SUMMARYGypsum plasterboards are widely used for compartmentation and for retarding the spread of fire in buildings. Although numerous heat transfer studies have been conducted, literature indicates there are extensive differences in the thermal properties used in these studies. Comprehensive experimental and numerical analyses have been conducted to elucidate the leading factor in the ablation of a gypsum board system when it is exposed to the standard fire resistance test. A methodology based on both simultaneous thermal analysis and computational modelling is proposed to understand the behaviour of a gypsum plasterboard when the boundary temperature increases quickly as one side of the wall is subjected to the standard ISO 834. Finally, four different wall assemblies made of a commercial fireproof plasterboard system are exposed to the standard test. The temperature on the unexposed face is examined to validate the computational model of the plasterboard.

The analysis of polymer chemical decomposition is often highly dependent on the test conditions. In fact, thermal analysis tends to be far more sensitive to instrumental parameters than other branches of chemical analysis. Some of the boundary conditions in thermal analysis have been widely studied in the literature, such as the heating rate or the atmosphere. However, the influence of the sample mass, the gas flow or the use of lid have not been enough studied for thermoplastic polymers.The aim of this paper is to analyse how the experimental boundary conditions of the Simultaneous Thermal Analysis apparatus affect the thermal decomposition of thermoplastic polymers. To do so a set of 35 experimental tests have been performed including variation of the sample mass, gas flow rate, heating rate, atmosphere and the use of lid in the crucible. Results enable us to analyse the influence in the mass loss and in the energy release or absorbed in the thermal decomposition of thermoplastic polymers, showing the impact of each boundary condition over the thermal decomposition. A comprehensive analysis of the thermal decomposition behaviour of the PVC and LLDPE by considering the influence of all the boundary conditions of the STA is covered. It is especially remarkable the influence of gas flow in the oxidative reactions, and of heating rate in the chemical reactions that thermoplastics polymers undergo in their decomposition. Additionally, sample mass comparison shows only deviation in the oxidative reactions, and do not show deviation for the non-oxidative reactions. That seems to show a higher effect on the results because of the energy release in the decomposition reactions than because of the thermal lag due to heat transfer on the sample, as it is usually thought.

Understanding a material's fire behaviour implies to know the thermal decomposition processes. Thermal analysis techniques are widely employed to study thermal decomposition processes, especially to calculate the kinetic and thermal properties. Cardboard boxes are widely employed as rack-storage commodities in industrial buildings. Hence, the characterization of the cardboard is considered a key factor for fire safety engineering, because it enables the determination of its thermal behaviour at high temperatures. The employment of mathematical or computational models for modelling the thermal decomposition processes is commonly used in fire safety engineering (FSE). The fire dynamics simulator (FDS) software is one of the most commonly used computational fluid dynamics software in FSE to address thermal analysis. To properly set up FDS and obtain accurate results, the numerical values of the thermal and kinetic properties are needed as input data. Owing to the large number of variables to be determined, a preliminary study is bound to be helpful, which can well-assess the influence of each variable over the pyrolysis model, discarding or restricting their influence. This study, based on the Monte Carlo method, presents a sensitivity analysis for the variables utilized as input data by the FDS software. The results show the conversion factor α, i.e. the mass involved in each reaction, and the triplet kinetic has a major impact on the reproduction of the thermal decomposition process in fire computer modelling.

This work aims to elucidate whether the hypothesis of zero-oxygen at the mixture layer when flame takes place is assumable for every kind of material. For that purpose, we investigated the oxygen concentration there by cone calorimeter tests. A modified holder was developed in order to collect oxygen in this mixture layer. In addition, thermogravimetric tests were carried out so as to relate the possible effects of the presence of oxygen in the atmosphere where the pyrolysis process takes place, since the cone calorimeter does not allow to control the oxygen level of the atmosphere during the experiment. The reaction rates and percent of residue in the cone calorimetric tests were measured and compared with the results from thermogravimetric tests. Six products were analysed which can be classified in three main groups: lignocellulosic, thermoplastic polymers and thermoset polymers. Cone calorimetric results showed that for some of the materials analysed (PET, Nylon and PUR foam) the oxygen level at mixture layer decreased until values close to zero. The comparison of reaction rates between cone calorimetric and thermogravimetric tests revealed the char layer created in cone calorimetric tests over the exposed face for brushed fir, Nylon and PET established an important heat barrier that modifies the thermal behaviour of these materials Keywords Cone calorimeter, thermal oxidation of char, oxygen concentration, carbon dioxide concentration, pyrolysis behaviour, thermogravimetric analysis. Nomenclature ̇c one Incident flux from cone calorimeter/kW•m-2 ṁp eak Peak of the mass flow released by the sample and measured by the cone in the exhaust tube/kg•s-1 T ̅ Average temperature of the surface of the sample during the test after the ignition/ºC q̇ cone peak HRR peak during the test released by the sample in cone test without gas sampling tubes/kW•m-2 ṁs Sampling mass flow/kg•s-1 q̇ gas peak HRR peak during the test released by the sample in cone test with gas sampling tubes/kW•m-2 / ṁa vg Average mass flow released by the sample and measured by the cone in the exhaust tube/kg•s-1

Thermal analysis techniques play a crucial role to characterize solid phase thermal decomposition, since it provides information about how mass is lost (Thermal Gravimetric Analysis) and energy released (Differential Scanning Calorimetry). However, most of the INPUT thermal parameters and kinetic properties to be used in fire computer modelling cannot be obtained directly from those tests. Early works looked forward achieving those parameters employing indirect fitting methods, which enable the user to obtain a set of parameters capable to simulate accurately the mass loss curve (TG) or its derivative (DTG). This work aims to study the possibility of adding the energy released as a new target in the process, applying the analysis to Linear Low-Density Polyethylene (LLDPE). Results obtained in the present work reveal the major challenge of getting a set of parameters that can also fit DSC curve. The level of accuracy of the fitting to TG curve is higher than to DSC curve. This fact increases the value of the errors when both curves are used as targets to approach. As a result, this paper includes an alternative to consider the effects of the DSC curve.