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What are the characteristics of polyurethane catalyst foaming applications?
Edit:Nantong Yutai Chemical Products Co., Ltd.   UpDate:2019-10-11

Polyurethane foams have a variable polymer structure to meet a wide range of applications. This structural difference is caused not only by the difference between the isocyanate used as the starting material and the polyol, but also by the different reactions carried out by these raw materials. These reactions are strongly influenced by the type and amount of catalyst used. The reaction of the isocyanate with the polyol is referred to as a gelation reaction, ultimately resulting in a carbamate. The reaction of isocyanate with water (called a foaming reaction) ultimately produces dolphins. When the carbamate is further reacted with isocyanate at night, crosslinking may occur, and methyl formate and crater may be produced separately. Isocyanates self-condense into trimers in several different ways.


The choice of polyurethane catalyst affects the reactivity of the overall foaming system and the selectivity of some of the individual reactions described above. The reactivity of the foaming system is indicated by the activation time of the system, the curing process, the demolding or curing time. The selectivity of the reaction varies with the choice of catalyst, affecting the equilibrium of the reactions occurring, the type and sequence of polymer chains formed, and the fluidity of the foaming system, thereby affecting the final foam processing and physical properties. The most commonly used catalysts for polyurethane foaming are tertiary amines, quaternary amines, amine salts and metal nucleic acid salts (usually SnII, SnIV or K+). A tertiary amine is used to promote gelation. Foaming and crosslinking reactions. Limb salts and heat-sensitive amines, such as diazobicycloundecane, are used to provide a blocking effect. Metal salts strongly influence the gelation reaction.


The stannous compound (SnII) is low in cost but easily hydrolyzed and unstable. Its typical use is to be able to meter separate streams of applications, such as soft blocks. The tin compound (SnIV) is not easily hydrolyzed and can be incorporated into systems such as soft molded and rigid foams. For example, specific classes of compounds such as quaternary amines, potassium nucleic acids, tris(dimethylaminomethyl)phenol and 2,4,6-tris[3-(dimethylamino)-n-propyl]hexahydrotriethyl Alkyl ammonium and the like. Trimerization is highly selective. Flexible Block Foam Flexible Block Polyether polyol based foam is a typical tertiary amine catalyzed reaction product used with organotin catalysts. The colloidal catalyst may be a dilution of a pure compound such as triethylenediamine and bis(dimethylaminoethyl)ether, or a mixture of optimized properties. A typical tin catalyst for soft block foaming is pure or diluted stannous octoate. Diluted products (including amines and tins) are designed to address issues such as raw material handling, metering accuracy and pumping viscosity limits. The use of high quality blends in specialized foaming equipment can improve the processing, expand the range of formulations, and produce small differences in the physical properties of the foam.



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