Analysis of the causes and solutions of plastic glass fiber exposure

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In order to improve the strength and temperature resistance of the product, it has become a very good choice to use glass fiber to modify the plastic. A large number of facts also prove the good performance brought by glass fiber. However, glass fiber and plastic itself are two different materials, which naturally leads to compatibility problems between the two.

Glass fiber exposure (or floating fiber) is a direct manifestation of the compatibility problem between the two. The glass fiber exposure is also a problem that often encounters and plagues many friends during the injection molding process of fiber-added materials.

So how does the fiberglass exposure come into being? In short, from the shape of the glass fiber, the fiberglass has the distinction of long fiber and short fiber, which is a bundle and is white. Adding fiber is the blending of glass fiber and resin.

When the glue is applied, the flow of the material is similar to the flow of the liquid. Everyone should have seen the river. When there are some branches and other debris in the river, there are often some such rivers along the coast. If it is in the injection molding, it is the glass fiber exposed.

This is because the fluidity of the glass fiber is much worse than that of the plastic, and the flow of the plastic in the mold flows forward from the middle of the interlayer, and the two sides flow in the outward direction, so the best fluidity is sure to run to the most. In front, the poor fluidity will stay on the surface of the mold.

At the same time, glass fiber has the function of promoting crystallization, and PP and PA are all crystalline materials. Crystallization is quick to cool; when cooling is fast, the glass fiber is difficult to be bound and covered by the resin, so that the glass fiber is easily exposed.

The current common solutions are mainly the following:

First, the material aspect:

1. Considering the compatibility of the glass fiber and the matrix, the surface treatment of the glass fiber, such as adding some coupling agent and graft;

2, the addition of lubricants, lubricants mainly consider the dispersion of glass fiber and some lubricants have external lubrication, easy to run to the surface of the product to form a smooth layer.

3, there are other fillers have improved effects, here are not listed one by one.

Second, injection molding processing:

1. Increase the material temperature and mold temperature;

2, high pressure and high speed;

3. Adopt rapid cold forming technology (RHCM).

Because if the molten plastic cures too quickly when it contacts the mold wall, the glass fiber cannot be completely covered, that is, surface floating phenomenon occurs. For RHCM molding, due to the high mold temperature, the glass fiber at the cavity interface can be completely covered by the plastic melt, and since the portion is in a molten state, the orientation of the glass fiber tends to be uniform, thereby ensuring uniformity of shrinkage, thereby ensuring The molding quality.

Third, the mold aspect

Deliberately make the appearance of the product into a matte or etched surface to reduce the visual response of the exposed fiber.

At present, the most used fiber-reinforced materials on the market are nylon fiber-reinforced materials. Due to the exposure of glass fiber, the application of such products has been limited, and it is mainly applied to some high-strength structural parts. Anything that uses fiber-reinforced materials for appearance parts is basically a matte surface or an etched surface (such as a power tool), because it is difficult to achieve a beautiful appearance with ordinary fiber materials.