Ke Qing Han

Study on the Chemical Modification of Cellulose in Ionic Liquid with Maleic Anhydride

Dissolution and regeneration of cotton cellulose using ionic liquids as solvent was investigated. In this paper, modification of celluloses with maleic anhydride (MA) was carried out in ionic liquid,1-allyl-3-methylimidazolium chloride(AmimCl).The maleylation celluloses with degrees of substitution (DS) between 0.85and 1.46 were accessible in IL. The effects of reaction time, temperature and mass ratio of the MA in cellulose were investigated. These maleylation celluloses were characterized by infrared spectroscopy, thermogravimetric analysis (TGA). Experiments showed that the optimal conditions for grafting were: mass ratio of maleic anhydride and cotton cellulose 0.8; reaction time of 90 min; temperature of 80 °C.

Rheological Behaviors of Polyacrylonitrile Melt Using Ionic Liquids as a Plasticizer

The rheological behaviors of polyacrylonitrile/ionic liquids (PAN/ILs) melt were investigated to determine the general processing parameters and offer an important theoretical foundation of plasticized melt spinning. A step was carried out to decide the accurate temperature through the temperature sweep and time sweeps. The impacts of the concentration and temperature on the modulus of PAN/ILs samples were studied by dynamic sweeps. The three-parameter Carreau viscosity model was used to predict the zero-shear viscosity from the apparent viscosity data. The PAN/ILs melt showed shear-thinning behaviors. The melt with higher PAN concentration was found to be more sensitive to the temperature. However the structural viscosity index of the melt first decreased and then increased with the increase of temperature.

Structure and Performances of Plasticized Melt-Spun Polyacrylonitrile Precursor Fiber

The structure and performances of melt-spun PAN precursor fiber were studied by combination of SEM, DSC, UV and so on. The tensile strength of melt-spun PAN precursor fiber is 0.68GPa. The surface is very smooth and the cross-section is around. Due to the partially cyclized structure of melt-spun precursor fiber, the exothermic peak becomes broader with reducing intensity in compared with commercial fibers from solution-spun.

Application of Melt Extrusion Process for an In Situ Polymers Blend of Cellulose with Polyethylene Glycol in the Presence of Ionic Liquid

To modifying cellulose through an eco-friendly process, an in-situ chemical blend modification of microcrystalline cellulose with PEG2000 was conducted by using co-rotating twin-screw extruder through a reactive extrusion process in the presence of IL namely, 1-N-butyl-3-methylimidazolium chloride which, was acting as plasticizer and solvent for cellulose . The modified cellulose (cellulose/PEG) was characterized by polarization optical images (POM), FT-IR, XRD and thermogravimetric analysis. The POM and XRD confirmed that cellulose I was changed into cellulose II. The FTIR and X-ray scattering showed that the cellulose hydrogen bond was disturbed through the extrusion, and strong interactions occurred between cellulose molecules and PEG which improved the thermal stability and decreased the degree of crystallinity.

Green Process for Preparing Cellulose/Reactive Epoxy (BGE) through an In Situ Chemical Blend (Pre-Hybrid Polymer Bio-Composite)

Reactive extrusion as a green has been applied for cellulose/ Butyl Glycidyl Ether (BGE) in-situ chemical blend modification, process was conducted by using co-rotating twin-screw extruder through a reactive extrusion process in presence of IL (1-N-butyl-3-methylimidazolium chloride) which was acts as plasticizer and solvent. The blended materials (cellulose/BGE) were characterized by SEM, elemental analysis, FT-IR, XRD, and thermogravimetric analysis. The SEM showed a good compatibility between cellulose and BGE molecules. FTIR and X-ray diffraction are showed that the hydrogen bonds of cellulose was disturbed through the extrusion, and strong interactions occurred between cellulose molecules and BGE, which was an obvious effect on the thermal stability and the degree of crystallinity (decreased).

Graft Polymerization of L-Lactide onto Cellulose in Ionic Liquid via Twin Screw Extruder

A twin-screw extruder was used to carry out the ring opening graft polymerization of L-lactide onto cellulose through reactive extrusion process. Ionic liquid (1-butyl-3-methylimidazolium chloride) [Bmim]Cl and Sn(oct)2 were used as solvent and catalyst, respectively. FTIR, TGA and XRD were used to investigate the structure, thermal stability and crystalline behavior of the reaction products. The result showed a successful ring opening polymerization of L-lactide on cellulose. Furthermore, it showed a increased crystalline degree and thermal stability after being introduced the PLLA.

Application of Twin Screw Extruder in Cellulose Dissolution with Ionic Liquid

Twin-screw extruder was used as a dissolution unit for microcrystalline cellulose with ionic liquid. Ionic liquid (1-butyl-3-methylimidazolium chloride) was applied as solvent and plasticizer; it was mixed with cellulose to prepare the extrusion mixture. The extrusion mixture was feed into twin screw extruder which was run under conditions; speed 65 rpm and 1400C. In order to determine whether the cellulose I has been transformed into cellulose II, the solubility, structure, crystallinty and thermal stability of the extrude cellulose were investigated by polarizing Optical microscope, FTIR, XRD and TGA, respectively. The results which were obtained from polarizing optical microscope showed a clear cellulose solution without undissolved cellulose. FTIR confirmed the transfer cellulose I into cellulose II. XRD result showed a decrease in degree of crystallinity and confirmed the change of cellulose I into cellulose II. Finally, TGA analysis approved that the thermal stability was decreased according to the decrease in crystallinity.

Influence of Melt Temperature on Structure of Polyacrylonitrile in Ionic Liquids during Plasticized Melt Spinning Process

The carbon fiber has excellent properties; however, the high cost limited its wide application. Here we report a novel process to reduce the heat emission during stabilization by in situ modification of spinning melt. In this paper, the effect of extruding temperature on the structures of PAN in the PAN/ILs melt was investigated by twin-screw extruder. FTIR and UV-vis absorption spectra of modified samples showed the formation of C=C and C=N group, which indicated the occurrence of cyclization and dehydrogenation reactions of PAN during extrusion process. The degree of cyclization was calculated from DSC test and the degree of cyclization can be up to 24.5% with the residence time of 14 min at 210 oC, which could decrease the heat release in the subsequent stabilization process during carbon fiber production. Therefore, this method should be benefit to improve the processing efficiency during stabilization process.

Study on the Properties of Melt Spinning PAN/MWNTs Composite Fibers

Polyacrylonitrile（PAN）/multi-walled carbon nanotubes (MWNTs) composite fibers were prepared by melt spinning using ionic liquids (ILs) as a plasticizer. The effects of different MWNTs contents on the morphology, mechanical and conductive properties of the composite fibers were discussed. The results showed that property improvements have occurred with the adding of MWNTs. When the content of MWNTs reached 10%, the conductivity of PAN/MWNTs was 8.65×10-3 S/cm.

TG-FTIR Study on the Heat Treatment of Plasticized Melt-Spun PAN Precursors for Carbon Fiber

In this paper, the evolution of the gas evolved during the heat treatment of the plasticized melt-spun PAN fibers was investigated by TG-FTIR. TG, DTG and G-S (Gram-Schmidt) curves showed that there were two main decomposition stages during the heat treatment of melt-spun PAN fibers. And the results indicated that the main pyrolysis products were NH3 (966 cm-1 and 932 cm-1), HCN (713 cm-1), H2O (3650 cm-1), CH4 (1305cm-1), CO (2180 cm-1), CO2 (2360 cm-1 and 667 cm-1). The release of NH3 and HCN started at the same temperature 220 °C, which were the main products during the stabilization step. Besides, the formation mechanism of the pyrolysis products is presented in detail.