Effect of cellulose nanocrystal polymorphs on mechanical, barrier and thermal properties of poly(lactic acid) based bionanocomposites

Abstract

Electronic Supplementary Information (ESI) available: XRD and FTIR spectra of pretreated bamboo pulp, AFM micrographs and height profiles of CNC I, CNC II and CNC: I→II and their properties (Table S1), XRD spectra for different PLA/CNC polymorph films at 1wt% CNC loading. See Cellulose nanocrystals (CNCs) using different polymorphs of cellulose were fabricated from raw bamboo pulp through alkali treatment followed by acid hydrolysis. The effect of CNC polymorphs, namely CNC I, CNC II and CNC:I→II (CNC II from cellulose I), on its morphology, crystal structure, degree of hydrogen bonding and thermal stability were studied. These polymorphs were dispersed in polylactic acid (PLA) films using casting evaporation approach and their effect on the structural, thermal, mechanical and barrier properties of the PLA were investigated. The CNC polymorphs differ significantly in their reinforcement capability and ability to form percolated network. Incorporation of CNC II and CNC: I→II significantly improved the Young's modulus of composites (by ~72%). However, their elongation at break significantly decreased compared to CNC I, due to high hydroxyl functionality, which forms entangled hydrogen bonded network within the polymer matrix, leading to improvement in mechanical as well as barrier properties. The theoretically calculated moduli of composites using Halpin Kardos, Cox-Krenchel and Ouali models showed good agreement for CNC I,CNC II and CNC:I→II respectively, albeit at higher aspect ratio. All three CNCs showed the capability to form percolated network, the occurrence and stability of which varied with the type of polymorphs. Therefore, the current study provides an insight towards selection of appropriate polymorphs for fabrication of CNC reinforced high performance poly (lactic acid) based bionanocomposites.

Magnetic Cellulose Nanocrystal Based Anisotropic Polylactic Acid Nanocomposite Films: Influence on Electrical, Magnetic, Thermal, and Mechanical Properties

“…However, as per our previously reported study 36 , such significant improvements in the TS were found to be absent in case of unmodified CNCs. The significant improvement in TS is probably due to the improved dispersion of the Fe 3 O 4 nanoparticlemodified CNCs due to better compatibility with the PLA matrix.…”

“…corresponding to the crystallographic planes (101), (101̅ ), (002) and (040)(Figure 1(c)), representing the cellulose I crystal structure36 . However, the XRD pattern for the MGCNCs shows presence of relatively new diffraction peaks at 2Ɵ= 33.1°, 35.6°, 49.5°, 54.1°, 62.4° and 64.0° which is consistent with the (220), (311), (422), (511), (440) and (531) reflections of Fe 3 O 4 nanoparticles 38 (Figure 1(c)).…”

Nanocellulose size regulates microalgal flocculation and lipid metabolism

“…This phenomenon demonstrated that agitation induces a tight network among CNF. This characteristic is related to the compact and faster network formation due to mechanical stress on CNF solution141718.…”

Lignin-coated cellulose nanocrystals as promising nucleating agent for poly(lactic acid)

“…Cellulose nanocrystals (CNCs) and nanofibers (CNFs) obtained by acid hydrolysis or TEMPO oxidation of cellulose fibers have been recognized as highly crystalline high aspect ratio fillers that have been widely proposed for incorporation of biodegradable polymer composites [12][13][14]. The incorporation of CNCs and CNFs in a PLA matrix has resulted in a moderate improvement in its crystallization characteristics, mechanical, and barrier properties [15][16][17][18][19][20][21]. However, poor dispersion of CNCs due to their high aspect ratio, intraparticle hydrogen bonding, and poor compatibility with hydrophobic polymers are major limitations in realizing the full potential of CNCs in a PLA matrix.…”