Forming methods

摘要

This invention relates to methods for forming a polymer, including continuously depositing a polymer extrudate that is above its glass transition temperature onto a lower molding surface of a first mold in a manner that reduces shear stress in the polymer extrudate, heating the lower molding surface to maintain the polymer extrudate above the glass transition temperature, applying an upper molding surface of a second mold to at least the exposed upper surface of the polymer, allowing the polymer to transition to below the glass transition temperature while within or between the upper and lower molding surfaces, and providing heat sinks spaced relative to each other through the pressure forming zone, wherein a heat sink more advanced through the pressure forming zone is controlled to a lower temperature to progressively reduce the temperature of the polymer as it advances through the pressure forming zone.

主权项

1. A method for forming a polymer to define a nano-scale sized surface texture onto at least part of the surface of said polymer so formed, the method comprising:
continuously depositing a polymer extrudate that is above its glass transition temperature from an extruder head onto a serially advancing lower moulding surface of a first mould;
heating the lower moulding surface, the heated lower moulding surface heated to a temperature to maintain the polymer extrudate above the glass transition temperature, the polymer extrudate being in or near a substantially liquid phase when being continuously deposited to the heated lower moulding surface,matching the linear speed of the polymer extrudate to the speed of the serially advancing lower moulding surface so that the deposited polymer extrudate is not moved with respect to the lower moulding surface,applying a serially advancing upper moulding surface of a second mould to at least an exposed upper surface of the polymer while the polymer is maintained at a temperature above the glass transition temperature, the lower and upper moulding surfaces forming a pressure forming zone, the temperature of the lower moulding surface remaining sufficiently high to keep the polymer entering the pressure forming zone above the glass transition temperature, andallowing the polymer to transition from above the glass transition temperature to below the glass transition temperature while within the pressure forming zone between the upper and lower moulding surfaces, andactively controlling heat removal from said polymer via at least one of said upper and lower moulding surfaces when said polymer is in said pressure forming zone, and transitioning said polymer from above the glass transition temperature to below the glass transition temperature whilst within the pressure forming zone; and wherein a plurality of heat sinks are provided for at least one of the upper and lower moulding surfaces, said heat sinks being spaced relative to each other along the pressure forming zone, wherein a heat sink more advanced through the pressure forming zone is controlled to a lower temperature than an adjacent heat sink less advanced through the pressure forming zone in order to progressively reduce the temperature of the polymer as it advances through the pressure forming zone; removing the polymer from the moulding surfaces, after said actively controlled heat removal.