Starch nanocomposites reinforced with TEMPO-oxidized cellulose nanofibrils derived from bamboo holocellulose

Abstract

Bamboo holocellulose was oxidized by 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO) in water at pH 10 with an addition of 7.5 mmol g-1 of NaClO for 2 h. After oxidation, the weight recovery ratio of TEMPO-oxidized bamboo holocellulose (TOBH) was 73% with a carboxylate content of 0.65 mmol g-1. The water-insoluble TOBH was converted to an aqueous dispersion of bamboo TEMPO-oxidized cellulose nanofibrils (TOBCN) through mechanical defibrillation and centrifugation, with the nanofibrillation yield of around 90%. Transmission electron microscopy (TEM) indicated that the widths of TOBCN were estimated to be between 3 and 4 nm and lengths of several micrometers. The TOBCN dispersions had high light-transparencies of 99% at a wavelength of 600 nm. These nanofibrils were used as reinforcing nanoparticles in thermoplastic starch (TPS) films. The TOBCN dispersions were added in dosages of 0, 0.3, 0.6, 0.9, 1.2, and 1.5 wt%. Glycerol was used as a plasticizer. Nanocomposite films were prepared through a solution casting process. The TOBCN/TPS nanocomposite films exhibited high optical transparencies and their tensile strength, Young’s modulus, elongation around failure, and work to cause a fracture increased, compared to the TPS films without TOBCN. The presence of TOBCNs, at 1.5 wt%, improved moisture resistance.

Cellulose nanocrystal assisted dual-modification of starch and subsequent polyvinyl alcohol blends

“…The introduction of acetyl group into OACS improved the dispersibility, and the disrupted structure facilitated their compatibility with PVOH/GL matrix. In addition, the low crystallinity of OACS indicated low crystal boundaries and less scattering (Aulin et al 2013;Sasiprapa et al 2019). The refractive index of corn starch was 1.55, the refractive indices of OACS with 0.1 wt%~0.5 wt% CNC were 1.51, 1.50 and 1.50 respectively.…”

“…Cellulose nanofibers can be used as reinforcing agents due to their high aspect ratio, crystalline nature, and high mechanical strength (Vigneshwaran et al 2011). Thermoplastic starch films fabricated with bamboo cellulose nanofibrils as reinforcing agent and glycerol plasticizer show high transparency and mechanical properties (Sasiprapa et al 2019). However, the good performance of biopolymer films strongly depends on uniform distribution of nanofillers, which is a major challenge (Vigneshwaran et al 2011).…”