Supercritical CO₂ Extrusion Foaming Technology: Process, Equipment & New Energy Applications

Extrusion foaming is a molding process to produce foam materials with extruders as core equipment. Foaming agents and resin are mixed for melting and plasticization inside the extruder, then foamed and shaped via precise control of pressure, temperature and residence time to form products with solid outer skin and foamed inner core. It is divided into one-step foaming and two-step foaming, compatible with PP, PET, PLA, PS raw materials to manufacture sheets, pipes, rods and films widely used in new energy, rail transit and food packaging industries. Many factories adopt mature PLA foam sheet extrusion line to mass-produce eco-friendly packaging foam.

Pressure serves as the core technical parameter. Higher pressure generates smaller foam cells; excessive temperature causes cell rupture; prolonged residence time weakens cell nucleation. The two-stage continuous supercritical CO₂ foaming complete set independently developed by Foshan Gaoming Keli Machinery Co., Ltd. breaks through technical barriers of continuous supercritical extrusion foaming, realizing mass production of V0 flame-retardant and low-dielectric materials for new energy battery and rail transit thermal insulation component manufacturers.

(1) Process OverviewPlastic raw materials and foaming additives are uniformly fed into the extruder for plasticization and mixing. Chemical foaming relies on gas generated by heated additives, while physical foaming adopts high-pressure injection of inert gas such as carbon dioxide or nitrogen. High barrel pressure prevents premature foaming; the melt expands instantly under sudden pressure drop at the die and is cooled to lock stable cellular structures. One-step foaming means direct molding at the die outlet, two-step foaming is widely matched with PET foam sheet production line for lightweight board production. The complete extrusion foaming production line realizes continuous mass production of sheets, films, pipes, special profiles and cable insulation foam layers.

(2) Process PrincipleExtrusion foaming completes melting, mixing and foaming via extruders, matched with die head, cooling calibrator, haul-off unit, cutter and winder to form an integrated supercritical foaming production line. Plastics and additives finish plasticization and foaming agent dissolution inside the barrel. High pressure at the die suppresses premature foaming; the melt expands after exiting the die and is cooled to fix finished product shapes, supporting high-volume stable automatic production.

(3) Key Process Parameters

1) Extrusion Pressure: Higher pressure reduces cell size and increases cell quantity.

2) Extrusion Temperature: There is an optimal temperature range. Overheating breaks cells, while insufficient temperature restricts bubble expansion.

3) Material Residence Time: Longer residence time suppresses nucleation and reduces the number of bubble cores.

(4) Main Extrusion Foaming UnitExtruders are core plastic machinery for most plastic molding processes. The motor acts as the power source to deliver high thrust for screw operation.

Manufacturers of new energy batteries, energy storage thermal foam and lightweight rail transit parts prioritize fluorine-free CO₂ physical foaming technology. Traditional chemical foaming is phased out due to excessive VOC emissions. For post-production waste disposal, supporting PS Foam Recycling Machine can efficiently reprocess leftover foams. New foam product factories can purchase complete extrusion foaming turnkey lines including CO₂ Foamed sheet extruder from Keli Machinery.