Tensile Strength and Solubility Studies of Edible Biodegradable Films Developed from Pseudo-cereal Starches: An Inclusive Comparison with Commercial Corn Starch

Edible biodegradable films were prepared from amaranth, buckwheat and commercial important corn starches by casting method. Starch, glycerol and carboxymethyl cellulose (CMC) were used to prepare filmogenic starch solutions in potable luke warm water, followed by ultra-sonication for homogenous mixing of the mixed ingredients. After this, heating was applied to starch based slurried solutions until it turned into gel solutions. These filmogenic gel solutions were then dried and films were peeled off and stored in desiccator. Stored films were analyzed for functional properties viz., tensile strength, solubility and water vapor permeation. Amaranth starch based edible biodegradable films presented considerable clarity values however buckwheat starch and corn starch based films exhibited good tensile strength and better solubility values. Developed edible biodegradable films from amaranth starch were analysed for surface structure examination by SEM. Evaluation of surface revealed uniformity, homogeneity with no surface crack on the surface of developed edible biodegradable films.

Desiccant Films Made of Low-Density Polyethylene with Dispersed Silica Gel—Water Vapor Absorption, Permeability (H2O, N2, O2, CO2), and Mechanical Properties

Silica gel is a well-known desiccant. Through dispersion of silica gel in a polymer, films can be made that absorb and desorb water vapor. The water vapor absorption becomes reversible by exposing such films to a water vapor pressure below that of the water vapor pressure during absorption, or by heating the film. The intention of this study was to achieve a better understanding about the water vapor absorption, permeability (H2O, N2, O2, CO2), and mechanical properties of films with dispersed silica gel. Low-density polyethylene (PE-LD) monolayer films with a nominal silica gel concentration of 0.2, 0.4, and 0.6 g dispersed silica gel per 1 g film (PE-LD) were prepared and they absorbed up to 0.08 g water vapor per 1 g of film. The water vapor absorption as a function of time was described by using effective diffusion coefficients. The steady state (effective) water vapor permeation coefficients of the films with dispersed silica gel were a factor of 2 to 14 (8.4 to 60.2·10−12 mg·cm·(cm²·s·Pa)−1, 23 °C) higher than for pure PE-LD films (4.3·10−12 mg·cm·(cm²·s·Pa)−1, 23 °C). On the other hand, the steady state gas permeabilities for N2, O2, and CO2 were reduced to around one-third of the pure PE-LD films. An important result is that (effective) water vapor permeation coefficients calculated from results of sorption and measured by permeation experiments yielded similar values. It has been found that it is possible to describe the sorption and diffusion behavior of water by knowing the permeability coefficient and the sorption capacity of the film (Peff.≈Seff.·Deff.). The tensile stress changed only slightly (values between 10 and 14 N mm−²), while the tensile strain at break was reduced with higher nominal silica gel concentration from 318 length-% (pure PE-LD film) to 5 length-% (PE-LD with 0.6 g dispersed silica gel per 1 g film).