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To enhance the oxygen-barrier and water-resistance properties of poly(vinyl alcohol) (PVA) and expand its food packaging applicability, five crosslinked poly(vinyl alcohol)/poly(acrylic acid) (PVA/PAA) blend films were prepared via esterification reactions between hydroxyl groups in PVA and carboxylic acid groups in PAA. The physical characteristics of the blends, including the thermal, barrier, mechanical and optical properties, were investigated as a function of PAA ratio. With increasing PAA content, the crosslinking density was significantly increased, resulting in changes in the chemical structure, morphology and crystallinity of the films. The oxygen transmission rate of pure PVA decreased from 5.91 to 1.59 cc m −1 day −1 with increasing PAA ratio. The water resistance, too, increased remarkably. All the blend films showed good optical transparency. The physical properties of the blend films were strongly correlated with the chemical structure and morphology changes, which varied with the PAA content.

Polypropylene (PP)/octadecane (OD) composite films were prepared via twin-screw extrusion, and their chemical, morphological, thermal, and surface properties and oxygen and water vapor permeabilities were analyzed as functions of the OD content and temperature. OD was dispersed well in the PP matrix, and two phases (i.e., the PP and OD portions) were present in the PP/OD composite films. When the temperature was increased from 10 to 30 8C, both the oxygen transmittance rate and the water vapor transmittance rate of the PP/OD composite films increased sharply because of the influence of the OD content. These results were related to the temperature-dependent changes in the morphological structure, such as changes in the the tortuous paths and crystallinity in the composite films because of the addition of OD. In the storage test, the PP/OD (83:17) composite films continuously controlled the gas concentration of the headspace and protected against environmental factors; this reduced the enzymatic activity and led to higher quality cherry tomatoes compared to the case when the pure PP and MP33000 films were used. V C 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 44087.

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A series of poly(vinyl alcohol)/sodium montmorillonite (PVA/NaMMT) nanocomposite films were prepared via a solution method, and their water sorption and water‐resistant properties were investigated as a function of clay content. The water sorption and water resistance properties were strongly dependent on the chemical structure and film morphology originating from the NaMMT content. The water diffusion coefficient and water uptake of the PVA/NaMMT nanocomposite films were obtained by best fits to a Fickian diffusion model. The diffusion coefficient and water uptake in the PVA/NaMMT nanocomposite films varied between 8.16 × 10−10 and 3.60 × 10−10 cm2 s−1 and 35.6 and 29.9 wt%, respectively. Both the diffusion coefficient and water uptake decreased as the content of NaMMT in pure PVA was increased. Additionally, the water resistance pressure (mm) of the PVA/NaMMT nanocomposite films increased with increasing NaMMT content. Contact angle analyses showed that the chemical affinity to water and the surface energy of the nanocomposite films decreased with increasing NaMMT content. Furthermore, the well‐dispersed and exfoliated structure in the nanocomposite films not only induced an increased tortuous path for water molecules to pass through, but also increased the molecular order. However, to enhance the water sorption properties and water resistance of hydrophilic PVA, further studies to increase the dispersion of clay particles and ensure desired morphological qualities such as crystallinity and molecular packing order in the PVA/clay nanocomposite films are required. POLYM. COMPOS., 36:660–667, 2015. © 2014 Society of Plastics Engineers

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A ceramic powder that emits far-infrared radiation (FIR) was incorporated into low-density polyethylene (LDPE) via melt-compounding and subsequent melt-extrusion processes. To investigate the feasibility of as-prepared LDPE/FIR composite films for use in packaging applications, the composite films were characterized using Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, thermogravimetric analysis, differential scanning calorimetry, FIR emissivity and emissive power, antimicrobial activity assays, and storage tests. The physical properties and antimicrobial activities of the composite films were found to strongly correlate with the changes in the chemical and morphological structures that originate from different contents of FIR ceramic powder. A higher content of FIR ceramic powder in the LDPE/FIR composite film provided increased FIR emissivity and emission power of the composite and resulted in good antimicrobial activity. Storage tests also showed that incorporation of FIR ceramic powder into LDPE film was an effective method for maintaining the freshness of lettuce. Furthermore, the incorporation of FIR ceramic powder into LDPE films induced higher thermal stability and crystallinity and enhanced their barrier properties, which suggest these LDPE/FIR composite films are potential candidates for advanced packaging materials for the food and medical industries.