Preparation And Research On Properties Of Hybrid Materials Based On Cellulose Microcrystal From Sisal Fiber/Octa-aminopropyl Sisesquioxane

Cellulose microcrystal is an abundant renewable resource, which is used in the reinforcementof polymer composites. As a reinforcement material, cellulose microcrystal has theadvantages of high modulus, low density and good compatibility with polymer matrix.However, cellulose microcrystal from sisal fiber （SFCM） as plant fiber, has the disadvantageof poor heat resistance, which limits its application. In this paper, we extracted cellulosemicrocrystal from sisal fiber and prepared cellulose nanocrystal （SFCN）. Then two kinds ofocta-aminopropylsisesquioxane （POSS-NH₂） with good heat resistance were synthesized andPOSS-NH₂grafted SFCM hybrids composites were prepared by cross-linking reaction. Theeffects of the structure and morphology of POSS-NH₂on the surface morphology and thermalproperties of the POSS-NH₂grafted SFCM hybrids were studied.Cellulose microcrystal from sisal fibers （SFCM） was extracted by means of chemicalprocedures such as alkaline extraction and acid hydrolysis. Then cellulose nanocrystal （SFCN）was prepared by the acid hydrolysis of SFCM. The final SFCM and SFCN were characterizedby Thermogravimetric Analysis （TGA）, Infrared Spectroscopy （FTIR）, X-Ray Diffraction（XRD）, Differential Scanning Calorimetry （DSC）, Optical Microscopy, Scanning ElectronicMicroscopy （SEM） and Field Emission Scanning Electronic Microscopy （FESEM）. Theresults proved that the obtained SFCM with diameters of10μm and lengths of50¹50μm andSFCN were present in the form of cellulose I. In the DSC thermogram for cellulosemicrocrystal a sharp endothermic peak at323.7oC could be seen. The result of ThermalGravimetric Analysis showed that it had a sharp weight loss starting at337oC higher thansisal fibers starting at275oC and was almost completely pyrolyzed at700oC with a residualmass of0.05wt%. The results of SFCN indicated that SFCN had higher degree of crystallinitybut lower thermal property.Two kinds of Octa-aminopropylsisesquioxane （POSS-NH₂） were synthesized by using ofγ-aminopropyltriethyoxysilane in Tetrahydrofuran （THF） and methyl alcohol （MeOH）,respectively. We called them POSS-NH₂（THF） and POSS-NH₂（MeOH）. The final productswere characterized by means of FTIR, XRD, TG, AFM and Zeta nasosize Analyzer. Theresults proved that the structure of POSS-NH₂（MeOH） was more regular than that ofPOSS-NH₂（THF）. Besides, POSS-NH₂（MeOH） had smaller and monodispersive diameter.The results of TG indicated that POSS-NH₂（THF） and POSS-NH₂（MeOH） stoppeddecomposing at522oC and512oC with a residual mass of56.57wt%and55.48wt%at700oC,respectively. POSS-NH₂（THF） and POSS-NH₂（MeOH） had good heat resistance. POSS-NH₂（THF） and POSS-NH₂（MeOH） grafted SFCM hybrids composites weresynthesized by cross-linking graft reaction, respectively. We called them CP-THF andCP-MeOH. Epoxy chloropropane as cross-linking agent was used in the graft reaction. Thechemical and surface structures and thermal properties of the POSS-NH₂grafted SFCMhybrids were characterized with FTIR, FESEM, XRD, TG and DSC. The results indicatedthat the surface of POSS-NH₂grafted SFCM hybrids were damaged possiblely due to thetreatment of alkaline during cross-linking reaction. Meanwhile, the degree of crystallinity wasslightly decreased resulting from the crystalline regin of SFCM having taken place in reactionwith POSS-NH₂（THF） and POSS-NH₂（MeOH）. The results of TG and DSC proved thatCP-THF and CP-MeOH had sharp weight loss starting at341.6oC and342.3oC higher thanSFCM starting at326.1oC and they stopped pyrolyzing at383.9oC and375.5oC higher thanSFCM stopping at347.9oC. The residual mass of CP-THF and CP-MeOH were15.59wt%and6.23wt%at700oC respectively, which were also increased. The thermal properties ofCP-THF and CP-MeOH were improved.