Kinetics of in situ fibrillation of modified fibres

Important results from the project

BillerudKorsnäs and KTH have developed a technology for chemical fibrillation of modified cellulose fibres into nanofibrils. In order to be able to develop a more large-scale process, one needs to understand on what time scales the fibrillation takes place. Equipment to achieve the required time resolution was designed and an array of experiments were performed at the P03 beamline at PETRA III (DESY, Hamburg). Complementary experiments will be needed to improve the signal-to-noise ratio and it is too early to say to what extent the results can be used in future process development.

Expected long term effects

During two intense days of beam time at DESY, hundreds of experiments were performed, including varying alkali concentration and flow rates. Experimental data have been processed and compared with theoretically plausible fibrillation processes. Unfortunately, none of these processes could be distinguished from our experimental data, probably due to the relatively large background scattering from nanofibrils released during the chemical modification as well as from the window material. Important lessons have been learned on how future attempts can be performed in a better way.

Approach and implementation

To achieve the desired time resolution, a flow focusing cell was designed where fibres and alkali meet in a T-junction and the flow rates and position in the channel give the time after mixing. Furthermore, the cell and flows were optimised to create a steady flow of fibres into the T-junction. Measurements were performed at synchrotron (P03 at PETRA III, DESY, Hamburg) and the results were compared with theoretical models for fibrillation of cellulose fibres.