Supercritical CO₂ Physical Foaming vs Traditional Chemical Foaming

Many people find supercritical foaming hard to grasp at first glance and need to learn about the supercritical state in advance. Simply put, it is also known as physical foaming. Though it shares partial similarities with chemical foaming in production workflows, their core difference lies in the foaming agent adopted, and the whole production relies on professional equipment such as CO₂ Foamed sheet extruder.

1. Fundamental Differences Between the Two Processes

Physical Foaming

Supercritical fluids such as carbon dioxide and nitrogen under high temperature and high pressure act as foaming agents. The conversion of supercritical fluid into gas under normal temperature and pressure is a purely physical change. A complete set of PLA foam sheet extrusion line can realize this physical foaming process for biodegradable materials.

Chemical Foaming

It relies on chemical foaming agents like azodicarbonamide (AC foaming agent) and sodium bicarbonate. Taking AC foaming agent as an example, it decomposes when heated to release nitrogen, carbon monoxide, carbon dioxide and ammonia gas, which belongs to a chemical reaction. Traditional PS foam sheet production line mostly adopts this chemical foaming route in early designs.

2. Comparison of Advantages, Disadvantages and Process Performance

Supercritical CO₂ Physical Foaming

• Produces pure foam materials that meet food contact safety standards and feature excellent skin compatibility, matching the production demands of PLA fast food box machine.
• Delivers finer cell structure and more stable material performance compared with chemical foaming.
• Foam products boast higher impact resistance, superior thermal stability and toughness, outstanding sound insulation, as well as lower thermal conductivity, ideal for new energy insulation panels manufactured by PET foam board extrusion line.
• Drawbacks: Long saturation period limits production efficiency; rapid heating or pressure relief imposes high requirements on energy consumption and equipment safety.

Chemical Foaming (Taking AC Foaming Agent as an Example)

• High gas output capacity, relatively uniform foam cells, stable performance and wide application range.
• Adjustable decomposition temperature without interfering with curing and molding speed, featuring fully mature industrial techniques.
• Limitations: AC foaming agent is yellow crystalline powder. Its decomposition generates abundant by-products. If the powder particle size is not fine enough, excessive residues will leave peculiar odors and color deviation on finished foam products.

3. Development Trend of Foaming Technologies

Supercritical physical foaming is an emerging advanced process. Traditional chemical foaming cannot easily achieve lightweight and low-density effects for many raw materials, while supercritical CO₂ foaming enables lightweight low-density foam production for a wide range of plastics. In addition, it features eco-friendly and clean production, fully aligning with the global carbon neutrality strategy. Supporting PS Foam Recycling Machine can further build a closed-loop green production chain for foaming factories.