Acrylic material's usage in CNC parts
Basic Introduction
Acrylic material's usage in CNC parts, also known as PMMA or organic glass, is derived from the English word acrylic (acrylic plastic), and its chemical name is polymethyl methacrylate.
It is an important plastic polymer material that was developed earlier. It has good transparency, chemical stability and weather resistance, is easy to dye, easy to process, and has a beautiful appearance. It is widely used in the construction industry. Organic glass products can usually be divided into cast plates, extruded plates and molded materials.
Mechanical properties
Properties
Polymethyl methacrylate has good comprehensive mechanical properties and ranks among the top general plastics. Its tensile, bending, and compression strengths are higher than those of polyolefins, polystyrene, polyvinyl chloride, etc. Its impact toughness is poor, but it is also slightly better than polystyrene. The mechanical properties of cast bulk polymerized polymethyl methacrylate sheets (such as plexiglass sheets for aviation) such as tensile, bending, and compression are higher, 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, 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 the mechanical properties are basically hard and brittle plastics, and it is notch sensitive and easy to crack under stress, but the fracture is not as sharp and uneven as polystyrene and ordinary inorganic glass when it breaks. 40℃ is a secondary transition temperature, which is equivalent to the temperature at which the side methyl group starts to move. When it exceeds 40℃, the toughness and ductility of the material are improved. The surface hardness of polymethyl methacrylate is low and it is easy to scratch.
The strength of polymethyl methacrylate is related to the stress action time. As the action time increases, the strength decreases. The mechanical properties of polymethyl methacrylate (oriented organic glass) after stretching orientation are significantly improved, and the notch sensitivity is also improved
Feature
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℃ depending on the working conditions. The heat deformation temperature is about 96℃ (1.18MPa), and the Vicat softening point is about 113℃. The heat resistance can be improved by copolymerizing the monomer with methacrylate or diester-based ethylene glycol acrylate. The cold resistance of polymethyl methacrylate is also poor, and the brittle temperature is about 9.2℃. The thermal stability of polymethyl methacrylate is medium, better than polyvinyl chloride and polyoxymethylene, but not as good as polyolefins and polystyrene. The thermal decomposition temperature is slightly higher than 270℃, and its flow temperature is about 160℃, so it still has a wide melt processing temperature range.
The thermal conductivity and specific heat capacity of polymethyl methacrylate are both at a medium level among plastics, which are 0.19W/M.K and 1464J/Kg.K respectively.
