Use of nitrogen as a blowing agent for the production of fine-celled high-density polyethylene foams

While many experiments have been performed to examine the effects of administering CO2 as a blowing agent in the foaming process, very few studies have investigated the use of N-2 for this purpose. In this study, foaming experiments were conducted in extrusion using HDPE as a polymeric material and N-2 as a blowing agent. Talc was used as a nucleating agent, and three different pressure-drop rates were applied to study the effects of pressure-drop rates on HDPE foams. The experimental results revealed that the void fraction of high-density foams blown with N-2 was not affected by the die temperature, contrasting the situation in low-density foams. Surprisingly, it was the cell density which determined the void fraction of high-density foams. It was also found that the use of talc significantly increased the cell density and the void fraction of the foams and minimized the role played by the pressure-drop rate in cell nucleation.