Green cross‐linked coir cellulose nanocrystals/poly (vinyl alcohol) composite films with enhanced water resistance, mechanical properties, and thermal stability

Abstract

Poly(vinyl alcohol) (PVA) based materials have received enormous attention ascribed to the merits of good mechanical properties, biodegradability, and environmental friendliness, but its widespread applications are severely hindered by poor water resistance. In the current study, self-made coir cellulose nanocrystal (CCNC) was applied as a reinforcing filler together with a costeffective and green cross-linker (oxalic acid, OA) for preparation of CCNC/ OA/PVA composite film via solution casting. After the thermal treatment of 120 C for 2 h, the ultimate product exhibited remarkable improvements in tensile strength (132.4 MPa), Young's modulus (4427.1 MPa), water resistance (degree of swelling: 33.6%; contact angle: 84.7 ; solubility: 0.9%), and thermal stability relative to the cleavage of the polymer chains (depolymerization). A reinforced synergetic effect of physical interaction (hydrogen bond) and hydrophobic ester linkages has been suggested according to the comprehensive analyses of functional groups, crystal structure, thermal behavior and stability, and fracture surface morphology.

Influence of Lignin Content and Pressing Time on Plywood Properties Bonded with Cold-Setting Adhesive Based on Poly (Vinyl Alcohol), Lignin, and Hexamine

“…To enhance the link of lignin with hexamine, PVOH is used to promote more hydroxy (−OH) groups in the system. PVOH, a highly polar and water-soluble polymer, is well utilized in polymer blends with natural polymeric materials such as cellulose, starch, chitosan, and lignin [ 46 , 47 , 48 ]. In these systems, good material performance was obtained and attributed to the formation of intermolecular hydrogen bonds between the hydroxyl groups of the respective polymers.…”

Lignocellulosic–biomolecules conjugated systems: green-engineered complexes modified by covalent linkers

“…[86][87][88] Unfortunately, citric acid covalently bonds with any hydroxyl group and becomes undesirable for a thoroughly efficient biconjugated formation, 89,90 crosslinking the same type of biomolecule in the process. 91 Besides citric acid, other molecules with carboxylic groups work as linkers and assemble cellulose-biomolecule systems, including oxalic acid 92 and succinic acid. 93,94 Lactic acid, another carboxyl biomolecule, is well-dispersed in water and forms ester bonds between CNC and fatty acids, which are carboxylic molecules (Fig.…”