Morphologies and properties of nanocomposite films based on a biodegradable poly(ester)urethane elastomer

Abstract

Biodegradable poly(ester)urethane (PU) elastomer-based nanocomposite films incorporated with organically modified nanoclay were prepared with melt-extrusion compounding followed by a casting film process. These films were intended for application as biodegradable food packaging films, with their enhanced gas barrier, mechanical, and thermal properties and good flexibility. From both X-ray diffraction measurements and transmission electron microscopy observations, the coexistence of intercalated tactoids and exfoliated silicate layers in the compounded PU/clay nanocomposite films was confirmed. In addition, the morphology exhibited a clay dispersion state in the matrix and was influenced by the incorporated nanoclay content. The effects of the nanoclay loading level on the thermal, mechanical, and barrier properties of the compounded nanocomposites were also investigated. As a result, it was revealed that the addition of nanoclay up to a certain level resulted in a remarkable improvement in the thermal properties in terms of thermal stability and the degree of thermal shrinkage; mechanical properties, including dynamic storage modulus and tensile modulus; and oxygen/water-vapor barrier properties of the nanocomposite films.

Thermal, mechanical, and gas barrier properties of ethylene–vinyl alcohol copolymer‐based nanocomposites for food packaging films: Effects of nanoclay loading

“…This result can be ascribed to the decomposition of low molecular weight organic modifiers (methyl tallow bis‐2‐hydroxyethyl quaternary ammonium) adsorbed on the clay surface. For the nanocomposites containing nanoclays treated with organic modifiers, the initial degradation temperatures have been usually observed to be reduced with increase of added nanoclay content because of decomposition phenomena of organic modifiers at initial low temperature range . As the true thermal stability parameters, therefore, the degradation temperatures at 50% weight loss ( T 50 ) were obtained from the thermograms in the higher temperature region after elimination of surfactants, which were determined as 386, 387, 389, and 392°C for the neat EVOH, EVCL3, EVCL5, and EVCL7, respectively.…”

“…Therefore, both tensile properties of modulus and elongation for the materials are not able to be improved simultaneously by only one technical method. It has been observed that the inclusion of inorganic clay possessing very high stiffness as well as high aspect ratio into polymer matrix improved the strength and modulus, but resulted in a reduction in the tensile elongation responsible for the flexibility of the nanocomposite film …”

“…The planar‐structured nanoclay with high aspect ratio has been considered as an efficient barrier to the permeation of gas molecules such as oxygen, carbon dioxide, and water vapor. Accordingly, the incorporation of such inorganic clay nanoplatelets into a polymer matrix has been attempted to improve gas barrier performances of the produced nanocomposites by increasing the tortuous path for penetrating gases . Figure shows the oxygen and water vapor permeabilities of the EVOH/clay nanocomposite films plotted as a function of added clay content.…”

“…Such polymer nanocomposites exhibit greatly enhanced gas barrier, thermal, and mechanical properties with the incorporation of very low amounts of clay, compared to those of neat polymers or conventional composites with micrometer scales . It has been commonly observed that improvements in the properties of nanocomposites are more prominent when highly intercalated or exfoliated nanoclay platelets are homogeneously dispersed in the polymer matrix …”

Nanocomposite materials based on zinc sulfide nanoparticles reinforced chlorinated styrene butadiene rubber

“…Major challenges associated with the incorporation of nanoparticles into the polymer matrix include incompatibility between nanoparticles and the polymer, the agglomerating tendency of fillers and the poor dispersion of nanoparticles in polymers. Several strategies have been developed to enhance the uniform dispersion of nanoparticles in the polymer matrix . Most of these methods require an additional step of ultrasonication for the dispersion of nanoparticles in an organic solvent followed by mixing with the polymer.…”