Stanislav I. Stoliarov

Thermo-Kinetic Model of Burning for Pyrolyzing Materials

One of the main obstacles to development of more effective passive fire protection for transportation is the lack of a quantitative understanding of the relations between the results of various materials fire tests used in this field. The need for multiple testing techniques arises from the complexity of fire phenomena and their sensitivity to environmental conditions. This work addresses this problem by developing a computational tool that predicts the behavior of materials exposed to fire. While it is not expected that this tool will eliminate the need for fire testing, the goal is to considerably reduce the number and complexity of the tests necessary for a comprehensive characterization of the materials of interest. The foundation of this tool is a mathematical model that describes transient thermal energy transport, chemical reactions, and transport of gases through the condensed phase. The model also captures such important aspects of material’s behavior as charring and intumescence. This paper provides a detailed description of the onedimensional version of this model and summarizes results of its verification.

Pyrolysis Model Development for a Multilayer Floor Covering

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.

Mechanism of the thermal decomposition of bisphenol C polycarbonate: nature of its fire resistance

Abstract Quantum chemical methods have been used to identify reaction pathways of the thermal decomposition of bisphenol C polycarbonate, one of the most fire-resistant polymers known to the scientific community. Despite substantial interest in its unusual high-temperature behavior, the mechanism of its thermal decomposition has been unknown. On the basis of computational results, a mechanism is proposed where the main feature is a shift of Cl atom from the β-styrene position to the adjacent aromatic ring, which leads to crosslinking and cyclization of the polymer. The proposed mechanism is consistent with experimental observations of char, HCl, and CO2 as the main pyrolysis products.

Pyrolysis model for a carbon fiber/epoxy structural aerospace composite:

Carbon fiber laminate composites have been utilized in the aerospace industry by replacing lightweight aluminum alloy components in the design of aircraft. By replacing low flammability aluminum components by carbon fiber laminates, the potential fuel load for aircraft fires may be increased significantly. A pyrolysis model has been developed for a Toray Co. carbon fiber laminate composite. Development of this model is intended to improve the understanding of the fire response and flammability characteristics of the composite, which complies with Boeing Material Specification 8–276. The work presented here details a methodology used to characterize the composite. The mean error between the predicted curves and the mean experimental mass loss rate curves collected in bench-scale gasification tests was calculated as approximately 17% on average for heat fluxes ranging from 40 to 80 kW m−2. During construction of the model, additional complicating phenomena were investigated. It was shown that the thermal conductivity in the plane of the composite was approximately 15 times larger than the in-depth thermal conductivity, the mass transport was inhibited due to the high density of the laminae in the composite, and oxidation did not appear to significantly affect pyrolysis at heat fluxes up to 60 kW m−2.

Enhanced thermal decomposition kinetics of poly(lactic acid) sacrificial polymer catalyzed by metal oxide nanoparticles

Poly Lactic Acid (PLA) has been used as a sacrificial polymer in the fabrication of battery separators and can be employed in 0D–3D Vaporization of a Sacrificial Component (VaSC) fabrication. In this study, 1 wt% PLA/Fe2O3, PLA/CuO and PLA/Bi2O3 composites are prepared by solvent evaporation casting. Scanning Electron Microscopy (SEM) images indicate that the embedded nanoparticles are well dispersed in the polymer matrix and X-ray diffraction (XRD) verifies the crystallinity of these Metal Oxides (MOs). Thermal stability analysis of the PLA and PLA/MO composites is performed using a thermogravimetric analyzer (TGA) and Differential Scanning Calorimeter (DSC). The overall heat of combustion is measured by Microscale Combustion Calorimetry (MCC) and is found to be insensitive to the presence of nanoparticles. The overall catalytic effects of the three metal oxides have the following trend: Bi2O3 > Fe2O3 > CuO ≈ inert material. The PLA/Bi2O3 decomposition onset temperature (T5%) and maximum mass loss decomposition temperature (Tmax) are lowered by approximately 75 K and 100 K respectively compared to the neat PLA. The as-synthesized Bi2O3 is identified as the most effective additive among those proposed in the literature to catalyze the PLA thermal decomposition process. A numerical pyrolysis modeling tool, ThermaKin, is utilized to analyze thermogravimetric data of all the PLA/MOs and to produce a description of the decomposition kinetics, which can be utilized for modeling of thermal vaporization of these sacrificial materials.

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

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.

Proceedings of the first workshop organized by the IAFSS Working Group on Measurement and Computation of Fire Phenomena (MaCFP)

This paper provides a report of the discussions held at the first workshop on Measurement and Computation of Fire Phenomena (MaCFP) on June 10-11 2017. The first MaCFP work-shop was both a technical meeting for the gas phase subgroup and a planning meeting for the condensed phase subgroup. The gas phase subgroup reported on a first suite of experimental- computational comparisons corresponding to an initial list of target experiments. The initial list of target experiments identifies a series of benchmark configurations with databases deemed suitable for validation of fire models based on a Computational Fluid Dynamics approach. The simulations presented at the first MaCFP workshop feature fine grid resolution at the millimeter- or centimeter- scale: these simulations allow an evaluation of the performance of fire models under high-resolution conditions in which the impact of numerical errors is reduced and many of the discrepancies between experimental data and computational results may be attributed to modeling errors. The experimental-computational comparisons are archived on the MaCFP repository [1]. Furthermore, the condensed phase subgroup presented a review of the main issues associated with measurements and modeling of pyrolysis phenomena. Overall, the first workshop provided an illustration of the potential of MaCFP in providing a response to the general need for greater levels of integration and coordination in fire research, and specifically to the particular needs of model validation.

Correction: McKinnon M.B. and Stoliarov S.I. Pyrolysis Model Development for a Multilayer Floor Covering. Materials 2015, 8, 6117–6153

The authors wish to make the following corrections to this manuscript [1]. During the publishing process, symbols that represented the absorption coefficient in Table 4 and thermal conductivity in Table 5 were changed such that they were inconsistent with the rest of the manuscript. [...].

Liquid Expansion in Glass Sprinkler Bulbs

An analysis of the physics of liquid expansion in fire sprinkler bulbs is presented to characterize the variation in void size and pressure with temperature. Two types of bulbs are considered, one filled with liquid and air, and the other filled with liquid and its vapor. The analysis predicts that the void fraction decreases linearly with temperature until the void disappears or the bulb fractures. The increase of pressure at increased temperature is much steeper when there is no air in the bulb. Observations generally support the predicted void sizes, with some commercial bulbs found to contain liquid and air, and others found to contain liquid and its vapor.