| This work was to prepare the high aspect ratios (length/diameter) nano cellulose extractedfrom poplar and cotton with mechanochemistry treatment. There are three methods to preparenano cellulose/PVA composite: Mixture of mixing method; Freeze drying casting method and theFilm immersion method, among them, the last method is the best. Successful preparation of suchbio-based composites could open up ways to new applications in e.g. medicine, bio-packaging orhorticulture. The nano cellulose and composite films were characterized with scanning electronmicroscope (SEM), fourier transform infrared spectrometry (FTIR), ultraviolet-visible spectra(UV-vis), tensile testing machine, thermo mechanical analysis(TMA) and constant temperatureand humidity incubator. Test results are as follows:1,SEM showed the diameter of the cellulose was mainly range between30~100nm and highaspect ratio was mainly range between1000～4000. Observe the composite film tensile fractureswith film immersion method, the nano cellulose film and PVA were mutual blend, touchedclosely, and the fracture present dimple that suggested nano cellulose film had very good enhanceeffect on PVA.2,FTIR indicated after poplar and cotton through the sodium chlorate treatment, the peaksrepresented of lignin become weak and also the peak of hemicellulose after potassium hydroxidetreatment. After the hydrochloric acid treatment, representatives the peak represented of celluloseincreased. To sum up, after mechanochemistry treatment, this work successfully extractedcellulose from poplar and cotton. FTIR indicated the interaction between nano cellulose andmatrix is physical rather than chemical in origin.3,UV-vis showed that with the thickness of nano cellulose film increased, no matter thevisible light or uv light transmittance, they were all decreased. Among them, the cotton was betterthan the poplar, this is because poplar contained more nano cellulose fiber that bigger than200nm. The light transmittance of composite film also decreased with the content of celluloseincreased.4,The mechanical properties of PVA were improved significantly and the two plantnanofibers had the similarly reinforcing effects in the matrix. The mechanical properties of nanocellulose film were wonderful, tensile strength was reached up to101.79MPa, and elasticmodulus was reached up to5741MPa. When the thickness of nano cellulose film was0.03mm,the mechanical properties reached the best, improved the elastic modulus of poly (vinyl alcohol)200%.5,TMA suggested that the thermal expansion coefficient of nano cellulose was extremelylow. When added them to the PVA, there can be made of ideal composite film with low thermalexpansion coefficient, and thermal stability of composite material was increased with the content of nano cellulose slightly increased.6,Biological degradation test showed that nano cellulose/PVA composite film wasbiodegradable. With the content of nano cellulose increased, the degradation property becomebetter. This composite film was environment friendly enhanced material.In conclusion, cellulose nanofibers as a future resource have tremendous potential since theyare one of the most abundant organic resources on the earth. The potential applications ofcellulose nanofbers are as thickeners in food products, as strengthening agents for packagingmaterials, as barrier coatings, and in lightweight and strong polymer nanocomposites. |
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