US 12,285,891 B2
Materials and methods
Christopher Douglas James Spooner, Bracknell (GB); Robert Nathan Williams, Farnborough (GB); and Emma Jane Newton, Farnborough (GB)
Assigned to QinetiQ Limited, Hampshire (GB)
Appl. No. 17/630,898
Filed by QinetiQ Limited, Farnborough (GB)
PCT Filed Jul. 28, 2020, PCT No. PCT/EP2020/071183
§ 371(c)(1), (2) Date Jan. 27, 2022,
PCT Pub. No. WO2021/023559, PCT Pub. Date Feb. 11, 2021.
Claims priority of application No. 1911136 (GB), filed on Aug. 5, 2019.
Prior Publication US 2022/0281143 A1, Sep. 8, 2022
Int. Cl. B29C 44/42 (2006.01); B29C 44/00 (2006.01); B29C 44/34 (2006.01)
CPC B29C 44/005 (2013.01) [B29C 44/3415 (2013.01); B29C 44/348 (2013.01); B29C 44/42 (2013.01)] 11 Claims
OG exemplary drawing
 
1. 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.