Identification of acrylate copolymers using pyrolysis and gas chromatography

A combination of pyrolysis and gas chromatography were used to investigate thermal degradation products formed from acrylic copolymers containing alkyl acrylate and methacrylate. The method provided an analytical tool for characterizing the chemical composition and structure of the degradation products. Thermal degradation of the synthesized copolymers was analyzed using isothermal (250 °C) pyrolysis–gas chromatography. The degradation process, and the nature and amount of pyrolysis products, provides relevant information about the thermal degradation of acrylic copolymers and the mechanism of pyrolysis. During pyrolysis, the formation of corresponding olefins, alcohols, acrylates and methacrylate was observed.     

Thermal degradation of copolymers based on selected alkyl methacrylates

The thermal stability and thermal degradation of copolymers based on selected alkyl methacrylates at temperatures between 250 and 400?°C have been studied using pyrolysis?Cgas chromatography. The type and composition of thermal degradation products gave useful information about the mechanism of pyrolysis of copolymers synthesized by using typical commercially available alkyl methacrylates. It was observed that the main thermal degradation products from alkyl methacrylate copolymers are monomers of alkyl methacrylates using by synthesis. Other pyrolysis by-products formed during thermal degradation were carbon dioxide, carbon monoxide, methane, ethane, methanol, ethanol, and propanol-1.     

废弃印刷电路板材料裂解产物的高分辨裂解气相色谱-质谱分析

采用高分辨裂解气相色谱-质谱法(PyGC-MS)分析了FR-4型印刷电路板粉末样品的裂解产物。在氦气氛围中,分别在350,450,550,650和750 ℃下对印刷电路板粉末样品进行热裂解,并通过毛细管气相色谱-质谱对裂解产物进行分析,研究了不同裂解温度下裂解产物分布以及主要裂解产物的产率与裂解温度的关系,根据热分解产物的组成,探讨了热分解反应机理。     

聚苯基不对称三嗪的热分解

用高分辨裂解气相色谱－质谱（ＨＲＰｙＧＣ－ＭＳ）考察了由对苯二眯腙和四种不同芳香族四酮合成的聚苯基不对称三嗪的热分解行为，鉴定了相应裂解产物的组成、分布及其与高分子结构的关系，并用热重法（ＴＧ）测定了它们的热分解反应动力学参数，提出了其热分解反应机理．     

Thermal degradation of poly(alkyl methacrylates)

The thermal degradation of selected poly(alkyl methacrylates) at temperatures between 300 and 800 °C was investigated by pyrolysis gas chromatography. Quantitative characterization of the pyrolysis products yields insights into the mechanism for thermal degradation of poly(alkyl methacrylates) under these conditions. Unsaturated monomeric alkyl methacrylates, carbon dioxide, carbon monoxide, methane, ethane, methanol, ethanol, and propanol were formed during thermal degradation of poly(alkyl methacrylates).     

聚亚苯基苯并二噻唑与聚亚苯基苯并二噁唑的热分解

用高分辨裂解气相色谱 质谱（ＨＲＰｙＧＣ ＭＳ）研究了聚亚苯基苯并二噻唑、聚亚苯基苯并二唑的热分解行为,鉴定了相应裂解产物的组成、分布及其与高分子结构的关系,并用热重法（ＴＧ）测定了它们的热分解反应动力学参数,提出了其热分解反应机理     

生物质主要组分低温热解研究

利用热重分析仪和裂解气质联用仪进行生物质主要组分低温热解特性研究。热重实验结果表明,生物质主要组分的热稳定性为：纤维素>木质素>半纤维素。半纤维素主要热解温度在210℃～320℃,而纤维素和木质素的主要热解温度分别在310℃～390℃和200℃～550℃。裂解气质联用实验考察不同温度对生物质主要组分低温热解产物的影响。半纤维素热解产物主要有乙酸、1-羟基-丙酮和1-羟基-2-丁酮,纤维素热解产物主要包括左旋葡聚糖和脱水纤维二糖,而木质素热解产物主要是邻甲氧基苯酚。     

Relevance of analytical pyrolysis studies to biomass conversion

The principles and methods of soft ionization mass spectrometry in combination with pyrolysis of macromolecules are outlined. Essential features of the newly developed techniques are the extension of the recorded mass range and the almost exclusive formation of molecular ions of the pyrolyzates. Using field ionization and field desorption mass spectrometry at low and high mass resolution, with electrical and photographic detection, pyrolysis products of biomass were analyzed for the first time. The results of flash pyrolysis by Curie-point heating and thermally programmed degradation of biopolymers are compared.The main topic is the evaluation of the methodology for time- and temperature-resolved pyrolysis. The thermograms and pyrolysis mass spectra obtained enable the study of pyrolysis reactions and the chemical fingerprinting of complex biological matter. The kinetics for the devolatilization of individual chemical species or classes of compounds can be monitored. Curie-point pyrolysis of biopolymers such as kappa-carrageenan and time-programmed degradation of cellulose and lignin are reported. Furthermore, preliminary investigations of pine wood and coal illustrate the potential of the introduced methods.     

Determination of the temperature—time profile of the sample in pyrolysis—gas chromatography

The mean temperature-time profile in a sample has been determined in order to establish whether it is possible to equate the temperature of the pyrolyzer with that of the sample being pyrolyzed. This was done by studying the degradation of cis-1,4-polybutadiene be sequential pyrolysis. The rate of degradation was determined for different amounts (0.5–20 μg) of sample. The temperature dependence of the degradation rate was determined from an Arrhenius plot. The experimental results were combined with theoretically derived expressions for the heating of samples subjected to pyrolysis. The temperature–time profiles of different amounts of sample could then be calculated.It was found that samples thinner than 1 μm were heated to a mean temperature of 95% of the temperature of the pyrolyzer in 40 ms or faster. Too thin samples can give rise to noticeable catalytic effects.By choosing the appropriate pyrolysis conditions of sample thickness, time and temperature it is possible to assume that the temperature of the sample is nearly the same as that of the pyrolyzer.     

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.     

Pyrolysis of polypropylene: I. Identification of compounds and degradation reactions

Pyrolysis of two polypropylene samples (degrees of isotacticity 0.50 and 0.85) has been carried out by flash pyrolysis and distillation pyrolysis. The analytical coupling of flash pyrolysis, gas chromatography and mass spectrometry allowed the analysis of the degradation products and their evolution with temperature between 500 and 900°C to be followed under different experimental conditions.The mechanism of polypropylene degradation is compared with the radical mechanism of polystyrene degradation.The depolymerization reaction leading to the production of monomer (25%) is not the most important degradation reaction. The transfer reactions predominate and generate the following products: 2,4-dimethyl-1-heptene (27–32%), pentane (ca. 8%), 2,4,6,8-tetramethyl-1-hendecene (7–18%) and 2,4,6-trimethyl-1-nonene (4–10%).     

Thermal degradation of polyurethane based on MDI and propoxylated trimethylol propane

A polyurethane based on diphenyl methane diisocyanate (MDI) and propoxylated trimethylol propane was thermally degraded by using the techniques of pyrolysis and thermogravimetric analysis (TGA) in an inert atmosphere. Identification of pyrolysis gaseous products at 600°C showed that the first degradation step consists of a reversal of the polycondensation process, i.e., dissociation into starting polyol and diisocyanate, followed by the polyol degradation and a probable diisocyanate polymerization. Kinetic parameters were determined using dynamic and isothermal TGA curves. It is shown that the degradation can be closely compared with a random chain scission process.     

Pyrolysis—gas chromatography of poly(3-methyl-1-alkenes)

The pyrolysis—gas chromatograpic behaviour of poly(3-methyl-1-butenes) and poly(3-methyl-1-pentenes) with different monomer units was investigated. Both polymers have two different units in their polymer chains, that is, 1, 2- and 1,3-structures. The amounts of the pyrolysis products vary because of the different degradation mechanism of each unit. With poly(3-methyl-1-butenes) the amounts of the two units can be evaluated from the amounts of some of the pyrolysis products.     

竹材非等温热解动力学

利用热重分析技术对竹材在高纯N2条件下,从室温至1273K进行了非等温热解分析,研究了升温速率(5、10、20和40K/min)对热解过程的影响,探讨了其热解机理。研究表明,竹材非等温热解过程主要分为失水干燥、快速热解和缓慢分解三个阶段组成,其中第二阶段是整个过程的主要阶段,析出大量挥发分造成明显失重。升温速率对热解过程有显著影响,随着升温速率的增加,最大热解速度增大,对应的峰值温度升高,热滞后现象加重,热解各阶段向高温侧移动。热解机理满足一维扩散Parabolic法则,反应机理函数为g(α)=α2。不同升温速率下活化能为75.32-82.99kJ.mol-1,指前因子为1.17×105-1.12×106min-1。     

Influence of structural factors on degradation product formation: Primary pyrolysis products of poly(acyl sulfides) investigated by direct pyrolysis mass spectrometry

Thermal degradation of two poly(acyl sulfide) polymers, poly(adipoyl sulfide) (PADS) and poly(terephthaloyl sulfide) (PTS) was investigated by direct pyrolysis mass spectrometry (DPMS). The structures of pyrolysis products detected in the DPMS analysis of both PADS and PTS indicate that the thermal degradation takes place mainly through a loss of carbon monoxide and carbonyl oxysulfide leading to the formation of cyclics. In the case of PADS, linear products with thioacid end groups were formed through hydrogen transfer reactions. In the case of PTS, almost equal proportions of linear products with phenyl end groups and cyclic products were formed. The mechanism of formation of degradation products has also been addressed.     

Study of the early deactivation in pyrolysis of polymers in the presence of catalysts

In this work, the early degradation step of the pyrolysis of some polymers in the presence of certain catalysts has been studied using thermogravimetric analysis (TGA). Three commercial polymers (PE, PP and EVA) and three catalysts were studied (ZSM-5, MCM-41a, and MCM-41b), and the MCM-41a catalyst has been selected for the analysis of the earlier steps of the pyrolysis process carried out in the presence of catalysts. Several cycles of heating–cooling were performed using a thermobalance, in order to analyze the influence of the first stages of decomposition on the activity of the more accessible active sites involved. In this way, the behaviour of the polymer–catalyst mixtures (20% (w/w) of catalyst) was studied and compared with that observed in the corresponding thermal degradation as well as in the pyrolysis in the presence of catalysts, in a single heating cycle.The results obtained clearly show the existence of an early degradation step. For a polymer–catalyst system with low steric hindrances such as PE-MCM-41, this early degradation step causes a noticeable decrease of the catalyst activity for the main decomposition step (i.e., cracking of the chain). The decrease of the catalytic activity is lower for a polymer–catalyst system with higher steric restrictions, as occurs in the EVA-MCM-41 degradation process. However, in this case, the catalyst activity in the first decomposition step (i.e., the loss of the acetoxi groups) is noticeable decreased after one pyrolysis run, thus reflecting that the active sites involved are mainly the most accessible ones.     

Thermal Degradation of Polystyrene-Polydimethylsiloxane Blends

Specific features of thermal degradation of polystyrene-polydimethylsiloxane blends were studied, and the effect of the organosilicon polymeric additive, polydimethylsiloxane, on the heat resistance of polystyrene was examined. The thermal degradation products were analyzed by gas chromatography-mass spectrometry. A mechanism of the joint pyrolysis was suggested.     

Identification of pyrolysis products of polysulphides by collisionally activated decomposition linked scanning mass spectrometry

Collisionally activated decomposition (CAD) linked scan mass spectra have been used in the identification of pyrolysis products obtained by the direct pyrolysis of some polysulphides in a mass spectrometer. Structures were determined by comparing the CAD spectra of the pyrolysis products with those of authentic compounds. The results are of help in elucidating the thermal degradation mechanisms that occur in the pyrolysis of the polysulphides investigated.     

Thermal degradation mechanisms of liquid crystalline aromatic polyesters studied by pyrolysis–gas chromatography/mass spectrometry

The thermal degradation mechanisms of liquid crystalline aromatic polyesters (LCPs) prepared from p-hydroxybenzoic acid (PHB), biphenol (BP), and terephthalic acid (TA) were studied by pyrolysis–gas chromatography/mass spectrometry (Py-GC/MS). The LCP containing deuterated terephthalate units and the LCPs that have different comonomer ratios were examined. On the basis of the pyrolysis products determined, the origin of the main pyrolysis products (benzene, phenol, biphenyl, phenyl benzoate, etc.) from the corresponding comonomer units were estimated and their thermal degradation mechanisms were eventually discussed in detail.     

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.