As a kind of polymer composite particle with unique structure, shell-core polymer is generally prepared by step emulsion polymerization. The core is rubber to give the tensile properties of the product; the shell is a plastic with a higher glass transition temperature, the main function is to isolate the particles from each other, promote the dispersion in the matrix and increase the interaction with the matrix resin. The polymer has recently been continuously improved in epoxy resin modification.
The researchers used a two-step emulsion polymerization method to prepare nucleophiles of PBS/PMMA shell and synthesize PAMMA, P(MMA-AM), P(MMA-GMA) and P(MMA-DVB) by introducing different comonomers. ) Different shells were used to study the interface between the shell-core particles and the epoxy resin. It is believed that the nature of the interface depends on the physical state of the bond. The morphological structure of the shell-core particles dispersed in the epoxy resin matrix plays an important role in the toughening. The degree of dispersion varies depending on the comonomer in the PMMA shell. The microscopic interface between the microparticles and the matrix does not directly affect the toughness but is used to control the morphology of the blends that have a significant effect on toughness.
Chinese researchers prepared shell-core structure particles PBA/PS, PBA/PMMA and P(MMA-AA) with different shells. According to epoxy-e experts, due to the poor compatibility of PS with the matrix epoxy resin, the interface bonding performance is weak, and the toughening effect of the rubber particles with the shell on the epoxy resin is not obvious; the PMMA shell is soluble In the epoxy resin, it is integrated with the epoxy resin to increase the toughening effect; the P(MMA-AA) shell containing the active group -COOH reacts with the epoxy group. So the shear strength and peel strength are the highest.
External progress in this area is also greater. Ceisler B et al. studied the mixed modified epoxy resin of PBA/PMMA and hardness alumina particles, and the fracture energy of the curing system was much higher than that of shell-core particles or hard alumina particles alone, compared with pure epoxy resin. The system is increased by about 15 times, which is the result of the increase in plastic deformation of hard crack particles in the local area of ​​the crack tip.