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The performance of PMMA

by:CSSSLD     2021-01-23
PMMA surface resistivity is higher than most other plastics, and within a certain range is not affected by climate and temperature, good arc resistance, have reduced arc ability. PMMA forming methods mainly include the slurry casting molding and plastic melt extrusion, injection molding. PMMA molecular structure of the existence of ester base make it easy to moisture absorption, and therefore must be dry before the material in the processing of plastic injection molding, the moisture content down to zero. Less than 02%.

the heat capacity of the PMMA is lower than most thermoplastics, it rapidly heated plasticizing, its thermal conductivity is 0. 14 - 0. 2 w, is a poor conductor of heat, should be paid attention to in the profile of the secondary processing to prevent local overheat and cause material damage, he is about 10 times higher than the general metal linear expansion coefficient, and along with the change of temperature change, from - 50 - 50℃。 PMMA, weak base, and some dilute acid resistant to water soluble salt.

although PMMA macromolecular chain and PE are similar, but the performance is much worse than PE, the main reason is that PMMA molecular chain ester base with polarity. Those side at temperature below Ta has not been frozen, dipole polarization in the appropriate frequency range, and therefore have higher dielectric constant value. With the increase of frequency, side base of dipole polarization is not completed in the effective time, to keep pace with the change of the external electric field, dielectric constant value instead of decrease obviously.

no, strong acid and strong alkali resistance to oxidation such as hydrocyanic acid and aqua regia, concentrated sulfuric acid, etc all can make its erosion. At the same time, the concentration of the medium and temperature also has a great influence on the stability of the chemical, in general, the increase of concentration, temperature, stability. For 50% of phosphoric acid, 25% sulfuric acid, acetic acid, 50% at 20 ℃, PMMA has the very good stability, but at 60 ℃ is unstable, and for 25% 20% of phosphoric acid, sulfuric acid and 10% acetic acid at 60 ℃ temperature is stable. For 30% of ammonia in 20 ℃ PMMA is stable, but even though 10% of ammonia in 60 ℃ erosion.

in organic compounds, PMMA of long chain alkane, simple ethers, grease is relatively stable, not resistant to short chain alkanes, alcohols, ketones, etc. Soluble in aromatic hydrocarbons, chlorinated hydrocarbons, such as organic solution, such as carbon tetrachloride, ethylene dichloride, tetrachloroethane, formic acid, acetone, etc. Contact with these causes PMMA materials or products to produce silver lines, and even cracking. Compared with other resin, PMMA has excellent weather resistance.

PMMA flammable materials, the light from the fire can't self-extinguishing, after the flame is shallow blue, the bottom is white. Bubbles when burning, the molten drop, decomposition of methyl methacrylate monomers such as, accompanied by the smell of rotting fruit and vegetables. Tg of PMMA is 105 ℃, vicat softening point 100 - 102 ℃, the brittle temperature Below 60 ℃. PMMA - 60 - 65 ℃ within the scope of use for a long time, short time using temperature should not exceed 105 ℃.

in outdoor conditions after 4 years of aging test, its tensile strength and light transmittance is only a slight decline, quality basic remain unchanged, exterior colour and lustre is yellow, but there is no crack, warp, the phenomenon such as bubble. Atmospheric exposure aging test show that the sample of aging is always situated, xiangyang the aging speed is back the sun block, which indicates that the aging of PMMA is mainly the role of ultraviolet radiation. Solvent and the process of production, processing, installation and use of the introduction of internal stress is an important factor of accelerated aging, is also caused by injection molding processing PMMA materials and products are the root cause of the crack.

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