Combustion Calorimeter Research Articles

Synthesis, characterization and flame retardant of UV-curable hybrid coatings containing SiO2–P2O5–B2O3 via sol–gel method

A ternary sol containing silicon, phosphorus and boron modified by γ-methacryloxypropyltrimethoxysilane was synthesized by sol–gel method. The ternary sol was incorporated into the organic matrix and UV-curable organic/inorganic hybrid coating materials were obtained. Hardness, transmittance, haze, cross-cut adhesion and abrasion resistance results showed that the mechanical properties of the hybrid coatings improved effectively with no comprising on optical properties by increasing sol content. Scanning electron microscopy and Energy Dispersive X-ray spectrometer studies indicated that inorganic particles were homogenously dispersed in the organic matrix. The flame retardancy of the UV-curable coatings was investigated by thermogravimetric analysis and microscale combustion calorimeter. The results showed that the incorporation of sol into the organic network led to an improvement in the thermal stability and flame retardancy of the hybrid coating materials. It is a desirable achievement to improve simultaneously both flame retardancy and mechanical properties of the coatings.

Synergistic Effect of Polyhedral Oligomeric Silsesquioxane on the Flame Retardancy and Thermal Degradation of Intumescent Flame Retardant Polylactide

In this study, intumescent flame retardant polylactide/trisilanolisobutyl polyhedral oligomeric silsesquioxane (PLA/TPOSS) composites were prepared via melt blending method. The morphology of the PLA nanocomposites was assessed by transmission electron microscopy (TEM). The flame retardancy of the PLA/TPOSS composites was evaluated by the limiting oxygen index (LOI) test and the UL-94 test. It was observed that the addition of TPOSS had evident flame retardant effect in comparison to the results obtained from neat PLA. The PLA nanocomposite showed a 69% reduction of heat release capacity (HRC) when tested in the microscale combustion calorimeter (MCC). Thermal gravimetric analysis (TGA) showed the incorporation of intumescent flame retardant, and TPOSS had effectively delayed the thermo-oxidation process of the PLA. The thermal degradation mechanisms of the PLA/TPOSS composites were investigated by thermogravimetric analysis/infrared spectrometry (TG-IR) and direct pyrolysis/mass (DP-MS) analysis.

Novel styrene polymers functionalized with phosphorus–nitrogen containing molecules: Synthesis and properties

A phosphorus and nitrogen-containing compound with high phosphorus content, AC2NP2, was firstly synthesized by the Kabachnik–Fields reaction and followed by esterification with acryloyl chloride. The synthesized comonomer was then incorporated into different amounts of polystyrene via radical solution polymerization. The copolymers were well characterized using Fourier transform infrared (FTIR), UV/vis spectrophotometer, nuclear magnetic resonance (NMR), gel permeation chromatography (GPC), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), microscale combustion calorimeter (MCC) and LOI. The results showed that the AC2NP2 was easily incorporated into the backbone of polystyrene, and the copolymers prepared have high transparency. The glass transition temperature (Tg) of the copolymers was decreased with increasing the AC2NP2 content, due to the introduction of much more flexible molecular chain. The TGA results revealed that the introduction of AC2NP2 units slightly decreased the initial decomposition temperatures, but significantly improved the thermal stability of copolymers at high temperature regions under both nitrogen and air atmosphere. Furthermore, all the copolymers exhibited much lower flammability as compared with virgin polystyrene.

Enhanced thermal stability of polychloroprene rubber composites with ionic liquid modified MWCNTs

Thermal degradation of polychloroprene rubber (CR) composites based on unmodified and ionic liquid modified multi-walled carbon nanotubes (MWCNTs) is studied using thermogravimetric analysis (TGA) in aerobic and anaerobic (nitrogen) conditions. The CR and its composites exhibit three stage and four stage degradation in nitrogen and air respectively. The presence of unmodified CNTs alone does not improve the thermal stability of composites to a great extent whereas a reasonable enhancement is observed in case of modified CNTs/CR composites which can be attributed to the interfacial interactions of ionic liquid/modified tubes with CR and to the fine dispersion of modified tubes in CR. The degradation products of CR and its composites were analysed using pyrolysis-gas chromatography-mass spectrometry (Py-GC-MS) and the mechanism of degradation is discussed. Non-isothermal degradation kinetics were studied using Kissinger and Flynn-Wall-Ozawa methods and the activation energy of thermal decomposition is found to be high for modified CNTs/CR composites. Isothermal degradation of modified CNTs/CR composites at 290 °C for 30 min in nitrogen reveals decreased weight loss (14%) as opposed to CR (31%) and unmodified CNTs/CR composites (30%). The combustion behaviour of the composites was dealt using microscale combustion calorimeter (MCC) and the flame retardancy of the composites is discussed.

Relationships between the molecular structure and the flammability of polymers: Study of phosphonate functions using microscale combustion calorimeter

The present work is based on the Van Krevelen’s approach proposed by Lyon et al. [1] to determine the relationships between the molecular structure and the flammability of molecules using Microscale Combustion Calorimeter (MCC). Via this approach, the contributions to Heat Release Capacity (HRC) and Total Heat Release (THR) were successfully calculated for two phosphorus-containing groups: phosphonate and dioxaphosphorinane. We showed that the Van Krevelen’s approach was invalid when the molecules contain both phosphorus and ester or acid groups. We hypothesized that these functions interact between them during the thermal decomposition. In this study we propose to calculate “Interaction Indexes” to estimate the level of interactions according to the chemical structure. The results enable to draw first conclusions about the best chemical architecture for lowering flammability.

Investigation of a combination of novel polyphosphoramide and boron-containing compounds on the thermal and flame-retardant properties of polystyrene

A novel phosphorus, nitrogen-containing compound, poly(4, 4′-diaminodiphenyl methane phenyl dichlorophosphate) (PDMPD) with high thermal stability was synthesized. The PDMPD was then incorporated into polystyrene (PS) to be used as halogen-free flame retardant. Moreover, small amounts of two boron-containing compounds, Zinc borate (ZnB) and boron phosphate (BP) were combined with PDMPD,to explore effective flame-retardant formulations for PS. The flammability and the thermal properties of the composites were evaluated using limiting oxygen index (LOI) test, microscale combustion calorimeter (MCC) and thermogravimetric analysis (TGA) respectively. A Fourier transform infrared (FTIR) spectroscopy coupled with a thermogravimetric analyzer (TG-IR) was also used to study the gas phase from the degradation of PS composites. Furthermore, the char residues of the samples were investigated by scanning electron microscopy (SEM) and FTIR. The results showed that the incorporation of PDMPD can significantly decrease the flammability of virgin PS, and enhance the thermal stability at high temperature region, in both nitrogen and air atmosphere. A combination of PDMPD with small amounts of boron compounds can further decrease the flammability.

Evaluation of three flame retardant (FR) grey cotton blend nonwoven fabrics using micro-scale combustion calorimeter

Unbleached (grey or greige) cotton nonwoven fabrics (with 12.5% polypropylene scrim) were treated with three phosphate–nitrogen–based flame retardant formulations and evaluated with micro-scale combustion calorimeter. Heat release rate, peak heat release rate, temperature at peak heat release rate, heat release capacity, total heat release and char yield were determined. The peak heat release rate and total heat release results demonstrated that nonwoven fabrics treated with a formulation having higher diammonium phosphate and no dimethylol dihydroxyethyleneurea were superior to those treated with a formulation containing dimethylol dihydroxyethyleneurea. Nonwoven fabrics treated with these formulations were both superior to the nonwoven fabrics treated with a commercially available flame retardant formulation. These results were supported by the percentages of phosphorus and nitrogen on these fabrics, confirming that P–N synergism imparts high flame retardancy to the nonwoven fabrics. Grey cotton (untreated) consistently showed better flame resistance than (untreated) bleached cotton. As a result, its flame retardant products had lower heat release rate/peak heat release rate and other flammability characteristics than those of the bleached cotton. Additionally, grey cotton is softer than bleached cotton and saves the cost of bleaching and waste disposal. These three flame retardant formulations were used primarily to treat the cotton component of the nonwoven blend to make it flame retardant without flame retardant improvement for the polymer component.

Thermal behaviour modelling of a reference calorimeter for natural gas

The French National Metrology and Testing Institute (LNE) build an isoperibolic reference gas calorimeter to measure the calorific value of natural gas with a high level of accuracy with the collaboration of the R&D Division of GDF-Suez. With 3D numerical modelling tools, GDF-Suez developed a comprehensive and refined model of the complete calorimeter geometry and evaluated the heat flux sources to reproduce the thermal behaviour of this calorimeter. The objectives are to optimise the thermal homogeneity and to maximize heat transfer to the water bath. The accurate assessment of the different thermal fluxes transferred to the water bath was performed based on a complete simulation of the combustion of the fuel gas in the burner. The numerical model results fit quite closely the experimental thermal behaviour of the calorimeter. The energy balance shows that approximately 90% of the total energy is absorbed by the water bath and about 10% by the calorimetric walls with a weak contribution of the radiative heat transfer to the calorimeter vessel. A comparative study between the numerical and experimental results confirms both that the geometries of the calorimeter vessels and the glass burner are adequate. The new refined geometric model validates also the location of the thermal sensor in the bath. The expected outcome of both experiments and thermal modelling is to decrease the uncertainty of the calorific value measured with this standard combustion calorimeter.

Effect of microencapsulation on thermal properties and flammability performance of epoxy composite

The influence of microencapsulated ammonium polyphosphate (MFAPP) on flame retardancy, thermal properties and water resistance of epoxy (EP) composite were investigated by LOI, UL-94, DSC, TG, microscale combustion calorimeter (MCC) and TG-FTIR. The results of DSC show that the shell outside MFAPP can increase its compatibility in EP. EP/MFAPP containing only 9wt% MFAPP can pass V-0 in the UL-94 test, while neat EP cannot pass any rating. Due to the presence of shell, water treatment show few effects on the flame retardancy of EP/MFAPP, while LIO values of EP/APP decrease remarkably after treatment. The presence of MFAPP can reduce the heat release rate and total heat release of EP significantly in MCC test. The reason is that MFAPP can stimulate the dehydration of EP at low temperature and retard the release of pyrolysis gas at high temperature. Moreover, a char formed via the reaction of EP and MFAPP has excellent thermal stability and can prevent underlying materials from further combustion during a fire.

Synthesis and thermal behavior of a novel UV‐curable transparent flame retardant film and phosphorus‐nitrogen synergism of flame retardancy

AbstractA novel phosphorus monomer (PDHA) has been synthesized through phenyl dichlorophosphate (PDPC) reacting with 2‐hydroxyethyl acrylate (HEA). The structure of PDHA was characterized by Fourier transform infrared spectroscopy (FTIR) and 1H nuclear magnetic resonance spectroscopy (1H NMR). A series of UV curable resins were manufactured by blending PDHA with triglycidyl isocyanurate acrylate (TGICA) at different weight ratios. The fire performance was examined by micro‐scale combustion calorimeter (MCC) and limiting oxygen index (LOI). The results obtained from MCC indicated that the addition of PDHA to TGICA reduced the HRR and HRC. In addition, the LOI values varied from 28 to 34. The char residues of the composites were observed by scanning electron microscopy (SEM). Their thermal degradation behavior was investigated by thermogravimetric analysis and real time FTIR analysis (RT‐FTIR). The test results indicated that when the weight ratio of PDHA/TGICA = 1:1, the onset temperature of the composite was highest and the most char residue at 700°C was observed. RT‐FTIR showed that the phosphate group of PDHA first degraded to form poly(phosphoric acid)s at around 300°C, which had the major contribution to form the compact char to protect the sample from further degradation. Copyright © 2010 John Wiley & Sons, Ltd.

Preparation, combustion, and thermal behavior of UV‐cured epoxy‐based coatings containing layered double hydroxide

AbstractThe bisphenol A epoxy acrylate resin (EA) containing a small amount of layered double hydroxide (LDH) was cured within seconds under UV irradiation at ambient temperature. Its microstructure was characterized by X‐ray diffraction (XRD). The combustion behavior of the coating was examined by the Microscale Combustion Calorimeter (MCC) and limiting oxygen index (LOI). The results obtained from MCC and LOI indicated that the addition of LDH into EA could decrease the peak of heat release rate (HRR) for the films and increase the LOI value of the films. Thermal behavior of the cured films was studied by thermogravimetric analysis (TGA). The results for TGA indicated that with increase in the contents of LDH, the residual char of UV‐cured films increased at 600 °C. The evolved products for UV‐cured films were characterized using thermogravimetric analysis/infrared spectrometry (TGA‐IR). It was implied that the mechanism of thermal degradation for EA0 was different from EA4. Viscoelastic property of photo‐cured hybrid materials was evaluated by dynamic‐mechanical analysis. The effect of LDH on the properties of UV‐curable films was critically evaluated in this paper. Copyright © 2010 John Wiley & Sons, Ltd.

Low‐Temperature Heat Capacities and Standard Molar Enthalpy of Formation of Gramine (C11H14N2)

AbstractLow‐temperature heat capacities of gramine (C11H14N2) were measured by a precision automated adiabatic calorimeter over the temperature range from 78 to 401 K. A polynomial equation of heat capacities as a function of temperature was fitted by least squares method. Based on the fitted polynomial, the smoothed heat capacities and thermodynamic functions of the compound relative to the standard reference temperature 298.15 K were calculated and tabulated at 5 K intervals. The constant‐volume energy of combustion of the compound at T=298.15 K was measured by a precision oxygen‐bomb combustion calorimeter as ΔcU=−(35336.7±13.9) J·g−1. The standard molar enthalpy of combustion of the compound was determined to be ΔcHm0=−(6163.2±2.4) kJ·mol−1, according to the definition of combustion enthalpy. Finally, the standard molar enthalpy of formation of the compound was calculated to be Δ;cHm0=−(166.2±2.8) kJ·mol−1 in accordance with Hess law.

Iron-montmorillonite and zinc borate as synergistic agents in flame-retardant glass fiber reinforced polyamide 6 composites in combination with melamine polyphosphate

This paper presents a preliminary investigation on the effects of organically modified iron-montmorillonite (Fe-OMT) and zinc borate (ZnB) on thermal degradation behaviors and flame retardancy of melamine polyphosphate (MPP) flame-retarded glass fiber reinforced polyamide 6 (GFPA6). The samples were characterized using limiting oxygen index (LOI), UL-94 tests, thermogravimetric analysis (TGA), Fourier transform infrared coupled with the thermogravimetric analyzer (TG-FTIR) and Microscale Combustion Calorimeter (MCC) measurements. The residue after LOI test was also analyzed by Scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FTIR) and Raman spectroscopy. A substitution of a certain fraction of MPP with ZnB or Fe-OMT can significantly improve the UL-94 rating of GFPA6/MPP composites from no rating to V0 rating, exhibiting excellent flame retardacny. Based on the investigations, different flame retardant mechanisms were proposed for the two effective flame-retardant formulations.

Development and Characterization of Fire Retarded Glass-Fiber Reinforced Poly(1,4-butylene terephthalate) Composites Based on a Novel Flame Retardant System

The aim of this work was to develop halogen-free glass-fiber reinforced poly(1,4-butylene terephthalate) (GRPBT) composites with significantly improved fire retardancy performance using a novel flame retardant system. The system was composed of aluminum hypophosphite (AHP), polycarbonate (PC), and melamine cyanurate (MC). The GRPBT composite containing the system achieved a V-0 classification in UL-94 testing (the thickness of testing bar was 0.8 mm). In microscale combustion calorimeter and cone calorimeter testing, both of the two different PHRRs (peak of heat release rate) for GRPBT composites were remarkably reduced by the incorporation of the novel system. Thermogravimetric analysis and residue characterization revealed that the addition of PC promoted the formation of char residues leading to the reduction of mass loss rate, which resulted in the improvement of fire retardancy.

Effect of rare earth hypophosphite and melamine cyanurate on fire performance of glass-fiber reinforced poly(1,4-butylene terephthalate) composites

This work mainly deals with a novel flame retardant system for glass-fiber reinforced poly(1,4-butylene terephthalate) (GRPBT) composites using trivalent rare earth hypophosphite (REHP) and melamine cyanurate (MC) through melt blending method. Firstly, two types of REHP, lanthanum hypophosphite and cerium hypophosphite, were synthesized and characterized. Thermal gravimetric analysis (TGA) was employed to investigate the thermal decomposition behavior of REHP and flame retardant treated GRPBT composites. Thermal combustion properties were measured using microscale combustion calorimeter. Fire performance was evaluated by limiting oxygen index, Underwriters Laboratories 94 and cone calorimeter. The results showed that the flammability of GRPBT is significantly reduced by the incorporation of the flame retardant mixture. Mechanism analysis revealed that the addition of MC reduces the condensed phase effect of REHP, but improves the flame inhibition in gas phase.

Synergistic effects of cerium(IV) phosphate with intumescent flame retardant in styrene butadiene rubber

Cerium(IV) phosphate [CeP(IV)] was synthesised by hydrothermal synthesis and used as a synergistic agent on the flame retardancy of styrene butadiene rubber (SBR)/intumescent flame retardant (IFR) system. The IFR system mainly consisted of ammonium polyphosphate and pentaerythritol. Limiting oxygen index, UL-94 test, thermogravimetric analysis, cone calorimeter, scanning electron microscopy and microscale combustion calorimeter were used to evaluate the synergistic effects of CeP(IV). The addition of CeP(IV) to SBR/IFR composites leads to the improvement in UL-94 values of the SBR/IFR/CeP(IV) composites, and the peak of heat release rate decreases with increasing CeP(IV) content. SEM was used to analyse the morphological structure of the residue chars formed from the SBR/IFR systems with and without CeP(IV). A possible mechanism for catalysing carbonisation was discussed. The experimental results indicated that there existed a synergistic effect between CeP(IV) and IFR for the flame retardancy of SBR.

Synthesis, Characterization and Properties of New Semifluorinated Poly(arylene ether phosphine oxide)s

AbstractBis(4‐fluoro‐3‐trifluoromethylphenyl)phenylphosphine oxide is synthesized and six new poly(arylene ether)s are prepared by nucleophilic displacement of the fluorine atom on the benzene ring by several diphenols under basic conditions. The products show very high glass transition temperatures of up to 252 °C and very good thermal stabilities of up to 490 °C for 5% weight loss. The polymers display very low heat release rates in the microscale combustion calorimeter test, suggesting good flame retardance. All polymers are soluble in a wide range of organic solvents. Transparent thin films cast from dichloromethane exhibit tensile strengths up to 54 MPa, a modulus of elasticity up to 0.97 GPa and elongation at break up to 47% depending on their exact repeating unit structures.magnified image

Flame‐retarded polystyrene with phosphorus‐ and nitrogen‐containing oligomer: Preparation and thermal properties

AbstractA phosphorus‐ and nitrogen‐containing compound (2‐dimethylamino ethyl phenyl hydroxyethyl acrylate phosphate) and its oligomer (poly(2‐dimethylamino ethyl phenyl hydroxyethyl acrylate phosphate), PDPHP) were synthesized and characterized. The polystyrene (PS) composites with various amounts of PDPHP were prepared by melt blending. The thermal stability of the PDPHP and PS composites was investigated by thermogravimetric analysis. The flame retardancy of the composites was evaluated using microscale combustion calorimeter and limiting oxygen index test. A Fourier transform infrared (FTIR) spectroscopy coupled with a thermogravimetric analyzer was also used to study the gas phase from the degradation of PS composites. The char residues of the PS composites containing 30 wt % PDPHP were analyzed by FTIR and scanning electron microscopy. The results suggest that the incorporation of PDPHP into PS can evidently enhance the char formation and improve the flame retardancy of virgin PS. The compact and coherent char formed during degradation was attributed to the enhancement of char quality and flame retardance. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Synergistic effects between boron phosphate and microencapsulated ammonium polyphosphate in flame‐retardant thermoplastic polyurethane composites

Microencapsulated ammonium polyphosphate (MAPP) with polyurethane resin has been prepared by in situ polymerization. The combination of MAPP and boron phosphate (BP) on the flammability properties of thermoplastic polyurethane (TPU) was studied by vertical burning (UL‐94) tests, limiting oxygen index tests, cone calorimetry (CONE), and microscale combustion calorimeter (MCC) whereas thermal stability was investigated by thermogravimetric analysis and real‐time Fourier transform infrared. Results showed that a suitable substitution of MAPP by BP could improve flame retardancy of the TPU/MAPP composites and TPU composites with MAPP/BP (15.5/2 wt%) achieving UL‐94 V‐0 rating. The CONE and MCC data showed synergistic effects between BP and MAPP in the composites. Copyright © 2011 John Wiley & Sons, Ltd.

Experimental study on the thermochemistry of some amino derivatives of uracil

Values of the standard (p∘=0.1MPa) molar enthalpy of combustion, ΔcHm∘, of four crystalline compounds: 5-aminouracil, 6-aminouracil, 6-amino-1-methyluracil, and 6-amino-1,3-dimethyluracil, were determined, at T=298.15K, using a static bomb combustion calorimeter. The values obtained of standard molar enthalpy of combustion were used to derive the standard molar enthalpy of formation of the compounds investigated in their condensed phase and together with literature values of the standard molar enthalpy of sublimation, yielded the standard molar enthalpies of formation in the gaseous phase. These are discussed in terms of the effects of the molecular structure on the relative enthalpic stability.