Foaming and Dimensional Stability of LDPE Foams with N2, CO2, i-C4H10 and CO2 - N2 mixtures as Blowing Agents

Abstract Low-density polyethylene (LDPE) foams blown with CO2 typically present severe shrinkage problems, which makes them have to be produced by using hydrocarbon as the blowing agent. In this work, we first clarified the characteristics in foaming LDPE with various pure gases (N2, CO2, and i-C4H10). The foaming behavior of the pure gases showed that i-C4H10 was weak in cell nucleation, N2 in cell growth, and CO2 in dimensional stability. Every gas type was very weak in one aspect (cell nucleation, cell growth or dimensional stability) but strong in the other two. To solve the problems of pure gas foaming, CO2 - N2 mixtures were proposed as the blowing agent to foam LDPE. The results showed that the CO2 - N2 mixture could not only produce a synergistic effect on cell nucleation, but also effectively solve the shrinkage problem of LDPE foams, which could completely eliminate the safety risks and time-consuming aging period.