Factors Affecting the Curing Speed of EPS Pre Expander Machine
1. Cooling rate. The heat from the bubble is distributed to the surrounding air, water or other cooling medium by various heat transfer methods. More commonly, air, water or other cooling media are used to cool the surface of the bubble directly or indirectly.
Because bubbles are poor conductors of heat, it is often the case that the surface bubble has cooled and solidified into shape during cooling, while the core bubble is still at a high temperature. Assuming that the cooling and shaping is completed at this time, although the surface foam has been solidified and shaped, the core is still at a high temperature, and its heat will continue to diffuse, causing the surface temperature of the foam to rise. Together with the expansion force of the core foam, the formed foam may deform or break. Therefore, for EPS molding machine manufacturers, the cooling and curing of foam products shall ensure sufficient cooling and curing time.
In general, the cooling equipment used for EPS pre expander machine foaming molding cooling intensity and cooling efficiency to be higher than similar equipment without foaming, so that the foam can be cured in time to shape, reduce the impact of instability factors can improve the productivity of foam products, the price in the foamed polypropylene will be relatively low, but on the other hand the cooling rate can not be too fast, especially for the shortening rate of polymer. If the shortening rate of the bubble wall is too large during cooling, the gas in the bubble will not be able to contract and disperse on the bubble wall, and the bubble wall may break. Therefore, it is very important to choose the right cooling rate for different polymer foams.
2. Gas separation from the melt. During bubble expansion, the gas separates from the melt and enters the bubble, resulting in an increase in melt viscosity on the bubble wall and accelerating the solidification process.
3. Decomposition and vaporization of the blowing agent. The foaming process of physical blowing agent usually includes gasification, gas partitioning and expansion. In the foaming process using chemical blowing agents, the decomposition of chemical blowing agents with heat absorption or exothermic effect. The crystallization process of polymers is generally exothermic, and all these factors affect the curing rate of the foam.