A. James Clark School of Engineering
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The collections in this community comprise faculty research works, as well as graduate theses and dissertations.
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Item DEVELOPMENT AND VALIDATION OF A PYROLYSIS MODEL FOR FLEXIBLE POLYURETHANE FOAM(2024) Kamma, Siriwipa; Stoliarov, Stanislav I; Fire Protection Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Flexible polyurethane foam (FPUF) is a common material contained in household goods such as upholstered furniture and mattresses, which are known to significantly contribute to fire growth. An accurate prediction of fire development on FPUF containing items requires knowledge of FPUF pyrolysis and combustion properties. These properties include reaction kinetic parameters, thermodynamic parameters, and thermal transport properties. While many past studies focused on the thermal decomposing mechanism and thermodynamic properties of the reactions, the thermal transport properties have not been determined. In this study, a complete pyrolysis model of FPUF was developed by extending the thermal decomposition model from a previous study. The thermal transport properties were obtained using inverse modeling of the Controlled Atmosphere Pyrolysis Apparatus II experimental data. The complete model was validated against cone calorimetry data and found to perform in an adequate manner.Item Pyrolysis Model Development for a Multilayer Floor Covering(MDPI, 2015-09-14) McKinnon, Mark B.; Stoliarov, Stanislav I.Comprehensive pyrolysis models that are integral to computational fire codes have improved significantly over the past decade as the demand for improved predictive capabilities has increased. High fidelity pyrolysis models may improve the design of engineered materials for better fire response, the design of the built environment, and may be used in forensic investigations of fire events. A major limitation to widespread use of comprehensive pyrolysis models is the large number of parameters required to fully define a material and the lack of effective methodologies for measurement of these parameters, especially for complex materials. The work presented here details a methodology used to characterize the pyrolysis of a low-pile carpet tile, an engineered composite material that is common in commercial and institutional occupancies. The studied material includes three distinct layers of varying composition and physical structure. The methodology utilized a comprehensive pyrolysis model (ThermaKin) to conduct inverse analyses on data collected through several experimental techniques. Each layer of the composite was individually parameterized to identify its contribution to the overall response of the composite. The set of properties measured to define the carpet composite were validated against mass loss rate curves collected at conditions outside the range of calibration conditions to demonstrate the predictive capabilities of the model. The mean error between the predicted curve and the mean experimental mass loss rate curve was calculated as approximately 20% on average for heat fluxes ranging from 30 to 70 kW·m−2, which is within the mean experimental uncertainty.Item Development of a Semiglobal Reaction Mechanism for the Thermal Decomposition of a Polymer Containing Reactive Flame Retardants: Application to Glass-Fiber-Reinforced Polybutylene Terephthalate Blended with Aluminum Diethyl Phosphinate and Melamine Polyphosphate(MDPI, 2018-10-12) Ding, Yan; Stoliarov, Stanislav I.; Kraemer, Roland H.This work details a methodology for parameterization of the kinetics and thermodynamics of the thermal decomposition of polymers blended with reactive additives. This methodology employs Thermogravimetric Analysis, Differential Scanning Calorimetry, Microscale Combustion Calorimetry, and inverse numerical modeling of these experiments. Blends of glass-fiber-reinforced polybutylene terephthalate (PBT) with aluminum diethyl phosphinate and melamine polyphosphate were used to demonstrate this methodology. These additives represent a potent solution for imparting flame retardancy to PBT. The resulting lumped-species reaction model consisted of a set of first- and second-order (two-component) reactions that defined the rate of gaseous pyrolyzate production. The heats of reaction, heat capacities of the condensed-phase reactants and products, and heats of combustion of the gaseous products were also determined. The model was shown to reproduce all aforementioned experiments with a high degree of detail. The model also captured changes in the material behavior with changes in the additive concentrations. Second-order reactions between the material constituents were found to be necessary to reproduce these changes successfully. The development of such models is an essential milestone toward the intelligent design of flame retardant materials and solid fuels.Item Polyisocyanurate Foam Pyrolysis and Flame Spread Modeling(MDPI, 2021-04-13) Chaudhari, Dushyant M.; Stoliarov, Stanislav I.; Beach, Mark W.; Suryadevara, Kali A.Polyisocyanurate (PIR) foam is a robust thermal insulation material utilized widely in the modern construction. In this work, the flammability of one representative example of this material was studied systematically using experiments and modeling. The thermal decomposition of this material was analyzed through thermogravimetric analysis, differential scanning calorimetry, and microscale combustion calorimetry. The thermal transport properties of the pyrolyzing foam were evaluated using Controlled Atmosphere Pyrolysis Apparatus II experiments. Cone calorimetry tests were also carried out on the foam samples to quantify the contribution of the blowing agent (contained within the foam) to its flammability, which was found to be significant. A complete pyrolysis property set was developed and was shown to accurately predict the results of all aforementioned measurements. The foam was also subjected to full-scale flame spread tests, similar to the Single Burning Item test. A previously developed modeling approach based on a coupling between detailed pyrolysis simulations and a spatially-resolved relationship between the total heat release rate and heat feedback from the flame, derived from the experiments on a different material in the same experimental setup, was found to successfully predict the evolution of the heat release rate measured in the full-scale tests on the PIR foam.Item DEVELOPMENT OF A PYROLYSIS MODEL FOR ORIENTED STRAND BOARD(2021) Zhou, Hongen; Stoliarov, Stanislav I.; Fire Protection Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)Oriented Strand Board (OSB) is a widely used construction material responsible for a substantial portion of the fire load of many buildings. To accurately model the response of OSB to fire, Thermogravimetric Analysis (TGA), Differential Scanning Calorimetry (DSC) and Microscale Combustion Calorimetry (MCC) tests were carried out to construct a thermal decomposition model using a numerical solver, ThermaKin2Ds, and a hill climbing (HC) optimization algorithm. The model was determined to consist of two distinct processes. The first process is a single step water vaporization. The second process is a chain of four consecutive reactions representing thermal decomposition of the organic constituents of OSB. The experiments and modeling revealed that the first two of the four reactions are endothermic, while the last two are exothermic, and that the net heat of decomposition is near zero. The heat capacities of condensed-phase species and heats of combustion of evolved gases were also determined from inverse modeling of the DSC and MCC tests, respectively. Controlled Atmosphere Pyrolysis Apparatus II (CAPA II) experiments were performed at 35 kW m-2 and 65 kW m-2 of the radiant heat flux. The sample bottom temperature data obtained at 65 kW m-2 were used to determine the thermal conductivities of condensed-phase species. The complete pyrolysis model of OSB was subsequently validated by comparing the experimental CAPA II mass loss rate profiles with the model predictions. The undecomposed OSB density was found to vary both along the sheet surface and through thickness. However, these density variations had only a minor impact on the key features of the mass loss rate profiles.Item Development of a Semiglobal Reaction Mechanism for the Thermal Decomposition of a Polymer Containing Reactive Flame Retardants: Application to Glass-Fiber-Reinforced Polybutylene Terephthalate Blended with Aluminum Diethyl Phosphinate and Melamine Polyphosphate(MDPI, 2018-09-17) Ding, Yan; Stoliarov, Stanislav I.; Kraemer, Roland H.This work details a methodology for parameterization of the kinetics and thermodynamics of the thermal decomposition of polymers blended with reactive additives. This methodology employs Thermogravimetric Analysis, Differential Scanning Calorimetry, Microscale Combustion Calorimetry, and inverse numerical modeling of these experiments. Blends of glass-fiber-reinforced polybutylene terephthalate (PBT) with aluminum diethyl phosphinate and melamine polyphosphate were used to demonstrate this methodology. These additives represent a potent solution for imparting flame retardancy to PBT. The resulting lumped-species reaction model consisted of a set of first- and second-order (two-component) reactions that defined the rate of gaseous pyrolyzate production. The heats of reaction, heat capacities of the condensed-phase reactants and products, and heats of combustion of the gaseous products were also determined. The model was shown to reproduce all aforementioned experiments with a high degree of detail. The model also captured changes in the material behavior with changes in the additive concentrations. Second-order reactions between the material constituents were found to be necessary to reproduce these changes successfully. The development of such models is an essential milestone toward the intelligent design of flame retardant materials and solid fuels.Item A COMPREHENSIVE CHARACTERIZATION OF PYROLYSIS AND COMBUSTION OF INTUMESCENT AND CHARRING POLYMERS USING TWO-DIMENSIONAL MODELING: A RELATIONSHIP BETWEEN THERMAL TRANSPORT AND THE PHYSICAL STRUCTURE OF THE INTUMESCENT CHAR(2019) Swann, Joshua; Stoliarov, Stanislav I; Mechanical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)A quantitative understanding of an intumescent material’s reaction to fire remains largely an unsolved challenge. More specifically, the relationship between thermal transport and the resulting char structure is not well understood. Improved pyrolysis models for intumescent materials are necessary to advance the fields of fire modeling and material development. To aid in this endeavor, a systematic methodology to parameterize comprehensive pyrolysis models for charring and intumescent materials is presented. Rigid poly(vinyl chloride), flexible poly(vinyl chloride), Bisphenol A poly(carbonate), poly(ether ether ketone), and poly(vinylidene fluoride) were analyzed in this work. First, thermogravimetric analysis and differential scanning calorimetry were employed simultaneously to characterize the kinetics and thermodynamics of thermal decomposition. Microscale combustion calorimetry was utilized to parameterize the heats of complete combustion of gaseous pyrolyzates. ThermaKin, a numerical pyrolysis solver, was employed to inversely analyze all milligram-scale tests. A multi-step reaction mechanism, consisting of sequential steps, was constructed to capture all observed physical changes and chemical reactions. Gasification tests were conducted on 0.07 m diameter disk-shaped samples using the newly developed Controlled Atmosphere Pyrolysis Apparatus II to parameterize the thermal transport within the undecomposed material and developing char layer. A recently expanded version of ThermaKin, ThermaKin2Ds, was employed to inversely model the gasification experimental results. The model accounted for spatially non-uniform swelling of the sample and the ensuing changes within the thermal boundary conditions. The resulting two-dimensional models were shown to reproduce the experimental sample shape profiles, unexposed surface temperatures, and mass loss rates with excellent accuracy. An analysis of the char pore structure was also conducted to determine the pore size distribution and char porosity. Further analysis enabled the mean, median, and volume-weighted mean pore diameters to be computed from pore size distributions. Quantitative relationships were subsequently developed between relevant thermal transport quantities and the char’s physical structure. It was determined that the thermal insulating potential of the fully developed char was related to the number of pore walls positioned perpendicular to the direction of heat flow. Therefore, designing charring polymers capable of producing many small pores will aid in the development of intumescent materials with an enhanced thermal insulating potential.Item A GENERALIZED METHODOLOGY TO DEVELOP PYROLYSIS MODELS FOR POLYMERIC MATERIALS CONTAINING REACTIVE FLAME RETARDANTS: RELATIONSHIP BETWEEN MATERIAL COMPOSITION AND FLAMMABILITY BEHAVIOR(2018) Ding, Yan; Stoliarov, Stanislav I; Mechanical Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)The development of effective flame retardant polymeric materials is of great interest to the fire protection community. To enable intelligent design of flame retardant polymeric materials, it is important to understand the relation between the material composition and the chemical and physical properties that control the fire growth process. This work details a generalized methodology to characterize flame retardant materials for the development of pyrolysis models that relate the fire behavior to material composition. The methodology employs thermogravimetric analysis, differential scanning calorimetry, and microscale combustion calorimetry, to measure the sample mass loss, heat required to decompose the sample, and the heat released from the complete combustion of the gaseous products evolved during the sample decomposition, respectively. Through inverse analysis of the milligram-scale experimental measurements using a numerical pyrolysis framework, ThermaKin2Ds, the decomposition kinetics and thermodynamics, and heats of combustion of gaseous pyrolyzate are determined. The chemical interactions between the polymer matrix and flame retardants are characterized by second-order (two-component) reactions. The resulting reaction model reproduces all aforementioned experiments with a high degree of detail as a function of heating rate and captures changes in the decomposition behavior with changes in the flame retardant contents. The methodology also utilizes a new bench-scale controlled atmosphere gasification apparatus to measure mass loss rate (MLR), back surface temperature, and sample shape profile evolution of 7-cm-diameter disk-shaped samples exposed to well-defined radiant heating. Inverse analysis of the bench-scale gasification experimental measurements using ThermaKin2Ds and the developed reaction model yields properties that define heat and mass transport in the pyrolyzing samples. This approach is demonstrated using two sets of materials: glass-fiber-reinforced polyamide 66 blended with red phosphorus and glass-fiber-reinforced polybutylene terephthalate blended with aluminum diethyl phosphinate and melamine polyphosphate. The resulting pyrolysis model is capable of predicting MLR data as a function of material composition and external heating condition. Idealized cone calorimetry simulations are conducted to demonstrate that, when the gas-phase combustion inhibition effect is excluded, aluminum diethyl phosphinate has a relatively minor impact on heat release rate, while the impacts of melamine polyphosphate and red phosphorus are significant.Item A Methodology for Determining the Fire Performance Equivalency Amongst Similar Materials During a Full-scale Fire Scenario Based on Bench-scale Testing(2015) Lannon, Chad Michael; Stoliarov, Stanislav I; Fire Protection Engineering; Digital Repository at the University of Maryland; University of Maryland (College Park, Md.)A methodology was developed for determining the equivalency amongst materials during a full-scale fire scenario. This procedure utilizes milligram-scale and or bench-scale tests to obtain the effective physical and chemical properties of individual materials through an optimization procedure. A flame heat feedback model was developed for corner-wall flame spread and implemented into a two-dimensional pyrolysis model, ThermaKin2D. ThermaKin2D was utilized to simulate upward flame spread during the room corner test. A criterion was created that determines the fire performance of similar materials during this full-scale fire scenario and compares how each material performed relative to one another. A fire investigator will be able to better select materials for their reconstructive fire test based on the modeled full-scale fire performance of candidate materials compared to the exemplar material found during the fire investigation. Overall, this procedure is expected to improve a fire investigator’s ability to perform accurate reconstructive fire tests.