Horizontal injection molding machine process conditions temperature (barrel temperature, nozzle temperature, mold temperature) on the properties of the polymer melt flow.
Cylinder temperature are the main factors influencing the melt viscosity, setting a reasonable because of polymer melt under any given shear rate viscosity is mainly decided by two factors: the melt in the free volume change and the entanglement between the macromolecular chain. Free volume refers to the space is not occupied by polymer in polymer, are the sites of macromolecular chain activities;
Macromolecular chain entanglement between can make movement of molecular chain becomes difficult, try to reduce tangles role factors, can accelerate the molecular motion between decreased viscosity. Reasonably set the cylinder temperature can increase the activation energy of molecular unit slip (flow) between the molecules become more convenient, is advantageous to the injection molding control.
Nozzle temperature setting principle in the melting point of the material as the basis, make inside the cylinder has been on the molten material, not to melt flow resistance. Mold temperature and the complexity of the product structure, a direct relationship between the type of plastic raw materials, generally choose the material by appropriate mould temperature in the middle section, enhance the proportion of material accounted for more than 30%, should be appropriate to improve the die temperature, so melt filling smoothly.
Mold temperature has a decisive effect on crystallization of materials, plastic parts of different sizes of crystallization rate will lead to the differences, according to different occasions of plastic parts to special attention mould temperature are: high mold temperature can improve the rigid plastic and surface hardness, horizontal injection molding machine mold temperature low to get good plastic toughness.
Pressure (injection pressure, holding pressure, plasticizing (back pressure) pressure, static pressure mould's influence on the forming process. Injection pressure has a decisive influence on quality of plastic parts, the effect of polymer by heating pressure at the same time, the volume has a different degree of narrow, free volume of polymer are also shrinking, viscous fluid viscosity has been increased. So simply by increasing pressure to improve the flow of polymer melt is inappropriate. Should according to different parts of the structure, shape, respectively take different pressure control.
Due to the material flow driven by pressure, melt glue, cooling surface and the mold wall place, and in the middle of the lining continues to move forward, form the drag force between melt and mold wall, the inner flow velocity is large, through the gate of the highest pressure, velocity, and molecular orientation is proportional to the pressure drop, cause the gate before the orientation of maximum and peak for O, and molecular orientation is quantitative relationship with the plastic parts wall thickness.
By freezing the molecular orientation can improve the strength of the plastic parts, but the phenomenon that molecular unit is in a state of the oppressed, because of the molecular structure is spherical, and due to the molecular orientation effect to forcibly straightening neat formation of carbon carbon bonds, one has to adapt to the situation (such as high temperature and pressure) was back to square one, and so are prone to warp, and even cracking. Injection pressure control can effectively reduce or reduce the molecular orientation, keep the plastic pieces of apparent brightness and good inner quality.