Green composites reinforced with hemp nanocrystals in plasticized starch

Abstract

New nanocomposite films were prepared from a mixed suspension of hemp cellulose nanocrystals (HCNs) and thermoplastic starch, or plasticized starch (PS), by the casting and evaporating method. The morphology, thermal behavior, mechanical properties, and water sensitivity of the films were investigated by means of scanning electron microscopy, wide‐angle X‐ray diffraction, differential scanning calorimetry, tensile testing, contact angle measurements, and water absorption. The results indicate that the cellulose nanocrystals dispersed in the PS matrix homogeneously and resulted in an increase in the glass‐transition temperature ascribed to the fact that the flexibility of the starch molecular chains in the starch‐rich phase was reduced because of the strong intermolecular interactions between the starch and stiff HCNs. The films exhibited significant increases in the tensile strength and Young's modulus, from 3.9 to 11.5 MPa and from 31.9 to 823.9 MPa, respectively, with increasing HCN content from 0 to 30 wt %. In addition to the improvement in mechanical properties, the incorporation of HCNs into the PS matrix also led to a decrease in the water sensitivity of the final composite materials. Therefore, the HCNs played an important role in improving the mechanical properties and water resistance of the starch‐based material. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

Cellulosic Bionanocomposites: A Review of Preparation, Properties and Applications

“…Cellulose whiskers can be prepared from a variety of sources, e.g., microcrystalline cellulose [45], bacterial cellulose [67], algal cellulose (valonia) [68], hemp [69], tunicin [70,71], cotton [62], ramie [36], sisal [72], sugar beet [73], and wood [63]. Transmission electron micrographs of some cellulose nanocrystals are presented in Figure 4.…”

Cellulose Nanocrystals Obtained from Cynara Cardunculus and Their Application in the Paper Industry

“…In particular, the results demonstrated a sensible increase of the 7.9% in the measured tensile strength for the sample Linter paper sheet + NCC from Cynara cardunculus and of the 0.8% for the sample Linter paper sheet + NCC from MCC (10 h), while not significant improvement for this parameter was measured for the Linter paper sheet + NCC from MCC (5 h) sample. There has been significant research in the use of NCC to reinforce natural polymers, e.g., starch and produce all bio-based nanocomposites, fully biodegradables and renewable: it has been for instance demonstrated that starch-based polymers can be reinforced by the addiction of a percentage of NCC as filler, as observed by Cao et al [35].…”

Desenvolvimento e avaliação da eficácia de filmes biodegradáveis de amido de mandioca com nanocelulose como reforço e com extrato de erva-mate como aditivo antioxidante

“…Portanto, as duas formulações resultam em filmes que podem ser empregados para diferentes aplicações, independente do aditivo incorporado, já que diferem em relação ao módulo, tensão e deformação. Ressalta-se ainda que as ótimas propriedades mecânicas apresentadas pelos filmes (A, B, CA e CB) estão relacionadas à presença dos nanocristais de celulose de coco, como relatado por outros autores que também incorporaram nanocristais de celulose de diferentes fontes em matrizes poliméricas biodegradáveis (WANG et al, 2006;CAO et al, 2008). SOUZA et al (2012) relatam valores bastante inferiores para a tensão (1,85 a 4,81MPa) de filmes de amido sem a presença de nanocristais de celulose.…”

“…Entretanto, apesar de os filmes de amido possuirem a vantagem de ter caráter biodegradável, apresentam propriedades mecânicas inadequadas, além de uma alta permeabilidade ao vapor de água (VEIGA-SANTOS et al, 2005a;VEIGA-SANTOS et al, 2005b;MALI et al, 2010), sendo, portanto, impróprios para a comercialização como embalagens. Com o objetivo de melhorar as propriedades mecânicas e de barreiras dos filmes a base de amido e tornar viável a sua comercialização, diversos estudos (LU et al, 2005;CAO et al, 2008;WANG et al, 2010;MACHADO et al, 2010) incorporaram nanopartículas obtidas da celulose de fibras naturais, chamadas de nanocelulose ou nanocristais de celulose.…”