ZnS as fire retardant in plasticised PVC

The flame retardant effect of zinc sulphide (ZnS) in plasticised poly(vinyl chloride) (PVC‐P) materials was investigated. PVC‐P containing different combinations of additives such as 5% ZnS, 5% of antimony oxide (Sb₂O₃) and 5% of mixtures based on Sb₂O₃ and ZnS were compared. The thermal degradation and the combustion behaviour were studied using thermogravimetry (TG), coupled with FTIR (TG–FTIR) or with mass spectroscopy (TG–MS), and a cone calorimeter, respectively. A detailed and unambiguous understanding of the decomposition and release of the pyrolysis products was obtained using both TG–MS and TG–FTIR. The influence of ZnS, Sb₂O₃ and the corresponding mixtures on the thermal decomposition of PVC‐P was demonstrated. Synergism was observed for the combination of the two additives. The combustion behaviour (time to ignition, heat release, smoke production, mass loss, CO production) was monitored versus external heat fluxes between 30 and 75 kW m^?2 with the cone calorimeter. Adding 5% of ZnS has no significant influence on the fire behaviour of PVC‐P materials beyond a dilution effect, whereas Sb₂O₃ works as an effective fire retardant. Synergism of ZnS and Sb₂O₃ allows the possibility of replacing half of Sb₂O₃ by ZnS to reach equivalent fire retardancy. © 2002 Society of Chemical Industry     

An assessment of PVC smoke

The conventional test method for evaluating the potential of a material to produce smoke in a real fire is the NBS Smoke Density Chamber. However there are major problems with this approach. These include foremost the fact that its results do not correlate with those of real fires. Furthermore, materials that melt and drip are able to achieve a favorable, but misleading, evaluation because a significant fraction of the sample escapes the burning process. Another problem is that the test takes no account of the role the rate or extent of material burning plays in controlling the smoke density in a real fire situation. The physical problems are solved by material smoke production evaluation techniques based on measurements from the Cone Calorimeter rate of heat release apparatus, which has been developed by the National Bureau of Standards. A smoke parameter has been developed, calculated from cone calorimeter measurements, which reflects the smoke hazard of a real fire. The smoke evolution characteristics for a series of rigid thermoplastic materials have been measured using the cone calorimeter and the smoke parameter concept. The results demonstrate that due to its tendency to resist ignition and to burn very slowly, PVC would produce very little smoke in a real fire situation. Of the 15 materials tested, the expected real fire smoke performance characteristics of PVC were superior to those of all other materials except one.     

氧化亚酮和三氧化钼对PVC阻燃和抑烟作用

用锥形量热仪（CONE）研究Cu2O/MoO3体系对PVC的阻燃和抑烟协同效应可以同时获得气相和凝聚相的综合信息。实验结果表明：Cu2O/MoO3对PVC的总热释放量（THR），表现出了一定的协同阻燃作用，其原因是Cu2O/MoO3改变了PVC的热解途径，协同降低了PVC炭骨架的热裂解速度，增加了残余炭的生成量。综合分析可知，Cu2O/MoO3对PVC的阻燃协同作用有现在凝聚相中，抑烟协同作用同时表现在凝聚相和气相中。     

Synergistic flame retardant effects of activated carbon and molybdenum oxide in poly(vinyl chloride)

The synergistic effects of activated carbon (AC) and molybdenum oxide (MoO₃) in improving the flame retardancy of poly(vinyl chloride) (PVC) were investigated. The effects of AC, MoO₃ and their mixture with a mass ratio of 1:1 on the flame retardancy and smoke suppression properties of PVC were studied using the limiting oxygen index and cone calorimeter tests. It was found that the flame retardancy of the relatively cheaper AC was slightly weaker than that of MoO₃. In addition, the incorporation of AC and MoO₃ greatly reduced the total heat release and improved smoke suppressant property of PVC composites. When the total content of AC and MoO₃ was 10 phr, PVC/AC/MoO₃ had the lowest peak heat release rate and peak smoke production rate values of 173.80 kW m^?2 and 0.1472 m² s^?1, which represented reductions of 47.3 and 59.9%, respectively, compared with those of PVC. Furthermore, thermogravimetric analysis and gel content tests were used to analyze the flame retardant mechanism of AC and MoO₃, with results showing that AC could promote early crosslinking in PVC. Char residue left after heating at 500 °C was analyzed using scanning electron microscopy and Raman spectroscopy, and the results showed that MoO₃ produced the most compact char, with the smallest and most organized carbonaceous microstructures. © 2017 Society of Chemical Industry     

Melaminium molybdate smoke and fire retarders for poly(vinyl chloride)

Melaminium molybdates are shown to be very effective smoke and fire retarder additives for PVC. In a simple tin stabilized rigid PVC compound the preferred melaminium β-octa-molybdate outperformed MoO₃ and other common molybdenum smoke retarders. Combinations of melaminium molybdates with compounds of copper formed very efficient smoke-reducing and char-forming synergistic additive systems for PVC. For example, combining the octamolybdate with a series of different copper compounds consistently gave smoke reductions of about 85% in the flaming mode of the NBS Smoke Chamber at a total additive level of 5 parts per hundred parts of PVC. These large reductions in smoke were accompanied by large increases in the amount of char formed and retained as combustion residues.     

Flame retardancy of ceramic-based rigid polyurethane foam composites

In this work, ceramic fillers zirconia and alumina powder were incorporated in the rigid polyurethane foams derived from modified castor oil and their impact on the mechanical, thermal, and fire performances of composite foams have been analyzed. It was observed that the addition of ceramic filler showed improved mechanical and thermal properties and best properties were shown by 6% zirconia with compressive strength of 6.61 MPa and flexural strength of 5.72 MPa. Zirconia also demonstrated an increase in T_5% up to 260 °C. Cone calorimetry shows a decrease in peak of heat release from 118 to 84 kW m⁻² and 94 kW m⁻² by the incorporation of alumina and zirconia powder, respectively. Furthermore, total heat release (THR), smoke production rate (SPR), and total smoke release (TSR) were also found to decrease remarkably on the incorporation of ceramic fillers. So, these fillers have a great potential as an additive to incorporate good mechanical, thermal, and fire properties in bio-based rigid PU foams. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48250.     

利用锥形量热仪研究聚氨酯硬泡的燃烧性能

利用锥形量热仪对硬质聚氨酯泡沫(RP UF)的燃烧特性进行了研究.通过对RP UF燃烧过程中的热释放速率、热释放总量、烟生成速率和总产烟量等进行系统性测试,讨论了聚醚多元醇、聚酯多元醇以及异氰酸酯指数(R值)对RP UF热危险性和烟气危险性的影响.结果表明,聚酯多元醇替代聚醚多元醇制备的RP UF燃烧过程中的热释放速率...     

The functional role of molybdenum trioxide as a smoke retarder additive in rigid poly(vinyl chloride)

The most effective smoke retarders for poly(vinyl chloride) are compounds of transition metals, such as molybdenum trioxide. MoO₃ when added to a rigid PVC compound shows three general effects. First, smoke formation is reduced dramatically as measured either by the NBS smoke chamber test or Goodrich smoke–char test. Second, volatile aromatic pyrolyzate formation is also reduced dramatically. The “pure” conjugated aromatic compounds (particularly benzene and naphthalene) are reduced more than the “mixed” aliphatic–aromatic compounds (such as toluene). Third, char formation is effectively promoted. Based on results from studying MoO₃ (and other metal-;based additives) in regular, perdeuterated, and syndiotactic PVC, we propose a “reductive coupling” scheme as the dominant mechanism to explain the smoke retarder action. In this mechanism the MoO₃ acts in the condensed phase to promote extensive crosslinking of the PVC polymer chains very early in the thermal degradation process. Specifically, the metal additive forms a redox catalyst system which promotes intermolecular crosslinking of polymer chains to form char, rather than the conventional degradation process which gives rise to aromatics and smoke.     

Flammability of GRP for use in ship superstructures

The burning characteristics of glass-reinforced panels with an isophthalic polyester resin, the same resin with an inorganic flame retardant, two differing vinylester resins or a resole phenolic as the matrix were tested at a range of incident heat flux values using a cone calorimeter. The phenolic composite was superior at all levels showing a longer ignition time, reduced heat output, less contribution to a low-level sustained fire (25 kWm^?2) and lower smoke yield.     

Burning behaviors of selected chlorosilanes and SiH‐containing siloxanes

Chlorosilanes are silanes containing the Si‐Cl functional group and SiH‐containing siloxanes are siloxanes containing the Si‐H functional group. Some chlorosilanes and SiH‐containing siloxanes present potentially high fire or explosion hazards during handling, storage, transport and process operations. Cone calorimeter tests have been used to study the burning behaviors of selected chlorosilanes and SiH‐containing siloxanes at various incident heat fluxes to simulate pool fire burning. The peak heat release rate of a silicon intermediate obtained from the cone calorimeter at 15 kW/m² incident heat flux was very close to that measured by a relatively large‐scale field test. The flammability of monochlorosilanes was similar to that of organic hydrocarbons having comparable volatility. The flammability of chlorosilanes descends in the order of monochlorosilanes, dichlorosilanes and trichlorosilanes. SiH‐containing siloxanes ignited faster than non‐SiH‐containing siloxanes because of the reactive silicon‐hydrogen linkages. The ignition of SiH‐containing siloxanes was much more violent than the ignition of non‐SiH‐containing siloxanes. The SiH‐containing siloxanes exhibited a lower peak heat release rate, less total heat released and a lower peak smoke extinction coefficient compared with non‐SiH‐containing siloxanes having comparable volatility. Copyright © 2004 John Wiley & Sons, Ltd.     

Comparison of cone and OSU calorimetric techniques to assess the flammability behaviour of fabrics used for aircraft interiors

Two test methods for measuring the heat release rate, HRR have been compared on fabric composites used for aircraft interior materials as side‐wall panels. These methods are based on the principles of direct measurement of the convective and radiant heat by thermopiles using an Ohio State University (OSU) calorimeter, and oxygen consumption using a cone calorimeter. It has been observed when tested by standard procedures, cone results at 35 kW/m² incident heat flux do not correlate with OSU results at the same heat flux. This is because in the cone calorimeter, the sample is mounted horizontally whereas the OSU calorimetric method requires vertical sampling with exposure to a vertical radiant panel. A further difference between the two techniques is the ignition source—in the cone it is spark ignition, whereas in the OSU it is flame ignition; hence, samples in the OSU calorimeter ignite more easily compared to those in the cone under the same incident heat fluxes. However, in this paper we demonstrate that cone calorimetric exposure at 50 kW/m² heat flux gives similar peak heat release results as the 35 kW/m² heat flux of OSU calorimeter, but significantly different average and total heat release values over a 2 min period. The performance differences associated with these two techniques are also discussed. Moreover, the effects of structure, i.e. type of fibres used in warp/weft direction and design of fabric are also analysed with respect to heat release behaviour and their correlation discussed. Copyright © 2005 John Wiley & Sons, Ltd.     

Mechanical properties of fire‐damaged glass‐reinforced phenolic composites

Changes to the mechanical and physical properties of a glass‐reinforced resole phenolic composite due to intense radiant heat and fire are investigated. Fire testing was performed using a cone calorimeter, with the composite exposed to incident heat fluxes of 25, 50, 75 or 100 kW/m² for 325 s and to a constant flux of 50 kW/m² for different times up to 1800 s. The post‐fire tensile and flexural properties were determined at room temperature, and these decreased rapidly with increasing heat flux and heat exposure time due mainly to the chemical degradation of the phenolic resin matrix. The intense radiant heat did not cause any physical damage to the composite until burning began on exposure to a high heat flux. The damage consisted of cracking and combustion of the phenolic matrix at the heat‐exposed surface, but this only caused a small reduction to the mechanical properties. The implication of the findings for the use of glass‐reinforced resole phenolic composites in load‐bearing structures for marine craft and naval ships, where fire is a potential hazard, is discussed. Copyright © 2000 John Wiley & Sons, Ltd.     

Controlled-atmosphere cone calorimeter studies of silicones

A controlled-atmosphere cone calorimeter was used to investigate the burning of a silicone fluid and two silicone elastomers. The silicone materials were tested at 50 kW/m² incident heat flux in environments containing 15–30% oxygen. The test results were compared with a high molecular weight hydrocarbon fluid and an ethylene propylene rubber in terms of time to ignition, peak heat release rate and total heat released, carbon monoxide yield and carbon monoxide production rate, and smoke production and smoke production rate. The data from this study show that when materials burn in oxygen-enriched, normal, and vitiated atmospheres, silicone-based materials have a comparatively low peak heat release rate, total heat released, average CO production rate, and average smoke production rate as compared with organic-based materials. The smoke production and smoke production rate of silicone elastomers can be significantly reduced by adding appropriate smoke suppressants and additives. © 1997 John Wiley & Sons, Ltd.     

The Accumulation of Flammable Gases in Cone Calorimeter Tests is Responsible for Flash Ignition of Wool and Cotton Samples

In this paper a possible explanation is presented for the differences found between the fire behaviour of materials in small-scale cone calorimeter tests and the large-scale furniture calorimeter. The results obtained with cone calorimeter/FTIR equipment at 35 kW m⁻² will show that the early flash ignitions of typical materials like cotton and wool are due to the liberation of flammable gases during the pyrolysis phase and the typical ignition situation on the cone calorimeter, that is, the presence of a sparking igniter above the sample. This fast flash ignition and the early heat release behaviour on the cone calorimeter may be in contradiction to the early fire growth in other fire tests where the ignition conditions are clearly different from pyrolysis circumstances, that is, ignition via a burning newspaper, match, gas flame, etc.     

Influence of Cu2+‐organic montmorillonites on thermal decomposition and smoke emission of poly(vinyl chloride) by cone calorimetric study

Cu²⁺‐Organic montmorillonites were prepared by modifying Na⁺ montmorillonite (Na⁺‐MMT) with silane coupling agents and cupric sulfate. PVC/organic montmorillonite composites were prepared by the melt intercalation method. Morphological structure of modified MMT and PVC/MMT was obtained by using XRD and SEM. The XRD results showed that silanes and Cu²⁺ were intercalated among interlayers and that modified MMT may have exfoliated dispersion in PVC. Effects of Cu²⁺‐organic montmorillonites on decomposition and smoke emission of poly(vinyl chloride) (PVC) in the flaming mode were investigated by using a cone calorimeter at an incident heat flux of 25 kW·m^?2. Cone experimental data demonstrated that the Cu²⁺‐organic montmorillonites prepared were new effective smoke suppressants. They clearly promoted an early HCl elimination, crosslinking reactions, and char residue formation, based upon the decomposition parameters of mass loss, mass loss rate, and time of initial decomposition (t_initial). Cu²⁺‐Organic montmorillonites decreased peak heat release rate, total heat release, peak smoke production rate, total smoke production, and smoke extinction area during the flaming process. The smoke‐reducing efficiency of Cu²⁺‐organic montmorillonites (Cu²⁺‐OMMTs) was the best. However, the content of cupric ion was only 0.6–0.8% in Cu²⁺‐OMMTs and 0.03–0.04% in PVC composites. They may make the smoke‐reducing efficiency reach 45–50%. This result further demonstrates that Cu²⁺ ion is a very effective smoke suppressant for PVC. J. VINYL ADDIT. TECHNOL., 13:31–39, 2007. © 2007 Society of Plastics Engineers.     

Zinc compounds as flame retardants and smoke suppressants for rigid PVC

Abstract

The effect of the concentration of zinc hydroxy-stannate and zinc borate on the fire performance of rigid PVC formulations has been investigated. Fire testing was carried out using cone calorimetry as well as the limiting oxygen index (LOI) test. In addition, further testing was done to check that incorporation of the fire retardant additives did not have any detrimental effects on other properties of the formulated PVC, such as heat stability, colour or impact strength. The results demonstrated that zinc hydroxy-stannate is an excellent fire retardant and smoke suppressant at additions levels of 3 parts per hundred parts of PVC. Zinc borate did not have the excellent fire retardant properties of zinc hydroxy-stannate, but was found to be an efficient and cost-effective smoke suppressant, although the presence of free zinc oxide in the sample affected the thermal stability of the formulation.     

Synergistic effect of carbon and phosphorus flame retardants in rigid polyurethane foams

Two kinds of carbon and phosphorus synergistic system used to improve the flame retardancy of rigid polyurethane foams (RPUF) were studied. One is the synergistic effect of expandable graphite and guanidinium phosphate; the other is red phosphorus and guanidinium phosphate. The flame retardant properties and mechanical properties of these composites were investigated by limiting oxygen index, cone calorimeter test, as well as tension and compression test. These 2 groups of mixed inorganic flame retardants can greatly improve the flame retardancy of RPUF composites, as the limiting oxygen index increases from 20.1% to about 33% and the HRR reduces from 395 kW/m² to below 200 kW/m². It provides a convenient and inexpensive way to obtain RPUF with demanding properties.     

粉煤灰/三氧化二锑对软质聚氯乙烯阻燃消烟作用研究

将粉煤灰(Flyash)、三氧化二锑(Sb₂O₃)复合阻燃剂加入软质聚氯乙烯(PVC),制备PVC/Sb₂O₃/Flyash复合材料。通过氧指数(LOI)、TG、锥形量热、SEM等测试,探究Flyash和Sb₂O₃的协同效应,对PVC阻燃抑烟性能的影响。结果表明:当m(PVC)∶m(Sb₂O₃)∶m(Flyash)=100∶4∶3,PVC/Sb₂O₃/Flyash具有较好的阻燃抑烟性能,其LOI可达到33.9%。PVC/Sb₂O₃/Flyash的阻燃抑烟性比PVC/Sb₂O₃和PVC好。PVC/Sb₂O₃/Flyash的热释放速率降低、热稳定性增强,成炭率更高。PVC/Sb₂O₃/Flyash难点燃,火灾性能指数(FPI)大,火灾蔓延指数(FGI)小,降低火灾危险性,阻燃性能优异。     

Effect of flame heat flux on thermal response and fire properties of char‐forming composite materials

This study evaluates the effect of flame heat flux on the prediction of thermal response and fire properties of a char‐forming composite material. A simplified two‐layer flame model was developed and incorporated into a heat transfer thermal model to predict the thermal response and fire reaction characteristics of a burning material. A typical char‐forming material, E‐glass reinforced polyester composite, was used in the study. A cone calorimeter was used to measure the fire reaction characteristics of the composite. The flame heat flux in a cone calorimeter test setup was estimated using the simplified flame model. Thermal response and fire property predictions with and without the effect of flame heat flux were compared with experimental data obtained from the cone calorimeter tests. Results showed that the average flame heat flux of the composite in a cone calorimeter was 19.1 ± 6 kW/m² from model predictions. The flame had a significant effect on the thermal response and fire properties of the composite around the first heat release peak but the effect decreased rapidly afterwards. Copyright © 2012 John Wiley & Sons, Ltd.