Study On Preparation And Gas Barrier Properties Of Regenerated Cellulose Composite Film

Petroleum-based polymer films have been drawing remarkable attention to packaging and protective field due to their low-cost,lightweight,versatility and good processability.However,the excessive use of such polymer material will bring about the consumption of non-renewable petroleum resources and the pollution to environment from non-degradable waste.Cellulose is the most abundant natural polymer on our planet.Cellulose nanofiber(CNF)is a kind of regenerated cellulose obtained after chemical treatment of natural cellulose,which has the advantages of low cost,renewable and biodegradable.Nevertheless,insufficient gas barrier properties of CNF greatly restricted its application in package of oxygen-sensitive commodities especially at high humidity environment.Therefore,innovative development of CNF packaging material with high gas-barrier properties is highly desirable.Over the past decades,the plate-like nanofiller blending method has been reported as a promising strategy to obtain high gas barrier nanocomposite films.Graphene oxide nanosheet(GONS)was usually blended with polymer matrix to fabricate multifunctional nanocomposite due to their high specific surface area and large aspect ratio.Graphene oxide nanosheet/cellulose nanofiber(GONS/CNF)nanocomposite films were fabricated through layer-by-layer coating and hot pressing method.However,GONS/CNF nanocomposite films exhibit hydrophilic properties due to the large number of hydrophilic groups on the CNF and GONS,resulting in an unsatisfactory water vapor barrier performance.Therefore,GONS/CNF nanocomposite films were hydrophobically modified by solution impregnation method using GN-704 waterproof and anti-corrosion nanocomposite ceramic coating,H-mCNF and H-mGONS/CNF composite film were obtained.XRD results showed that GONS was completely exfoliated and well dispersed in CNF matrix.The images of SEM and GI-WAXS manifested that the exfoliated GONS was highly oriented along the film direction under a strong external shear flow field.Such unique structure endows GONS/CNF nanocomposites with ultrahigh oxygen barrier property.With only 3.66 vol%GONS,the oxygen permeability coefficient of CNF film decreased by about 4×104 times,from 5.5×10-13 to 1.4×10-17 cm3 cm·cm-2s-1Pa-1.Pa-1.Meanwhile,the tensile strength and Young's modulus of the CNF film were respectively enhanced by 2 and 57 times.Furthermore,the thermal stability of CNF film was also improved with the incorporation of GONS.SEM results showed that a micron-scale rough structure composed of spherical inorganic oxide particles was formed on the surface of CNF and its composite films by solution impregnation.The rough structure transforms the surface of CNF and its composite film from hydrophilic to hydrophobic,and the water contact angle of CNF film was significantly increased from 0°to above 140°.After hydrophobic modification,the water vapor barrier property of CNF and its composite film was improved due to the increase of water contact angle and the decrease of permeable water vapor molecules.The water vapor permeability coefficient of CNF film decreased from 1.61×0-12 to 1.41×10-12 g cm cm-2 s-1 Pa-1.In addition,after hydrophobic modification,H-mCNF film has good antifouling and self-cleaning properties.