Determination of multipolymer structure using pyrolysis gas chromatography

The thermal degradation of poly(styrene-butadiene-methylmethacrylate-butylacrylate)multipolymers has been investigated by Curie Point pyrolysis gas chromatography (PGC). Small multipolymer samples were pyrolysed in a stream of helium at 600° in a Curie Point pyrolyser directly connected to the gas chromatograph. The pyrolysis products were identified by mass spectrometry. The interpretation of each cluster of dimer and trimer peaks appearing on the chromatogram was carried out by using a statistical method (factor analysis) from which the molecular structure of the multipolymers was inferred.     

Pyrolysis—gas chromatography of networks

Cis-1,4-polybutadiene was exposed to different doses of β-radiation (5–100 Mrad), and polybutadiene samples with different contents of 1,2- and 1,4-isomers were exposed to equal doses of radiation (50 Mrad). The cross-linked products were characterized by sol—gel analysis, distribution of the molar masses of the sol fraction, determination of the degree of swelling and compressibility, and pyrolysed by means of a Curie-point pyrolyser at 770°C in 4 s. Evaluation of the pyrograms taken with the help of a capillary gas chromatograph proved that pyrolysis—gas chromatography enables statements regarding the micro-structure of these cross-linked polymers to be made through the degradation products 1-cis-2- and 1-trans-2-dimethylcyclopropane, 2-methyl-1,3-butadiene and trans-1,3-pentadiene in a very short time without much preparation of the samples. The peak areas of 1,3-butadiene and 4-vinylcyclohexane can be used to characterize the network density.     

Aromatic polyamides. II. Thermal degradation of some aromatic polyamides and their model diamides

Thermal degradation behavior of poly(1,3-phenylene isophthalamide) and poly(chloro-2,4-phenylene isophthalamide) was investigated with the aid of some appropriate model compounds. The pyrolysis products of these materials were identified by gas chromatography (GC), gas chromatography/Fourier transform infrared spectroscopy (GC/FT-IR), and gas chromatography/mass spectrometry (GC/MS). The residual chars were characterized by IR spectroscopy. Thermogravimetric analysis (TGA) was applied to study the effect of end-group concentration on the degradation characteristics of the two polyamides. Kinetic parameters that describe the thermal degradation of the polyamides were also evaluated by TGA. The results of this investigation suggest that the thermal decomposition of these aromatic polyamides involves homolytic as well as hydrolytic cleavages of the amide units.     

Polyamides having long methylene chain units

Three series of polyamides having long methylene chain units have been prepared from p-xylylenebisethylamine and 2,2′-pphenylenebisethylamine with aliphatic dicarboxylic acids of long methylene chain units; aliphatic diamines of long methylene chain units with terephthalic, p-benzenediacetic, and p-benzenedipropionic acids; and aliphatic diamines with aliphatic dicarboxylic acids, both having long methylene chain units. The effects of the length of the methylene chain units on the melting point, the glass transition temperatures and the densities of these polyamides were investigated. The aromatic polyamides, in which even methylene chains are joined between a phenylene and an amide group generally have higher melting points than the corresponding ones with odd methylene chains. On the plots of the melting points and the densities of the aliphatic series against the amide concentrations, both the melting point and the density extrapolated to the zero amide concentration are found below the values for polymethylene.     

Novel ferrocene modified poly(amide ether amide)s and investigation of physical and thermal properties

A new diamine containing ferrocene group with preformed ether and amide units was prepared via reaction of 1,1′-ferrocenedicarbonyl chloride with two moles of 2,6-bis(5-amino-1-naphthoxy)pyridine. Polycondensation reactions of the prepared diamine with different aromatic and aliphatic diacid chlorides in the presence of trimethylchlorosilane (TMSCl) resulted in preparation of novel ferrocene modified poly(amide ether amide)s. The monomer and polyamides were characterized and the effect of trimethylchlorosilane (TMSCl) as activating agent on the polymerization reaction was studied. The physical and thermal properties of the polyamides including inherent viscosity, solubility, thermal stability and behavior, flame-retardancy and crystallinity of the polymers were studied. The polymers showed good thermal stability and flame-retardancy, and also improved solubility in polar aprotic solvents.     

裂解色谱法甲基化试剂碱性对多不饱和脂肪酸降解和异构化的影响

采用最佳比例裂解甲基化试剂,消除了强碱性甲基化试剂对油脂中多不饱和脂肪酸降解和异构化作用的影响。考察了不同比例甲基化试剂的碱性对多不饱和脂肪酸降解和异构化的程度。     

High-temperature pyrolysis of poly(vinyl chloride): Gas chromatographic-mass spectrometric analysis of the pyrolysis products from PVC resin and plastisols

A pyrolysis–gas chromatographic–mass spectrometric technique for analyzing the pyrolysis products from polymers in an inert atmosphere is described. Initial studies encompassing the pyrolysis of poly(vinyl chloride) homopolymer and a series of PVC plastisols (based on o-phthalate esters) have provided a complete qualitative and semi-quantitative analysis of the pyrolysis products from these materials. PVC resin yields a series of aliphatic and aromatic hydrocarbons when pyrolyzed at 600°C; the amount of aromatic products is greater than the amount of aliphatic products. Benzene is the major organic degradation product. A typical PVC plastisol [PVC/o-dioctyl phthalate (100/60)] yields, upon pyrolysis, products that are characteristic of both the PVC matrix and the phthalate plasticizer. The pyrolysis products from the plasticizer dilute those from the PVC portion of the plastisol and are, in turn, the major degradation products. There are no degradation products resulting from an interaction of the PVC with the plastisol. The pyrograms resulting from pyrolysis of the various plastisols of PVC can be used for purposes of “fingerprinting.” Identification of the major peaks in a typical plastisol pyrogram provides information leading to a precise identification of the plasticizer. The pyrolysis data from this study were related to a special case of flammability and toxicity.     

Structural characterization of polyolefins by pyrolysis—hydrogenation glass capillary gas chromatography

In order to obtain quantitatively specific and high-resolution pyrograms of high polymers, fundamental splitting conditions for pyrolysis—gas chromatography were studied using a vertical micro-furnace type of pyrolyzer attached to a glass capiliary separation column. High-resolution pyrograms were measured for polyolefins such as polyethylenes (PE), polypropylenes (PP) and various kinds of ethylen—propylene copolymers [P(E-co-P)] using a pyrolysis—hydrogenation device. Microstructures such as short branchings for PE, stereoregularities and chemical inversions for PP and sequence distributions for P(E-co-P) are discussed on the basis of the pyrograms.     

裂解气相色谱—裂解毛细柱气相色谱联用仪

设计了一种裂解气相色谱--裂解毛细柱气相色谱联用仪。在第一级裂解气相色谱仪把聚合物裂解并分离裂解产物,分离了的产物用六通气体进样阀选取并逐个在第二级裂解气相色谱仪裂解,得到聚合物裂解产物的裂解气相色谱图。与低分子化合物的标准指纹图比较,这些裂解产物就得到确认,这样,就可以充分肯定地推断复杂聚合物的组成。     

Thermal properties and solubility of ordered aromatic polyamides containing a methyl-substituted phenylene linkage

Ordered aromatic polyamides and copolyamides were prepared by the polycondensation of terephthaloyl and isophthaloyl dichlorides with symmetrical diamines containing preformed amide linkages derived from unsymmetrical methyl—substituted aromatic diamines at low temperature. Thermal properties and solubilities of the ordered polyamides were compared with those of the corresponding random polyamides. There was little difference between thermal stabilities of the ordered polyamide and the corresponding random one, while the former was less soluble in organic solvents than the latter, depending on the extent of hydrogen bonding of the amide groups. The thermal stability of the alternating copolyamides containing both terephthaloyl and isophthaloyl groups as acid components was less than that of the corresponding homopolymers having either a terephthaloyl or an isophthaloyl group, and the solubility of the former resembled that of the corresponding ordered homopolysiophthalamides in accord with the extent of hydrogen bonding of the amide groups in both polymers.     

Characterization of complex hydrocarbons in cigarette smoke condensate by gas chromatography-mass spectrometry and comprehensive two-dimensional gas chromatography-time-of-flight mass spectrometry

Gas chromatography-mass spectrometry with electron ionization and positive-ion chemical ionization and comprehensive two-dimensional gas chromatography-time-of-flight mass spectrometry (GC x GC-TOF-MS) were applied for the characterization of the chemical composition of complex hydrocarbons in the non-polar neutral fraction of cigarette smoke condensates. Automated data processing by TOF-MS software combined with structured chromatograms and manual review of library hits were used to assign the components from GC x GC-TOF-MS analysis. The distributions of aliphatic hydrocarbons and aromatics were also investigated. Over 100 isoprenoid hydrocarbons were detected, including carotene degradation products, phytadiene isomers and carbocyclic diterpenoids. A total of 1800 hydrocarbons were tentatively identified, including aliphatic hydrocarbons, aromatics, and isoprenoid hydrocarbons. The identified hydrocarbons by GC x GC-TOF-MS were far more than those by GC-MS.     

Pyrolysis of solid waste in a rotary kiln: influence of final pyrolysis temperature on the pyrolysis products

Temperature is one of the most important parameters in pyrolysis reaction. In present work, an externally heated laboratory-scale rotary-kiln pyrolyser was designed and developed. The influence of final pyrolysis temperature (FPT) on the pyrolytic products of solid wastes has been studied. Raising FPT caused increasing gas yield and decreasing semi-coke yield. The average heat value of the gas also changed with FPT. The content of aliphatic hydrocarbons in PE tar increased initially and then decreased with increasing FPT. Parallel to this, the content of aromatic ring changed conversely. FPT had obvious influence on the primary and elemental analysis data of the semi-cokes. The CO₂ reactivity of the semi-cokes also varied with the FPT. The kinetic parameters of the semi-cokes were different for the same material at the different FPT.     

Compositional analysis of UV-cured acrylic ester resins by pyrolysis–gas chromatography in the presence of organic alkali

Compositional analysis of UV-cured resins consisting of multi-component acrylic esters was studied by pyrolysis–gas chromatography (Py–GC) in the presence of organic alkali, tetramethylammonium hydroxide (TMAH). The pyrograms of the UV-cured resins formed from ethylene oxide modified bisphenol A diacrylate (EBADA) contained specific products such as methyl acrylate (MA) and various dimethyl ethers of ethylene oxide modified bisphenol A reflecting the numbers of ethylene oxide units in the original EBADA. Meanwhile the pyrograms of the UV-cured resins comprised of acrylated polyfunctional aliphatic alcohols such as pentaerythritol triacrylate (PETA) and dipentaerythritol hexacrylate (DPEHA) contained methyl ethers reflecting the structure of the original alcohols. In addition, considerable amounts of pyrolyzates with non-methylated hydroxyl groups were also detected for aliphatic alcohol moieties. The compositions of the UV-cured resins containing multi-component acrylic esters were also analyzed based on the relative yields of the characteristic pyrolyzates of each acrylic ester. For calibration purpose, a series of UV-cured standard samples, which contained known amounts of the individual acrylic ester and neopentylglycol diacrylate (NPGDA) used as an internal standard, were measured. The compositions of the multi-component UV-cured resins determined using this approach showed good agreement with the theoretical values estimated from the feed composition.     

Conformational preferences of model aliphatic diamides: Effect of the methyl side group on the polymethylene segment

The conformational preferences of N‐[3‐(acetylamino)‐2‐methyltrimethylene] acetamide and N‐[5‐(acetylamino)‐(S)‐2‐methylpentamethylene]acetamide were investigated using ab initio computational methods. These are model compounds of a number of substituted nylons‐m,n containing a methyl side group in the diamine unit. A comparison with the results obtained for their linear analogues have allowed us to determine the influence of the methyl side group on the conformational preferences of aliphatic diamides. Furthermore, the conformations compatible with the electron and X‐ray diffraction data recently obtained for the related substituted nylons‐m,n were identified.     

Applications of a new vapour-phase pyrolyser

The application of a device for the post-column vapour-phase pyrolysis of compounds after gas chromatographic separation is described. The system proposed permits a mixture to be separated, pyrolysis to be carried out and pyrograms to be obtained in the chromatograph with one flame ionization detector. The reproducibility of the retention time and the intensity of the pyrogram peaks were studied. Some examples of applications to the identification of unknown components in a single gas chromatographic analysis are given.     

Thermal degradation of aliphatic polyamides studied by field ionization and field desorption mass spectrometry

The aliphatic polyamides nylon 6.6, 6.9, 6.10, 6.12, 12.6, 12.10, and 12.12 of the diamine dicarboxylic acid-type were pyrolyzed in the ion source of a double-focusing mass spectrometer and the thermal degradation products were recorded by field ionization (FI) and field desorption (FD) mass spectrometry (MS). In the FI mode, several series of thermal degradation products differing in the number of polymer repeating units were detected up to 1000 Daltons. The main products were oligomers and, in addition, protonated dinitriles and various protonated nitriles are formed in large amounts except for nylon 6.6 and nylon 12.6. These two polymers form, in contrast to all other samples, large amounts of protonated amides and diamines. The technique employed allows distinction between oligomers already present in the original polymer and oligomers formed by thermal fission of bonds in the polymer chain. Reaction mechanisms are given that explain the products observed. High resolution experiments and accurate mass measurements were performed to confirm the proposed structures. In the FD mode, cationized oligomers (attached mostly to a sodium cation) were observed below 200°C with the dimers being the base peak for most samples. In contrast to the FI results, the monomers were only detected at very low intensities. Similarly, only weak signals for additional thermal degradation products were registered except for nylon 12.6. At higher temperatures the FD mass spectra gave protonated and doubly protonated oligomers in the high mass range up to 2000 Daltons, which resulted in complementary structural information about the polymers.     

Amide-exchange reactions in mixtures of N-alkyl amides and in polyamide melt blends

The amide-exchange reactions which cause copolymer formation in polyamide melt blends were studied with mixtures of N-ethylcaproamide and N-hexylacetamide containing small concentrations of caproic acid and hexylamine as a model system for melt blends of aliphatic polyamides. Amide exchange was found to involve acidolysis and aminolysis reactions with no detectable contribution of direct reaction between amide groups. Kinetics data are consistent with formation of an anhydride intermediate in amide acidolysis. Rate constants over the range 200–275°C and activation energies for amide acidolysis and aminolysis reactions are given. Equations are given for calculating amide exchange rates in polyamide melt blends and for relating degree of amide exchange to block copolymer composition.     

Polythioamides aliphatiques—IV. Etude des proprietes thermiques en correlation avec la structure du motif

We have already studied some physicochemical properties of aliphatic polythioamides and the contribution of the thioamide group to some of them. We now report the thermal behaviour of these condensation polymers and determine the functional group participation to molar melt and glass transition functions. These results allow us to compare polyamides, polyesters and polythioamides. We have also studied some polythioamides containing ether-linkages. Thermal degradation has been studied by thermogravimetric analysis.     

Synthesis of polyamides by ring-opening polyaddition: Reaction of 4,4′-disubstituted bisazlactones with diamines

Ring-opening polyaddition of 4,4′-disubstituted bisazlactones with various diamines was carried out in N-methyl-2-pyrrolidone to afford polyamides with pendant amide group having inherent viscosities of 0.17-0.51 in quantitative yields. The solution polymerization with aliphatic diamines was almost complete at room temperature within 24 hr. Nearly all of the polyamides were soluble in polar in polar aprotic solvents and in acidic solvents. These polymers began to decompose at around 200–300°C as determined by DTA and TGA under nitrogen.     

脂肪族聚酰胺热膨胀行为的研究

通过热膨胀测试,示差扫描量热分析(DSC)、广角X射线衍射(WAXD)与傅里叶变换红外光谱(FTIR)等方法研究了4种脂肪族聚酰胺玻璃化转变温度(Tg)、结晶行为以及氢键强度对热膨胀行为的影响,探索了影响脂肪族聚酰胺热膨胀的本质.DSC和X射线衍射结果表明,聚酰胺中结晶部分的热膨胀系数要低于无定形部分,但聚酰胺的熔融温度和结晶度对热膨胀的影响不够明确.相比较其它脂肪族聚酰胺,聚酰胺56(PA56)具有较高的玻璃化转变温度和较低的亚甲基/酰胺基(CH2/CONH)比例,表现出较低的热膨胀系数.研究发现,在相同条件下制备的脂肪族聚酰胺体系中,CH2/CONH比例或Tg与热膨胀系数具有明显的线性关系,随着CH2/CONH比例的降低或Tg的升高,热膨胀系数显著减小.FTIR的结果表明,聚酰胺分子链间的氢键密度和氢键强度随温度升高衰减的程度是影响其热膨胀行为的关键因素.