Polymethyl methacrylate (PMMA) has good comprehensive mechanical properties. It ranks in the forefront of general plastics. Its tensile strength, bending strength and compression strength are higher than polyolefin, polystyrene, PVC, etc., and its impact toughness is poor, but it is also slightly better than polystyrene. The mechanical properties of cast bulk polymethylmethacrylate (such as PMMA for aviation) are higher than those of other engineering plastics, such as polyamide and polycarbonate.
Generally speaking, the tensile strength of PMMA can reach 50-77mpa, and the bending strength can reach 90-130mpa. The upper limit of these performance data has reached or even exceeded some engineering plastics. Its elongation at break is only 2% - 3%, so its mechanical properties are basically hard and brittle plastic with notch sensitivity. It is easy to crack under stress, but the fracture is not as sharp and uneven as polystyrene and ordinary inorganic glass. 40 ℃ is a second-order transition temperature, which is equivalent to the temperature at which side methyl begins to move. When the temperature is over 40 ℃, the toughness and ductility of the material are improved. The surface hardness of PMMA is low and easy to scratch.
The strength of PMMA is related to the time of stress action. With the increase of action time, the strength decreases. The mechanical properties and notch sensitivity of PMMA (oriented PMMA) after drawing were improved.
The heat resistance of polymethyl methacrylate is not high. Although its glass transition temperature reaches 104 ℃, the highest continuous use temperature varies from 65 ℃ - 95 ℃ with different working conditions. The temperature of thermal deformation is about 96 ℃ (1.18mpa), and Vicat softening point is about 113 ℃. The heat resistance can be improved by copolymerization of monomers with propylene methacrylate or glycol diester acrylate. The cold resistance of PMMA is also poor, and the embrittlement temperature is about 9.2 ℃. The thermal stability of polymethyl methacrylate is moderate, superior to PVC and POM, but inferior to polyolefin and polystyrene. The thermal decomposition temperature is slightly higher than 270 ℃, and its flow temperature is about 160 ℃, so there is a wide range of melting processing temperature.
The thermal conductivity and specific heat capacity of polymethyl methacrylate are in the middle level, which are 0.19w/m.k and 1464j / kg. K, respectively
