Preparation of Modified Epoxy Resin
May 19, 2023
Experimental results have shown that the toughening modification of epoxy resin by polydimethylsiloxane has good results at low percentage content. With the increase of molecular weight and percentage content of epoxy resin, the mechanical properties of its copolymer have been improved within a certain molecular weight range.
One of the key technologies for developing epoxy sealing materials for megabit level VLSI is the preparation of low stress modified epoxy resin. The main idea of modifying low stress epoxy resin is to mix elastic rubber into the epoxy resin to reduce its modulus and linear expansion coefficient, achieving the goal of reducing internal stress. Because most elastomers are incompatible with epoxy resin, the "compatibility" is improved by some chemical bond between rubber and epoxy matrix, and the macro size of the rubber dispersed phase is controlled, Relying on evenly dispersed "islands Elastomers play a role in toughening and reducing internal stress. Li Shanjun et al. synthesized a modified ortho cresol epoxy resin with uniformly dispersed tibia based silicone oil through dispersion polymerization using a multifunctional group coupling agent. The silane coupling agent KH-550 hydrolyzed to silanol groups, and then condensed with tibia based silicone oil to form polysiloxane particles with amine terminal groups on the surface. These particles can be stably dispersed in organic solvents. The KH-550 branched chain on the surface of organic silicon particles acts as a stabilizer Therefore, this type of particle can be stably dispersed in organic solvents. Disperse organic silicon particles in epoxy by vigorously stirring to evenly disperse the particles, and fix the dispersed phase particles in the matrix through the reaction between the NH2- or - NH - group on its surface and the epoxy group, obtaining a stable phase structure.
The synthesis process consists of three steps: hydrolysis, condensation, and dispersion.
(1) Hydrolysis: Add 20g of tibial methyl silicone oil PDMS, 15g of pure water, 3g of KH-550, lg of ammonia water, and 15g of 4-methylpentone 2 'solution in a three necked bottle with a mechanical stirrer. The pH value is 8, and the mixture is vigorously stirred at 40 ° C for 8 hours to obtain a clear two-phase system.
(2) Condensation: Add the remaining 15g of 4-methylpentane-2, raise the temperature to 90 ° C and reflux for 3h, then azeotrope and evaporate at 120 ° C for 5h. Remove water from the reaction system using a moisture separator to obtain a viscous, clear, homogeneous solution.
(3) Dispersion: Add 100g of o-cresol epoxy resin, raise the temperature to 125-130 ° C, stir vigorously after the resin is completely melted, reflux reaction for 8 hours, cool to 120 ° C, reduce pressure to remove all solvents, and obtain modified resin.
Observing the cross-sectional morphology using scanning electron microscopy, the silicone oil particles were uniformly dispersed in the epoxy matrix. The particle size decreases with the increase of KH-550 dosage. It shows that the molecular weight of the product condensed with PDMS will decrease with the increase of KH-550 stamp, and because there are more amino groups, it provides more chemical bond, overcomes the adverse factor of surface energy rise caused by the decrease of dispersed phase particle size, and is conducive to the stability of silicone oil particles in epoxy. Experiments have shown that the organosilicon modified o-cresol epoxy resin prepared by dispersion polymerization has a significant effect on reducing the internal stress of epoxy molding materials.
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