Foaming enhanced barrier properties in bio-based polymer nanocomposite film

Overview

This research proposes a bio-based polymer nanocomposite film designed to deliver tunable barrier properties and compostability for sustainable packaging applications. The polymer material system (PMS) combines Polyhydroxybutyrate (PHB), Poly(glycolic) acid (PGA), and montmorillonite (MMT) nanoclay. By integrating blending, composite compounding, and supercritical CO2 foaming, the approach aims to tailor the micro- and nanostructure of the film to optimize oxygen and moisture barrier performance.

The synergy of these processing techniques enables strain-induced filler alignment and crystallization, which enhance the tortuosity of gas diffusion pathways. This makes the resulting film a promising candidate for food packaging, pharmaceutical packaging, and other applications requiring high barrier performance combined with environmental sustainability.

Technical specifications

Material composition:

• Polyhydroxybutyrate (PHB): Provides superior biodegradability under both aerobic and anaerobic conditions
• Poly(glycolic) acid (PGA): Contributes high oxygen and moisture barrier properties through its crystallinity
• Montmorillonite (MMT) nanoclay: Enhances barrier properties via high surface area-to-volume ratio and interlayer space that increase gas diffusion tortuosity

Processing approach:

• MMT nanoclay is dispersed in PHB-PGA blend using a microcompounder
• Extrudate is compression molded into films of 100 to 250 micrometers thickness
• Supercritical CO2 foaming induces strain-based nanoclay alignment and PGA crystallization
• A constraining mold directs expansion to preferentially align nanoclay platelets

Characterization methods:

• High-resolution imaging (micro-CT and SEM) for phase morphology assessment
• Differential scanning calorimetry for crystallinity characterization
• Fourier transform infrared spectroscopy for functional group analysis
• Mechanical testing and gas/water permeability testing for barrier property validation

Technology readiness level

The underlying hypotheses have been validated in prior studies by the lead investigator in different applications. Previous work demonstrated that supercritical CO2 foaming facilitates strain-induced alignment of thermally conductive fillers in thermoplastic polyurethane matrices, enhancing effective thermal conductivity. Additional research showed that supercritical CO2 processing can tailor the electroactive phase crystallization of polyvinylidene fluoride.

The current project will be led by Dr. Leung, Dr. Melenka, and Dr. Garces to extend these findings to barrier applications. The work focuses on elucidating processing-structure-property relationships through systematic formulation variation and comprehensive characterization. The technology is at an early-to-mid stage of development, with ongoing validation of barrier performance, mechanical properties, and compostability.