The control method of plastic orientation
injection tooling control orientation technology. In different processing methods, using different control methods to control orientation. The method of controlling the orientation in injection molding, in order to improve the injection pressure, the increase of injection pressure, degree of orientation increased almost linearly. Using two methods in calendaring, may control orientation. One is increase the shear force, specific methods to increase the shear roller speed ratio, the second is to improve the traction rate, external force exerting traction. In the extrusion molding, the best way to control the orientation to improve the traction rate, in order to improve the extrusion direction orientation degree.
stretch orientation technology. This method is below the melting point, this method is below the melting point, glass transition temperature above the high elastic state condition, impose on tensile force on thin plastic products, making it the force direction orientation is a way. Stretch orientation technology is one of the most effective control orientation direction, can greatly improve the degree of orientation, and obviously improve the plastic products of tensile strength, impact strength, barrier property and transparency, etc. Its shortcomings are only suitable for thin wall products, and not suitable for thick wall products.
stretch orientation there are three kinds of methods: 1. Two-way tensile membrane tube at the same time, this method is suitable for extrusion blown film, it will have the molding pipe transverse tensile membrane blew up again after heating, and in the traction to exert on the longitudinal tensile force. This method is suitable for wide film production. 2. Two-way stretch flat membrane method at the same time, this method is suitable for extrusion film production methods, it is to have cooling molding after heated vertical and horizontal piece of film to a method of drawing at the same time. 3. Successive two-way tensile membrane. From extruder extrusion of diaphragm after cooling molding, reheating process, longitudinal tensile first, then carries on the transverse tensile. This method is easy to cause longitudinal and transverse direction of the two thin film on the mechanical properties of differences, but has the characteristics of the equipment has simple structure, easy operation.
the modification effect of plastic orientation optical performance. Orientation is to improve the plastic optical performance of one of the most effective way, it can improve the surface gloss of light transmittance and plastic products. But excessive orientation can increase the birefringence phenomenon, is not conducive to plastics used as optical materials. Therefore, used in optical materials of plastic product is made of casting forming method, mostly in as far as possible do not produce processing orientation, thus reduce birefringence phenomenon. Orientation can change the spherulite size, large spherulite scattering light can be produced, which affects transparency of plastic products, small spherulite instead can improve its transparency.
mechanical properties. Modified plastics through orientation, its mechanical properties can be improved generally, concrete such as tensile strength, impact strength, tear strength and resistance to fatigue strength etc. , especially in the tensile strength increased obviously. If drawing modification effect is good, can increase the tensile strength of plastics materials to close to the theoretical level of tensile strength.
thermal performance. Orientation modification can make plastic generally improved thermal performance. Orientation in the heat and low temperature resistant modification omnidirectional, but in the thermal expansion and thermal shrinkage modified has directivity. Orientation can reduce the thermal expansion coefficient of the orientation direction. But orientation increased the orientation in the direction of heat shrinkage rate, this is mainly because produced in the orientation of jun as many imbalances, when heated, unbalanced jun will happen like the rapid transformation of jun as forming balance, causing shrinkage. Orientation can be used to improve the effect of heat shrinkage rate of this modification, can produce heat shrinkable film processing, for a variety of heat shrinkable packaging.
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