Research Of Wood Cellulose Modified Carbon Nanotubes Reinforced Cellulose Matrix Composites

In recent years,the consumption of non-renewable resources such as natural gas,petroleum,and coal has been severe,and environmental problems such as atmospheric pollution and global warming caused by the consumption of various fossil resources have also become increasingly prominent.Cellulose,a biomass resource,has many advantages,such as wide source,environmental protection,and renewable,and it has received more and more attention.Since the discovery of carbon nanotubes,due to its peculiar structure and numerous excellent properties,it has made great progress in the fields of physics,biology,materials,and chemistry.Wood cellulose?WDC?hybridized multi-walled carbon nanotubes?MWCNTs?composites?MWCNTs-WDC?were synthesized by covalently grafting WDC onto MWCNTs in ionic liquid 1-allyl-3-methylimidazolium chloride?AmimCl?.Then,the MWCNTs-WDC/WDC composites were prepared in AmimCl.the reactivity of the natural polymer WDC is poor because of the large proportion of intra-and intermolecular hydrogen bonds,high molecular weight and high degree of order.The reactivity of MWCNTs is poor too,because of the high degree of order and high chemical stability.It result in more difficulty to bond covalently between MWCNTs and WDC.What's worse,the property of MWCNTs composites is always not satisfied,due to the van der Waals interactions of MWCNTs,MWCNTs process aggregation in solvent and matrix.In this study,these problems were all solved.The mechanical and electrical properties of MWCNTs/WDC composites were enhanced significantly,by facilitating the dispersion of MWCNTs in WDC matrix.The conclusions were summarized as below:1.The natural polymer WDC dissolved effectively in AmimCl,the hydrogen bonds in WDC was decreased,the reactivity of WDC was improved owe to more hydroxy exposed.Then,WDC grafted onto the MWCNTs bearing acyl chlorides via esterification reaction using an ionic liquid AmimCl as a solvent.The results revealed that WDC successfully grafted onto the MWCNTs via esterification reaction in AmimCl.MWCNTs-WDC were synthesized.The stability of MWCNTs-LNC dispersion was superior to the MWCNTs in AmimCl.The enhanced dispersion stability of MWCNTs in AmimCl after covalently grafting WDC onto their surfaces could be explained as following:WDC can effectively dissolve in AmimCl,and covalently grafting along the surface of MWCNTs.The van der Waals interactions between the side walls of MWCNTs were obstructed.2.The MWCNTs-WDC/WDC films,WDC films and MWCNTs/WDC films were prepared in AmimCl.The optimal reaction time was 2 hours and the optimal reaction temperature was 70°C.The results revealed that the WDC grafted covalently onto the surface of MWCNTs facilitated the dispersion of MWCNTs in WDC matrix.The elongation at break and tensile strength of MWCNTs-WDC/WDC films with 3 wt%of MWCNTs content were 12.2%and 106.7 MPa respectively,which was almost 93.7%and10.7%higher than those of the pristine MWCNTs/WDC films.3.The MWCNTs-WDC/WDC fibers,MWCNTs/WDC fibers and WDC fibers were fabricated in AmimCl.The results revealed that the WDC grafting onto the surface of MWCNTs facilitated the dispersion of MWCNTs in the WDC matrix.The tensile strength of MWCNTs/WDC fibers was up to approximately 203.4 MPa with 6 wt%MWCNTs.Comparably,the tensile strength of the MWCNTs-WDC/WDC fibers composite increased to 304.6 MPa with 10 wt%MWCNTs,which was almost 106.8%higher than that of MWCNTs/WDC fibers with the same amount of MWCNTs.Meanwhile,it was 117.1%higher than that of WDC fibers.The highest electrical conductivity of MWCNTs/WDC fiber was up to 8.0×10^-3 s/cm with 6 wt%MWCNTs containing.While the highest electrical conductivity of MWCNTs-WDC/WDC composite fibers promoted to 1.3×10^-1s/cm with 10 wt%MWCNTs,which was almost 108 times higher than that of MWCNTs/WDC fibers with the same amount of MWCNTs.It was 16.25 times higher than the highest electrical conductivity of MWCNTs/WDC fibers.4.The WDC fibers were subjected to high-temperature carbonization to prepare WDC conductive fibers.The results showed that with the increase of carbonization temperature,the morphology of carbonization cellulose gradually became spherical,and the degree of graphitization of WDC conductive fibers gradually increased;at the carbonization temperature of 800°C,the conductivity of conductive fibers was 7.6 s/cm;the conductivity of the conductive fiber was 27.2 s/cm at a carbonization temperature of 1000°C.5.The WDC conductive fibers and MWCNTs-WDC/WDC composites conductive fibers were prepared at a carbonization temperature of 1000°C.The results revealed that the MWCNTs played a role of conductive bridge between carbonization cellulose blocks.What's more,MWCNTs acted as a template for cellulose graphitization,changing the morphology of the carbonization cellulose from microspheres to sheets while improving the degree of graphitization of cellulose.The sheet form possessed more percolation between building blocks compared to the microspheres,which was good for electronic transmission.These all contributed to the improvement of conductivity of the fiber.The mean conductivity of the MWCNTs-WDC/WDC composites conductive fiber was 105s/cm.It had a good electrochemical properties.