Acrylic process characteristics
1. Polymethyl methacrylate contains polar side of methyl, with a more obvious hygroscopicity, water absorption is generally 0.3% -0.4%, must be dry before molding, drying conditions are 80 ℃ -85 ℃ dry 4-5h .
2.Methyl methacrylate has obvious non-Newtonian fluid properties in the temperature range of molding process. Melt viscosity will decrease obviously with the increase of shear rate, and the melt viscosity is also sensitive to the change of temperature. Therefore, for the polymethyl methacrylate molding process, to improve the molding pressure and temperature can significantly reduce the melt viscosity, to obtain better mobility.
3. The temperature at which poly (methyl methacrylate) starts to flow is about 160 ℃, and the temperature at which decomposition begins is higher than 270 ℃, with a wide range of processing temperature.
4. MMA melt viscosity is high, the cooling rate and faster, easy to produce internal stress products, so the molding process to control the demanding conditions, products also need to be post-processing molding.
5. polymethyl methacrylate is an amorphous polymer, shrinkage and its range of changes are small, generally about 0.5% -0.8%, is conducive to forming a high dimensional accuracy of the plastic parts.
6. PMMA cutting performance is very good, the profile can be easily machined to various sizes.