| 摘要 |
<p>To cause expansion, a composition in a molten state, comprising a polymer with an expansion agent, is extruded through a die. The product is cooled and cut by a blade at the die outlet. The expansion agent is a gas dispersing or dissolving in the molten polymer. It is pore-forming. It is a volatile compound able to dissolve in the molten polymer. It is a chemical compound able to react chemically with the polymer through heating, generating a gas. The expansible composition includes a nucleation agent and/or a surfactant and/or a plasticizer. The composition includes reinforcing additions, e.g. glass fiber, mat-forming agents, pigments, coloring agents, stabilizers against light and/or heat, bio-active agents, anti-soiling agents and/or antistatic agents. The bead is up to 10 mm in diameter, preferably 5 mm or less. The superficial density is 0.8 g/cm 3> or less, preferably 0.5 g/cm 3> or less and especially 0.3 g/m 3> or less. An independent claim is included for the corresponding polyamide bead.</p> |
