The Primary Influencing Factors In The Processing Of Wood-plastic Composites

The influence of temperature is mainly on the two aspects of barrel temperature and head temperature. The temperature of the barrel has a resolutional effect on the mixing result of the composite material. The temperature is too low and the plastic plasticization is uneven.

The primary influencing factors in the processing of wood-plastic composites

 (1) Forming temperature

 The influence of temperature is mainly on the two aspects of barrel temperature and head temperature. The temperature of the barrel has a resolutional effect on the mixing result of the composite material. The temperature is too low, the plastic plasticization is uneven, the mixing is not sufficient, and the mixture is in the mixture. The activity in the barrel is difficult; the temperature is too high, the plastic is easily degraded, the wood powder is easily burnt, and the smoke is emitted. The temperature of the cylinder mainly has a major influence on the extrusion molding. The temperature is too low, the pressure of the head is too large, and the finished product is difficult to be extruded. Secondly, it is easy to form a blocking material; if the temperature is too high, it is too late to form a high head pressure. The extruded product is not dense, and the temperature is too high. The foaming can be foamed when it is not extruded, and it can not constitute a good bubble core, which affects the quality of the finished product.

Under the premise of sufficient plasticization, low temperature extrusion should be used. Equipment such as screws and forming dies should also have low temperature extrusion characteristics to ensure that the cells have superior shape and small diameter. The feeding section temperature should be controlled below 165 °C, the tightening section and the homogenization section should be between 160 and 180 °C, and the head and die should be set below 160 °C.

 (2) Screw speed

 The influence of screw speed on extrusion foaming is mainly manifested in the following aspects: First, it affects the extrusion pressure. The higher the rotation speed, the greater the pressure inside the extruder, and then the more favorable it is for nucleation, the number of nucleated cells is also The more the foaming rate, the higher. However, when the pressure is too high, the development of the nucleated cells is affected by the sputum, which affects the development of the cells. Second, the higher the screw speed, the stronger the shearing effect. When the shearing effect is too strong, the cells are easily merged or broken, affecting the hair. The composition of the foam body and the low-density foam; the third is that the screw speed is too high or too low, so that the stay is too short or too long, and it is easy to cause early foaming or insufficient foaming agent differentiation, which affects the average precision. Cell structure. Therefore, under the condition that other influencing factors are unchanged, there is an optimum value of the screw speed, which is generally between 12 and 18 r/min.

 (3) Extrusion pressure

 The lack of extrusion pressure will result in a rough appearance and low strength, while the higher extrusion pressure can not only control the gas-containing melt in the machine head without premature foaming, but also make the pressure difference in the die of the machine head large, then The high pressure drop rate is favorable for bubble nucleation, the number of nucleated bubbles increases, and the foaming rate also increases, which is favorable for obtaining an average precision cell structure. However, excessive extrusion pressure has an effect on the development of cells. To achieve the proper head pressure, it can be done by adjusting the screw speed, head temperature and die profile.