Materials and methods

A method of forming a shaped foamed polymer article from a polymer composition;

• wherein the shaped foamed polymer article is a radiofrequency lens in the form of a skinless foam having homogenous density to control permittivity;
• wherein said polymer composition comprises a polymer and a foaming agent comprising polymer shells encapsulating a gas or liquid, and
• wherein the method comprises:
• heating the polymer composition in an extruder barrel of an injection moulding tool;
• and
• forming the shaped foamed polymer article from the heated polymer composition in a mould cavity of the injection moulding tool;
• wherein:
• the polymer composition is maintained at a temperature in the mould cavity to prevent the polymer composition freezing during formation of the shaped foamed polymer article;
• and
• the foaming agent is present in the polymer composition in quantities above 10 wt % and up to 16 wt % to achieve a density reduction suitable for enabling the polymer composition to be used as the radiofrequency lens.