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May 9, 2023
Due to the significant difference in solubility parameters between organic silicon and epoxy resin, the compatibility between organic silicon and epoxy resin is poor based on the principle of similar solubility parameters. If the two are simply mixed together during modification, the modification effect is not good enough due to the high interfacial tension between the two phases and the multiphase separation structure. In order to improve compatibility, it is necessary to modify organic siloxanes, or use organic silicon coupling agents, compatibilizers, and the third component of transition phase functions to improve the compatibility and interface state of organic silicon and epoxy resin. These are effective methods to improve the performance of polymer alloys. Therefore, the following methods are used to improve the compatibility of the two.
Blending modification is the blending of organic silicon and epoxy resin to form a system with excellent comprehensive performance and low cost. The compatibility of each component in the blend system is an important factor affecting the morphology, structure, and properties of the blend.
Introduction of compatibilization group into the molecular structure of organosilicon
The polymer obtained through mechanical blending has poor interaction force between the two phases and is prone to significant microphase separation, forming a larger "island" structure. The two polymers are very incompatible at the segment or molecular level, which leads to poor compatibility with epoxy resin. Generally, organic silicone resins with active groups are used for modification. For example, polydimethylsiloxane has excellent flexibility and unique low surface energy characteristics, making it an ideal material for modifying epoxy resin. However, the two cannot be miscible. By introducing functional groups that can react with epoxy resin groups on the polydimethylsiloxane molecular chain, such as light groups The compatibility can be improved by groups such as amino and amino groups. Introducing slightly stronger polar groups such as cheese chains into organic silicon molecules increases the polarity of organic silicon molecules, causing strong physical interactions between polymer molecules and increasing their compatibility with epoxy resins. Huang et al. blended a triblock copolymer of poly (acyl polydimethylsiloxane) with epoxy resin and found that the longer the siloxane chain segment, the lower the static friction coefficient of the modified epoxy resin coating, indicating an improvement in the hydrophobicity of the coating.
By free radical polymerization of polysiloxane pre polymers with alkene terminated groups with styrene or methyl methacrylate, elastomers containing polysiloxane branched chains were obtained, and their modification of epoxy resin achieved good results. In addition to the modification of organosilicon oxide, it can also be improved by adding a transition phase. For example, the introduction of specific interactive compatibilizing groups in the molecular structure of organosilicon can cause strong physical interactions between different polymer molecules, such as hydrogen bonds, dipole dipole, elemental hydrogen bonds, ion ion, ion dipole, etc. The currently reported compatibilizing groups that introduce organosilicon include benzene with slightly stronger polarity Groups, polyacyl chains, etc., enhance the polarity of organic silicon molecules and enhance their compatibility with epoxy resins.
A heat-resistant epoxy resin composite material was prepared by combining a polysiloxane containing aromatic groups with epoxy resin. Due to the polarity of the aromatic group, the difference in solubility parameters between organic silicon and epoxy resin is reduced, and the compatibility is improved.
A technical personnel prepared a poly acyl grafted polysiloxane fired copolymer through hydrosilylation reaction, which has good compatibility with epoxy resin but does not react with epoxy resin. And blend it with epoxy resin to modify the epoxy resin. The structure of the grafted cheese chain segment in the copolymer, the content of the cheese, and the addition of the epoxy resin copolymer are the most important factors affecting the microstructure and surface properties of the modified epoxy resin. As the mole fraction of propylene oxide in the polyacrylic chain increases, the compatibility between the copolymer and epoxy resin deteriorates, and the size of the polysiloxane calcined micro zone increases. When the mass fraction of polyimide in the copolymer increases to about 75%, the average particle size of the dispersed phase decreases to below 1.5 µ m.
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