Hardening mechanism of phenolic resin.Phenol and formaldehyde in the synthesis reaction equipment, the resin obtained by addition and appropriate polycondensation reaction, usually a mixture of low molecular weight oligomers and various methylol phenols, the phenolic resin only forms a cross-network (or body type) structure has excellent performance after use, including mechanical properties, electrical insulation properties, chemical stability, thermal stability and so on.
The hardening of phenolic resin is the process of transforming it into a network structure. durable cutting off wheel
shows gelation And in the two stages of complete curing, this transformation is not only a physical process, but also a chemical process. Therefore, the hardening of the phenolic resin is not the solidification of the melt in the general sense of cooling below the melting point, but the cross-linking of the molecular (cylindrical) molecules in the concept of polymer chemistry (the formation of the network-like molecules leads to the loss of solubility and fusibility). The curing of the phenolic resin, after obtaining good physical properties, loses solubility, fusibility and no longer processability. Therefore, the curing process must be composed of a phenolic resin as a binder. The use of plastics, paints and various engineering materials or molding processes is completed.
The hardening process exhibits the following characteristics:
(1) The structural factors (composition, molecular weight, reaction functionality, etc.) of the resin before sclering are significantly affected;
(2) The hardening reaction is significantly affected by the catalyst, curing agent, resin pH, etc.;
(3) The hardening process has a thermal effect;
(4) The hardening rate is significantly affected by temperature and pressure;
(5) By-products (such as water, formaldehyde, etc.) are produced during the hardening process;
(6) The hardening reaction is an irreversible process.