Shonali Nazare

Smoke, CO, and CO2 Measurements and Evaluation using Different Fire Testing Techniques for Flame Retardant Unsaturated Polyester Resin Formulations

Smoke is considered to be the main fire hazard but its production depends on major variables, principally the chemical character and the burning rate of the polymer plus the availability of oxygen and hence ventilation. The main aim of this work is to study the effect of smoke suppressants on flammability and smoke production of flame retarded unsaturated polyester resin-nanocomposites using four different testing regimes representing different fire scenarios. Samples containing zinc borate, zinc stannates, ammonium polyphosphate with and without nanoclay are analyzed for smoke generation using cone calorimetry (well-ventilated fire), a tube furnace (fully developed fire), and a smoke density chamber (under-ventilated fire). Carbon monoxide (CO) and carbon dioxide (CO2) measurements using thermogravimetry-evolved gas analysis (TG-EGA), cone calorimetry, and tube furnace have also been analyzed and compared. Results have confirmed that the production of smoke, CO, and CO2 depend upon smoke suppressants and fire conditions used during testing samples. From this study it is evident that tin additives have very little influence on flammability of unsaturated polyester resin but they reduce smoke formation. The slight flame retardant action of the Res/APP/ZB sample is due to enhanced cross-linking of APP in the presence of zinc borate, whereas zinc stannates do not promote cross-linking of APP and hence show no improvement in flame retardancy. Finally, the presence of nanoclay in flame retarded resin shows significant reduction in smoke formations in both well-ventilated and under-ventilated fire condition. However, in the presence of smoke suppressants used in this study, the nanoclay is not instrumental in further suppressing smoke formation.

Quantification of Zinc Hydroxystannate** and Stannate** Synergies in Halogen-containing Flame-retardant Polymeric Formulations

Zinc stannate and hydroxystannate are used as synergists in fire-retardant systems in conjunction with halogenated species where their behavior is generally considered to be similar to antimony-containing synergists while offering the additional properties of smoke suppression and relative nontoxicity. The literature most often compares relative synergistic behaviors qualitatively but this article determines such behavior quantitatively using Lewin’s synergistic effectiveness parameter, ES, calculated from sample limiting oxygen index (LOI) data. Flame-retardant formulations comprising zinc stannate (ZS), zinc hydroxystannate (ZHS), or antimony III oxide (ATO) in combination with selected and polymer-compatible bromine-containing flame retardants were formulated in commercial grades of poly(vinyl chloride) (PVC)), thermoset polyester resin, and polyamide 6. PVC formulations simulated both commercial cable and plastisol applications and comprised either a phthalate or aryl phosphate ester as plasticizer in combination with selected synergists. All formulations were subjected to flammability testing using LOI, UL94 (vertical sample mode), and cone calorimetric (including smoke analysis) methods. For all PVC/synergist combinations containing the phthalate plasticizer, synergy was evident with 2.0 > ES > 1.0 and a relative effectiveness order ATO > ZHS > ZS. Zinc borate present as a cosynergist also has a quantifiable, positive effect. In the presence of the phosphate ester plasticizer, the reverse order is observed with marginal levels of synergy being evident (1.2 > ES > 1.0). In polyester resin formulations, ATO and ZHS exhibit similar levels of synergy when present with dibromoneopentyl diglycol with the former being superior when decabromodiphenyl ether is the flame retardant. However, in all polyamide 6 formulations, the highest levels of synergistic effectiveness are observed (ES ≥ 5.0) with ZS. Maximum values of ES correspond to a molar ratio of Sn/Br<0.3 suggesting the formation of SnBr2 and SnBr4 as the effective flame-retarding species.

A Review of Fire Blocking Technologies for Soft Furnishings

Fire barrier fabrics are expected to play an increasingly important role in complying with existing and proposed soft furnishing flammability regulations in the US. The number of commercial fire blocking technologies is large in order to accommodate the vast requirements of the consumers, manufacturers, and regulatory agencies. Generally, highloft, nonwoven fiber battings are used in residential mattress applications, whereas coated or laminated textiles are more common in institutional and upholstered furnishing applications. Successfully achieving the desired level of fire protection requires appropriate matching of the barrier fabric to the desired characteristics of the soft furnishing. Barrier material selection for soft furnishings is generally a process of trial and error due to significant measurement science gaps.In 2009, the National Institute of Science and Technology and American Fiber Manufacturers Association held a workshop on fire blocking barrier fabrics for soft furnishings to discuss the past, present, and future state of the barrier materials in the US. This manuscript is based on knowledge obtained from the workshop and the subsequent knowledge gathered from literature and stakeholders. Several fire blocking technologies have been explored to reduce the flammability of soft furnishings by preventing or delaying direct flame impingement and heat transfer from the flames or molten polymer to the core components. While previous studies reported on use of fire barriers to comply with full-scale testing of soft furnishing items, they failed to report on assessment of barrier materials as isolated components. In addition to a few examples that demonstrate the complexity that makes a priori selection of fire barrier materials difficult, various fire blocking technologies are discussed in this report with respect to material type, fiber content, and fire blocking mechanisms. Potential test methods for characterizing barrier performance are reviewed. Future trends in fire blocking materials are also briefly described.

Effects of fire retardants and nanofillers on the fire toxicity

Four polymers, polyamide 6, polypropylene, ethylene vinyl acetate and polybutylene terephthalate have been prepared with fire retardants, nanofillers, (both separately and together). The toxic product yield of each material has then been measured under different fire conditions. The influence of polymer nanocomposites and fire retardants in the formulations, on the yields of toxic products from fire, have been studied using the ISO 19700 steady state tube furnace, and it was found that under early stages of burning more carbon monoxide may be formed in the presence of nanofillers and fire retardants, but, under the more toxic under-ventilated conditions, there was a relative reduction in the toxic product yields. In general, the differences between the samples containing fire retardants and nanofillers are very small compared to the differences obtained under different fire conditions or in the presence of certain heteroelements, such as nitrogen or halogens.

Study of the Relationship Between Flammability and Melt Rheological Properties of Flame-Retarded Poly(Butylene Terephthalate) Containing Nanoclays

Recent studies on a new class of flame retardant (FR) systems that contain nanoclay and conventional FR microparticles have shown that the threshold concentration of FR required to achieve acceptable levels of flame retardancy can be significantly reduced in the presence of nanoclay. Bourbigot et al...

Factors for Consideration in an Open-Flame Test for Assessing Fire Blocking Performance of Barrier Fabrics

The main objective of the work reported here is to assess factors that could affect the outcome of a proposed open flame test for barrier fabrics (BF-open flame test). The BF-open flame test characterizes barrier effectiveness by monitoring the ignition of a flexible polyurethane foam (FPUF) layer placed in contact with the upper side of the barrier fabric, exposed to a burner flame from below. Particular attention is given to the factors that influence the ignitibility of the FPUF, including thermal resistance, permeability, and structural integrity of the barrier fabrics (BFs). A number of barrier fabrics, displaying a wide range of the properties, are tested with the BF-open flame test. Visual observations of the FPUF burning behavior and BF char patterns, in addition to heat flux measurements on the unexposed side of the barrier fabrics, are used to assess the protective performance of the BF specimen under the open flame test conditions. The temperature and heat transfer measurements on the unexposed side of the BF and subsequent ranking of BFs for their thermal protective performance suggest that the BF-open flame test does not differentiate barrier fabrics based on their heat transfer properties. A similar conclusion is reached with regard to BF permeability characterized at room temperature. However, the outcome of this BF-open flame test is found to be heavily influenced by the structural integrity of thermally degraded BF. The BF-open flame test, in its current form, only ignited FPUF when structural failure of the barrier was observed.

Effects of Fire Retardants and Nanofillers on Fire Toxicity

Four polymers, polyamide 6, polypropylene, ethylene vinyl acetate and polybutylene terephthalate have been prepared with fire retardants, nanofillers, (both separately and together). The toxic product yield of each material has then been measured under different fire conditions. The influence of polymer nanocomposites and fire retardants in the formulations, on the yields of toxic products from fire, have been studied using the ISO 19700 steady state tube furnace, and it was found that under early stages of burning more carbon monoxide may be formed in the presence of nanofillers and fire retardants, but, under the more toxic under-ventilated conditions, there was a relative reduction in the toxic product yields. In general, the differences between the samples containing fire retardants and nanofillers are very small compared to the differences obtained under different fire conditions or in the presence of certain heteroelements, such as nitrogen or halogens.