Polymer additive analysis by pyrolysis-gas chromatography. II. Flame retardants

Flame retardants are widely used in thermoplastic polymers for household and transportation applications. Flame retardants as well as most of the other additives in the polymer can be qualitatively analyzed by pyrolysis-gas chromatography (Py-GC) simultaneously with the polymer composition. The key to successful analysis of flame retardants not only requires a thorough knowledge of the various types of flame retardants but also necessitates an understanding of the parent polymer and its targeted applications. In this study, several flame retardants in different polymer matrices have been studied to demonstrate the utility of Py-GC for the analysis of flame retardants. The advantages of Py-GC for flame retardants analysis have also been discussed.     

Polymer additive analysis by pyrolysis-gas chromatography. I. Plasticizers

Plasticizers are widely used in thermoplastic polymers to modify their physical properties and processibility. Plasticizers as well as most of the other additives in the polymer can be qualitatively analyzed by pyrolysis-gas chromatography (Py-GC) simultaneously with the polymer composition. The key to the successful analysis of plasticizers not only requires a comprehensive understanding of commercial plasticizers but also requires knowledge of the polymer and its applications, as well as the Py-GC technique. In this study, several plasticizers in different polymeric systems were studied to demonstrate the utility of Py-GC as a good tool for the characterization of these systems. The advantages of using Py-GC for plasticizer analysis are also discussed.     

Polymer additive analysis by pyrolysis-gas chromatography. IV. Antioxidants

Antioxidants are important additives in polymers. Because of the low level of antioxidants normally used, they cannot be analyzed directly by common spectroscopic or thermal chemical techniques. However, antioxidants as well as other additives in polymers can be qualitatively analyzed by pyrolysis-gas chromatography (Py-GC) after separating the polymers and additives. In this study, several antioxidants have been investigated to demonstrate that Py-GC is a viable tool to analyze them. The advantages of using Py-GC in the analysis of antioxidants have also been discussed.     

Analysis of red phosphorus in resins using pyrolysis-gas chromatography/mass spectrometry.

Although red phosphorus is used as a flame retardant for polymer materials, no analysis methods for it in resins has been established. Analysis methods for red phosphorus in resins were investigated using pyrolysis-gas chromatograpy/mass spectrometry (Py-GC/MS) by paying attention to the fact that it has a sublimation property. We found that the mass spectrum of red phosphorus shows a series of ions at m/z=62, 93 and 124, and a fragment pattern indicating that red phosphorus (P4=124, P=31) was pyrolytically decomposed. The coefficient of the correlation between the content of red phosphorus in the resin and the peak intensity in Py-GC/MS was 0.9781. The relative standard deviations of this analysis method was 6.29% (n=5). Py-GC/MS was applicable not only to qualitative analysis but also to the quantitative analysis of red phosphorus.     

Qualitative and quantitative analysis of a thermoset polymer, poly(benzoxazine), by pyrolysis-gas chromatography

The chemical composition of a poly(benzoxazine) thermoset polymer (a copolymer of bisphenol-A benzoxazine and tert.-butylphenol benzoxazine) has been studied by pyrolysis-gas chromatography (Py-GC). Major pyrolysates have been identified and the possible degradation pathways have been investigated. A specific pyrolysate was identified for quantitative analysis after carefully proving the linear relationship between the pyrolysate signal intensity and monomer concentration over a wide range of compositions. A method to determine the concentration of the monomer that potentially acts as a cross-linking unit has been developed. In this study, Py-GC was shown to be an excellent analytical technique for the qualitative and quantitative analysis of thermoset polymers.     

Recent trends and developments in pyrolysis-gas chromatography

Pyrolysis-gas chromatography (Py-GC) has become well established as a simple, quick and reliable analytical technique for a range of applications including the analysis of polymeric materials. Recent developments in Py-GC technology and instrumentation include laser pyrolysis and non-discriminating pyrolysis. Progress has also been made in the detection of low-level polymer additives with the use of novel Py-GC devices. Furthermore, it has been predicted that future advances in separation technology such as the use of comprehensive two-dimensional gas chromatography will further enhance the analytical scope of Py-GC.     

Liquid Chromatographic Separation of Olefin Oligomers and its Relation to Separation of Polyolefins – an Overview

Summary: Linear and branched alkanes are oligomers of polyethylene. Alkanes with higher molar masses are called waxes. These substances are widely used as fuels, oils, lubricants, etc. and for these reasons many groups have tried to analyse, separate and characterise alkanes by various methods, including liquid chromatography. Alkanes may be separated according to their size in solution by SEC. In addition to chromatographic systems separating in the SEC mode, various sorbent-solvent systems have been published, where alkanes have been separated one from another by adsorption and/or precipitation mechanism. The mobile phase is either a non-polar solvent or a polar solvent or a mixture of a solvent and a non-solvent for alkanes. Even near critical conditions, which have several advantages for applications of HPLC in polymer analysis, have been identified for alkanes. Moreover, selective separations of branched alkanes according to their structure have been published. In the majority of these published studies, solvents with low boiling points have been used as the mobile phases, which do not allow dissolution of crystalline polyolefins at atmospheric pressure. However, taking into account experiences with the separation of alkanes, new HPLC systems for the separation of polyolefins may be developed. This is a major challenge and first results are presented in this contribution.     

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.     

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.     

同时裂解甲基化气相色谱法鉴别合成胶粘剂

 应用同时裂解甲基化气相色谱法 (Py Me GC)对合成胶粘剂进行了鉴别。采用热丝型裂解器、氢火焰离子化气相色谱仪、FFAP毛细管柱、程序升温方式及季铵盐甲基化试剂 ,对刑事案件中常见的丙烯酸酯类及其改性体、醋酸乙烯酯、聚乙烯醇等合成胶粘剂进行了测定 ,并对样品裂解各主要组分峰进行了GC/MS定性分析 ,同时比较了相同样本用常规裂解气相色谱法 (Py GC)测定的结果。结果表明 :Py Me GC法比Py GC法可获得更多的物质组分信息 ,是一种适用于法庭科学鉴定的方法。     

Determining the density profile of confined polymer brushes with neutron reflectivity

Polymer molecules at solid or fluid interfaces have an enormous spectrum of applications in a wide variety of technologies as lubricants, adhesion modifiers, and protective surface coatings. Because polymer brushes have great potential to be used in such applications, there is a need to determine their structure and efficiency in reduced spaces. Using neutron reflectivity, we have directly quantified the density distribution of opposing polymer brushes under confinement in good solvent conditions under confinement. Our measurements show that the density profile in the overlap region between opposing polymer brushes flattens, consistent with predictions from molecular-dynamics simulations. In addition, a significant increase in the density at the anchoring surfaces due to the collapse of the brush layers was observed. This collapse of the brushes in restricted geometries suggests that high-density brushes do not interpenetrate significantly under good solvent conditions. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 3290–3301, 2004     

Application of a pyrolysis-GC/MS system incorporating with micro-UV irradiation to rapid evaluation of the weatherability of acrylic coating paints for house exterior walls

A pyrolysis-GC/MS system incorporating with micro-UV irradiator (Xe-Hg lamp) was applied to the evaluation of the weatherability of the acrylic coating paints for house exterior walls. The deterioration of the materials during UV irradiation under thermal, and oxidative atmosphere was evaluated within a relatively short period of time with evolved gas analysis-mass spectrometry (EGA-MS) using a sub-milligram polymer sample. The EGA-MS thermograms indicated that both micro-UV irradiator with Xe-Hg lamp and weather meter with metal halide lamp caused similar photo, thermal, and oxidative degradation to the coating paint samples. Strong correlations between the results obtained by the UV/Py-GC/MS and that obtained by conventional weathering test using metal halide lamp was observed. It was suggested that UV/Py-GC/MS method could be used for compensating the conventional method by reducing the test period.     

Determination of polymer additives using analytical pyrolysis

When analyzing a polymeric material using pyrolysis-GC, the majority of the peaks seen are degradation products from the polymer matrix, but there may be specific compounds present resulting from the presence of antioxidants, plasticisers, stabilizers, flame retardants and other additives. Some of these compounds may be volatile or semi-volatile and appear as intact molecules, while others are larger and only appear as fragments after the pyrolysis. In understanding the pyrolysis of the complete system, it is important to understand the behavior of such additives under the thermal conditions used to analyze the polymer matrix.This paper presents data for several polymer additives, showing their contribution to the analytical results when studying typical polymers using Py-GC/MS. Specific types of additives include phenolic antioxidants, hindered amine light stabilizers, phthalates and phosphites.It was determined that for some additives, especially when analyzing simple polymers, co-analysis of the polymer and additive was feasible. For other, more complex formulas, a multi-step approach permitted a thermal separation of compound families and simplified the analysis. For some additives, especially in the parts-per-million range, pyrolysis with selected or extracted ion mass spectrometry was the most informative.     

Characterization of substituted polyacetylene microstructure by pyrolysis gas chromatography

A series of substituted acetylenes has been polymerized with WOC14/Ph4Sn metathesis catalyst and [Rh(cod)OMe]2 insertion catalyst, and the thermal degradation of the polyacetylenes prepared has been studied using pyrolysis capillary gas chromatography (Py-GC) with flame ionization and mass spectrometric detection to obtain information on the effect of the catalyst on the head-tail (H-T) isomerism of polyacetylenes (poly(phenylacetylene), poly[(4-methylphenyl)acetylene], poly(benzylacetylene), poly((2-fluorophenyl)acetylene], poly[(3-fluorophenyl)acetylene], and poly[(4-fluoro-phenyl)acetylenel). Cyclotrimers have been found to be the main pyrolysis products in all cases. Direct Py-MS connection was used to determine the temperature profiles of the released pyrolysis products. 1,3,5-Trisubstituted benzenes were found to be the predominant pyrolysis products of the polymers prepared with the insertion catalyst, which proves the presence of long head-to-tail sequences of monomeric units in these polyacetylenes. On the other hand, both 1,2,4- and 1,3,5-trisubstituted benzenes are present in significant amounts in the pyrolysis products of polymers prepared with the metathesis catalyst, which proves the presence of a significant content of the head-to-head (HH) and tail-to-tail (TT) linkages in these isomers of polyacetylenes. Contents of the regular (HT) and inverse (HH-TT) monomer linkages (RML and IML, respectively) in polymer chains were determined from the relative amounts of di-, tri-, and tetrasubstituted benzenes found in the Py-GC products.     

A rheological model based on primary laboratory data of lubricants with polymers additives

The present work reports some experimental data consisting in traction behavior for lubricants with polymer additives. The rheological response of lubricants without polymer additives and with additives as a function of polymer concentration, pressure and temperature is discussed. Based on the laboratory data, the paper presents a quasi-empirical approach which predicts elastic shear modulus, limiting shear stress and characteristic shear stress of a lubricant with polymer additives.     

Characterization and identification of acrylic binding media: influence of UV light on the ageing process

This study characterizes and identifies two different acrylic binding media such as Plextol® D498 and Primal® AC33, which are widely used in modern and contemporary art. In order to investigate their fast photooxidative deterioration when exposed to ultraviolet (UV) light, ageing studies on these materials were carried out. For this purpose, pure synthetic materials but also mixed with different inorganic pigments were identified and characterized before and after UV exposure by means of pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS). Particular attention was paid to the comparison of two different analytical methods: (1) single-shot method based on a pyrolysis for the analysis of polymers and (2) double-shot method, which allows a unique combination of thermal desorption for the analysis of volatile compounds and pyrolysis of the polymers themselves. These analyses have been complemented by Fourier transform infrared spectroscopy-attenuated total reflectance (FTIR-ATR) studies. The comparison of the results obtained from unaged samples and UV-aged clearly showed material alterations as well as the formation of new products, which were recorded by FTIR-ATR. Generally, these changes were more pronounced when the acrylic binding media were mixed with pigments. The double-shot technique of Py-GC/MS additionally allowed the detection of the phenolic antioxidant in unaged Plextol® D498, but no oxidation products could be identified by Py-GC/MS in all samples.     

A degradation study of waterborne polyurethane based on TDI

The thermal degradation of synthetic waterborne polyurethane (PU) based on toluenediisocyanate (TDI) was investigated by pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) and thermogravimetry (TG). The degradation profiles of cast films obtained from dispersions were evaluated. More than 20 characteristic volatile pyrolyzates reflecting the structure and pyrolysis mechanisms of the polymer have been identified by on-line MS. The synthesized products of polyurethane were pyrolyzed at 350, 450, 550, 650 and 750 °C respectively, and the analysis results revealed that the pyrolyzates distribution of the polyurethane depends strongly on the pyrolysis temperature. The aqueous polyurethane thermogravimetric measurements were used to study the kinetics of thermal degradation.     

The effect of processing additives on the surface properties of polyvinyl chloride

Stabilizers, plasticizers and lubricants play an important part in the formulation of polymer materials for use in manufacturing. For polyvinyl chloride, they are used to achieve stability, together with suitable flow and release behavior, during extrusion, molding, and other processing steps. However, the additives remain after manufacturing and may affect the properties of the product for the rest of its useful life. We have investigated the surface properties of polyvinyl chloride containing organotin stabilizers and calcium stearate, and the surface properties of the additives themselves. We used zeta-potential measurements to determine the charge on the surface of additive-containing polyvinyl chloride and have related this to chemical reactions of the additive materials. This chemistry is important for understanding what goes on during the period when the polymer product comes in contact with a humid environment. The major chemical reactions are those involving hydrolysis of tin-ester linkages in the organotin compounds and dissociation of carboxylic acid groups. These groups may be the carboxylic acid groups originally present or those formed by hydrolysis. As a result of these reactions, the surface charge of the polymer depends strongly on the pH of the aqueous medium in contact with the surface.     

Modelling relation between oxidation resistance and tribological properties of non-toxic lubricants with the use of artificial neural networks

The lubricants based on vegetable oils, as environmental friendly, are urgently sought. However, in addition to ecological characteristics, the lubricating properties have to be met. To meet these requirements the active additives influencing the lubricating properties and oxidation resistance are used. The useful lifetime of lubricants is determined largely by their abilities to resist oxidation. The article presented the results of new, ecological lubricants development. The oxidation performances of different developed lubricants have been tested. The experimentally determined oxidation stability of the compositions based on vegetable oils are presented. Analysed oxidation onset temperature was obtained from the differential scanning calorimetry (DSC) curves, which provides the rapid prediction of the oxidative stability of lubricants. Besides the lubricating composition based on vegetable oils, the developed greases-based mineral, or synthetic oil were investigated. The properties of these greases were evaluated using the measurement of parameters describing structure (penetration) and resistance to high temperature (dropping point). The lubricating properties of both the greases and vegetable oil compositions were tested on four-ball testing machine. In the results of the modelling of the lubricating properties the neural network models for the both types of the lubricants were developed. A discussion of the research results and analysis of models validity is given below. The experimental results are compared with the calculated using the neural models. An acceptable agreement was achieved.     

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.