Nanocellular closed-cell flexible foams from polybutylene adipate terephthalate (PBAT)

Overview

This research proposes a method to produce nanocellular closed-cell flexible foams from polybutylene adipate terephthalate (PBAT), a compostable polymer. By incorporating dispersed polymer nanofibrils into the PBAT melt through an in situ nanofibrillation process, the technology achieves extremely fine cell structures at the nanoscale. The resulting foams offer a sustainable alternative to conventional petroleum-based flexible foams, with tunable morphology that allows balancing heat dissipation against moisture absorption depending on application needs.

The approach combines melt processing with supercritical CO2 foaming, both of which are scalable using existing extrusion and fibre-spinning equipment with only minor modifications. This makes the technology accessible for industrial partners seeking compostable foam solutions without major capital investment.

Technical specifications

• Material system: PBAT reinforced with dispersed nanofibrils of a higher-melting compostable resin such as polylactide (PLA) or polyglycolide
• Foaming methods: Supercritical CO2 batch foaming (physical blowing agent) or chemical blowing agent foaming
• Cell size: Hundreds of nanometers in diameter, significantly finer than conventional polymer foams
• Cell structure: Tunable between closed-cell and open-cell configurations
• Key mechanisms: Nanofibrils promote cell nucleation, crystal nucleation, strain hardening, and cell stabilization to prevent coalescence
• Processing: Compatible with conventional twin-screw extruders and existing spunbond or melt-blown fibre systems
• Performance benefits: Improved foam resilience and toughness compared to neat PBAT foams

Technology readiness level

The underlying in situ nanofibrillation and supercritical CO2 foaming approach has been validated across multiple polymer systems, including polyethylene, polypropylene, polylactides, thermoplastic polyurethanes, polymethyl methacrylate, and polystyrene. In each case, nanocellular structures with dramatically improved mechanical properties have been demonstrated.

For the PBAT system specifically, the research is at an early stage. Initial work would establish a processing window by foaming neat PBAT resins, followed by incorporating nanofibrils via fibre spinning extrusion and evaluating foamability through lab-scale batch foaming experiments. Industrial partners would have the opportunity to benchmark resulting foam structures and mechanical performance against their own requirements, supporting co-development toward application-specific targets.