In PEs using

The introduction of EU directives on Waste Electrical and Electronic Equipment and Reduction of Hazardous Substances has highlighted the need for precise and repeatable elemental analysis of heavy metals in the plastics production process. X-ray fluorescence (XRF) spectroscopy has emerged as the most economical and effective analytical tool for achieving this. A set of certified standards, known as TOXEL, is now available to facilitate XRF analyses in PE. Calibration with TOXEL standards is simplified by the fact that XRF is a multi-element technique. Therefore a single set of the new standards can be used to calibrate several heavy elements, covering concentrations from trace level to several hundred ppm. This case study is the analysis of heavy metals in PE using an Epsilon 5 XRF spectrometer. 

Because of the double sound path involved in PE measurements of the back wall echo, we approximate the corresponding attenuation at a certain frequency to be twice as large as the attenuation that would be obtained by an ordinary TT measurement. We propose to use the logarithm of the absolute value of the Fourier transform of the back wall echo as input data, i.e... 

Software In some programmable electronic systems (PES), errors are much easier to detect and correct than in others. Using the term software, in the wider sense, to cover all procedures, as distinct from hardware or equipment, some software is much friendlier than others. Training and instructions are obvious examples. As another example, if many types of gaskets or nuts and bolts are stocked, sooner or later the wrong type will be installed. It is better, and cheaper in the long run, to keep the number of types stocked to a minimum, even though more expensive types than are strictly necessaiy are used for some applications. 

Mangipudi et al. [63,88] reported some initial measurements of adhesion strength between semicrystalline PE surfaces. These measurements were done using the SFA as a function of contact time. Interestingly, these data (see Fig. 22) show that the normalized pull-off energy, a measure of intrinsic adhesion strength is increased with time of contact. They suggested the amorphous domains in PE could interdiffuse across the interface and thereby increase the adhesion of the interface. Falsafi et al. [37] also used the JKR technique to study the effect of composition on the adhesion of elastomeric acrylic pressure-sensitive adhesives. The model PSA they used was a crosslinked network of random copolymers of acrylates and acrylic acid, with an acrylic acid content between 2 and 10%. 

MW and MWD are very significant parameters in determining the end use performance of polymers. However, difficulty arises in ascertaining the structural properties relationship, especially for the crystalline polymers, due to the interdependent variables, i.e., crystallinity, orientation, crystal structure, processing conditions, etc., which are influenced by MW and MWD of the material. The presence of chain branches and their distribution in PE cause further complications in establishing this correlation. 

Another feature in PES spectra is the so-called shake-up structures, appearing as weak satellites on the high binding energy side of the main line. The shake-up structure reflects the spectrum of the 1 -electron-2-hole states generated in connection with pholoionization, and can give useful information about the valence n-electronic structure of a molecular ion. 

A qualitatively different approach to probing multiple pathways is to interrogate the reaction intermediates directly, while they are following different pathways on the PES, using femtosecond time-resolved pump-probe spectroscopy [19]. In this case, the pump laser initiates the reaction, while the probe laser measures absorption, excites fluorescence, induces ionization, or creates some other observable that selectively probes each reaction pathway. For example, the ion states produced upon photoionization of a neutral species depend on the Franck-Condon overlap between the nuclear configuration of the neutral and the various ion states available. Photoelectron spectroscopy is a sensitive probe of the structural differences between neutrals and cations. If the structure and energetics of the ion states are well determined and sufficiently diverse in... 

Activation studies were conducted at pH 7.5 at 30°C in 20 mL of 0.5% high methoxyl citrus pectin (Citrus Colloids, Hereford, U.K.). Final cation concentration in PE extracts used for activation studies was less than 2 mM as measured by potentiometry. Controls were conducted to correct for non-enzymic alkali consumption, with no polyamine/no PE and polyamine added/no PE. PE activity was normalized as a percentage of activity with no cation addition. 

Joseph TN, Chen AL, Di Cesare PE. Use of antibiotic-impregnated cement in total joint arthroplasty. J Am Acad Orthop Surg 2003 11 38 7. 

Various additives in PE (Santonox, Nonox DPPD, Neozone A, Ionol and Agerite White) were determined by conventional TLC [507]. Other additives in PE, studied by means of TLC, were Tinuvin P 120/326/327/770, Cyasorb UV531, Anti UV P (2-hydroxy-4-n-octyloxybenzophenone), Irganox 1076, Sanduvor EPU, AO-4 and Dastib 242/263 [508], TLC has also been used in the analysis of additives in polyurethanes [509,510] as well as of slip additives (ethoxylated amines and amides) in HDPE extracts... 

RPLC-PDA is frequently used for quality control, such as the determination of free Irganox 1098 in PA4.6 (at 278 nm after dissolution/precipitation), of free Irganox 1010/1076 in PP (at 278 nm after extraction with MTBE, thus avoiding dissolution of polymer waxes), of Luperco 802 in PP (at 218 nm, after extraction with HCC13), and of Tinuvin 122 in HDPE (at 225 nm as diol). The advantages of the use of HSLC over conventional LC in QC of plastics and additives have been demonstrated, e.g. for AOs in PE, mixed phthalate esters and residual terephthalic acid in PET and partially cured epoxy resins [557],... 

LDPE or HDPE extracts has been determined colorimet-rically at 430 nm by oxidation with H202 in the presence of H2S04 [66]. p-Phenylenediamine derivatives such as Flexzone 3C, used as antiozonants in rubber products, have been determined colorimetrically after oxidation to the corresponding Wurster salts [67]. A wide range of amine AOs in polyolefins has been determined by the p-nitroaniline spectrophotometric procedure [68]. Monoethanolamine (MEA) in a slip agent in PE film has been determined as a salicylaldehyde derivative by spectrophotometric quantification at 385 nm [69]. Table 5.6 contains additional examples of the use of 1JV/VIS spectrophotometry for the determination of additives in polymers. 

Phenolic antioxidants in rubber extracts were determined indirectly photometrically after reaction with Fe(III) salts which form a red Fe(II)-dipyridyl compound. The method was applicable to Vulkanox BKF and Vulkanox KB [52]. Similarly, aromatic amines (Vulkanox PBN, 4020, DDA, 4010 NA) were determined photometrically after coupling with Echtrotsalz GG (4-nitrobenzdiazonium fluoroborate). For qualitative analysis of vulcanisation accelerators in extracts of rubbers and elastomers colour reactions with dithio-carbamates (for Vulkacit P, ZP, L, LDA, LDB, WL), thiuram derivatives (for Vulkacit I), zinc 2-mercaptobenzthiazol (for Vulkacit ZM, DM, F, AZ, CZ, MOZ, DZ) and hexamethylene tetramine (for Vulkacit H30), were mentioned as well as PC and TLC analyses (according to DIN 53622) followed by IR identification [52]. 8-Hydroquinoline extraction of interference ions and alizarin-La3+ complexation were utilised for the spectrophotometric determination of fluorine in silica used as an antistatic agent in PE [74], Also Polygard (trisnonylphenylphosphite) in styrene-butadienes has been determined by colorimetric methods [75,76], Most procedures are fairly dated for more detailed descriptions see references [25,42,44],... 

The results thus show that ammonia DCI-MS/MS using a triple quadrupole mass spectrometer is a convenient method for the detection of additives in PE samples. The softness and selectivity provided by ammonia DCI in combination with the specificity provided by CID, demonstrate great potential for identification of additives directly from PE extracts. The utility of DCI in the quantitative analysis of additives has still to be explored. DCI-MS/MS (B/E) with high collision... 

On-line SFE-SFC has also been used for the quantification of erucamide and antioxidants in PE [110]. Cotton et al. [15] have reported quantitative extraction of additives from PP at five different extraction pressures, at a constant flow-rate and temperature. Below 50 atm, extraction was negligible between 50 and 200 atm, Tin-uvin 326 and 770 were extracted, along with small quantities of oligomers. Higher pressures lead to the extraction of all the additives present, with the integrated peak areas conforming well to the actual concentrations. 

Applications Off-line SFE-HPLC appears to be applicable and quantitative for a variety of samples in many real -world matrices. The main challenge lies in the use of this technique for the more polar compounds. Quantitative off-line SFE-SFC-UV analysis of HDPE/Ethanox 330 was described after extensive method development (varying modifiers, modifier concentration, temperature) [129]. Soxhlet extraction and SFE-RPLC-UV of PE samples were compared [127]. A sample size (inhomogeneity) problem was pointed out when a SFE reproducibility study was performed on five 3-mg samples of PE. This points to limits... 

On-line SFE-pSFC-FTIR was used to identify extractable components (additives and monomers) from a variety of nylons [392]. SFE-SFC-FID with 100% C02 and methanol-modified scC02 were used to quantitate the amount of residual caprolactam in a PA6/PA6.6 copolymer. Similarly, the more permeable PS showed various additives (Irganox 1076, phosphite AO, stearic acid - ex Zn-stearate - and mineral oil as a melt flow controller) and low-MW linear and cyclic oligomers in relatively mild SCF extraction conditions [392]. Also, antioxidants in PE have been analysed by means of coupling of SFE-SFC with IR detection [121]. Yang [393] has described SFE-SFC-FTIR for the analysis of polar compounds deposited on polymeric matrices, whereas Ikushima et al. [394] monitored the extraction of higher fatty acid esters. Despite the expectations, SFE-SFC-FTIR hyphenation in on-line additive analysis of polymers has not found widespread industrial use. While applications of SFC-FTIR and SFC-MS to the analysis of additives in polymeric matrices are not abundant, these techniques find wide application in the analysis of food and natural product components [395]. 

Applications Basic methods for the determination of halogens in polymers are fusion with sodium carbonate (followed by determination of the sodium halide), oxygen flask combustion and XRF. Crompton [21] has reported fusion with sodium bicarbonate for the determination of traces of chlorine in PE (down to 5 ppm), fusion with sodium bisulfate for the analysis of titanium, iron and aluminium in low-pressure polyolefins (at 1 ppm level), and fusion with sodium peroxide for the complexometric determination using EDTA of traces of bromine in PS (down to 100ppm). Determination of halogens in plastics by ICP-MS can be achieved using a carbonate fusion procedure, but this will result in poor recoveries for a number of elements [88]. A sodium peroxide fusion-titration procedure is capable of determining total sulfur in polymers in amounts down to 500 ppm with an accuracy of 5% [89]. 

Haslam et al. [32] reported the determination of Al in polyolefins by AAS. Typical AAS tests on rubber compounds involve several steps. The sample is combusted, and the resulting ash is dissolved in distilled de-ionised water. The solution is then used for AAS [126]. AAS or EDS can also be used for element analysis of filler particles. In order to determine the uniformity of tin compounds in polychloroprene after milling and pressing, Hornsby et al. [127] have ashed various pieces from one composition. After fusion of the residue with sodium peroxide and dissolution in HC1, the Sn content was determined by means of AAS. Typical industrial AAS measurements concern the determination of Ca in Ca stearate, Zn in Zn stearate, Ca- and Zn stearate in PE, Ca and Ti in PE film or Al and V in rubbers. 

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