The mechanical qualities of nylon may be considerably improved by adding fillers like glass fibers and tougheners. However, the phenomenon of “floating fibers” frequently happens during the injection molding process of nylon reinforced with glass fiber. Exposed fiber, also known as floating fiber, refers to glass fiber that is exposed on a product’s surface and is often rough. The use of such items is restricted because of the exposed glass fiber. Below is an analysis of the “floating fiber” phenomenon’s causes and potential remedies.

Why “floating fiber” phenomenon occurs

01 Difference in Base Material and Glass Fiber Density

Due to the fluidity and density differences between glass fiber and resin, which exist throughout the plastic melt flow, the two tend to separate, with the resin sinking inside and the glass fiber floating to the surface, resulting in the phenomenon known as “glass fiber exposed.”

02 Poor compatibility between nylon and glass fiber

Local viscosity variations will result from the plastic melt being subjected to the friction and shear forces of the screw, nozzle, runner, and gate throughout the flow process, and at the same time, the interface layer on the surface of the glass fiber will be destroyed. The interface performs better the lower the melt viscosity. The bonding force between the glass fiber and resin decreases with the severity of the layer degradation. The glass fiber will progressively amass on the surface and become exposed when the bonding force is low enough to release it from the resin matrix’s grip.

03 Fountain effect,

A “fountain” effect will be created when the nylon melt is injected into the mold, causing the glass fiber to flow from the inside to the outside and make contact with the cavity’s surface. The light-weight, quickly condensing glass fiber is immediately frozen due to the low surface temperature of the mold; if it is not completely enveloped by the melt in time, it will be exposed and create “floating fibers.”

Therefore, the development of the “floating fiber” phenomena is connected to the molding process, which is very complicated and unknown, as well as the composition and properties of plastic materials.

A remedy for “floating fiber”

01 Mold component

To lessen the visual reaction to glass fiber exposure, the product’s outside surface is purposefully made matte or etched.

02 Increase the compatibility of nylon with glass fiber

Add compatibilizers, dispersants, and lubricants, such as silane coupling agent, maleic anhydride graft compatibilizer, fatty acid lubricant, and certain locally produced or imported anti-glass fiber exposure agents, etc., to the molding material through These additives are used to enhance glass fiber exposure by enhancing the compatibility of glass fiber and resin, uniformity of dispersion, interface bonding strength, and reducing the separation of glass fiber and resin. According to studies, compared to the matrix without the compatibilizer, the modified glass fiber’s compatibility in the matrix is greatly improved.

03 Better circumstances for the molding process

① Boost filling rate

Glass fiber and plastic have different flow velocities after speeding up, however compared to high-speed injection, the fraction of this relative velocity variation is minimal.

② Boost the mold’s temperature

The best impact is this one. In order to decrease contact resistance and to lessen the speed difference between the glass fiber and the plastic, the mold temperature should be raised. And as the plastic flows, make the centre molten layer as thick as you can, and the skin layers on each side as thin as you can, exactly like a smooth river bank couldn’t support branches. This idea is applied in the RHCM high-speed, high-temperature molding process to provide the appearance of no floating fibers.

③ Lower the temperature of the screw’s metering part to lessen the quantity of sol

This reduces the likelihood that glass and plastic fibers may separate. Generally speaking, it has little influence during real operation and has the least impact on floating fibers. The burned, however, are well-cared for by this one. This is due to the fact that adding glass fiber makes it simple to clog the exhaust channel, making it challenging to exhaust at the conclusion, and glass fiber is simple to burn in an atmosphere with high pressure and high oxygen gas.