Enhanced optical properties of ZnS–rGO nanocomposites for ultraviolet detection applications

In this research, fabrication and characterization of ultraviolet (UV) detectors based on zinc sulfide–reduced graphene oxide (rGO) nanocomposite with the focus on the wurtzite structure of zinc sulfide was carried out. The nanoparticles of ZnS were synthesized using chemical deposition method and annealed at 500?°C under flow of argon. X-ray diffraction pattern showed that ZnS with the wurtzite phase was formed at 500?°C. Here, rGO as a unique material with similar properties to graphene such as high electron transport was used in order to improve the optical properties of ZnS. For this purpose, rGO was added to ZnS with three different weight percentages of 5, 10 and 15. Scanning electron microscopy showed that ZnS nanoparticles were well placed in rGO sheets. The UV–visible spectra of the synthesized composites showed that with increasing rGO in composite, light absorption is increased. Photoluminescence (PL) spectra also showed that with increasing the percentage of rGO the generation of electron-hole in composite was increased and PL peak was enhanced. The effect of elevated generation of electron-hole pairs was apparent in optoelectrical properties of fabricated UV detectors based on the sample with higher concentration of rGO in composite. For this sample, the response time was decreased to 310 ms, and the sensitivity to UV irradiation was increased by 7.7 times.     

(Corn Starch and Montmorillonite Nanocomposite)‐Reinforced Polypropylene: Preparation,Properties, and Biodegradability

Blends of polypropylene and thermoplastic starch (TPS) containing different amounts of TPS were prepared with and without modified montmorillonite (C30B) in the presence of ethylene‐(vinyl acetate) copolymer. Mechanical properties, thermal stability, morphology, and biodegradation were investigated. The results of tensile tests showed that the tensile strength and Young's modulus increased but that elongation at break decreased in the presence of C30B. Small‐angle X‐ray scattering patterns and transmission electron microscopy confirmed that the prepared nanocomposites were exfoliated. Scanning electron microscopy (SEM) was used for the investigation of the phase morphology and particle distribution. Thermal gravimetric analysis indicated that the C30B caused an increase in thermal degradation temperature. Biodegradability tests of the specimens were conducted in a fungal culture medium. Biodegradation was assessed by SEM images, monitoring the changes in the FTIR spectra, and the weight loss of specimens after culturing. J. VINYL ADDIT. TECHNOL., 20:16–23, 2014. © 2014 Society of Plastics Engineers     

Mechanical and thermal properties of polypropylene/recycled polyethylene terephthalate/chopped rice husk composites

The various ratios of recycled polyethylene terephthalate (rPET) into polypropylene (PP) filled with 40 parts chopped rice husk per hundred part of polymer have been studied. Composites were prepared using a corotating twin screw extruder at temperature zones of 165–215, well below 250°C (rPET mp temperature) and characterized by mechanical and thermal properties. To improve the compatibility between different components, PP grafted with maleic anhydride was added as a coupling agent in all the compositions studied. The results showed that the addition of rPET improved the tensile and flexural modulus and impact strength of the composite while reducing its tensile and flexural strength. The scanning electron microscopy micrographs of samples in the injection direction showed that some particle shaped rPET inside the composites appear as drawn fibrils and some appear as plates. Differential scanning calorimetric studies showed that the addition of rPET particles to the composites decrease the PP crystallization temperatures. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Prediction of viscoelastic behavior of interphase in polypropylene‐chopped rice husk composites for β‐relaxation domain

The effect of chopped rice husk (CRH) content on viscoelastic properties and crystallinity of polypropylene (PP) composites was investigated. Composites containing 0, 20, and 40 part per hundred plastics (php) of CRH into PP were prepared by twin‐screw extruder, with maleic anhydride‐grafted PP as the coupling agent. The viscoelastic behavior and the crystallinity of these composites have been studied by dynamic mechanical analysis as well as differential scanning calorimetry, respectively. By the incorporation of CRH into PP, the storage modulus (E′) was found to be increased progressively, whereas the mechanical loss factor (tan δ) decreased in a nonlinear manner. A self‐consistent analysis was proposed for the prediction of viscoelastic response of the interphase between PP matrix and CRH particles. A three‐phase model was applied in a reverse mode, and the viscoelastic behavior of the interphase was extracted and compared with the unfilled matrix. Differential scanning calorimetry results indicated that CRH influences crystallization temperature as well as the degree of crystallinity of the composites. An entrapped polymer within CRH filler and PP matrix was detected by scanning electron microscope, which can be attributed to the interfacial layer with a good adhesion between the main components. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

An attempt to cast light into starch nanocrystals preparation and cross-linking

Potato starch was hydrolyzed with 2.2 or 3.7 M hydrochloric acid in order to obtain the nanocrystals which afterwards were chemically cross-linked with sodium hexametaphosphate. The stronger acidity resulted in smaller nanocrystals with mean size of 48 nm in a shorter time. X-ray diffraction confirmed the dominant crystalline nature of particles and Fourier transform infrared spectroscopy suggested the presence of lower number of free hydroxyl groups in nanocrystals after cross-linking. Starch nanocrystals showed two distinctive differential scaning colorimetry endotherms at 26 and 125 °C, attributed to destruction of nanocrystals lattice and moblizing of each nanocrystal’s structure, respectively. Cross-linking resulted in a tenacious spatial arrangement of nanocrystals, strengthening the crystals lattice against phase transitions induced by heating. Scanning electron microscopy images confirmed the particle size measured for nanocrystals by light scattering. Atomic force microscopy topographic images suggested that starch nanocrystals were originated from small amylopectin blocklets in granular assembly of starch.     

Morphological and rheological properties of (low‐density polyethylene)/thermoplastic starch blend: investigation of the role of high elastic network

Rheological and morphological properties of low‐density polyethylene (LDPE) and thermoplastic starch (TPS) with low‐density polyethylene‐grafted‐maleic anhydride as a compatibilizer were investigated. The results showed that the circularity of the droplets decreased with increasing TPS content. The presence of compatibilizer led to finer morphology and higher continuity. The rheological analyses showed that TPS and compatibilizer can increase elasticity and viscosity of the blend dramatically. In addition, the compatibilizer enhanced the compatibility of the blends, as evidenced by the shifting of the relaxation time peak of TPS to longer times. The rheological properties of the neat components and their blends were discussed by the Carreau‐Yasuda and fractional Zener models. The fractional Zener model results proved the existence of network structure in the compatibilized blends. The transient properties of blends showed that TPS and compatibilized blends had strong overshoot compared with the uncompatibilized blend, owing to the formation of high elastic network in their structure. J. VINYL ADDIT. TECHNOL., 20:250–259, 2014. © 2014 Society of Plastics Engineers     

Synthesis of clay–TiO2 nanocomposite thin films with barrier and photocatalytic properties for food packaging application

In this study, low‐density polyethylene (LDPE) nanocomposite films with two types of nanoparticles, TiO₂ (3 wt %) and Closite 20A (3 and 5 wt %), were prepared using a melt blow extrusion as an industrial method and their properties such as mechanical properties, water vapor, oxygen and carbon dioxide gas barrier, and antimicrobial activity were tested. Transmission electron microscopy (TEM) and X‐ray diffraction (XRD) were also performed to determine the degree of dispersion and exfoliation of nanoparticles. Mechanical test indicated that the reinforcement in the presence of the nanocomposites was more than that with their conventional counterparts, and the highest stiffness was achieved in a sample containing 5 wt % clay and 3 wt % TiO₂. Exfoliation of silicate layers and a good dispersion of TiO₂ nanoparticles in LDPE were achieved as confirmed by XRD and TEM. The gas barrier properties were improved after formation of the nanocomposites especially by insertion of 5 wt % of clay nanoparticles as a filler in the LDPE matrix. The photocatalytic effect of the nanocomposite film was carried out by antimicrobial evaluation against Pseudomonas spp. and Rhodotorula mucilaginosa and by ethylene removal test using 8 W ultraviolet (UV) lamps with a constant relative intensity of 1 mW cm^?2. The greatest effects were recorded by combining UVA illumination and active film. It was also proven that the photocatalyst thin film with improved barrier properties prepared by extrusion could be used in horticultural product packaging applications. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41764.     

Effect of microwave cooking on the microstructure and quality of meat in goat and lamb

Fat cell distribution in the structure of semimembranosus muscle of goat and lamb was studied. The effect of various heating methods including conventional, domestic and industrial microwave were investigated using fluorescent light microscopy. Frequency used for microwave heating was 2450 MHz with two wattages levels of 700 (domestic microwave) and 12000 (industrial microwave). All samples were heated to internal temperature of 70 °C. The roasted samples in conventional oven were compared with microwave cooking. Fat distribution was different in various heat treatments. The roasted samples had greater fat retention in semimembranosus muscle. Results showed that uneven distribution of fat in muscle system influenced fat loss during cooking. The fat cells in the interior of muscle were lost more slowly compared to the fat located near the surface of the muscle. The overall migration of fat globules during microwave cooking was higher than conventional cooking.