Polypropylene oxidation, analyzed

The 100 MHz H-NMR spectrum of polypropylene oxide is too complex to be analyzed accurately even when decoupled from methyl protons. It is reasonable to ascribe the complexity of the spectrum to the spin coupling between hydrogen atoms linked to contiguous carbon atoms in the main chain. If this interpretation is correct, the spectrum should be simplified by substituting the methine proton by a deuterium atom. In fact, the spectrum of polypropylene oxide-a-d was simpler than that of the undeuterated one. Methyl protons lie at higher field and methylene protons at lower field. The stereoregularity was analyzed on the basis of the spectrum of the methylene proton absorption other than that of the methyl proton absorption. 

Environmental water samples to be analyzed for metals are best stored in quartz or Teflon containers. However, because these containers are expensive, polypropylene containers are often used. Borosilicate glass may also be used, but soft glass should be avoided because it can leach traces of metals into the water. If silver is to be determined, the containers should be light absorbing (dark colored). Samples should be preserved by adding concentrated nitric acid so that the pH of the water is less than two. The iron in well water samples, for example, will precipitate as iron oxide upon exposure to air and would be lost to the analysis if not for this acidification. 

Analyses. Samples of reaction mixtures were frozen and sublimed into the vacuum line (10-6 mm Hg). The vapor was passed through a wide-bore U-trap at —45°C which collected acetic acid and volatile oxidation products and allowed any unreacted hexenes to pass. After further fractional condensation the hexene was transferred to a graduated tube to measure the volume and was finally analyzed by GLC using a 12 meter X 6 mm column packed with polypropylene glycol LB-550-X on Chromosorb W. The sublimation residue was analyzed by IR spectroscopy while the acetic acid condensate was subjected to a wet separation (5, 15) to recover the oxidation products for GLC analysis. 

Amorphous and semi-crystalline polypropylene samples were pyrolyzed in He from 388°-438°C and in air from 240°-289°C. A novel interfaced pyrolysis gas chromatographic peak identification system was used to analyze the products on-the-fly the chemical structures of the products were determined also by mass spectrometry. Pyrolysis of polypropylene in He has activation energies of 5-1-56 kcal mol 1 and a first-order rate constant of JO 3 sec 1 at 414°C. The olefinic products observed can be rationalized by a mechanism involving intramolecular chain transfer processes of primary and secondary alkyl radicals, the latter being of greater importance. Oxidative pyrolysis of polypropylene has an activation energy of about 16 kcal mol 1 the first-order rate constant is about 5 X JO 3 sec 1 at 264°C. The main products aside from C02, H20, acetaldehyde, and hydrocarbons are ketones. A simple mechanistic scheme has been proposed involving C-C scissions of tertiary alkoxy radical accompanied by H transfer, which can account for most of the observed products. Similar processes for secondary alkoxy radicals seem to lead mainly to formaldehyde. Differences in pyrolysis product distributions reported here and by other workers may be attributed to the rapid removal of the products by the carrier gas in our experiments. 

Table 3 Apparent composition of surfaces relevant to aluminum-coated bioriented polypropylene films, obtained at two collection angles 6 and computed by considering that the analyzed zone is homogeneous film submitted to an oxidizing treatment, aluminum-coated film, surfaces obtained after the peeling test. Roughness rms measured by AFM on 2 x 2pm images...

The HRP, aniline (or PANI), and hydrogen peroxide made up a specific oxidative system based on fast reaction kinetics. Devices were developed according to this system in which any two of the three components can be used as a sensor to detect the third component. The electronic signals were collected and analyzed for changes in the electrochemical properties of the polyaniline or its derivatives when the oxidative coupling reactions occurred. Polyaniline-coated polypropylene membranes exhibited strong tendency to adsorb and immobilize HRP [68]. 

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