Study On Application Of Esterification Modification Of Hemicellulose And Its Hyperbranched Polymer

Hemicellulose is a kind of compound polysaccharide polymerized from many kinds of monosaccharides,which has excellent biocompatibility,high functionality and high chemical activity et.al.The application of hemicellulose can be expanded by chemical modification,including esterification,etherification or sulfonation,which can be used to prepare sweeteners,plasticizers,surfactants,anticoagulants or specific targeted drugs and other medical preparations.It is of great significance to modification and study the functionalization of hemicellulose.In this paper,the synthesis of hemicellulose modified by esterification and hyperbranched polymer and its application on dispersion of color paste,microencapsulation of flame retardant and dye adsorption were studied.Hemicellulose was esterified by maleic anhydride to obtain hemicellulose maleate HCMA with a large amount of carboxylic at the end.The effect of reaction conditions on the degree of substitution of HCMA were discussed and the best preparation condition was determined.The maximum degree of substitution of HCMA was reached to 0.97.The structure and properties of HCMA were characterized by FT-IR,¹³C-NMR and TG.The results show that in the process of HCMA synthesis,there were obvious change of-COOH and-C=C-absorption peak intensity in FT-IR and ¹³C-NMR spectra.Compared with hemicellulose,the carboxyl group at the end of HCMA and more branched chain structure had greater influence on the thermal decomposition temperature,so it had better thermal stability.Carbon black slurry was prepared with HCMA as dispersant.The effect of content of HCMA on the centrifugal stability,temperature stability and storage stability of carbon black slurry were studied.When the content HCMA was 10%,the centrifugal stability,temperature stability and storage stability of carbon black slurry were the best.The properties of carbon black slurry were characterized by SEM.The results show that carbon black slurry was prepared with HCMA showed better homogeneity,smaller particle size and excellent stability.Dyeing of viscose staple fiber with carbon black slurry:the effect of content of carbon black pulp on the dry breaking strength,wet breaking strength,dry breaking elongation,dry strength change index and whiteness of black staple viscose fiber were investigated.The results show that when the addition of carbon black slurry was 4%,the performance of black staple viscose fiber was the best.Flame retardant microcapsules（MDPS）were prepared by in situ polymerization from HCMA,urea,formaldehyde and DPS.The effect of reaction conditions on the embedding rate and particle size of MDPS were investigated.The optimal preparation condition was determined.The particle size of MDPS was 33μm,and the highest embedding rate was reached to 66.7%.The structure and properties of MDPS were characterized by FT-IR,EM,SEM,EDS and TG.The results show that the absorption peak intensity of-C=O,-C=C-and-NH changed obviously in FT-IR spectrum.The higher the embedding rate was,the more obvious the change of these absorption peaks would be.MDPS had obvious core and shell structure,and showed good dispersion;the surface of MDPS was relatively rough,and with a certain number of particles.The peaks of C,N,O were significantly enhanced and peak of P was significantly declined in EDS spectra.With the increasing of embedding rate,the thermal stability of MDPS increased first and then decreased.When the embedding rate was 60.9%,the thermal stability of MDPS was the best.MDPS was used in the flame-retardant modification of fiber membrane.The flame-retardant performance of the modified fiber membrane was tested by limit oxygen index and vertical combustion tester.The change of the flame-retardant performance of the modified fiber membrane with the addition of MDPS were studied.The results showed that when the addition of MDPS was 15%,the flame-retardant of modified fiber membrane showed excellent flame-retardant effect.The LOI increased to 29.1%,and the UL-94 reached to V-0 grade.The 1-2-generation hemicellulose hyperbranched polymer HPP with precision structure and a large number of hydroxyl and carboxyl groups at the end was obtained by the step-by-step esterification of dihydroxymethylpropionic acid and HCMA.The effect of reaction conditions on the degree of substitution of HPP were investigated,and the best preparation condition was determined.The maximum degree of substitution of HPP1 and HPP2 were reached to 0.89 and 0.83 respectively.The structure and properties of HPP were characterized by FT-IR,¹³C-NMR,rotational viscometer and TG.The results showed that the absorption peak intensity of-COOH,-OH,-COO and-CH₃changed obviously in FT-IR and ¹³C-NMR spectra.Because dimethylolpropionic acid was continuously grafted into the molecular structure of HCMA,there were a large number of branched chain structures in the molecular structure of HPP,and the number of carboxyl,hydroxyl and other groups at the end was also increasing.Compared with HCMA,the viscosity of HPP was increasing with the increasing of algebra.Compared with HCMA,HPP molecular structure contained linear unit of branched ester structure,which could be cross-linked to form network structure,so it had better thermal stability.With the increasing of algebra,the thermal stability of HPP was gradually increasing.HPP2 as adsorbent,the adsorption of HPP2 on methyl red,bromocresol green and bromophenol blue were studied.To explore the influence of adsorption condition on the adsorption capacity of HPP2 and determine the use condition of HPP2 with best adsorption capacity.The adsorption capacity were reached to 810 mg/g,680 mg/g and 905mg/g,respectively.The adsorption mechanism of HPP2 were characterized by UV-vis and BET specific surface area tester.The results show that the adsorption kinetics of HPP2was in accordance with pseudo second order kinetics equation,the adsorption thermodynamics was in accordance with Langmuir model,which was a endothermic process,and the diffusion mode were including internal diffusion mode and membrane diffusion mode,in which internal diffusion was the main mode.The desorption rate of HPP2 was over 80%under high relative pressure.HPP2 could be successfully regenerated and reused for N₂adsorption.