Mechanically Reinforced, Flexible, Hydrophobic and UV Impermeable Starch-Cellulose Nanofibers (CNF)-Lignin Composites with Good Barrier and Thermal Properties

Miao Wang,Jean-Marie Bouquet,Eric M Thompson,Bin Zheng,Christofer Troedsson,Yadong Zhao

doi:10.3390/polym13244346

Abstract

Bio-based composite films have been widely studied as potential substitutes for conventional plastics in food packaging. The aim of this study was to develop multifunctional composite films by introducing cellulose nanofibers (CNF) and lignin into starch-based films. Instead of costly and complicated chemical modification or covalent coupling, this study optimized the performance of the composite films by simply tuning the formulation. We found that starch films were mechanically reinforced by CNF, with lignin dispersing as nanoparticles embedded in the matrix. The newly built-up hydrogen bonding between these three components improves the integration of the films, while the introduction of CNF and lignin improved the thermal stability of the starch-based films. Lignin, as a functional additive, improved hydrophobicity and blocked UV transmission. The inherent barrier property of CNF and the dense starch matrix provided the composite films with good gas barrier properties. The prepared flexible films were optically transparent, and exhibited UV blocking ability, good oxygen-barrier properties, high hydrophobicity, appreciable mechanical strength and good thermal stability. These characteristics indicate potential utilization as a green alternative to synthetic plastics especially for food packaging applications.

Highlights

Synthetic polymers, especially petroleum-based plastics as food packaging materials, play critical roles in our daily life and the development of society
The tunicate cellulose was subjected to high pressure homogenization and was disintegrated into elementary fibrils or microfibrillar aggregates, termed tunicate cellulose nanofibers (CNF)
Novel starch–CNF–lignin composite films were successfully prepared by a facial blending–casting–evaporation method

Summary

Introduction

Especially petroleum-based plastics as food packaging materials, play critical roles in our daily life and the development of society. Due to inherent non-degradability in nature, plastics cause serious land and marine pollution, threatening the health of humans and other animals [1]. Finding suitable replacements for synthetic plastics is still a challenge [2]. Many bio-based materials have been chosen as potential candidates to replace synthetic plastics due to their abundance, low cost, renewability and biodegradability [3]. Starch is composed of glucose units with α-1,4 linkages. It is a low cost material and abundantly available in large quantities from several renewable plant sources [4]

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