INFLUENCE OF NON-THERMAL MICROWAVE EFFECTS ON HEMP FIBER OBTANED BY MICROWAVE ASSISTED DEGUMMING

Microwave-assisted heating degumming was successfully employed in hemp fiber extraction. This route was selected owing to the fact that it is a fast, green, high-efficiency and low-cost method. The mechanism of action was investigated and the results were compared with those obtained by the traditional water-heating method. The fibers treated by the two procedures were examined by X-ray photoelectron spectroscopy (XPS). Specifically, their C 1s spectra and the corresponding carbon and oxygen atomic concentration ratios (O/C) were analyzed. The results indicated that the O/C ratio gradually increases from 0.35 for untreated hemp to 0.49 for the microwave treated fiber, indicating that the lignin, which is mainly composed of the carbon component, was to a great extent removed from the fiber surface. It was concluded that the non-thermal effects of microwave radiation could accelerate the degumming process and its efficiency, as well as modify the surface composition and the structure of hemp fiber, compared with the conventional waterbath heating method.