Drying of non-chemically prepared nanofibrillated cellulose from lime residue: Effects of drying methods on fiber morphology, physicochemical properties and redispersibility

The effects of drying methods, i.e., hot air oven and spray drying, defibrillation step and use of maltodextrin as a drying aid on microstructure as well as water redispersibility of dried nanofibrillated cellulose (NFC) were investigated; NFC-to-maltodextrin ratios were varied at 1:0, 1:1, 1:1.5 or 1:2. Spray-dried NFCs possessed lower crystallinity index (CI) values than oven-dried NFC. Higher added maltodextrin content resulted in lowered CI values due to an increase in the amorphous fraction within the samples. Freshly prepared NFC suspension exhibited gel-like behavior, while suspensions prepared by redispersing any dried NFC in water lost such a behavior. High pressure (100 MPa) applied during microfluidization defibrillation is postulated to cause the degradation of pectin, leading to the loss of its capability to serve as Van der Walls interactions and hydrogen bonding formation inhibitor. Although maltodextrin could somehow help form a dispersed fibrillar structure upon water reconstitution, the extents of such a structure in all cases were still not adequate to regain the gel-like behavior.