METHOD OF PRODUCING THERMOFORMED ARTICLES FROM GAS IMPREGNATED POLYMER

摘要

A solution is proposed for forming a thermoplastic material (116) into a desired shape. A corresponding method comprises increasing the thermoplastic material's degree of crystallinity by infusing the thermoplastic material (116) with a gas for a period, wherein the thermoplastic material (116) includes a core (304) and a surface layer (306a, 306b) adjacent the core (304), and has a threshold degree of crystallinity above which bubbles will not nucleate when the gas-infused thermoplastic material is heated to its glass-transition-temperature, and wherein the increase in the material's degree of crystallinity includes the surface layer's degree of crystallinity being greater than the core's degree of crystallinity, and less than the thermoplastic material's threshold degree of crystallinity; allowing, for a period, gas infused into the thermoplastic material (116) to migrate out of the material (116); nucleating bubbles in the gas-infused thermoplastic material (116) by causing the gas-infused thermoplastic material (116) to reach a temperature that is at least the glass-transition-temperature of the gas-infused thermoplastic material (116); holding, for a period, the temperature that is at least the glass-transition-temperature of the gas-infused thermoplastic material (116) to allow the bubbles to grow in size; reducing the temperature of the gas-infused thermoplastic material (116) to stop the bubbles from growing in size; and thermoforming the thermoplastic material (116) into a shape.