Fourier Transfer Infrared Spectra Research Articles

Effects of processing and gamma radiation on mechanical properties and organic composition of frozen, freeze-dried and demineralised human cortical bone allograft.

Bone processing and radiation were reported to influence mechanical properties of cortical bones due in part to structural changes and denaturation of collagen composition. This comparative study was to determine effects of bone processing on mechanical properties and organic composition, and to what extent the radiation damaging after each processing. Human femur cortical bones were processed by freezing, freeze-drying and demineralisation and then gamma irradiated at 5, 15, 20, 25 and 50kGy. In the compression test, freeze drying significantly decreased the Young's Modulus by 15%, while demineralisation reduced further by 90% (P < 0.05) when compared to the freezing. Only demineralisation significantly reduced ultimate strength of bone by 93% (P < 0.05). In the bending test, both freeze drying and demineralisation significantly reduced the ultimate strength and the work to failure. Radiation at 25kGy showed no effect on compression for ultimate strength in each processing group. However, high dose of 50kGy significantly reduced bending ultimate strength by 47% in demineralisation group. Alterations in collagen in bones irradiated at 25 and 50kGy showed by the highest peak of the amide I collagen in the Fourier Transfer Infra-Red spectra indicating more collagen was exposed after calcium was removed in the demineralised bone, however radiation showed no effect on the collagen crosslink. The study confirmed that demineralisation further reduced the ability to resist deformation in response to an applied force in freeze-dried bones due to calcium reduction and collagen composition. Sterilisation dose of 25kGy has no effect on mechanical properties and collagen composition of the processed human cortical bone.

Theoretical Interpretation of Polarized Light-Induced Supramolecular Orientation on the Basis of Normal Mode Analysis of Azobenzene as Hybrid Materials in PMMA with Chiral Schiff Base Ni(II), Cu(II), and Zn(II) Complexes

We have prepared hybrid materials of azobenzene and chiral Schiff base Ni(II), Cu(II), and Zn(II) complexes and investigated their linearly or circularly polarized UV (ultraviolet) light-induced supramolecular orientation with polarized electronic and IR spectra or CD (circular dichroism) spectra. The experimental FT-IR (Fourier transfer-infrared) spectra of azobenzene molecules were recorded at room temperature, and the results were compared with quantum chemical theoretical values using B3LYP, M052X, and M062X DFT (density functional theory) methods. The interaction of azobenzene with PMMA was simulated. Molecular geometry, vibrational wavenumbers, and thermodynamic parameters were calculated in all these systems. With the help of specific scaling procedures for the computed wavenumbers, the experimentally observed FT-IR bands were analyzed and assigned to different normal modes of the molecule. Most modes had wavenumbers in the expected range, and the error obtained was in general very low. Several general conclusions were deduced.

Effect of FeCl3 on the morphology, wetting behavior, and stabilization/carbonization of polyacrylonitrile nanofibers prepared by electrospinning

AbstractHerein we report that the neat polyacrylonitrile (PAN) nanofibers and PAN/FeCl3 composite nanofibers were prepared by the materials-processing technique of electrospinning. The effect of FeCl3 amount on the morphology and wetting behavior of the resulting composite nanofibers were studied by scanning electron microscopy (SEM) and drop shape analysis (DSA), respectively. The SEM images indicated that the diameters of composite nanofibers decreased with increase of FeCl3 amount, and this was probably due to the conductivity increase of spinning solutions. The results acquired from DSA measurement showed that the addition of FeCl3 increased the surface contact angle of water deposited on composite nanofibers, suggesting the higher hydrophobicity and the lower wetting behavior. Additionally, the effect of FeCl3 on stabilization and carbonization of the PAN composite nanofibers were investigated. The structural and morphological evolutions of the stabilized and carbonized nanofibers were studied by Fourier transfer infrared (FTIR) spectra and SEM. The FTIR spectra showed that the presence of FeCl3 in composite nanofibers considerably varied the mechanisms of thermo-chemical reactions during the heat treatments. The SEM images revealed that there were conglutinations of nanofibers after carbonization, while the degree of conglutination for the carbonized PAN composite nanofibers with FeCl3 was higher than that for the carbonized neat PAN nanofibers.

Remote H2/N2 plasma processes for simultaneous preparation of low-k interlayer dielectric and interconnect copper surfaces

This study focuses on the simultaneous plasma treatment of interlayer dielectric (ILD) and chemical mechanical polished (CMP) Cu surfaces using N2/H2 plasma processes. The modifications induced by the gas chemistries are investigated for two ILD films with different porosities and carbon concentrations. H atoms and radicals in the plasma react with the carbon groups leading to carbon removal for both of the ILD films. Fourier transfer infrared (FTIR) spectra show a greater fractional reduction of CH3 in the high porosity ILD compared to the low porosity ILD. Results indicate that an N2 plasma forms an amidelike layer on the surface, which apparently leads to reduced carbon abstraction from an H plasma process. In addition, FTIR spectra indicate the formation of hydroxyl (SiOH) groups following the plasma exposure. Increased temperature (380 °C) processing leads to a reduction of the hydroxyl group formation compared to ambient temperature processes, and the dielectric constant is increased by a smaller amount. It appears that the increase of the dielectric constant is mainly attributed to moisture uptake rather than network topography change due to carbon loss. The plasma experiments were repeated with CMP Cu surfaces at both ambient temperature and 380 °C. The carbonate contamination was removed by an H2 plasma process at elevated temperature while the CC and CH contamination was removed by an N2 plasma process at elevated temperature.

The synthesis of SiCON ceramics through precursor method

AbstractA polymeric precursor, polysiloxazane (PSON), for SiCON ceramics has been synthesized by the partial hydrolysis of MeViSiCl2, MeHSiCl2, and MeSiCl3 followed by ammonolysis reaction of the hydrolyzed intermediates with NH3. The structure and thermal properties of the polymeric precursor were investigated by means of Fourier transfer infrared spectra (FTIR), 1H‐NMR, 29Si‐NMR, gel permeation chromatography, and thermogravimetric analysis. The structure of the SiCON ceramics derived from the pyrolysis of PSON was characterized by FTIR and X‐ray diffraction. The as‐synthesized PSON produced mainly α‐Si3N4 crystalline phase during pyrolysis at 1500°C under N2 atmosphere, whereas when pyrolyzed at 1500°C under Ar atmosphere, crystalline phases of α/β‐SiC and/or α‐Si3N4 were detected. © 2012 Wiley Periodicals, Inc. J fAppl Polym Sci, 2012

Photocrosslinking and related properties of intumescent flame‐retardant LLDPE/EVA/IFR blends

The photoinitiated crosslinking of halogen‐free flame retarded linear low density polyethylene/poly(ethylene‐co‐vinyl acetate) blends (LLDPE/EVA) with the intumescent flame retardant (IFR) of phosphorous‐nitrogen compound (NP) in the presence of photoinitiator and crosslinker and their characterization of related properties have been investigated by gel determination, heat extension test, cone calorimeter test (CCT), thermogravimetric analysis (TGA), Fourier transfer infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), mechanical properties measurements, limiting oxygen index (LOI), UL‐94, and water resistance test. The data from the gel content and heat extension rate (HER) show that the LLDPE/EVA/IFR blends filled with NP are readily crosslinked to a gel content of above 75% and the HER values reach about 50% by UV‐irradiation of 5 sec under suitable amount of photoinitiator and crosslinker. The data obtained from the CCT and LOI indicate that photocrosslinking can considerably decrease the heat release rates (HRR) by 10–15%, prolongate the combustion time, and increase two LOI values for the LLDPE/EVA/NP blends UV irradiated for 5 sec. The results from TGA and the dynamic FTIR spectra give the evidence that the photocrosslinked LLDPE/EVA/NP samples show slower thermal degradation rate and higher thermo‐oxidative degradation temperature than the uncrosslinked LLDPE/EVA/NP samples. The morphological structures of charred residues observed by SEM give the positive evidence that the compact charred layers formed from the photocrosslinked LLDPE/EVA/NP samples play an important role in the enhancement of flame retardant and thermal properties. The data from the mechanical tests and water‐resistant measurements show that photocrosslinking can considerably improve the mechanical and water‐resistant properties of LLDPE/EVA/NP samples. Copyright © 2011 John Wiley &amp; Sons, Ltd.

Effects of silane on the properties of wood‐plastic composites with polyethylene‐polypropylene blends as matrices

AbstractThe influence of 3‐(trimethoxysilyl)propyl methacrylate and benzoyl peroxide on gel content, crystallinity, and mechanical performance of unfilled PP‐PE blends, and their composites with wood was investigated. All materials were compounded in a twin screw extruder and then injection molded. Specimens were then exposed to high‐humidity and elevated temperature in a humidity chamber to cross‐link any unhydrolyzed silane.Adding wood to the PE‐PP blends, increased premature cross‐linking but also increased gel contents. However, the gel contents of the composites were still low. The PP component did not appear to cross‐link well and our gels were almost entirely HDPE. Fourier Transfer Infrared (FTIR) spectra provided additional evidence that TMSPM is grafted and cross‐linked in unfilled PE‐PP blends. Unfortunately, the spectra of wood composites proved difficult to interpret because of the complexity and overlap of the FTIR spectra of the wood. The HDPE component annealed when exposed to high‐humidity and elevated temperature, although less so in samples with high‐gel contents, presumably because of the decreased mobility. Annealing influenced mechanical performance, especially increasing moduli. Adding peroxide and silane appeared to improve adhesion between the wood flour and matrix in the composites but had little effect on energy absorbed during high‐speed puncture tests. Published 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Synergistic effects of fumed silica on intumescent flame‐retardant polypropylene

AbstractThe synergistic effects of fumed silica on the thermal and flame‐retardant properties of intumescent flame retardant (IFR) polypropylene based on the NP phosphorus‐nitrogen compound have been studied by Fourier transfer infrared (FTIR) spectroscopy, cone calorimeter test (CCT), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), limiting oxygen index (LOI), and UL‐94 tests. The LOI and UL‐94 data show that when ≤1 wt % fumed silica substituted for the IFR additive NP can increase 2 to 4% LOI values of the PP blends and keep the V‐0 rating. The data obtained from the CCT tests indicate the heat release rates (HRR) reduce by about 23% for the PP/NP sample with 0.5 wt % fumed silica, whereas the mass loss rates (MLR) and total heat release (THR) values are much lower than those of the PP/NP samples without fume silica. The TGA data demonstrate that a suitable amount of fumed silica can increase the thermal stability and charred residue of the PP/IFR/SiO2 blends after 500°C. The morphological structures of charred residues observed by SEM give positive evidence that a suitable amount of fumed silica can promote the formation of compact intumescent charred layers and prevent the charred layers from cracking, which effectively protects the underlying polymer from burning. The dynamic FTIR spectra reveal that the synergistic flame‐retardant mechanism of a suitable amount of fumed silica with IFR additive is due to its physical process in the condensed phases. However, a high loading of fumed silica restricts the formation of charred layers with POP and POC complexes formed from burning of polymer materials and destroys the swelling behavior of intumescent charred layers, which deteriorates the flame retardant and thermal properties of the PP/IFR blends. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Two step modification of poly(vinyl alcohol) by UV radiation with 2-hydroxy ethyl methacrylate and sol–gel process for the application of polymer electrolyte membrane

Two step modification of poly(vinyl alcohol) (PVA) by UV radiation and sol–gel process was used to prepare the modified PVA membranes. From the first step modification of PVA by UV radiation with 2-hydroxy ethyl methacrylate (HEMA) monomer, the poly(2-hydroxy ethyl methacrylate) (PHEMA) modified poly(vinyl alcohol), PVAHEMA, was obtained and characterized by Fourier transfer infrared spectra (FTIR) and optical polarizing microscopy for the chemical compositions and morphology. With the second step modification of sol–gel process, the organic–inorganic hybrid sol–gel material, PVAHEMA–SiO 2, was prepared. Both of the modified PVA, (PVAHEMA and PVAHEMA–SiO 2), were characterized by X-ray diffraction (XRD), differential scanning calorimetry (DSC), and thermogravimetry analysis (TGA). To prepare the alkaline solid polymer electrolyte, the various PVAHEMA and PVAHEMA–SiO 2 membranes were immersed in 40 wt% KOH solution to form the KOH containing polymer electrolyte membranes. And then their performances were conducted with ac impedance spectroscopy to evaluate the ionic conductivity through the membranes. At room temperature, the ionic conductivity increased from 0.044 to 0.073 S/cm for the PVAHEMA membrane; whereas the ionic conductivity was about 0.11 S/cm for the PVAHEMA–SiO 2 membranes. Compared to other reports in references, our hybrid sol–gel membrane is a highly ionic conducting alkaline solid polymer electrolytes membrane.

Simultaneous formation of silicon carbide and diamond on Si substrates by microwave plasma assisted chemical vapor deposition

The effects of several process parameters, such as substrate temperature, nucleation density, and substrate surface pretreatment, on the simultaneous formation of SiC and diamond under typical growth conditions of diamond by microwave plasma assisted chemical vapor deposition (MPCVD), have been investigated by scanning electron microscopy (SEM), X-ray diffraction, and Raman and Fourier-transfer infrared (FTIR) spectroscopy. Results show that no SiC can be detected in the diamond films grown with a high nucleation density, whereas, SiC is detected in the thick diamond films grown with a low nucleation density, with or without surface pretreatment of the Si substrates. SEM micrographs and FTIR spectra illustrate that SiC is formed on the Si substrate not covered by diamond nuclei or in void regions between diamond nuclei. The formation of SiC and diamond on Si substrates under the growth conditions of diamond by MPCVD is a concurrent competitive deposition process, especially at the initial stage of diamond nucleation and growth. This is an alternative method for the synthesis of diamond-SiC composites by MPCVD.

Flammability characteristics and flame retardant mechanism of phosphate-intercalated hydrotalcite in halogen-free flame retardant EVA blends

The flammability characteristics and flame retardant mechanism of phosphate-intercalated hydrotalcite (MgAl-PO 4) in the halogen-free flame retardant ethylene vinyl acetate (EVA) blends have been studied by X-ray diffraction (XRD), Fourier transfer infrared (FTIR) spectroscopy, cone calorimeter test (CCT), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), limiting oxygen index (LOI) and UL-94 tests. The results show that the hydrotalcite MgAl-PO 4 intercalated by phosphate possesses the enhanced thermal stability and flame retardant properties compared with ordinary carbonate-intercalated hydrotalcite MgAl-CO 3 in the EVA blends. The CCT tests indicate that the heat release rate (HRR) and mass loss rate (MLR) values of the EVA/MgAl-PO 4 samples are much lower than those of the EVA/MgAl-CO 3 samples. The TGA data show that the thermal degradation rates of MgAl-PO 4 and EVA/MgAl-PO 4 samples are much slower and leave more charred residues than those of MgAl-CO 3 and its corresponding EVA blends. The LOI values of EVA/MgAl-PO 4 samples are 2% higher than those of the corresponding EVA/MgAl-CO 3 samples at the range of 40–60 wt% loadings, while the EVA sample with 55 wt% MgAl-PO 4 can reach the UL-94 V-1 rating. The dynamic FTIR spectra reveal that the flame retardant mechanism of MgAl-PO 4 can be ascribed to its catalysis degradation of the EVA resin, which promotes the formation of charred layers with the P–O–P and P–O–C complexes in the condensed phase. The SEM observations give further evidence of this mechanism that the compact charred layers formed from the EVA/MgAl-PO 4 sample effectively protect the underlying polymer from burning.

Hydrothermal synthesis, characterization and its photoactivity of CdS/Rectorite nanocomposites

CdS/Rectorite nanocomposites were prepared through hydrothermal method by using Cd[NH 2CSNH 2] 2Ac 2 complex as precursor of CdS which was derived from cadmium acetate and thiourea. The obtained nanocomposites were characterized by X-ray diffraction (XRD), Fourier transfer infrared spectra (FTIR), diffusion reflection spectra (DRS), transmission electron microscopy (TEM) and the selected area electron diffraction (SAED) patterns. Experimental results indicate that CdS exist in at least three forms: CdS adsorbed at surface, CdS pillared in montmorillonite-like layers of Rectorite and CdS pillared in the new layered structure formed during the hydrothermal process. Those CdS crystals are hexagonal symmetry. The photoactivity and photostability of the obtained CdS/Rectorite nanocomposites are improved significantly compared to that of the reference Rectorite and pure CdS.

Interaction of rofecoxib with human serum albumin: Determination of binding constants and the binding site by spectroscopic methods

The interaction of rofecoxib with human serum albumin (HSA) under physiological condition was investigated by fluorescence, UV–vis absorbance and Fourier transfer infrared (FT-IR) spectroscopy. Fluorescence data revealed that the fluorescence quenching of HSA by rofecoxib was the result of the formed complex of HSA–rofecoxib, and the site binding constants ( K a) were 4.840 × 10 4, 3.450 × 10 4, and 2.325 × 10 4 M −1 at 298, 304, and 310 K, respectively. The thermodynamic parameters, enthalpy change (Δ H) and entropy change (Δ S) for the reaction were calculated to be −46.90 kJ mol −1 and −67.59 J mol −1 K −1 according to van’t Hoff equation. The spectroscopic measurements and the thermodynamic parameters suggested that van der Waals interaction and hydrogen bonds were the predominant intermolecular forces to stabilize the complex. The distance r = 5.1 nm between donor (Trp 214) and accepter (rofecoxib) was obtained according to the Förster theory of non-radiative energy transfer. FT-IR spectra and UV–vis absorbance showed that the change of protein secondary structures resulted from the rofecoxib binding to several amino acids on the hydrophobic pocket of HSA. Furthermore, it is observed from the probe of competitive experiments that the binding location of rofecoxib with HSA could be the same as the warfarin site I of HSA, which was also revealed by fluorescence anisotropy.

Structure characteristics and thermal properties of silane-grafted-polyethylene/clay nanocomposite prepared by reactive extrusion

Silane-grafted-polyethylene/OMT nanocomposite (VTMS-g-PE/OMT) was prepared by reactive extrusion from linear low density polyethylene (LLDPE), vinyltrimethoxysilane (VTMS), organically modified montmorillonite (OMT) and dicumyl peroxide (DCP). A series of tests such as X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transfer infrared (FTIR) and thermogravimetric analysis (TGA) have been performed to characterize the morphology and thermal properties of the graft polymer and its nanocomposite. Results show that the graft polymer (VTMS-g-PE) chains have been successfully intercalated into OMT layers proved by XRD data (a d-spacing of 3.4 nm) and TEM images; the PE chains have been chemically bounded to the OMT layers proved by FTIR spectra; the nanocomposite exhibits a higher thermal-oxidative stability than that of either the VTMS-grafted-LLDPE or the LLDPE proved by TGA curves. The increase in thermal properties lies in two facts: one is the formation of chemical bonds between PE macromolecules and OMT layers during silane graft reaction; the other is the in situ graft of PE macromolecules onto the OMT surfaces during thermal-oxidative degradation.

Preparation and thermal characteristics of silane-grafted polyethylene/montmorillonite nanocomposites

Intercalated methacryloylpropyltrimethoxysilane (VMMS)-grafted polyethylene (PE-g-VMMS) /organo-montmorillonite (OMT) nanocomposite was prepared by melt intercalation. Its morphology and thermal characteristics were carried out by X-ray diffraction (XRD), transmission electron microscopy (TEM), thermogravimetric analyses (TGA) and dynamic Fourier transfer infrared (FTIR) spectroscopy. The intercalated tactoids of silicate layers within PE-g-VMMS have been verified by XRD and TEM image. TGA profiles of the nanocomposite show that the presence of the silicates exerts a significant stabilization effect on thermal-oxidative degradation process from 250 to 375°C, but less effect above 375°C. Dynamic FTIR spectra reveal that this nanocomposite has a slower thermal-oxidative degradation rate of main chains than that of pure PE-g-VMMS, but a faster rate of the pendant VMMS grafts.

Structural Characteristics and Thermal Properties of PE-g-MA/MgAl-LDH Exfoliation Nanocomposites Synthesized by Solution Intercalation

Exfoliated nanocomposites (PE-g-MA/MgAl-LDH) were synthesized by solution intercalation of polyethylene-grafted-maleic anhydride (PE-g-MA) into the galleries of organo-modified MgAl layered double hydroxide (OMgAl-LDH) under reflux in xylene. Their structural elucidation and thermal characterization were carried out by X-ray diffraction (XRD), Fourier transfer infrared (FTIR) spectroscopy, transmission electron microscopy (TEM), selected area electron diffraction (SAED), thermogravimetric analysis (TGA), and differential thermal analysis (DTA). The molecular dispersion of OMgAl-LDH layers within the PE-g-MA matrix has been verified by the disappearance of d001 XRD diffraction peak of OMgAl-LDH and the observation of TEM image. The OMgAl-LDH layers of about 70-nm length or width show a disordered phase in PE-g-MA matrix. The SAED pattern demonstrates that the MgAl hydroxide sheets of about 0.48-nm thickness have a hexagonal crystal structure with a = 0.305 nm. TGA profiles of the PE-g-MA/MgAl-LDH nanocomposites show a faster charring process in temperature range from 210 to 360 °C and greater thermal stability above 370 °C than PE-g-MA. The decomposition temperature of the nanocomposites with 5 wt % OMgAl-LDH can be 60 °C higher than that of PE-g-MA when 50% weight loss was selected as a measuring point. Dynamic FTIR spectra reveal that this nanocomposite has a slower thermo-oxidative rate than PE-g-MA from 200 °C to 320 °C. This kind of exfoliation nanocomposite is promising for use in flame-retardant polymeric materials.