Vinyl using FTIR spectroscopy

Characterization of Vinyl Polymer Blends using FTIR Spectroscopy... 

It is necessary to be able to identify and quantify the additives in polymers and vibrational spectroscopy is a particularly useful approach to this problem. Compared with traditional chemical analyses, vibrational methods are nondestructive and are time-and cost-effective as well as more precise. A large number of examples exist in the literature. For example, antistatic agents (polyethylene glycol (PEG) in polyethylene (PE)) can be detected directly using FTIR sampling (367). An IR spectroscopic technique for the analysis of stabilisers (2, 6-di-tert-butyM-methylphenol) in PE and ethylene-vinyl acetate (EVA) copolymer has been described (368). It is possible to quantify the amount of external and internal lubricants (stearic acid in polystyrene (PS)) (371). Fillers in polymers can also be analysed (white rice husk ash (predominantly silica in polypropylene (PP)) (268). Raman spectroscopy has been used to detect residual monomer in solid polymethyl methacrylate (PMMA) samples (326). 

By measuring the presence of functional groups at finite depths from the crystal surface by real time ATR-FTIR spectroscopy, the conversion during acrylate polymerisations was measured. By varying the film thickness, the reactivity of multiacrylates could be spatially resolved (262). The simultaneous monitoring of vinyl acetate (VA) and erucamide additive concentrations in EVA copolymers was undertaken with NIR spectroscopy using an in-line flow cell attached to an extruder (130). 

Specific interactions in binary blends of ethylene-vinyl acetate copolymer with various low molecular weight terpene-phenol tackifying resins (TPR) were systematically investigated, as a function of the composition of the blend and of the electron acceptor ability of the resin, by using attenuated total reflection FTIR spectroscopy. Molecular acid-base were evidenced between TPR hydroxyl groups and EVA carbonyl groups. Quantitative information on the fraction of acid-base bonded entities, the enthalpy and equilibrium constant of pair formation were obtained. A crystalline transition of the EVA copolymer was observed and discussed in terms of enthalpy and entropy considerations based on FTIR and calorimetric DSC investigations. Fundamental results are then summarised to predict the interfacial reactivity of such polymer blends towards acid or basic substrates. 16 refs. 

The use of photoacoustic FTIR spectroscopy in quantitative analysis of polymers was investigated with reference to determination of vinyl acetate in EVA, acrylonitrile in NBR, ethylene in EPDM, styrene in SBR and vinyl-butadiene in SBR. The results obtained indicated that, despite the theoretical complexities of photoacoustic FTIR spectroscopy, simple quantitative relationships could be found for many of these polymer analyses. 24 refs. 

The sensitivity of FTIR spectroscopy to microscopic defects is greatly increased compared to a macroscopic measurement - if the defective area is examined. As opposed to single element, wide beam spectroscopy where the spectrum from the entire sample is obtained, the polymer does not overshadow the contaminant if a spectrum from a microscopic area of the sample is obtained. The contaminant can be later identified from a library of known compounds, providing clues to process control and helping to maintain quality control. This approach has been used to identify gel inclusions in poly(ethylene) [28, 29], contaminant on the surface of a semi-conductor device [30], acrylic fiber on a microcircuit die (Fig. 4) [31], contaminants in poly(vinyl chloride) (PVC) [32] and a mold release agent on the surface of a polyurethane [ 33 ]. An additive (erucamide) in linear low density polyethylene (LLDPE) that was found to migrate to the surface [34] thereby changing the surface properties could be readily identified. Various contaminants, whether in a... 

Many cable sheaths are mamrfactured from heavily filled polymers, and TGA has been foimd to be of immeasurable value in studies of such materials and some of their ingredients. The combination of the weight-loss curve, for quantitative analysis, with the derivative, for a qualitative interpretation, has been found to be particularly powerful for these applications particularly when taken together with data obtained by the other thermal methods already discussed but also with that obtained by FTIR spectroscopy. In addition the vinyl acetate content of ethylene-vinyl acetate (EVA) copolymer used in the preparation of some sheathing formulations has been measured and used as a confirmation of grade. 

PP-g-MA (0.1 mol% MA). Characterization methods included SEM, ESCA, and interfacial tension measurement. Tselios et al. (1998) have prepared compatibilized blends of LDPE and PP through inclusion of PP-g-MA (0.8 mol% MA) and EVAl (7.5 mol% vinyl alcohol). Blends were characterized using SEM, torque rheometry, mechanical properties, FTIR, and micro-Raman spectroscopy. 

NMR spectroscopy can be used to characterize these carbon skeletons, relatively large sample amounts (10-100 p,g) in nearly pure form are required. Frequently, natural product chemists are fmstrated by the unavailability of large samples. But, they can be characterized by GC/ FTIR. Svatos and Attygalle" have demonstrated that GC/ FTIR data allow definitive deductions to be made about the stereochemistry of carbon-carbon double bonds conjugated to a vinyl group. 

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