Influence of mold material flowability on molding process

The quality index of the molding material not only affects its fluidity, but also closely relates to the quality of the product. Practice has shown that in the quality index of the central molding material, the volatile content should be strictly controlled. The volatile content increases and the material fluidity increases. However, when the volatile matter content is too high, it is easy to cause a large loss of resin during molding, the shrinkage rate of the product is intensified, and even warpage occurs, and bubbles, ripples, flow marks, sticking molds, and surface finish are degraded on the surface of the product. When the volatile matter content is too low, the fluidity of the material will be significantly reduced, resulting in difficulty in forming the product and being extremely short of material. Therefore, it is meaningful to control the proper volatile content of the molding compound. The morphology of the molding material also has a great influence on its fluidity and product properties.

Practice has shown that premixes have better fluidity than prepregs. When the premix is ​​in a "flaky" state or in a fluffy state, the flow resistance is large, the mutual solubility between the materials is poor, and the joint performance is liable to be significantly degraded. In order to prevent the "agglomeration" of the premix, the following three measures can generally be used:

1 The length of the fibers in the premix should not be too long to avoid mutual entanglement;

2 When the machine is torn loose, the screen is supplemented with manual tearing, and the “unity” material is opened;

3 Pre-forming the material before molding to increase the fluidity of the material. Molding mold

The measures to improve the miscibility of prepreg are: using glass fiber with weak banding and strong bundleability, strictly controlling the quality index of the molding material, grasping the appropriate pressing timing, increasing the molding pressure, and increasing the preheating of the molding material. .

In short fiber molding, fiber length has a significant effect on the fluidity of the material and the mechanical properties of the product. Generally, as the fiber length increases, the strength of the article increases, but the fluidity of the material decreases. Therefore, in the preparation process of the molding material, the influence of the fiber length on the fluidity and the strength of the product should be comprehensively considered, and the appropriate fiber length should be selected according to different. Practice has shown that for products of different structures and sizes, in order to give full play to the ideal properties of the molding material, fibers of different lengths should be selected separately. In some complex structures requiring higher mechanical properties, molding of different fiber lengths can be combined in the same article.