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Cause Analysis And Solution Of Plastic Defect Floating Fiber
Oct 11, 2018

Injection molding production, whether you also often have problems floating fiber, fiber is a glass fiber in the product surface, rough, appearance is more difficult to accept, the possible reasons for analysis: at the time of adding this kind of filler, generally is the physical mix method, so just glass fiber evenly dispersed in the middle of the plastic, but after the plastic melt, the mixture will appear different degrees of separation (depending on the length of the glass fiber and the proportion of the added, and the temperature of the raw material has a certain degree of influence)

Why is it exposed?
In injection, although the flow of material is different from the flow of liquid (liquid is Newtonian flow, plastic is non-newtonian flow), but there is a more interesting and easier to understand. You've got to look at the rivers, where there's a little bit of tree branches and stuff, and there's often a little bit of this kind of clinging to the Banks along the Banks. Because the velocity of the water along the river bank is slowed by resistance, this is similar to the skin layer at the time of filling. So these branches are in the injection molding, which is glass, which is floating.
This is because the glass fiber to much difference relative to the flow of the plastic, the plastic flow in mould is fountain flow type (fountain effect), flows from middle to both sides turn way, so the best liquidity must be run to the front, bad liquidity will remain in the mold surface (when making PP raw materials such as combination of line and the last place that also with different colors, just in the front is a waxy, and pigments separated especially additive mother's most obvious, because the pigment is typically made from PE carrier), fire-proof material mould surface adsorption and do fire retardant is also one of the reasons.

Generally, the following methods can be adopted to reduce the proportion of floating fiber:
1. Increase filling speed
After increasing the speed, the relative speed difference between glass and plastic, though different in velocity, is smaller than that of high-speed gelling, just as a river never leaves a branch in a rapids section.
2. Increase the mold temperature
This effect is the biggest, increase the mold temperature, is to reduce the glass fiber and mold contact resistance, so that the speed difference between glass and plastic as small as possible. And let the plastic flow as thick as possible in the middle of the melting layer, let both sides of the epidermis as thin as possible, such as smooth river bank can not retain the branches of the same reason. RHCM USES this principle to achieve a non-floating-like appearance.
3. Lower the temperature of screw metering section and reduce the amount of sol
This is to reduce the possibility of the separation of the plastic box glass fiber, generally speaking, the smallest impact on the floating fiber, in the actual operation. However, this can be a good solution for burning. This is because after adding the glass fiber, the glass fiber volume is much larger than the plastic, so it is easy to plug the exhaust passage, so it is difficult to exhaust at the end, and the glass fiber is easy to burn in the environment of high pressure and high oxygen gas!