Chemical treatments of flax fibers – Control of the diffusion of molecules into the fiber structure

[Display omitted] •Flax fabrics were impregnated by several treatment agent solutions.•Different combinations of molecules, macromolecules and solvents have been tested.•Phosphorus and fluorine mapping (SEM-EDX) was used to locate the grafting agents.•Control of impregnation conditions allowed a regioselective modification of flax. This study concerns the control of the diffusion of molecules and macromolecules in the structure of flax fibers during the impregnation step of a radiation grafting procedure. In this work we essentially focused on the impact of the conditions used during the impregnation of flax fabrics on localization of the treatment agent in the fibers structure. In a first step fabrics were impregnated by dipping them into a solution containing different chemical monomers, polymers or copolymers combined with various solvents. After solvent elimination, fibers were characterized by SEM/EDX to evaluate the presence of the treatment agents in their structure. Influences of treatment agent and solvent combination and duration of the impregnation step were evaluated. The regioselective localization at the surface or the presence in the whole fiber can be obtained through a suitable choice of the treatment agent and the solvent. The duration of the impregnation process can also modify this localization when the affinity between the treatment agent and the solvent is low. Two new strategies of double functionalization were successfully developed. The first one is based on the repetition of the irradiation sequence (impregnation, irradiation, washing) on the same sample but with change of the treatment agent for the second cycle. The second strategy is based on a single impregnation step with a regioselective localization of the treatment agents due to their differences of affinity with solvent used.