Green thin films for food packaging are essential and growing in recent years to reduce the dependence on petroleum‐derived plastics. In this study, the glycerol‐plasticized chitosan film incorporated with 1–3% of crude Piper betel Linn. leaf (PBLL) extract was prepared via facile casting process and was characterized by scanning electron microscope, attenuated total reflection‐Fourier transform infrared, thermogravimetric analysis, X‐ray diffraction, UV–Vis, contact angle, water content, antimicrobial, and antioxidant activities. The film improved the protective properties of the sole chitosan and enhanced the UV‐blocking ability of glycerol‐plasticized chitosan film in the regions of Ultraviolet B (280–320 nm) and Ultraviolet A (320–390 nm), resulting in suitable film for food packaging applications. Furthermore, the presence of PBLL extract predominantly containing phenolic compounds in blend film induced very strong antimicrobial activities against Staphylococcus aureus, Pseudomonas aeruginosa, Salmonella typhimurium, and Escherichia coli. The modified chitosan films increased the hydrophilic property resulting in high potential in degradability and can also protect the king orange by coating with the shelf life‐prolonging up to 18 days at 20°C with acceptable appearance and texture. Our results can be developed to produce industrial green thin films to protect fruits during transportation and preservation.
Positron annihilation lifetime spectroscopy (PALS) has been used to study the free volume in dry synthetic polymer nanoparticles of various sizes. A series of poly(styrene/divinyl benzene) particles with diameters in the range of 100 to 500 nm were synthesized and then carefully chemically treated using the sulfonation process, to increase their porosity. The particles were characterised by Scanning Electron Microscopy (SEM), light scattering and PALS. Light scattering gave larger size for the treated particles, reflecting the hydration effect and therefore the increase in porosity. PALS spectra of untreated and treated particles gave four and three life-time components, respectively. Analysis by PAScual version 1.3.0 program indicated there was a reduction in the intensity and the type of the micropores in the treated particles. The data suggest PALS is a sensitive tool for detecting changes in microporosity in particles. The conflicting results obtained for light scattering compared to PALS for chemically treated particles is difficult to resolve and suggests sample preparation of polymeric materials for PALS is the critical factor.
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