1. Polymethyl methacrylate contains polar side methyl groups and has obvious hygroscopicity. The water absorption rate is generally 0.3% -0.4%. It must be dried before molding. The drying conditions are 80 ℃ -85 ℃ for 4-5h .
2. Polymethyl methacrylate has obvious non-Newtonian fluid characteristics in the temperature range of molding process. The melt viscosity will obviously decrease 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.
3. The temperature at which polymethyl methacrylate begins to flow is about 160 ° C, and the temperature at which it begins to decompose is higher than 270 ° C, which has a wide processing temperature range.
4. The melt viscosity of polymethyl methacrylate is higher, the cooling rate is faster, and the product is prone to internal stress. Therefore, the process conditions are strictly controlled during molding, and post-processing is also required after the product is molded.
5. Polymethyl methacrylate is an amorphous polymer, and the shrinkage rate and its variation range are relatively small, generally about 0.5% -0.8%, which is conducive to molding plastic parts with higher dimensional accuracy.
6. The cutting performance of polymethyl methacrylate is very good, and its profiles can be easily machined into various required sizes.