Processing of technical flax fibers: A study on the combination of enzymatic and ultrasonic degumming

To maximize their potential for intended applications, technical fibers such as flax ( Linum usitatissimum L.) need to be processed via mechanical or physicochemical methods. Among these, enzymatic and ultrasonic degumming treatments make it possible to modify the material while adhering to green chemistry principles. However, the combination of these treatments to achieve new characteristics has not yet been well investigated in plant fibers, although it is applied to many other lignocellulosic materials. In this study, the first objective was to determine favorable degumming conditions for the enzymatic hydrolysis and ultrasonic irradiation of technical flax fiber. To this end, the impacts of different pectinase cocktails and low-frequency ultrasound conditions on the composition of technical flax fibers were investigated via a screening design. On the basis of these results, the effects of various treatments and their combination on the diameter, surface finish, and thermal and mechanical properties of well-characterized fibers were studied. Notably, the use of a pectate lyase-based cocktail (BioPrep 3000 L) was shown to refine technical fibers by 16–34%, while improving their traction modulus up to 42–76%. Moreover, the use of ultrasound downstream of pectate lyase treatment enhanced the thermal properties and cleaned the fiber surfaces, while reducing the breaking properties up to 20–34%. These impacts have been shown to depend on the raw fiber state. The use of these treatments and their combination is therefore subject to compromises depending on the properties targeted and would require further investigation to achieve optimization.