| 摘要 |
<p>The invention relates to a method for forming an article comprising closed-cell microfoam from thermoplastic, wherein at least one molten thermoplastic comprising a foaming agent is subjected under pressure to a forming operation and, after the pressure has been at least partially released is cooled, characterized in that the amount of foaming agent is substantially identical to the amount corresponding to that quantity of gas released by the foaming agent which is comprised by a close-packed structure of the foam cells having a specific foam-cell diameter, substantially uniform throughout the foam, at the pressure prevailing during cool-down. If nitrogen is used as a physical foaming agent and PP is used as the plastic, the concentration is about 0.12 wt%, based on the weight of the thermoplastic, whereas the value is about 0.19 wt% if carbon dioxide is used as the foaming agent. Expediently, the method is implemented as an extrusion method, possibly as a coextrusion method. The use of talc as a nucleating agent is beneficial, and in the method according to the invention the talc concentration proves to be a determining factor for the mean foam-cell diameter.</p> |
