fluidity of different plastic material
fluidity is divided into three categories:
1 good fluidity PE, PS, PP, CA, poly (4) methyl decene;
2 medium mobility, polystyrene series resin (such as ABS, AS), PMMA, POM, polyphenylene ether;
3 poor fluidity PC, hard PVC, polyphenylene ether, polysulfone, polyarylsulfone, fluoroplastic.
1. The fluidity of thermoplastics can generally be analyzed from a series of indices such as molecular weight, melt index, Archimedes spiral flow length, apparent viscosity and flow ratio (flow length / plastic wall thickness).
The molecular weight is small, the molecular weight distribution is wide, the molecular structure is poor in regularity, the melt index is high, the snail flow length is long, the viscosity is small, and the flow ratio is good. For the plastic of the same product name, the specification must be checked to determine whether the fluidity is applicable. For injection molding.
2. The fluidity of various plastics also changes due to various shaping factors. The main factors affecting are as follows:
1 When the temperature of the material is high, the fluidity increases, but different plastics also have different, PS (especially high impact resistance and MFR value), PP, PA, PMMA, modified polystyrene (such as ABS, AS) The fluidity of plastics such as PC and CA varies greatly with temperature. For PE and POM, the temperature increase and decrease has little effect on the fluidity. Therefore, the former should adjust the temperature to control the fluidity during molding.
2 When the pressure injection pressure is increased, the molten material is subjected to large shearing action and the fluidity is also increased, especially PE and POM are sensitive. Therefore, the molding pressure should be adjusted to control the fluidity during molding.
3 mold structure casting system form, size, layout, cooling system design, melt flow resistance (such as profile finish, channel section thickness, cavity shape, exhaust system) and other factors directly affect the melt in the cavity The actual fluidity inside, when the melt material is lowered to lower the temperature and the fluidity resistance is increased, the fluidity is lowered.
The mold should be designed according to the fluidity of the plastic used, and a reasonable structure should be selected. When molding, it can also control the material temperature, mold temperature and injection pressure, injection speed and other factors to properly adjust the filling to meet the molding needs.