Enhanced flame retardancy and electrical conductivity in nacre-inspired PBAT/montmorillonite/lignin ternary biodegradable composites reinforced with well-dispersed carbon nanotubes

Abstract

Poly(butylene adipate-co-terephthalate) (PBAT) has shown great promise as a biodegradable plastic for packaging film production. However, its inherent flammability and tendency to produce molten droplets during combustion pose significant fire risks and safety concerns. This study focuses on developing a PBAT composite designed to enhance safety by addressing these flammability issues. The composite incorporates montmorillonite (MMT) and lignin as fillers, drawing inspiration from the "brick-mortar" structure observed in natural nacres. Organically modified MMT acts as the primary "brick" component, while coupling agent-modified lignin entangled with PBAT serves as the "mortar," effectively binding and anchoring the inorganic layers together. This unique structural configuration improves interfacial compatibility by abundant intermolecular forces and reinforces the nanosheets, resulting in superior mechanical properties. Furthermore, the composite demonstrated significant flame retardancy. It formed a protective carbon layer during combustion that blocks oxygen access, inhibited the release of combustible volatiles, and prevented molten droplet formation, thereby reducing fire hazards. The addition of carbon nanotubes (CNTs) further boosted the mechanical strength of the composites and provided electrical conductivity. Remarkably, the electrical conductivity of these composites increased with ambient temperature, suggesting that the CNTs established robust interfacial connections and created effective conductive pathways. This feature enabled the composites to exhibit pronounced resistance changes and enhanced responsiveness to temperature variations. In conclusion, this study introduces a novel approach for preparing flame-retardant PBAT composites, incorporating intelligent detection capabilities and fire protection attributes. These composites hold potential for application in large-scale packaging materials, offering both safety and functional advancements.