What are the properties of acrylic material?
Mechanical properties
Polymethyl methacrylate has good comprehensive mechanical properties and ranks in the forefront of general-purpose plastics. Its tensile, bending, and compressive strengths are higher than those of polyolefins, and also higher than those of polystyrene and polyvinyl chloride. The impact toughness is poor. But also slightly better than polystyrene. The cast bulk polymerized polymethyl methacrylate sheet (such as plexiglass sheet for aviation) has higher mechanical properties such as tensile, bending and compression, 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 its mechanical properties are basically hard and brittle plastics, and it has notch sensitivity and is easy to crack under stress, but the fracture is not like polystyrene and ordinary inorganic glass. So sharp and uneven. 40°C is a secondary transition temperature, which is equivalent to the temperature at which the side methyl group starts to move. Above 40°C, the toughness and ductility of the material are improved. Polymethyl methacrylate has low surface hardness and is easy to scratch.
The strength of polymethyl methacrylate is related to the stress action time, and the strength decreases with the increase of action time. The mechanical properties of the stretch-oriented polymethyl methacrylate (oriented plexiglass) are significantly improved, and the 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 varies between 65 °C and 95 °C with different working conditions, and the heat distortion temperature is about 96 °C. ℃ (1.18MPa), Vicat softening point is about 113℃. The heat resistance can be improved by copolymerizing the monomer with propylene methacrylate or ethylene glycol diester acrylate. The cold resistance of polymethyl methacrylate is also poor, and the embrittlement temperature is about 9.2 °C. The thermal stability of polymethyl methacrylate is medium, which is better than that of polyvinyl chloride and polyoxymethylene, but not as good as polyolefin and polystyrene. The thermal decomposition temperature is slightly higher than 270 °C, and its flow temperature is about 160 °C, so Has a wide melt processing temperature range.
The thermal conductivity and specific heat capacity of polymethyl methacrylate belong to the medium level in plastics, which are 0.19W/M.K and 1464J/Kg.K respectively
Electrical properties
Due to the polar methyl ester group contained in the side position of the main chain, the electrical properties of polymethyl methacrylate are inferior to those of non-polar plastics such as polyolefin and polystyrene. The polarity of the methyl ester group is not too large, and the polymethyl methacrylate still has good dielectric and electrical insulating properties. It is worth pointing out that polymethyl methacrylate and even the entire acrylic plastic have excellent arc resistance. Under the action of the arc, the surface will not produce carbonized conductive paths and arc tracks. 20°C is a second-order transition temperature, which corresponds to the temperature at which the side carboxyl group starts to move. Below 20°C, the side carboxyl group is in a frozen state, and the electrical properties of the material will be improved when it is above 20°C.
Solvent resistance
Polymethyl methacrylate can be resistant to relatively dilute inorganic acids, but concentrated inorganic acids can make it eroded and alkali resistant, but warm sodium hydroxide and potassium hydroxide can make it eroded and salt resistant And oil, resistant to aliphatic hydrocarbons, insoluble in water, methanol, glycerin, etc., but can absorb alcohol swelling, and produce stress cracking, not resistant to ketones, chlorinated hydrocarbons and aromatic hydrocarbons. Its solubility parameter is about 18.8(J/CM3)1/2, it is soluble in many chlorinated hydrocarbons and aromatic hydrocarbons, such as dichloroethane, trichloroethylene, chloroform, toluene, etc., vinyl acetate and acetone can also make it dissolve.
Polymethyl methacrylate has good resistance to gases such as ozone and sulfur dioxide.
Weather resistance
Polymethyl methacrylate has excellent resistance to atmospheric aging. After 4 years of natural aging test, the weight of the samples changed slightly, the tensile strength and light transmittance decreased slightly, the color was slightly yellowed, and the silver streak resistance decreased. Obviously, the impact strength is slightly improved, and other physical properties are almost unchanged.
flammability
Polymethyl methacrylate is easy to burn with a limiting oxygen index of only 17.3.
Polymethyl methacrylate has good comprehensive mechanical properties and ranks in the forefront of general-purpose plastics. Its tensile, bending, and compressive strengths are higher than those of polyolefins, and also higher than those of polystyrene and polyvinyl chloride. The impact toughness is poor. But also slightly better than polystyrene. The cast bulk polymerized polymethyl methacrylate sheet (such as plexiglass sheet for aviation) has higher mechanical properties such as tensile, bending and compression, 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 its mechanical properties are basically hard and brittle plastics, and it has notch sensitivity and is easy to crack under stress, but the fracture is not like polystyrene and ordinary inorganic glass. So sharp and uneven. 40°C is a secondary transition temperature, which is equivalent to the temperature at which the side methyl group starts to move. Above 40°C, the toughness and ductility of the material are improved. Polymethyl methacrylate has low surface hardness and is easy to scratch.
The strength of polymethyl methacrylate is related to the stress action time, and the strength decreases with the increase of action time. The mechanical properties of the stretch-oriented polymethyl methacrylate (oriented plexiglass) are significantly improved, and the 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 varies between 65 °C and 95 °C with different working conditions, and the heat distortion temperature is about 96 °C. ℃ (1.18MPa), Vicat softening point is about 113℃. The heat resistance can be improved by copolymerizing the monomer with propylene methacrylate or ethylene glycol diester acrylate. The cold resistance of polymethyl methacrylate is also poor, and the embrittlement temperature is about 9.2 °C. The thermal stability of polymethyl methacrylate is medium, which is better than that of polyvinyl chloride and polyoxymethylene, but not as good as polyolefin and polystyrene. The thermal decomposition temperature is slightly higher than 270 °C, and its flow temperature is about 160 °C, so Has a wide melt processing temperature range.
The thermal conductivity and specific heat capacity of polymethyl methacrylate belong to the medium level in plastics, which are 0.19W/M.K and 1464J/Kg.K respectively
Electrical properties
Due to the polar methyl ester group contained in the side position of the main chain, the electrical properties of polymethyl methacrylate are inferior to those of non-polar plastics such as polyolefin and polystyrene. The polarity of the methyl ester group is not too large, and the polymethyl methacrylate still has good dielectric and electrical insulating properties. It is worth pointing out that polymethyl methacrylate and even the entire acrylic plastic have excellent arc resistance. Under the action of the arc, the surface will not produce carbonized conductive paths and arc tracks. 20°C is a second-order transition temperature, which corresponds to the temperature at which the side carboxyl group starts to move. Below 20°C, the side carboxyl group is in a frozen state, and the electrical properties of the material will be improved when it is above 20°C.
Solvent resistance
Polymethyl methacrylate can be resistant to relatively dilute inorganic acids, but concentrated inorganic acids can make it eroded and alkali resistant, but warm sodium hydroxide and potassium hydroxide can make it eroded and salt resistant And oil, resistant to aliphatic hydrocarbons, insoluble in water, methanol, glycerin, etc., but can absorb alcohol swelling, and produce stress cracking, not resistant to ketones, chlorinated hydrocarbons and aromatic hydrocarbons. Its solubility parameter is about 18.8(J/CM3)1/2, it is soluble in many chlorinated hydrocarbons and aromatic hydrocarbons, such as dichloroethane, trichloroethylene, chloroform, toluene, etc., vinyl acetate and acetone can also make it dissolve.
Polymethyl methacrylate has good resistance to gases such as ozone and sulfur dioxide.
Weather resistance
Polymethyl methacrylate has excellent resistance to atmospheric aging. After 4 years of natural aging test, the weight of the samples changed slightly, the tensile strength and light transmittance decreased slightly, the color was slightly yellowed, and the silver streak resistance decreased. Obviously, the impact strength is slightly improved, and other physical properties are almost unchanged.
flammability
Polymethyl methacrylate is easy to burn with a limiting oxygen index of only 17.3.