Microwave assisted retting – A novel method of processing of flax stems

•Novel method of retting of flax stem by using microwave energy.•Non-thermal effect of microwave together with pre-soaking and thermal effect of microwave offers effective retting.•Conducting experiments at various conditions and the process was optimised.

A new method for retting of flax stem was introduced by using microwave energy. The combined effect of pre-soaking, microwave volumetric heating and the non-thermal effect of microwave energy were applied in the retting of flax stem. Effective retting was observed in various combinations of pre-soaking, Microwave treatment times and microwave energy. The samples soaked for 24 and 36 h with microwave treatments of 20 min showed better retting efficiency. Fried tests, Near Infrared analysis and fibre diameter analysis were done to find out the retting efficiency. The effect of non-thermal effect of microwave in flax retting was proved experimentally. Colourimetric tests and tensile strength tests were conducted to compare the quality of fibres after microwave retting and no significant changes in the physical qualities were observed. The water released after pre-soaking was not contaminated because of less microbial activity in short duration of the entire process. In industrial point of view, this method is acceptable because of the ease of recyclability of the pre-soaked water and comparably short duration of the process.