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I. Core Properties of Common Rubbers II. Differences and Applications of Common Rubbers Note: Practical rubber products often contain pigments, so color cannot be used as the sole basis for identification. The most reliable methods are: – Checking the material marking (e.g., markings on oil seals) – Consulting your supplier For simple identification, you can combine: – Oil resistance test (observe swelling after immersion) – Burning characteristics (e.g., CR is self-extinguishing) III. Advantages and Disadvantages of Common Rubbers Natural Rubber (NR) Main Advantages: Excellent elasticity, tensile strength, and tear resistance; good processability. Main Disadvantages: Poor resistance to oil, ozone, and heat aging; narrow operating temperature range. Styrene-Butadiene Rubber (SBR) Main Advantages: High abrasion resistance, heat resistance, low cost, and the highest production volume. Main Disadvantages: Slightly lower elasticity and cold resistance; poor resistance to oil. Butadiene Rubber (BR) Main Advantages: Outstanding elasticity, abrasion resistance, and cold resistance. Main Disadvantages: Poor tear resistance. Chloroprene Rubber (CR) Main Advantages: Good overall performance; resistant to oil, weathering, flame, and ozone aging. Main Disadvantages: High density, average low-temperature performance, and relatively expensive. Nitrile Rubber (NBR) Main Advantages: Excellent oil resistance (second only to fluorocarbon rubber, etc.), good abrasion resistance, and airtightness. Main Disadvantages: Poor cold resistance, ozone resistance, and electrical insulation. Ethylene Propylene Diene Monomer (EPDM) Main Advantages: Superior resistance to ozone, weathering, and aging; resistant to hot water and steam; good electrical insulation. Main Disadvantages: Poor oil resistance; slow vulcanization; poor self-adhesion. Butyl Rubber (IIR) Main Advantages: Best gas and water tightness; heat and aging resistance. Main Disadvantages: Poor tack, slow vulcanization, and poor oil resistance. Silicone Rubber (SI) Main Advantages: Widest temperature resistance range, non-toxic, insulating, and ozone-resistant. Main Disadvantages: Low mechanical strength, poor oil and solvent resistance, and high cost. Fluorocarbon Rubber (FKM) Main Advantages: High-temperature resistance, oil resistance, superior chemical resistance, and aging resistance. Main Disadvantages: Very expensive, poor processability, average cold resistance, and low elasticity. Chlorosulfonated Polyethylene (CSM) Main Advantages: Excellent abrasion resistance, weather resistance, ozone resistance, and good flame retardancy. Main Disadvantages: High cost, poor rebound, and compression set properties. IV. Quick Selection Guide Great elasticity → Choose Natural Rubber (NR) Great wear resistance & low cost → Choose Styrene-Butadiene Rubber (SBR) Oil resistance → Choose Nitrile Rubber (NBR) (general use) or Fluoro Rubber (FKM)(extreme conditions) Weather & aging resistance → Choose Ethylene Propylene Rubber (EPDM) Air & water tightness → Choose Butyl Rubber (IIR) Wide temperature resistance → Choose Silicone Rubber (SI) Super corrosion resistance → Choose Fluoro Rubber (FKM)

Standard O-ring sizes are defined by two core dimensions: inner diameter (d₁) and cross-section diameter (d₂, wire diameter). All major standards follow these two key parameters, together with matching tolerances and standardized series rules. The sizing principles and common standards are as follows: 1. Core Dimension Standards: All standards first establish a standard series for the cross-sectional diameter d2 (wire diameter) (e.g., 1.8, 2.4, 3.1, 5.7, 7.0 mm, etc.), and then match the wire diameter with standardized values for the inner diameter d1. Furthermore, d1 increases in fixed increments to avoid a chaotic array of specifications. 2. Dimensioning Rules: The general notation is d1×d2 (inner diameter × wire diameter). In some cases, the outer diameter (d1+2×d2) may be specified, but the standard core remains based on d1 and d2; 3. Tolerance Specifications: Different standards define upper and lower deviations for d1 and d2 based on size ranges (e.g., small inner diameter/large inner diameter, fine wire diameter/coarse wire diameter) to ensure interchangeability. Main Common Standards (Most Widely Used in Industry)： – GB/T 3452.1 (Chinese National Standard) The mainstream standard in China. It defines a narrow series (1.0–4.0 mm) and a wide series (5.7–12.0 mm) for crosssection diameters. Inner diameters are matched to each crosssection, covering most general industrial applications. – AS568 (American Standard) Widely used globally, especially in hydraulic and pneumatic systems. Each part number corresponds to a unique d₁×d₂ size (e.g., AS568010 = 1.78 × 1.78 mm). Key crosssections include 1.78, 2.62, 3.53, and 5.33 mm, widely compatible with American and European equipment. – JIS B 2401 (Japanese Standard) Divided into Type P (general) and Type G (precision). Its crosssection and inner diameter series differ slightly from GB and AS568, mainly for Japanese machinery. – ISO 3601 (International Standard) Highly aligned with GB/T 3452.1, serving as the unified global basic specification with consistent core dimension series. Key Notes: Standards clearly specify the matching rules for minimum groove dimensions. The Oring inner diameter d₁ and crosssection d₂ must be compatible with the bore and width of the installation groove (typical compression ratio: 10%–20%). This is also a necessary design requirement supporting size standardization.

What’s the biggest complaint that seal manufacturers fear most? It’s definitely leakage. When you remove a leaking O-ring, you’ll often discover a heartbreaking sight: it’s no longer the smooth, plump O-ring it once was; its cross-section has turned square or flattened into a D-shape. If you squeeze it with your fingers, it feels rock-hard and completely lacks elasticity. In the rubber industry, this phenomenon has a technical term: compression set. When faced with this issue, many technicians’ first instinct is to say, “Use a higher-quality raw rubber!” or “Add more carbon black!” The result is often higher costs with little improvement. Today, Dr. will take you into the molecular world of rubber to see exactly how your seals “die.” Part 1: Understanding the Basics—What Is Compression Set? In simple terms, compression set refers to the percentage of height that rubber cannot recover after being compressed under a specific temperature for a period of time and then released. In laboratory testing, we use a precise scientific formula to calculate it:  C: Compression set value(The lower the value, the better the resilience and the longer the service life.)  h₀: Original height of the test specimen  h₁: Height of the specimen after recovery  h₈:Height of the spacer (limiter) For seals, CS is a critical indicator. When CS reaches 80% or even 100%, the rubber completely loses its elastic memory. Even the slightest vibration will cause fluids — oil or water — to leak through the gaps. Part 2: The Four Main Culprits — Who Killed Rubber’s Elasticity? Culprit 1: “Genetic Defects” in the Vulcanization System This is the most critical factor determining compression set! The common sulfur vulcanization system (CV) we typically use primarily produces polysulfide bonds (-S_x-). Fatal flaw: Although polysulfide bonds offer good tear resistance, their bond energy is extremely low. Under high temperatures and compression, these bonds will break. After breaking, the molecular chains slide into new, flattened positions and then re-crosslink (forming new chemical bonds). Result: When the pressure is removed, the newly formed chemical bonds tightly hold the molecular chains in place, preventing them from bouncing back. Your O-ring is thus “locked” in a flattened state. Culprit 2: Under-Curing & Lack of Post-Curing Phenomenon: To maximize production output, many factories push curing time to the limit (often not even reaching t90). Consequence: A large number of unreacted crosslinking agents and active sites remain inside the rubber compound. When the seal is compressed under high-temperature operating conditions, these unreacted substances undergo secondary crosslinking. Crosslinking while in a compressed state is like permanently “fixing” the flat shape into its structure. This is especially true for FKM and VMQ silicone: Without standard post-curing (typically oven curing at around 200°C for several hours) to remove volatile components and perfect the crosslinking network, their compression set values will be extremely poor. Culprit 3: Stress Relaxation and Molecular Chain Breakage at High Temperatures High temperatures are the arch-enemy of rubber. When subjected to prolonged pressure at 100°C or even 150°C: Physical relaxation: The thermal motion of the rubber’s polymer chains intensifies, causing irreversible slippage between chain segments. Chemical degradation: The main chain breaks down under the combined effects of heat and oxygen. Once the spring breaks, it naturally cannot spring back. Culprit 4: Escape of Plasticizers (Oil) If your formula contains large amounts of processing oil to reduce hardness or cost, these plasticizers will be extracted or evaporated when the seal is exposed to hot oil or chemical media. Volume shrinkage combined with stress loss causes the seal to degrade and collapse rapidly. Part 3: Doctor’s Prescription — How to Save Your Seals? Now that we’ve identified the culprits, we can target solutions effectively. If you want to produce high-end seals with ultra-low compression set, here is your practical prescription: 1.Overhaul the Vulcanization System (Top Priority) Abandon conventional sulfur systems: Switch to EV (Efficient Vulcanization) or SEV (Semi-Efficient Vulcanization) systems. By increasing accelerator dosage and reducing sulfur content, you form more stable monosulfide and disulfide bonds. Ultimate solution: Peroxide curing system (e.g., DCP, BIPB) Peroxide crosslinking creates carbon-carbon bonds (CC), which have extremely high bond energy and excellent heat resistance. These bonds rarely break under compression. For EPDM or NBR seals, whenever the customer requires low compression set, choose a peroxide system without hesitation. 2. Choose the Right Base Rubber For applications above 150°C, NBR will fail no matter how you adjust the formula. Upgrade directly to: – HNBR (Hydrogenated Nitrile Rubber) – EPDM (for water resistance, not oil resistance) – ACM (Acrylate Rubber) – FKM (Fluoroelastomer) 3. Strictly Implement Post-Curing For high-end FKM and silicone seals, never save on oven time! Post-curing is mandatory. It not only reduces compression set but also completely removes toxic or corrosive byproducts from the vulcanization process. 4. Optimize Fillers and Plasticizers Use carbon black with low structure and moderate particle size (such as N550, N774), or highly active silica (with coupling agents). High-structure carbon black tends to form a rigid network that restricts the recovery of molecular chains. Control the amount of liquid plasticizers, and choose low-volatility, extraction-resistant, eco-friendly oils or ester plasticizers. A compression set is essentially a microscopic war between destruction and reconstruction. The “failure” of a seal is not sudden death. It is the gradual compromise and rearrangement of the internal crosslinking network under high temperature and compression. As formulators and process engineers, our mission is to give rubber the strength to resist deformation —using the most stable chemical bonds (CC bonds, monosulfide bonds) and the most compact vulcanized network. Next time you face leakage issues, don’t blindly add more carbon black. Ask yourself: Is your vulcanization system correct?

Irregularly shaped sealing rings (non-standard shapes such as rectangular, L-shaped, etc.) typically rely on manual trimming due to their soft material or complex structure. The reasons are as follows: 1.Material Softness and Deformation Susceptibility Material Properties: Soft materials like rubber or silicone have high elasticity, making them prone to deformation or damage under mechanical clamping or cutting forces during machine trimming, compromising geometric precision. Manual Advantage: Human operators can dynamically sense material conditions and adjust pressure and angle to avoid overexertion, ensuring edge flatness. 2.Complex Geometry and Poor Adaptability Non-standard Contours: Irregular sealing rings often feature curves, angled edges, or intricate structures that are challenging for generic machinery (e.g., laser cutters, stamping dies) to precisely replicate. Custom fixtures or repeated adjustments are costly. Manual Flexibility: Workers can directly trim using hand tools to match actual shapes, offering strong adaptability, especially for small batches or prototypes. 3.Precision and Surface Quality Requirements Tight Tolerances: Sealing rings require minimal clearance with mating components (e.g., hydraulic systems). Machine cutting may introduce burrs or micro-errors, while manual trimming allows fine finishing via sandpaper or files to enhance surface smoothness. Stress-Free Processing: Mechanical methods may induce residual internal stress, whereas manual operations reduce molecular chain damage, prolonging service life. 4. Cost-Efficiency Trade-offs Low-Volume Production: For small batches, custom automation is uneconomical, making manual trimming more practical. Rapid Adjustments: Manual processes enable immediate defect correction (e.g., flash, material defects) based on quality inspections, minimizing rework waste. 5. Specialized Process Requirements Thermal Trimming Limitations: Some soft materials require low-temperature or solvent-assisted softening for trimming, where manual control ensures safety and precision. Seam Handling: For sealing rings with bonded joints, manual trimming and sanding are necessary to ensure flat, void-free bonding surfaces. Alternative Solutions Precision Molds: For high-volume production with fixed shapes, custom molds can reduce post-trimming needs. Laser Cutting: Suitable for harder materials or simple irregular shapes, though soft materials may suffer from thermal degradation at edges. Semi-Automated Systems: Pneumatic trimming machines paired with flexible fixtures balance efficiency and precision but still require manual assistance. Summary Manual trimming remains the preferred method for soft irregular sealing rings, balancing material behavior, cost, and quality—particularly in low-volume, high-precision scenarios. However, advancements in flexible manufacturing (e.g., vision-guided robotic trimming) may reduce reliance on manual processes in the future.

Silicone sealing ring is a kind of sealing ring, which is made of various silica gel as raw materials for fixing the ring cover, so that it can be fitted with the gap between the ring or the washer on the bearing, and the sealing ring made of other materials has more excellent performance in preventing water or oil leakage. At present, it is mainly used for waterproof sealing and preservation of daily supplies such as fresh-keeping box, rice cooker, drinking machine, lunch box, insulated box, fresh-keeping box, water cup, oven, magnetized cup, coffee pot, etc. It is convenient to use, safe and environmental protection, and is deeply loved by everyone. So today, let’s take a look at the silicone sealing ring. (Silicone sealing ring) (ordinary rubber sealing ring) 1.Excellent weather resistance Weather resistance refers to the influence of direct sunlight, temperature changes, wind and rain and other external conditions, and a series of aging phenomena such as fading, discoloration, cracking, powder and strength decline, ultraviolet irradiation is the main factor to promote the aging of products. Si-O-Si bond in silicone rubber is very stable to oxygen, ozone and ultraviolet rays, and has excellent resistance to ozone and oxide erosion. In the absence of any additives, it has excellent weather resistance, and does not crack even if it is used outdoors for a long time. It is generally believed that silicone rubber seals can be used outdoors for more than 20 years. 2.Material safety and environmental protection Silicone rubber has its unique physiological inertia, non-toxic, tasteless, no smell, good preservation effect, and less interference by the external environment, long-term use unchanged yellow, do not fade. And in line with the national food and medical health standards, mostly used in food, medicine, aluminum silver pulp and various oils filtration and impurity removal. 3.Good electrical insulation performance Organic silicone has excellent electrical insulation properties, corona resistance (can resist quality declination) and arc resistance (resistance to deterioration caused by high voltage arc action) is also very good. 4.High permeability and selectivity of gas transmission Because the molecular structure of silica gel makes the silicone sealing ring have good permeability and good selectivity for gas, the permeability of silicone rubber to air, nitrogen, oxygen, carbon dioxide and other gases at room temperature is 30-50 times higher than that of natural rubber. 5.Hygroscopic performance The surface energy of the silica gel ring is low, which has the absorption function of water in the environment and plays the role of isolation. 6.Wide range of high and low temperature resistance High temperature resistance: silicone sealing ring compared with ordinary rubber has better heat resistance, can be heated under high temperature without deformation without harmful substances. It can be used almost forever at 150 ° C without performance changes, can be used continuously for 10,000 hours at 200 ° C, and can be used for a period of time at 350 ° C. Widely used in applications requiring heat resistance, such as: hot water bottle sealing ring. Low temperature resistance: ordinary rubber -20 ° C ~ -30 ° C will become hardened and brittle, while silicone rubber still has good elasticity at -60 ° C ~ -70 ° C, some special formulations of silicone rubber can also withstand more harsh extremely low temperatures, such as: low temperature sealing rings, the lowest can reach -100 ° C. 7.High permeability and selectivity of gas transmission Because the molecular structure of silica gel makes the silicone sealing ring have good permeability and good selectivity for gas, the permeability of silicone rubber to air, nitrogen, oxygen, carbon dioxide and other gases at room temperature is 30-50 times higher than that of natural rubber. Disadvantages of silicone rubber sealing ring Tensile strength and tear strength mechanical properties are poor For stretching, tearing, and strong wear in the working environment, it is not recommended to use silicone seals, which are usually only used for static sealing. Although silicone rubber is compatible with most oils, compounds and solvents, it has good acid and alkaline resistance, but it has no resistance to alkane, hydrogen and aromatic oils. Therefore, it is not suitable for use in an environment with a working pressure of more than 50 pounds. In addition, it is not recommended to use silicone seals in most concentrated solvents, oils, concentrated acids and diluted caustic soda solutions. The price is relative to other materials, silicone sealing rubber ring, the manufacturing cost is relatively high.