Modification Method with Vinyl Coupling Agent

Vinyl undergoes free radical polymerization under the action of an initiator, grafting siloxane onto the polyurethane chain for modification. A new type of organic silicone polyol with high cohesion was synthesized through solution polymerization using acrylic epoxy resin (AE) and vinyl trimethoxysilane (VTMS) as monomers. Ammonia based organic silane was reacted with polyurethane prepolymer to study the heat resistance of the modified polyurethane. The results showed that:, The heat resistance of materials modified by adding organic silicon to both soft and hard segments is significantly improved compared to materials that only introduce organic silicon in the soft segment;

The effect of the ratio of acrylic epoxy resin monomer and vinyl trimethoxysilane monomer on the copolymerization reaction was studied, and it was found that the conversion rate of the reaction significantly increased with the increase of monomer ratio; The increase in temperature and initiator leads to an increase in the number of free radicals and an increase in the speed of copolymerization reaction; With the increase of self-made silicon content, the mass loss rate of synthesized polyurethane decreases.

Introducing organic siloxanes to modify acrylic polyurethane hybrid aqueous dispersions and improving the heat resistance, solvent resistance, and hardness of the hybrid aqueous dispersions film can provide a broader application prospect for the modified hybrid aqueous dispersions. The polyurethane acrylic acid lotion is modified by silane coupling agent, which uses the Y organic functional groups (such as tibial, amino, epoxy, vinyl, etc.) on the organosiloxane to react with the isoparm ester group in the polyurethane, or to mix and copolymerize with the acrylic acid monomer, and introduce the organosiloxane into the polyurethane acrylic acid copolymerization lotion.

The surface tension of acrylic polyurethane copolymers containing siloxane groups is lower than that of acrylic polyurethane copolymers without siloxane groups. In order to achieve the lowest surface energy of the system, the components with low surface energy will gradually migrate to the outside of the components with high surface energy, thus forming siloxane segments that are enriched on the surface of the lotion film. The active siloxane groups enriched on the surface of the lotion are hydrolyzed to form silanol under certain conditions. The silanol and the active groups inside or on the surface of the polymer condense to form a three-dimensional network (Si-0-Si) cross-linking structure, which leads to the increase of chemical cross-linking points and cross-linking density in the lotion, which has a strengthening effect on the density of the surface layer of the film, and ultimately improves the heat resistance and mechanical properties of the film, and improves the water resistance and solvent resistance of the polymer film.

Vinyl siloxane modified waterborne polyurethane is a hybrid of acrylic polyurethane dispersions that uses siloxane monomers with vinyl groups and acrylic monomers to copolymerize, introducing organic siloxanes into the acrylic polyurethane dispersions, thereby improving the water resistance and mechanical properties of the waterborne polyurethane dispersions.

The preparation process can be divided into seed lotion polymerization, in-situ lotion polymerization and solution polymerization phase inversion. In the seed lotion polymerization method, PU dispersion seeds are usually obtained first, then acrylic monomer, vinyl siloxane and initiator are added, and a small amount of emulsifier is added if necessary, and then free radical lotion polymerization is used to prepare organosilicon modified PUA dispersion products.

In situ lotion polymerization, acrylic monomer and vinyl siloxane partially or completely replace the organic solvent in the seed lotion polymerization. The hydrophilic PU prepolymer/vinyl monomer mixture is prepared by solution polymerization, and then the mixture is dispersed in water, and then the free radical lotion polymerization of vinyl monomer is carried out to prepare the silicone modified PUA dispersion.

The solution polymerization phase inversion method is to first polymerize in an organic solvent to prepare PU prepolymers, and then add acrylic monomers, vinyl siloxanes, and initiators for free radical solution polymerization of the monomers to prepare a water dispersible modified PUA composite resin. After water dispersion and solvent removal treatment, the organic silicon modified PUA dispersion is prepared.

At present, there are not many studies using the method of modifying waterborne polyurethane with vinyl siloxane. The main difficulty is that the stability of waterborne polyurethane is affected by the hydrolysis of siloxane after it is dispersed in water.

Our main products are Silicone Resin for Mica Insulation Materials，Silicone Resin for Motor，Silicone Resin for transformer coils，Silicone Resin for H-class motors，Silicone Resin for motor coil wrapping，Silicone Resin Elastomer Suspension.