Effect of carboxymethyl cellulose concentration on mechanical and water vapor barrier properties of corn starch films.

The main objective of this study was to evaluate the effect of the addition of different concentrations of CMC (0, 20, 40, 60, 80 and 100 %) on the mechanical and water vapor barrier properties in corn starch films produced by casting. The addition of CMC 40 % was sufficient to significantly increase its mechanical properties (tensile strength, elongation at break and elastic modulus), and water vapor barrier of the starch films, thus improving its functionality as a packaging material for food. CMC incorporation led to a small reduction in the thermal stability of the films. CMC in low content dispersed well in the starch matrix, ensuring interaction between its constituents that formed a network structure, thus improving mechanical properties and making diffusion of water difficult.

Corn and cassava starch with carboxymethyl cellulose films and its mechanical and hydrophobic properties.

The amylose and amylopectin content of starch influences its functional characteristics and its interaction with other materials. Thus, it is important to study the mechanical strength and hydrophilicity of starch films of different botanical origins to elucidate the influence of their constituents in the interaction with carboxymethyl cellulose (CMC). The objective of this work was to evaluate the mechanical and physico-chemical properties of corn and cassava starch films and their blends with CMC by casting. The addition of CMC improved the tensile, increasing the strength at 206% for its blends with corn starch and 51% for its blends with cassava starch, the rupture stress at 89% and 74%, respectively, and the rupture strain at 381% and 57%, respectively. The elastic modulus presented increase of 20% for corn starch/CMC and 18% for cassava starch/CMC and the water vapor permeability at 48 and 40%, respectively. The corn starch film was more hydrophobic due to its higher amylose content, which contributed to the interaction between starch and glycerol OH groups and CMC COOH groups. This interaction was evidenced by FTIR and contact angle analysis, turning corn starch/CMC films into less hydrophilic material and reducing its water vapor permeability rate, which made this material promising for several applications, including food packaging.

Curaua and eucalyptus nanofibers films by continuous casting: Mechanical and thermal properties.

A wide variety of new green materials such as curaua leaf fibers (CLFs) has potential applications in nanotechnology. This study aims to investigate the thermomechanical properties and morphological structure of cellulose nanocrystals (CNCs) and cellulose nanofibrils (CNFs) films obtained by continuous casting. The CNCs were obtained by acid hydrolysis and CNFs by mechanical shearing from bleached CLFs and eucalyptus pulp. The morphology after continuous casting resulted in oriented nanofibers, and as a consequence there was mechanical anisotropy. CNCs films showed the greatest values of tensile strength (36±4MPa) and the more effective fibrillation provided better mechanical strength of eucalyptus CNFs films than curaua CNFs films. Sulfur groups and mechanical shear degradation affected the stability of CNCs and CNFs films, respectively. Thus, the type of nanostructure, the way they interact to each other, the cellulose source and the process interfere significantly on the properties of the films.