Process characteristics
1. Acrylic contains polar side methyl, which has obvious hygroscopicity, and the water absorption rate is generally 0.3% - 0.4%. Before molding, acrylic plate must be made
The drying condition is 80 ℃ - 85 ℃ for 4-5h. 2. Acrylic has obvious non Newtonian fluid properties in the temperature range of molding process. The melt viscosity decreases with the increase of shear rate, and the melt viscosity is also sensitive to the change of temperature. Therefore, for the processing of polymethylmethacrylate, increasing the molding pressure and temperature can significantly reduce the melt viscosity and obtain better fluidity. 3. The temperature at which acrylic begins to flow is about 160 ℃, and the temperature at which it begins to decompose is higher than 270 ℃. It has a wide processing temperature range. 4. Acrylic melt viscosity is high, cooling rate is fast, the product is easy to produce internal stress, so the control of process conditions is strict during molding, and post-treatment is also needed after molding. 5. Acrylic is an amorphous polymer, and its shrinkage rate and its variation range are small, generally about 0.5% - 0.8%, which is conducive to forming plastic parts with high dimensional accuracy. 6. The cutting performance of acrylic is very good, and its profile can be easily machined to various required sizes.
Processing technology
Acrylic can adopt casting, injection molding, extrusion, thermoforming, laser engraving, laser cutting and other processes.
casting molding 
Casting molding is used for molding organic glass plate, bar and other profiles, that is, forming profiles by bulk polymerization method. The post-treatment conditions are as follows: holding at 60 ℃ for 2 hours and holding at 120 ℃ for 2 hours
injection molding 
Injection molding uses suspension polymerization of granular materials, molding in ordinary plunger or screw injection molding machine. Table 1 shows the typical process conditions of injection molding of PMMA. Process parameters screw injection molding machine plunger injection molding machine barrel temperature rear 180-200 180-200 middle 190-230 front 180-210 210-240 nozzle temperature ℃ 180-210 210-240 mold temperature ℃ 40-80 40-80 injection pressure MPa 80-120 80-130 holding pressure MPa 40-60 40-60 screw speed rp.m-1 20-30 Injection molding products also need post-treatment to eliminate internal stress. The treatment is carried out in 70-80 ℃ hot air circulation drying oven. The processing time of acrylic rod depends on the thickness of the product, and generally takes about 4 hours.
Thermoforming
Hot forming is the process of making plexiglass plate or sheet into products of various sizes and shapes. The blank with required size is clamped on the mold frame, heated to make it soften, and then pressed to make it close to the mold surface to obtain the same shape as the mold surface. After cooling and shaping, the edge is adjusted to obtain the product. The method of vacuum drawing or direct pressure on punch with profile can be used for pressurization. The hot forming temperature can refer to the temperature range recommended in Table 3. When using the rapid vacuum low draft molding products, it is appropriate to adopt the temperature close to the lower limit, and to adopt the temperature close to the upper limit when forming the deep drawing products with complex shape, and generally adopt the normal temperature.