Polyester fibers flame retardent additives

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. 

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). 

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). 

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. 

Our original goal of making thermoplastic phosphorus containing polymers was considered a technical success. However, we weren t able to commercialize any of them. So this technical success was a commercial failure for us. About twenty some years later, the Japanese chemists from Toyobo Ltd. (6) prepared a polymer using phenylphosphonic dichloride and sulfonyl bisphenol as the dihydroxy reactant. That polymer called Heim Additive (equation 11) was considered seriously for use as an additive type of flame retardant for polyester fibers. 

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. 

The properties of these polyesters coupled with their ease of synthesis from relatively cheap and available raw materials serve to make them commercially attractive. The bisphenol A polyesters possess a high heat deflection temperature, high impact resistance, are transparent and inherently flame retardant. In addition, similar polyesters from tetrachlorobisphenol A (CAPE) or tetrabromobis-phenol A (BRAPE) can yield fibers with even better flame retardant properties. 

PCT displays a high deflection temperature (HDT) consistent with its high melting point which enables it to be used in glass-fiber reinforced formulations resistant to elevated temperatures. Usual formulations for injection molding contain 30-40 % of glass fiber as well as other additives, such as low molecular weight aliphatic polyesters, in order to increase the crystalizability of PCT. In some applications, thermal stabilizers and flame retardant bromide and antimony aromatic derivatives are also added (14,118). 

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