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Industry news
position: > News > Industry news

Natural rubber vulcanization process

date: 2016-12-06 source: Century creation

  The process of the natural rubber vulcanization rubber macromolecular chain of chemical crosslinking reaction process. Can be roughly divided into three stages:
  Phase 1 for induction phase, sulfur molecules and promoter system (promoting agents, zinc oxide, stearic acid) response naturally a more active intermediate compounds, it further trigger a rubber chain crosslinking of free radicals.
  Phase 2 for crosslinking reaction stage, can be crosslinked chain reaction between free radicals and rubber chain, a natural crosslinking chain.
  Stage 3 to stage of formation of network structure, and at the same time may be crosslinked bond rearrangement and cracking reaction, such as in the late stage of the crosslinking reaction has been largely discontinued, the consequent is mainly crosslinked bond rearrangement and cracking reaction (i.e., "sulfide to return the original" response).
  By glue assumed that stretch strength measurement (or rheometer) as you can see, the whole process can be divided into sulfide sulfide induced, sulfur, is sulfide and sulfur (for natural rubber is vulcanized to return the original) four stages. Sulfide induction period, scorch time, crosslinking have yet to begin, rubber has good liquidity. This stage determines the charred and processing of the security. The end of this phase, the rubber crosslinking and loss of liquidity. Curing the length of the induction period is concerned with nature rubber itself, mainly depends on the YongZhuJi, such as delayed promoter can get longer scorch time, and have higher processing and security. After vulcanization induction period is at a certain speed presulfurization stage of crosslinking. Presulfiding of low degree of crosslinking, and even to late breaking strength of the vulcanizates, elastic also can't reach the expected level, but the tear and dynamic crack performance is better than the corresponding is sulfide. Arriving at is sulfide stage, the analysis of the various physical properties at or near optimal point respectively, or to the performance of the whole balance. Is sulfide stage (sulfide flat area), namely for sulfur phase, there are two situations: "return to the original" phenomenon in a natural rubber (a decrease in tensile modulus), most of the synthetic rubber (except butyl rubber) increase tensile modulus. Not only for any rubber vulcanization when has the crosslinking, also due to the role of heat and other factors of production chain and molecular chain rupture. This phenomenon throughout the vulcanization process. In sulfur phase, if the crosslinking is still dominant, and hard rubber, tensile modulus continues to rise, on the contrary, rubber soft, namely a return to the original.
  Ordinary vulcanization system in vulcanization crosslinking process produces much more volatile sulfur crosslinked bond, it compared with single sulfur crosslinked bond is characterized by a thermal instability, after vulcanization curve performance to reach the maximum torque as the extension of curing time, torque gradually decline.
  Catalysis is one of the important areas of the application of nanometer particle, nanometer particle area ratio and highly active can significantly enhance the catalytic efficiency. Nanometer particles for plastic, traditional coating modification and has achieved obvious results. This work studied the nano zinc oxide as curing activator on the reaction of natural rubber composite vulcanization system, and compared with ordinary zinc oxide role at the same time. Natural rubber SMR20 products (Malaysia); Ordinary ZnO (anqing city zinc oxide factory); Nanometer ZnO feng susquehanna m technology co., LTD. (shanxi).
  Basic recipe (mass ratio) : SMR20 (100), stearic acid (1) O), sulfur (2.5), the accelerator Ⅳ a ring hexyl a 2 a benzothiazole base times sulfonamide (CZ) (1) O), ZnO (5. O).
  According to the conventional method in the mixing machine mixing, on a plate vulcanizing machine sulfide (total working pressure is 100 t, curing temperature is 151 C). RheoTECH (R) a MD type rotor rheometer, the TECH PRO products, angular 4 - _1. , the frequency of 1.7 Hz, vulcanization curve under 151 C test, determination of vulcanization time t.. (in terms of crosslinking degree for 9 o) and the scorch time t. (in the crosslinking degree of 1 o %), and calculate the sulfide to return the original index R, Rt refers to the vulcanization curve after reaching the highest torque fell 0.1 dN m. the time required.
  Using SiTECH (R) electronic tensile machine (TECH PRO companies in the United States), test the mechanical properties of vulcanized rubber at room temperature. WRT the 3 p type thermal analyzer (Shanghai precision instrument factory), 15 ℃ / rain heating rate, temperature range ~ 5 oo C at room temperature, air atmosphere, 10.0 mg samples.

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