Effect of radio frequency pretreatment on enzymatic retting of flax stems and resulting fibers properties

Abstract

Radio frequency (RF) pretreatment of different water-presoaking time and RF treatment durations was introduced into enzymatic retting. RF pretreatment was used to degrade non-cellulosic materials and encourage the fast water-absorbing and swelling of the polar components in flax phloem, thus loosen the interfaces between fibers and fiber bundles and facilitate enzymes penetration. Retting efficiency, the resulting fibers properties and the water sorption after RF pretreatment were measured. It was found that the 8h-30min RF pretreatment improved retting efficiency most, increasing weight loss by 47 % and decreasing pectin content by 7.87 % compared to the control enzymatic retting and obtaining water sorption of 2.19. The results RF treated presoaked and non-presoaked flax were found to be different. The RF treatment of 30 min for the non-presoaked stems did not cause any improvement in pectin removal with a percentage decrease in pectin content of -8.41 %. The reason probably was that partial pectic substances in the non-presoaked flax phloem were dried, hardened and compacted during RF treatment. It was also found that RF pretreatment improved fibers whiteness and tended to weaken fibers tensile performance, and how it affected the fibers tensile properties was closely linked to the RF pretreatment processing.