Methods for study of thermal aging and stabilization of grafted acrylonitrile-butadiene-styrene (ABS) terpolymers

Acrylonitrile-butadiene-styrene (ABS) grafted terpolymers are apt to oxidize at an elevated temperature and its stabilization by an antioxidant is critical to processing and performance. The differential thermal analysis was used to study the effect of the AgeRite® Geltrol, a modified high molecular weight hindered phenol antioxidant, on the ABS thermal oxidation. The Kissinger equation was found to be accurate enough to determine the activation energy of oxidation. The induction time was also measured and these results were compared with the activation energies. The polybutadiene component of ABS was oxidized rapidly around 200°C under an oxygen atmosphere while the styrene-acrylonitrile (SAN) component was oxidized at a higher temperature. Air oven aging at 130°C affected the Izod impact (notched), ultimate elongation, but not the ultimate tensile, melt index and morphology. It further confirmed that the polybutadiene component was oxidized and the SAN component was fairly stable at 130°C in air.     

Computer aided spectroscopy

Techniques are being developed which have as their objective improvement in the accuracy of infrared absorbance measurements and more exact recording of the true band shapes. From these improved spectra, accurate quantitative parameters are being obtained which can supplement or even supplant the present chart recordings as the fundamental spectral representations. These techniques include methods for processing spectra to eliminate most of the instrumentally introduced artifacts and to resolve the corrected spectra into algebraic representations in the form of sums of distribution functions. The consequences of the increasing use of these techniques will be to improve significantly our ability to do both qualitative and quantitative analysis. Presented at the AOCS-AACC Joint Meeting, Washington, D.C., April, 1968.     

An investigation of microstructure of styrene-methacrylonitrile copolymers by FT-IR spectroscopy

Summary The microstructure of styrene-methacrylonitrile copolymers has been investigated by FT-IR spectroscopy. The CN bond stretching frequency was shifted to a higher value with an increase in the methacrylonitrile (MAN) content in the copolymers. There was no linear relationship between the CN frequency and the diad fraction of MAN-MAN linkages in the copolymer chain, as reported previously for styrene-acrylonitrile copolymers. Different methods for the copolymer sample preparation can cause differences in the shifts in the CN frequency. This suggests that the polymer morphology plays an important role. A study of blends of poly(methacrylonitrile) (PMAN) with polystyrene has shown that the CN frequency is shifted to a higher value with an increase of the PMAN composition of the blends.     

Characterisation of an Egyptian coal by Mossbauer and FT-IR spectroscopy

Six coal samples collected from Maghara Coal Mine, North Sinai, Egypt, at different depths (52-87 m) were characterised by Mossbauer (MS) and Fourier Transform Infrared (FT-IR) spectroscopy. The moisture and ash content and the ultimate analysis are given. The iron minerals were studied by MS. Jarosite (ferric sulphate) and pyrite have been found in the sample taken at 52 m. However, ferrous sulphate and pyrite are present in the other samples. On the other hand, several structural parameters such as H_ar/H_al and H_ar/C_ar were calculated from FT-IR spectra as a function of depth. These parameters give a quantitative determination of the aromaticity, which was found in the range between 0.46 and 0.59, similar to that reported in the literature for subbituminous coals.     

Interaction of methane with surface of alumina studied by FT-IR spectroscopy

Methane adsorption on alumina was investigated by FT-IR spectroscopy at 173 K. Adsorbed methane gives four distinct IR bands at 3008, 3000, 2900 and 1305 cm^–1 which are attributed to v₁ (2900 cm^–1), v₃ (3008, 3000 cm^–1), and v₄ (1305 cm^–1) modes of methane respectively. The appearance of the v₁ mode indicates that the T_d symmetry of methane is distorted by the adsorption. The intensities of these bands increase significantly with outgassing temperatures of alumina, reach their maxima at an outgassing temperature near 773 K, and then decrease with further higher outgassing temperatures. Two hydroxyls with IR bands at 3750 and 3665 cm^–1 are perturbed evidently by the adsorbed CH₄ thereby resulting in two redshifted bands at 3707 and 3640 cm^–1. Coadsorbed CO slightly affects the adsorbed CH₄ indicating the very weak interaction between CH₄ and surface cations of alumina. It is proposed that the adsorbed CH₄ on alumina is formed mainly via the interaction of CH₄ with both surface hydroxyl and c.u.s. oxygen anion.     

聚氨酯胶黏剂降解行为的在线红外表征

文中采用自制的“在线检测平台”与红外光谱方法相结合技术,进行了聚氨酯胶黏剂的热老化动力学研究,在125～150℃温度范围内聚氨酯胶黏剂的老化降解反应为二级反应,与固化反应有相同的反应级数。分析结果说明,在线FT—IR方法能直接反映高分子材料老化过程中的对应基团的变化,是老化机理研究的直接实验依据。该方法的建立为其他高分子材料老化机理和动力学的研究提供了有效的检测技术和试验装置。     

计算机辅助设计的产生和发展

介绍了计算机辅助设计的产生背景、发展过程及其应用场合。同时指出 ,我国的计算机辅助设计技术与国外先进水平尚有一段距离 ,建立计算机辅助设计系统时 ,应根据实际需要以及技术经济可行性来判断。     

The quantitative analysis of fluorocarbon polymer finishes on wool by FT-IR spectroscopy

Two contrasting infrared spectroscopic techniques, Attenuated Total Reflectance (ATR) and PhotoAcoustic Spectroscopy (PAS), have been investigated as means for the determination of fluorocarbon polymer finishes on wool fabric. Based on the experimental conditions used, the results of the PAS method are more characteristic of the bulk sample, while the ATR results are more surface specific. Linear calibrations between polymer addon, as determined by total fluorine analysis, and the absorbance of the C? F stretching bands of the normalized spectral data were obtained for a typical commercial fluorocarbon polymer. The correlation obtained for the PAS method was found to be significantly better than that of the ATR method. The lower limit of detection of fluorocarbon polymers on wool using the PAS technique was 0.25% on the weight of the wool (oww). In contrast, fluorocarbon polymer add-ons as low as 0.125% oww (approximating monolayer coverage) could be analyzed using the ATR method. At high levels of add-on, the ATR calibration deviated from linearity. This can be attributed to the distribution of fluorocarbon polymer on the surface of the fiber, in particular, the build up of polymer on the cuticle cell edge regions. The quantitative methods developed are used to help access the effects of wear and the subsequent heating of fluorocarbon polymer-treated fabric samples. © 1995 John Wiley & Sons, Inc.     

Enquiry based learning in chemical engineering curriculum supported by computer aided delivery

Traditional curriculum delivery in higher education has long been considered ineffective in promoting deep learning. Enquiry based learning (EBL) provides an opportunity to develop important professional attributes within the subject-specific content. Computer-aided learning packages can be a useful tool in supporting the development of these skills, as they enable students to explore and gain experience of new software environments in subject-specific context. The development of case studies delivered in Stages 1 and 2 of a chemical engineering degree programme, utilising a number of different software packages is described. The Stage 1 case study develops fundamental principles of chemical engineering whilst Stage 2 case studies concentrate on separation processes and the reactor engineering aspect at the same time requiring the application of the knowledge of statistics and design of experiments, respectively. Student evaluation via questionnaires, focus groups and comments from individual reflective reports, submitted as part of the assessment of the Stage 1 case study activity, demonstrate the impact of these case studies on student learning and their behaviour. Students consider these case studies useful in strengthening their knowledge of the relevant areas of chemical engineering as well as helping them develop skills they consider important from employability point of view.     

CAEv–A program for computer aided evaluation

The evaluation of new reagents and instruments in clinical chemistry leads to complex studies with large volumes of data, which are difficult to handle. This paper presents the design and development of a program that supports an evaluator in the definition of a study, the generation of data structures, communication with the instrument (analyser), online and offline data capture and in the processing of the results. The program is called CAEv, and it runs on a standard PC under MS-DOS. Version 1 of the program was tested in a multicentre instrument evaluation. The concept and the necessary hardware and software are discussed. In addition, requirements for instrument/host communication are given. The application of the laboratory part of CAEv is described from the user''s point of view. The design of the program allows users a high degree of flexibility in defining their own standards with regard to study protocol, and/or experiments, without loss of performance. CAEv''s main advantages are a pre-programmed study protocol, easy handling of large volumes of data, an immediate validation of the experimental results and the statistical evaluation of the data.     

Photo- and thermal-oxidation of the nonwoven polypropylene fabric studied by FT-IR photoacoustic spectroscopy

The photo- and thermal-oxidation of a nonwoven polypropylene fabric was investigated using Fourier transform infrared photoacoustic spectroscopy (FT-IR/PAS). The infrared spectroscopic data indicate that alcohol, peroxide, aldehyde, ketone, carboxylic acid, and anhydride were formed as the products of the thermal oxidation and photooxidation of the polypropylene fabric. Ester was also formed during the thermal oxidation process. The thermal oxidation was accelerated after an initiation period. It was found that thermal oxidation occurred homogeneously between the surfaces of the fabric and its bulk. For the polypropylene fabric irradiated by ultraviolet (UV) radiation, however, the highest degree of oxidation occurred in the surface of the fabric facing the UV radiation source. It was also found that the UV radiation at 254 nm caused photooxidation of polyropylene. No photooxidation was observed in the fabric exposed to the UV radiation at 350 nm under the same conditions. © 1994 John Wiley & Sons, Inc.     

Microstructure determination of the acrylonitrile–styrene–methyl methacrylate terpolymers by NMR spectroscopy

Acrylonitrile–styrene–methyl methacrylate (A–S–M) terpolymers were prepared by photopolymerization using uranyl nitrate ions as photo initiators, which were analyzed by NMR spectroscopy. The terpolymer compositions were determined by Goldfinger's equation using comonomer reactivity ratios: r_as = 0.04; r_sa = 0.31; r_am = 0.17, r_ma = 1.45; r_sm = 0.52; r_ms = 0.47. The terpolymer compositions were also determined from the quantitative ¹³C(¹H)‐NMR spectroscopy. The sequence distribution of the acrylonitrile‐, styrene‐, and methyl methacrylate–centered triads were determined from the ¹³C(¹H)‐NMR spectra of the terpolymers and are in good agreement with triad concentrations calculated from the statistical model. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 3026–3032, 1999     

Influence of the surface properties of concrete on the adhesion of coating: Characterization of the interface by peel test and FT-IR spectroscopy

The understanding of the adhesion between protective coating and concrete is essential to ensure the aesthetic of buildings. Polyurea (PU) based coating are mainly deposited on the surface of concrete, several days after demoulding. However, their adhesion on concrete depends on different interlinked parameters. This study is based on the development of specific peel tests. A strengthened and porous membrane is introduced into the layer of liquid coating before its crosslinking. This methodology ensures a reproducible debonding of the coating/concrete system to measure the fracture energy. The fracture loci are then characterized by Fourier Transformed Infra-Red (FT-IR) spectroscopy. Results show that humid conditions of curing and long-term ageing strongly decrease the adhesion of coating. This weak adhesion is related to the presence of large crystals of portlandite, the growth of efflorescence or the kinetics of carbonation that could close the porosity or induce a weak interface. The type of the mould is also significant because it could induce the tearing of the extreme surface of concrete during demoulding. This tearing increases the roughness and the open porosity that enhances the fracture energy. Finally, this study demonstrates that the adhesion of PU coating is mainly conditioned by the mechanical anchorage at the surface of concrete.     

Characterization of LLDPE/LLDPE-g-AA Blends by Contact Angle and FT-IR Methods

Abstract

Blends of linear low density polyethylene (LLDPE) and linear low density polyethylene-grafted-acrylic acid (LLDPE-g-AA) were prepared by melt mixing. The surface of films with different content LLDPE-g-AA were characterized through contact angle measurements and FT-IR spectroscopy. The contact angles of water and glycerol on films surfaces of LLDPE/LLDPE-g-AA blends decrease with increase of LLDPE-g-AA. From FT-IR spectra of the blends, the carbonyl peak strength on the films surface was calculated. It was found that larger the carbonyl peak strength, the lower the value contact angle for LLDPE/LLDPE-g-AA blends.     

Fracture toughness of acrylonitrile-butadiene-styrene by J-integral methods

The fracture toughness of acrylonitrile-butadiene-styrene (ABS) was determined by three J-integral methods, ASTM E813-81, E813-87, and by hysteresis. The critical J values (J_1c) obtained are fairly independent of the specimen thickness, ranging from 10 to 15 mm. ASTM E813-81 and hysteresis methods result in comparable J_1c values, whereas the ASTM E813-87 was ～40% to 50% higher. The critical displacement determined from the plots of hysteresis (energy or ratio) and the true crack grow length vs. displacement are close. This indicates the critical displacement determined by the hysteresis method is indeed the displacement at onset of crack initiation, and the corresponding J_1c represents a physical event of crack initiation. The elastic storage energy. The input energy minus the hysteresis energy, is the most important factor in determining the onset of crack initiation. The critical elastic storage energy (at the beginning of crack growth) was found close to the J_1c obtained from the E813-81 or the hysteresis method.     

A computer aided methodology for the design of decentralized controllers

The use of decentralized controller is justified if tuning is simplified and the resulting control system is failure tolerant. The ability to satisfy these criteria with a given plant depends, in turn, on the choices of control structure and tuning parameters. Interaction Measures (IM's) are analysis tools which aid the designer in addressing each of these choices in a rigorous, quantitative manner. This communication presents a synopsis of existing IM's and shows how these can form the basis of a computer aided methodology for the design of decentralized controllers.     

Characterization by solid state V NMR spectroscopy

The fresh catalyst V₂O₅–WO₃/TiO₂ and catalyst used in SCR for 9000 h have been studied by the solid state ⁵¹V NMR spectroscopy in static and MAS conditions. According to ⁵¹V NMR in both samples the majority of vanadium sites are in a distorted octahedral environment similar to that in V₂O₅. There is a strong interaction between vanadium oxide and the support, but the concentration of vanadium atoms strongly bound to the surface is very small and can be detected only in MAS NMR experiments or after removing the excess of V₂O₅. There is no influence of WO₃ additives on the structure of the particles of V₂O₅, whereas the influence on the structure of strongly bounded V cannot be excluded. Combination of static (wide line) and MAS NMR techniques permit the characterization of not only the structure of the vanadium species but also small changes in their local environment. Hence these experiments show that there are some distortions of the local environment of vanadium sites of the vanadium oxide particles compared with the polycrystalline V₂O₅; treatment by SCR increases these distortions.     

Characterization and FT-IR study of nanostructured alumina-supported V-Mo-W-O catalysts

The effect of tungsten incorporation in the surface composition and its catalytic performance is evaluated for alumina supported Mo-V-O, Mo-W-O, V-W-O and Mo-V-W-O nanostructurated-oxide catalysts. The characterization results reveal that the surface of Mo-V-W-O catalysts is further different from the binary counterparts, due to the presence of stabilized and reduced structures dispersed on the support. Such species are not present in the Mo-V-O catalysts; indicative that tungsten acts as a structural–chemical promoter. The in situ FT-IR study of these catalysts under propane + oxygen atmosphere showed that Mo-V-W-O catalyst is able to thermally activate the propane oxotransformation and ODH-products are registered in the gas-phase whereas oxygenate-compounds are detected on the surface of catalysts.