PVC foaming regulator common problems and solutions

- Aug 10, 2018 -

PVC foaming regulator is a chemical agent used in the processing of PVC materials to achieve foaming effect. When the solubility of PVC data is not good, PVC foaming regulator can improve PVC

 PVC foaming regulator is a chemical agent used in the processing of PVC materials to achieve foaming effect. When the solution strength of PVC data is not good, PVC foaming regulator can improve the solution strength of PVC data, and make the processing performance of PVC data more stable. The PVC foaming regulator has the effect of promoting PVC melting, improving the appearance of the surface, improving the elasticity of the melt, and enhancing the elongation and strength of the melt. It is good for covering bubbles and avoiding cell collapse.

 The molecular weight and amount of PVC foaming regulator have a great influence on the density of the foamed sheet: following the progress of molecular weight, the PVC melt strength is improved, the density of the foamed sheet can be made lower, and the amount of the adjusting agent is improved. Have the same effect. However, this effect is not linear, and the molecular weight or the amount of progress is continuously added. The effect on the density of decline is not very significant, and the density will tend to be stable.

 There is an important relationship between the PVC foaming regulator and the foaming agent. The density of the foamed sheet and the foaming regulator have a balance point. Outside this equilibrium point, the foamed sheet density is not affected by the foaming agent content. The effect is to maintain stability, that is, the amount of foaming agent added cannot be reduced. The reason for this appearance is that the melt strength of PVC plastic additives is limited under a certain amount of foaming regulator. Excess gas Causes the cells to collapse or merge.

 In the PVC foam sheet extrusion process, the problems encountered can be classified into four categories, one is the question of stability; the second is the melt strength question; the third is the lubrication question; the fourth is the doubt. These four types of questions, especially the first three types of questions, will restrict each other and cross-impact. From the appearance of the appearance, it is sometimes difficult to understand immediately. To analyze and analyze the problem, the source of the problem can be solved. Lack of stability, will affect all the board surface, the board surface is yellow, and the foamed sheet is brittle. The lack of melt strength results in a large foam cell and a long longitudinal bubble. It is judged whether the melt strength is lacking. The most straightforward method is to press the sheet wrapped on the middle roll with a finger after the three rolls, and the melt strength can be felt when pressed. If it is difficult to bounce after pressing, the melt strength is poor. Since the screw structure and the cooling method are different, it is difficult to determine whether the temperature is reasonable. Generally speaking, in the load agreed by the extruder, the temperature in the 3-5 zone is preferably low. In order to obtain a uniform foamed product in a foamed pipe, it is also required to ensure that the PVC material has an excellent melt strength. The foaming auxiliaries developed by the company were developed to deal with the problem of foamed products, which can effectively improve the quality of foamed pipes. Lubricant is divided into external lubricant and internal lubricant. External slip is beneficial to demoulding. It has advantages in the appearance of the outer surface of the sheet. The outer slip is too small. The temperature in the extruder 5 is difficult to control and it is easy to heat up. This will cause the combined core. The temperature is high, and the center of the sheet has large bubbles, string bubbles, yellowing, etc., the appearance of the sheet is not smooth; the outer slip is more, the tapping will become severe, and the structure inside the mold and the slippage of the outer surface of the sheet are also It will appear as some individual representations moving back and forth irregularly on the board. Internal slip is beneficial to plasticization and melt flow. The lack of internal slip is difficult to control the thickness of the plate. The thickness of the plate is thick on both sides. The internal slip is more, which is easy to show the high temperature of the combined core. Poor sputum will bring the appearance of the sheet is not smooth