Spectral Study For Reaction Mechanism Of Etherification Of Rice Straw

In this study, etherification reaction was applied to modify rice straw into a thermoplastic material. Etherification of rice straw was carried out with NaOH as swelling agent and catalyst, epichlorohydrin and benzyl chloride as etherifying agent, hexadecyl trimethyl ammonium bromide as phase transfer catalyst (only for benzylated straw) and toluene as solvent. The microstructure of rice straw changed greatly and the polarity was erased partly after modification.Weight percent gain (WPG), infrared spectrum (IR spectrum), CP/MAS 13C NMR spectrum and X-ray diffraction (XRD) were used to study the reaction progress and mechanism of modification.According to WPG of epichlorohydrin-modified rice straw(1-8h), it was found that WPG increased as modification time increased. WPG of epichlorohydrin-modified rice straw increased to 90.12% within 5h in steps, but it kept steadily about 93.00% after 5h. From the IR spectra and 13C NMR spectra of epichlorohydrin-modified rice straw, it was suggested that epichlorohydrin-modified reaction of rice straw could be devided into two steps. Firstly, C-Cl bond of epichlorohydrin broke and repalaced an H of-OH in cellulose. Secondly, epoxy ring of epichlorohydrin which was replaced on cellulose opened and reacted with another-OH of cellulose. Finally, XRD was used to analyse the crystallinity of rice straw before and after modification. It indicated that the crystallinity of rice straw reduce after modification.According to WPG of benzylated straw(1～10h), WPG was about 0.00%within 2h. WPG increasd as modification times increased between 3-8h and achieved the highest of 61.37%. But WPG fell down after 8h. This was approved by IR spectra. There were no benzyl functional group absorption peaks in the IR spectrum of benzylated straw with 2h. The absorption peaks appeared in the IR spectrum when reaction time was longer than 4h. The number of absorption peaks and peak values got maxium at 8h.