Wentan Ren

Hydrophobicity Enhancement of Cellulose-Based Material via Heterogeneous Surface Acetylation

Heterogeneous cotton fibre surface acetylation with acetic anhydride was performed in an oil bath at 130 °C with Na2CO3 as a catalyst to enhance the reaction activity. The effect of reaction time on fibre acetylation was characterised by the ester content of acetylated fibres, attenuated total reflectance-Fourier transform infrared spectrometry (ATR-FTIR), x-ray diffraction (XRD), static and dynamic contact angle measurements and field emission scanning electron microscopy (FESEM). The ester content increased with increasing reaction time, and the increase of ester content was not evident at a reaction time over 90 min. The emergence and intensity of the absorption peak characteristic of C=O and the reduction of the absorption peak of O-H clearly proved the occurrence of acetylation. The XRD data of the fibres exhibited the typical XRD pattern of cellulose I, and the diffracted intensity decreased after acetylation. Static and dynamic contact angle measurements demonstrated enhanced hydrophobicity and decreased surface energy with increasing reaction time. FESEM micrographs showed that the acetylation removed the wax layer of fibres and smoothed the fibre surfaces.

The grafting reaction of epoxidized natural rubber with carboxyl ionic liquids and the ionic conductivity of solid electrolyte composites

A novel hybrid material was prepared via a grafting reaction of 50% epoxidized natural rubber (ENR 50) with 1-carboxymethyl-3-methylimidazoliumbis(trifluoromethylsulfonate)imine ([(HOOC)C1C1Im][NTf2]). The grafting reaction and cross-linked structure of the hybrid material were investigated using attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy, differential scanning calorimetry (DSC) and the equilibrium swelling method. The analysis results indicated that the carboxyl group of [(HOOC)C1C1Im][NTf2] can react with the epoxy group of ENR 50 to generate an ENR 50–[(HOOC)C1C1Im][NTf2] graft polymer under conditions of 40 °C for 24 h. Furthermore, the grafting of ENR 50 formed ionic clusters and led to ionic crosslinking. In addition, ENR 50/[(HOOC)C1C1Im][NTf2]/LiTFSI electrolyte composites were prepared through introducing bis(trifluoromethanesulfon)imide lithium salt (LiTFSI) into the ENR 50/[(HOOC)C1C1Im][NTf2] hybrid system and the ionic conductivity of these electrolyte composites were studied. The results showed that the electrolyte composites have high ionic conductivity and reached a maximum ionic conductivity of 3.01 × 10−4 S cm−1 (23 °C) in the experimental range.

Improved Ionic Conductivity of NBR/Epoxy Resin/LiClO4 Composites by Adding Ionic Liquid

Solid polymer electrolyte with high ionic conductivity was prepared by adding an ionic liquid, 1-butyl-3-methylimidazolium trifluoromethanesulfonate (BMIMOTF) to the nitrile butadiene rubber/epoxy resin/LiClO4 (NBR-EP-Li) system. The addition of BMIMOTF into NBR-EP-Li composites, with the LiClO4/BMIMOTF mole ratio of 1/0.54, improved the conductivity by 6–17 times depending on the amount of LiClO4. Infrared difference spectroscopy and nuclear magnetic resonance spectroscopy analysis confirmed the interaction between LiClO4 and BMIMOTF, which caused a decreasing interaction between ClO4 − and Li+. X-ray diffraction and field emission scanning electron microscopy analysis indicated BMIMOTF improved the dissolution of LiClO4 and contributed to the increase of conductivity by an increase of free Li+.

Preparation and properties of a water-swelling rubber by in situ formed lithium acrylate in nitrile rubber

Lithium acrylate (LiAA) was in situ prepared in nitrile rubber (NBR) through neutralization of lithium hydroxide (LiOH) and acrylic acid (AA) during mixing. The NBR/LiAA compounds were vulcanized with dicumyl peroxide (DCP). The in situ preparation and polymerization of LiAA were characterized using Fourier transform infrared (FTIR) spectrometer. The micrographs of the compounds and vulcanizates were explored using a scanning electron microscope (SEM). The effects of DCP and LiAA contents on the water-swelling and mechanical properties of the vulcanizates were studied. The relationship between the LiOH/AA molar ratio and the properties of the vulcanizates was investigated. The results showed that the in situ formed LiAA could improve the mechanical properties and water–swelling properties of the NBR/LiAA vulcanizates. The vulcanizates properly compounded had high water-swelling ratio over 800% and tensile strength more than 12MPa. The differential scanning calorimetry (DSC) measurements indicated that the water absorbed in the vulcanizate existed in PLiAA and NBR networks in three different physical states, namely, free water, freezable bound water and non-freezable bound water.

Grafting modification of epoxidized natural rubber with poly(ethylene glycol) monomethylether carboxylic acid and ionic conductivity of graft polymer composite electrolytes

A novel comb-like polymer was synthesized via grafting epoxidized natural rubber (ENR) with polyethylene glycol (PEG) monomethylether carboxylic acid (mPEG-COOH), and the grafting reaction was studied by variable-temperature Fourier transform infrared (FTIR) spectroscopy. This comb-like polymer was characterized by attenuated total reflectance-FTIR (ATR-FTIR) spectroscopy and differential scanning calorimetry (DSC). The carboxyl groups of mPEG-COOH reacted with the epoxy groups of ENR to produce graft polymers. The composite polymer electrolyte (CPE) based on this comb-like polymer ENR-g-mPEG-COOH was prepared via introducing LiClO4 into the graft polymer matrix. The CPE was studied by X-ray diffraction analysis (XRD), DSC, an equilibrium swelling method, and electrochemical workstation techniques. With increasing mPEG-COOH content, the ionic conductivity of the electrolyte significantly increased.