Layered double hydroxide-based nanocomposite scaffolds in tissue engineering applications

Layered double hydroxides (LDHs), when incorporated into biomaterials, provide a tunable composition, controllable particle size, anion exchange capacity, pH-sensitive solubility, high-drug loading efficiency, efficient gene and drug delivery, controlled release and effective intracellular uptake, natural biodegradability in an acidic medium, and negligible toxicity. In this review, we study potential applications of LDH-based nanocomposite scaffolds for tissue engineering. We address how LDHs provide new solutions for nanostructure stability and enhance in vivo studies\u27 success

Building a Time Server with RaspberryPI & GPS, Connecting with a Free Web GIS Software

In this study, we have organized a revival project for Time Synchronization and used a Raspberry PI & GPS Module to capture The GPS Signal and parsed the Signal for building NTP Server. After building NTP Server, we are going to make a GPS handset by adding touch screens to our Raspberry Pis and we\u27re going to use this handset for locating the trees at the Kandilli Observatory and Earthquake Research Institute Campus. At the end, collected the data will be used at the free and open source web GIS software for our project

Synthesis and film properties of epoxy esters modified with amino resins from glycolysis products of postconsumer PET bottles

Glycolysis of waste polyethylene terephthalate (PET) flakes obtained from grinding postconsumer bottles was carried out at 225-250 degrees C and molar ratios of PET/ethylene glycol were taken as 1/1, 1/1.5, 1/5, and 1/10. Reaction product was extracted by hot water for three times and water-soluble crystallizable fraction and water-insoluble fraction were obtained. These fractions were characterized by acid and hydroxyl value determinations, differential scanning calorimeter analysis, and H-1-NMR analysis. Glycolysis product was used for synthesis of PET-based epoxy resin. This epoxy resin was used to prepare epoxy ester resins having 40% and 50% oil content. Epoxy ester resin having 40% oil content was modified with urea-formaldehyde and melamine-formaldehyde resins for synthesis of epoxy ester-amino resin. Physical and chemical film properties of epoxy ester and modified epoxy ester resins were investigated. All the epoxy ester and modified epoxy ester films were having excellent adhesion, water, and salt water resistance properties. Modification of PET-based epoxy ester resins with amino resin has significantly improved hardness, impact resistance, and alkaline and acid resistance of resin films. As a result, PET oligomers obtained from glycolysis of postconsumer PET bottles are suitable for manufacturing of amino-resin-modified epoxy ester resins that have improved physical and chemical surface coating properties. POLYM. ENG. SCI., 55:2519-2525, 2015. (c) 2015 Society of Plastics Engineer

The use of intermediates obtained from aminoglycolysis of waste poly(ethylene terephthalate) (PET) for the synthesis of water-reducible alkyd resin

In this study, depolymerization products obtained from an aminoglycolysis reaction of postconsumer poly(ethylene terephthalate) (PET) bottles were used for the synthesis of water-reducible alkyd resins for the first time. We also aimed to reduce the amount of amine using aminoglycolysis products of PET having amine end groups for the neutralization of alkyds in this work. Alkyds formulated to have an oil content of 50% were prepared with glycerine (G), ethylene glycol (EG), fatty acid (FA), and phthalic anhydride (PA) or aminoglycolysis depolymerization products (ADP). The "K alkyd constant system" was used for the formulation calculations of the alkyd resins. The K constant was 1.1 and the ratio of basic equivalents to acid equivalents (R) was 1.15. Physical and chemical film properties and thermal degradation stabilities of these alkyd resins were investigated. According to the results of surface coating tests, the properties of the waste PET-based alkyd resins were found to be compatible with the properties of the reference resins. In addition, thermal degradation stabilities of the water-reducible alkyd resins prepared by ADP were better than that of the reference resin. As a result, we concluded that aminoglycolysis products of waste PET are suitable for manufacturing water-reducible alkyd resins. Furthermore, the amount of amine used for the neutralization stage of preparing water-reducible resin was reduced by 50% using aminoglycolysis products having an amine end group

Preparation and characterization of pH responsive poly(methacrylic acid-acrylamide-N-hydroxyethyl acrylamide) hydrogels for drug delivery systems

In this study, pH responsive polymers composed of methacrylic acid, acrylamide, and N-hydroxyethyl acrylamide were synthesized by free radical polymerization technique. The characterization was done with Fourier transform infrared spectroscopy and scanning electron microscopy. The swelling and drug release behavior of the hydrogels was determined as a function of time at 37 degrees C in pH 2.1 and 7.4. The swelling and drug release studies showed that increased methacrylic acid amount caused a higher increase in swelling and drug release values at pH 7.4 than those at pH 2.1. In addition, the drug release data were applied to kinetic models such as zero order, first order, and Higuchi equations, and it fit well in the Higuchi model of the hydrogel. (c) 2015 Wiley Periodicals, Inc

Characterization of the thermal oxidative degradation kinetics of thermoplastics

Thermal oxidative degradation kinetics of polyethylene, poly(ethylene terephthalate), and polystyrene were investigated by thermogravimetric analysis. The samples included low-density polyethylene, medium-density polyethylene, high-density polyethylene, a starch-based biodegradable thermoplastic polyester, polyethylene natural gas pipe, a poly(ethylene terephthalate) water bottle, and a polystyrene drinking cup. The kinetics were conducted under dynamic conditions at heating rates of 10, 20, 30, and 40 degrees C min(-1) between 25 and 650 degrees C in air. The Kissinger, Flynn-Wall-Ozawa, and Coats-Redfern methods were used for investigation of degradation of these polymers. Thermal oxidative degradation of the polymers was compared. Low-density polyethylene, medium-density polyethylene, high-density polyethylene, and polyethylene pipe obeyed a diffusion mechanism for oxidative thermal degradation. The starch-based biodegradable thermoplastic polyester, polystyrene cup, and poly(ethylene terephthalate) bottle followed random nucleation, diffusion, and phase boundary-controlled reaction mechanisms, respectively

The Effect of Xylene as Aromatic Solvent to Aminoglycolysis of Post Consumer PET Bottles

This study deals with the use of ethylene glycol and diethylamine for the aminoglycolytic degradation of waste poly(ethylene terephthalate) (PET). Our aim is to investigate how the product composition changes according to depolymerization conditions and to obtain oligomer mixtures having different properties. For this purpose, simultaneous aminolysis-glycolysis reactions of postconsumer soft-drink PET bottles were carried out in a high pressure reactor with or without xylene. As a result, the oligomer mixtures having carboxyl, hydroxyl, and amine end groups were obtained at the end of the aminoglycolysis of PET. All products were characterized by acid value, hydroxyl value, and amine value determinations as well as by Fourier Transform Infrared Spectroscopy and Differential Scanning Calorimeter. Use of xylene has provided initially easily mixable low viscosity dispersions and depolymerization reactions proceeded more easily. It also provided water soluble and lower molecular weight oligomers with deep depolymerization of PET in the presence of xylene. In case of using xylene, glycolysis reaction was dominant reaction rather than aminolysis and hydrolysis. Functional oligomer mixtures obtained from degradation of waste PET can be used for synthesis of coating materials, such as water reducible alkyd resins and epoxy resins. POLYM. ENG. SCI., 53:2429-2438, 2013. (c) 2013 Society of Plastics Engineer

A novel type nanocomposite coating based on alkyd-melamine formaldehyde resin containing modified silica: Preparation and film properties

In this study, the surface of the silica particles was modified with glycidoxypropyl trimethoxysilane and then silica nanoparticle modified alkyd-melamine resins were synthesized by two methods, namely in situ (IS) polymerization and blending (BL) methods. After alkyd resins containing 40% oil were prepared; these resins were blended with 30% of a commercial melamine-formaldehyde. The films of the alkyd-melamine formaldehyde resins were prepared from 60% solid content in xylene solutions. These films were cured at 170 degrees C and properties of the films were determined. The effect of modified silica on the film properties and thermal behaviors of the resins was investigated. The scanning electron micrographs of the nanocomposite resin showed that modified silica particles have been dispersed into polymer resins substantially for IS polymerization. According to results of surface coating tests, we can say that, film properties of the resins prepared by IS method were better than that of prepared by BL method. In addition, using modified silica did not have a negative effect on the thermal behaviors of the resins with respect to thermogravimetric analysis. Furthermore, adding the modified silica in the resin structure caused increasing the thermal stability especially for resins prepared by IS method. As a result, alkyd-melamine resins containing modified silica nanoparticle are suitable for manufacturing of industrial baking enamels. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 201

THERMAL OXIDATIVE DEGRADATION KINETICS OF NANOCOMPOSITE ALKYD-MELAMINE FORMALDEHYDE RESIN CONTAINING MODIFIED SILICA

Thermal oxidative degradation kinetics of a nanocomposite alkyd-melamine formaldehyde resin containing surface-modified silica were investigated by thermogravimetric analysis. For this goal, the surface of the silica nanoparticles was modified with glycidoxypropyl trimethoxysilane. Afterwards, a nanocomposite alkyd-melamine formaldehyde resin containing 3% (wt.) ratio of surface modified silica was prepared by an in situ polymerization method. The degradation kinetics of this resin were investigated using different methods. The activation energies of different mechanism models were determined by the Coats-Redfern method. It was concluded that the actual reaction mechanism obeyed three-dimensional diffusion compared with the values obtained from the Kissinger and Flynn-Wall-Ozawa methods

HYDROXYL-FUNCTIONALIZED HYPERBRANCHED ALIPHATIC POLYESTERS BASED ON 1,1,1-TRIS(HYDROXYMETHYL)PROPANE (TMP) AS A CORE MOLECULE: SYNTHESIS AND CHARACTERIZATION

The aim of this study is to synthesize and characterize the new hydroxyl-functionalized hyperbranched aliphatic polyesters with various generations for potential use in cancer therapy as targeted drug delivery system. For this purpose, a series of novel hydroxyl-functionalized hyperbranched aliphatic polyesters (HBPs) based on 2,2-bis(hydroxymethyl) butyric acid (Bis-HBA) as AB2-type monomer and 1,1,1-tris(hydroxymethyl) propane (TMP) as B3 core molecule were synthesized via acid catalyzed polyesterification reaction in three different generations and named as HBP-2G, HBP-4G and HBP-5G. The synthesis route was a simple pseudo-one-step reaction where AB2-type monomer and B3 core molecule are polycondensed in the presence of an acid catalyst. The chemical structures of the synthesized HBPs were confirmed by FTIR, C-13 NMR and H-1 NMR analysis. The degree of branching (DB) of the HBPs as calculated from H-1 NMR results were between 0.87 and 0.92. These results showed that all synthesized HBPs had a high degree of branching. TGA measurements exhibited that all of HBPs had similar and good thermal stability. Glass transition temperatures (Tg) of samples were identified using DSC analysis and were found to be between 66.2 degrees C and 69.1 degrees C. Low generation HBPs have considerably higher solubility in organic solvents than high generation HBPs. All synthesized HBPs displayed extremely low water solubility but extremely high solubility in dimethyl sulfoxide. It was concluded that new HBPs which were synthesized in this study have reasonable characteristics for hyperbranched polymers applications