Ethylene oxide sampling

Jet/VUV mass spectra of poly(ethylene oxide) samples. A Liqui-Nox laboratory detergent. B Reference sample with nominal Mp = 1000 A fragment series in spectrum B is labeled with asterisks. The number, n, of ethylene oxide repeat units is given for some peaks (in parentheses for fragment series). 

Materials The poly(ethylene oxide) samples used were commercial samples obtained from Shell U.K. and their structure and molecular weights are shown in Table 1. 

Pyrene is used commercially to make dyes and dye precursors. It was used by Jarroux et al. [37] as a MALDI matrix for the analysis of a poly(ethylene oxide) sample terminated with pyrene on both sides. trans-2-[3-(4-tert-Butylphenyl)-2-methyl-2-propenylidene]malononitrile is a relatively new matrix (it was introduced in 2003). This matrix possesses a very low threshold, probably lower than HABA. 

Electrospray sample deposition (ESDEP) is a sample preparation method where matrix and analyte solutions are sprayed on the target surface under the influence of a high-voltage electric field [44,45]. ESDEP is reported to yield much better shot-to-shot and spot-to-spot reproducibility than the dried-droplet method. The improved results are ascribed to the small and evenly sized crystals that are formed, and as a consequence, improved homogeneity of the MALDI sample surface. Hanton et al. [45] analyzed PEG1450, a narrowly distributed poly(ethylene oxide) sample, using an uncommon... 

Ethylene oxide samples analyzed at the OSHA Laboratory have normally been collected on activated charcoal and desorbed with carbon disulfide. The analysis is performed with a gas chromatograph equipped with a FID (Flame ionization detedor) as described in NIOSH Method S286 (Ref. 5.1). This method is based on a PEL of 50 ppm and has a detedion limit of about 1 ppm. 

The breakthrough (5% breakthrough) volume for a 3.0 mg/m ethylene oxide sample stream at approximately 85% relative humidity, 22° C and 633 mm is 2.6 liters sampled at 0.05 liters per minute. This is equivalent to 7.8 ig of ethylene oxide. Upon saturation of the tube it appeared that the water may be displacing ethylene oxide during sampling. 

Figure 14.26 (a) Exponential decay length, A, vs. Rg for four poly(ethylene oxide) samples, (b) The increase in apparent particle radius, Sa, as a function of Rg. A linear fit gives... 

Microscopic observations revealed that polymer formed during the above-mentioned process was shaped into the raspberry-like particles (see Figure 2). The diameters of particles formed in the absence of poly( ethylene oxide) were in the range of 25-100 jm, whereas the diameters of particles formed by polymerization in the presence of poly(ethylene oxide) (samples with Mn equal to 15 000 and 40 000 were used in the studies)... 

Fig. 3.32 H-decoupled NMR spectrum of a sample of linear poly (ethylene oxide) with hydroxyl end-groups. The (weak) absorptions at 6 72.5, 70.1 and 61.2 are due to the atoms nearest the chain-ends, and are shifted from that of the main-chain atoms at 6 70.3 because of effects arising from the hydroxyl end-groups. From the ratio of the integrations for the end-group absorptions to that for the main-chain absorption, the number-average molar mass of the poly (ethylene oxide) sample is calculated to be 1500g mol (courtesy of F. Heatley).

Dilatometric or optical studies allow the degree of crystallinity to be measured as a function of time. Details of the complete crystallization process can then be analyzed. Figure 12.17 is an example of the change in the level of crystallinity as a function of time at the indicated shear rate for a poly(ethylene oxide) sample, M = 7x 10. (68) The enhancementofthe crystallization rate with increasing shear rate is quite clear in these plots. The isotherms become much steeper with shear rate. 

Analysis for Poly(Ethylene Oxide). Another special analytical method takes advantage of the fact that poly(ethylene oxide) forms a water-insoluble association compound with poly(acryhc acid). This reaction can be used in the analysis of the concentration of poly(ethylene oxide) in a dilute aqueous solution. Ereshly prepared poly(acryhc acid) is added to a solution of unknown poly(ethylene oxide) concentration. A precipitate forms, and its concentration can be measured turbidimetricaHy. Using appropriate caUbration standards, the precipitate concentration can then be converted to concentration of poly(ethylene oxide). The optimum resin concentration in the unknown sample is 0.2—0.4 ppm. Therefore, it is necessary to dilute more concentrated solutions to this range before analysis (97). Low concentrations of poly(ethylene oxide) in water may also be determined by viscometry (98) or by complexation with KI and then titration with Na2S202 (99). 

Polymers. Studies to determine possible exposure of workers to residual epichl orohydrin and ethylene oxide monomers in the polymers have been done. Tests of warehouse air where Hydrin H and Hydrin C are stored showed epichl orohydrin levels below 0.5 ppm. Air samples taken above laboratory mixing equipment (Banbury mixer and 6" x 12" mill) when compounds of Hydrin H or C were mixed gave epichl orohydrin levels below detectable limits, and ethylene oxide levels less than 0.2 ppm, well below permissible exposure limits (46). A subacute vapor inhalation toxicity study in which animals were exposed to emission products from compounded Parel 58 suggests that no significant health effects would be expected in workers periodically exposed to these vapors (47). 

Ethylene oxide is sold as a high purity chemical, with typical specifications shown ia Table 14. This purity is so high that only impurities are specified. There is normally no assay specification. Proper sampling techniques are critical to avoid personal exposure and prevent contamination of the sample with trace levels of water. A complete review and description of analytical methods for pure ethylene oxide is given ia Reference 228. 

The phase behavior of several polybibenzoates with oxyalkylene spacers has been reported [11,14,15,20-27]. These spacers include the dimer of trimethylene glycol and different ethylene oxide oligomers. The most noticeable characteristic of these polybibenzoates with ether groups in the spacer is the considerable decrease of the rate of the mesophase-crystal transformation. Thus, Fig. 8 shows the DSC curves corresponding to a sample of poly[oxybis(trimethylene)p,p -bibenzoate], PDTMB, with a structure similar to that of P7MB but with the... 

A prepolymer is made first by charging Pluracol E2000 [1000.0 g, 1.0 eq., poly(ethylene oxide), 56 OH, BASF] to a suitable container equipped with a mechanical stirrer and a nitrogen gas inlet. Flush the container with dry nitrogen and add Desmodur W (264.0 g, 2.0 eq., 4,4 -methylene-bis(cyclohexyl isocyanate), 31.8% NCO, Bayer). While maintaining a positive N2 pressure on the reaction mixture, stir and heat at 80°C for 2 h. Cool the product to room temperature and check the NCO content (theory = 3.32 %). It might be necessary to warm the highly viscous prepolymer to take samples for titration. To a portion of this prepolymer (250.0 g, 0.2 eq.), add Dabco T-12 (0.25 g, dibutyltin dilaurate,... 

The stability characteristics of two different antiperspirant lotion systems were compared. Sample 1 represented an aqueous emulsion containing an aluminum salt. The internal phase consisted of stearyl alcohol and ethylene oxide reaction products, polyoxyethylene sorbitan monostearate and polyoxyethylene sorbitan tristearate. Methylcellulose was used as a stabilizer and bodying agent. Sample 2 represented a dispersion of magnesium aluminum silicate in an aqueous system containing aluminum ions. Because of its com-... 

Figure 7 shows the quasi identity of the ethylene-oxide distributions of the Genapol samples, analyzed at the outlet of the porous medium. For nonylphenols with 14 and 30 EO, we also checked that the distribution of these nonionic agents (injected in a concentration of 5 g/1) was not appreciably changed after transit via the adsorbent porous medium. Under these conditions, the mixed micelles formed... 

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