Phthalate plasticizers oxidation

Aryl phosphates were introduced into commercial use early in the twentieth century for flammable plastics such as cellulose nitrate and later for cellulose acetate.26 In vinyls (plasticized), arylphos-phates are frequently used with phthalate plasticizers. Their principal applications are in wire and cable insulation, connectors, automotive interiors, vinyl moisture barriers, plastic greenhouses, furniture upholstery, and vinyl forms. Triarylphosphates are also used, on a large scale, as flame-retardant hydraulic fluids, lubricants, and lubricant additives. Smaller amounts are used as nonflammable dispersing media for peroxide catalysts. Blends of triarylphosphates and pentabromodiphenyl oxide are extensively used as flame-retardant additives for flexible urethane foams. It has been also... 

Glyceryl hydrogenated rosinate plasticizer, mats Asphalt, oxidized plasticizer, mech. foam Diphenyl octyl phosphate plasticizer, mech. goods Asphalt, oxidized plasticizer, medical tubing Epoxidized soybean oil plasticizer, melamine Trishydroxyethyl triazine trione plasticizer, membranes Dinonyl phthalate plasticizer, metalworking Propylene glycol laurate plasticizer, metalworking fluids Octyl stearate... 

In actual practice, tin stabilizers are often quite complex. There are products on the market that are both carboxylates and mercaptides, made by reaction of dialkyltm oxides with esters in the presence of a tin mercaptide. If a stearate ester is used, the product has increased lubricating value if a phthalate ester is used, it does not, but may be more useful in phthalate-plasticized flexible PVC applications. Blends of different carboxylates and mercaptides may be used. Some reverse esters are claimed to have —S— bridges between two tin atoms, as in thiobis[monomethyltin-bis(2-mercaptoethyloleate)] ... 

Initially, common phthalate plasticizers were included in die extremely hazardous substances list (Section 311) of Title III SARA, but this has since been corrected. But many usual plastics compounding ingredients still remain Usted and must be reported. For example, EPA denied a petition from a vinyl stabilizer company to de-list antimony tris(isooctylmercaptoacetate), a well known PVC stabilizer, since it considers the oxide decomposition products to be possible carcinogens. 

Fig. 2. The effect of antimony oxide on the oxygen index of poly(vinyl chloride) plasticized with dioctyl phthalate (DOP), (—...

In plasticizer manufacture, eg, of phthalates or sebacates, uskig sulfuric or/ -toluenesulfonic acid catalysts, the temperature (140—150°C) requked for rapid reaction and high conversion may dehydrate or oxidize the alcohol and may yield a dark or foul-smelling product. Neutral titanates do not cause such side reactions. Although a temperature of 200°C is requked, esterifications can easily be forced to over 99% conversion without the formation of odors or... 

Between 250 and 450°F (121 and 232°C), plastics used include glass or mineral-filled phenolics, melamines, alkyds, silicones, nylons, polyphenylene oxides, polysulfones, polycarbonates, methylpentenes, fluorocarbons, polypropylenes, and diallyl phthalates. The addition of glass fillers to the thermoplastics can raise the useful temperature range as much as 100°F and at the same time shortens the molding cycle. 

Moisture Deteriorating effects of moisture are well known as reviewed early in this chapter (OTHER BEHAVIOR, Drying Plastic). Examples for high moisture applications include polyphenylene oxide, polysulfone, acrylic, butyrate, diallyl phthalate, glass-bonded mica, mineral-filled phenolic, chlorotrifluoroethylene, vinylidene, chlorinated polyether chloride, vinylidene fluoride, and fluorocarbon. Diallyl phthalate, polysulfone, and polyphenylene oxide have performed well with moisture/steam on one side and air on the other (a troublesome... 

Dimensional stability There is plastics with very good dimensional stability, and they are suitable where some age and environmental dimensional changes are permissible. These materials include polyphenylene oxide, polysulfone, phenoxy, mineral-filled phenolic, diallyl phthalate, epoxy, rigid vinyl, styrene, and various RPs. Such products will gain from an after-bake for dimensional stabilization. Glass fillers will improve the dimensional stability of all plastics. 

Organotin compounds such as monobutyltin oxide, the main substance used, accounting for 70% of consumption, dibutyltin oxide, monooctyltin oxide, and dioctyltin oxide are used in certain esterification and transesterification reactions, at concentrations between 0.001% and 0.5% by weight. They are used in the production of substances such as phthalates, polyesters, alkyd resins, fatty acid esters, and adipates and in trans-esterifications. These substances are in turn used as plasticizers, synthetic lubricants, and coatings. Organo-tins are used as catalysts to reduce the formation of unwanted by-products and also provide the required colour properties (ETICA, 2002). 

Salthammer et al. (1999) examined emissions from commonly available coatings used on furniture and identified numerous oxidation products. These were observed without the addition of oxidants such as ozone, indicating that oxidation in air (perhaps including photodecomposition for some compounds) under typical conditions is sufficient to generate such products. For example, emissions of 2-ethylhexanol were identified from di-2-ethylhexyl phthalate, used as a plasticizer in many coatings. 

Nylon, polyacetal, polycarbonates, poly(2,6-dimethyl)phenylene oxide (PPO), polyimides, polyphenylene sulfide (PPS), polyphenylene sulfones, polyaryl sulfones, polyalkylene phthalates, and polyarylether ketones (PEEK) are stiff high-melting polymers which are classified as engineering plastics. The formulas for the repeating units of some of these engineering plastics are shown in Figure 1.15. 

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