Determination of impurities in industrial caprolactam produced from toluene by SPME and GC–MS

Solid‐phase microextraction (SPME) in combination with gas chromatography‐mass spectrometry (GC–MS) was applied to study the impurities in industrial caprolactam produced from toluene. Various nitriles, lactones, amides, and alcohols were detected to be the main impurities in caprolactam products. Trace amounts of heterocyclic compounds, which had great effects on the quality of caprolactam, were also successfully detected. Those were pyrrole, 2‐ethyl‐3‐methyl pyrazine, 5,6,7,8‐tetrahydroquinoxaline, quinoxaline, 2,3‐dimethyl quinoxaline, 2‐pyridinamide, etc. The effects of some impurities on caprolactam quality and the polymerization of caprolactam as well as the possible origin of the main impurities were also discussed. This could be of great importance to the industrial purity control of caprolactam. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 3141–3144, 2006     

固相微萃取-气相色谱串联两级质谱法测定水中10种藻类代谢产物

文中建立了固相微萃取-气相色谱串联两级质谱法测定地表水中的10种藻类代谢产物的含量,研究了萃取时间、萃取温度、萃取剂量、萃取纤维等预处理参数对嗅味物质含量的影响,同时对不同规格的色谱柱进行分离效果比较。结果表明,在萃取时间为25 min、萃取温度为65℃、氯化钠含量为1.7 g的测定条件下,采用50/30μm DVB/CAR/PDMS萃取头进行预处理,HP-5MS色谱柱进行分离,质谱检测器进行测定,可以使检测结果达到最优效果。方法的质量浓度均达到5.00～100.00 ng/L,工作曲线回归方程的相关系数R²>0.995;方法检出限(2S/N)为0.14～1.00 ng/L。在纯水加标量为20.00、50.00、80.00 ng/L时,平均回收率为92.0%～109.0%,精密度RSD为0.4%～8.9%,实际水样加标的平均回收率为83.9%～101.8%。该方法检测浓度数量级在纳克级,灵敏度较固相萃取-气相色谱-质谱法提高1 000倍,更适合地表水和饮用水中低浓度藻类代谢产物的检测要求。     

Loss and transformation products of the aromatic antioxidants in MDPE film under long‐term exposure to biotic and abiotic conditions

The loss of a primary phenolic antioxidant Irganox 1010 and of a secondary phosphite antioxidant Irgafos 168 from a medium density polyethylene film (MDPE) was investigated after exposure of the film for 4 years to different environments such as aqueous media at pH5 and 7, open air, and compost, with an exposure of exposition of 25°C. An ultrasonic extraction technique using chloroform as extraction solvent was applied to recover the residual antioxidants from the polymeric matrix, and this was followed by High‐Performance Liquid Chromatography (HPLC) with acetonitrile as mobile phase and a quantitative analysis at a wavelength of 280 nm of the extracted antioxidants. The amount of antioxidant lost varied remarkably depending on the testing medium. The fastest loss of antioxidant was found on exposure to open air and sunlight while the slowest loss was observed in compost. Thermo‐analytical measurements were made to characterize the residual thermo‐oxidative stability of MDPE film in terms of oxidation temperature and oxidation induction time, to provide a greater insight into the underlying mechanisms of ageing in the different environments. Analysis by Gas chromatography–Mass Spectrometry (GC‐MS) revealed that degradation of the polymeric matrix resulted in the formation of hydrocarbons and oxygen‐containing compounds such as alcohols, carboxylic acids, aldehydes, and esters. The transformation products of the antioxidants formed as result of processing or exposure to the tested media were also identified. The transformation of the phenoxy radical of the Irganox 1010 produced the ester, acid, dealkylated cinnamate, and quinone products, whereas Irgafos 168 yielded oxidation products and the phenolic hydrolysis byproduct 2,4‐di‐tert‐butylphenol. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 974–988, 2002     

Long‐term mechanical and viscoelastic behavior of constitutive polymeric materials used for magnetic tapes

Creep‐compliance behavior of specially prepared magnetic tape materials was measured at elevated temperature levels to facilitate the use of a time–temperature superposition (TTS) process. This TTS process allowed for the construction of master curves at a reference temperature of 30°C, which were used to predict the long‐term viscoelastic behavior of the magnetic particle (MP) and metal‐evaporated (ME) tapes used in the study. The specially prepared samples allowed for the use of a rule of mixtures technique to determine the long‐term creep compliance of the front coat and back coat used for the magnetic tapes. To test the validity of this procedure, the front coat, substrate, and back coat data determined through separate experiments were used to calculate creep compliances of simulated tapes. These calculated creep‐compliance curves were then compared to measured data for the actual magnetic tapes. After determination and validation of the front coat, substrate, and back coat creep‐compliance data sets, they were used to determine strain distributions when the tapes are stored in a reel. Strain distributions were calculated for two cases, which reflect how tapes are stored in different drives: (1) the front coat (magnetic + nonmagnetic layer) is oriented away from the hub, and (2) the front coat is oriented toward the hub. Results showed that strain in the critical front coat of a tape is lower if it is stored with the front coat oriented toward the hub. In addition, the use of the creep‐compliance data showed that the MP tape front coat is more susceptible to creep than the ME tape front coat. The strain distributions in future magnetic tapes were also simulated by reducing the thickness and compliance of the layers. Results showed the importance of using lower compliance front coat, substrate, and back coat materials if thinner tapes are to be developed to increase the volume of information that can be stored in a magnetic tape reel. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 1142–1160, 2001     

Long‐Term Stability,Regeneration and Recycling of Imidazolium‐based Ionic Liquids

Ionic liquids (ILs) are discussed in many current research papers extensively in terms of their potential use in the chemical industry, as process aids and novel materials. The long‐term stability of the IL is for industrial applications as important as to know which species arise during the degradation due to thermal, mechanical, chemical or electrochemical stress. The investigation of the long‐term stability of two selected ILs over several months under process‐like conditions is presented with a subsequent analysis by LC‐MS to identify the resulting decomposition products. Knowledge about the occurring species and their analytical quantification are basis for the selection of appropriate processes for the separation of the decomposition products and the development of recycling processes for ILs. Particularly melt crystallization processes are suitable for separating structurally similar decomposition products that typically occur in the IL degradation.     

固相微萃取法(SPME)在农药残留分析中的应用

固相微萃取（SPME）是一种崭新的无溶剂萃取分离技术，SPME具有灵敏度高，无溶剂、样品用量少，而且简便、快速等优点，已成为分析方法前处理研究的一个方向。本文对固相微萃取技术及其在农药残留分析中的应用做了概述。     

Headspace solid‐phase microextraction with gas chromatography/mass spectrometry reveals a correlation between the degradation product pattern and changes in the mechanical properties during the thermooxidation of in‐plant recycled polyamide 6,6

The increased susceptibility of in‐plant recycled polyamide 6,6 toward thermooxidation was shown by headspace solid‐phase microextraction with gas chromatography/mass spectrometry (HS‐SPME/GC‐MS), tensile testing, differential scanning calorimetry (DSC), and Fourier transform infrared spectroscopy (FTIR). A correlation between the deterioration in mechanical properties and the formation of degradation products due to thermooxidation was found, and the most prominent decrease in mechanical properties coincided with the largest increase in the abundance of degradation products. The recycled materials had a shorter induction period toward oxidation, and their mechanical properties deteriorated faster than the mechanical properties of virgin material. The same trend was observed with HS‐SPME/GC‐MS because degradation products were found for recycled materials after oxidation times shorter than those for virgin material. Furthermore, larger amounts of degradation products were formed in the recycled materials. The high sensitivity of HS‐SPME/GC‐MS as an analytical tool was demonstrated because it was able to detect changes caused by oxidation considerably earlier than the other methods. Unlike DSC and FTIR, it could also show differences between samples recycled for different times. Four groups of degradation products—cyclic imides, pyridines, chain fragments, and cyclopentanones—were identified in thermooxidized polyamide 6,6. After 1200 h of thermooxidation, 1‐pentyl‐2,5‐pyrrolidinedione was the most abundant degradation product. Approximately four times more 1‐pentyl‐2,5‐pyrrolidinedione was formed in polyamide recycled three times than in virgin polyamide. Pyridines and chain fragments behaved toward oxidation and repeated processing like cyclic imides; that is, their amounts increased during oxidation, and larger amounts were formed in recycled materials than in virgin material. The cyclopentanone derivatives were present already in unaged material, and their amounts decreased during oxidation. Cyclopentanones were not formed because of the thermooxidation of polyamide 6,6. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 3396–3407, 2002     

Synthesis,characterization, and thermal properties of poly(methylvinylsilylene‐co‐styrene)

The copolymerization of methylvinyldichlorosilane (MVDCS) and styrene was carried out with various monomer feed ratios under dechlorination conditions with sodium in toluene at 110°C. The copolymers were obtained in 84–95% yields. The copolymerization of MVDCS and styrene with monomer feed ratios of 1 : 0.25 and 1 : 0.5 mainly gave insoluble polymers. The copolymers synthesized with monomer feed ratios of 1 : 1, 1 : 3, and 1 : 7 contained soluble fractions of 3, 26, and 47%, respectively. The copolymers were characterized with infrared, ¹H‐NMR, gel permeation chromatography, thermogravimetric analysis, pyrolysis/gas chromatography (PGC), X‐ray diffraction, and elemental analysis (silicon content). ¹H‐NMR and PGC studies suggested that the soluble fractions were mainly polystyrene. PGC studies indicated that the copolymers obtained with monomer feed ratios of 1 : 0.25 and 1 : 0.5 did not have any significant amount of polystyryl blocks, whereas the copolymers obtained with higher styrene feed ratios contained appreciable amounts of polystyryl blocks. The composition of the insoluble fractions of the copolymers was obtained from PGC data and was in good agreement with the composition calculated from the silicon content of the copolymers.© 2004 Wiley Periodicals, Inc. J Appl Polym Sci 91:3774–3784, 2004     

Effects of artificial weathering on the mechanical properties of paper‐based materials consolidated with polymeric materials

The study of polymer behavior over time represents the crucial stage in the setup of innovative methodologies for paper restoration. In this research, a series of laboratory simulations by accelerated aging and characterization tests by chemical and physical measurements were carried out on paper samples consolidated both by grafting polymerization with acrylic copolymers and by coating with waterborne polyurethanes with the aim of determining their harmlessness and long‐term effectiveness. In this way, our purpose was not only to verify possible risks for the paper materials but also to determine the advantages and potentialities of new restoration methods through an appropriate and essential working plan of investigations. From our evaluation, both the selected consolidation methods appeared unsuitable to be used in paper restoration because of the damage that they could cause on the paper materials because of their limited durability over time. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Long‐term investigation on hydrolytic degradation and morphology of poly(ethylene glycol terephthalate)‐b‐poly(butylene terephthalate) copolymer films

Poly(ethylene glycol terephthalate)‐b‐Poly(butylene terephthalate) copolymer (PEGT‐b‐PBT) films with different copolymer compositions were incubated in phosphate buffered saline under pH 7.4 at 37°C to study hydrolytic degradation and morphology up to 300 days. With the fall of intrinsic viscosity and mass of degraded films, SEM micrographs show that a set of particular and highly interconnected porous morphologies closely related to the content of PBT hard segments in copolymer is developed. Moreover, the variation in PBT crystallinity for copolymer films with weight ratio of 70/30 fluctuates with the development of degradation profiles, and PEGT content for copolymer films with weight ratio of 80/20 and 70/30 gradually decreases. The hydrolytic experiments demonstrate that the degradation of PEGT‐b‐PBT copolymer results from the cleavage of ester bonds between hydrophilic PEG and terephthalate. At the beginning period of degradation, PEGT‐b‐PBT copolymer films follow a typical mechanism of bulk degradation, and then undergo both bulk degradation and surface erosion, all of which finally generate the particular porous morphologies for copolymer films. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Synthesis and evaluation of poly(dioctyltin maleate‐styrene‐methyl acrylate) as a stabilizer for poly(vinyl chloride)

A novel thermal stabilizer poly(dioctyltin maleate‐styrene‐methyl acrylate) [P(DOTM‐St‐MA)] was synthesized by radical solution polymerization with benzene as the solvent and 2,2‐azobisisobutyronitrile as the initiator. The structure of terpolymer was characterized by FTIR and ¹H‐NMR spectra, and thermal stability of the stabilizer was measured by thermogravimetric analysis (TGA). Evaluation of [P(DOTM‐St‐MA)] as thermal stabilizer for poly(vinyl chloride) (PVC) was measured by acidimeter, and the extent of changing color of PVC was measured by thermal aging method. Compatibilities of four stabilizers with PVC were characterized by scanning electron microscope (SEM). The results showed that, with the same tin content in PVC mixtures, [P(DOTM‐St‐MA)] exhibited better performance as a PVC stabilizer compared with other stabilizers,such as poly(dibutylin maleate‐styrene‐methyl acrylate), DOTM, and dibutylin maleate (DBTM). Furthermore, [P(DOTM‐St‐MA)] had better compatibility with PVC in PVC processing. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Solid‐phase photocatalytic degradation of polystyrene with TiO2/Fe(St)3 as catalyst

A novel photodegradable TiO₂‐Fe(St)₃‐polystyrene (TiO₂‐Fe(St)₃‐PS) nanocomposite was prepared by embedding TiO₂ and Fe(St)₃ into the commercial polystyrene. Ferric stearate was added into polymer as cocatalyst in order to improve the dispersion in polystyrene and photocatalytic efficiency of TiO₂ nanoparticles. Solid‐phase photocatalytic degradation of the TiO₂‐Fe(St)₃‐PS nanocomposite was carried out in an ambient air at room temperature under ultraviolet lamp. The properties of TiO₂‐Fe(St)₃‐PS composite film were compared with that of the pure PS film and the TiO₂‐PS composite film, through weight loss monitoring, scanning electron microscope, gel permeation chromatogram, and FTIR spectroscopy. The photodegradation efficiency of TiO₂‐Fe(St)₃‐PS composite film was higher than that of the pure PS film and the TiO₂‐PS composite film under the UV light irradiation. The average molecular weight (M_w) of TiO₂‐Fe(St)₃‐PS composite film decreased 63.08%, and the number of average molecular weight (M_n) decreased 79.49% after UV light irradiation for 480 h. Photo‐oxidation leads to an increase in the low molecular weight fraction by chain scission, thereby facilitating biodegradation. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Accurate determination of hexanal in beef bouillons by headspace solid‐phase microextraction gas‐chromatography mass‐spectrometry

Lipid oxidation has great impact on the quality of food products through flavor and taste deterioration, reduction in nutritive value, and potential toxicity of the oxidized food components. Flavor and taste deterioration can be easily perceived and it represents one of the major causes of consumer complaints in the food industry. The deterioration of sensory properties is due to the decomposition products of hydroperoxides that easily isomerize and degrade into volatile compounds. Volatile products are responsible for flavor and taste deterioration. In this study, we present the development of the solid‐phase microextraction gas chromatography‐mass spectrometry (SPME‐GC‐MS) technique to quantify low amounts (μg/g range) of secondary oxidation products, i.e. hexanal. The optimization of SPME parameters is a difficult task because of the possibility of further formation of volatile products during analysis. Different parameters such as type of fiber, exposure time of the fiber to the sample headspace and the optimal temperature of absorption have also been investigated. The complete validation of the method was achieved by the determination of linearity, limits of detection and quantification and repeatability. We demonstrated that the SPME method is a valuable tool for the quantification of low amounts of secondary oxidation products such as hexanal. Therefore, this technique can be used to detect early formation of volatiles.     

Solid‐phase preparation method of silica‐supported 2,2′‐methylenebis(6‐tert‐butyl‐4‐methyl‐phenol) and its antioxidative behavior in styrene‐butadiene rubber

A solid‐phase preparation method is applied to the synthesis of a novel supported rubber antioxidant, silica–supported 2,2′‐methylenebis(6‐tert‐butyl‐4‐methyl‐phenol) (SiO₂‐2246), by directly reacting 2,2′‐methylenebis (6‐tert‐butyl‐4‐methyl‐phenol)(antioxidant 2246) with silica. FTIR, Raman spectroscopy and TGA confirm that the antioxidant 2246 is chemically bonded on the surface of the silica particles. The SEM observation shows that the SiO₂‐2246 is homogeneously dispersed in the styrene‐butadiene rubber (SBR) matrix. The results of the apparent activation energy and the attenuated total reflectance infrared spectrometry indicate that the antioxidative efficiency of the SiO₂‐2246 in SBR is superior to the corresponding low‐molecular‐weight 2246. The thermal oxidative stability of the SBR/SiO₂‐2246 composites is much higher than that of the SBR/SiO₂/2246 composites by comparing their mechanical properties retentions and crosslinking densities. Additionally, the advantages of SiO₂‐2246 also include low migration, low volatility, and low pollution. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43014.     

Long‐term stress relaxation behavior of predrawn poly(ethylene terephthalate)

Research has been carried out with the aim of better understanding the relevant properties of materials to be used in a new self‐healing cementitious composite material system. In a previous study, the buildup of stress in a heat‐activated restrained predrawn poly(ethylene terephthalate) (PET) specimen was investigated. In the current study, the long‐term stress relaxation behavior of such a restrained specimen has been explored so that its potential for use in the new material system can be better understood. The work includes an experimental study in which the stress in a number of PET specimens, restrained against longitudinal shrinkage, was measured during the initial heat activation and cooling phases, and then monitored for a further 6 months. These data were used to quantify the stress relaxation of the specimen and to inform the development of a new one‐dimensional numerical model to simulate the thermomechanical behavior of this material. This model is shown to be able to reproduce the observed short‐ and long‐term experimental behavior with good accuracy. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 41208.     

Prediction of long‐term service performance of polymeric materials from short‐term tests: Creep and prediction of the stress shift factor of a longitudinal polymer liquid crystal

The material studied is a longitudinal polymer liquid crystal (PLC). The creep behavior of the PLC is examined in the region of nonlinear viscoelasticity. The creep compliance D curves at nine different stress σ levels, from 10 to 50 J.cm^?3 at a constant temperature are determined and shifted along the log time axis for σ_ref = 10 J · cm^?3 to produce the D versus t/a_σ master curve. A fairly general formula for stress shift factor a_σ based on free volume v^f and the chain relaxation capability (CRC) derived by one of the authors is applied. The formula predicts values that agree with the experimental ones within the limits of the experimental accuracy. Thus, experiments at several stress levels can serve for prediction of long‐term behavior from short‐term tests. The same value of the Doolittle constant B is obtained separately from temperature shift and stress shift experiments for the PLC.     

Poly(lactic acid) properties as a consequence of poly(butylene adipate‐co‐terephthalate) blending and acetyl tributyl citrate plasticization

This study was aimed at the modulation of poly(lactic acid) (PLA) properties by the addition of both a low‐molecular‐weight plasticizer, acetyl tributyl citrate (ATBC), and a biodegradable aliphatic–aromatic copolyester, poly(butylene adipate‐co‐terephthalate) (PBAT). PLA/PBAT, PLA/ATBC, and PLA/PBAT/ATBC mixtures with 10–35 wt % ATBC and/or PBAT were prepared in a discontinuous laboratory mixer, compression‐molded, and characterized by thermal, morphological, and mechanical tests to evaluate the effect of the concentration of either the plasticizer or copolyester on the final material flexibility. Materials with modulable properties, Young's modulus in the range 100–3000 MPa and elongation at break in the range 10–300%, were obtained. Moreover, thermal analysis showed a preferential solubilization of ATBC in the PBAT phase. Gas permeability tests were also performed to assess possible use in food packaging applications. The results are discussed with particular emphasis toward the effects of plasticization on physical blending in the determination of the phase morphology and final properties. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Interface‐tailored and nanoengineered polymeric materials for (opto)electronic devices

For plastic (opto)electronic devices such as light‐emitting diodes (LEDs), photovoltaic (PV) cells and field‐effect transistors (FETs), the processes of charge (hole/electron) injection, charge transport, charge recombination (exciton formation), charge separation (exciton diffusion and dissociation) and charge collection are critical to enhance their performance. Most of these processes are relevant to nanoscale and interfacial phenomena. In this review, we highlight the state‐of‐the‐art developments of interface‐tailored and nanoengineered polymeric materials to optimize the performance of (opto)electronic devices. These include (1) interfacial engineering of anode and cathode for polymer LEDs; (2) nanoengineered (C₆₀ and inorganic semiconductor nanoparticles) π‐conjugated polymeric materials for PV cells; and (3) polymer and monolayer dielectrics/interfaces for FETs and light‐emitting and nano‐FETs. Copyright © 2009 Society of Chemical Industry