| Liquefaction technology was used to transform banana pseudostem(BPs)into liquid products(LBP),which are rich in reactive hydroxy groups.LBP was employed as a platform material to fabricate biodegradable films.Based on green solvent,liquefied residue(LR)was utilized to prepare high-value chemicals,such as cellulose and carbon dots.Thus,comprehensive utilization of BPs waste was realized.Main works and conclusions drawed in this paper are as follows:Firstly,the chemical compositions of BPs were analyzed.The three major components of BPs,namely,cellulose,hemicellulose,and lignin were extracted and separately liquefied.In the process of liquefaction,content changes of the three components in liquefied residues of BPs were also tracked.The dynamic and thermodynamic equations were established to eatimate kinetic parameters of each component and to understand the liquefaction behavior of BPs.Results show that activation energies of the three components are in the order of cellulose>lignin>hemicellulose.Multiple reactions coexist in heterogeneous liquefaction process.The liquefied BPs product(LBP)with wide molecular weight distribution,which contains abundant functional groups,such as hydroxyl group and aromatic ring,is the degradation product of carbohydrate and lignin.When liquefaction of BPs performed in the condition that liquid ratio of 5:1,catalyst amount of 1 mg/g BPs,reaction temperature of 150?,and the reaction time of 90 min,cellulose content in LR was as high as 85.21%.Taking LBP with hydroxyl value of 246.52 mg KOH/g as plasticizer,modifacation of biocomposite film in two-and three-dimensional spatial structure was carried out.The addition of silica sol in the substrate and growing of OTS on the surface endowed PVAc composite film with hydrophobic properties,its tensile strength and elongation at break were highly improved by 425.79%and 250.81%,respectively.With carrageene-polyvinyl alcohol copolymer(CG-PVA)as the film substrate,potassium ion(K+)was introduced to promote the coil-helix transformation of macromolecular chains.The pyrolysis kinetics of CG-PVA/LBP/K films was analyzed in detail by combining model-free,model-fitting methods and the pseudo-component model method.It was the compact membrane network designed that enhanced the mechanical and thermal properties of biocomposite films prepared Immersion tests showed that those composite films were degradable.Acting as an initiator,LBP reacted with ?-caprolactone by ring opening polymerization.When weight ratio of ?-caprolactone and LBP is 9:1,molecular weight of the synthetic poly(caprolactone)polyols is 14251.Acting as crosslinker,LBP polymerized with HDI to produce hard chain segment,which subsequently grafted with artifical or commercial polycaprolactone polyols with two different molecular weights to introduce soft chain segment,poly(?-caprolactone)-based polyurethanes(LPU/PUPCL)were synthesized by two step polymerization.FT-IR,13C NMR,GPC and other characterization methods were applied to track the progressive chain expansion.Tensile tests,DMA,TG and DSC analysis showed that the composite film with high elastic state and good thermal stability had the highest tensile strength of 37.24 MPa and the highest flexible elongation rate of 638.83%.In addition,LPU/PUPCL films had excellent ultraviolet absorption performance.Taking liquefied residue which possessed the highest cellulose content as raw material,cellulose nanofibers and nanocrystals were successfully extracted by TEMPO oxidation and acid decomposition,respectively The average length of CNF was 332.3 nm and the average diameter was 5.9 nm.The average length of CNC was 93.3 nm and the average diameter was 3.5 nm.Carbon dots(CDs)with high yield and high fluorescence intensity were prepared by hydrothermal carbonation of residue cellulose with acidic ionic liquid(SO3H-IL)and PEG novely added.The CDs particle size distribution was 1-4.6 nm,and it had strong stability.Cr(VI)can be selectively detected by the prepared CDs. |
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