Alec process characteristics:
1. Polymethyl methacrylate contains a polar side methyl group, which has obvious hygroscopicity, and the water absorption rate is generally 0.3%-0.4%. It must be dried before molding, and the drying condition is drying at 80 ° C - 85 ° C for 4-5 h. .
2. Polymethyl methacrylate is an amorphous polymer, and the shrinkage rate and its range of variation are small, generally about 0.5%-0.8%, which is favorable for molding plastic parts with high dimensional accuracy.
3. Polymethyl methacrylate has excellent cutting performance, and its profiles can be easily machined to various required sizes.
4. Polymethyl methacrylate has a high melt viscosity and a fast cooling rate, and the product is prone to internal stress. Therefore, the process conditions are strictly controlled during molding, and post-treatment is also required after the product is formed.
5. Polymethyl methacrylate has obvious non-Newtonian fluid properties in the temperature range of molding processing. The melt viscosity decreases with the increase of shear rate, and the melt viscosity is also sensitive to temperature changes. Therefore, for the molding process of polymethyl methacrylate, increasing the molding pressure and temperature can significantly reduce the melt viscosity and achieve better fluidity.
6. Polymethyl methacrylate starts to flow at a temperature of about 160 ° C, and the temperature at which decomposition begins is higher than 270 ° C, and has a wide processing temperature interval.