Views: 51 Author: Site Editor Publish Time: 2021-05-06 Origin: Site
When the polymer is in plastic injection molding, when the fluid shear rate is low, the extrudate through the die or gate has a smooth surface and a uniform shape. When the shear rate or shear stress increases to a certain value, the surface of the extrudate loses its luster and the surface is rough; when the plastic extrusion rate increases again, there will be many irregular nodules and distortions on the surface of the extrudate. Or slub pattern, or even split and break into fragments or column segments, we call it "melt fracture".
These phenomena indicate that under low shear stress or velocity, small disturbances caused by various factors are suppressed by the melt, while under high shear stress or velocity, the disturbance in the fluid is difficult to suppress and develops into an unstable flow. ; When a critical shear force is reached, it will cause the rupture of the fluid.
The peeling problem of plastic products is closely related to the rupture of the fluid caused by high shear. What are the factors that affect the peeling problem of the product during the entire plastic injection molding process? Combine materials, molds and processes for further explanation.
The rupture of the fluid under high shear leads to the skinning of the product. Compared with other materials, the two-phase structure of PC and ABS is more prone to fluid rupture and two-phase under high shear. Separation, and then the phenomenon of delamination and peeling occurs. For PC/abs materials, the two components of PC and ABS are partially compatible. Therefore, it is necessary to add appropriate compatibilizers to improve their compatibility during the modification process. Of course, because of the bad peeling caused by the mixture, we need to eliminate it in the first step.