Modified ABS plastics
Although the differentiation temperature of modified ABS plastics is as high as 270 ℃, the resin often starts to change color at about 250 ℃ due to the influence of other process conditions. If the temperature is below 20 ℃ but light color and high gloss products are made, if it is necessary to shut down for 15 minutes or more, the barrel temperature should be reduced to 120 ℃.
Modified fireproof ABS plastics
In order to prevent the flame retardant from splitting during startup or shutdown of modified flame retardant ABS plastics, it is required to clean the barrel before processing. When it is necessary to stop the machine for more than 15 minutes, on the one hand, the barrel temperature must be reduced to below 100 ℃, on the other hand, the material in the barrel must be emptied, and the barrel can be cleaned with general-purpose ABS before shutdown.
All the general and modified fireproof ABS plastics require the barrel temperature to be slightly lower, and special attention should be paid to the stability of the temperature in the front of the barrel and the nozzle temperature, otherwise, the appearance will be bad.
Modified hips plastics
The modified PS plastic is generally heat resistant, but it will turn yellow when heated too long in the barrel. The residence time of 250 ℃ barrel should not exceed 5 minutes. If the temperature is 275 ℃, the residence time can not span 1 to 2 minutes. Signs of overheating of the resin will appear as twills or streaks (as if wet).
Modified PMMA plastics
If the temperature is 260 ℃, the residence time of the barrel can not exceed 10 minutes, and if the temperature is 270 ℃, the residence time cannot span 8 minutes.
Special attention should be paid to the cleaning condition of the hopper and barrel of the modified PMMA plastic. If there are other materials in the barrel, the barrel should be cleaned first (the cleaning material can be recycled material of PMMA). When there are PVC, POM and other materials in the barrel, the barrel should be cleaned with PS and other materials, and then with recycled materials, instead of PMMA recycled materials It is necessary to pay attention to this.
Modified PC plastics
It is not necessary to increase the injection pressure but to improve the injection temperature to add the activity of the melt into the modified PC plastics. It is basically not differentiated when staying in the barrel at 300 ℃ for a long time. For example, when the temperature is over 340 ℃, the PC will show differentiation, the color of the product will become darker, and the defects such as silver wire, dark stripe, black spot and bubble appear on the outer surface, and the physical and mechanical properties of the modified PC plastic are also obviously lower Down.
When starting the machine, if the materials stored in the barrel are PVC, POM and other resins with low molding temperature and poor thermal stability, you can't use PC to push and wash the barrel, and you can't increase the barrel temperature. You should clean the barrel with PE, PS and other resins with good thermal stability at low temperature. Then raise the barrel temperature to PC processing temperature, clean the barrel again with PC recycled material, and empty other resins, and then use new material for processing.
The barrel temperature should be reduced to below 160 ℃ for more than 20 minutes of temporary shutdown to prevent degradation and discoloration of materials.
Modified PPO plastics
When starting up, when the raw materials in the barrel are PA, PC, PP, etc., the modified PPO plastic can be directly cleaned. If it is PVC, POM or other heat sensitive materials which are easy to be heated and differentiated, it is necessary to replace these materials with PS or PE, and then clean the cylinder with PPO at the processing temperature of modified PPO plastic before it can be put into processing.
When the materials tend to change color and degrade in normal processing, the temperature should be lowered and the materials in the barrel should be emptied immediately. Then, PS, PE and other materials should be used to clean the barrel. After the process is adjusted, the new materials can be put into processing.
When the shutdown time is less than 15 minutes, the normal processing temperature can be maintained. If the shutdown time is more than 15 minutes, it is necessary to reduce the barrel temperature below 200 ℃. If the shutdown time reaches 2 hours, it is necessary to reduce the barrel temperature to below 100 ℃. If the shutdown time is more than 4 hours, it is necessary to clean the barrel with PS.
Modified POM plastics
Lower molding temperature and shorter molding cycle should be selected as far as possible. The molding temperature of modified POM plastics should not exceed 200 ℃ and homopolymerization should not exceed 220 ℃. At this temperature, material differentiation will occur within a few minutes; it is not allowed to stay in the barrel above 190 ℃ for too long, otherwise it will cause material differentiation. When starting up, the nozzle heating power should be turned on first, so that the nozzle is preheated first, and then the barrel heating power supply is turned on.
Before processing the modified POM plastics, if there are materials with processing temperature exceeding POM processing temperature in the barrel, the barrel must be cleaned with other resins such as PE. When the temperature drops below the POM processing temperature, the barrel is cleaned with PE, and then the POM molding operation is conducted.
In the molding process, if there is a serious smell of rhinoformaldehyde and the product is accompanied with yellow brown strips, it indicates that the material has been overheated and degraded (sometimes the moisture content is too high, but the color bar is light). At this time, the material in the barrel should be emptied by air injection method, and the barrel should be cleaned with PE. After the temperature drops to normal (or the material is dry), the processing can be carried out.
Modified PA6 and PA66 plastics
If the melt temperature of modified PA6 and PA66 plastics is above 300 ℃, it is necessary to prevent too long residence time (such as spanning 15 minutes), otherwise it will degrade the quality and make the products fade or fragile. If the plastic is overheated, it needs cleaning. If it is necessary to extend the residence time, the temperature should be reduced to 200 ℃.
Source: Jiangmen engineering plastics http://www.rolon88.com/
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