Ultrasound-assisted synthesis of polyacrylamide-grafted sodium alginate and its application in dye removal

A polymeric adsorbent based on sodium alginate (SAG) grafted with polyacrylamide (PAM) (SAG-g-PAM) was synthesized using an ultrasound-assisted method. The addition polymerization was carried out with ammonium persulfate as the initiator, at different acrylamide (AM) concentrations. The SAG-g-PAM copolymers were evaluated by FTIR and 13C NMR spectroscopies, thermogravimetric analysis, grafting efficiency (%GE) and intrinsic viscosity in NaCl solution at 25 °C. Graft copolymers could be obtained in reaction lasting until 10 min by using ultrasound energy with grafting efficiency above 75%. The decolorization efficiency and adsorption capacity of the SAG-g-PAM copolymers were investigated in the adsorption of methylene blue (MB). The dye adsorption was pH dependent, and adsorption capacity (69.13 mg/g) maxima was at pH 10. All the graft copolymers have shown the same decolorization efficiency (99%), and the best one for MB removing is the SAG-g-PAM6 (%GE = 75%), since lower acrylamide content is required in the synthesis

Biodegradation of PP films modified with organic pro-degradant : natural ageing and biodegradation in soil in respirometric test

In this study, PP films were modified with an organic pro-degradant in different concentrations (1, 2 and 3 wt.%), exposed in the first step of degradation to natural ageing for 100 days followed by biodegradation in simulated soil in the respirometric test for 100 days. At the end of the combined degradation process the PP samples were characterized according to their morphological and physical properties and the CO2 generated during the biodegradation in soil was monitored. The CO2 production by the PP films modified with the organic pro-degradant was proportional to the oxidation rate and weight loss of the samples. The reduction in the average viscosimetric molecular weight could be attributed to chain scission due to the weathering conditions to which the samples were exposed (natural ageing followed by biodegradation in soil). Scanning electron microscopy (SEM) of the PP films revealed surface deterioration of the films with the organic pro-degradant after the combined degradation process

Comparative study of degradation of PP modified with an organic pro-degradant subjected to natural and artificial ageing

In abiotic degradation the action of light radiation is one of the most important parameters, because polymers undergo degradation due to the action of light (natural or artificial). The aim of this study was to investigate the degradation rate for samples of polypropylene (PP) modified with an organic pro-degradant submitted to ageing in a natural environment and to accelerated ageing test. The degradation behavior of the samples exposed to the ageing processes was evaluated through changes in the degree of crystallinity (Xc), surface morphology (Scanning Electron Microscopy) and molecular weight. The results indicated that for the modified polypropylene samples natural ageing led to a 42.3% reduction in the molecular weight and the surface morphology showed evidence of erosion. In the accelerated ageing process the UV radiation was stronger, which led to a 94.3% increase in the degree of crystallinity and micro-voids were present on the surface of the modified polypropylene

Rheological behavior and morphological and interfacial properties of PLA/TPE blends

Rheological and interfacial tension data were employed to predict the morphology and thermal and mechanical properties ofnoncompatibilized and compatibilized poly(lactic acid) (PLA)/thermoplastic elastomer (TPE) blends. PLA was melt blended with thermo-plastic polyurethane (TPU) and ethylene elastomer (EE) and compatibilized by ethylene–butyl acrylate–glycidyl methacrylate (EBG) in aninternal mixer chamber. Both TPU and EE TPEs have higher viscosities than PLA, and the interfacial properties evaluated have revealedbetter adhesion between domains of PLA–TPU. The efficiency of the compatibilizer agent EBG depended on the TPE type inferred bymodifications in the scanning electron microscopy images of PLA/TPE blends and by the Izod impact strength (improved by 23%). TheEBG was more effective in the PLA/TPU blend. The TPEs and EBG did not affect the PLA thermal stability, and no thermal event wasobserved in the usual PLA extrusion and injection temperature range

Nafion/sulfonated poly(indene) polyelectrolyte membranes for fuel cell application

Sulfonated poly(indene) (SPInd), with 35% and 45% degree of sulfonation, was blended with Nafion to prepare blended membranes with 10, 15 and 20 wt.% of SPInd. Membranes were evaluated by infrared spectroscopy, thermogravimetric analysis, differential scanning calorimetry, scanning electron microscopy and X-ray diffraction. Water uptake (WU), ion exchange capacity (IEC) and through-plane proton conductivity were measured. The membranes presented similar thermal stability to Nafion. WU was slightly higher for Nafion/SPInd membranes (19-21% at RT and 40-44% at 90 °C) compared with recast Nafion (16% and 34%, respectively), and IEC values showed a similar trend. Blended Nafion membranes had increased proton conductivity of 2.41 x 10-2 and 2.37 x 10-2 Scm-1 (20 wt. % of SPInd 35% and 45%, respectively), compared with 1.16 x 10-2 Scm-1 for recast Nafion. The results show that the addition of SPInd to Nafion is a potential route towards improving the performance of Nafion in proton conductivity for use in fuel cells devices

Influence of the morphology and viscoelasticity on the thermomechanical properties of poly(lactic acid)/thermoplastic polyurethane blends compatibilized with ethylene‐ester copolymer

Viscoelastic, interfacial properties, and morphological data were employed to predict the thermal and mechanical properties of compatibilized poly(lactic acid) (PLA)/thermoplastic polyurethane (TPU) blends. The combination of interfacial thickness measured by contact angle and entanglement density determined by dynamical mechanical analysis analyze data was employed to evaluate the mechanical behavior of PLA/TPU blends with and without ethylene‐butyl acrylate‐glycidyl methacrylate (EBG) compatibilization agent. The PLA/TPU blend (70/30 wt %) was prepared in a Haake internal mixer at 190 °C and compatibilized with different contents of EBG. The evaluation of the interfacial properties revealed an increase in the interfacial layer thickness of the PLA/TPU blend with EBG. The scanning electronic microscopy images showed a drastic reduction in the size of the dispersed phase by increasing the compatibilizer agent EBG content in the blend. The compatibilization of the PLA/TPU blends improved both the Izod impact strength and yield stress by 38 and 33%, respectively, in comparison with neat PLA/TPU blend. The addition of EBG into PLA/TPU blends significantly increased the entanglement density and the PLA toughening but resulted in a decrease of PLA deformation at break. The PLA and TPU glass transitions were affected by the EBG, suggesting that the PLA and TPU domains were partially miscible

Estudo da degradação térmica do copolímero tribloco estireno-butadieno-estireno (SBS) utilizado na modificação de asfalto

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