For a long time, in order to improve the strength and temperature resistance of products, the use of glass fiber to enhance and modify plastics has become a very good choice. A large number of facts have also proved the good performance of glass fiber. However, glass Fiber and plastic itself are two different materials, and naturally they have the problem of compatibility between the two.
Glass fiber exposure (or floating fiber) is a direct manifestation of the compatibility of the two. Glass fiber exposure is also a problem often encountered in fiber-filled materials injection molding process and troubled many of my friends.
So, in fact, the appearance of glass fiber is exactly what it produces. In short, from the aspect of glass fiber, glass fiber has a long fiber and a short fiber. It is bundled, and it is white. Adding fiber material is to be Glass fiber and resin blend granulation.
When the glue is injected, the flow of material is similar to the flow of liquid. Everyone should look inside the river. When there are some branches and other debris in the river, there are often some such shores along the shore to stay. In injection molding, it is exposed glass fiber.
This is because glass fiber has a much lower fluidity than plastic. The flow of plastic in the mold flows from the middle of the sandwich, and the two sides flow outwards. Therefore, the best liquidity is definitely to go to the bottom. In front, the poor flowability will stay on the mold surface.
At the same time, glass fiber has the effect of promoting crystallization, while PP and PA are all crystalline materials. Crystallization quickly cools down; cooling quickly, glass fiber is difficult to be bound and covered by resin, then it is easy to produce glass fiber exposure.
The current common solution mainly includes the following:
First, materials:
1, taking into account the compatibility of glass fiber and matrix, the glass fiber surface treatment, such as adding some coupling agents and grafts;
2, adding lubricant, lubricant is mainly taking into account the dispersion of glass fiber and some lubricants have external lubrication, easy to run into the surface of the product to form a smooth layer.
3, there are some other fillers also have improved results, no longer listed here.
Second, injection processing:
1, increase the material temperature and mold temperature;
2, high pressure and high speed;
3, using rapid hot and cold forming technology (RHCM).
Because if the molten plastic cures too quickly when it touches the mold wall, the glass fiber cannot be completely coated, ie, the surface is buoyant. For RHCM molding, the glass fiber at the cavity interface can be completely melted by the plastic due to the high mold temperature. Body cladding, and because the part is in the molten state, the orientation of the glass fiber tends to be consistent, ensuring the uniformity of the shrinkage, and thus ensuring the molding quality.
Third, the mold
The appearance of the product is deliberately made into a matt or etched surface, which reduces the visual response of the exposed glass.
At present, the most widely used fiber-reinforced materials on the market are nylon plus fiber materials. Due to the exposure of glass fiber, the application of such products has been limited. Currently, they are mainly applied to some high-strength structural parts. Any fiber-reinforced materials are used. The exterior parts are basically matt or etched (for example, power tools), because the ordinary fiber material is difficult to achieve beautiful appearance.
For a long time, in order to improve the strength and temperature resistance of products, the use of glass fiber to enhance and modify plastics has become a very good choice. A large number of facts have also proved the good performance of glass fiber. However, glass Fiber and plastic itself are two different materials, and naturally they have the problem of compatibility between the two.
Glass fiber exposure (or floating fiber) is a direct manifestation of the compatibility of the two. Glass fiber exposure is also a problem often encountered in fiber-filled materials injection molding process and troubled many of my friends.
So, in fact, the appearance of glass fiber is exactly what it produces. In short, from the aspect of glass fiber, glass fiber has a long fiber and a short fiber. It is bundled, and it is white. Adding fiber material is to be Glass fiber and resin blend granulation.
When the glue is injected, the flow of material is similar to the flow of liquid. Everyone should look inside the river. When there are some branches and other debris in the river, there are often some such attached river banks that stay along the coast. In injection molding, it is exposed glass fiber.
This is because glass fiber has a much less fluidity than plastic, and the flow of plastic in the mold flows from the middle of the sandwich, and the two sides flow outwards, so the best liquidity is definitely to go to the bottom. In front, the poor flowability will stay on the mold surface.
At the same time, glass fiber has the effect of promoting crystallization, while PP and PA are all crystalline materials. Crystallization is fast and fast; cooling is fast, glass fiber is difficult to be bound and covered by resin, so it is easy to produce glass fiber exposure.
The current common solution mainly includes the following:
First, materials:
1, taking into account the compatibility of glass fiber and matrix, the glass fiber surface treatment, such as adding some coupling agents and grafts;
2, adding lubricant, lubricant is mainly taking into account the dispersion of glass fiber and some lubricants have external lubrication, easy to run into the surface of the product to form a smooth layer.
3, there are some other fillers also have improved results, no longer listed here.
Second, injection processing:
1, increase the material temperature and mold temperature;
2, high pressure and high speed;
3, using rapid hot and cold forming technology (RHCM).
Because if the molten plastic is cured too quickly when it contacts the mold wall, the glass fiber can not be completely coated, which means that the surface of the glass fiber floats. For RHCM molding, the glass fiber in the cavity interface can be completely melted due to the high mold temperature. Body cladding, and because the part is in the molten state, the orientation of the glass fiber tends to be consistent, ensuring the uniformity of the shrinkage, and thus ensuring the molding quality.
Third, the mold
The appearance of the product is deliberately made into a matt or etched surface, which reduces the visual response of the exposed glass.
At present, the most widely used fiber-reinforced materials on the market are nylon plus fiber materials. Due to the exposure of glass fiber, the application of such products has been limited. Currently, they are mainly applied to some high-strength structural parts. Any fiber-reinforced materials are used. The exterior parts are basically matt or etched (for example, power tools), because the ordinary fiber material is difficult to achieve beautiful appearance.