PMMA (Acrylic) CNC Machining

Acrylic, also known as PMMA or Plexiglas, is from the English acrylic (acrylic plastic), and is the chemical name of polymethyl methacrylate.

Is an important early development of plastic polymer materials, with good transparency, chemical stability, and weather resistance, easy to dye, easy to process, and beautiful appearance, in the construction industry and has a wide range of applications. Plexiglass products can usually be divided into cast sheets, extruded sheets, and molded plastics.

Mechanical Properties

Polymethyl methacrylate has good overall mechanical properties and is at the forefront of general-purpose plastics. Its tensile, bending, and compression strengths are higher than those of polyolefins and higher than those of polystyrene and polyvinyl chloride, etc. Its impact toughness is poor, but it is also slightly better than that of polystyrene. The mechanical properties of tensile, bending, and compression are higher for cast polymerized polymethyl methacrylate sheets (such as plexiglass sheets for aviation), which can reach the level of polyamide, polycarbonate, and other engineering plastics.

Generally speaking, the tensile strength of polymethyl methacrylate can reach the level of 50-77MPa and the bending strength can reach 90-130MPa, and the upper limit of these performance data has reached or even exceeded some engineering plastics. Its elongation at break is only 2%-3%, so the mechanical properties are basically hard and brittle plastic and have a gap sensitivity, easy to crack under stress, but the fracture is not as sharp and uneven as polystyrene and ordinary inorganic glass. 40 ℃ is a secondary transition temperature, which is equivalent to the temperature at which the side methyl starts to move, and over 40 ℃, the toughness of the material, and ductility improved. Polymethyl methacrylate has low surface hardness and is easily scuffed.

The strength of polymethyl methacrylate is related to the time of stress action and decreases with the increase of action time. The mechanical properties of polymethyl methacrylate (oriented plexiglass) after tensile orientation are significantly improved and notch sensitivity is also improved.

The heat resistance of polymethyl methacrylate is not high. Although its glass transition temperature reaches 104°C, the maximum continuous use temperature changes between 65°C and 95°C with different working conditions, the heat deflection temperature is about 96°C (1.18 MPa), and the Vicat softening point is about 113°C. Heat resistance can be improved by copolymerization of monomer with acrylate methacrylate or glycol bis-ester acrylate. The cold resistance of polymethyl methacrylate is also poor, with a brittleness temperature of about 9.2°C. The thermal stability of polymethyl methacrylate is medium, better than polyvinyl chloride and polyformaldehyde, but less than polyolefin and polystyrene, thermal decomposition temperature is slightly higher than 270 ℃, its flow temperature is about 160 ℃, so there is still a wide range of melt processing temperature.

The thermal conductivity and specific heat capacity of polymethyl methacrylate are medium in plastics, 0.19W/M.K and 1464J/Kg.K respectively.