Ultrasonication-induced re-dispersion of freeze-dried cellulose nanoparticles for improving strength and durability of PAN polymer matrix

Abstract

Cellulose nanocrystals (CNCs) have acquired considerable attention owing to their noteworthy properties, including high crystallinity, biodegradability, high specific surface area, and excellent mechanical characteristics that alter the inherent features of the polymer matrix upon reinforcement. Typically, CNCs undergo freeze-drying or spray-drying to facilitate handling and dispersion in a hydrophobic polymer medium. Unfortunately, these drying procedures compromise the intrinsic nano-scale properties of CNCs. Therefore, achieving a uniform re-dispersion of dried CNCs is imperative to attain the desired characteristics in the polymer composite. This study specifically focuses on achieving a homogeneous re-dispersion of freeze-dried CNCs within a waste polyacrylonitrile (PAN) matrix through a simple ultrasonication treatment. The enhanced mechanical properties of the PAN polymer matrix validate the impact of ultrasound energy on re-dispersing CNCs. A noticeable improvement in the tensile properties of the composite polymer film is observed when CNC particles are well-dispersed in the PAN matrix. This observation is substantiated through SEM imaging, XRD, and FTIR data of both neat PAN and PAN–CNC composite films. The results affirm that particle dispersion plays a crucial role in augmenting the tensile properties of PAN composite films.