Core-shell Structure Modifier Aim Toughened Poly Methyl Methacrylate The Performance

Polymethyl methacrylate (PMMA) is rigid, amorphous polymers particularly noted for their exceptional clarity and UV resistance, and therefore wildly used for making household appliances, medical devices and automobile, etc. For their mechanical property show brittle and notch sensitivity, the research on toughening receives much concern, in which adopting core-shell modifiers toughening PMMA resins is one of the most important method.In this paper, core-shell modifiers were synthesized by emulsion polymerization, and the influence of modifiers structure, cross-linking density of rubber phase, the variance of interface property between modifiers and matrix on PMMA resins toughening were investigated. The main research works and conclusions are as follows:1. Two and three layers acrylic impact modifiers (AIM) were synthesized by emulsion polymerization, The optimization diameter of rubber particle which led to maxium impact strength, fracture energy and stress intensity factor (Kmax) of AIM/PMMA blends was 269nm, and crack propagating energy (Uprop) reached maxium when rubber particle diameter of AIM was 351nm. The blends with three layers AIM had higher Kmax at low strain rate than that of blends with two layers AIM, it indicated that the deformation of rubber phase of three layers AIM was benificial to hinder the generation of crack in the process of blends fracture. Morphology analysis of deformation zone of three layers AIM toughening PMMA blends showed that the AIM with BA-St copolymer interface rubber layer generated evident cavitation, and the AIM with PBA interface rubber layer arised matrix crazing. That can be attributing to the influence of rubber phase property on toughening mechanism.2. Four kinds of acrylic impact modifiers (AIMs) with different rubber cross-linking density were synthesized by emulsion polymerization, which diameter and refractive index can be controlled. The effect of different rubber cross-linking density on mechanical and optical properties of AIM/PMMA blends was investigated. It was shown that impact strength of AIM/PMMA blends increased at first and then decreased with cross-linking agent raise, the AIM/PMMA blends of maximum crack initiation energy (Kmax), crack propagation energy (Uprop) and impact strength got to maximum when moderate rubber cross-linking agent content of AIM,2wt%, was adopted. In comparison with pure PMMA, impact strength improved by five times, and the change of optical property was not remarkable. Combined the results of impact tests and SEM observation of deformation zone of AIM/PMMA blends, it was shown that the rubber particles cavitation of AIM is beneficial to improve energy-absorbing of matrix resin.3. Toughening blends which composition was PMMA, AIM with carboxylic acid group and methyl methacrylate-glycidyl methacrylate-methacrylate copolymer were prepared by melt blending. Maxium torque and equilibrium torque of blends in the process of melt blending increased with carboxylic acid group content in the shell of AIM increament, and impact strength and Kmax of blends enhanced accordingly, but the optical propertie of blends was not affected. It indicated that the reaction of carboxylic acid group of modifiers and epoxy group of matrix resin increased interfacial cohesion of two phases, which led to form more rubber particles cavitation and promoted massive yielding of maxtrix resins in the process of deformation.