Poor stability will affect the entire board, board will become yellow and the foam sheets’brittleness is large. Insufficient melt strength will cause the cell of foamed sheet becoming bigger and the longitudinal section bulbs longer. The most direct way to judge whether the melt strength is insufficient is to press the sheet wrapped in the medium speed roll with your fingers, if the melt strength is excellent, you can feel elasticity when pressing. If it is difficult to bounce after pressing, then the melt strength is poor. Because there is larger difference between a screw structure and cooling method, it is difficult to determine a reasonable temperature. If you want to obtain uniform pvc foam board in the foam pipe, there is also need to ensure good financial strength of PVC materials. Foaming aid is developed to solve this problem of the foamed article and effectively improve the quality of the foam pipe.
Lubricant Plays an Important Role in Foam Board
Lubricant is divided into external lubricants and internal lubricants, outer slip is conducive to demolding and the surface gloss, if the outer slide is less, it is not easy to control and easy heating, which causes the high temperature of confluence core, and there will be the problems in the middle of plate, such as a large bubble, string bubble, yellow, and other issues. While if the surface of the plate the precipitation of the outer slide is not smooth; outer slide is more, precipitation will become serious. Inner slide is conducive to the fluidity of plasticization and melt, and then it is difficult to control the thickness of construction foam board, if the inner slide is insufficient. If inner slide is too more sufficient, it prone to the phenomenon of high confluence core temperature.
The Control Problems of Process Temperature
Compared with the above fundamental problems, the process temperature control will be much more intuitive, it is the surface problem, but if the temperature control is not good, it may give rise to the emergence of the fundamental problems. Improving the processing temperature, material stabilization time will be reduced, and the problems of stability will appear; the original lubrication balance will be broken, the general performance is the lack of the external lubrication, especially external lubrication in the late period of time, there is need to improve the amount of external lubrication; the increasing of temperature will lead to melt strength decreased, cell foam sheet increased, the number of cell sheet reduced, the sheet is brittle and easy to break; raise the temperature to reduce the melt strength and reduce the melt viscosity, decreasing of the viscosity reduces dispersing ability, for the screw with poor dispersion, sometimes the phenomenon of uneven dispersion.
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