Double wall plastic container - for dewar flask in place of glass

摘要

Inner and outer walls of a double walled container of the Dewar flask type are formed from a polymeric material resistant to low temps and are joined along the periphery of the opening by a welded rope of the same polymer. The containers have the advantage that suitable plastic materials are less fragile than glass and more easily fabricated. Pref. two concentric tube sections of polymeric material are flattened at their lower ends and sealed by polymerisation of the same material, the upper end of the inside envelope being sealed tangentially to the outer envelope along an opening. Polymethyl methacrylate is a prefd. material. The inner envelope is pref. reinforced by inserting a thick, open fabric and optionally also by hooping with a tubular heat shrinkable fabric. The outer envelope may also be reinforced by hoops kept in position by a light fabric.