modification, you can produce silicone seals and other products.
Chemical Resistance
EPDM has a wider range of chemical resistance. EPDM can resist acids and alkalis, high temperatures, and some polar solvents. In the chemical industry, EPDM can be used to make seals for chemical pipelines and sealing strips for chemical tanks. However, EPDM must not come into contact with oil, hydrocarbon fuels, concentrated acids, concentrated alkalis, or halogenated solvents.
Silicone is resistant to weak acids, weak alkalis, and automotive brake fluid. The chemical resistance of silica gel will decline in an environment above 150℃.
Wear Resistance And Mechanical Strength
EPDM has strong wear and tear resistance. For products that need to deal with long-term friction, EDPM is an excellent choice. For example, door and window sealing strips, anti-slip parts for sports equipment, etc.
For industrial heat-transfer equipment, gasket material should be selected according to operating temperature, fluid compatibility, and sealing requirements. Plate heat exchanger gaskets are commonly available in elastomers such as EPDM and NBR to support reliable sealing under different operating conditions.
Silicone has very poor wear resistance and will wear out severely in long-term friction. The wear resistance of EPDM can also be improved by adding reinforcing agents, but it still cannot compare with that of EPDM after modification. The modified silicone can only be used in some low-friction application scenarios, such as silicone tableware.
The mechanical strength of EPDM is also higher than that of silicone. EPDM chains have greater rigidity and are less likely to break even when subjected to repeated stretching. Silicone has relatively low fatigue resistance and is prone to tearing when repeatedly stretched.
Temperature Resistance
The main chain of silicone is composed of silicon-oxygen bonds (Si-O), whose bond energy is much higher than that of carbon-carbon bonds (C-C) in EPDM. Moreover, silicone is a thermosetting elastomer. After the curing is completed, the silicone gel structure will no longer melt. This thermosetting property makes its heat resistance more stable. Even when repeatedly heated above 200℃/450F, it can still maintain its shape and basic performance.
EPDM is a thermoplastic elastomer. Although a cross-linked network is formed after vulcanization, the cross-linked bonds at the lower part may break at high temperatures, resulting in softening or flow. The melting point of EPDM is only 148°C/ 300°F, and it begins to decompose at 130℃.
Silicone is the first choice for scenarios that require high-temperature stability. For instance, silicone O-rings for car engine seals and food-grade silicone baby bottle caps can be made of silicone.EPDM is more cost-effective for medium-temperature scenarios. For instance, in a normal temperature environment, EPDM rubber strips for car wipers are resistant to ozone and rain erosion, and their cost performance is higher than that of silicone.
Compression Deformation
Compression deformation rate refers to the proportion of permanent deformation of a material after it has been in a compressed state for a period of time. The lower this value is, the better the resilience of the material is, and the more the material can maintain its sealing performance or shock absorption effect. For products such as O-rings, gaskets, and shock-absorbing pads, the compression deformation rate directly determines their long-term reliability in use.
The main chain of silica gel has a silicon-oxygen bond structure, with weak intermolecular forces and strong chain segment movement ability. At room temperature, the compression deformation rate of silicone is not high. Its advantage lies in high-temperature stability. When the ambient temperature rises to 200℃, the molecular chains of silicone can still maintain a certain degree of mobility and can quickly rebound after compression.
At low temperatures, the resilience of silicone deteriorates. At -60 ℃, the activity of silicon-oxygen bonds is restricted, the material becomes hard and brittle, and the compression deformation rate will be very high. Silica gel molecules are prone to permanent deformation under long-term compression.
The rigidity of the EPDM molecular chain is higher than that of silica gel, and the movement of its chain segments requires more energy. The permanent compression set rate of EPDM at room temperature is close to that of silicone. However, the performance of EPDM varies in high-temperature scenarios. Its compression set rate at 148℃ is lower than that of silica gel at the same temperature. At temperatures above 232℃, its high-temperature performance is comparable to that of silica gel.
In low-temperature environments, the compressive resilience of EPDM is better than that of silicone. EPDM can still maintain a certain degree of elasticity at minus 40℃. This makes EPDM more advantageous in the sealing of equipment in cold regions.
To sum up, if your product needs to be sealed at high temperatures, silicone is a better choice. If sealing is done at room temperature, the more cost-effective EPDM is sufficient.
EPDM is preferred for sealing equipment in cold regions. For instance, in the cold winter in the north, EPDM outdoor sealing gaskets can still maintain their elasticity, reducing leakage caused by hardening.
Processing Performance
Silicone rubber processing has relatively high requirements for equipment precision. Local temperature differences in the mold may lead to incomplete vulcanization or the appearance of bubbles or defects on over-vulcanized surfaces. Although room-temperature vulcanized silicone does not require heating, the humidity must be strictly controlled. Silicone has medium fluidity. During injection molding, pressure needs to be controlled, and process parameters need to be adjusted frequently. Compared with silicone, the processing parameter adjustment range of EPDM is larger, and the process is easier.
Silicone is mainly produced by three processes: injection molding, extrusion molding, and compression molding. Injection molding has high efficiency and is suitable for mass production of small parts such as sealing rings and silicone buttons. The short vulcanization time after injection is suitable for rapid turnover. Extrusion molding is used for the production of rubber hose sealing strips. When continuously extruding, the screw speed needs to be controlled to match the traction speed to avoid stretching deformation. Compression molding is used for large or complex-shaped products such as automotive gaskets. The mold cost is relatively high, but the dimensional consistency is good.
The commonly used calendaring extrusion molding process for EPDM. Calendering can produce films or adhesive tapes. Extrusion molding is used for rubber hoses and flexible hoses. The expansion rate of EPDM extrusion is relatively high, so the die design needs to reserve shrinkage compensation. Compression molding is similar to silicone rubber, but due to the slower vulcanization speed of EPDM and the longer heating time of the mold, the production efficiency of a single mold is slightly lower.
Silicone can undergo secondary vulcanization to enhance its compression set performance. Secondary vulcanization is carried out in an oven. This process increases energy consumption but can improve the aging performance of the product. EPDM generally does not undergo secondary vulcanization. After complete vulcanization, its performance is already stable, and additional treatment does not bring significant benefits.
The surface treatment of silicone is relatively simple and can be directly printed or sprayed. The surface of EPDM is highly inert. Before printing, it needs to be sanded or coated with a primer. If not handled properly, it is prone to peeling off, increasing the subsequent processing procedures.
Service Life
The lifespan of your product mainly depends on the environment in which it needs to be placed.
If your product needs to operate for a long time in high-temperature, humid, chemically corrosive, or ultraviolet environments, silicone is preferred. In these environments, silicone has a longer lifespan, which can reduce the frequency of product replacement and maintenance and save costs.
If your product is used in a mild environment, operates in a wear-resistant environment, and your budget is limited, EPDM can be an alternative. Of course, a more reliable approach is to test the aging curves of the two materials in the local environment based on the actual working conditions of the product and then determine which material to choose.
Safety and Biocompatibility
Silica gel has extremely stable chemical properties and no easily migrating harmful groups in its molecular structure. Silicone is a mainstream food contact material worldwide and has passed the FDA food contact certification. Tests show that long-term exposure to oils and acidic or alkaline foods does not release toxic substances. Silicone is the preferred choice for baby pacifiers, baking molds, kitchen sealing rings, etc.
Oligomers are prone to precipitate on the surface of EPDM. Limited to the field of food contact. During the EPDM processing, plasticizers or antioxidants may be added and migrate into food in high-temperature or oily environments. EPDM is generally only used for non-direct contact sealing parts in food processing equipment.
The medical field has strict requirements for biocompatibility and must pass the ISO 10993 series tests. Silicone fully meets these requirements. For instance, when medical silicone catheters come into contact with blood, they do not clot and do not trigger inflammatory reactions.
EPDM fails to meet medical-grade biosafety standards. Its potential chemical precipitates may trigger cytotoxic reactions. In medical equipment, EPDM is only used in non-contact parts such as anti-slip pads on the equipment shell or support parts of external connecting pipes.
Cost and Price
The market quotation for silicone is usually around 6.25 US dollars per kilogram. The price range of EPDM is between 2 and 4 US dollars per kilogram. Just from the perspective of raw material procurement, the cost of EPDM is lower than that of silicone.
Silica gel mainly consists of silicon dioxide and organosilicon polymers, and it has high requirements for the purity of raw materials. Silicone rubber production requires strict control of the anhydrous and oxygen-free environment. Polymerization reactions are often carried out under high temperature and high pressure, and the vulcanization process needs precise regulation of temperature and humidity. This leads to the overall price of silicone being higher than that of EPDM.
What are the Application Fields of EPDM and Silicone
Sealing and Protection of HVAC System
EPDM is renowned in the HVAC field for its weather resistance and sealing performance. During the long-term operation of the system, the joints of the air ducts are subject to alternating cold and hot temperatures. The material at the joints needs to maintain elasticity with temperature changes. The thermal expansion coefficient of EPDM is stable, which can expand and contract synchronously with the metal or plastic substrate to avoid air leakage caused by stress cracking. The shell sealing gasket made of EPDM can simultaneously achieve dust-proof and airtight performance. The flexible connection sections of ventilation ducts often use EPDM rubber strips to buffer the vibration during fan operation and reduce noise transmission. The perforated cable ring is a distinctive application of EPDM. After cutting regular holes in the metal plate, the cable ring is embedded to prevent dust from entering the equipment casing.
Silicone is mainly used for special working condition protection in HVAC. The high-temperature area sealing silicone strip does not soften or deform when in long-term contact with hot air above 150℃.
Sealing and Protection of Industrial Equipment
EPDM has strong resistance to polar solvents. The EPDM used for sealing the hole covers of metal storage tanks can resist industrial atmospheric corrosion.
Silicone is focused on high-temperature and fire-resistant scenarios in industry. The cable entry of the electrical control cabinet requires fireproof sleeves made of silicone material that can withstand short-term high temperatures. Silicone rubber is selected for sealing parts in non-strongly corrosive areas of some chemical equipment.
Sealing and Shock Absorption in Automobile Manufacturing
EPDM is used for the sealing strips of car door frames. The gasket at the connection between the hood and the body, made of EPDM, can absorb the tiny displacement caused by the engine vibration
Silicone is mainly used in high-temperature areas of automobiles. The sealing of the heat shield near the exhaust system and the sealing between the headlamp lens and the housing.
The Field of Electronics and Electrical Appliances
The EPDM sealing gasket for outdoor door frames is resistant to acid rain and salt spray corrosion, has a high surface resistivity, and does not adsorb dust. For waterproof gaskets of consumer electronic devices, EPDM is the preferred choice.
The silicone used for potting circuit boards forms an elastic barrier after curing. The insulating sleeve of the high-frequency connector is made of silicone to ensure that the signal transmission is not distorted.
Daily Consumer Goods and Specialized Tools
The EPDM used for joint sealing in inflatable swimming pools is resistant to exposure to sunlight and erosion by chlorine water. For the waterproof joint rubber strips of camping tents, choose EPDM. EPDM is added to the palm area of industrial rubber gloves to enhance oil resistance.
Silicone is mainly used in household scenarios to emphasize safety and skin-friendliness. Silicone for kitchen baking molds is easy to demold and leaves no residue. The sealing ring of the baby pacifier is made of silicone and has passed food-grade certification. The sealing ring of the household sealed can is made of silicone, which is resistant to cold storage and low temperatures. The grips of some power tools are made of silicone to increase friction.
Summary
In conclusion, although EPDM and silicone each have their own advantages, their respective characteristics can meet different applications and requirements. On the other hand, EPDM has high wear resistance and tear strength, making it suitable for manufacturing durable and long-lasting products. If you are still hesitant about which material to choose, you can contact us for free. legensilico will offer you more free and other value-added services.
FAQ
Silicone vs EPDM vs Other Rubbers
Natural rubber: Its tensile strength, elongation, and wear resistance are superior to those of EPDM and silicone, but its ozone resistance is weak. It is suitable for highly wear-resistant scenarios such as tire treads, but not for outdoor or high-temperature environments.
Styrene-butadiene rubber (SBR): It has the lowest cost and better wear resistance than silicone and EPDM, but its heat resistance and weather resistance are poor. It is mostly used for daily necessities with low performance requirements, such as shoe soles and rubber hoses.
Nitrile butadiene rubber (NBR): Outstanding oil and fuel resistance, capable of withstanding extremely cold temperatures of -30℃. Automotive oil seals and oil pipelines are commonly used, but their weather resistance and heat resistance are not as good as those of EPDM.
Chloroprene rubber: Its compression set is similar to that of EPDM, and its ozone resistance is comparable, but its water expansion resistance is not as good as that of EPDM. It is suitable for general seals but performs worse than EPDM in extreme environments.
EPDM vs Silicone Gasket
Silicone is heat-resistant and outstanding. It is not easy to soften and leak when used for sealing high-temperature equipment such as ovens and steam pipe joints. Silicone has good biocompatibility and is safe for contact with food or medical scenarios. However, it becomes hard and brittle at low temperatures and may crack in cold outdoor areas.
EPDM has excellent weather resistance. It can withstand long-term outdoor exposure to ultraviolet rays without cracking. It has a low water expansion rate and a long service life when used for sealing water pipes and water tanks. It is resistant to polar solvents but is prone to oxidation and failure when the temperature exceeds 150℃.
If your product requires high-temperature sealing, choose silicone. If outdoor weather resistance or water resistance is emphasized, choose EPDM. Both have their own suitable scenarios.
EPDM vs Silicone O-ring
An O-ring is a mechanical gasket, usually made of rubber. The advantage of silicone lies in its ability to maintain elasticity at high temperatures, and it is generally used for sealing rings of steam pipes. The advantage of EPDM lies in its weather resistance. You can use EPDM O-rings on outdoor equipment.
