A new method to monitor adhesion and interfacial failure between polymers: rheo-photoacoustic FT-IR spectroscopy

Recently, a new rheo-photoacoustic Fourier transform infra-red (IR) cell has been developed to perform stress-strain measurements on polymeric materials. This technique is now being utilized to monitor interfacial failure between organic coatings and polymeric substrates; namely the interfacial failure between siloxane-polyethylene and poly(methyl methacrylate)-polyethylene systems is studied. As a result of interfacial failure, the intensities of substrate bands are enhanced. Signal leakage results from the formation of microvoids, which are monitored by electron microscopy. Analysis of the IR spectra demonstrates frequency shifting in the siloxane-polyethylene system, indicating chemical interactions between the two materials at the interface.     

Copper(II) Extraction from Phosphoric Acid Media by 5‐Dodecylsalicylaldoxime (LIX 622)

Abstract

The extraction of Cu(II) from phosphoric acid media (0.4–7.3 M) by the commercial reagent LIX 622 in toluene has been studied. Experimental results have been treated numerically and the formation in the organic phase of the complex CuR₂, HR being 5‐dodecylsalicylaldoxime, has been proposed. Values of the conditional extraction constants, which increase with the phosphoric acid concentration, are given. Organic extracts have been analyzed by EPR spectroscopy. The presence of a square planar complex of Cu(II) has been deduced confirming the stoichiometry CuR₂.     

PAHs in Sediments Contaminated by the Haven Oil Spill. (Genoese Bay)

Sediment samples were collected 40 months after the wreckage of the HAVEN off shore Arenzano, facing the Genoese coast, at 300 to 500 m depth, (wreckage zone) and analysed by UV fluorescence spectroscopy and CG/MS. PAHs as alkylated naphtalene, fluorene, phenanthrene, dibenzothiophene series have been studied. Analytical results reveal – 1° – a great alteration of alkylated homologues compared to parent compounds - 2° - the appearance of anthracene (absent in the original crude oil) in samples – 3° – a relative increase of high molecular weight PAHs (4–5 rings and more) as benzo(ghi)perylene and indeno(cd)pyrene. These changes result from the partial burning of the contaminant oil. A beginning of biodegradation is observed for alkylated phenanthrenes.     

Room-Temperature Solid-Matrix Luminescence Spectroscopy of Pyrene and 1-Hydroxypyrene from Optically Clear Sugar Glasses

Room-temperature solid-matrix luminescence was investigated for two model compounds pyrene and 1-hydroxypyrene from optically clear sugar glasses. Several glasses were investigated. Novel glasses were prepared for the first time from binary mixtures of sugars for spectroscopy. Glasses were prepared from glucose/xylose and glucose/maltose. The glucose/maltose gave a superior glass compared to glucose/xylose. The glucose/maltose glass gave the best room temperature phosphorescence (RTP) for pyrene compared to glasses of glucose and maltose without a heavy atom. The RTP was weak for both pyrene and 1-hydroxypyrene without a heavy atom in the glucose glass. The addition of a heavy atom (12% NaI) gave a 44-fold increase in RTP of pyrene and a 10-fold increase in the RTP of 1-hydroxypyrene. Room temperature fluorescence (RTF) of pyrene and 1-hydroxypyrene were easily observed from all the glass systems studied. However, the pyrene RTF intensity varied with the different sugar glass systems studied. Furthermore, a polymer, polyacrylic acid (PAA), was added to the sugar matrix at the level of 1% and 2% to improve the rigidity of the glass matrix. The observed phosphorescence was weak for pyrene at both the 1% and 2% PAA concentrations. A glass prepared with 2% PAA gave the strongest RTP for pyrene. Addition of 12% NaI with 1% polyacrylic acid did improve the RTP of pyrene but it was less than the RTP of pyrene from a glucose glass with 12% NaI by a factor of 2.7. A glucose glass with 12% NaI was the best system for RTP of pyrene.     

Spectroscopic Studies of Model Photo-Receptors: Validation of a Nanosecond Time-Resolved Micro-Spectrophotometer Design Using Photoactive Yellow Protein and α-Phycoerythrocyanin

Time-resolved spectroscopic experiments have been performed with protein in solution and in crystalline form using a newly designed microspectrophotometer. The time-resolution of these experiments can be as good as two nanoseconds (ns), which is the minimal response time of the image intensifier used. With the current setup, the effective time-resolution is about seven ns, determined mainly by the pulse duration of the nanosecond laser. The amount of protein required is small, on the order of 100 nanograms. Bleaching, which is an undesirable effect common to photoreceptor proteins, is minimized by using a millisecond shutter to avoid extensive exposure to the probing light. We investigate two model photoreceptors, photoactive yellow protein (PYP), and α-phycoerythrocyanin (α-PEC), on different time scales and at different temperatures. Relaxation times obtained from kinetic time-series of difference absorption spectra collected from PYP are consistent with previous results. The comparison with these results validates the capability of this spectrophotometer to deliver high quality time-resolved absorption spectra.     

Enhanced conductivity of bacterial cellulose films reinforced with NH4I-doped graphene oxide

ABSTRACT

Bacterial cellulose (BC) films reinforced with reduced graphene oxide (RGO) platelets were investigated to assess their potential application as solid polymeric electrolytes. BC-RGO composites were further doped with NH₄I at different concentrations to evaluate the effect of NH₄I doping on the conductivity. Scanning electron microscopy images confirmed that GO addition did not alter BC coherent three-dimensional morphology. Electrochemical impedance spectroscopy studies revealed that the ionic conductivity increased with the ammonium iodide salt concentration. The highest conductivity found was 1.32 × 10^?4 S/cm for the samples doped with 5% NH₄I, suggesting that BC-RGO can be a promising candidate for electrochemical applications.     

Local Dynamics of Adhesives in Aggressive Environment in the Pre-Damage Stage

Molecular aspects of chemical and physical changes in adhesive joints caused by absorbed moisture were investigated. The focus was on the pre-damage stage that precedes the formation of voids and microcracks. A model and a commercial epoxy-amine formulation were studied. Local dynamics were monitored by broad-band dielectric relaxation spectroscopy (DRS). One portion of the absorbed water does not form hydrogen bonds with the network and gives rise to a fast relaxation process (termed γ) with activation energy of 28 kJ/mol. The local β dynamics are slowed down by the interactions between water and various sites on the network that include the ether oxygen, the hydroxyl group and the tertiary amine nitrogen. One particularly significant finding is that the average relaxation time for the β process above 20°C is of the order of nanoseconds or less and, hence, the detection and monitoring of this process hinges upon the ability to perform high-precision DRS at frequencies above 1 MHz. This is an important consideration in the ongoing efforts aimed at the implementation of DRS as nondestructive inspection (NDI) tool for adhesive joints.     

Bond Strength of a Silicone Soft Lining Material to Poly(methyl methacrylate) Resin Treated with Maleic Anhydride and its Terpolymers

This study investigated the effectiveness of surface treatment of Poly (methyl methacrylate) (PMMA) denture base resin on tensile bond strength between PMMA/silicone-based soft liner. A total of 25 specimens were fabricated and assigned into five groups (n = 5). The surfaces of PMMA were treated with maleic anhydride, maleic anhydride-styrene-vinyl-acetate, n-butylmaleate-styrene-vinyl-acetate, or n-pentamaleate-styrene-vinyl-acetate prior to Primo adhesive primer application and silicone liner placement. The Primo adhesive primer on applied group untreated dentuse base resin served as control. The tensile test was performed using a universal testing machine. Fractured surfaces were observed under Scanning Electron Microscopy (SEM) and spectroscopic interpretation of the interfaces was done by Fourier Transform Infrared (FTIR). Test results showed that surface treatment increased interfacial strength giving the highest value for n-butylmaleate-styrene-vinyl acetate treated group. SEM micrographs revealed that the specimens with n-butylmaleate-styrene-vinyl-acetate and n-penta maleate-styrene-vinyl-acetate terpolymers underwent cohesive failure. FTIR analysis indicated secondary interactions such as hydrogen bonding, possibly on acrylic resin surfaces, caused by the use of maleic anhydride and its terpolymers, and the adhesive.     

Thermal processing and properties of bioplastic sheets derived from meat and bone meal

Chemical modification of plasticized meat and bone meal (MBM) and its thermal processing into bioplastic sheets is reported. Specifically, MBM plasticized with 30 wt% glycerol and modified with calcium hydroxide (CH) (0, 3, 7, and 10 wt%) was batch compounded at 100°C, 15–30 min, and 60 rpm followed by thermal compaction at 140°C to produce sheets. The effect of CH content on the chemical structure, processability, and tensile properties (static and dynamic) of modified MBM sheets were studied. Fine particle size of MBM and moderate environment humidity produced well‐consolidated sheets. Increase in CH content to about 7 wt% was found to increase tensile strength and modulus, whereas the strain to failure decreased. Fourier transform infrared spectroscopy analysis of modified MBM sheets showed that the changes in mechanical properties could be attributed to increased interactions between protein chains, which were further aided by the precipitation of the fat portion of MBM. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013