The Main Shortcomings of Plexiglass
The main disadvantage of plexiglass is the small hardness, easy to wear and tear; poor thermal conductivity, large coefficient of thermal expansion; subject to temperature, sunlight and solvents, the role of nature will change. It changes under the influence of external factors mainly in the following aspects:
(1) Mechanical properties deteriorate when temperature changes. As the temperature increases, the mobility of plexiglass increases, the intermolecular gravity decreases, so the strength and hardness will be gradually reduced, while the plastic is increased. When the temperature exceeds 80 ℃, plexiglass is very easy to deformation. As the temperature decreases, the brittleness of the plexiglass increases, and cracks easily occur when subjected to vibrations.
(2) it is easy to produce silver stripe when the temperature changes sharply. Due to the poor thermal conductivity of the plexiglass and the expansion of the thermal expansion system, when the temperature changes rapidly, the thermal stress often occurs between the surface layer and the inner layer due to the larger temperature difference and the expansion shrinkage inconsistency, resulting in tiny cracks on the plexiglass surface. These fine cracks appear in the sunlight or from a certain angle, showing a silver gloss. So it is usually called the silver stripe. When the organic glass produces a silver stripe, the light intake will decrease, and the strength and the plasticity decrease.
(3) it will be oxidized under the action of sunlight. Plexiglass is stable in chemical properties, but it will also oxidize due to ultraviolet radiation in sunlight, which makes the molecules of oxygen and plexiglass in the air more active. After the oxidation of the plexiglass, the original molecules will break down into many small molecules, the color becomes yellow and the transparency decreases. In addition, the long-term exposure of the sun also causes the plasticizer in the plexiglass to evaporate and make it kneel. In the case of higher temperature, it should not be overforce on the plexiglass to prevent deformation. When the temperature is low in winter, attention should be paid to the prevention of vibration because of the fragility of the plexiglass. In addition, should not make the hard material contact with the plexiglass, so as not to scratch.
(4) dissolving in acetone, ethyl acetate and other solvents. Acetone, ethyl acetate (paint and paint remover often contain such solvents) contact with plexiglass, it will soon dissolve the plexiglass surface and turn it into milky white with poor transmittance. This phenomenon is usually called “fog” (sometimes called “fissures”). Therefore, it is necessary to prevent the contact of acetone and ethyl acetate from the plexiglass. Gasoline and alcohol have little influence on the plexiglass, but it can make it slightly dilated and should not be attached to the plexiglass for a long time.