Preparation Of Cellulose Nanocrystal/Nanosilver Hybrids And Its Synergistic Reinforcement Mechanism In Biopolyester

In recent years,petroleum-based plastic polymers have been gradually replaced by biodegradable Poly(3-hydroxybutyrate-co-4-hydroxybutyrate)(PHBV)nanocomposites.Compared with petroleum-based plastics,PHBV nanocomposites with excellent performances(good biocompatibility,high crystallinity and low toxicity)have aroused the interest of researchers all over the world.However,PHBV has defects of brittleness,poor toughness and slow crystallization rate as a result of its regular molecular chain.In this work,the PHBV nanocomposites were prepared by adding cellulose nanocrystal/nanosilver hybrids as the filler into the PHBV matrix.The effects of different nanosilver contents and polar groups(hydroxyl and carboxyl groups)on the crystallization,thermal,mechanical,bulk migration and antibacterial properties of PHBV nanocomposites were investigated.(?)Preparation of cellulose nanocrystal/nanosilver hybrids with different nanosilver contents and its synergistic reinforcement mechanism in biopolyester.The crystallization,thermal,mechanical,barrier,migration and antibacterial properties were characterized by using solution casting technique to prepare the PHBV nanocomposites containing cellulose nanocrystal/nanosilver(CNC-Ag)hybrids and biodegradable PHBV.The results show that the CNC-Ag can act as the nucleating agents could to improve the crystallization rate and crystallinity of PHBV nanocomposites.Compared with pristine PHBV,the mechanical property of PHBV/CNC-Ag-1.7 was improved(the tensile strength and Young's Modulus were increased by97 % and 220 %,respectively),and the initial decomposition temperature(T0)was increased by45.1oC,The PHBV nanocomposites exhibited excellent antibacterial properties against E.coli and S.aureus,and the antibacterial properties were close to 100%.In addition,PHBV/CNC-Ag-0.85 has the best barrier properties in food simulants.The prepared PHBV nanocomposites are very promising for food packaging,beverage and disposable tableware.(?)Preparation and characterization of CNC-Ag with various polar groups content.The content of polar groups on the CNC-Ag nanohybrids surface was changed by controlling the preparation method of cellulose nanocrystals,introducing assistant reducing agent(AA),crosslinking agent(CA)and ultrasonic method.The microstructure,chemical structure and hydrophilicity of the hybrid materials were investigated by FE-SEM,FT-IR,UV-vis,carboxylcontent and contact angle.The results show that the CNC-Ag hybrids with high polarity(carboxyl group content was 1.21 mmol/g)can be prepared at room temperature with AA and CA by ultrasonic method.The excellent dispersion of CNC-Ag can help its application in the preparation of PHBV nanocomposites and enhance the performance.(?)Synergetic enhancement mechanism of CNC-Ag hybrids in PHBV nanocomposites.PHBV nanocomposites containing CNC-Ag nanohybrids with different polar groups were prepared by solution casting technique.PHBV nanocomposites were characterized by FE-SEM,FT-IR,UV-vis,DSC,TG and other characterization methods.The brittle fracture cross section,chemical structure,crystallization properties,thermal properties and barrier properties were analysed.The results show that CNC-Ag hybrids with different polar groups(hydroxyl and carboxyl groups)have good dispersion and biocompatibility in PHBV matrix,which helps to keep their hybridization with PHBV matrix after the spatial dispersion and adhesion performance.The CNC-Ag hybrids have strong intermolecular and intramolecular hydrogen bonding interactions with PHBV matrix to form a hydrogen-bonding network and enhance the mechanical properties of the PHBV nanocomposites.In addition,PHBV nanocomposites have a high antibacterial effect,making it a biofunctional biodegradable nanocomposite.