Understand the basic cognition of PVC transparent particles

2020-11-28

PVC transparent granular rubber is the base material (basic raw material) for polyvinyl chloride plastic molding, and other auxiliary materials need to be added during the actual molding time. PVC (Polyvinyl Chloride) Chemical and physical properties Rigid PVC is one of the widely used plastic materials. PVC material is a non-crystalline material. In actual use, PVC materials often add stabilizers, lubricants, auxiliary processing agents, pigments, impact agents and other additives.

  PVC transparent particlesThe material has non-flammability, high strength, weather resistance and excellent geometric stability. PVC has strong resistance to oxidants, reducing agents and strong acids. However, it can be corroded by concentrated oxidizing acids such as concentrated sulfuric acid and concentrated nitric acid and is not suitable for contact with aromatic hydrocarbons and chlorinated hydrocarbons.

The melting temperature of PVC during processing is a very important process parameter. If this parameter is not appropriate, it will cause material decomposition. The flow characteristics of PVC are quite poor, and its process range is very narrow. In particular, PVC materials with large molecular weights are more difficult to process (such materials usually need to be added with lubricants to improve flow characteristics), so PVC materials with small molecular weights are usually used. The shrinkage rate of PVC is quite low, generally 0.2~0.6%.

PVC is a heat-sensitive plastic, and the PVC formulation can contain no plasticizer. For example, rigid pipe, PVC rigid film, PVC twisted film, etc. But there must be no heat stabilizer: In general PVC products, the amount of heat stabilizer is 5~8phr; if transparent PVC formula is used, the organotin heat stabilizer used is combined with epoxy soybean oil, and the amount of organotin is 1.5~ 2.5phr, and the amount of epoxide is 3~5phr.

The raw material of PVC (polyvinyl chloride) particles is a strong polar polymer. Because of the large intermolecular force, the softening temperature and melting temperature are higher. Normally, the melting temperature of the modified PVC particles is 160℃-210 Between ℃, the substituted chlorine group in it will easily cause the PVC monomer to undergo de-HCL reaction, thereby causing degradation.

In the process of processing, the performance of pure PVC is extremely unstable after being heated, and decomposition reaction is prone to occur. It begins to decompose slightly when the temperature reaches 90°C, and when the temperature reaches 120°C, a more obvious decomposition reaction begins. Because the decomposition temperature of the PVC particle raw material is much lower than the melting temperature, that is to say, it starts to decompose before heating. Therefore, the PVC particle raw material cannot be processed by thermoplastic methods, and must be modified before proceeding. The processing is designed so that its decomposition temperature is higher than the melting temperature to ensure that it can melt and flow without decomposition during processing.


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