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Mechanical properties of acrylic(PMMA)

2023-11-18

Polymethyl methacrylate has good comprehensive mechanical properties and ranks among the top in general plastics. Its tensile, bending, and compression strengths are higher than those of polyolefins, as well as polystyrene and polyvinyl chloride. Its impact toughness is poor, but it is also slightly better than polystyrene. The poured bulk polymerized polymethyl methacrylate sheet (such as aviation organic glass sheet) has higher mechanical properties such as tensile, bending, and compression, which can reach the level of engineering plastics such as polyamide and polycarbonate.



Acrylic

Generally speaking, the tensile strength of polymethyl methacrylate can reach the level of 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 plastics, and it has notch sensitivity and is prone to cracking under stress. However, the fracture surface is not as sharp and uneven as polystyrene and ordinary inorganic glass when broken. 40 ℃ is a secondary transition temperature, equivalent to the temperature at which the lateral methyl group begins to move. Beyond 40 ℃, the toughness and ductility of the material are improved. Polymethyl methacrylate has low surface hardness and is prone to scratching.


The strength of polymethyl methacrylate is related to the stress action time, and as the action time increases, the strength decreases. After stretching, the mechanical properties of polymethyl methacrylate (oriented organic glass) were significantly improved, and the notch sensitivity was also improved.


The heat resistance of polymethyl methacrylate is not high. Although its glass transition temperature reaches 104 ℃, its maximum continuous use temperature varies between 65 ℃ and 95 ℃ depending on the working conditions. The thermal deformation temperature is about 96 ℃ (1.18 MPa), and the Vicat softening point is about 113 ℃. The heat resistance can be improved by copolymerization of monomers with propylene methacrylate or ethylene glycol diester acrylate. Polymethyl methacrylate also has poor cold resistance, with a embrittlement temperature of about 9.2 ℃. The thermal stability of polymethyl methacrylate is moderate, superior to polyvinyl chloride and paraformaldehyde, but not as good as polyolefin and polystyrene. The thermal decomposition temperature is slightly higher than 270 ℃, and its flow temperature is about 160 ℃. Therefore, there is still a wide range of melting processing temperatures.


The thermal conductivity and specific heat capacity of polymethyl methacrylate (PMMA) in plastics belong to the middle level, which are 0.19W/M.K and 1464J/Kg. K respectively