Characterising high mass materials in heavy oil fractions by size exclusion chromatography and MALDI-mass spectrometry

Several petroleum vacuum residues and a Maya asphaltene have been examined using size exclusion chromatography (SEC), using 1-methyl-2-pyrrolidinone as eluent. Aliphatic components are not dissolved in this solvent. All the samples showed a bimodal distribution. Material under the early eluting peak, excluded from column porosity corresponded to apparently very large molecular masses. The later eluting peak corresponded to molecules with a smaller range of masses and was relatively intense. The material excluded from column porosity is concentrated in the heptane-insoluble fraction; the peak of this fraction corresponding to smaller molecules shifted to earlier times than was found for the whole sample. In UV-fluorescence spectrometry, the heptane-insoluble materials did not fluoresce strongly. Materials excluded from column porosity showed no fluorescence, indicating that UV-fluorescence based methods are unable to detect high mass materials. MALDI-mass spectrometry indicated a bimodal distribution for the Maya asphaltene with a mass range up to m/z 40,000. Comparison of the low mass range of the spectrum with the small-size molecules detected by SEC indicated broad agreement for masses up to about 5000 u. However, if the excluded peak of SEC corresponds to the higher mass range up to m/z 40,000, then it is likely that these molecules are adopting three-dimensional conformations. Data from the hydrocracking of heavy oils was used to confirm some of the outlined findings.     

Viscous properties and microstructure of recycled eva modified bitumen

This paper deals with the viscous properties of recycled-polymer modified bitumens (PMBs) in a wide range of temperatures. With this aim, two different penetration grade bitumens (60/70 and 150/200) and recycled EVA copolymer (EVA_R) from agriculture films were processed in an open reactor using a four blade propeller. Polymer concentration ranged from 0 to 9 wt%. Viscous flow and DSC measurements, from 5 to 165 °C, and optical microscopy, at room temperature, were performed on the samples. From the experimental results obtained, we may conclude that the viscous properties of bitumen, at high temperature, are improved by adding recycled EVA copolymer in amounts that depend on bitumen penetration grade. Moreover, significant microstructural changes, related to the development of a polymer-rich phase, tend to occur in the bitumen as polymer concentration increased. These changes in microstructure have a significant influence on the flow behaviour of the binder and on its in-service performance. As a consequence, the use of recycled EVA in PMBs can be considered a suitable alternative from both environmental and economical points of view.     

定量体积排除色谱用于火药成分分析的研究

研究了定量体积排除色谱分析火药成分的方法,用ＷＡＴＥＲＳ－２４４型高效体积排除色谱仪对火药的成分进行了实验测定,对所得图谱进行了解析,讨论了具有重叠峰成分的分峰方法,给出了一些火药成分的标准曲线。并以单基火药和双迫火药为例将实验结果与化学分析方法结果进行了比较。结果表明,用定量体积排除色谱法能同时分离与测定火药的各种成分操作简单,结果准确,这对火药的生产与研究具有重要的应用价值。     

Rheological behavior of bitumen modified by reclaimed polyethylene and polypropylene from different recycling sources

This work studied the rheological, thermal, and mechanical properties of bitumen modified by reclaimed polyethylene (PE), and polypropylene (PP) from different recycling sources. The rutting resistance under high temperature of polymer modified bitumen (PMB) was investigated by rheologically temperature ramp test and multiple stress creep recovery (MSCR) test. It is found that for some modified bitumen, a plateau of complex modulus G^* could be formed with temperature increment, revealing rheological stability. Furthermore, these samples with rheological stability revealed a higher creep recovery and lower creep compliance measured by the MSCR test. Glass transition temperature (T_g) measured by dynamic mechanical analysis was used to evaluate the crack resistance under a low temperature of PMB. The influence of recycled PE on the T_g of modified bitumen was different from that of recycled PP modified bitumen, as compared with corresponding virgin polymer modified bitumen. A possible reason for the various effect of recycling sources on the service property of modified bitumen was explored by crystallization and melting behaviors of polymer in bitumen since that polymer with higher crystallinity degree could endow the modified bitumen stiffness, which was closely, related to their service property especially the rutting resistance.     

Molar mass analysis of polyamides-11 and -12 by size exclusion chromatography in HFiP

The SEC analysis of polyamide-11 and polyamide-12 can be conducted free of association and aggregation phenomena when hexafluoroisopropanol + 0.05 mol/L potassium trifluoroacetate are used as the mobile phase. The calibration of the SEC system can be conducted in different ways. As stationary phases non-polar polystyrene and polar perfluoro silicagel were tested. The investigations showed that the polystyrene gel exhibits hydrophobic interactions with the polyamides while with the silicagel selective interactions were not found. Investigating different options for SEC calibration it was found that conventional PMMA calibration does not yield correct results. The universal calibration approach based on PMMA calibration did not work either. Correct molar masses were obtained when the PMMA calibration curve was corrected with data from polyamide blends using a simplex algorithm. Alternatively, calibration can be conducted with broadly distributed polyamides that were first fully characterized by SEC-MALLS. The resulting molar mass distributions for different sets of polyamides were compared with molar masses that were determined directly by SEC-MALLS and excellent correlation was obtained.     

Termini and main-chain composition of monomethoxy-terminated poly(ethylene glycol) studied by two-dimensional column chromatography

Samples of poly(ethylene glycol) especially those with functionalized ends have dimeric, trimeric, and tetrameric components at twice, three times, and four times as high a molecular weight (MW) as that of the main component. We used two-dimensional column chromatography to evaluate the MW and identify the terminal groups in each component. The first step is high osmotic pressure chromatography to prepare a sufficient amount of fractions that contain different percentages of the multimeric components. In the second step, each of the fractions was characterized by using regular size exclusion chromatography and high-resolution NMR. Decomposition of the chromatogram combined with isolation of the terminal methoxy peak in the NMR spectrum led to unique identification of the terminal groups. We thus found that the monomeric component is monomethoxy-terminated whereas the dimeric and other multimeric components are mostly dihydroxy-terminated.     

傅里叶变换红外光谱法测定SAN中丙烯腈组分含量

采用傅里叶红外光谱（FTIR）法定量分析丙烯腈-苯乙烯共聚物（SAN）中的丙烯腈,利用丙烯腈在2237 cm-1处的吸收峰及苯乙烯在700 cm-1处的吸收峰,建立了FTIR法快速测定SAN中丙烯腈组分含量的标准工作曲线,对其准确性和精密度进行了评价。结果表明,测定样品的最大相对误差为2.8 %,重复测定同一样片的相对标准偏差为2.48 %,方法的准确性和精密度良好。     

季戊四醇四(3-巯基丙酸)酯/乙烯基硅氮烷体系光聚合反应动力学红外光谱法研究

用傅立叶变换红外光谱法研究了季戊四醇四(3-巯基丙酸)酯/乙烯基硅氮烷体系光聚合反应动力学,跟踪检测了巯基和乙烯基吸光度的变化,测定了光聚合反应过程的巯基和乙烯基的转化率,发现巯基与乙烯基以化学计量比1∶1反应。在巯基和乙烯基物质的量相等和乙烯基过量的情况下,按照一级反应处理的动力学数据都得到较好的线性关系,且反应速率与巯基浓度的一次方成正比。     

Effect of blanching on volatile compounds and structural aspects of Cordyceps militaris dried by microwave-assisted pulse-spouted bed freeze-drying (MPSFD)

Effect of low temperature blanching at 50°C (for 15, 30, and 60?min) and high temperature blanching at 100°C (30, 60, and 120?s) on volatile compounds and structural properties of Cordyceps militaris dried by microwave-assisted pulse-spouted bed freeze-drying were investigated. A total of 83 volatile compounds were identified. Blanching at 100°C remarkably decreased the ketones and alcohols while contributed to the formation of alkanes. The absence at 993?cm^?1 and the appearance near 1548?cm^?1 in samples blanched at 100°C were observed, indicating blanching at high temperature would cause the loss of polysaccharides and the degradation of proteins. Principal component analysis and cluster analysis suggested that volatile compounds in untreated samples and those blanched at 50°C for 15?min were similar. In general, blanching at 50°C for 15?min is recommended regarding the retention of flavor components and structural properties of dried C. militaris.     

Separation of acylglycerols,FAME and FFA in biodiesel by size exclusion chromatography

Size‐exclusion chromatography separates solutes according to their molecular sizes. Free fatty acids (FFA), fatty acid methyl esters (FAME) and monoacylglycerols (MG) of vegetable oils or animal fats have very close molecular sizes and they cannot be baseline‐separated on a single Phenogel column (100 Å, 300 mm × 7.8 mm ID, 5 µm) by using tetrahydrofuran (THF) as the mobile phase. When toluene is used as the mobile phase, triacylglycerols (TG), diacylglycerols (DG), MG and FAME are well separated but there is no baseline resolution between DG and FAME. In addition, the elution order of MG and FAME is reversed. However, baseline separation of all the above lipid classes can be achieved by using toluene containing THF, acetone, dichloromethane, ethyl acetate or acetic acid as the solvent modifier. Acetic acid (0.25%) as the solvent modifier gives the best resolution and all the reference peaks are symmetrical. The detection limit of each class of lipids is 0.1 µg. The correlation coefficient values (between 1 and 100 µg) of all the lipid classes are better than 0.99. Thus, the determination of biodiesel products in the biodiesel reactor is very much simplified.     

Influence of UV stabilizers on the weathering of PETG and PCTT films

The influence of two UV photostabilizers on the photostability of Polyethylene-co-CHDM-terephthalate (PETG) and Polycyclohexylenedimethylene-Co-TMCD-terephthalate (PCTT) copolyester films was investigated. Untreated films and films containing stabilizer were irradiated. The resulting films were analyzed by attenuated total reflectance Fourier transform infrared (ATR FTIR) spectroscopy, gel permeation chromatography (GPC), and X-ray photoelectron spectroscopy (XPS). FTIR spectra of the irradiated films containing Cyasorb 1164 showed less change in intensity of the broad peak corresponding to OH groups, than the films containing Cyasorb 3638, indicating that Cyasorb 1164 is a better photostabilizer for these films. XPS results showed that the decrease in C/O ratio, due to photodegradation, was greater in films containing Cyasorb 3638 compared to those containing Cyasorb 1164. The formation of degradation products was evident from emission spectra arising from extracts of irradiated films based on PCTT +10% Cyasorb 3638, but no degradation products were apparent in extracts from irradiated PCTT +10% Cyasorb 1164. UV-absorption spectra of Cyasorb 1164 overlap more substantially with the absorption spectra of PETG and PCTT. The results from FTIR, XPS, and GPC analyses of the irradiated PETG and PCTT films demonstrated that Cyasorb 1164 was more effective than Cyasorb 3638 in enhancing resistance to UV-induced weathering. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48198.     

Mechanical properties and surface morphology of photodegraded polyoxymethylene modified by a core–shell acrylate elastomer with UV stabilization

In order to improve the photostability of polyoxymethylene (POM), a core‐shell acrylate elastomer with UV stabilization, i.e. poly[(methyl methacrylate)‐(butyl acrylate)‐2‐hydroxy‐4‐(3‐methacryloxy‐2‐hydroxypropoxy)benzophenone] (core‐shell poly(MMA‐BA‐BPMA)), was added into the POM matrix using a melt‐mixing method. The effect of the modification with core‐shell poly(MMA‐BA‐BPMA) on POM was compared with that of poly(MMA‐ co ‐BA‐ co ‐BPMA) copolymer. Scanning electron microscopy, metallographic microscopy, Fourier transform infrared spectroscopy, differential scanning calorimetry, X‐ray diffraction and X‐ray photoelectron spectroscopy were employed to characterize POM blends before and after UV irradiation, and the mechanical properties of the POM blends were investigated. The results showed that core‐shell poly(MMA‐BA‐BPMA) improved well the compatibility with and toughness of the POM matrix, and its light‐stable functional groups could increase the UV resistance of POM blends. During UV aging, the impact strength and elongation at break of POM/core‐shell poly(MMA‐BA‐BPMA) blends were retained, the growth rate of surface cracks of POM was inhibited effectively by core‐shell poly(MMA‐BA‐BPMA) and the degree of photo‐oxidation of POM blend surfaces was improved to a certain extent. Compared with poly(MMA‐ co ‐BA‐ co ‐BPMA), core‐shell poly(MMA‐BA‐BPMA) had a better UV stabilization effect on the POM matrix. Our results indicate that the core‐shell acrylate elastomer with toughening and UV stabilization functions can significantly improve the long‐term UV stability of POM. Copyright © 2012 Society of Chemical Industry     

J-116结构胶粘剂与QY8911树脂匹配性研究

本文利用漫反射傅立叶交换红外光谱法、扫描电镜法和溶度参数法研究了J－116结构胶粘剂和QY8911树脂之间的相容性．     

傅立叶变换红外光谱法测定黄姜中皂素含量

直接对黄姜进行压片,利用傅立叶变换红外光谱法测定黄姜中皂素含量.结果表明,以1647 cm-1处的吸收峰作为分析峰,在0.5%～5.0%含量范围内峰面积和含量具有良好的线性关系,相关系数为0.9690,加标回收率为99.12%,相对标准偏差RSD为0.22%.测定结果与传统的重量分析法相近,实现了黄姜中皂素含量的无损分析.     

Uniaxial deformation of an elastomer nanocomposite containing modified carbon nanofibers by in situ synchrotron X-ray diffraction

Structure and property of a nanocomposite consisting of modified carbon nanofibers (MCNFs), homogenously dispersed in an elastomeric ethylene/propylene (EP) random copolymer (84.3 wt% P) matrix, were studied by in situ synchrotron X-ray diffraction during uniaxial deformation. The MCNF acted as a nucleating agent for crystallization of the α-form of isotactic polypropylene (iPP) in the matrix. During deformation at room temperature, strain-induced crystallization took place, while the transformation from the γ phase to α phase also occurred for both unfilled and 10 wt% MCNF-filled samples. The tensile strength of the filled material was consistently higher than that of pure copolymer. However, when compared with pure copolymer, the highly stretched nanocomposite exhibited a higher amount of unoriented crystals, a lower degree of crystal orientation and a higher amount of γ crystals. This behavior indicated that polymer crystals in the filled nanocomposite experienced a reduced load, suggesting an effective load transfer from the matrix to MCNFs. At elevated temperatures, the presence of MCNFs resulted in a thermally stable physically cross-linked network, which facilitated strain-induced crystallization and led to a remarkable improvement in the mechanical properties. For example, the toughness of the 10 wt% nanocomposite was found to increase by a factor of 150 times at 55 °C.     

FT-NIR法快速测定烟草中的水溶性糖

采用偏最小二乘法建立了烟草中葡萄糖、果糖、蔗糖和麦芽糖分析的近红外预测模型,相关系数分别为:0.96327、0.96138、0.93968、0.95638,交叉验证均方残差分别为:0.240、0.189、0.126、0.049。     

FT-NIR快速测定烟叶及卷烟烟丝中挥发碱的含量

采用傅立叶变换近红外光谱技术采集烤烟烟叶和卷烟烟丝样品的近红外光谱,结合水蒸汽蒸馏法测定样品中挥发碱含量的数据,采用偏最小二乘法(PLS)分别建立了预测烤烟烟叶和国内品牌卷烟烟丝中挥发碱含量的近红外模型,两种模型的相关系数分别为0.95396和0.96558。进行了准确性和重复性实验。实验表明,近红外光谱法与标准方法之间不存在显著性差异,可以很好的应用于两类样品挥发碱含量的快速检测。     

Characterization and thermal properties of poly(n‐butyl acrylate‐g‐styrene) graft copolymers

Poly(butyl acrylate‐g‐styrene) graft copolymers were prepared by free‐radical polymerization using a polystyrene macromonomer carrying a methacryloyloxy group at the chain end and they were characterized by size‐exclusion chromatography, and Fourier transform infrared spectroscopy. Glass transition temperatures and degradation behavior were determined by thermal analysis. Only a single glass transition temperature was observed for the resulting graft copolymers, indicating the miscibility between the poly(styrene) phase and poly(butyl acrylate) (pBA) phase in the graft copolymer. The incorporation of polystyrene segments in the graft copolymer improved the thermal stability of pBA and enhanced the apparent activation energy for the thermal degradation of pBA. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 80: 783–789, 2001     

Fractionation and Analysis of an Impact Poly(propylene) Copolymer by TREF and SEC‐FTIR

TREF fractionation was combined with SEC‐FTIR analysis to measure the compositional heterogeneity within a commercial impact PP copolymer. The chemical composition of all fractions was determined as function of their molecular weight distribution. This approach proved to be highly successful at identifying different constituents within fractions exhibiting bimodal molecular weight distributions. Furthermore, the determination of ethylene and propylene crystallinity distribution across the molecular weight distribution confirmed the morphological nature of each of the components of the bimodal distribution. It is demonstrated that the combination of TREF and SEC‐FTIR provides a simple alternative to more time‐consuming conventional ways of characterising impact PP copolymers of complex heterogeneity.

     

Polymerization of an epoxy resin modified with azobenzene groups monitored by near‐infrared spectroscopy

New photosensitive materials containing photochromic azobenzene moieties were synthesized. For this purpose, an epoxy resin based on diglycidyl ether of bisphenol A (DGEBA) was reacted with an azobenzene chromophore (disperse orange 3, AZ) to satisfactorily synthesize an azo‐modified prepolymer, which was then used to generate series of epoxy‐based polymers containing azo groups. Three different amines were used as hardeners, with the aim of obtaining materials with different chemical structures. Understanding the epoxy resin polymerization kinetics is essential for intelligent processing of materials. Near‐IR (NIR) spectral analysis was used to follow the polymerization kinetics. The quality of the NIR spectra enables concentrations of individual chemical species to be measured in real time. Conversion of epoxy and primary amine groups, as well as the concentration of different groups, as a function of reaction time was therefore calculated by this spectroscopic technique. Samples containing azo units were compared to the pure DGEBA/amine systems. Results showed that the azo‐prepolymer incorporation has an accelerating effect on polymerization rate. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009