chloroprene rubber

In the field of specialty rubber materials, chloroprene rubber (CR) has long held an irreplaceable position due to its excellent weather resistance, flame resistance, oil resistance, and chemical corrosion resistance. Among the various types of chloroprene rubber, sulfur-modified chloroprene rubber, with its unique molecular structure design, exhibits excellent physical and mechanical properties and adhesion, making it a key focus in the rubber products industry. This article will delve into the SN32 and SN12 series of sulfur-modified chloroprene rubber produced using a low-conversion polymerization process. These two series of products, through specific process control, overcome the challenges of Mooney viscosity stability in traditional sulfur-modified rubber, providing a more uniform and reliable raw material choice for industrial products.     1. Characteristics of Sulfur-Modified Process and Advantages of Low-Conversion Polymerization The core of sulfur-modified chloroprene rubber lies in the introduction of sulfur as a regulator during the polymerization process, and the use of thiuram for chain termination. Compared with traditional thiol-modified rubber, sulfur-modified rubber generally has higher tear strength, better adhesion, and superior dynamic fatigue performance. The SN32 and SN12 series discussed here are based on a low-conversion emulsion polymerization process. This process is key to improving product quality stability: Uniformity of Mooney viscosity: By strictly controlling the monomer conversion rate during polymerization, it effectively avoids polymer gelation or excessively broad molecular weight distribution caused by over-reaction. This means that each batch of rubber produced maintains a very narrow range of Mooney viscosity fluctuations, greatly improving the consistency of compounding and processing in downstream factories. Optimization of molecular chain structure: This process, combined with advanced molecular weight regulation technology, results in chloroprene rubber with low crystallinity. Low crystallinity means that the material is softer at room temperature and less prone to premature hardening, thus ensuring the flexibility and service life of the products. Improved processing safety: Through precise polymerization control, these two series of products significantly improve the processing safety of the rubber compound while maintaining the high strength of sulfur-modified rubber, reducing the risk of dead stock and scorching.   2. SN32 Series The SN32 series is positioned as a general-purpose sulfur-modified chloroprene rubber. From a molecular structure perspective, it undergoes a special adjustment of the degree of mechanical shearing and chain scission. According to technical data, the SN32 series has a lower degree of molecular chain mechanical shearing and scission than the SN12 series, but its thermal stability is stronger than the SN12 series. This characteristic determines that SN32 performs better in high-temperature environments.   Model SN321 SN322 SN323 Mooney Viscosity(100℃1+4) 37-49 50-65 66-75 Mooney Scorch (MSt5) min≥ 25 25 25 500% Modulus (Mpa) 2-5 2-5 2-5 Tensile Strength (MPa) ≥ 22 22 22 Elongation at Break (%) ≥ 800 800 800 Volatile Matter (%) ≤ 1.3 1.3 1.3 Ash Content % ≤ 1.0 1.0 1.0   ♠ Physical and Mechanical Properties and Processing Characteristics The SN32 series exhibits excellent physical and mechanical properties, with tensile strength greater than 22 MPa and elongation at break above 800%. Compared with the traditional CR322(such as Polychloroprene Rubber CR3221), the advantages of the SN32 series are mainly reflected in the processing stage: Easy to plasticize and compound: The rubber compound absorbs powder quickly and disperses evenly. Excellent extrusion molding: The rubber sheet surface is flat and smooth, with low shrinkage, which is crucial for manufacturing extruded products requiring high dimensional accuracy (such as sealing strips and hoses). Good appearance quality: The surface of the product is smooth after vulcanization, with a low defect rate. ♠ Grade Subdivision  The SN32 series is subdivided into three main grades according to different Mooney viscosity (ML100℃ 1+4), corresponding to different hardness and processing requirements: SN321 (Mooney 37-49): Low viscosity, good fluidity, suitable for complex mold injection molding. SN322 (Mooney 50-65): Medium viscosity, most versatile. SN323 (Mooney 66-75): High viscosity, higher physical strength, suitable for high-load products. ♠ Key Applications Thanks to its excellent oil resistance, chemical resistance, ozone aging resistance, and non-flammability, the SN32 series is widely used in mining conveyor belts, power transmission belts, dust covers, and various sealing parts. In particular, its excellent thermal stability makes it perform outstandingly in power transmission components involving frictional heat generation.   3. SN12 Series ♠ Outstanding Scorching Safety and Anti-Aging Properties The most significant feature of the SN12 series is its long scorching time. In rubber processing, scorch time determines the "safety window" of the operation. A longer scorch time means that the rubber compound is less prone to premature vulcanization (scorch) during high-temperature mixing and molding, which is crucial for thick products or injection molding processes with complex structures. Furthermore, the SN12 series blended rubber exhibits superior vulcanization characteristics, particularly in terms of aging resistance. Data shows that its products have better aging resistance than the GNA type, and also possess good electrical properties and weather resistance.   Model SN121 SN122 TBD-102 Mooney Viscosity(100℃1+4) 30-50 51-65 30-50 Mooney Scorch (MSt5) min≥ 25 25 25 500% Modulus (Mpa) 2-5 2-5 2-5 Tensile Strength (MPa) ≥ 23 23 23 Elongation at Break (%) ≥ 850 850 850 Volatile Matter (%) ≤ 0.8 0.8 0.8 Ash Content % ≤ 1.0 1.0 1.0   ♠ Physical Performance Advantages Although both are sulfur-cured types, the SN12 series has slightly higher tensile strength (≥23 MPa) and elongation at break (≥850%) than the SN32 series. This indicates that the SN12 series has greater molecular chain flexibility and toughness, allowing it to withstand greater deformation without damage. ♠ Differences between SN122 and SN121 The main difference lies in Mooney viscosity; SN122 (51-65) is slightly higher than SN121 (30-50). Users can choose based on the power of their mixing equipment and process requirements. ♠ Comparison with CR121 Compared to traditional CR121(such as Polychloroprene Rubber CR1212), the SN12 series has better processing performance, especially in plasticizing, mixing, and extrusion molding, with less shrinkage and better product appearance quality.   4. Application Scenario Analysis and Series Selection Recommendations Both the SN32 and SN12 series possess the characteristic "all-round" properties of chloroprene rubber: oil resistance, heat resistance, flame retardancy, and suitability for rubber products with special requirements for comprehensive performance. However, in actual engineering applications, engineers should select materials based on specific needs. ♠ Power Transmission and Mining Fields (Conveyor Belts, Drive Belts) This is the core application area for sulfur-cured chloroprene rubber. Mining conveyor belts require extremely high flame retardancy and wear resistance, as well as good adhesion between the rubber compound and the reinforcing materials (such as nylon and polyester canvas). Recommendation: If thermal stability of the rubber compound is important (e.g., drive belts in high-temperature environments), the SN32 series is the preferred choice. Recommendation: If tear strength and a long scorch time are important (facilitating long-term vulcanization molding of large conveyor belts), the SN12 series is more suitable. ♠ Cable Sheathing and Seals Cable sheathing requires materials with good weather resistance, ozone resistance, and certain electrical insulation properties. The SN32 series, with its excellent extrusion surface smoothness and low shrinkage, is ideal for extruded cable sheathing and profiled sealing strips, ensuring dimensional accuracy and aesthetic appearance of the finished product. ♠ Hoses and Vibration Damping Products The high elongation and tensile strength of the SN12 series make it perform exceptionally well in hoses and damping pads subjected to high-pressure deformation. Its excellent dynamic fatigue resistance can effectively extend the service life of damping products.   The SN32 and SN12 series sulfur-modified chloroprene rubber, produced using a low conversion rate polymerization process, represents the advanced level of current domestic synthetic rubber technology. The SN32 series excels in thermal stability and processing appearance, while the SN12 series is known for its scorch safety and high strength and elongation properties. These two series not only meet the standards of comparable high-end international products (such as DuPont, Lanxess, and Denka) in various physical and chemical indicators, but also achieve uniform and stable Mooney viscosity through process innovation, solving a major pain point of processing instability for rubber product manufacturers. They are ideal base materials for manufacturing high-quality rubber products.   Website: www.elephchem.com Whatsapp: (+)86 13851435272 E-mail: admin@elephchem.com

Thiol-modified chloroprene rubber plays a crucial role in adhesive chloroprene rubber systems due to its unique polymerization control mechanism. Thiol-modified products, especially the SN24 series, SN244X series, and SN23 series, are widely used in shoe adhesives, spray adhesives, high-grade universal adhesives, architectural decorative adhesives, and automotive interiors.   1. Mechanism of Thiol Modification During the polymerization of chloroprene rubber (CR), modifiers significantly affect the polymerization rate, molecular weight, distribution, and controllability of the polymerization process. Thiol modifiers, due to their moderate reactivity, are widely used in the production of adhesive chloroprene rubber. 1.1 More Stable Polymerization Process Thiol modification effectively controls chain growth, maintaining suitable molecular weight and distribution, resulting in good solubility and stable processing properties. This directly affects adhesive viscosity, film-forming characteristics, and long-term storage stability. 1.2 Determining Initial Tack and Final Strength of Adhesives Taking the SN24 series as an example, the molecular structure obtained through thiol regulation exhibits superior film-forming strength. When grafted with MMA (methyl methacrylate), it significantly improves adhesion to various substrates, resulting in higher initial tack and final bond strength. 1.3 Affecting Open Time and Working Window The SN23 series is specifically designed for "adjustable open time." Through meticulous control of the molecular structure, it provides more flexible application times for the footwear and decoration industries, effectively improving operational convenience and production efficiency. Thiol regulation is not merely simple polymerization control; it is a core technical means influencing the application performance of the entire adhesive system, providing a strong technical foundation for complex bonding scenarios.   2. Performance and Application Value of the SN24/SN244X Series Among thiol-regulated chloroprene rubbers, the SN24 and SN244X series are the products with the highest market attention. SN24 focuses on bond strength and grafting applications, while SN244X further optimizes solubility, color, and weather resistance, resulting in more comprehensive overall performance. 2.1 SN24 Series: High-strength, graftable, and widely applicable basic products   ♠ Key features of the SN24 series include: Thiol-modified system for stable molecular weight control MMA grafting adaptability, further improving adhesion to substrates such as metals, leather, and rubber High initial tack and excellent final bond strength Suitable for fast bonding systems ♠ Typical applications: Shoe adhesives in the footwear industry Spray adhesives in the furniture and packaging industries Advanced all-purpose adhesives and engineering adhesives Chloroprene Rubber SN-242A is a widely used product, extensively adopted in footwear adhesive applications due to its strength, fast bonding speed, and ease of use. 2.2 SN244X Series: Upgraded Products with High Solubility, Light Color, and High Weather Resistance Chloroprene Rubber SN-244X series optimizes several key properties based on SN24, making it a higher-end and more stable thiol-modified chloroprene rubber.   ♠ Key advantages include: Faster dissolving speed, improving production efficiency Lighter glue color, suitable for light-colored or appearance-sensitive products High initial bond strength, long holding time, and better weather resistance Less prone to aging after bonding, suitable for outdoor or strong light environments ♠ Typical applications: High-end shoe adhesives Construction and decoration adhesives Automotive interior bonding Furniture and decoration industries For companies requiring "fast dissolution + strong adhesion + high weather resistance," the SN244X series is a typical choice.   3. SN23 Series: Complementary Products Specifically Designed for Adjusting Open Time Unlike the direct application of SN24 and SN244X, the SN23 series acts as a "modifier" in adhesive chloroprene systems. Its core value is adjusting the open time.   3.1 Why is open time so critical? In adhesive applications, too short an open time leads to application difficulties; too long an open time reduces efficiency. Different seasons, application temperatures, and substrate conditions can all cause fluctuations in the final bonding effect. The SN23 series allows for precise adjustment of the adhesive's drying speed and operating window, ensuring stable performance under various environmental conditions. 3.2 Enhanced results when used in conjunction with SN24/SN244X The SN23 series is typically not used alone, but rather in combination with SN24 and SN244X, serving the following purposes: Extending or optimizing adhesive open time Improving sprayability and application feel Optimizing the balance between initial and final bond speeds Enhancing adaptability to complex processes Typical products such as SN236T and SN237T possess suitable solution viscosity and good stability, making them highly valuable in the footwear and industrial adhesive industries.   As industries such as footwear manufacturing, furniture decoration, and automotive interiors demand increasingly higher performance from adhesives, adhesive-grade neoprene rubber is entering a stage of development focused on higher performance, greater controllability, and greater stability.   ♣ The thiol-modified SN24, SN244X, and SN23 series are key components of this trend: SN24 – High strength, graftable, and comprehensive adhesive properties SN244X – An upgraded solution offering fast dissolution, light color, and high weather resistance SN23 – An open-time modifier product that makes production more controllable.   Through proper combination, these adhesives can create more stable, easier-to-process, and more adaptable neoprene adhesive systems, bringing higher efficiency and better bonding quality to end-user industries.   Website: www.elephchem.com Whatsapp: (+)86 13851435272 E-mail: admin@elephchem.com