Differentiation of resin-modified paints by pyrolysis-gas chromatography/mass spectrometry and principal component analysis

The combination of pyrolysis (Py) with gas chromatography/mass spectrometry (GC/MS) is already well established for polymer analysis. A first approach is reported using this method for detailed quality monitoring of a complex technical polymer system. Six similar solvent-based paints (one standard and five modifications) have been used for evaluation. The major pyrolysis products were identified and qualitative and quantitative modifications were detected and specified. Principal component analysis (PCA) was applied for visualization of differences and similarities.     

Differentiation of resin-modified paints by pyrolysis-gas chromatography/mass spectrometry and principal component analysis

The combination of pyrolysis (Py) with gas chromatography/mass spectrometry (GC/MS) is already well established for polymer analysis. A first approach is reported using this method for detailed quality monitoring of a complex technical polymer system. Six similar solvent-based paints (one standard and five modifications) have been used for evaluation. The major pyrolysis products were identified and qualitative and quantitative modifications were detected and specified. Principal component analysis (PCA) was applied for visualization of differences and similarities.     

Characterization of some acrylic anion-exchangers by pyrolysis-gas chromatography

Pyrolysis-gas chromatography was used in the study of the thermal behaviour of some acrylic anion-exchangers for identification of the thermal decomposition products and their percentage estimation. The acrylic anion-exchangers were prepared by aminolysis of cross-linked acrylic ester copolymer with difunctional amines. The pyrolysis-gas chromatography studies, coupled with data obtained by thermogravimetry, showed that the acrylic anion-exchangers first lose the water easily absorbed from the air, and the decomposition starts at temperatures above 100°. The great number of decomposition products identified in the pyrograms on the thermal degradation of acrylic anion-exchangers indicated a complex degradation mechanism, with important variations in the contents of the evolved amine compounds.     

Structural characterization of polymers by pyrolysis-gas chromatography

Pyrolysis gas chromatography can yield structural information about a particular polymer which is both detailed and characteristic. Those examined include polyethylenes, polypropylenes and ethylene-propylene co-polymers.     

UV ageing studies: evaluation of lightfastness declarations of commercial acrylic paints

The lightfastness declarations of several different commercial acrylic paints and different quality series were tested by artificial UV ageing. To evaluate their lightfastness declarations, three acrylic colours (cadmium red, ultramarine blue and chromium oxide green) from six companies (Lascaux, Liquitex, Lukas, Rembrandt, Schmincke, and Winsor & Newton) were analysed before and after UV exposure. Characterisation and identification of these materials were carried out with Py–GC/MS, FTIR–ATR analyses, and colour measurements. Particular attention was focused on the Py–GC/MS measurements and on comparison of the single-shot method for pyrolysis of polymers and the double-shot mode which enables a unique combination of pyrolysis methods for analysis of polymers and thermal desorption for documentation of the volatile compounds. Depending on the particular company and the specific value of the lightfastness declaration, different binding media (i.e. poly(EA/MMA), poly(nBA/MMA), and poly(2-EHA/MMA)), and fillers (i.e. kaolinite, calcium carbonate, barite, and talc) were characterised and identified by Py–GC/MS and FTIR–ATR analyses. After UV exposure, several alteration processes with consequent formation of volatile compounds or new products were observed by both techniques, especially for the blue paints. In particular, the double-shot mode of Py–GC/MS enabled the detection of oxidation products, which could not be detected with the single-shot mode. Comparison of the lightfastness declarations for each of the blue, green, and red paints and the noted alterations broadly agreed for most of the paints.     

Determining the composition and microstructure of ethylene-propylene copolymers by pyrolysis-gas chromatography

The average composition and detailed microstructure of copolymers of ethylene and propylene have been studied by pyrolysis-gas chromatography (Py-GC), using a statistical modeling approach to analyze the data. The trimer distribution obtained from Py-GC is used to infer monomer arrangement information, which is quantified in terms of a number-average sequence length for each monomer. These values are used to define the microstructure and to calculate the average composition. Compared with other available techniques, Py-GC provides a simple, quick and reliable approach to study the microstructure and composition of polyolefin copolymers. Details of this Py-GC method are discussed, including an examination of its advantages and disadvantages, and a summary of the qualitative and quantitative analysis aspects of this approach is presented. The combination of a statistical modeling approach with Py-GC to study copolymer composition and microstructure allows one to investigate the complex problem of monomer arrangement in copolymers using a widely available analytical technique. We expect that with further advances in separation technology, especially two-dimensional gas chromatography (GC x GC), research of this type will be become increasingly accurate and reproducible in the near future.     

Determination of the amine content of chitosan by pyrolysis-gas chromatography

Pyrolysis-gas chromatography-mass spectrometry has been applied to the study of N-acetyl-d-glucosamine, chitin and chitosans of varying degrees of deacetylation prepared from chitin. An examination of the pyrograms of samples of chitosan revealed that there is a direct correlation between the amine content and the ratio of the areas of the peaks derived from the glucosamine and N-acety-d-glucosamine moieties.     

Blends of styrene/acrylic acid copolymers and acrylic polymers

The miscibility of a series of styrene/acrylic acid copolymers with various polyacrylate and polymethacrylate homopolymers, as well as a series of styrene/methyl methacrylate copolymers, has been investigated. According to the binary interaction model, the miscibility diagram for styrene/acrylic acid copolymers with styrene/methyl methacrylate copolymers indicates that acid and ester groups interact endothermically. The phase behavior of the homopolymers also implies this. The analysis ignores the association and self-association observed for the polymer blends and the low-molecular-weight analogs used to model them. The heat of mixing of low-molecular-weight analogs depended greatly on both composition and acid structure.     

Number-average molecular mass determination of polymeric material by pyrolysis-gas chromatography

The number-average molecular mass of a polymeric material has been determined by pyrolysis-gas chromatography (Py-GC) via end-group analysis. The major advantage of this technique is that no sample preparation is required. The sample is not required to be in the dilute solution form, and the amount of sample needed is approximately 0.5 mg. Phenyl group-terminated polybutadiene systems have been studied as an example. The application of Py-GC to obtain the end-group concentration, the number-average molecular mass and the limitations of this method are discussed in detail. The success of this development elevates the role of Py-GC as an important technique for end-group analysis for the determination of number-average molecular mass.     

Developments in the determination of organic oxygen by pyrolysis-gas chromatography

Summary The use of 40% nickel-coated carbon is described in a method for direct determination of organic oxygen, based on instantaneous pyrolysis of the sample in a long quartz capsule, followed by gaschromatographic separation and thermal-conductivity measurement of the CO produced. A short layer of nickelised carbon is used, placed separately from the pyrolysis zone in order to avoid physical and chemical interferences. Carbon coated with 40% of nickel remains active for approximately 20 days when used in a carbon/ carbon dioxide reaction system.

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Zusammenfassung Die Verwendung von 40% Nickel enthaltender Kohle zur direkten Bestimmung von organisch gebundenem Sauerstoff wurde beschrieben. Sie beruht auf der Momentpyrolyse der Probe in einer langen Quarzkapsel und nachfolgender gaschromatographischer Trennung und Messung des entstandenen Kohlenmonoxids durch Wärmeleitfähigkeitsbestimmung. Eine kurze Schicht mit Nickel versehener Kohle wird abseits von der Pyrolysezone verwendet, um physikalische oder chemische Störungen zu vermeiden. Mit 40% Nickel versetzte Kohle bleibt etwa 20 Tage aktiv, wenn sie in einem Kohle/Kohlendioxid-System verwendet wird.

     

Studies on thermal degradation of epoxy resins by high-resolution pyrolysis-gas chromatography

The optimum pyrolytic conditions for thermosetting epoxy resin samples were first empirically studied. On the basis of the optimized pyrolytic conditions, epoxy prepolymers and epoxy resin samples cured with and without curing agents, such as diamine and dicarboxylic acid anhydride, were studied using high-resolution pyrolysis-gas chromatography. In addition to some intact prepolymer molecules, various degradation products characteristic of the prepolymers, up to diglycidyl ether of bisphenol A, were detected on the pyrograms of the prepolymers. On the other hand, various phenols characteristic of the prepolymers and a variety of pyrolyzates characteristic of the reacted curing agents, including intact dicarboxylic acid anhydride, were observed on the programs of the cured resin samples. The potential of this technique for studying the curing process of the epoxy resins is discussed.     

Rapid and sensitive determination of the conversion of UV-cured acrylic ester resins by pyrolysis-gas chromatography in the presence of an organic alkali.

The double-bond conversion of UV-cured resins prepared from pentaerythritol triacrylate (PETA) was determined by pyrolysis-gas chromatography in the presence of an organic alkali, tetramethylammonium hydroxide (TMAH). The pyrogram of the uncured prepolymer compound, consisting of PETA and a photoinitiator, 2,2-dimethoxy-2-phenylacetophenone, contained specific products reflecting the original acrylate structure, such as methyl acrylate (MA) and methyl ethers of pentaerithritol. Meanwhile, in pyrograms of the UV-cured PETA, the yields of MA considerably decreased. The double-bond conversions of the cured resins, irradiated with various UV dosages, were calculated based on the relative yields of MA among specific products in the pyrograms. The conversions determined by this approach were analyzed by comparing them with those estimated by Fourier-transform infrared spectroscopy.     

Characterization of sulphur-cured rubbers by high-resolution pyrolysis-gas chromatography with flame photometric detection

Polybutadiene rubber, natural rubber and acrylonitrile-butadiene rubber cured with sulphur and accelerators were characterized by high-resolution pyrolysis-gas chromatography with a sulphur-selective flame photometric detector. With the three polymer systems, various sulphur-containing products characteristic of the base polymers and vulcanization accelerators were observed. The vulcanization process for polybutadiene rubber is discussed on the basis of the relationships between the peak intensities of the characteristic products and cure time.     

Natural and artificial weathering characteristics of stabilized acrylic–urethane paints

Depth-profiling by Fourier transform infrared (FTIR) spectroscopy, dynamic mechanical analysis (DMA), microhardness and scanning electron microscopy (SEM) observations have been used to monitor degradation chemistries in two-package acrylic–urethane coatings when exposed to different exposure conditions. Three artificial and three natural weathering protocols (QUV, ASTM D5894, ISO20340, Pipady (south of France), Bandol (south of France) and Kure Beach (USA)) were selected for this study. The same chemical events were found to occur under all conditions, particularly under natural and artificial exposures. Both loss of the amide II band at 1520 cm⁻¹ and carbonyl growth occurred but at relatively low rate owing to the presence of hindered-amine light stabilizers in the film. A less typical loss of urea biuret linkages also occurs during all exposures and results in a change in the balance between urethane and urea links across the depth of the film during weathering. The chemical degradation of the polymer matrix involves the formation of species that are readily ablated from the surface and results in loss of gloss, increase in hardness and a rougher topology. The dramatic loss of gloss observed after Pipady and Bandol exposures show that loss of gloss should not be systematically correlated to the advance in chemical degradation.     

Evaluation of acidic paper deterioration in library materials by pyrolysis-gas chromatography

Pyrolysis-gas chromatography (Py-GC) has been applied to the evaluation of the deteriorated acidic paper in old books. A tiny piece (ca. 0.25 mg) of deteriorated paper was subjected to Py-GC measurement at 300 °C pyrolysis temperature. Levoglucosan and its dehydrated form levoglucosenone were typical degradation products while a recent control paper gave rise mainly to levoglucosan. The relative yield of levoglucosenone was much higher for the paper sample taken at the heavily deteriorated marginal part than that in the center of the same page of the old book. Accordingly, levoglucosenone observed in the pyrogram can be used as a marker to evaluate the degree of the deterioration of the acidic paper. The formation of levoglucosenone can be attributed to the slow deterioration process of paper, in which dehydration reaction play an important roll accompanied by the chain scission of cellulose. The Py-GC method for paper evaluation was also applied to clarify the effect of storage conditions and chemical compositions of paper materials to their deterioration processes.     

Determination of the antioxidant alurofen in synthetic rubbers by pyrolysis-gas chromatography

A pyrolysis—gas chromatographic (Py—GC) method for the determination of the antioxidant Alurofen in synthetic rubbers was developed. The Alurofen was extracted from the rubber, then pyrolysed as 873 K in continuous-mode furnace pyrolyser in 20 s. Chromatographic conditions for the separation of the pyrolysis products were established. The pyrolysis of the Alurofen at several temperatures was investigated by measuring the yields of the pyrolysis products. It was observed that 2-phenyl-2-(4-hydroxyphenyl)propane was produced in the greatest, amounts, and the effect of the pyrolysis temperature on the yield of this compound was studied. The overall Py—GC method for the determination of the Alurofen content of rubbers had a mean relative error of 2.7% and a relative standard deviation of 2.94%.     

Study of chloroquine binding to melanins by pyrolysis-gas chromatography and electron spin resonance spectroscopy

Structural differences in melanins were studied by Curie-point pyrolysis-gas chromatography-mass spectrometry, electron spin resonance spectroscopy and chloroquine binding. Pyrolysis-gas chromatographic data on the polymer allow the calculation of a UU index that expresses the relative amount of unindolized DOPA-derived units in the melanins.It is shown that the content of unindolized units in the polymer depends strongly on the oxidation time and DOPA concentration used during the melanin synthesis. Comparison of the chloroquine binding to melanins and the pyrolysis data showed that there is an inverse relationship between the affinity of chloroquine and the UU index.     

Catalytic effect of smectite clays in hydrocarbon generation revealed by pyrolysis-gas chromatography

Temperature-programmed pyrolysis-gas chromatography of mixtures of expanding three-layer clays and Eocene Green River Formation kerogen gives insight into the differences in composition of pyrolyzates of specific sediments and of isolated kerogens. Argillaceous sediments containing less than about 2τ total organic carbon yield pyrolyzates containing primarily low molecular weight hydrocarbons in the gas condensate range whereas kerogens isolate from such sediments yield a broad range of volatile products including higher molecular weight hydrocarbons. Pyrolyzates of organic-rich sediments are much more similar in composition to pyrolyzates of isolate kerogens. The ration of expanding three-layer clays to organic matter in sediments apparently controls the degree of catalytic cracking so that argillaceous sediments relatively low in organic matter yield volatiles rich in low molecular weight hydrocarbons due to more carbon—carbon bond cleavage. These observations are related to gas and gas condensates of the northern Gulf Mexico basin and in Indonesia and to oil in the North Sea area.     

松香丙烯酸基二元单体与苯乙烯的共聚反应

以丙烯酸松香加成物(RA)与甲基丙烯酸-2-羟乙酯的酯化物(RAH)为二元单体,采用溶液聚合法制备了苯乙烯与RAH的共聚物.通过正交实验法研究了反应条件对RAH与苯乙烯共聚反应的影响.对正交实验的结果分析得出:在反应温度为105℃下,RAH与苯乙烯的质量比为1:2,引发剂的用量为单体质量的1.5%,反应时间为8小时,单体转化率最高,为85%;原料配比对共聚反应的影响最为显著,其次是反应温度和引发剂用量,反应时间的影响最小.通过红外光谱分析和核磁共振图谱分析表明成功合成了RAH与苯乙烯的共聚物,热重分析表明产物的热稳定性随单体中RAH比例的增加而增加.