Improving the thermal stability and fire safety of PVC formworks

This study examines the impact of materials and compositions on the fire design considerations of plastic formworks, focusing on the influence of building materials on the fire resistance of buildings, the safety of occupants, and the environment. The study investigates the chemical properties of formworks, including heat resistance, UV resistance, and smoke suppressant properties, which are essential for developing and optimizing formwork products. The research covers three key areas for improving thermal behaviour of PVC: (a) the development and evaluation of new metal complexes with dipentaerythritol, (b) cementitious compositions as a novel class of thermal stabilizers, and (c) the development and evaluation of a new synergistic thermo stabilizer based on sodium hexametaphosphate. To investigate the thermal degradation procedures of each additive for fire retardancy workability, the study utilizes advanced techniques such as thermal gravimetric analysis (TGA), fourier transform infrared spectroscopy (FT-IR), X-ray diffraction spectroscopy (XRD), scanning electron microscopy (SEM), and Energy Dispersive Spectroscopy (EDS). The results demonstrate that hydrated cementitious materials are more effective in stabilizing PVC than metal chelates of dipentaerythritol or synergistic stabilizers based on sodium hexametaphosphate. Moreover, the study found that zinc, as a metal complex with dipentaerythritol, is more effective than traditional stabilizers. The research on cementitious compositions also revealed their highly economical, environmentally friendly, and compatible nature, making them an attractive option for use in the PVC formwork construction industry. The study also highlights the positive impact of calcium metaborate and sodium hexametaphosphate in improving the thermal behaviour of PVC. The study emphasizes the significance of fire-resistant materials in ensuring the safety of occupants and the environment, and the need for innovative solutions to enhance their effectiveness. In conclusion, this research underscores the importance of materials and compositions in the fire design considerations of plastic formworks. The study's findings can imply the development of more effective and sustainable fire-resistant materials and promote safer buildings

Shape-stable and smart polyrotaxane-based phase change materials with enhanced flexibility and fire-safety.

post-print2142 K

Phytic acid as a biomass flame retardant for polyrotaxane based phase change materials.

Petrochemical resources are facing depletion and human long-term survival needs sustainable development. In this era, it is very important to develop new sustainable phase change materials (PCMs), because it has shown great application value in the effective utilization of industrial waste heat, solar energy harvesting, and electronic heat treatment. In this work, we reported a biomass phytic acid (PA) modified polyrotaxane (PLR) as PCMs for thermal management. The tensile performances, fire safety, phase transition performances of the PCMs were investigated. It is found that all the tensile properties, char residual, and fire-safety of PLR can be enhanced remarkably by introduce of PA. Typically, the Young's modulus, yielding strength and tensile strength of the PLR were 826.7 MPa, 14.2 MPa and 14.2 MPa, respectively, and significantly increased to 1527.4 MPa, 22.1 MPa, and 24.0 MPa respectively, with the addition of 10 wt% of PA. Elongation (>783 %) for all modified PCMs was gradually increased with the increase of PA contents. Thermal analysis shows that the fire safety of PLR is significantly improved. Specifically, for the best sample PLR-PA30, the pHRR could decrease by 54.2 %, THR decreased by 34.0 %; and the LOI increased from 20.8 % to 28.2 %. The PCMs showed the perfect form stability and leakage-proof performance, enhanced thermal conductivity and outstanding cycle properties. Notably, its biomass source, and high flexibility, enhanced fire safety and completely green pathway may provide a practical way for the highly flexible and sustainable packaging of electronic devices for heat treatment.pre-print1895 K

Three dimensional flame reconstruction towards the study of fire-induced transmission line flashovers.

Thesis (M.Sc.Eng.)-University of KwaZulu-Natal, 2007.The work presented in this thesis focuses on the problem of reconstructing threedimensional models of fire from real images. The intended application of the reconstructions is for use in research into the phenomenon of fire-induced high voltage flashover, which, while a common problem, is not fully understood. As such the reconstruction must estimate not only the geometry of the flame but also the internal density structure, using only a set of a few synchronised images. Current flame reconstruction techniques are investigated, revealing that relatively little work has been done on the subject, and that most techniques follow either an exclusively geometric or tomographic direction. A novel method, termed the 3D Fuzzy Hull method, is proposed, incorporating aspects of tomography, statistical image segmentation and traditional object reconstruction techniques. By using physically based principles the flame images are related to the relative flame density, allowing the problem to be tackled from a tomographic perspective. A variation of algebraic tomography is then used to estimate the internal density field of the flame. This is done within a geometric framework by integrating the fuzzy c-means image segmentation technique and the visual hull concept into the process. Results are presented using synthetic and real flame image sets

Processing, Characterization And Performance Of Carbon Nanopaper Based Multifunctional Nanocomposites

Carbon nanofibers (CNFs) used as nano-scale reinforcement have been extensively studied since they are capable of improving the physical and mechanical properties of conventional fiber reinforced polymer composites. However, the properties of CNFs are far away from being fully utilized in the composites due to processing challenges including the dispersion of CNFs and the viscosity increase of polymer matrix. To overcome these issues, a unique approach was developed by making carbon nanopaper sheet through the filtration of well-dispersed carbon nanofibers under controlled processing conditions, and integrating carbon nanopaper sheets into composite laminates using autoclave process and resin transfer molding (RTM). This research aims to fundamentally study the processing-structure-property-performance relationship of carbon nanopaper-based nanocomposites multifunctional applications: a) Vibrational damping. Carbon nanofibers with extremely high aspect ratios and low density present an ideal candidate as vibrational damping material; specifically, the large specific area and aspect ratio of carbon nanofibers promote significant interfacial friction between carbon nanofiber and polymer matrix, causing higher energy dissipation in the matrix. Polymer composites with the reinforcement of carbon nanofibers in the form of a paper sheet have shown significant vibration damping improvement with a damping ratio increase of 300% in the nanocomposites. b) Wear resistance. In response to the iv observed increase in toughness of the nanocomposites, tribological properties of the nanocomposite coated with carbon nanofiber/ceramic particles hybrid paper have been studied. Due to high strength and toughness, carbon nanofibers can act as microcrack reducer; additionally, the composites coated with such hybrid nanopaper of carbon nanofiber and ceramic particles shown an improvement of reducing coefficient of friction (COF) and wear rate. c) High electrical conductivity. A highly conductive coating material was developed and applied on the surface of the composites for the electromagnetic interference shielding and lightning strike protection. To increase the conductivity of the carbon nanofiber paper, carbon nanofibers were modified with nickel nanostrands. d) Electrical actuation of SMP composites. Compared with other methods of SMP actuation, the use of electricity to induce the shape-memory effect of SMP is desirable due to the controllability and effectiveness. The electrical conductivity of carbon fiber reinforced SMP composites can be significantly improved by incorporating CNFs and CNF paper into them. A vision-based system was designed to control the deflection angle of SMP composites to desired values. The funding support from National Science Foundation and FAA Center of Excellence for Commercial Space Transportation (FAA COE CST) is acknowledged

Chemical and Physical Modification of Thiol-Ene and Epoxy-Amine Networks for Advanced Control of Gas Transport and Flame Retardant Behavior

Crosslinked polymers are widely used due to its several advantages not limited to high mechanical strength combined with the easy processability. Despite of its popular usage, the fundamental understanding of polymer structure affecting the desired properties is still lacking. This PhD thesis is in two parts, the first part is devoted to the design and developing a basic understanding of structure and chemical composition dependencies of gas transport, whereas in the second part a fundamental relationship between structure to the fire-retardant properties is established. Membrane based gas separation technique has attracted interest of selective removal of carbon dioxide gas from mixture of light gases such as H2, O2, N2 and CH4. Polyethylene glycol (PEG) has been employed to improve the solubility of acidic gases such as CO2 to improve the selective permeation. While conventional research on solubility selective membranes focuses on the strategies to prepare amorphous membrane while incorporating maximum PEG content, to the best of our knowledge, no studies have been focused in determining the effect of increasing PEG units on solubility/ selectivity of CO2/light gases. This research aims to determine the increasing effect of PEG units in solubility selectivity of UV curable thiol-ene based membranes. We determined the threshold amount of PEG units to achieve maximum CO2 gas solubility/ selectivity. We also examined the effect of network architecture on solubility when PEG units are placed in the backbone or as a dangling chain. The results indicated that CO2 solubility / selectivity saturated at 10 weight percentage of PEG for these elastomeric networks despite of the placement of the PEG units. Knowing that the required amount of PEG to achieve maximum selectivity is around 10 wt%, several other moieties that incorporate flexibility such as PDMS can be incorporated to further increase the permeability without compromising the selectivity, thus improving the overall membrane separation process. Crosslink density affects several properties of a crosslinked network. The effect of network crosslink density on fire retardant performance was examine via cone calorimeter using thiol-ene model networks in chapter 3. A series of network was designed to vary the rigidity and crosslink density. Rigidity was tuned by using different types of ene monomer from aliphatic to aromatic nature. By crosslinking trifunctional ene with thiol with varying functionality from 2 through 4, it was possible to increase the crosslink density without changing the chemical nature of the network. We determined that fire retardant properties improved with increasing crosslink density and rigidity within the series of networks examined. Pyrolysis behavior was examined via scanning electron microscope on networks constructed with two structurally similar ene monomers, allyl triazine (TOT) and an allyl isocyanurate (TTT). The combustion process was interrupted by quenching in liquid nitrogen at increasing times, and the cross section was examined via SEM. SEM images revealed that the isomers undergo distinct pyrolysis behavior. Networks containing ether linkage had faster bulk pyrolysis, while the monomers with allyl linkage underwent surface pyrolysis. Through cross section elemental analysis, we were able to quantify the composition different zone and were able to trace the extend of degradation at various time of combustion. This could be an important tool in enhancing the fire-resistant properties of the neat polymeric systems. Since epoxy networks are another class of polymers widely used in aerospace, electrical insulation and construction, special emphasis was given in understanding and correlating the epoxy resin structure with several fire-retardant properties determined via cone calorimeter in chapter 4. TGA analysis was used to calculate the activation energy of decomposition via fitting in Ozawa plot. The main emphasis was given to relate structural parameters such as glass transition temperature, network crosslink density to the fire performance of these networks. The presence of aromatic content in the networks influenced the char formation which reduced the heat release rate. For the first time, FR properties determined via cone calorimeter was corelated with numerically calculated heat release and heat capacity values predicted via molar group contribution method. Comparative studies of structurally similar isomers, 3,3’-DDS and 4,4’-DDS, revealed the differences in properties arising solely from the differences in configurational entropy between these monomers. Network containing 4,4’-DDS possess higher onset temperature and higher Tg, but interestingly, the peak heat release rate determined via cone calorimeter was inferior as compared to 3,3’-DDS containing networks. This is mainly due to the higher configurational entropy of 3,3’-DDS making the chain to pack better at elevated temperature during the combustion process. Following this basic understanding of structure fire retardant properties of epoxy amine networks, a comprehensive comparison of graphene oxide (GO) modified with a phosphorous based compound, DOPO-V and a polysiloxane (PMDA) flame retardant was studied. This was accomplished by two step process: in the first step, GO synthesis via Hummer’s method, while in the second step, the GO was functionalized by addition of DOPO and PMDA which were synthesized separately. The chemical modification of GO with DOPO-V and PMDA was verified using FTIR, XPS and AFM. Two separate FR additive, GO-DOPO-V and GO-PMDA was added to a standard DGEBA based epoxy resin which was cured with a polyether diamine (Jeffamine D230) to form a composite. Thermal stability of the composites were examined using TGA. DSC results showed no change in Tg which indicated that the added FR additive did not affect the epoxy amine matrix properties. Cone calorimetry was used as a tool to evaluate the flame-retardant properties of composites prepared using GO-DOPO-V and GO-PMDA. The cone results were compared with standard epoxy-amine matrix along with composites made by mixing GO, DOPO-V and PMDA separately which revealed that the presence of grafted GO, ie GO-DOPO-V and GO-PMDA, improved the flame retardancy. The char morphology analyzed via SEM revealed that the presence of GO along with the FR additives led to a honeycomb type morphology. We hypothesize that the modified GO improved the dispersion within the matrix which improved the FR properties. In the last session of this thesis, a new approach of using dissolved metal in improving flame retardant properties of several polymers including epoxy-amine (EP), polyurethane (PU), polystyrene (PS) and polyethylene oxide (PEO) is presented. Cone calorimeter was used as a standard tool to evaluate the flame retardancy of these metal dissolved composites. It was discovered unexpectedly that dissolution of a divalent metal, which is capable of forming an oxide layer upon combustion, improves the flame retardancy of a polymer matrix by suppressing the smoke formation and reducing the heat release rate. It was discovered that the presence of primary or secondary amine aids in metal dissolution of certain metal salts such as zinc acrylate, but metal salts containing long organic tail such as zinc stearate was readily dissolved upon heating. The dissolution was evidenced from formation of transparent composites and through the loss of crystal structure of metal salt detected through wide angle X-ray analysis. We discovered that the improvement in flame retardancy was greatly enhanced when the metal was dissolved rather than dispersed in the polymer matrix. A two-step additive approach was followed where in the first step an additive containing dissolved metal in amine was prepared which was subsequently added in to the desired polymer matrix in the second step. The solubility of the additive to a common solvent was chosen as a criterion to disperse in the desired polymer matrix, ie., the nature of the amine in additive manufacturing was selected such that it solubilizes with a common solvent of the polymer. For instance, a water-soluble additive was prepared using ethylene diamine which was subsequently added to a polyethylene oxide (PEO) which had water as a common solvent. The choice of amine made it possible to add this additive to several polymers which made this approach more versatile in nature. This approach can be a termed as “green” technique due to the absence of halogenated, phosphorous or boron containing compounds which releases toxic smoke during suppressing the fire

Boron Nitride Colloidal Solutions, Ultralight Aerogels and Freestanding Membranes through One-Step Exfoliation and Functionalization

Manufacturing of aerogels and membranes from hexagonal boron nitride (h-BN) is much more difficult than from graphene or graphene oxides because of the poor dispersibility of h-BN in water, which limits its exfoliation and preparation of colloidal solutions. Here, a simple, one-step mechano-chemical process to exfoliate and functionalize h-BN into highly water-dispersible, few-layer h-BN containing amino groups is presented. The colloidal solutions of few-layer h-BN can have unprecedentedly high concentrations, up to 30 mg ml-1, and are stable for up to several months. They can be used to produce ultralight aerogels with a density of 1.4 mg cm-3, which is ~1,500 times less than bulk h-BN, and freestanding membranes simply by cryodrying and filtration, respectively. The material shows strong blue light emission under ultraviolet excitation, in both dispersed and dry state

Fire Pattern Analysis, Junk Science, Old Wives Tales, and Ipse Dixit: Emerging Forensic 3D Imaging Technologies to the Rescue?

Forensic science is undergoing a period of transformation as legal and scientific forces converge and force older forensic sciences toward a new scientific paradigm. Fire investigative undertakings are not an exception to this trend. Skeptical defense attorneys who routinely formulate astute Daubert challenges to contest the scientific validity and reliability of every major forensic science discipline are one catalyst to this revolution. Furthermore, a steady influx of novel scientific advances makes possible the formulation of consistent and scientifically-based quantitative forensic evidence analyses to overcome the “undervalidated and oversold” problems affecting many areas of forensic science

Evaluation of FDS V.4: Upward Flame Spread

NIST\u27s Fire Dynamics Simulator (FDS) is a powerful tool for simulating the gas phase fire environment of scenarios involving realistic geometries. If the fire engineer is interested in simulating fire spread processes, FDS provides possible tools involving simulation of the decomposition of the condensed phase: gas burners and simplified pyrolysis models. Continuing to develop understanding of the capability and proper use of FDS related to fire spread will provide the practicing fire engineer with valuable information. In this work three simulations are conducted to evaluate FDS V.4\u27s capabilities for predicting upward flame spread. The FDS predictions are compared with empirical correlations and experimental data for upward flame spread on a 5 m PMMA panel. A simplified flame spread model is also applied to assess the FDS simulation results. Capabilities and limitations of FDS V.4 for upward flame spread predictions are addressed, and recommendations for improvements of FDS and practical use of FDS for fire spread are presented