L. Haurie

Characterization of highly filled magnesium hydroxide-polypropylene composite foams

Magnesium hydroxide—filled polypropylene foams were prepared by a compression-molding chemical foaming process and studied considering the effects of foaming and the presence of the particles on the microstructure (cellular structure and induced particle and polymer orientations), dynamic mechanical, and flame retardancy of the polypropylene composites. Two magnesium hydroxide concentrations, 50 and 70 wt%, as well as different foam densities, were considered. Results are discussed in terms of the observed anisotropy-induced cellular and particle and crystal orientations and their effects on the direction-dependent dynamic mechanical and flame behavior results. Preliminary flame retardancy characterization of the several solid and foamed composites showed interesting results due to foaming, foams globally exhibiting a higher extinguishability than the respective solid composites.

A possible recycling method for high grade steels EAFD in polymer composites

This work evaluates the feasibility of incorporating electric arc furnace dust (EAFD), as filler in a polymer matrix, to obtain a moldable heavyweight sheet, useful for acoustic insulation in automotive industry. For this purpose EAFD from a steel factory that manufactures high quality steels, was characterized and different formulations of composites were prepared. Physical and mechanical properties, as well as fire behaviour were tested and compared with a polymer composite compounded with common mineral fillers. Optimum formulation with 25% EAFD fulfils the RoHs Directive used by automotive industry to regulate heavy metals content. Leaching test was also performed on prepared composites to classify the material after use.

Comparative Study of Magnesium By-Products and Vermiculite Formulations to Obtain Fire Resistant Mortars

There exists an increasing concern about the dangers originated in a building in case of fire. In this work the behaviour of vermiculite as aggregate in fireproof mortars was compared with mortars formulated with two magnesium by-products aggregates which undergo an endothermic decomposition. Fire resistance and mechanical properties were evaluated. An optimal mixture of both magnesium by-products as aggregates allows formulating mortars that improve fire resistance at temperatures greater than 450 °C compared with vermiculite mortars. It would be interesting to obtain mortars formulated with magnesium by products and vermiculite to study possible synergic effects.

Study of the Thermal Properties and the Fire Performance of Flame Retardant-Organic PCM in Bulk Form

The implementation of organic phase change materials (PCMs) in several applications such as heating and cooling or building comfort is an important target in thermal energy storage (TES). However, one of the major drawbacks of organic PCMs implementation is flammability. The addition of flame retardants to PCMs or shape-stabilized PCMs is one of the approaches to address this problem and improve their final deployment in the building material sector. In this study, the most common organic PCM, Paraffin RT-21, and fatty acids mixtures of capric acid (CA), myristic acid (MA), and palmitic acid (PA) in bulk, were tested to improve their fire reaction. Several flame retardants, such as ammonium phosphate, melamine phosphate, hydromagnesite, magnesium hydroxide, and aluminum hydroxide, were tested. The properties of the improved PCM with flame retardants were characterized by thermogravimetric analyses (TGA), the dripping test, and differential scanning calorimetry (DSC). The results for the dripping test show that fire retardancy was considerably enhanced by the addition of hydromagnesite (50 wt %) and magnesium hydroxide (50 wt %) in fatty acids mixtures. This will help the final implementation of these enhanced PCMs in building sector. The influence of the addition of flame retardants on the melting enthalpy and temperatures of PCMs has been evaluated.

Kinetic analysis of endothermic degradation of magnesium hydroxide, calcium hydroxide and calcium carbonate in the context of passive fire protection

In a fire scenario, huge amounts of heat are generated and high temperatures rapidly achieved in such a way that the integrity of structural materials becomes compromised. One of the aims of passive fire protection is the use of building materials that are able to absorb at least part of that heat and maintain the structural materials under critical temperatures for longer times in order to gain evacuation time. Gypsum panels are commonly used in building walls, but they only absorb heat at temperatures around 110 degrees C. We use three inorganic fillers, Mg(OH)(2), Ca(OH)(2) and CaCO3, which undergo endothermic transitions at high temperatures to obtain an improved panel with a richer heat-absorbing profile. With this formulation, the time to reach temperatures of the order of 500 degrees C, critical for steel and reinforced concrete, is significantly increased. In this work, we focus on the kinetics of the endothermic fillers as an essential ingredient for further spatially extended simulations that include macroscopic heat and mass transfer phenomena or sample heterogeneities. However, kinetics may be affected as well by heat transfer effects that occur at molecular levels. Copyright (c) 2014 John Wiley & Sons, Ltd.

Trace metal partitioning in caustic calcined magnesia produced from natural magnesite.

Caustic calcined magnesia from natural magnesite has been widely employed as a source of magnesium. This mineral, depending on the origin, may contain heavy metals and metalloids that can exceed the regulatory limits in some applications. In most cases, heavy metals and metalloids form solid solutions with the mineral phases of the main impurities, or even magnesium oxide itself, replacing other ions in the crystal lattice. Compared with magnesium oxide, most of these impurities such as silica and silicates are much more chemically stable even in concentrated mineral acids under normal temperature and pressure conditions. In this study, the partitioning of the trace metals was monitored using a sequential extraction procedure (SEP), and their potential solubility was determined using the pH-static leaching test. Only a small fraction of magnesium oxide derived from heavily calcined magnesia is soluble in slightly acidic media. The release of the trace metals and metalloids contained in the soluble fractions was less than 40% as determined by total digestion. It can be concluded that SEP is more accurate than total chemical digestion for setting the maximum limits of the undesirable trace metals.

Study of Fresh and Hardening Process Properties of Gypsum with Three Different PCM Inclusion Methods

Gypsum has two important states (fresh and hardened states), and the addition of phase change materials (PCM) can vary the properties of the material. Many authors have extensively studied properties in the hardened state; however, the variation of fresh state properties due to the addition of Micronal® DS 5001 X PCM into gypsum has been the object of few investigations. Properties in fresh state define the workability, setting time, adherence and shrinkage, and, therefore the possibility of implementing the material in building walls. The aim of the study is to analyze, compare and evaluate the variability of fresh state properties after the inclusion of 10% PCM. PCM are added into a common gypsum matrix by three different methods: adding microencapsulated PCM, making a suspension of PCM/water, and incorporating PCM through a vacuum impregnation method. Results demonstrate that the inclusion of PCM change completely the water required by the gypsum to achieve good workability, especially the formulation containing Micronal® DS 5001 X: the water required is higher, the retraction is lower (50% less) due to the organic nature of the PCM with high elasticity and, the adherence is reduced (up to 45%) due to the difference between the porosity of the different surfaces as well as the surface tension difference.

Kinetic analysis of endothermic degradation of magnesium hydroxide, calcium hydroxide and calcium carbonate in the context of passive fire protection: KINETIC ANALYSIS OF ENDOTHERMIC DEGRADATION

In a fire scenario, huge amounts of heat are generated and high temperatures rapidly achieved in such a way that the integrity of structural materials becomes compromised. One of the aims of passive fire protection is the use of building materials that are able to absorb at least part of that heat and maintain the structural materials under critical temperatures for longer times in order to gain evacuation time. Gypsum panels are commonly used in building walls, but they only absorb heat at temperatures around 110 degrees C. We use three inorganic fillers, Mg(OH)(2), Ca(OH)(2) and CaCO3, which undergo endothermic transitions at high temperatures to obtain an improved panel with a richer heat-absorbing profile. With this formulation, the time to reach temperatures of the order of 500 degrees C, critical for steel and reinforced concrete, is significantly increased. In this work, we focus on the kinetics of the endothermic fillers as an essential ingredient for further spatially extended simulations that include macroscopic heat and mass transfer phenomena or sample heterogeneities. However, kinetics may be affected as well by heat transfer effects that occur at molecular levels. Copyright (c) 2014 John Wiley & Sons, Ltd.