Composite Films of Poly(vinyl alcohol) and Bifunctional Cross-linking Cellulose Nanocrystals

Abstract

Long and flexible cellulose nanofibrils or stiff and short cellulose nanocrystals (CNCs) are both promising lightweight materials with high strength and the potential to serve as reinforcing agents in many polymeric materials. In this study, bifunctional reactive cellulose nanocrystals (RCNCs) with carboxyl and aldehyde functionalities were used as reinforcements to prepare acetal-bonding cross-linked poly(vinyl alcohol) (PVA) films. Two RCNCs were obtained through the mechanical homogenization of partially carboxylated dialdehyde cellulose (DAC) with a residual aldehyde content of 0.55 and 1.93 mmol/g and a carboxyl content of 1.65 and 1.93 mmol/g, respectively. The mechanical, thermal, and barrier properties of PVA-RCNC films with a variable mass ratio of RCNCs (0.5-10%) were determined. Reference CNCs without reactive aldehydes were obtained through the reduction of aldehyde functionalities to primary hydroxide groups, and their reinforcing effect was compared to RCNCs. With the addition of 10% acetal-bonding RCNCs with respect to PVA weight, the tensile strength and Young's modulus were up to 2-fold greater than those of pure PVA film. An addition of only 0.5% RCNCs improved the tensile strength of the PVA film by 66% and the modulus by 61%. In comparison, a significantly lower reinforcing effect (19% with CNC loading of 0.5%) was found using reference CNCs. PVA's effective oxygen barrier and thermal properties were preserved when RCNCs were introduced into the films.

Crosslinked poly(vinyl alcohol) composite films with cellulose nanocrystals: Mechanical and thermal properties

“…when PVA/CNC composites (1 and 2 wt %) were compared to the neat PVA . These observations have led to the conclusion that the reinforcing ability of CNCs is dominated by the interfacial interaction between the CNCs and PVA …”

“…However, the poor mechanical properties of PVA limit its use . The introduction of a reinforcing material in the PVA matrix has been reported to improve its mechanical properties …”

Antibacterial cellulose acetate films incorporated with N‐halamine‐modified nano‐crystalline cellulose particles

“…In the literature, it has been reported that the addition of nano‐sized particles can enhance the nucleation of a polymer and thus would increase the crystallinity index. The diffraction pattern of NCC‐PMAMs could not be detected in CA/NCC‐PMAM‐Cl nanocomposite films, and there was no peak shift due to the addition of NCC‐PMAM particles, which could mean that an intercalated structure might exist between CA polymer and NCC‐PMAM nanoparticles. …”

Interfacial modification mechanism of nanocellulose as a compatibilizer for immiscible binary poly(vinyl alcohol)/poly(ethylene oxide) blends

“…As is shown in Figure (a), the pure PVA had two stages of decomposition, whereas there was only a single sharp decomposition in the pure PEO. For PVA, the first decomposition region, at approximately 250–370 °C, was due to the degradation of the PVA chain, whereas the second region, at approximately 380–500 °C, was due to the carbonation of the polymer matrix and was followed by a final decomposition of the polymer . PEO exhibited only a single‐stage degradation, which occurred at approximately 367–450 °C by the random chain scission of CO bonds .…”