Study On The Effects Of Different Chain Length Fatty Acids On Solid Phase Esterification Of Cellulose And Properties Of The Products

In recent years,natural cellulose used as a kind of almost inexhaustible renewable raw material to prepare long chain cellulose esters(LCCEs)has attracted worldwide attentions on this research.But the researches show that the esterification of cellulose is gradually difficult with the increase of carbon chain length of fatty acids in the synthesis process of LCCEs.Therefore,based on our previous research of preparing LCCEs by mechanical activation(MA)-strengthened solid phase reaction(MASPR)with co-reagent,this paper further studied the influence of different chain length fatty acids on solid phase esterification of cellulose and properties of the products.The main research contents and results are as follows:LCCE was produced by MASPR with microcrystalline cellulose(MCC)as the raw material,palmitic acid as long chain esterifying agent,acetic anhydride as co-reagent,and concentrated sulfuric acid as catalyst.The effects of pre-reaction time,pre-reaction temperature,esterification reaction temperature,esterification reaction time,reactants molar ratio,and catalyst dosage,etc.were investigated respectively by using bound acid content(A)of the products as evaluating index.The results indicated that under the optimum conditions of pre-reaction time 60min,pre-reaction temperature 80 C,esterification reaction temperature 80?,esterification reaction time 120min,reactants molar ratio of 1:3:6(cellulose/palmitic acid/acetic anhydride),and catalyst dosage 0.2mL,A of the product reached 0.0108mol·g-1.In addition,the products were characterized by SEM,FTIR and XRD.According to the above mentioned optimum conditions,octanoic acid,lauric acid and palmitic acid were used as long chain esterifying agents to prepare cellulose octanoate-aceate,cellulose laurate-aceate and cellulose palmitate-aceate with different reaction time.The DS of the products were analyzed by 1H-NMR and 13C-NMR for exploring the influence of different chain length fatty acids on the reaction activity between cellulose and esterifying agents in the solid phase esterification.The results showed that the esterification of cellulose was easier with the shorter carbon chain fatty acid.On the contrary,the longer the carbon chain,the more difficult for the esterification of cellulose.The functional groups,granule morphology,crystal structure and thermal performance of the different chain length cellulose esters with different reaction time were characterized by FTIR,SEM,XRD,DSC,and TGA,respectively.The results showed that the infrared spectra of all the cellulose esters appeared a new absorption peak at about 1740 cm-1,indicating that cellulose was successfully esterified.The longer the carbon chain of fatty acid,the bigger the particles and the stronger the surface of its corresponding cellulose ester.The crystal stucture of cellulose had great changes after esterification as its original cellulose I crystalline stucture was destroyed and transformed to new crystal type and structure,and the diffraction peaks weakened with the increase in carbon chain length of fatty acids and strengthened with increasing DS of the products.DSC results showed that the three kinds of cellulose esters had a glass-transition in the range of 0?80?,which was clearer with the increase in chain length of fatty acids,and the glass-transition temperature(Tg)reduced with increasing DS of the products.Affected by the steric hindrance of the substituent side chain,the thermostability of products improved with the increase in chain length of fatty acids,and the thermostability of cellulose esters was cellulose octanoate<cellulose laurate<cellulose palmitate.