Acrylic is also called plexiglass. This material has many special characteristics and is widely used because of these characteristics!
1. Mechanical properties
Plexiglass has good comprehensive mechanical properties and ranks in the forefront of general-purpose plastics. Its tensile, bending, and compressive strengths are all higher than polyolefins, and higher than polystyrene, polyvinyl chloride, etc., and its impact toughness is poor, but slightly better than PS. The cast bulk polymerized polymethyl methacrylate sheet (such as aerospace plexiglass sheet) has higher tensile, bending, and compression mechanical properties, and can reach the level of engineering plastics such as polyamide and polycarbonate.
Generally speaking, the tensile strength of PMMA can reach the level of 50-77MPa, and the bending strength can reach the level of 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 have notch sensitivity, easy to crack under stress, but the fracture is not as sharp as PS and ordinary inorganic glass Jagged. 40°C is a secondary transition temperature, which is equivalent to the temperature at which the pendant methyl group starts to move. If it exceeds 40°C, the toughness and ductility of the material will be improved.
2. Heat resistance
The heat resistance of acrylic material is not high. Although its glass transition temperature reaches 104°C, the continuous use temperature varies between 65°C and 95°C depending on the working conditions. The heat distortion temperature is about 96°C (1.18MPa) . The heat resistance can be improved by copolymerization of monomers with propylene methacrylate or ethylene glycol diester acrylate. The cold resistance is also poor, and the embrittlement temperature is about 9.2°C. The thermal stability of polymethyl methacrylate is moderate, better than polyvinyl chloride and polyformaldehyde, but not as good as polyolefin and polystyrene. The thermal decomposition temperature is slightly higher than 270℃, and its flow temperature is about 160℃. There is a wide range of melt processing temperature.
3. Chemical and solvent resistance
Polymethyl methacrylate can withstand relatively dilute inorganic acids, but concentrated inorganic acids can make it corrode and alkali-resistant, but warm sodium hydroxide and potassium hydroxide can make it corrode and salt-resistant And grease, resistant to aliphatic hydrocarbons, insoluble in water, methanol, glycerin, etc., but can absorb alcohol and swell and cause stress cracking. It is not resistant to ketones, chlorinated hydrocarbons and aromatic hydrocarbons. Its solubility parameter is about 18.8 (J/CM3) 1/2, and it can be dissolved in many chlorinated hydrocarbons and aromatic hydrocarbons, such as dichloroethane, trichloroethylene, chloroform, toluene, etc., vinyl acetate and acetone can also make it Dissolve.
4. Flame resistance and weather resistance
Polymethyl methacrylate is easy to burn, and its limited oxygen index is only 17.3.
Polymethyl methacrylate has excellent atmospheric aging resistance. After 4 years of natural aging test, the sample has a slight decrease in tensile strength and light transmittance, a slight yellowing in color, and a decrease in crazing resistance. Obviously, the impact strength has been slightly improved, and other physical properties have hardly changed.