jrups
Abstract : Copper Ion Doped Mullite Composite in Poly (vinylidene Fluoride) Matrix: Effect on Microstructure, Phase Behavior and Electrical Properties
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Abstract: Highly crystallized copper ion doped mullite composites have been synthesized at 1100°C and 1400°C via sol-gel technique with five different strengths of copper ion and was incorporated in poly-vinylidene fluoride (PVDF) to make doped mullite composite/polymer films. We have studied the effects of this dopant on microstructure, phase transformation, and electrical properties of the polymer films over a wide range of frequency from 1.0 KHz to 2.0 MHz. Characterizations were done by various analytical tools at room temperature. Prominent mullite phases were observed from XRD, FTIR spectroscopy and FESEM characterization of composite polymer. The concentration of the dopant and the sintering temperature were found to be the two basic factors which affect the phase transition of the polymer. The composite film showed maximum dielectric constant of 19.96 at 1 KHz for 1.2M concentration of copper ion doped mullite sintered at 1400°C, compared to 3.09 for the pure polymer. Furthermore, both dielectric constant and electrical conductivity of the composite were found to be highly frequency and temperature dependent. After doping, the A.C. conductivity of the composite was found to increase with increasing temperature following Jonscher’s power law and the electrical resistivity reduced too. Moreover, the results revealed that the phase behaviors and micro structural changes of the copper ion doped mullite composite/polymer film affected its electrical properties with possible impact on its applications. Keywords: Polymer, Mullite, Sol–gel technique, XRD, FTIR, Dielectric properties, FESEM.Download Full Article |
Abstract : Mechanical Recycling of PET Waste from Non-Woven Fabrics by Reactive Extrusion with Chain Extenders
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Abstract: Mechanical recycling of poly (ethylene terephthalate) (PET) is an important industrial activity with direct effect for environmental saving. However, recycled PET (R-PET) undergoes progressive degradation during each recycling process, leading to considerable loss of properties such as mechanical, thermal and melting strength. Chain extenders have been successfully used to increase molecular weight of R-PET, improving process ability and mechanical performance of the material. The aims of this work was to evaluate the performance of the compounds polymeric methylene diphenyldiisocyanate (PMDI) and bis-(2,4-di-t-butylphenol) pentaerythritoldiphosphite (Irgafos®126) for potential use as chain extenders when compared to the traditional chain extender pyromelliticdianhydride (PMDA). Tensile testing, differential exploratory calorimetry, viscometry and dynamic rheometry were used to evaluate changes in mechanical properties, crystallinity, molecular weight and rheological properties of R-PET. PMDI showed effective action on increase in molecular weight and improvements in mechanical and rheological properties of R-PET, while Irgafos 126 causes depreciation of properties of the R-PET after initially to increase the molecular weight of the polymer. Thus, the use of PDMI as chain extension can represent an important alternative for mechanical recycling of highly degraded PET. Keywords: PET, recycling, diisocyanate, phosphite, PMDA, chain extender.Download Full Article |
Abstract : Mechanism of Micro-Crack Propagation in Semicrystalline Polymers
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Abstract: The development and propagation of cracks is the principle reason for premature mechanical failure of polymeric materials. The well known and widely accepted fracture theories, namely the Griffith fracture theory and the Irwin model, both assume that fracture takes place through the presence of preexisting cracks in the polymer. These minor preexisting cracks, or micro-cracks, are practically present in most polymeric samples. The Griffith approach assumes that for any particular material, the fracture stress is controlled by the size of the flaws present in the structure. The control and minimization of micro-crack size during polymer processing requires an understanding of the inherent micro-crack propagation mechanism. The present research reveals a mechanism of internal stress-induced micro-crack propagation in semicrystalline polymers and describes the effect of the intricate crystalline morphological interactions on the extent and direction of intra-spherulite and inter-spherulite micro-crack propagation. In conclusion, a method for minimizing inter-spherulite micro-crack propagation is presented in this article. Keywords: Crystalline morphology, fracture, micro-cracks, internal stress, high -density polyethylene (HDPE). Download Full Article |
Abstract : Delamination and Separation of Aluminum-Polyethylene-Paper Packing Material
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Abstract: Delamination and separation of laminated aluminum- polyethylene-paper packaging material were conducted for recycling packaging materials. Delamination was carried out using glacial acetic acid (GAA) solution. L9 (34) orthogonal experiments demonstrate that the most significant factor is GAA concentration followed by temperature and liquid/solid ratio. The delamination time decreased sharply with increasing temperature and the GAA concentration. The packaging material was delaminated under conditions of 60 ˚C, 70 v% GAA solution, liquid/solid ratio 20:1 and delamination time 60 min, and separation of polyethylene, paper and aluminum foil was conducted through sink-float method and air separation. Polyethylene, paper and aluminum foil were separated efficiently. The recovery and purity of aluminum foil was 90.81% and 100%, respectively; the purity of polyethylene was 100%; the recovery and purity of paper was 100% and 96.03%, respectively. This study offers some technical insights for recycling of aluminum-plastic packaging. Keywords: Delamination, separation, aluminum, polyethylene, packaging material.Download Full Article |
Abstract : Nanoencapsulation of Antitumor and Antituberculosis Drug Preparations with Biocompatible Polymers
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Abstract: Controlled release of drugs at the locus of the targeted disease is one of the most challenging research areas in the pharmaceutical field. Nowadays novel drug delivery systems on the basis of polymers are attracting great attention since they can improve therapeutic efficiency of potent drug preparations decreasing the risk of side effects. By developing colloidal drug delivery systems such as liposomes/vesicles and polymeric nanoparticles and nanocapsules the pharmacokinetics of the drug can be changed and thus the therapeutic efficiency of the drug can be increased. Nanoparticles with their special characteristics such as small particle size, large surface area and high capacity of carrying biologically active substances offer a number of advantages compared to other colloidal drug delivery systems [1, 2]. Controlled drug release systems are constructed on the basis of natural and biocompatible synthetic polymers. Among the most promising biocompatible polymers human serum albumin (HSA), polyalkyl cyanoacrylates (PACA) and poly-D,L-lactic acid (PLA) are of great importance. Nanoparticles on their basis have been proven to be efficient in treatment of serious and long-termed diseases such as tumors, tuberculosis and bacterial infections [3-126]. Therefore this article is aimed to give a brief review on the research works devoted to the synthesis and investigation of polymeric nanoparticles and nanocapsules based on PACA, HSA and PLA for the past three decades. Keywords: Drug delivery systems,nanoparticles, nanocapsules, polyalkyl cyanoacrylates, human serum albumin, poly-D,L-lactic acid. Download Full Article |