Surface functionalization of nanofibrillated cellulose extracted from wheat straw: Effect of process parameters

• An indirect method for surface propionylation has been used.
• Cellulose microfibril aggregates from wheat straw were surface modified.
• Surface modified aggregates were homogenized to obtain propionated nanofibers.
• Hydrophobic nanofibers with contact angle in the range 115–120°.
• Thermal stability of the surface modified nanofibrils using TGA/DTGA analysis.

Aggregates of microfibrillated cellulose isolated from wheat straw fibers were subjected to propionylation under different processing conditions of time, temperature and concentration. The treated fibers were then homogenized to obtain surface modified nanofibrillated cellulose. For varying parameters, progress of propionylation and its effects on various characteristics was investigated by FTIR, degree of substitution, elemental analysis, SEM, EDX, TEM, X-ray diffraction, static and dynamic contact angle measurements. Thermal stability of the nanofibrils was also investigated using thermogravimetric technique. FTIR analysis confirmed the propionylation of the hydroxyl groups of the cellulose fibers. The variations in reaction conditions such as time and temperature had shown considerable effect on degree of substitution (DS) and surface contact angle (CA). These characterization results represent the optimizing conditions under which cellulose nanofibrils with hydrophobic characteristics up to contact angle of 120° can be obtained.