Study of flame retardants

Air Products, a manufacture of latex binders, has completed a comprehensive study of flame retardants for latex binder systems. This study evaluates the inherent flammability of the major polymer types used as nonwovens binders. In addition, 18 of the most common flame retardants from several classes of materials were evaluated on polyester and rayon substrates. Two of the most widely recognized and stringent small scale tests, the NFPA 701 vertical burn test and the MVSS-302 horizontal burn test, are employed to measure flame retardancy of a latex binder-flame retardant system. Quantitative results of the study indicate clear-cut choices of latex binders for flame retardant nonwoven substrates, as well as the most effective binder-flame retardant combinations available. 

Tkac, A. Radical process in polymer burning and its retardation. II. An ESR study of flame retardation of polypropylene. /. Polym. Sci. Polym. Chem. Ed., 19, 1495 (1981)... 

Broad Studies of Flame Retardants. Several broad studies of health, safety, and environmental factors of flame retardants have been published by public agencies. A critical review by a US government-appointed toxicology panel was conducted to facilitate CPSC regulations on flammability of furniture upholstery (145). The panel found ammonium polyphosphate, alumina trihydrate, zinc borate, hexabromocyclododecane, decabromodiphenyl ether (oxide), PYKOVATEX CP, and THPC to be usable with minimum risk on residential furniture even with worst-case assumptions. Antimony trioxide, several organophosphates, chlorinated paraffins, and molybdate salts were said to need more exposure studies. 

The behaviour of materials in the application environment where photochemical degradation is sensitized by dyes is also important. This is reflected in thermoanalytical studies of flame-retardant polyester-cotton blends where the THPC-Urea-PVBR and THPON-ammonia treatments have been compared. 

On-line pyrolysis-FTIR studies of evolved degradation products from polymeries provide rapid, unique information that is useful in formulating fire retardant materials. PyFTIR studies of flame retarded cotton fabrics [853] have been used to retrieve information on evolved gases and condensibles in dependence on the pyrolysis temperature. 

Research sponsored by BFRIP regarding the use of brominated flame retardants shows that there is no evidence that the use of decabromodiphenyl oxide leads to any unusual risk. In addition, a study by the National Bureau of Standards (now National Institute of Science and Technology) showed that the use of flame retardants significantly decreased the ha2ards associated with burning of common materials under reaUstic fire conditions (73). Work ia Japan confirms this finding (74). 

Recent advances in the application of ultrafine talc for enhanced mechanical and thermal properties have been studied [12]. A particularly important use is of finely divided filler in TPO as a flame-retardant additive. In a representative formulation, 37 parts of E-plastomer, Ml 2.0, density 0.92, 60 parts of amorphous EPR, and 4 parts of fine carbon black were dry blended, kneaded at 180°C, pelletized, and press molded into test pieces, which showed oxygen index 32 versus 31 in the absence of a filler. The oxygen index is a measure of flame retardancy. 

There are literally hundreds of flame retardants commercially available for nonwoven polyester and rayon. These can be subdivided into durable and nondurable. In this paper, non-durable means water soluble in room temperature water. Durable means able to withstand at least five washes in hot water with detergent. Flame retardants with performance somewhere in between, often called semi-durable, were not utilized in this study. Table III is a compilation of the flame retardants included in the study. Compositions include ... 

While there are a large number of both phosphorus additive and comonomer compounds available, no direct comparisons have been reported between the effectiveness of the two methods of incorporation, aside from some references to the lack of permanency of many additive compositions. The use of additives, on the other hand, may provide a greater flexibility, allowing the production of polymeric compositions of varying degrees of flame retardance, from the same base resin. The purpose of this study was to determine whether any real differences in effectiveness are detectable due to the method of incorporation of phosphorus into a polymer system. 

This paper reports the results of a molecular-level investigation of the effects of flame retardant additives on the thermal dedompositlon of thermoset molding compounds used for encapsulation of IC devices, and their implications to the reliability of devices in molded plastic packages. In particular, semiconductor grade novolac epoxy and silicone-epoxy based resins and an electrical grade novolac epoxy formulation are compared. This work is an extension of a previous study of an epoxy encapsulant to flame retarded and non-flame retarded sample pairs of novolac epoxy and silicone-epoxy compounds. The results of this work are correlated with separate studies on device aglng2>3, where appropriate. 

D. Price, F. Gao, GJ. Milnes, B. Ehng, C.I. Lindsay, and T.P. McGrail, Laser pyrolysis/time-of-fhght mass spectrometry studies pertinent to the behavior of flame-retarded polymers in real fire situations. Polym. Degrad. Stab., 64, 403 110 (1999). 

Day, M., Suprunchuk, T., and Wiles, D. M., Combustion and pyrolysis of poly(ethylene terephthalate) II. Study of the gas-phase inhibition reactions of flame retardant systems, J. Appl. Polym. Sci., 1981, 26, 3085-3098. 

Hornsby, P.R. and Watson, C.L., A study of the mechanism of flame retardancy and smoke suppression in polymers filled with magnesium hydroxide, Polym. Deg. Stab., 30, 73-87,1990. 

X-ray diffraction (XRD) has been poorly used to characterize the carbon phase of intumescent structure. Indeed, as shown previously, the carbon structure resulting from the development of the intumescent system is mainly disordered whereas XRD characterizes ordered structure. However, this technique may be of interest to study the carbonization process in the case of flame-retardant systems containing layered additives, such as expandable graphite,28,42 or even more in the case of lamellar nanocomposites, such as MMT-based nanocomposites. 

The selective treatments of flame-retardant plastics are fulfilled when the WEEE plastics are treated (recovered, recycled, thermally disposed) together with other wastes, as is the case with energy recovery processes that are currently practiced in Europe.78 79 In this scenario, the joint recovery of plastics containing brominated flame-retardants with other materials complies with the purpose of the WEEE Directive without the removal requirement of Annex II. Recent technical studies and legal reviews demonstrate that WEEE plastics containing brominated flame-retardants are compatible with the EU WEEE Directive without separation and removal prior to the waste treatment. This has been confirmed by the 2006 EU Member States guidance on the separation requirements of the WEEE Directive.80... 

Quantitative risk assessments have been performed on a variety of flame-retardants used both in upholstered furniture fabric and foam. The National Research Council performed a quantitative risk assessment on 16 chemicals (or chemical classes) identified by the U.S. Consumer Product Safety Commission (CPSC). The results were published in 2000.88 The 16 flame-retardants included in this NRC study were HBCD, deca-BDE, alumina trihydrate, magnesium hydroxide, zinc borate, calcium and zinc molybdates, antimony trioxide, antimony pentoxide and sodium antimonate, ammonium polyphosphates, phosphonic acid, (3- [hydroxymethyl]amino -3-oxopropyl)-dimethylester, organic phosphonates, tris (monochloropropyl) phosphate, tris (l,3-dichloropropyl-2) phosphate, aromatic phosphate plasticisers, tetrakis (hydroxymethyl) hydronium salts, and chlorinated paraffins. The conclusions of the assessment was that the following flame-retardants can be used on residential furniture with minimal risk, even under worst-case assumptions ... 

Most of the previous studies on flame retardation of polymer nanocomposites are focused on the relationship between macroscopic morphologies of chars and the flammability properties. Fang et al. studied the relationship between evolution of the microstructure, viscoelasticity and graphitization degree of chars and the flammability of polymers during combustion (68). The flame retar-dancy of ABS/clay /MWNTs nanocomposites was strongly affected by the formation of a network structure. Flammability properties... 

Ion-pair extraction and IPC were combined to analyze phosphoric acid mono- and diesters originating from the microbial hydrolysis of flame retardants. Even tertiary treatment did not ensure complete removal of the studied compounds detected in municipal wastewater [107], Chlorophenols extracted from water samples as anionic chlorophenolates were studied by IPC because the anionic forms of these analytes provide better UV ultraviolet absorption than uncharged chlorophenol based on their auxochromic effects. IPC conditions yielded adequate retention of the charged analytes and good sensitivity [108]. 

Present research efforts aim mainly at obtaining the important parameters from a study of the macrokinetics of combustion. It is important to estimate the effects of flame retardants, chemical structure of the polymer and polymer composition on variations of the solid- and gas-phase reaction kinetics. 

---