Microperforation of Three Common Plastic Films by Laser and Their Enhanced Oxygen Transmission for Fresh Produce Packaging

Three different plastic films of biaxially oriented polypropylene (BOPP), biaxially oriented polyethylene terephthalate (BOPET) and low‐density polyethylene (LDPE) were perforated using Nd‐YAG laser. Effects of laser pulse energy were examined by varying energies from 50 to 250 mJ where the pulse duration and pulse repetition were kept constant at 10 ns and 1 Hz, respectively. It was found that perforation diameters of all films increased with increasing pulse energies. Observed perforations were different among the three film types. Explanation was contributed to material inherent property and its interaction with laser. Incorporation of an inorganic filler (i.e. silica based anti‐blocking agent used in packaging film) of 0.5 wt% into the LDPE films (0.5Si‐LDPE) could improve perforation performance for LDPE. This was attributed to an increased thermal diffusivity of the 0.5Si‐LDPE film. Commercial BOPET and BOPP films containing 97 microholes/m² (hole diameter of ~100 µm) showed an improvement in oxygen transmission rates (OTR) of 18 and 5 times that of the neat films without perforation. In the case of perforated 0.5Si‐LDPE films having similar perforations of 97 microholes/m² and perforation diameter of 100 µm, a two‐fold increase of OTR was obtained. Gas transmission rates of the microperforated films were measured based on the static method. Measured OTR and CO₂TR values of the three films with varying perforation diameters in a range of ~40–300 µm were compared and discussed. Overall results clearly indicate that perforation by laser is an effective process in developing breathable films with tailored oxygen transmission property for fresh produce packaging. Copyright © 2014 John Wiley & Sons, Ltd.     

Structural and optical properties of encapsulated ZnO in porous host matrix

ZnO nanoparticles were encapsulated in the porous activated carbon matrix by incipient-wetness impregnation. The use of the small host matrix allowed the size confinement of ZnO by utilizing the porous nature of the host matrix. Partial fixation of ZnO in the porous matrix determines the size and the dispersion of the particles. Experiments at different calcination temperatures were carried out to investigate structural and optical properties of ZnO nanoparticles in the porous activated carbon matrix using X-ray diffraction, scanning electron microscopy, Raman spectroscopy and photoluminescence. The optimal calcination temperature was found to be ～450 °C in order to confine ZnO nanoparticles in the porous ACP matrix. Near-band-edge UV emission and green emission were both associated with the deep-level defect state. A decrease in full width at half maximum of E₂ mode in Raman spectrum confirmed an increase in crystallite size due to higher calcination temperature, causing an increase in phonon lifetime.     

Surface-enhanced Raman scattering substrate of silver nanoparticles depositing on AAO template fabricated by magnetron sputtering

In this report, we describe a fabrication process of low-cost and highly sensitive SERS substrates by using a simple anodizing setup and a low-energy magnetron sputtering method. The structure of the SERS substrates consists of silver nanoparticles deposited on a layer of anodic aluminum oxide (AAO) template. The fabricated SERS substrates are investigated by a scanning electron microscope (SEM), a transmission electron microscope (TEM), and a confocal Raman spectroscope. We have verified from the surface morphology that the fabricated SERS substrates consist of high-density round-shape silver nanoparticles where their size distribution ranges from 10 to 30 nm on the top and the bottom of nanopores. The surface-enhanced Raman scattering activities of these nanostructures are demonstrated using methylene blue (MB) as probing molecules. The detection limit of 10⁻⁸ M can be achieved from this SERS substrate.     

Structural study of (1-x)BNKLT-xBZT ceramics using XRD,Raman spectroscopy and XAS

Abstract

The aim of this work is to study the structural phase of (1-x)Bi_0.5(Na_0.74K_0.16Li_0.10)_0.5TiO₃–xBaZr_0.05Ti_0.95O₃ ((1-x)BNKLT-xBZT) ceramics with various x content between 0.025 and 0.150?mol% synthesized via the combustion method. The X-ray diffraction (XRD), Raman spectroscopy and X-ray absorption spectroscopy (XAS), including X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS), were used to investigate the structural phases of all samples. The XRD pattern and Raman spectra revealed coexisting phases of rhombohedral (R) and tetragonal (T) in all compositions. As the BZT content increased, the phase formation in these samples exhibited higher tetragonality. The quantity of each phase in (1-x)BNKLT-xBZT ceramics can be determined by the XAS technique with Ti K-edge measurements. Increasing the BZT content from 0 to 0.15?mol% caused the R phase to suddenly deceased from 60.9% to 20% while the T phase rapidly increased from 39.1% to 80%. The phase of the structural was determined by several alternative strategies including XRD, Raman and XAS techniques.     

Designs and investigations of anti-glare blue-tint side-view car mirrors

Recent developments for luxury car industries have been in favor of anti-glare color-tint side-view exterior car mirrors. In this study, we explore the designs, the fabrications, and the investigations of anti-glare blue-tint samples suitable for the side-view car mirrors. With an aid of the thin film design software, the TiO₂-based backside-coated optical systems are prepared by the homemade and the retailed sputtering systems, and examined for the reflection spectra and the chromaticity diagrams. From four major designs of the anti-glare blue-tint mirrors, the ultra-thin metallic layer and the dielectric stack with the bottommost reflective layer offer the blue-tint at 85% highest reflection. Although the design requires only 40 min of the deposition time, the careful control of the ultra-thin metallic film thickness is crucial.     

Flexible and Tough Poly(lactic acid) Films for Packaging Applications: Property and Processability Improvement by Effective Reactive Blending

This study demonstrates a practical means to overcome inherent brittleness problem of poly(lactic acid) (PLA) and make PLA feasible as packaging material. PLA with suitable processability is utterly required for package manufacturers, where flexible, tough PLA film is essential for packers and end users. Highly flexible PLA films with 60‐fold increase in elongation at break (Eb) over that of the neat PLA were successfully produced by integrating effective reactive blending and economical film blowing process. The ‘two‐step’ blending was used to prepare PLA compound; poly(butylene adipate‐co‐terephthalate) (PBAT – another biodegradable polymer) was first blended with 0.5–1% chain extender (epoxy‐functionalized styrene acrylic copolymer) (ESA), followed by subsequent blending with PLA in twin‐screw extruder. Blown films of reactive blend of PLA/PBAT/ESA (80/20/1) showed impressively high Eb of 250% versus a very low Eb of 4% for the neat PLA. Resulting blown films still possessed high modulus of 2 GPa, yield stress of 50–60 MPa and good toughness of ~100 MPa. Significant enhancement in the film's ductility was attributed to homogeneous blend with developed fine strand‐like structure as a result of effective in situ compatibilization and good interfacial adhesion between the PLA and PBAT. PLA/PBAT/ESA blend also offered improved processability. Resulting films had acceptable haze of ~10% for common packaging, and clearer film close to PLA (≤2%) could be obtained by designing PLA skin layers in multilayer structure. Films of PLA/PBAT/1%ESA exhibit potential as packaging material; their mechanical and optical properties are comparable with or even exceed some existing films used in the market. Copyright © 2015 John Wiley & Sons, Ltd.     

Efficacy of chitin-PAA-GTMAC gel in promoting wound healing: animal study

Acrylic grafted chitin (chitin-PAA) was modified with glycidyltrimethylammonium chloride (GTMAC) with the aim of promoting wound healing. The chitin-PAA-GTMAC gels with different GTMAC contents were compared with the original chitin-PAA gel and Intrasite gel for their efficacy in deep wound healing of Wistar rats. Four full-thickness wounds were made on the dorsal skin of rats and then each was treated with 4 materials; chitin-PAA, chitin-PAA-GTMAC(1:4), chitin-PAA-GTMAC(1:10) and Intrasite gel. During 18 days of treatment, the wounds were visually observed and calculated for wound size using image analysis program. Skin wound tissues of sacrificed rats were processed for routine histological observation and immunohistochemistry of proliferating cell nuclear antigen (PCNA). The wounds covered with the chitin derivatives either with or without GTMAC showed a significant reduction in wound size in day 9 in comparison with day 12 for those covered with Intrasite gel. The faster rate and the better pattern of epidermal development observed in histological study as well as the higher dermal cell proliferation (PCNA expression) also demonstrated the better efficiency in wound healing of the chitin derivatives than Intrasite. The earliest epidermal development of the wounds treated with chitin-PAA-GTMAC (1:4) among the tested materials suggested the most promising of this material for the treatment of full-thickness open wound.     

Microstructural Analyses of Biaxially Oriented Polylactide/Modified Thermoplastic Starch Film with Drastic Improvement in Toughness

This study presents microstructural regularization of biaxially oriented polylactide blended with a silane‐modified thermoplastic starch (BO‐PLA/mTPS) film, traced by X‐ray diffraction and scattering, and differential scanning calorimetry techniques. Interfacial adhesion improvement of mTPS favors PLA crystallization, and produces a large δ‐crystal (100–150 nm) with isotropic orientation when combining with BO stretching. High draw ratio (5 × 5), and BO stretching rate (75 mm s^?1) lead to tight packing of PLA lamellae in both BO‐PLA/TPS and BO‐PLA/mTPS films, resulting in drastic toughness improvement (i.e., fivefold increases of Young's modulus and tensile strength, and threefold increase of elongation, as compared to those of the films without the BO process) with significantly decreased water absorption. However, the effect of reactive compatibility by mTPS on mechanical and water barrier properties is hindered by the BO process in which the V_H‐type patterns of TPS and mTPS are unclearly present, overlapped with (203) diffraction plane of PLA crystal, especially applying fast stretching.     

Immobilization of CO2 by aqueous K2CO3 using microfibrous media entrapped small particulates for battery and fuel cell applications

This work focuses on developing a new adsorptive material and regenerable system for CO₂ sequestration to supply CO₂-free gas stream for low temperature and low carbon dioxide concentration applications, such as alkaline fuel cells, metal-air batteries, and portable air-purifying respirators. A novel microfibrous media has been introduced for carbon dioxide filtration from wet gas streams at room temperature. The use of microfibrous media in a composite bed maximizes the breakthrough capacity per unit volume and promotes high accessibility. The microfibrous media synergically combines the high contacting efficiency of the microfibrous matrix and the small internal mass transfer resistance of small particulates. The carbon dioxide adsorption capacity of the microfibrous media can be reversibly recovered. The incorporation of microfibrous media to the sodalime was observed. The result shows 120% improvement in the breakthrough capacity compared with the packed bed of the sodalime with the same volume. This approach can be applied to miniaturize the reactor and reduce thermal mass enhancing process intensification.     

Porous Ultrahigh Gas‐Permeable Polypropylene Film and Application in Controlling In‐pack Atmosphere for Asparagus

Porous polypropylene (PP) films with greater gas permeability and lower permeability ratios (β) than existing commercial films were developed for fresh produce packaging. PP containing high content of beta‐form crystal was biaxially stretched under controlled conditions. Resulting porous films with uniquely high oxygen transmission rate (OTR) of 2 659 000 cm³?m^?2?d^?1, water vapor transmission rate of 67 g?m^?2?d^?1, and β value of 0.76 was used as a “breathable window” attached to the less permeable commercial BOPP (biaxially oriented PP) lidding film. Various sizes/areas of the breathable windows were designed and tested on packaging asparagus of 400 g, at 5°C. Results demonstrated that in‐pack O₂ and CO₂ concentrations could be practically controlled and modified by changing areas of the breathable windows. Altered porous high OTR area directly affected total gas permeation of the package. Optimum gas composition of Ο₂ and CΟ₂ within the recommended controlled atmosphere for asparagus, stored at 5°C, was effectively created and maintained in the package containing 25 cm² breathable window (15% of total film lid's area). The shelf life of asparagus under optimum modified atmosphere was extended to 29 days, as compared with <3 days in the normal, low OTR tray sealed with BOPP lidding film. Clearly, these developed porous ultrahigh permeable PP films can be useful materials in designing high OTR package with desirable in‐pack O₂ and CO₂ concentrations. Copyright © 2013 John Wiley & Sons, Ltd.