Polyesters, additives Flame retardants

Historically, PEB has been used as an additive flame retardant for thermoset polyester and thermoplastic resins during the 1970s and 1980s. In 1977, the production of PEB was 45-450 metric tons [60]. The production of PEB declined to 5-225 metric tons in 1986, and in 1988, there was no ongoing or intended production or processing of this substance [60]. Information on the current manufacturers or processors of PEB is not publicly available in addition, information on the amount of PEB currently produced (if any) is confidential. However, PEB is listed as a low-production-volume chemical manufactured by Albemarle in France according to the European... 

Formulation of SMC/BMC compounds is a very sophisticated balance of many ingredients to enhance specific properties and/or act synergistically with other components. Most SMC/BMC formulations have three main elements binder, filler and fiber reinforcement, from a choice of ingredients such as unsaturated polyester resin, monomer, catalyst, inhibitor, fillers, TP anti-shrinkage additives, flame-retardant, thickener, release agent, and glass fiber reinforcement. 

Among phosphorus-containing additive flame-retardants, phosphates are mostly applied as secondary plasticizers in formulations of flame-retarded plasticized PVC. Other additive agents are admixed with natural and synthetic rubbers, polyester and epoxy resins, polyurethane foams, polystyrenes and polyethylenes, etc. 

BASF has a US patent (US 5712336) in which a thermoplastic polyester is flame-retarded with decabromodiphenylethane and two more additives. These are ... 

This liquid oligomer, Clariant s EXOLIT 5087, contains 27-28% Cl and 15% P, and is useful as an additive flame retardant for transparent cast polymethyl methacrylate, unsaturated polyester resins, or rigid polsuirethane foams. It has good light stability, but is not stable to heat above about 180°C. 

Reactive flame retardants are added to the monomers, therefore they are covalently linked in the polymer and do not significantly penetrate into the environment. The use of these substances is limited to a few groups of polymers. Additive flame retardants are added into polymers, therefore they are not covalently bound, which is associated with the higher risk of environmental contamination. PBDEs and HBCD are used only as additive flame retardants, while TBBPA is primarily a reactive flame retardant and in only about 10% of cases is it used as an additive flame retardant. For example, the HBCD content in polystyrene foam ranges from 0.4 to 8% and the TBBPA content in polyesters may reach 13-28%. 

In addition to dyeabiHty, polyesters with a high percentage of comonomer to reduce the melting poiat have found use as fusible biader fibers ia nonwoven fabrics (32,34,35). Specially designed copolymers have also been evaluated for flame-retardant PET fibers (36,37). 

Unsaturated Polyesters. There are two approaches used to provide flame retardancy to unsaturated polyesters. These materials can be made flame resistant by incorporating halogen when made, or by adding some organic halogen compound when cured. In either case a synergist is needed. The second approach involves the addition of a hydrated filler. At least an equal amount of filler is used. 

Several commercial polyester fabrics are flame retarded using low levels of phosphoms additives that cause them to melt and drip more readily than fabrics without the flame retardant. This mechanism can be completely defeated by the presence of nonthermoplastic component such as infusible fibers, pigments, or by siUcone oils which can form pyrolysis products capable of impeding melt flow (27,28). 

TrialkylPhosphates. Triethyl phosphate [78-40-0] C H O P, is a colorless Hquid boiling at 209—218°C containing 17 wt % phosphoms. It may be manufactured from diethyl ether and phosphoms pentoxide via a metaphosphate intermediate (63,64). Triethyl phosphate has been used commercially as an additive for polyester laminates and in ceHulosics. In polyester resins, it functions as a viscosity depressant as weH as a flame retardant. The viscosity depressant effect of triethyl phosphate in polyester resins permits high loadings of alumina trihydrate, a fire-retardant smoke-suppressant filler (65,66). 

Textile Flame Retardants. The first known commercial appHcation for phosphine derivatives was as a durable textile flame retardant for cotton and cotton—polyester blends. The compounds are tetrakis(hydroxymethyl)phosphonium salts (10) which are prepared by the acid-cataly2ed addition of phosphine to formaldehyde. The reaction proceeds ia two stages. Initially, the iatermediate tris(hydroxymethyl)phosphine [2767-80-8] is formed. 

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. 

In flame retarding nonwovens, the contribution of components may not be additive. Rather, the interaction of binder, flame retardant, and substrate is critical in the performance of the flame retardant nonwoven. Similarly, the flammability of a binder film or the flammability of a flame retardant coated woven cloth often do not predict the flame retardancy of the same binder or flame retardant on a nonwoven substrate of rayon or polyester. Actual data on a nonwovens substrate is the only accurate measure of a system s flame retardancy. For this study, two widely used substrates were selected. The first, lightweight rando rayon, is representative of material used in nurse caps, surgeon s masks, and miscellaneous coverstock. This material is constructed of 1 1/2 denier fiber, weighs 1 1/2 ounces per square yard, and is relatively dense web. Rayon as a material is water absorbent, burns rather than melts, and is readily flammable. This fiber ignites around 400°C(2) and has an oxygen index of about 19.0. Certain binders adhere well to rayon while others do not. Apparently, this lack of affinity for the substrate affects flame retardancy, as will be demonstrated later. 

Earlier studies at the ITRI have demonstrated the effectiveness of tin(IV) oxide, both in its anhydrous and hydrous forms, as a flame- and smoke-retardant additive for laboratory-prepared polyester resin formulations (J5j. In a recent study, carried out in collaboration with a major U.K. company, a number of inorganic tin additives have been incorporated into a commercial brominated polyester resin. Although this resin, which contains 28% by weight bromine, is intrinsically flame-retardant, giving samples with an 01 of ca. 41 and which meet the UL94-VO classification, formulations with improved flame and smoke properties are sought. 

The advantage of using a paste dispersion of a flame-retardant additive in this polyester resin formulation is evident from the... 

A further improvement in flame-retardant efficiency is observed when a colloidal dispersion of tin(IV) oxide is incorporated into the polyester. At a 1.5% addition level, colloidal SnO gives an 01 value (49.0) which is markedly higher than that obtained with 5% loadings of either anhydrous SnO, (47.7) or 8-stannic acid (47.9), as powdered additives (Figure 2). In addition to its increased flame-retardant ability, colloidal Sn02 offers the further advantages of translucency in the cured plastic, ease of incorporation and nonsettling in the resin prior to cure. 

The SSP behavior of co-polyesters with rigid or voluminous comonomers, such as the flame retardant additive 9,10-dihydro[2,3-di-9-oxa-(2-hydroxyethoxy)-carbonylpropyl]-10-phosphaphenanthrene-10-oxide, or the ionic compound, sodium 5-sulfoisophthalate, is inhibited. This also occurs in the melt phase and cannot be improved by the use of catalysts [56], The results of studies examining the influence of employed catalysts with respect to stability and quality of the polymer suggest the use of antimony catalysts. The thermal or thermo-oxidative stability is, however, reduced by the interaction of the catalyst with the carboxylic groups of the polymer [57],... 

Flammability of Phosphorus-Containing Aromatic Polyesters A Comparison of Additives and Comonomer Flame Retardants... 

Aromatic polyphosphonates have been found to be especially effective flame retardant additives for polyester compositions (j), 1, 8), especially for polyethylene terephthalate. 

In view of the utility of the aromatic polyesters and the demonstrated effectiveness of the aromatic polyphosphonates as flame retardants, the combination of these two polymers was chosen for this study. In addition, this system provided a composition in which both copolymers and polymer blends could be prepared with identical chemical compositions. The polyesters were prepared from resorcinol with an 80/20 m/m ratio of iso-phthaloyl and terephaloyl chlorides while the polyphosphonates were resorcinol phenylphosphonate polymers. Copolymerized phosphorus was incorporated by replacement of a portion of the acid chloride mixture with phenylphosphonic dichloride. 

Dicylopentadiene Resins. Dicyclopentadiene (DCPD) can be used as a reactive component in polyester resins in two distinct reactions with maleic anhydride (7). The addition reaction of maleic anhydride in the presence of an equivalent of water produces a dicyclopentadiene acid maleate that can condense with ethylene or diethylene glycol to form low molecular weight, highly reactive resins. These resins, introduced commercially in 1980, have largely displaced 0 0-phthalic resins in marine applications because of beneficial shrinkage properties that reduce surface profile. The inherent low viscosity of these polymers also allows for the use of high levels of fillers, such as alumina trihydrate, to extend the resin-enhancing, flame-retardant properties for application in bathtub products (Table 4). 

POLYARYLATES. These are clear, amorphous thermoplastics that combine clarity, high heat deflection temperatures, high impact strength, good surface hardness, and good electrical properties with inherent ultraviolet stability and flame retardance. No additives or stabilizers are required to provide these properties. Polyarylates are aromatic polyesters that are manufactured from various ratios of iso- and terephthalic acids with bisphenol A.1 The resultant products are free-flowing pellets which can be processed by a variety of thermoplastic techniques in transparent and... 

PBBs were also widely used as flame retardant additives in polymer formulations, e.g., synthetic fibers, molded plastics and plastic housings also in the manufacture of polycarbonates, polyesters, polyolefins and polystyrenes. Nixed ABS polymers (acrylonitrile -butadiene - styrene), plastics, coatings and lacquers also contained added PBBs to enhance fire-retardancy. 

Among the emerging pollutants of industrial origin, Bisphenol A [2,2 bis(4-hydroxydiphenyl)pro-pane] (BPA) has special relevance since it was one of the first chemicals discovered to mimic estrogens as endocrine disrupters.147 This compound was first reported by Dianin in 1891.1411 BPA is produced in large quantities worldwide, mainly for the preparation of polycarbonates, epoxy resins, and unsaturated polyester-styrene resins.149 The final products are used in many ways, such as coatings on cans, powder paints, additives in thermal paper, in dental composite fillings, and even as antioxidants in plasticizers or polymerization inhibitors in polyvinyl chloride (PVC). To a minor extent, BPA is also used as precursor for flame retardants such as tetrabromobisphenol A or tetrabromobisphenol-S-bis(2,3-dibromopropyl) ether.150 This substance can enter the environment... 

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