Thermal Decomposition Of Polyurethane Foams Research Articles

Cage Nanofillers' Influence on Fire Hazard and Toxic Gases Emitted during Thermal Decomposition of Polyurethane Foam.

Polyurethane (PUR), as an engineering polymer, is widely used in many sectors of industries. However, the high fire risks associated with PUR, including the smoke density, a high heat release rate, and the toxicity of combustion products limit its applications in many fields. This paper presents the influence of silsesquioxane fillers, alone and in a synergistic system with halogen-free flame-retardant compounds, on reducing the fire hazard of polyurethane foams. The flammability of PUR composites was determined with the use of a pyrolysis combustion flow calorimeter (PCFC) and a cone calorimeter. The flammability results were supplemented with smoke emission values obtained with the use of a smoke density chamber (SDC) and toxicometric indexes. Toxicometric indexes were determined with the use of an innovative method consisting of a thermo-balance connected to a gas analyzer with the use of a heated transfer line. The obtained test results clearly indicate that the used silsesquioxane compounds, especially in combination with organic phosphorus compounds, reduced the fire risk, as expressed by parameters such as the maximum heat release rate (HRRmax), the total heat release rate (THR), and the maximum smoke density (SDmax). The flame-retardant non-halogen system also reduced the amounts of toxic gases emitted during the decomposition of PUR, especially NOx, HCN, NH3, CO and CO2. According to the literature review, complex studies on the fire hazard of a system of POSS-phosphorus compounds in the PUR matrix have not been published yet. This article presents the complex results of studies, indicating that the POSS-phosphorous compound system can be treated as an alternative to toxic halogen flame-retardant compounds in order to decrease the fire hazard of PUR foam.

Thermogravimetric and qualitative analysis of thermal decomposition characteristics of polyurethane foams based on polyols with carbamide or oxamide and borate groups

The thermal stability and the kinds of products of thermal decomposition of polyurethane foams modified with urea or oxamide and borate groups were studied. Incorporation of urea or oxamide groups and borate groups enhances the thermal stability of polyurethane foams compared to polyurethane foams based on typical polyols. Thermal stability of foams modified with oxamide groups is somewhat higher that of foams modified with urea groups. In turn, simultaneous incorporation of borate groups results in an increase in thermal stability of the foams modified with urea. The temperature of thermal decomposition of the foams with oxamide and borate groups does not change or undergoes a slight decrease. The thermal degradation products of investigated foams are similar and they are usually water, ammonia, carbon dioxide and/or nitrous oxide. Additionally, hydrogen cyanide can be released during thermal decomposition of polyurethane foams modified with urea groups. The presence of borate groups prevents the formation of hydrogen cyanide. The opposite situation is observed in the case of the foams modified with oxamide and borate groups. Thus, from the point of view of a fire hazard, the use of the foams modified with urea and borate groups is safer. © 2017 Society of Chemical Industry

Polyurethane foams chemically reinforced with POSS—Thermal degradation studies

Thermal degradation of rigid polyurethane foams chemically modified by polyhedral silsesquioxanes was analyzed using hyphenated techniques – thermogravimetry (TG) coupled with FTIR spectroscopy and quadrupole mass chromatography (QMS). Two functionalized POSS were used – PHI-POSS as pendant group to the main PU chain and OCTA-POSS which acts as a chemical crosslinking agent due to the presence of eight OH-terminated side chains.Based on thermogravimetric data, thermal stabilization effect of POSS particles on PU foamed matrix was found and it was evidenced by shift of the initial decomposition temperature. The TG/FTIR/QMS studies showed that the thermal decomposition of polyurethane foams reinforced with POSS starts from about 150°C via urethane linkages scission. In lower temperature region the materials decompose to some low molecular weight compounds and intermediates with ether/ester and alcohol groups. At the temperature above 350°C evolution of hydrocarbons, aldehydes, alcohols, ethers, glycols, amines, cyclic species and low molecular weight compounds—carbon monoxide, carbon dioxide, water and ammonia was recorded. The evolution profiles of degradation products proved that POSS influences the mechanism of PU decomposition.

Flame retardant flexible polyurethane foams from novel DOPO-phosphonamidate additives

In this work we report synthesis and flame retardant application of novel 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) based phosphonamidates. Two mono and one bis DOPO-phosphonamidates were synthesized and incorporated in polyether based polyurethane (PU) manufacturing process. For the comparison of fire performance of these DOPO-phosphonamidates, we have chosen commercially available flame retardants (TCPP, DOPO and Exolit® OP 560) commonly used in flexible PU foam manufacturing. UL94 HBF fire results of various PU foam formulations indicate that DOPO-phosphonamidates exhibit superior fire performance as compared to the commercial flame retardants. 6,6′-(ethane-1,2-diylbis-(azanediyl)-bis-(6H-dibenzo[c,e][1,2]-oxaphosphine-6-oxide (EDAB-DOPO))/foam formulations exhibit the best fire performance as compared to other DOPO-phosphonamidate/foam formulations. A concentration of only 5% EDAB-DOPO on wt. of polyol is needed to achieve a HF1 rating. Thermal decomposition studies of the DOPO-phosphonamidate/foam formulations indicate their limited condensed phase interaction. In TGA experiments, a very small residue (<5%) was observed at 800 °C for all PU formulations. Additionally EDAB-DOPO showed evidence of intermediate condensed phase interaction in the first stage of PU foam decomposition. Direct insertion probe (DIP) – MS studies indicate that mono DOPO-phosphonamidates volatilize primarily in the first stage of thermal decomposition of PU foams whereas the EDAB-DOPO, being thermally more stable is only detected in gas phase in the second stage. Like in case of TCPP/PU foam formulation, the increase in the CO/CO2 ratio in the cone calorimeter experiments for the DOPO-phosphonamidate/foam formulation further proves the gas phase activity (flame inhibition) of these DOPO-phosphonamidates. EDAB-DOPO being thermally more stable seems to offer more sustained gas phase activity during the entire burning stage of PU foams in cone calorimeter experiments. Higher thermal stability of EDAB-DOPO may explain its superior flame retardant efficacy among all the DOPO-phosphonamidates investigated in this study.

Thermal decomposition kinetics of rigid polyurethane foam and ignition risk by a hot particle

ABSTRACTRigid polyurethane foam, one kind of building insulation material used in China, is prone to being ignited by hot particles from fireworks or welding processes and has been the fuel for some catastrophic fire accidents. Thermal decomposition has long been recognized to play an important role in the ignition and fire‐spreading processes of materials, and thus, it is important to understand the behavior and kinetics of material decomposition. In this study, the characteristics of the thermal decomposition of polyurethane foam were investigated in an air atmosphere with nonisothermal thermogravimetry and differential scanning calorimetry (DSC). Model‐free (isoconversional) methods and model‐fitting methods were used to study the decomposition kinetics. The results reveal that the decomposition process of polyurethane foam in air presented three main stages: the loss of low‐stability organic compounds (bond fission of the weakest link in the chain), oxidative degradation of organic components, and oxidative degradation of residue material. A scheme containing three consecutive reactions was proposed to describe the decomposition process, and good agreement was found between the experimental and simulated curves. The heat during decomposition was calculated from DSC measurement. On the basis of the kinetics and heat of decomposition, the critical conditions for a hot particle to ignite polyurethane foam was evaluated, and this was helpful for the understanding the ignition risk of polyurethane foam. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 39359.

Soft-type polyurethane foams derived from molasses

Molasses (ML)-based soft-type polyurethane (PU) foams were successfully prepared by controlling evolved heat during chemical reaction. Two kinds of isocyanate, poly(phenylene methylene) polyisocyanate (MDI) and tolylene diisocyanate (TDI), and polypropylene glycol with a long molecular chain length were utilized to control the chemical reaction. The hydroxyl group in ML was used as the reaction site and soft-type PU foams were synthesized at isocyanate (NCO)/hydroxyl group (OH) ratios of 1.05. Mechanical properties of the above foams were controlled by changing the mixing ratio of MDI and TDI. Pore size and distribution were measured by scanning electron microscopy. With increasing thickness of cell wall, compression strength and modulus increased. Thermal properties of PU foams were investigated by differential scanning calorimetry, thermogravimetry, and thermal conductivity measurements. Two-step glass transition temperatures were observed at around ca. −55 and 80 °C, regardless of kind of isocyanate. The low temperature side glass transition is attributed to the molecular motion of long oxyethylene chains and the high temperature side transition is caused by rigid components including saccharide components. Thermal decomposition of PU foams started from ca. 270 °C. Thermal conductivity of soft-type PU was observed in a range from 0.034 to 0.035 J s−1 m−1 K−1.

Characterization of polyurethane foams prepared from non-pretreated liquefied corn stover with PAPI

Polyurethane foams were prepared through co-polymerization of non-pretreated liquefied corn stover (LCS) and polymethylene polyphenylisocyanate (PAPI). The effects of [NCO]/[OH] ratio on the chemical structure and the thermal properties were studied by means of Fourier transform infrared spectroscopy (FT-IR), differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The urethane linkages and the free isocyanate groups in co-polymerization were detected from FT-IR analysis. Thermal decomposition of polyurethane foams occurred in four main successive stages. With the increasing [NCO]/[OH] ratio, the glass transition temperature (Tg) and the initial decomposition temperature increased from −36.12 and 52.18 to 1.20 and 73.30°C, respectively. And the range of Tg expanded from 26.39 to 57.12°C. On a préparé des mousses de polyuréthane par la copolymérisation de canne de maïs liquéfiée (CML) non prétraitée et l'isocyanate de polyphényle polyméthylène (IPP). On a étudié les effets du rapport [NCO]/[OH] sur la structure chimique et les propriétés thermiques par le biais de la spectroscopie infrarouge à transformée de Fourier (FTIR), la calorimétrie à balayage différentiel (CBD) et la thermogravimétrie. Les liaisons d'uréthane et les groupes d'isocyanates libres dans la copolymérisation ont été détectés à partie de l'analyse de la FTIR. La décomposition thermique des mousses de polyuréthane s'est produite dans quatre étapes principales successives. Avec le rapport [NCO]/[OH] croissant, la température de transition vitreuse (Tg) et la température de décomposition initiale se sont accrues de −36,12°C et 52,18°C à 1,20°C et 73,30°C, respectivement. De plus, la portée de la Tg s'est accrue de 26,39°C à 57,12°C.

Cyanide

Hydrogen cyanide gas and liquid, cyanide salts and their derivatives (acetonitrile, acrylonitrile, cyanamide, nitroprusside and thiocyanates) are used widely in industry. Cyanides are components of electroplating solutions, fertilizers, fumigant mixtures, metal polishes and rodenticides. Acrylonitrile is used in the production of synthetic rubber. Cyanide poisoning may occur as a result of inhalation or ingestion of cyanide, or one of its salts or derivatives. Hydrogen cyanide and other organic cyanides are released during thermal decomposition of polyurethane foams used in the manufacture of furniture, and contribute to mortality in smoke inhalation. Prolonged or excessive therapeutic use of nitroprusside may lead to cyanide toxicity and metabolic acidosis. Cyanide poisoning may also result from ingestion of the cyanogenic glycoside amygdalin (vitamin B17), which is found in the kernels of almonds, apples, apricots, cherries, peaches, plums and other fruits.

Uncertainty analysis of decomposing polyurethane foam

Sensitivity/uncertainty analyses are necessary to determine where to allocate resources for improved predictions in support of our nation’s nuclear safety mission. Yet, sensitivity/uncertainty analyses are not commonly performed on complex combustion models because the calculations are time consuming, CPU intensive, nontrivial exercises that can lead to deceptive results. To illustrate these ideas, a variety of sensitivity/uncertainty analyses were used to determine the uncertainty associated with thermal decomposition of polyurethane foam exposed to high radiative flux boundary conditions. The polyurethane used in this study is a rigid closed-cell foam used as an encapsulant. The response variable was chosen as the steady-state decomposition front velocity. Four different analyses are presented, including (1) an analytical mean value (MV) analysis, (2) a linear surrogate response surface (LIN) using a constrained latin hypercube sampling (LHS) technique, (3) a quadratic surrogate response surface (QUAD) using LHS, and (4) a direct LHS (DLHS) analysis using the full grid and time step resolved finite element model. To minimize the numerical noise, 50 μm elements and approximately 1 ms time steps were required to obtain stable uncertainty results. The complex, finite element foam decomposition model used in this study has 25 input parameters that include chemistry, polymer structure, and thermophysical properties. The surrogate response models (LIN and QUAD) are shown to give acceptable values of the mean and standard deviation when compared to the fully converged DLHS model.

Decomposition of organohalogen compounds in municipal solid waste incineration plants. Part II: Co-combustion of CFC containing polyurethane foams

The thermal decomposition of polyurethane foams containing chlorofluorocarbon 11 (CFC-11) was studied both in the KfK test facility TAMARA and in a municipal solid waste incinerator (MSWI). At technically feasible PUF feeds and typical combustion temperatures the CFC-11 destruction is 99.999 % in TAMARA and 99.998 % in the MSWI. The CFC-11 emission exceeds only slightly the background level in ambient air. Up to 50 % of the chlorine and fluorine fed in by CFC-11 were released into the flue gas as hydrohalogens, which are removed by modern APC systems without problems.