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HUALONG CASTING MATERIAL

Hardening mechanism of Alkaline phenolic resin

Release time:

2022-06-03 09:53

  In the hardening reaction of Alkaline phenolic resin, the base in the resin reacts with the ester first, forming the carbonate of the alkali metal, releasing the alcohol. After the alkali in the resin forms carbonate, it is in a reaction state, and a cross-linking reaction can occur at normal temperature to bond the sand grains, so that the molding sand has the necessary strength.

Alkaline phenolic resin

  Since the organic ester as the Alkaline phenolic resin hardener is a component involved in the resin hardening reaction, it is different from other resin self-hardening sand in which the hardener only plays a catalytic role and does not participate in the reaction. It cannot be adjusted by changing the amount of hardener added. Sand hardening rate and ejection time.

  The amount of organic ester added is generally 20-25% of the resin, which is slightly different due to the variety of Alkaline phenolic resin and hardener. If the amount of organic ester added is insufficient, the mold will be difficult to harden; if the amount of organic ester added is too high, the mixed sand and sand mold will feel slippery, and may cause a reaction at the mold-metal interface, affecting the surface quality of the casting. The hardening rate and mold release time of self-hardening sand should be adjusted by changing the grade of hardener.

  The Alkaline phenolic resin hardened by organic esters, under the action of organic esters, the Alkaline phenolic resin only undergoes partial cross-linking reaction at room temperature, and the molding sand still maintains a certain plasticity when the mold is started. The process of cross-linking reaction occurs again, which is commonly referred to as secondary hardening.

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