Denka A400 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