Study Of CNCs Surface Chemical Modification And Its Enhancing Behavior For Epoxy Resins

Cellulose nanocrystals(CNCs)are very important materials containing active hydroxyl groups which can be easily modified with other functional groups by ester-formation,ether-formation,etc.CNCs can improve the thermal and adhesive properties of epoxy resin.In these days it has become an interesting topic to enhance thermosetting resins by CNCs fillers instead of traditional petroleum-based additives.It’s important to understand the interactions of CNCs with other materials at a micro level.Therefore,this study discusses the surface modification of cellulose nanocrystals with different monomers to improve the dispersion in epoxy matrix and thermal stability.Modified cellulose nanocrystals(MCNCs)were added into the epoxy resins as fillers to enhanced the mechanical and thermal properties of the composites.In chapter 2 of the thesis,we synthesized the cellulose nanocrystals(CNCs)by using cotton as a raw material,then it was modified with 2-carboxyethyl acrylate to improve its dispersion in epoxy resin.Scanning electronic microscopy(SEM),transmission electron microscopy(TEM),X-ray’s powder diffraction(XRD),thermal gravimetric analysis(TGA and DTG)and Fourier transform infrared spectroscopy(FTIR)techniques were used to differentiate between the synthesized native CNCs(NCNCs)and modified CNCs(MCNCs).The result showed that MCNCs with epoxy resin gives an excellent shear strength and shear modulus.MCNCs enhanced E-51 epoxy system achieved high shear strength 15.1(MPa)at 5 wt%.In chapter 3,CNCs was modified with KH-560.The successful modi fication of CNCs(MCNCs)was characterized by Fourier infrared transformed spectroscopy.The characteristics peaks appeared at 880 cm-1 and 1028 cm-1 were assigned to C-H bending and Si-O-C bending vibration.MCNCs possess the unique properties of high mechanical strength and a crystalline nature.While on the other hand CaSO4 fillers is a typical high strength material widely used as the reinforcing agent.So,we added both MCNCs and CaSO4 fillers in E-51 epoxy resin via sonication technique making a strong relation to enhance the adhesive properties.The surface morphology,size and shape of MCNCs were examined by atomic force microscope(AFM),scanning electron microscope(SEM)and transmission electron microscope(TEM).The thermal stability of the composites was investigated by thermal gravimetric analysis(TGA),X-ray powder diffraction(XRD).We found that MCNCs and native CaSO4(1:1 ratio)had an obvious enhancement effect on shear strength at 3 wt%18.6(MPa),cured with triethylenetetramine,showed remarkable improvement.In chapter 4,Firstly,we synthesized the bio-based epoxy resin containing silicone-bridged difunctional epoxy monomer(SIEEP2).It is derived from naturally occurring eugenol epoxy in high yield by introducing the methylsiloxane linker into its molecular backbone.The epoxy ring can be observed at a chemical shift of 2.4-3.2 ppm in the 1H NMR spectra and 45-50 ppm in the 13C NMR spectra.The hydrosilylation reactions of eugenol epoxy and silicone linker was carried out without formation by side reaction.Furthermore,mass spectroscopy analysis calculated the same molecular mass confirmed the synthesis being.Mass spectroscopy analysis report with molecular mass 574.4(597.4-23,minus the weight of Na-),confirms the synthesis of bio-based epoxy,which is in accordance with the values of their expected molecular structure.Native CNCs was firstly modified by eugenol-based silane coupling agent(EBSCA)which was synthesized via hydrosilylation process.The MCNCs added into the bio-based epoxy to enhance the adhesive properties.The scanning electron microscopy(SEM)shows that MCNCs is uniformly dispersed in the bio-based epoxy resin at low ratios,but agglomerations will be formed at higher ratios.The presence of MCNCs has been greatly improved and enhanced the bonding performance of bio-based epoxy resin in the interface area.The most promising result is that the adhesive property of the shear strength of MCNCs increases by 3 wt%17.5(MPa).Enhancing the bio-based epoxy adhesive properties by MCNCs have broad application prospects in environmental applications.This suggests that the widespread use of bio-based MCNCs in environmental engineering applications is feasible,especially in terms of adhesives properties.In chapter 5.The modified cellulose nanocrystals(MCNCs)was added with different resins(E-51 epoxy resins,liquid phenolic,and acrylic)system,and was investigated for thermal stability and adhesive property.Scanning electronic microscopy(SEM),X-ray’s diffraction(XRD),Thermogravimetric analysis(TGA)and Fourier transform infrared spectroscopy(FTIR)were used to characterize the structure and investigate different properties of the composites.Comparing with the native CNCs,the MCNCs can enhance the shear strength of the 1 wt%of E-51 epoxy resin 13.6(MPa),acrylic resin 7.9(MPa)and liquid phenolic resin 9.9(MPa)composites due to the epoxy group of eugenol-based silane coupling agent.In chapter 6.The investigation was made to study the CNCs surface modification with succinic anhydride to enhance epoxy resin(E-51)performance for adhesive property.Scanning electronic microscopy(SEM),X-Ray diffraction(XRD),and Fourier transform infrared spectroscopy(FTIR)were used to characterized the structure and investigate the different properties of MCNCs.The shear strength and shear modulus showed good result of MCNCs epoxy composites.The maximum value was observed of MCNCs for shear strength for 3 wt%13.9(MPa).Cellulose nanocrystals can also be used for different applications such as dye adsorption.The aim is to introduce bio-sorbent for the removal of toxic cationic golden yellow X-GL dye.The MCNCs showed better adsorption than native CNCs because of the-COOH group.Its low cost,biodegradability,and non-toxicity to the environment,modified cellulose nanocrystals have potential application value in the field of biosorption.