Non-metallic couplings for flexible pipes; non-metallic couplings for flexible pharmaceutical and laboratory hoses; non-metallic couplings for tubes; pipe connectors made of non-metallic materials for joining lengths of flexible pipe; joint couplings made of non-metallic materials for pipes; couplings of plastic for pipes; couplings of plastic for tubes; non-metallic couplings for tubes; non-metallic connectors for pipes; non-metallic couplings for pipes