3 measures to improve the aging properties of plasticized layer
The aging characteristics of the plasticized layer on the surface of bamboo plywood have different forms, but they are all related to the molecular structure of the resin. Therefore, the key to improving the aging resistance of the surface plasticized layer is to change the molecular structure of the resin, that is, to modify the resin. Sex.
For phenolic resins, they can be modified with melamine. The modified adhesive is obtained by polycondensation of melamine, phenol and formaldehyde in the presence of a basic catalyst. The modified phenolic resin has a change in its molecular structure, which enhances the flexibility and elasticity of the resin, reduces its brittleness, and improves its aging resistance. There are two methods for modifying the melamine resin, one is an internal plasticization method; the other is an external plasticization method. The external plasticization method generally adds a certain proportion of plasticizer to the melamine resin. Plasticizers are thermoplastic resins or low molecular substances that soften rigid molecular chains and are easy to move. The added plasticizer should have good compatibility with melamine and good stability after dissolution. Generally, high-boiling esters with lower vapor pressure are used as plasticizers, such as phthalic acid, phthalic acid. Dioctyl ester, dibutyl sebacate, and the like. Low molecular weight polyesters, polyurethanes can also be used as plasticizers, or some flexible polymers can be blended with melamine resins. These flexible polymers are polyvinyl formal, polyvinyl acetate resin, alcohol. Acid resin, etc.
The internal plasticization method is to add a polyfunctional monomer modification component to the polycondensation process during the polycondensation of the melamine resin, and introduce another molecular chain in the molecular chain of the melamine resin to make the mother nucleus of the melamine The distance between the lengths is lengthened and the molecules are enlarged to soften the rigid molecules. The addition of such a compound separates the functional group hydroxymethyl group, makes the polycondensation slow, and reduces the degree of polymerization, thereby increasing the fluidity of the resin. Such compounds are usually compounds containing -NH2, -NH groups such as amides, thioureas, carbamates, sulfonamides and the like, with toluenesulfonamide being more commonly used. In addition, in the hot pressing process, when using the cold-hot-cold process, the pressure relief temperature should be below 50 °C, so that the plate is gradually cooled under pressure, to reduce the influence of thermal stress on the deformation of the plate, and improve the surface of the plate. Flatness
The aging characteristics of the plasticized layer on the surface of bamboo plywood have different forms, but they are all related to the molecular structure of the resin. Therefore, the key to improving the aging resistance of the surface plasticized layer is to change the molecular structure of the resin, that is, to modify the resin. Sex.
For phenolic resins, they can be modified with melamine. The modified adhesive is obtained by polycondensation of melamine, phenol and formaldehyde in the presence of a basic catalyst. The modified phenolic resin has a change in its molecular structure, which enhances the flexibility and elasticity of the resin, reduces its brittleness, and improves its aging resistance. There are two methods for modifying the melamine resin, one is an internal plasticization method; the other is an external plasticization method. The external plasticization method generally adds a certain proportion of plasticizer to the melamine resin. Plasticizers are thermoplastic resins or low molecular substances that soften rigid molecular chains and are easy to move. The added plasticizer should have good compatibility with melamine and good stability after dissolution. Generally, high-boiling esters with lower vapor pressure are used as plasticizers, such as phthalic acid, phthalic acid. Dioctyl ester, dibutyl sebacate, and the like. Low molecular weight polyesters, polyurethanes can also be used as plasticizers, or some flexible polymers can be blended with melamine resins. These flexible polymers are polyvinyl formal, polyvinyl acetate resin, alcohol. Acid resin, etc.
The internal plasticization method is to add a polyfunctional monomer modification component to the polycondensation process during the polycondensation of the melamine resin, and introduce another molecular chain in the molecular chain of the melamine resin to make the mother nucleus of the melamine The distance between the lengths is lengthened and the molecules are enlarged to soften the rigid molecules. The addition of such a compound separates the functional group hydroxymethyl group, makes the polycondensation slow, and reduces the degree of polymerization, thereby increasing the fluidity of the resin. Such compounds are usually compounds containing -NH2, -NH groups such as amides, thioureas, carbamates, sulfonamides and the like, with toluenesulfonamide being more commonly used. In addition, in the hot pressing process, when using the cold-hot-cold process, the pressure relief temperature should be below 50 °C, so that the plate is gradually cooled under pressure, to reduce the influence of thermal stress on the deformation of the plate, and improve the surface of the plate. Flatness
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