The Effects Of Co-extrusion Process Conditions On The Performance Of Wood Plastic Composite Materials
(1)Effect of extruding molding temperature
The wood plastic composite material is mainly affected by the temperature and head temperature of the head of the machine during the squeezing processing process.The temperature of the tube mainly has a decisive effect on the mixed and plastic effect of composite materials, and the temperature of the head of the machine has an important impact on the extrusion molding.The increase in the temperature of the tube will reduce the obvious viscosity of the composite melt, which will help increase the flow rate of the melt.However, too high temperature will scorch the wooden powder, which will cause too low viscosity and not sufficient head pressure.At the same time, it is not conducive to the cooling setting. It is easy to make the surface of the product appear on the surface of the product.Therefore, it is possible to reduce the temperature of the barrel as much as possible under the premise that the material is fully plasticized. The temperature control of the transition section of the heading of the head of the machine to the cooling and fixed machine has a significant impact on the quality of the extruded product. If the temperature in this paragraph is too low, the viscosity of the wooden plastic composite materials will be increased and the flow is difficult. If the temperature of this section is raised, the surface quality of the extruded product will be greatly improved.The material through the transition section is melted. In order to obtain sufficient setting, the temperature of the head of the machine should be controlled in sections, that is, the temperature gradually decreases. It can be seen that the head temperature is very critical for the extrusion of wood plastic composite materials. The temperature of the general machine should be controlled at 135 to 150 ° C, and the temperature of the head of the machine should be slightly lower than that of 125-135 ° C.
(2)The impact of the screw speed of the extrusion machine
From the theory of solid conveying theory and viscosity fluid transmission theory, it can be seen that increasing the speed of the screw can increase the output of extrusion, reduce production costs and increase labor productivity.However, with the increase of the screw speed, the process of heating the material in the runner will be shortened, and its melting effect will deteriorate.And the material at the mouth of the mouth is too late to cool out, which will make the product cool unevenly.Causes wave patterns on the surface of the product, affecting the quality and product appearance of the extruded molding. In severe cases, the product will not be forming, making the production inconsistent.At the same time, due to the fast squeezing speed, there will be an internal stress on the extruded product, and the surface will become rough or even ruptured after the oral model is squeezed out;When the screw speed is reduced, the material is advancing forward with layers, and the material is fully cooled. The surface of the product is very smooth, the appearance quality is good, but the output is very low.At the same time, because the screw speed is very low, the wooden powder is too long when the wooden powder stays in the runner, which can easily cause the wood powder to be burnt. Therefore, when extruded wood plastic composite materials, the best speed should be set for the extrusion machine screw, which can not only improve the quality of the product, but also increase the yield, and achieve the optimal production conditions.
(3)Impact of other process conditions
In addition to temperature and screw speed on the performance of wood plastic composite materials, the cooling speed, head pressure, exhaust, etc. also have a certain impact on it.The cooling speed at the head and port of the machine should be moderate. If the cooling speed is too fast, the surface of the material will quickly form a curing layer.If the cooling speed is very slow, the material is not easy to mold, resulting in uneven surfaces and segmented surfaces.The pressure of the head of the machine has a very important impact on the quality of the wooden plastic composite material products. When the pressure of the head of the machine is small, it is easy to make the extruded products not dense.The surface of the product is prone to ripples, and it is not available to get better products.Therefore, as long as it is within the allowable pressure range, the higher the pressure, the dense the product, the better the quality of the extruded.The effect of exhaust effect on the performance of the product is not small. When the raw materials are heated, the water and other volatile substances will be discharged through the exhaust holes.If the exhaust effect is not good, the pores will be formed in the product to affect the quality of the product.
In summary, the crowded process conditions have a certain impact on the performance of wood plastic composite materials, but their role is not isolated but restricted and influenced each other. Only by comprehensively adjusting various process conditions can we get good performance products.
