Structural Design And Application Of Multifunctional Nanocellulose Enhanced Biopolyester Composites

In the past few decades,the traditional petroleum-based packaging materials have been difficult to naturally degrade and decompose for a long time,thus environmental pollution is increasingly becoming a serious problem.The use of biodegradable nanocomposites with the characteristics of"take from nature and return to nature"and comparablities in packaging can replace petroleum-based packaging materials,which have attracted widespread attention from experts and scholars.Compared to traditional plastics,poly(3-hydroxybutyrate-co-3-hydroxyvalerate)(PHBV)bioplastic is widely developed and applied due to the advantages of biodegradabilities,friendly environmental effects and biocompatibilities.However,PHBV has some structural and performance defects to limit its application and industrialization in the field of bioplastics,such as semi-crystalline,brittleness,poor thermal properties,low nucleation density and large spherulite size.The PHBV nanocomposites with different cellulose nanocrystals-rosin(CNC-R)contents were prepared by a simple solution casting method,and explored the effects of structure and properties and application tests.Studies have found that the uniformly dispersed CNC-R can be used as a good heterogeneous nucleating agent into PHBV matrix to promote the crystallization of PHBV,and the PHBV nanocomposite is endowed with barrier properties,resistance to water vapor permeability.Compared to neat PHBV,PHBV/CNC-R nanocomposites can simultaneously improve the mechanical strength/toughness and thermal stability.Among all PHBV nanocomposites,the tensile strength,Young's modulus and the elongation at break of 5 wt%CNC-R nanocomposites are increased by 107.9%,79.5%and 43.9%,respectively.The melting temperature T_m2 of 5 wt%CNC-R nanocomposites is also increased by 47.1?.Both Lan-negative(E.coli)and Gram-positive(S.aureus)show an antibacterial rate of 100.0%,and have shown potential important applications in extending the shelf life of biologically active food packaging materials.Innovatively,through the Pickering emulsion/hot pressing film method,the cellulose nanocrystals-cinnamon CNC-Cc as the"rigid unit"and the amorphous PC as the"soft unit"were synergistically introduced into the biopolyester PHBV to prepare ternary composite materials,which were explored PHBV chemical structure,thermal stability,crystallization,mechanics,anti-oxidation and and application tests.Studies have found that evenly dispersed CNC-Cc nanohybrids can improve the two-phase compatibility of PHBV and PC.And cross-links were formed network structure in the intermolecular hydrogen bonding interaction between CNC-Cc/PC and CNC-Cc/PHBV.In addition,there was the dynamic competition mechanism between PC and CNC-Cc in the crystallization of PHBV.Compared to neat PHBV,PHBV/PC/CNC-Cc nanocomposite films not only exhibit excellent antibacterial properties against E.coli and S.aureus,but also have excellent antioxidant properties and UV shielding effects.The composite materials guarantee the safety of oxidation-sensitive food during the packaging process,maintaining the taste and nutrients.After a comprehensive survey of relevant literatures,the PHBV/PC/CNC-Cc composite material in this study has salient mechanical properties(tensile strength:38.5 MPa;Young's modulus:2.19GPa;elongation at break:72.4%);especially,the mechanical toughness is also significantly improved by 821.9%,compared to neat PHBV.