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Pet plastic bottle production in the analysis of the causes of bubbles and vacuum bubble
by：Lisson
2020-05-16
Melt pet plastic bottles in the process of mold filling by gas interference, often form some hole or air bubbles on the surface of products.
Now a summary about a bubble.
Technological factors: 1, the speed is too fast, make the molten plastic decomposition by big shearing action, produce gas.
2, product cooling fast, uneven contraction, especially the products for the larger wall thickness, the surface cooling speed is faster than near the center, in the process of cooling, near the center of plastic shrink and expansion to the appearance, the center filling, vacuum bubble.
3, pressure and pressure is insufficient, make molten material and cavity surface is not close to, is not conducive to air discharge.
4, back pressure, back pressure control of the speed of the screw back, back pressure is small, the speed of the screw back will be quick, easy to produce feed shortage, material into the air, not from the inlet discharge, produce a large number of bubbles.
Raw materials have water material factors.
Die mold factors trapped gas, should maintain the mold or increase the exhaust slot.
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