Phthalate Subject

For a part to exhibit stmctural stiffness, flexural moduH should be above 2000 N/mm (290,000 psi). Notched l2od impact values should be deterrnined at different thicknesses. Some plastics exhibit different notch sensitivities. For example, PC, 3.2 mm thick, has a notched l2od impact of 800 J/m (15 fdbf/in.) which drops to 100 J/m (1.9 fflbf/in.) at 6.4-mm thickness. On the other hand, one bisphenol A phthalate-based polyarylate resin maintains a 250-J /m (4.7-fdbf/in.) notched l2od impact at both thicknesses. Toughness depends on the stmcture of the part under consideration as well as the plastic employed to make the part. Mechanical properties, like electrical properties, ate also subject to thermal and water-content changes. 

In 1930, in one of many pioneering studies, Carothers showed that certain condensation polymers could be cyclic or macrocyclic rather than exclusively linear. In addition to this very important observation, he showed that thermolysis in vacuo of certain polymers could also yield macrocyclic materials. Quite a number of papers have been published on this subject since that time, especially dealing with the chemistry of phthalate " , isophthalate " ", and terephthalate esters Many of these structures are tabulated at the end of this... 

Si element ATR-FTIR spectroscopy was used to analyze this residue, and its spectrum, along with the closest library matches, are shown in Figure 41. The absorbance of this residue is low as a consequence of the thin layer present on the plate. This makes matching the sample spectrum with a reference spectrum somewhat difficult. The closest matches extracted from the library interrogated are to ester-based plasticizer materials, which is consistent with a phthalate-plasticized PVC. A more specific identification could have been made with further testing such as subjecting the residue to GC-MS analysis, but the information suggested by the ATR-FTIR analysis was, in this case sufficient. 

Eor example, in the intestinal tract and liver of both humans and animals DEHP is rapidly hydrolyzed by esterases to yield mono-(2-ethylhexyl) phthalate (MEHP) and 2-ethylhexanol [25]. The latter metabolite is subsequently oxidized enzymatically to 2-ethyl hexanoic acid (2-EHXA) [26]. MEHP, 2-hethylhexanol, and/or their metabolites are the immediate inducers of the majority of enzymes known to be affected by exposure of DEHP [27]. Due to the high importance of the primary and secondary PAE metabolites in the human exposure smdies, during the last years a big number of smdies have been conducted to prove that some of them are appropriate biomarkers to calculate human PAE intake [28-30] and that their determination is easier than calculate it through food intake, which are more time consuming and subjects to several error sources. 

Regulations on phthalate esters cover aU aspects of their production, transportation, use, and disposal. Phthalates are regulated under the Clean Water Act, so that at certain manufacturing facilities in the US, wastewater to be treated in municipal sewage treatment plants may be required to undergo pretreatment prior to leaving the facility (Pretreatment Standards).When they become waste products, certain phthalates are subject to Resource Conservation and Recovery Act [45] requirements. Releases to the environment of several phthalate esters are required to be publicly reported in the US, Canada, and Japan. 

The migration of PAEs from the polymers leads emissions to the environment during their production, transport, storage, manufacture, use, and disposal [8, 15, 40, 69]. Once in the different environmental compartments phthalates are subject to photo degradation, biodegradation, aerobic and anaerobic degradation and, thus, generally do not persist in the outdoor environment [8, 70]. 

There are many ways to obtain distance-like measures among flavor compounds. First, stimuli are generally equated in subjective intensity so that judgments are based on quality rather than intensity. Odorants are diluted in an odorless grade of diethyl phthalate and tastants, in deionized water. Then subjects rate all the n(n-l)/2 possible pairs for a set of n stimuli along an undifferentiated 5" line ... 

Although some polymers may be satisfactory when used under the stress of static loads, they may fail when subjected to impact. The impact resistance, or resistance to brittle fracture, is a function of the molecular weight of a polymer. Thus uhmwpe is much more resistant to impact failure than general purpose high-density polyethylene (hdpe). The impact resistance of brittle polymers is also increased by the addition of plasticizers. Thus polyvinyl chloride (PVC), plasticized by relatively large amounts of dioctyl phthalate, is much less brittle than unplasticized rigid PVC. 

The mortality of 221 workers in a di(2-ethylhexyl) phthalate production plant in Germany was followed between 1940 and 1976. Most subjects (135/221) were hired after 1965 and the process was completely enclosed in 1966. No information on level of exposure was provided. Information on vital status for foreigners [number not stated] was obtained for only 55% of them, but appeared to be complete for the remaining cohort. Reference rates were obtained from local populations (the city of Ludwigshafen, the Rheinhessen-Pfalz land) and national rates. Altogether, eight deaths... 

Groups of 18-20 male Fischer rats (weighing 160 g) were given a single intra-peritoneal injection of 200 mg/kg bw NDEA. Two weeks later, they were fed a diet containing 3000 ppm di(2-ethylhexyl) phthalate [purity unspecified] for six weeks. At week 3, they were subjected to a partial hepatectomy. All rats were killed at week 8. Di(2-ethylhexyl) phthalate-treated rats had no increase in foci staining positively for glutathione S-transferase placental form (8.5 per cm versus 11.6 for NDEA alone) (Ito etal., 1988). 

In a very early study, Shaffer et al. (1945) administered single oral doses of 5 and 10 g di(2-ethylhexyl) phthalate to two human subjects and reported that approximately 4.5% of the dose was excreted in the urine within 24 h. Schmid and Schlatter (1985) also administered di(2-ethylhexyl) phthalate orally to two human subjects, but at the much lower dose of 30 mg per person. These authors reported that 11-15% of the dose was excreted in the urine and a urinary elimination half-life of about 12 h can be estimated from the data. In the same study, the two volunteers also received 10 mg di(2-ethylhexyl) phthalate daily for four days, there being no evidence of accumulation, with 11 and 33 % of the dose recovered each day in the urine. In contrast, Rubin and Schififer (1976) reported data from two patients receiving platelet transfusions from bags containing di(2-ethylhexyl) phthalate, who excreted between 60 and 90% of the infused dose in the urine collected for 24 h after transfusion. 

Species differences in the metabolism of di(2-ethylhexyl) phthalate have been reported and attempts have been made to explain the susceptibility of animals to di(2-ethylhexyl) phthalate-induced hepatic peroxisome proliferation based on their metabolic profiles (Doull et al., 1999). As mentioned above, the bulk of a di(2-ethylhexyl) phthalate dose is absorbed as the mono-ester, mono(2-ethylhexyl) phthalate, and following absorption this metabolite is subjected to extensive oxidative metabolism mediated by cytochrome P450 enzymes (Albro Lavenhar, 1989 Astill, 1989 Huber et al., 1996 Doull et al., 1999). The metabolism of mono(2-ethylhexyl) phthalate has been summarized by Doull et al. (1999) as follows (see Figure 1) ... 

Male Fischer 344 rats (body weight, 100-150 g) were fed 0.5-4% di(2-ethyl-hexyl) phthalate in the diet for one or four weeks and male Swiss Webster mice (20-30 g) were fed 2 or 4% di(2-ethylhexyl) phthalate in the diet for one or four weeks (Reddy etal., 1976). Di(2-ethylhexyl) phthalate increased relative liver weights and markedly induced hepatic carnitine acetyltransferase activity in both species (up to 25-fold in rats and 10-fold in mice). Some increase in hepatic catalase activity (approximately two-fold) was observed and subjective (non-morphometric) ultra-structural examination revealed marked peroxisome proliferation. This study also demonstrated that di(2-ethylhexyl) phthalate was a hypolipidaemic agent, as serum triglyceride levels were reduced to one seventh of control values in rats and one third of control values in mice. 

Hepatocytes isolated from male Wistar rats (180-250 g) were treated with 0.2 mM mono(2-ethylhexyl) phthalate or 1 mM 2-ethylhexanol for 48 h (Gray et al., 1982). Both di(2-ethylhexyl) phthalate metabolites increased carnitine acetyltransferase activity about nine-fold. In studies with hepatocytes from male Sprague-Dawley rats (180-220 g), treatment with 0.2 mM mono(2-ethylhexyl) phthalate and 1.0 mM 2-ethylhexanol for 48 h resulted in induction of carnitine acetyltransferase activity about 15-fold and six-fold, respectively (Gray et al., 1983). Mono(2-ethylhexyl) phthalate was also shown to induce cyanide-insensitive palmitoyl-CoA oxidation and, by ultra-structural examination, to increase numbers of peroxisomes. Hepatocytes were isolated from Wistar-derived rats (180-220 g) and treated for 72 h with 0-0.5 mM mono(2-ethylhexyl) phthalate and some mono(2-ethylhexyl) phthalate metabolites (Mitchell etal., 1985). Treatment with mono(2-ethylhexyl) phthalate and metabolites VI and IX (see Figure 1) resulted in a concentration-dependent induction of cyanide-insensitive palmitoyl-CoA oxidation. In addition, 0-0.5 mM mono(2-ethylhexyl) phthalate and 0-1.0 mM metabolite VI produced concentration-dependent increases in lauric acid hydroxylation. Treatment with metabolites I and V resulted in only small effects on the enzymatic markers of peroxisome proliferation. In another study with hepatocytes from Wistar-derived rats (180-220 g), metabolite VI was shown by subjective ultrastructural examination to cause proliferation of peroxisomes (Elcombe Mitchell, 1986). 

Hepatocytes were isolated from male Wistar rats, two dogs (age, breed and sex not stated) and two human subjects (69-71 years of age, sex not stated) (Hildebrand et al., 1999). In collagen sandwich cultures, the rat hepatocytes responded to di(2-ethylhexyl) phthalate in the culture medium with slightly increased carnitine acetyltransferase activity, while dog and human hepatocytes did not respond. 

The absorption and disposition of di(2-ethylhexyl) phthalate has been investigated extensively in humans and laboratory animals. In all species studied, the compound underwent rapid metabolism, with the urine and faeces being the major routes of excretion. Following oral administration, the bulk of a di(2-ethylhexyl) phthalate dose was absorbed as the monoester, mono(2-ethylhexyl) phthalate. This ester is also formed by esterases in the body following intravenous administration and is subject to extensive oxidative metabolism by the cytochrome P450 system. 

The solvent extract should be subjected to one or more cleanup steps for the removal of interfering substances. The presence of phthalate esters, sulfur, or other chlorinated compounds can mask pesticide peaks. The extract should, therefore, be cleaned up from the interfering substances using a florisil column or by gel permeation chromatography (see Chapter 1.5). The distribution patterns for the pesticides in the florisil column fractions are presented in Table 2.20.2. 

The sample was a solution of polystyrene (PS) dissolved in dioctyl phthalate (DOP). This system has a theta temperature of approximately 22°C [183] and has been the subject of most of the studies investigating flow-induced phase transitions in polymer solutions. The particular sample used here had a molecular weight for PS of 2 million, a poly-dispersity of MW/MN = 1.06, and a concentration of 6%. This results in a semidilute... 

The opposite behavior as sketched before was detected for solutions of PS in DOP [112], Again, the critical temperature (an UCST at Tc = 12 °C in the quiescent state) turned out to be a function of the shear rate to which the solution is subjected. But, in contrast to solutions of PS and PB in DOP, here enhancements of the UCST as large as 28 °C were recorded at a shear rate of 220 s-1. Similar results have been found for PS solutions in di(2-ethyl hexyl)phthalate or in a mixture of cis- and frans-decalin [113], The solutions demixed in a converging flow from a reservoir into a capillary tube. It has been observed that an increase in the deformation rate raised the UCST or reduced the region of miscibility. In both of these studies an increase of the cloud point temperature of the polymer solutions was used as an indication of phase separation. 

It is well-known that by the addition of plasticizers the glass temperature of polymers decreases severely the glass temperature of PVC, e.g. decreases from 90 to 0 °C by the addition of 30% dioctyl phthalate and plasticized PVC finds many applications. We will come back to this important subject in Chap. 16. 

Enhancement of a flexible PVC-silica composite interface was studied by the application of gamma-aminopropyltrimethoxysilane on silane. Composites containing silica and silanised silica up to 25.6 phr and prepared by sol-gel technology were subjected to water and water vapour attacks similar to that in their daily use. Silane application resulted in diminishing liquid water and water vapour sorption by about 24.0% and 11.9%, respectively. Inhibition of dioctyl phthalate migration from composites by silane application was also determined as 24% using UV measurements. 20 refs. TURKEY... 

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