Green esterification: A new approach to improve thermal and mechanical properties of poly(lactic acid) composites reinforced by cellulose nanocrystals

Abstract

Cellulose nanocrystal (CNCs)‐reinforced poly(lactic acid) (PLA) nanocomposites were prepared using twin screw extrusion followed by injection molding. Masterbatch approach was used to achieve more efficient dispersion of CNCs in PLA matrix. Modified CNCs (b‐CNCs) were prepared using benzoic acid as a nontoxic material through a green esterification method in a solvent‐free technique. Transmission electron microscopy images did not exhibit significant differences in the structure of b‐CNCs as compared with unmodified CNCs. However, a reduction of 6.6–15.5% in the aspect ratio of b‐CNCs was observed. The fracture surface of PLA‐b‐CNCs nanocomposites exhibited rough and irregular pattern which confirmed the need of more energy for fracture. Pristine CNCs showed a decrease in the thermal stability of nanocomposites, however, b‐CNCs nanocomposites exhibited higher thermal stability than pure PLA. The average storage modulus was improved by 38 and 48% by addition of CNCs and b‐CNCs in PLA, respectively. The incorporation of b‐CNCs increased Young's modulus, ultimate tensile stress, elongation at break, and impact strength by 27.02, 10.90, 4.20, and 32.77%, respectively, however, CNCs nanocomposites exhibited a slight decrease in ultimate strength and elongation at break. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 46468.

Deterioration in the Physico-Mechanical and Thermal Properties of Biopolymers Due to Reprocessing

“…The formation of cross-linking in the polymer matrix hinders the untangling of the polymer chains and the sliding over each other after the glass transition temperature in the rubbery state [28]. In the DMA test, the mobility of the polymer chains is a response against the dynamic deformations of a particular frequency, and the viscoelastic properties of the polymers can be evaluated through the peak values of the tanδ curves [29]. Surprisingly, the recycled Solanyl displayed a lower tanδ peak intensity as compared with virgin Solanyl, suggesting, fewer polymer chains participate in the transition from a glassy to a rubbery state.…”

Trends in Advanced Functional Material Applications of Nanocellulose

“…Reinforcement of high melting temperature polymers with modified biomass has extensively been reported [6][7][8][9][10][11]. Likewise, it has also been extensively reported that the addition of cellulose fibrils in various forms to produce polymeric composites can greatly enhance mechanical properties of the base polymeric materials at significantly lower loadings compared to other biomasses [12][13][14][15][16][17]. Forms of cellulose fibrils can range from cellulose powders to microcrystalline cellulose and nanocrystalline cellulose.…”

Preparation and analysis of poly(l‐lactic acid) composites with oligo(d‐lactic acid)‐grafted cellulose

“…α‐Cellulose has a large number of hydroxyl groups, which are the main basis for hydrogen interactions between two nanofibrils and produce gel‐like structures and the dispersion of hydrophilic cellulose in hydrophobic polymer matrixes; they also serve as an obstacle to better interfacial adhesion between the components of the final composites . To increase the compatibility between α‐cellulose and the polymer matrix, α‐cellulose can be modified physically or chemically . A favorable solution is the chemical surface modification of α‐cellulose to reduce the number of hydroxyl interactions and to increase its compatibility with different matrixes.…”

“…[14][15][16] To increase the compatibility between α-cellulose and the polymer matrix, α-cellulose can be modified physically or chemically. [17][18][19] A favorable solution is the chemical surface modification of α-cellulose to reduce the number of hydroxyl interactions and to increase its compatibility with different matrixes. Recently, several chemical methods, including ringopening polymerization, atom transfer radical polymerization, reversible addition fragmentation chain-transfer polymerization, nitroxide-mediated polymerization, and single electron transferliving radical polymerization, have been used to modify cellulose surfaces.…”