Acrylic glass has good comprehensive mechanical properties. It is at the forefront of general-purpose plastics. Its tensile, bending, and compression strengths are higher than polyolefins, and also higher than polystyrene and polyvinyl chloride.
The impact toughness is poor, but it is also slightly better. For polystyrene. The cast bulk polymerized polymethyl methacrylate sheet (such as plexiglass sheet for aviation) has higher mechanical properties such as stretching, bending and compression, and can reach the level of engineering plastics such as polyamide and polycarbonate. Generally speaking, the tensile strength of polymethyl methacrylate can reach 50-77Mpa level, and the bending strength can reach 90-130Mpa. The upper limit of these performance data has reached or even exceeded some engineering plastics. The elongation at break is only 2%-3%, so the mechanical properties are basically hard and brittle plastics, and have notch sensitivity, easy to crack under stress, but the fracture is not like polystyrene and ordinary glass when breaking Sharp and jagged. 40 ℃ is a second-order transition temperature, which is equivalent to the temperature at which the methyl side begins to move. Above 40 ℃, the toughness and ductility of the material have improved. Polymethyl methacrylate has low surface hardness and is easily scratched.
The heat resistance of polymethyl methacrylate is not high. Although its glass transition temperature reaches 104 ℃, the maximum continuous use temperature varies between 65 ℃-95 ℃ according to the conditions of the workpiece. The heat deformation temperature is about 96 ℃ (1.18MPa), Vicat softening point is about 113 ℃. The heat resistance can be improved by copolymerizing the monomer with methyl methacrylate or ethylene glycol acrylate. Polymethyl methacrylate has poor cold resistance knife, and the embrittlement temperature is about 9.2℃.
The thermal stability of polymethyl methacrylate is moderate, better than polyvinyl chloride and polyoxymethylene, but not as good as polyolefin and polystyrene. Its thermal decomposition temperature is slightly higher than 270℃, and its flow temperature is about 160℃. There is a wide range of melt processing temperature. The thermal conductivity and specific heat capacity of polymethyl methacrylate belong to the middle level in plastics, respectively 0.19W/CM.K and 1464J/Kg.K.