How to solve the floating fiber in the injection molding process? (One）

What is floating Fiber and how to solve it (一)?

 

Floating fiber is also called exposed fiber. In the production of raw materials with glass fiber is most likely to appear is the surface appearance of bad, mainly for burnt, exposed fiber and material flower.And this is the most important, the most difficult to solve is the exposed fiber. The so-called exposed fiber is the glass fiber exposed on the surface of the product, relatively rough, the appearance is more difficult to accept. White glass fiber in the plastic melt mold flow process exposed to the exterior, to be condensed after molding in the plastic surface to form a radial white traces, when the plastic parts for the black will be due to the increase in the color difference and more obvious.

 

1. Improve the compatibility of glass fiber and nylon
Add compatibilizers, dispersants and lubricants and other additives to the molding material, including silane coupling agent, maleic anhydride graft compatibilizer, fatty acid lubricants and some domestic or imported anti-glass fiber exposure agents. Through these additives to improve the compatibility between glass fiber and resin, improve the uniformity of the dispersed phase, increase the interfacial bond strength, reduce the separation of glass fiber and resin, thereby improving the phenomenon of glass fiber exposure. For example, studies have shown that by adding compatibilizers to the matrix, the compatibility of glass fibers in the matrix of the modified material is significantly higher than that of the unadded material.

2.Adjustment of Inject mold casting system

The mold casting system is closely related to the formation of "floating fiber" phenomenon. For the glass fiber reinforced plastic mobility is poor, and the glass fiber and resin mobility of the two components of the characteristics of the inconsistency, the flow distance can not be too long, the melt must quickly fill the cavity to ensure that the glass fiber is uniformly dispersed, does not occur siltation and layering and the formation of "floating fiber".

Therefore, the basic principle of casting system design is that the cross-section of the runner should be large, and the flow should be straight and short. Should be used in the thick and short of the main flow channel, manifolds and coarse gate, the gate can be sheet type, fan and ring, can also be used in the form of multiple gates, in order to make the material flow chaotic, fiberglass diffusion, reduce the orientation of the sex. Moreover, it is required to have a good exhaust function, which can discharge the gas generated by the volatilization of glass fiber surface treatment agent in time, to avoid defects such as poor fusion, lack of material and burns.

As for the pouring system of the handle cover mold, its long runner flow is a factor that causes the serious phenomenon of "floating fiber", but this is the need of the mold structure, which can't be shortened, so only the cross-section size of the runner and the form and size of the gate are adjusted. The gate was changed to a fan-shaped gate, and the gate and runner size were gradually increased during the trial molding process. In addition, it should be noted that the "floating fiber" is easy to appear in the part of the molded part with large wall thickness, because the melt flow velocity gradient is large in this place, the center of the melt flow is high, and the velocity is low near the cavity wall, which makes the tendency of the glass fiber exposed intensify, and the relative velocity is slower, which results in the formation of the "floating fiber" due to the accumulation of the stagnation. "Floating fiber". Therefore, should try to make the wall thickness of the molded part everywhere uniform, and avoid sharp corners, notches, to ensure smooth flow of the melt.

In addition to the mold, the product appearance surface deliberately made of matte surface or etching surface, to reduce the visual response of the glass fiber exposed.