PVC foam board is a kind of vacuum plastic board, which is made of PVC and has a honeycomb mesh structure, many used in advertising industry and furniture industry, there is embrittlement and delamination of PVC foam board, what is the reason? following, we will introduce the causes of embrittlement and delamination of PVC foam board.
1. Insufficient hot pressing time. It should be extended appropriately. If the hot pressing time is insufficient, the bonding temperature between the sheets cannot be reached. Although the sheets are barely bonded together between the lower layer and the layer under high pressure, the sheet is easy to be layered under the action of external force, such as shearing and sawing.
2. The forming temperature of PVC material sheet in the previous process of lamination is too high or the heating time is too long. This is the main reason for the brittleness and redness of the material sheet. It is worth noting that if the sheet is not formed normally in the previous process, even if the pressing temperature is properly reduced during lamination, embrittlement and redness can be avoided, but the bonding temperature of the sheet cannot be reached, which is easy to lead to plate delamination. In order to avoid delamination, if the plasticizing temperature of the sheet is appropriately increased and the pressing temperature is correspondingly increased, the embrittlement of the plate and the redness of the plate surface will be more serious. Therefore, PVC sheet should control the process conditions during the forming of single-layer sheet, appropriately reduce the forming temperature and shorten the forming heating time.
3. The sheet surface is not clean. Keep the production environment clean and remove the dust on the surface of the sheet in time. Otherwise, even if the pressing process is reasonably controlled, there will be delamination due to poor bonding between layers. During the hot pressing of PVC sheet, the forming temperature and pressure should be controlled in three stages: 1. Low temperature preheating stage; 2. Medium temperature and pressure holding stage. After a period of low temperature heating, the temperature of the middle layer can reach about 120 degrees, and then it can be transferred to the medium temperature and pressure holding stage. The purpose is to transfer heat quickly. If the sheet expands outward, it should be reduced appropriately to prevent excessive expansion of the sheet.
In the high-temperature pressing stage, when the middle layer of the plate reaches the bonding temperature, the material sheet is bonded with the lower layer in the molten flow state. The temperature in the high-temperature stage should be controlled at 170 to 175 degrees, but the heating time should not be too long, and the pressure should be maintained at 0.8 to 1MPa first.
