White edges are injection defects specific to modified […]
White edges are injection defects specific to modified polyethylene and plexiglass, and are mostly found on the edge of the part near the parting surface. The white edge is an aggregate composed of a myriad of stretched orientation molecules perpendicular to the direction of the flow and a fine distance between them. There is still a polymer connecting phase in the direction of the white side, so the white edge is not a crack, and under appropriate heating, it is possible to cause the stretched oriented molecules to return to the natural curl state and the white edge to retreat.
1. The production process should pay close attention to the close matching of the parting surface of the template, especially the area around the cavity, which must be under the true sufficient clamping force to avoid longitudinal and lateral expansion.
2. Reduce injection pressure, time and amount, and reduce molecular orientation.
3. Apply oily release agent to the white side of the die face. On the one hand, this position is not easy to transfer heat, and the high temperature time is maintained more. On the other hand, the white edge may be inhibited.
4. Improve mold design. If the material with small elastic deformation is used to make the mold, the mechanical bearing capacity of the side wall and the bottom plate of the cavity is strengthened, so that it can withstand the high pressure impact during injection and the sharp rise of the working process temperature, and the higher the white edge prone area. The temperature compensation changes the flow direction and makes the flow distribution in the cavity reasonable.
5. Consider refueling.