Investigation Of The Preparation Of Plastics Tube By Controlling Contraction Direction

In thermoplastic processing fields, Extrusion is a diverse, comprehensive and major processing method, extrusion products include continuous profile products, such as pipe, rod, thread, board, film, electric wire and cable and coating products etc. It is also used in making many high-tech products. Precise pipe is a good example, it need precise extrusion. Of course extrusion machine is still not a perfect thing. Sometimes it will also make some unwanted result if it is not controlled correctly. Such as, low quality products, unstable production will follow. Those are byproducts that we do not need.The innovation of the thesis is using plastic volumes change from melt to solid to get the hole when it cooling. Our research is a new method in making inside-hole. In today's world, the plastic industry is the fast growing department. There are many holes machining methods. Different vocation use different technologies, even in the same vocation themachining maybe differ. Some special hole cannot be made by traditional ways, especially those micro-holes, even if it can be made by traditional method, the cost of whole facilities is very expensive. For example, during the processing of precise micro-pipe, engineers more focus on the special mould than other parts of extrusion machine, which means they need to input a lot of money in making such micro-pipe, however here we use a physical method to gain the pipe, which is an innovative way.The most important part of the thesis is to make clear the mechanism of polymer pipe, as we all known, polymer can be divided into two types: crystal and amorphism by collective conditions. Crystal polymer shows some regular arrange, so it has an invariable melting point, on the other hand, the amorphism shows some irregular arrange, therefore they have no invariable melting point. As a result, their principles are different. Meanwhile, we should also consider other factor: constriction, cooling temperature, cooling liquid, drawing speed, die temperature, tube diameter, relaxation time, heat volume, conductivity of heat and the difference between solid plastics and liquid plastics. All these may contribute to the principle.On the one hand, considering plastic performances change by the temperature, a new mathematic model of cooling process of extruded plastics rods based on the theory of heat-transfer is built up. A relative energy equation for evaluating the critical condition to forming an inner...