Qualitative spectroscopic characterization of the matrix-silane coupling agent interface across metal fibre reinforced ion exchange resin composite membranes

The characterization of novel metal reinforced electro-dialysis ion exchange membranes, for water desalination, by attenuated total reflectance Fourier transform infrared spectroscopy mapping is presented in this paper. The surface of the porous stainless steel fibre meshes was treated in order to enhance the amount of surface oxide groups and increase the material hydrophilicity. Then, the metal membranes were functionalized through a sol-gel reaction with silane coupling agents to enhance the affinity with the ion exchange resins and avoid premature metal oxidation due to redox reactions at the metal-polymer interface. Polished cross sections of the composite membranes embedded into an epoxy resin revealed interfaces between metallic frameworks and the silane layer at the interface with the ion exchange material. The morphology of the metal-polymer interface was investigated with scanning electron microscopy and Fourier transform infrared micro-spectroscopy. Fourier transform infrared mapping of the interfaces was performed using the attenuated total reflectance mode on the polished cross-sections at the Australian Synchrotron. The nature of the interface between the metal framework and the ion exchange resin was shown to be homogeneous and the coating thickness was found to be around 1 μm determined by Fourier transform infrared micro-spectroscopy mapping. The impact of the coating on the properties of the membranes and their potential for water desalination by electro-dialysis are also discussed.

Acid induced degradation of the bentonite component used in geosynthetic clay liners

Bentonite is a natural clay mineral widely used in the mining and solid waste containment industry, for example, as a soil mixture for the construction of seepage barriers, or as a component of geosynthetic clay liners (GCLs), to provide low hydraulic conductivity. However, degradation of bentonites generally occurs when permeated with acid solutions, such as encountered in mining applications, which may influence physical properties, and particularly, the hydraulic performance of geosynthetic clay liners.In this paper, properties such as Atterberg limits, free swell index, and fluid loss of three bentonites were measured with different concentrations of sulphuric acid solutions. These properties were found to deteriorate even with low (0.015 M) sulphuric acid solutions; higher concentrations (up to 1 M) resulted in larger degradation. X-ray diffraction and infrared spectroscopy were used to monitor the change of bentonites after interaction with the acid solutions. Acid leachates in general result in the overall degradation of the hydraulic performance of geosynthetic clay liners and potentially, any bentonite-soil mixture.

Bond length dependence on quantum states as shown by spectroscopy

Undergraduate students often have the misconception that molecules have fixed, unchanging bond lengths. This article discusses how linear-molecule rotational band spacings in infrared spectroscopy can be used as a qualitative, visual demonstration of the elongation of average bond lengths on vibrational excitation. The method does not depend on a detailed mathematical analysis of the spectra. In UV–vis spectroscopy, the rotational band spacings give rise to distinctive linear-molecule rotational contours, which easily show whether the average bond length has increased or decreased. The method is based on a spreadsheet simulation of the vibration–rotation or rovibronic (electronic–vibration–rotation) spectrum and is applied to hydrogen chloride IR, iodine UV–vis, and nitrogen UV–vis spectra in this article.

Quantifying rubber degradation using NMR

Ageing can lead to the degradation of the tensile properties of natural rubber. The ageing process causes changes in the polymer segmental motion as well as the chemical structure, both of which can be monitored using nuclear magnetic resonance (NMR) spectroscopy. This work demonstrates that NMR can quantify rubber degradation due to ageing, and also that relatively simple NMR equipment can be used. This simpler equipment can be made portable and so could give a simple and fast indication of the condition of rubber in service. The 1H NMR transverse relaxation time, T2, and the 13C NMR spectrum using cross polarization and magic angle spinning (CP MAS) for samples taken at various levels of a degraded natural rubber liner were compared. These experiments showed that, as the level of degradation increased, the 1H NMR transverse relaxation time decreased. The 13C spectra showed considerable peak broadening, indicative of decreased mobility with increased level of degradation as well as the presence of degradation products. Further investigations using lower powered NMR equipment to measure the 1H NMR transverse relaxation times of two different series of natural rubbers were also performed. This work has shown that this simpler method is also sensitive to structural and mechanical property changes in the rubber. This method of monitoring rubber degradation could lead to the non-destructive use of NMR to determine the condition of a part in service.

Effect of aluminum on the corrosion resistance of low-alloy steel in 10wt% sulfuric acid solution

The aqueous corrosion behavior of low-alloy steel with aluminum contents was examined in a 10 wt% H₂SO₄ (pH 0.13) solution using electrochemical techniques and surface analyses. The corrosion resistance of the new alloy steel was evaluated in terms of electrochemical parameters, such as passive current density, film, and charge transfer resistances. The results showed that a high Al content in the steel imparted better passivation behavior resulting in a lower corrosion rate. It related to the enrichment of iron carbonate and hydrocarbon by the dissolution of the carbide phase.

Rapid discrimination and determination of polyunsaturated fatty acid composition in marine oils by FTIR Spectroscopy and Multivariate Data Analysis

A rapid analytical approach for discrimination and quantitative determination of polyunsaturated fatty acid (PUFA) contents, particularly eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), in a range of oils extracted from marine resources has been developed by using attenuated total reflection Fourier transform infrared spectroscopy and multivariate data analysis. The spectral data were collected without any sample preparation; thus, no chemical preparation was involved, but data were rather processed directly using the developed spectral analysis platform, making it fast, very cost effective, and suitable for routine use in various biotechnological and food research and related industries. Unsupervised pattern recognition techniques, including principal component analysis and unsupervised hierarchical cluster analysis, discriminated the marine oils into groups by correlating similarities and differences in their fatty acid (FA) compositions that corresponded well to the FA profiles obtained from traditional lipid analysis based on gas chromatography (GC). Furthermore, quantitative determination of unsaturated fatty acids, PUFAs, EPA and DHA, by partial least square regression analysis through which calibration models were optimized specifically for each targeted FA, was performed in both known marine oils and totally independent unknown n - 3 oil samples obtained from an actual commercial product in order to provide prospective testing of the developed models towards actual applications. The resultant predicted FAs were achieved at a good accuracy compared to their reference GC values as evidenced through (1) low root mean square error of prediction, (2) good coefficient of determination close to 1 (i.e., R 2≥ 0.96), and (3) the residual predictive deviation values that indicated the predictive power at good and higher levels for all the target FAs. © 2014 Springer Science+Business Media New York.

Transesterification induced mechanical properties enhancement of PLLA/PHBV bio-alloy

In order to improve the miscibility and mechanical properties of poly(l-lactic acid) (PLLA) and poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) bio-alloy, small amount of transesterification catalyst, zinc acetate was added in the melt blending process. We show that the PLLA-PHBV copolymer generated during the melt blending significantly improves the miscibility and therefore enhances the mechanical properties of the product. Dynamic mechanical analysis (DMA), scanning electron microscopy (SEM), and tensile tests were performed to study the miscibility and mechanical properties of the blends. Fourier transform infrared spectroscopy (FTIR) and gel permeation chromatography (GPC) were used to reveal the molecular structural, and molecular weight changes of PLLA and PHBV after melt mixing with zinc acetate. SEM and FTIR results have clearly shown that the PLLA-PHBV copolymer generated from transesterification reaction acted as a compatibilizer and therefore resulted in an improved interfacial miscibility and ductility of PLLA/PHBV blend. In our mechanistic study, a competition between the PLLA/PHBV transesterification reaction and the thermal decomposition of PHBV was identified for the first time. On the basis of these observations, a new mechanism of transesterification reaction was proposed.

Crystalline polymorph transition in poly(vinylidene fluoride) (PVDF)/acrylic rubber(ACM)/clay partially miscible hybrid

This study investigates the intercalation of nanoclay in partially miscible blends of poly(vinylidene fluoride) (PVDF) and acrylic rubber(ACM). Transmission electron microscopy and X-ray diffraction technique were used to investigate the formation of nanoscale polymer blend/clay hybrids. Using Infrared spectroscopy and X-ray analysis, the different polymorph formation in PVDF nanocomposite and conjugated phases of partially miscible nanocomposite was studied. Nanoclay was found to induce β and γ polymorphs while ACM tend to induce α phase in this polymer system. It was shown that PVDF chains in ACM-rich phase of partially miscible nanocomposites interact with ACM chains which in return form α polymorph in the presence of ACM. Further observations revealed that nanoclay in α polymorph is wrapped by ACM molecules.