PVC foam boards are used in all walks of life, especially in building materials. Do you know what problems may arise during the production of PVC foam boards? Below, the editor will tell you about them.
According to different foaming ratios, it can be divided into high foaming and low foaming. According to the softness and hardness of the foam texture, it can be divided into hard, semi-hard and soft foams. According to the cell structure, it can be divided into closed-cell foam plastics and open-cell foam plastics. Common PVC foam sheets are hard closed-cell low-foam sheets. PVC foam sheets have the advantages of chemical corrosion resistance, weather resistance, flame retardancy, etc., and are widely used in many aspects, including display panels, signs, billboards, partitions, construction panels, furniture panels, etc. Insufficient melt strength will lead to large cells in the foam sheet and long longitudinal sections. The direct way to judge whether the melt strength is insufficient is to go behind the three rollers and press the plate wrapped on the middle roller with your fingers. If the melt strength is good, you can feel the elasticity when pressing. If it is difficult to spring up after being pressed, it indicates that the melt strength is poor. Because the screw structure and cooling method are quite different, it is difficult to judge whether the temperature is reasonable. Generally speaking, within the allowable load of the extruder, the temperature in zones 3-5 should be as low as possible. In order to obtain uniform foamed products in foam sheets, it is also necessary to ensure that the PVC material has good melt strength. Therefore, the quality of the foaming regulator is very important. For example, in addition to the basic functions of a general-purpose processing aid, the foaming regulator also has a molecular weight and melt strength, which can significantly improve the melt strength of the PVC mixture and prevent bubbles and rupture. , resulting in a more uniform cell structure and lower product density, while also improving the surface gloss of the product. Of course, the dosage of yellow foaming agent and white foaming agent must also be matched.
In terms of boards, if the stability is insufficient, it will affect the entire board surface and the surface of the board to turn yellow, and the foam board will be brittle. The solution is to lower the processing temperature. If there is no improvement, you can adjust the formula and appropriately increase the amount of stabilizer and lubricant. The stabilizer is a lubrication system based on imported lubricants to enhance the fluidity of the material. Heat-resistant materials have good fluidity. , good heat resistance; strong weather resistance, good dispersion, toughening and melting effects; excellent stability, plasticizing fluidity, wide processing range, strong applicability and auxiliary internal and external lubrication. Lubricant has low viscosity, high special properties, excellent lubricity and dispersion, and is widely used in plastic processing and other industries. It has good internal and external lubrication effects; it has good compatibility with polyethylene, polyvinyl chloride, polypropylene, etc. Used as dispersant, lubricant and brightener during the molding process of PVC profiles, pipes, pipe fittings, PE and PP, to enhance the degree of plasticization, improve the toughness and smooth surface of plastic products, and can be changed one by one, making it easy to quickly find problems Wherever you are, solve the problem as quickly as possible. In terms of lubricant balance, insufficient external slip is reflected in the fact that the temperature in zone 5 of the extruder is difficult to control and easily heats up, resulting in high temperatures in the converging core, problems such as large bubbles, bubbles, and yellowing in the middle of the board, and the surface of the board is not smooth; Excessive slip will cause precipitation to become serious, which will manifest itself in the structure within the mold and the precipitation of external slip on the surface of the plate. It will also manifest as some individual phenomena moving back and forth irregularly on the plate surface. Insufficient internal slip means that it is difficult to control the thickness of the board, which is thick in the middle and thin on both sides. Too much internal slip will easily lead to high temperatures in the converging core.
Post time: Jul-03-2024