Attributes Electrical performance Polymethyl methacryla […]
Polymethyl methacrylate has less electrical properties than non-polar plastics such as polyolefins and polystyrene due to the polar methyl ester group at the side of the main chain. 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 noting that polymethyl methacrylate and even the entire acrylic plastic have excellent arc resistance. Under the action of arc, the surface does not produce carbonized conductive paths and arc track phenomena. 20 ° C is a secondary transition temperature, corresponding to the temperature at which the side methyl ester group begins to move. Below 20 ° C, the side methyl ester group is in a frozen state, and the electrical properties of the material are increased above 20 ° C.
Polymethyl methacrylate is resistant to relatively dilute inorganic acids, but concentrated inorganic acids can erode it and can be resistant to alkalis, but warm sodium hydroxide and potassium hydroxide can etch it and can withstand salt. And oils, fat-resistant hydrocarbons, insoluble in water, methanol, glycerin, etc., but can absorb alcohol to swell, and produce stress cracking, not resistant to ketones, chlorinated hydrocarbons and aromatic hydrocarbons. Its solubility parameter is about 18.8 (J / CM3) 1/2, soluble in many chlorinated hydrocarbons and aromatic hydrocarbons, such as dichloroethane, trichloroethylene, chloroform, toluene, etc., vinyl acetate and acetone can also make it Dissolved.
Polymethyl methacrylate has good resistance to gases such as ozone and sulfur dioxide.
Polymethyl methacrylate has excellent weathering resistance. The sample has been subjected to natural aging test for 4 years. The weight change, tensile strength and light transmittance are slightly decreased, the color is slightly yellowish, and the anti-silver grain is decreased. Obviously, the impact strength is also slightly improved, and other physical properties are almost unchanged.
Polymethyl methacrylate is easily burned with a limiting oxygen index of only 17.3.