Thermo-compression of cellulose nanofibrils

All cellulose composites made of 100% cellulose nanofibrils (CNFs) were produced without the use of solvent, binders, chemicals and/or dissolution process. Specimens were produced by thermo-compression and compared with materials made with cellulosic fibers. Different compression conditions such as temperature, time and pressure were tested and their impacts were quantified regarding the mechanical properties of the obtained materials. After determining the optimal compressing conditions, different grades of CNFs were tested and characterized using several characterization methods such as bending properties, Charpy impact strength, water absorption or degree of polymerization. Specimens made of 100% CNFs present improved bending properties, lower Charpy impact strength and lower water sensitivity than samples made with cellulose fibers. CNFs with their smaller size and increased number of possible H-bonds, create samples of lower porosity and allow establishing a solid H-bonding network. However, the particle size of the dry CNF powder influences strongly the self-bonding of the CNFs and the mechanical resistance of the thermo-compressed objects. Objects made of 100% CNFs can now be produced using an environmentally friendly process. Graphic abstract Schematic illustration of the study: production of 100% CNF objects by thermo-compression. [GRAPHICS] .