Notes on carbonization of plastic products

1 Temperature and time control

The processing temperature of plastic products is determined according to the requirements of raw materials and plasticization of products, and can not be too high or too low. Too low temperature will lead to too much load, but also the appearance of the product water lines and weld marks and other defects. If the temperature is too low, the fluidity of the melt will be poor - some, on the surface of the product glossiness and the full of edges and corners also have a greater impact. If the temperature is too high, and sometimes the temporary shutdown for two hours, or even a few hours, it is easy to produce melt carbonization in the machine. In this case, the constant temperature is between 100 and 120C, and it needs to be heated to the required temperature before starting, which can prevent the carbonization caused by a sudden rise in temperature or a long shutdown time.

2 Heating and boot operation control

Usually, one-step heating method is used, that is, after setting the temperature, continuously heating to the set temperature, according to the size of the equipment, and then keep the constant temperature for 1~3 hours before starting. This method is easy to carbonize the residual plastic in the machine. If the step heating method is used, the effect is much better.

For example, set the temperature to 100 degrees Celsius at the beginning, then set the temperature to 130 degrees Celsius after the constant temperature, then set the temperature to 170 degrees Celsius, gradually heating up according to the time period, until the temperature rises to the required temperature. Medium and small equipment to reach the required temperature can be turned on, of course, need to do the relevant preparatory work in advance. Large equipment in reach the required temperature, the need for a constant temperature of 1 to 2 hours to start better.

When the machine is just started, it is necessary to pay attention to the speed of the extruder from 1-5 RPM slowly accelerate, the feeding port is slowly opened, and pay attention to the current value displayed on the extruder ammeter at any time. If the load is too large, it is appropriate to extend the constant temperature time, so as to achieve step by step temperature rise, start the machine as early as possible, and prevent the residual plastic from carbonizing in the long starting waiting time.

3 Shutdown and temperature off operation control

Usually, the shutdown operation is to close the feed port of the extruder before the shutdown, and eliminate the plastic melt in the machine. With the reduction of the current of the extruder, the plastic melt in the machine is gradually eliminated, and then stop the temperature. This conventional method is due to the high temperature in the machine and the mold mouth is not closed, a small amount of plastic adhering to the inner wall of the machine is easy to heat deterioration in the cooling and heating process, plus the oxygen entering the air from the mold mouth, so that the heat deterioration intensifies into carbide.

If the new method of cooling closed shutdown is used, the effect is very good. Because the antioxidant capacity of recycled material and color masterbatch carrier - plastic is lower than the antioxidant capacity of new pure plastic, so stop the money no matter the use of recycled material, or containing ingredients, should be completely excluded in the machine after the plastic melt, add new pure plastic low speed washing machine. At the same time, the temperature is lowered by 25~35 degrees Celsius. With the decrease of temperature, the latent heat in the machine is gradually removed by the extruded plastic melt. But it is necessary to pay special attention to observe the current value of the extruder to avoid the accident of driving motor overload. When the actual temperature is lower than the normal operating temperature of about 25 degrees Celsius, according to the actual situation of melt flow, close the feed port, close the mold after the plastic melt in the discharge machine, prevent air entry, and then stop the temperature. In the above process, the washing machine can also be stopped when the actual temperature is 25~40 degrees Celsius lower than the normal operating temperature, so that the semi-flowing plastic melt fills the space inside the machine and makes it closed. In this case, pay special attention to the next heating and holding time should be properly extended to ensure that the melt in the machine is warm enough before starting.