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1. Increasing the injection pressure can improve the tensile strength of PP injection parts
PP material is relatively elastic compared with other hard adhesive materials, so the density of injection parts will increase with the increase of pressure, which is relatively obvious. When the density of plastic increases, its tensile strength will naturally increase, and vice versa.
However, when the density increases to the maximum value that the PP itself can reach, the tensile strength will not continue to increase even if the pressure is increased. On the contrary, it will increase the residual internal stress of the injection part and make the injection part brittle. Therefore, enough is enough. Other materials show a similar pattern, but to a different degree.
2. Hot oil injection molding can improve the strength of steel parts and nylon parts
Nylon and POM materials, are crystalline plastic. Injection molding with hot oil machine can slow down the cooling speed of injection parts and improve the crystallinity of plastics. At the same time, the residual internal stress of the injection parts decreases as the cooling speed slows down. Therefore, the impact resistance and tensile strength of nylon and POM molded by hot oil injection with hot oil machine can be improved correspondingly. It should be noted that the dimensions of nylon and POM parts transported by hot oil injection machine are slightly different from those of water injection molding, and nylon parts may be slightly larger.
3, melt too fast even if 180 ℃ injection will raw rubber
Usually, PVC90 degrees with 180 ℃ injection, the temperature is enough, general won't appear problem of raw rubber. But is often not noticed by the operator, or to speed up production and speed up the melt velocity of purpose, make the speed of the screw back fairly quickly, only two or three seconds, for example, screw back to the biggest melt volume at least half of the position, the PVC material is a serious shortage of heating and stirring time, melt temperature and mixed uneven raw rubber, makes the strength and toughness of molded parts will become very poor.
Therefore, in the injection of PVC materials, you must pay attention not to casually melt speed set to more than 100 RPM. If it must be quite quick, be about to remember to 5 to 10 ℃ high temperature, or increasing melt back pressure to cooperate, at the same time also note often to check for gum problems, otherwise may cause big loss. About this problem, because the general people will not care too much, so here specially put forward to remind the production must pay attention to, and remember to do a good job in inspection. On the contrary, it should be noted that if the melt speed is too slow, even the material of 180-degree injection molding PVC90 degree will cause the problem of glue burning, especially the transparent PVC, there will be many black spots and gas lines on the injection molding parts.