| Analysis on the reasons and solutions of glass fiber exposure |
| From：北京佳合恒泰材料科技有限公司 官方网站 Date：2018-04-16
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For a long time, in order to improve the performance of products, such as strength and temperature resistance, using glass fiber to enhance plastics has become a very good choice. A lot of facts have proved the good performance of glass fiber. However, glass fiber and plastics themselves are two different materials, which naturally produce the compatibility of the two.
Glass fiber exposure (or floating fiber) is a direct reflection of the compatibility between the two. And glass fiber exposure is also a problem that many friends often encounter and worry about in the process of fiber injection molding.
So how does glass fiber produce? In short, from the form of glass fiber, glass fiber has long fiber and short fiber, and it is a bunch of white. Fiberglass is made from glass fiber and resin.
When ejecting glue, the flow of material is similar to the way of liquid flow. You should have seen that there are some branches and other debris in the river, and there are some of them that are attached to the river bank to stay. If it"s in injection, it"s glass fiber.
This is because the flow of glass fiber relative to the plastic is much worse, and the flow of plastic in the mold is from the middle of the interlayer, the two sides move in the way, so the best liquidity is sure to go to the front, and the poor fluidity will stay on the surface of the mold.
At the same time, glass fiber can promote crystallization, while PP and PA belong to crystalline materials. Crystallization is fast cooling, fast cooling, and glass fiber is difficult to be bound and covered by resin, so it is easy to produce glass fiber exposure.
At present, the usual solutions are mainly as follows:
1. Materials:
1, considering the compatibility of glass fiber and matrix, surface treatment of glass fiber, such as adding some coupling agents and grafts.
2, adding lubricants, lubricants mainly consider the dispersion of glass fiber and some lubricants themselves have external lubrication, in the forming of easy to run to the surface of products to form a smooth layer.
3, there are some other fillers that also improve the effect.
Two, injection processing:
1, improve the temperature of the material and the mold.
2. High pressure and high speed;
3. The rapid cold and hot forming technology (RHCM) is used.
Because if the molten plastic solidifies too fast when it contacts the die wall, the glass fiber can not be completely covered, that is, the phenomenon of surface floating fiber. For the RHCM molding, the glass fiber can be completely coated by the plastic melt at the high mold temperature, and the orientation of the glass fiber tends to be consistent because of the melting state, which ensures the uniformity of the shrinkage and thus ensures the quality of the molding.
Three, mold aspect
The appearance of the product is deliberately made into sub gloss or etching surface to reduce the visual reaction of glass fiber exposure.
At present, nylon plus fiber is the most widely used material on the market. Due to the exposure of glass fiber, the application of such products has been limited. At present, it is mainly applied to some high strength structural parts. It is basically subglossy or etched (such as electric tools), because ordinary fibre reinforced material is difficult to make a bright appearance.
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