Poly(vinyl chloride)/Metallic Oxides/Organically Modified Montmorillonite Nanocomposites: Fire and Smoke Behavior

Nanocomposites of poly(viny] chloride), metallic oxides (copper, molybdenum, and zinc), and organically modified montrnoriflonite (O-MMT) were prepared in a melt-blending or intercalation-in-the-molten state process, and their morphology was assessed with X-ray diffraction and transmission electron microscopy. The formation of an intercalated/partially exfoliated hybrid microstructure was confirmed in every situation studied. The combustion and smoke emission properties were studied with cone calorimetry, limiting oxygen index, and thermogravimetry (TG) coupled with mass spectroscopy (MS). The results reveal that the metallic oxides had a significant effect on both the combustion properties and smoke suppression, whereas O-MMT only affected these properties discretely. Little interaction was observed in the joint use of these additives. The results also confirm the anticipation of dehydrochlorination, reductive coupling, and benzene suppression mechanisms resulting from the presence of copper, molybdenum, and zinc metals; these were indicated by the increase in carbonaceous char residue and the significant reduction in benzene formation, in this case indicated in the TG/MS measurements obtained. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 116: 946-958, 2010116294695

Metallic Oxides as Fire Retardants and Smoke Suppressants in Flexible Poly(Vinyl Chloride)

Combustion and smoke emission properties of PVC compounds, modified with copper (II), molybdenum, and zinc oxides, were studied using cone calorimeter, limiting oxygen index (LOT) and thermogravimetry coupled with mass spectrometry (TG/MS). Results showed that the metal oxides have a very significant effect on the combustion and smoke suppression properties of the PVC compounds. The results also confirmed the anticipation mechanisms of the dehydrochlorination reactions, reductive coupling, and elimination of benzene resulting from the presence of copper (II), molybdenum, and zinc, indicated by the increasing content of postcombustion char residue and the significant reduction in benzene production, indicated by the MS measurements performed. The results also provide indications that the combination of the copper (II) and molybdenum oxides is the one with the best balance of combustion properties, as it reduced the heat released and promoted the suppression of smoke more efficiently. The formulations containing ZnO, because of their strong Lewis acid character, indicated a less pronounced reduction of smoke released during the combustion process, when compared with copper (II) and molybdenum oxides. (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 118: 2613-2623, 2010118526132623Braskem S/

NON-WOVEN NANOFIBER CHITOSAN/PEO MEMBRANES OBTAINED BY ELECTROSPINNING

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)The present work focused on the preparation and morphological characterization of chitosan-based nanofiber membranes, aiming at applications in medical and pharmacological areas. Membranes with nanofiber diameters ranging from 50 - 300 nm were prepared from polymer solutions through the electrospinning process. To stabilize the process, it was necessary to use poly(ethylene oxide) (PEO), which is a biocompatible synthetic polymer. Pure chitosan solutions, as well as chitosan and PEO solution blends, were characterized by their rheological behavior, conductivity, and surface tension measurements. The electrospun fiber thermal characteristics and crystalline structures were investigated through thermogravimetric analysis (TG) and differential scanning calorimetry (DSC). Scanning electron microscopy images (SEM) were used for the morphological evaluations of the membranes. The addition of PEO to the chitosan solutions improved their electrical conductivity, surface tension and viscosity, greatly favoring the electrospinning process. Thus, membranes with 80% chitosan could be electrospun.3115768Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)CNPq [p. 140146/2008-3

Synthesis and characterization of chitosan-PHB blends

The blends were obtained using trifluoracetic acid as co-solvent under continue stirring at room temperature. Chitosan was obtained from shrimps shells of (M) over barv = 81,430 Daltons and 91% deacetylation degree, DS, was used. The PHB comes from biological fermentation process (Copersucar, Sao Paulo, Brazil) and their (M) over barv = 183,200 Daltons. The elastomeric products were characterized by elemental analyses, thermogravimetry, FT-IR and SEM.47452953

The use of differential photocalorimetry to measure the oxidation induction time of isotatic polypropylene

The widespread use of polymeric materials in many applications requires polymers which are weather resistant. The aim of this study is to examine the usefulness of oxidation induction time (OIT) measurements by differential photocalorimetry (DPC) as a tool for evaluating the ultraviolet (UV) stability of isotatic polypropylene (PPi). DPC was used to measure OIT in PPi formulations containing different concentrations of light and thermal stabilizers. The OIT was measured with and without UV light incidence and the results were compared with the appearance of cracks seen with an optical microscopy, after aging in a Weather-Ometer. The measures of OIT with UV light showed values 25-60% smaller than the values of OIT without light, for different formulations. In this paper, these OIT results will be discussed. (C) 2003 Elsevier Ltd. All rights reserved.23446146

Use of oxidation onset temperature measurements for evaluating the oxidative degradation of isotatic polypropylene

The widespread use of polymeric materials in many applications requires polymers that are weather resistant. The aim of this study is to examine the usefulness of oxidation onset temperature measurements as a tool for evaluating oxidative degradation of isotatic polypropylene. Differential scanning calorimetry was used to measure the oxidation onset temperature in formulations of isotatic polypropylene containing different concentrations of light and thermal stabilizers after aging in a Weather-Ometer. Oxidation onset temperature gave better results than oxidation induction time for evaluating the degradation of isotatic polypropylene during aging in a Weather-Ometer. However, both tests showed a poor correlation with the appearance of cracks seen by optical microscopy.121111

PLA and Montmorilonite Nanocomposites: Properties, Biodegradation and Potential Toxicity

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)The concern related to solid waste increases efforts to develop products based on biodegradable materials. At present, PLA has one of the highest potentials among biopolyesters, particularly for packaging. However, its application is limited in some fields. In order to optimize PLA properties, organo-modified montmorilonites have been extensively used to obtain nanocomposites. Although PLA nanocomposites studies are widely reported in the literature, there is still few information about the influence of organoclays on de biodegradation process, which is a relevant information, since one of the main purposals related to the final disposal of biopolymers as PLA is composting. Besides, in the last years some research has been conducted in order to evaluate the potential toxicity of montmorilonite, unmodified or organo-modified. Since the use of montmorilonite is expanding in different applications, human exposure and risk assessment are important issues to be investigated. In this context, this review intends to compile available information related to common organoclays used for PLA nanocomposites, its properties, biodegradation analysis and potential toxicity evaluation of nanocomposites, focused on montmorilonite as filler. Two issues of relevance were pointed out. The first is food safety and quality, and the second consideration is the environmental effect.213738759Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)FAPESP [2011/14250-3, 2012/00227-2

Properties that characterize the propagation of cracks of recycled glass fiber reinforced polyamide 6

Industrial wastes of glass fiber reinforced polyamide 6 originating from injection molding were reprocessed and characterized by measurements of relative viscosity, impact strength, fiber average length and fiber length distribution. The results show that the set of characterization techniques used are efficient to reproduce the behavior of reprocessed polymeric composites and to compare them with the virgin material. (C) 1999 Elsevier Science Ltd. All rights reserved.18321121

The influence of the drying process time on the final properties of recycled glass fiber reinforced polyamide 6

Polyamides are intrinsically hygroscopic because of the polar nature of their chains, which make them moisture sensitive materials, and hence chemically unstable towards hydrolytic conditions. Prior to processing steps, polyamide composites need to be dried in order to attain their good mechanical properties afterwards. Nevertheless, polyamide based materials may undergo discoloration and sonic deterioration after long drying periods. Industrial wastes consisting of glass fiber reinforced polyamide 6 (PA 6) composite were dried for 3, 6 and 9 h before reprocessing. The reprocessing of this type of composite was shown to be quite viable, because satisfactory physical-mechanical properties are attained thereafter, which make them suitable for several applications where these properties are desirable. (C) 2001 Elsevier Science Ltd. All rights reserved.21222923

Water and drug transport in radiation-crosslinked poly(2-methoxyethylacrylate-co-dimethyI acrylamide) and poly(2-methoxyethylacrylate-co-acrylamide) hydrogels

Hydrogels of poly(N,N'-dimethylacrylamide-co-2-methoxyethylacrylate) and poly(acrylamide-co-2-methoxyethylacrylate) have been synthesized by radiation polymerization in dimethylformamide solution with trimethylolpropane trimethacrylate as a crosslinker. In this work, some investigations on the in vitro release of gentamicin sulphate, an antibiotic entrapped in the hydrogels, are reported. The kinetics of drug release from hydrogels matrices were examined and the results indicate that the release for the proposed geometry practically occurs in the first 24 h. The fractional cumulative release of the drug from the DMAA/MOEA matrices is linear when plotted against the square root of time, pointing out a Fickian process. On the other hand, AAm/MOEA matrices showed an initial non-Fickian behaviour, probably indicating a comparable rates of Fickian diffusion and polymer relaxation. (C) 2003 Elsevier Science Ltd. All rights reserved.66215515