Flame-retardant Polyurethane Foams Research Articles

Evaluation on the thermal performance of external insulation system in apartment building remodelling

Thermal insulation plays a significant role in increasing building energy saving and creating comfortable indoor environment by reduction of heat transfer between indoor and outdoor environments. This study aims to investigate the insulation performance of the external insulation system applied in remodelling apartment buildings using the equivalent U-value. The results of this study indicate that thermal performance achieved by the external insulation system was improved and panel approach system is more excellent than flame-retardant polyurethane foam. The results of this study indicate that the external insulation system was investigated in this study, and the result confirms that the application of the external insulation system in remodelling apartment buildings will contribute to energy conservation. The above-mentioned results imply that external insulation system applied in remodelling apartment buildings can significantly contribute to the improvement in energy-efficient of buildings.

Preparation and characterization of flame retardant polyurethane foams containing phosphorus–nitrogen-functionalized lignin

Lignin-based phosphate melamine was used as a partial substitute for polyols to synthesize rigid polyurethane foams which exhibit high mechanical strength and low flammability.

Bi-phase flame-retardant effect of hexa-phenoxy-cyclotriphosphazene on rigid polyurethane foams containing expandable graphite

The flame-retardant rigid polyurethane (PU) foams with hexa-phenoxy-cyclotriphosphazene/expandable graphite (HPCP/EG) were prepared through box-foaming in our laboratory. The flame retardancy of PU foams was characterized using the limiting oxygen index and cone calorimeter. The results show that the incorporation of HPCP into the PU foams containing EG enhanced flame retardancy. The main degradation process of HPCP in PU foams was investigated by pyrolysis gas chromatography/mass spectroscopy. HPCP during combustion generated phenoxyl and PO2 free radicals, which could quench the flammable free radicals produced by the matrix and hamper the free radical chain reaction of combustion. This observation shows that HPCP produced a gas-phase flame-retardant effect in this specimen. Additionally, micro-morphology, elemental composition and content of residual char of the flame-retardant PU foams after the cone calorimeter test were also characterized using scanning electron microscope and energy dispersive X-ray microanalyser. The results exhibit that the partial phosphorus from HPCP remained in the residual char, and HPCP significantly enhanced the strength and compatibility of the char layer formed by the PU foams containing EG. These results indicate the important function of HPCP in condensed phase. Thus, HPCP exhibited gas-phase and condensed-phase flame-retardant effects on the PU/EG foams.

The study of mechanical behavior and flame retardancy of castor oil phosphate-based rigid polyurethane foam composites containing expanded graphite and triethyl phosphate

Abstract The goal of this work was the synthesis of novel flame-retarded polyurethane rigid foam with a high percentage of castor oil phosphate flame-retarded polyol (COFPL) derived from renewable castor oil. Rigid flame-retarded polyurethane foams (PUFs) filled with expandable graphite (EG) and diethyl phosphate (TEP) were fabricated by cast molding. Castor oil phosphate flame-retarded polyol was derived by glycerolysis castor oil (GCO), H2O2, diethyl phosphate and catalyst via a three-step synthesis. Mechanical property, morphological characterization, limiting oxygen index (LOI) and thermostability analysis of PUFs were assessed by universal tester, scanning electron microscopy (SEM), oxygen index testing apparatus, cone calorimeter and thermogravimetric analysis (TGA). It has been shown that although the content of P element is only about 3%, the fire retardant incorporated in the castor oil molecule chain increased thermal stability and LOI value of polyurethane foam can reach to 24.3% without any other flame retardant. An increase in flame retardant was accompanied by an increase in EG, TEP and the cooperation of the two. Polyurethane foams synthesized from castor oil phosphate flame-retarded polyol showed higher flame retardancy than that synthesized from GCO. The EG, in addition to the castor oil phosphate, provided excellent flame retardancy. This castor oil phosphate flame-retarded polyol with diethyl phosphate as plasticizer avoided foam destroy by EG, thus improving the mechanical properties. The flame retardancy determined with two different flame-retarded systems COFPL/EG and EG/COFPL/TEP flame-retarded systems revealed increased flame retardancy in polyurethane foams, indicating EG/COFPL or EG/COFPL/TEP systems have a synergistic effect as a common flame retardant in castor oil-based PUFs. This EG/COFPL PUF exhibited a large reduction of peak of heat release rate (PHRR) compared to EG/GCO PUF. The SEM results showed that the incorporation of COFPL and EG allowed the formation of a cohesive and dense char layer, which inhibited the transfer of heat and combustible gas and thus increased the thermal stability of PUF. The enhancement in flame retardancy will expand the application range of COFPL-based polyurethane foam materials.

The Thermal Properties of Rigid Polyurethane Foams Treated with Flame Retardant

A novel cheap macromolecular intumescent flame retardants (MIFR), was synthesized, and its structure was a caged bicyclic macromolecule containing phosphorus characterized by IR. Rigid polyurethane foam (PUF) were modified with MIFR to get the flame retardant PUF, whose flammability and burning behavior were characterized by UL 94 and limiting oxygen index (LOI). 25% of weight of MIFR were doped into PUF to get 24.5 of LOI and UL 94 V-0. The thermal properties of epoxy resins containing MIFR were investigated with thermogravimetry (TG). Activation energy for the decomposition of samples was obtained using Kissinger equation. The resultant data show that for PUF containing MIFR, compared with PUF, MIFR decreased weight loss, thermal stability, increased the char yield. The activation energy for the decomposition of EP is 205 kJ/mol while it becomes 162 kJ/mol for PUF containing MIFR, decreased by 42 kJ/mol, which shows that IFR can catalyze decomposition and carbonization of PUF.

TG–FTIR characterization of volatile compounds from flame retardant polyurethane foams materials

Flame retardant polyurethane foams materials (PUFM) composites were prepared using tricresyl phosphate (TCP) as flame retardant. The combustion and thermal degradation behaviors of flame retardant PUFM composites were investigated by microscale combustion calorimetry (MCC) and thermogravimetric analysis/infrared spectrometry (TG–IR). The results showed that TCP had excellent flame retardant abilities for PUFM. The TGA curves suggested that TCP has good ability of char formation. The volatilized products formed on thermal degradation of flame retardant PUFM indicated that the volatilized products are mainly carbonyl compounds, CO2, and esters. In addition, TCP can greatly reduce the toxic gases containing NCO groups and increase CO2 as nonflammable gases when it is incorporated into the composites.

Preparation and Characterization of Excellent Flame Retarded Rigid Polyurethane Foams

Rigid polyurethane foams were excellent thermal insulation materials with widely used, which was highly flammable at the same time. In order to obtain safe application, flame retarded polyurethane foams were needed. In this paper, series flame retarded rigid polyurethane foams were prepared with loading different flame retardants such as ammonium polyphosphate, expandable graphite, red phosphorus, Tri (2-chloroethyl) phosphate and dimethyl methylphosphonate. The effects of flame retardants on the foaming-process and flame retardant property of the rigid polyurethane foams were investigated by otary viscometer and limiting oxygen index. The results showed that the combination of solid and liquid flame retardants was necessary to improve the flame retardant and different flame retardants played synergistic roles in rigid polyurethane foams. The limiting oxygen indexes of the foams could be up to 30wt% and 29.6% with 25wt% solid flame retardants and 10wt% liquid retardants, respectively.

Influence of phosphorus valency on thermal behaviour of flame retarded polyurethane foams

This paper reports decomposition/pyrolysis studies of polyurethane (PU) rigid foams containing phosphinate, phosphonate or phosphate as flame retardant in order to study the effect of phosphorus oxidation state on their gas and/or solid phase action. The flame retardants analyzed were aluminium phosphinate (IPA), dimethylpropanphosphonate (DMPP), triethylphosphate (TEP) and ammonium polyphosphate (APP), which differ in oxidation state and/or decomposition temperature. Gases evolved during TGA analyses as well as solid residues have been studied by means of MS and FTIR. The results show that phosphorus flame retardants which significantly lose weight at temperatures lower than those of neat PU foams act in the gas phase irrespective of their valency: indeed, they are completely volatilized before polymer decomposition starts and thus no interaction between flame retardant and polymer can be expected. The effect of phosphorus oxidation state becomes important when flame retardant decomposition takes place in the same temperatures range as neat polymer. In this case, it seems that at lower P oxidation state (+1) a combined gas and solid phase action takes place while at higher P oxidation state (+5) only solid phase action was observed.

Discoloration in Fire-Retardant Flexible Polyurethane Foams

The mechanism of discoloration (‘scorch’) of water-blown flame-retardant polyurethane (PU) foams has been studied. As UV spectroscopy showed, scorch is a kinetically controlled phenomenon, and it can occur either in flame-retardant or non-flame-retardant foams. Isolated isocyanate groups in the PU structure, which transform into aromatic amines, are mostly responsible for scorch. Some flame retardants tend to accelerate scorch, and it becomes visible during industrial foaming, especially in hot and humid weather conditions. UV, FTIR, 13C and 31P NMR and GC-MS study carried out with a model aromatic amine showed that aliphatic phosphate esters as well as aliphatic chloroalkyl phosphates tend to N-alkylate aromatic amines. N-alkylated aromatic amines are easier to oxidize to colored quinoid type chromophores compared to primary aromatic amines. Discoloration can be significantly decreased by using aromatic flame retardants or by applying proper antioxidants in combination with aliphatic flame retardants.

Burning behaviour of foam/cotton fabric combinations in the cone calorimeter

The burning behaviours of polyurethane foam/cotton fabric combinations were investigated using cone calorimetry. One non-flame retarded and two flame retarded polyurethane foams containing melamine and melamine plus a chlorinated phosphate respectively, were combined with four cotton fabrics, i.e. two types of commercial cotton, one without flame retardant (CN) and another flame retarded with Proban (CPR); and another two flame retardant cottons which were treated with Pyrovatex (CPY) and (NH 4) 2HPO 4 (CDA) respectively in the laboratory.

Burning behaviour of fabric/polyurethane foam combinations in the cone calorimeter

The burning behaviour of three different flexible polyurethane foam samples covered with wool fabric has been studied in a cone calorimeter operated at a radiant flux of 35 kW m -2 . One non-flame retarded and two flame retarded polyurethane foams containing melamine and melamine plus a chlorinated phosphate, respectively, have been used. Two wool fabrics were used, one of which was flame retarded using zirconium hexafluoride (Zirpro (IWS)). Results for the polyurethane foams indicated that the presence of chlorinated phosphate in the flame retardant system results in increased levels of smoke and CO compared to when melamine only was the flame retardant. The times to ignition of the foam/fabric combinations were longer than those of the foams alone. The (peak) rates of heat release of the composite samples were dependent on the covering fabric. Smoke and CO release from the composite depended on both the foam and the fabric.

Thermal degradation of different fire retardant polyurethane foams

The thermal behaviour of four different flame retarded polyurethane foams has been investigated. For this reason simultaneous thermal analysis/mass spectrometry (TA/MS) as well as incineration experiments on laboratory scale were carried out. Additionally the evolved gases during TA/MS measurement were adsorbed on XAD-resin and identified by means of GC-MS analysis. The results were compared to those of the incineration experiments and the degradation pathways of the flame retardants are discussed.