The film-forming agent is the main component of glass fiber infiltrant, generally accounting for 2% to 15% of the mass fraction of the infiltrant formula, its role is to bond the glass fiber into bundles, in the production of protection of fibers, so that the fiber bundles have a good degree of stiffness, agglomeration, to meet the subsequent process requirements in the glass fiber products. The commonly used film-forming agents in glass fiber infiltrant formulations are polymers, including epoxy resins, polyurethane, polyester, phenolic resins, modified polypropylene dispersions, or emulsions. The performance of film-forming agents mainly depends on the molecular structure and molecular weight of the polymer. For the same film-forming agent, the stiffness of glass fiber can be regulated by the molecular weight of the film-forming agent, and a film-forming agent with high molecular weight will have a higher stiffness of the glass fiber, which is suitable for the surface treatment of reinforcing thermoplastic chopped glass fiber products, while a film-forming agent with lower molecular weight is suitable for the production of yarns used in winding and pulling molding. Epoxy resin polymers contain aliphatic hydroxyl, ether, and epoxy groups, and there is strong chemical attraction between polar groups in epoxy film-forming agents, so they have good adhesion and bundling effect on glass fibers;
In addition, the epoxy group in the epoxy film-forming agent can react with the terminal hydroxyl group, terminal carboxyl group, terminal amino group, and other active groups in engineering plastics such as PBT, PET, PA, PC, etc., to improve the interfacial bonding strength between the glass fiber and the resin. Polyester film-forming agents contain many ester groups, unsaturated chemical bonds, and hydrophilic groups in the main chain, and their performance depends on the type of acid and alcohol used in the synthesis of polyester and the ratio. When the base resin is unsaturated polyester resin, the unsaturated double bonds in the polyester film-forming agent can polymerize and cross-link with the double bonds in the base resin to form a strong chemical bond or physical entanglement, which improves the interfacial bonding strength. Polyester film-forming agents usually have excellent wetting and penetration properties and are therefore used as wetting agents in pultrusion, winding, spraying, chevron, and other products. Polyurethane film-forming agent molecular chain contains repeating carbamate structure, the existence of these polar groups makes the polyurethane to glass fiber have a very good binding, the molecular soft and hard segments of the combination of high elasticity and abrasion resistance, at the same time, polyurethane in the isocyanate group can be infiltrated with the amino coupling agent and the matrix resin in the chemical reaction, to promote the interfacial bonding, improve the performance of composite materials products.
Post time: Feb-17-2025
