Coating of the EPS raw material
During the producing process of the EPS,from the storage ,sales,transporting to usage, it is hard to prevent the dissipation of the foaming agent.If dissiipating too much,it will reduce the EPS foaming ratio and increase the EPS density. Adapting some water solubility coating agent on the EPS beads surface can prolong the EPS storage time,prevent dissipating too much foaming agent and improve the foaming ratio.
Is influenced by the coating agent on the surface of the EPS particle. Through studying the dissipation rate of the EPS n-pentane , we get a conclude that the EPS particle size has much influence on the dissipation rate of the foaming agent. Because of the diffusion and the dissipation distances of the smaller particle is short, so the foaming agent dissipate at a high rate. And we also find that under the same condition, the dissipation rate of the isopentane is smaller than the n-pentane’s , although the boiling point of the former one is higher than the latter one, which proves that the dissipation rate of the foaming agent not only depends on its boiling point, but also relevant to its structure. The branched chain structure of the isopentane in the EPS particle is much tighter, so it is not apt to get out of the EPS molecular, as a result ,the EPS products’ preservation period is much longer. And the conclusion is helpful for us to choose the proportion of the n-pentane and the isopentane in the foaming agent , but whatever foaming agent has its own dissipation rate, and that can improve the packaging form of the products. Experiment indicates that the dissipation rate of the transportation vessel packaging is smaller than the paper bag packaging . As to settled the preservation period problem efficiently and quickly, we use coating agent to treat the EPS products impregnated by different kinds of foaming agents, and that will increase the products’ preservation period more than one time
- The influence of the high-concentration foaming agent
First, when we select a foaming agent ,we should consider the compatibility of the foaming agent, so as to preserve a coat with gas-barrier property on the EPS particle surface and prevent the foaming agent dissipate. Foaming agent can adhere to the EPS particle surface, and at the same time, prevent the foaming agent dissipation, and that can lower the diffusion coefficient of the foaming agent in the coating layer, and the foaming agent concentration between the EPS particle surface and the coating agent will get closer to the particle’s inner concentration because of the coating agent’s prevent. In this way, the particle’s inner diffusion thrust can also be reduced. Make coating agent of different concentration , and doing experiments to expand EPS particle. The result is as shown in the Form 4-20 and the chart 4-16 . |
