Preparation Of Nano-cellulose Whiskers Using Copper Sulphate As Cotatalyst And Its Reinforcement Application In Waterborne Polyurethane

Cellulose is the most abundant biodegradable natural biopolymer in the world. With thefuture shortage of crude oil resource and people's increasing emphasis on environmentalprotection, it is very important to develop new fine chemical products of cellulose withsuperior performance. They are obtained by reassembly and modification of cellulosemolecules and whiskers in microscopic field.There are three kinds of nano-cellulose according to the shape and topography, sphericalnano-cellulose, nano-cellulose whisker and fibrous nano-cellulose fiber. The length and thediameter of nano-cellulose whisker(NCW) are 10～1000nm and 5～20nm reapectively, theratio of length to cross diameter (L/d) is 5～100. NCW has high crystallinity, excellenthydrophilicity, high strength, unique fluid properties and mechanical behavior. It can be usedas the reinforcing agent in environmental-friendly nano-composites due to its specialbiocompatibilityand biodegradability.It has been reported that some metallic ion such as Fe 2?,Fe 3?,Ca 2?,Cu 2?canaccelerate the cellulose hydrolysis process of cellulose. Recently there is no report aboutmodification of preparation of NCW by using metallic ion as cocatalyst. In our research,copper sulfate was chosed to be used as cocatalyst in the hydrolysis process of cellulose toprepare NCW. The first-order reaction hydrolysis kinetics was calculated based on therelationship between the content of glucose and time. The reaction constant of the reaction ofcellulose hydrolysis before and after the adding copper sulfate were k1=0.0937 and k2=0.9000,respectively. k2 is almost ten times of k1, which showes that copper sulfate can accelerate thecellulose hydrolysis effectively.The effect of temperature, reaction time, amount of copper sulfate and the ultrasonicdispersion time on the hydrolysis and the NCW properties were studied. And the optimalreaction condition was obtained, which was that the temperature was 50℃, the reaction timewas 120min, the amount of CuSO4 is m(CuSO4)/m(cellulose)=1%, the ultrasonic dispersiontime was 20min. The yield of NCW was as high as 58%. The ratio of L/d was 20～50. TheAFM topography showed that the peak of NCW film was 27.95nm.The results proved thatwhen the reaction time was shortened, the yield was increased. And the structure andproperties of the nano-cellulose whiskers were modified when copper sulphate was used ascocatalyst. Nanocomposite of WPU/NCW with high tensile strength was prepared by using NCW asthe reinforcement agent and waterborne polyurethane(WPU) as matrix. The structure,topography and mechanical properties of WPU/NCW composite were tested and analysised.The results showed that NCW could be dispersed well in WPU and appropriate amount ofNCW could modify the mechanical properties of WPU. The elongation at break and strengthof stress of the nanocomposite of NCW/WPU were increased by 28.82% and 15.06% ,respectively, when the ratio of NCW andWPU was 0.8%.