Fire Retardancy of Melamine and Zinc Aluminum Layered Double Hydroxide in Poly(methyl Methacrylate)

The thermal and fire properties of PMMA modified with various loadings of melamine or zinc aluminum undecenoate LDH were evaluated using TGA, DTA and cone calorimetry. The additives were characterized by X-ray diffraction, TGA, FT-IR and elemental analysis. While the two additives are very effective with this polymer, a higher loading of melamine (30%) is required to reach a good reduction in PHRR (47%) relative to the pure polymer, while with the LDH, 10% loading is enough to obtain a similar reduction. The combinations of these additives in PMMA reveal that the time to PHRR and the amount of smoke produced are the key differences, with melamine increasing the first parameter and leading to less smoke production relative to LDH-rich PMMA systems at similar total additive loadings. Analysis of the residue shows that melamine is completely lost during combustion while the LDH forms ZnO and ZnAl2O4

Comparative Study on the Flammability of Polyethylene Modified with Commercial Fire Retardants and a Zinc Aluminum Oleate Layered Double Hydroxide

Polyethylene (PE) was modified by the addition of a layered hydroxide of zinc aluminum oleate (ZnAl) and/or commercial fire retardants. Commercial additives included: melamine polyphosphate (MPP), ammonium polyphosphate (APP), triphenol phosphate (TPP), resorcinol diphosphate (RDP), decabromophenyl oxide (DECA) and antimony oxide (AO). The thermal stability and the combustion behaviors of the new composite polymeric materials are evaluated in TGA experiments and cone calorimetry. At 20% total additive loading, APP and LDH enhance the thermal stability of the PE composites and favor char formation. ZnAl leads to the best reduction in the peak of heat release rate (PHRR), 72%, while the combinations of PE with other additives give reductions in the range 20-40%. The combination of DECA and AO effectively increases the time to ignition and time to PHRR while LDH lowers these two Phosphate fire retardants parameters. APP and MPP on the other hand, do not affect the time to ignition, but they effectively increase the time to PHRR relative to the pristine polymer

The Role of the Trivalent metal in an LDH: Synthesis, Characterization and Fire Properties of Thermally Stable PMMA/LDH Systems

Two layered double hydroxides (LDHs), calcium aluminum undecenoate (Ca3Al) and calcium iron undecenoate (Ca3Fe), have been prepared by the co-precipitation method. XRD analysis of these LDHs reveals that they are layered materials and FT-IR and TGA confirmed the presence of the undecenoate anions in the material produced. The PMMA composites were prepared by bulk polymerization and the samples were characterized by XRD, TEM, TGA and cone calorimetry. Both additives greatly enhance the thermal stability of PMMA, while the calcium aluminum LDH gives better results when the fire properties were examined using the cone calorimeter

Aluminum-containing Layered Double Hydroxides: the Thermal, Mechanical, and Fire Properties of (Nano)composites of Poly(methyl Methacrylate)

Hydrotalcite-like anionic clays or layered double hydroxides (LDHs) of the general formula, [MII1-xMIIIx(OH)2]intra[(CH2=CH(CH2)8COO-)x•nH2O]inter, with MIII = Al and MII = Co, Ni, Cu, and Zn, have been prepared by the co-precipitation method and used to prepare nanocomposites with poly(methyl methacrylate) (PMMA). One goal of this work was to compare the morphology, thermal, fire and mechanical properties with those of the well known PMMA–montmorillonite system. The thermal properties of these systems are greatly improved relative to the virgin PMMA, with ZnAl2 and CoAl2 being the best systems when 50% mass loss is the point of comparison. NiAl2, on the other hand, is more thermally stable when 10% mass loss was the point of comparison. The mechanical properties, such as Young’s Modulus and elongation, were not significantly impacted by nanocomposite formation. The cone calorimetric results showed that the PMMA–CoAl2 system gives the best reduction (41%) in peak heat release rate (PHRR); this value is significantly larger than that seen for the PMMA–montmorillonite system. Small improvements were observed for the nickel-containing LDH with the same polymer. XRD of the char produced in the cone calorimeter, and after heating to 1000 °C, suggest the formation of a mixture of the spinel and the MII oxide for Zn, Cu and Ni systems while only the spinel was identified in the case of PMMA–CoAl2 systems

Polymer Nanocomposites Using Zinc Aluminum and Magnesium Aluminum Oleate Layered Double Hydroxides: Effects of LDH Divalent Metals on Dispersion, Thermal, Mechanical and Fire Performance in Various Polymers

Oleate-containing layered double hydroxides of zinc aluminum (ZnAl) and magnesium aluminum (MgAl) were used to prepare nanocomposites of polyethylene, poly(ethylene-co-butyl acrylate) and poly(methyl methacrylate). The additives and/or their polymer composites were characterized by X-ray diffraction, FTIR, elemental analysis, thermogravimetric analysis, mechanical testing, and cone calorimetry. The unusual packing of the monounsaturated oleate anions in the gallery of these LDHs facilitates the dispersion of these nanomaterials. The inorganic LDH protects the polymer from thermal oxidation, shown by enhancement of the thermal and fire properties of the corresponding polymer nanocomposites. There is a qualitative difference in the morphology of the two LDHs in PE and PMMA. ZnAl is better dispersed in PE while MgAl is better dispersed in PMMA. The zinc-containing material led to a large reduction in the peak heat release rate in polyethylene, while the magnesium-containing material led to enhancement of the fire properties of the more polar poly(methyl methacrylate). These fire properties are consistent with the morphological differences. Neither of these LDHs shows efficacy with poly(ethylene-co-butyl acrylate), which indicates a selective interaction between the LDH and the various polymers

Evaluating process and clinical outcomes of a primary care mental health integration project in rural Rwanda: a prospective mixed-methods protocol

Introduction: Integrating mental healthcare into primary care can reduce the global burden of mental disorders. Yet data on the effective implementation of real-world task-shared mental health programmes are limited. In 2012, the Rwandan Ministry of Health and the international healthcare organisation Partners in Health collaboratively adapted the Mentoring and Enhanced Supervision at Health Centers (MESH) programme, a successful programme of supported supervision based on task-sharing for HIV/AIDS care, to include care of neuropsychiatric disorders within primary care settings (MESH Mental Health). We propose 1 of the first studies in a rural low-income country to assess the implementation and clinical outcomes of a programme integrating neuropsychiatric care into a public primary care system. Methods and analysis A mixed-methods evaluation will be conducted. First, we will conduct a quantitative outcomes evaluation using a pretest and post-test design at 4 purposively selected MESH MH participating health centres. At least 112 consecutive adults with schizophrenia, bipolar disorder, depression or epilepsy will be enrolled. Primary outcomes are symptoms and functioning measured at baseline, 8 weeks and 6 months using clinician-administered scales: the General Health Questionnaire and the brief WHO Disability Assessment Scale. We hypothesise that service users will experience at least a 25% improvement in symptoms and functioning from baseline after MESH MH programme participation. To understand any outcome improvements under the intervention, we will evaluate programme processes using (1) quantitative analyses of routine service utilisation data and supervision checklist data and (2) qualitative semistructured interviews with primary care nurses, service users and family members. Ethics and dissemination This evaluation was approved by the Rwanda National Ethics Committee (Protocol #736/RNEC/2016) and deemed exempt by the Harvard University Institutional Review Board. Results will be submitted for peer-reviewed journal publication, presented at conferences and disseminated to communities served by the programme

Avaliação da habilidade do modelo WRF em representar a precipitação na amazônia usando diferentes escalas

Precipitation over the northern Amazon during the austral summer and autumn seasons of the 1988-1999 was simulated using the Regional Weather Research and Forecasting (WRF) model, with downscaling approach with nested domains of 45 and 15 km. The boundary and initial conditions were obtained from the Climate Forecast System Reanalysis (CFSR) of the National Centers for Environmental Prediction (NCEP). The model skill was tested using different rea-nalyzed precipitation datasets that represent different space scales. The bias of the model shows seasonal and spatial dependences, with positive bias in southwestern Brazilian Amazon during summer and in northwestern South America during autumn. The downscaling was needed to reproduce the surface influences on the regional and local systems that affect the rainfall distribution in the region. The WRF model, in general, reproduces the main observed precipitation patterns, without the dry bias, typical of general circulation models (GCM). The results indicate that the dynamic downscaling technique improves the WRF model performance for the seasonal climate forecast in the Amazon region. © 2019, Sociedade Brasileira de Meteorologia. All rights reserved