Stretching Vibration Region Research Articles

Pressure-induced phase changes in natural fluorapophyllite-(K) studied by Raman spectroscopy

The high-pressure Raman spectra in the low-wavenumber region (50–1200 cm−1) and the hydroxyl stretching vibration region (2600–3800 cm−1) of fluorapophyllite-(K) were collected in the interval of 0.0–50.7 GPa. Experimental results show that fluorapophyllite-(K) undergoes a crystalline-crystalline phase transition from a tetragonal structure (P4/mnc) to an orthorhombic structure (Pnnm) and then amorphization under high pressure conditions. Discontinuous changes in Raman peaks in the hydroxyl vibration region (2600–3800 cm−1) and the low-wavenumber region (50–1200 cm−1) occur at different onset pressures, suggesting that the destabilization of sub-lattices in fluorapophyllite-(K) under high pressure is not synchronous; the weak interlayer H2O structural units are more prone to destabilization at lower pressures than the rigid SiO4 tetrahedral layer units. Therefore, H2O groups in fluorapophyllite-(K) serve as sensitive local probes during the pressure-induced phase transition and amorphization.

Application of Acid Activated Ouw’s Natural Clay (ONC) on Adsorption of Methylene Blue Dye

The application of natural clay as an adsorbent has been widely used. This is supported by the porous surface texture of the clay. However, some treatments are needed to remove impurities in natural clay before using it as an adsorbent. The common effort is to activate it with acid. This research studied the effect of hydrochloric acid concentration on the adsorption capacity of methylene blue dye. The concentrations of hydrochloric acid used were 2, 3, and 4 M. Characterization was carried out with IR, XRD, and SEM-EDX spectroscopy to see the differences in ONC characters before and after adding hydrochloric acid. The characterization results showed that ONC contained montmorillonite and quartz, and an increase in base distance was directly proportional to the increase in the concentration of hydrochloric acid used. High concentrations of hydrochloric acid caused excessive dealumination and deionization. The dealumination process was supported by IR data where there was a shift in wavenumber in the Al-O stretching vibration region from 796 cm–1 to 794 cm–1; the sharper the vibration in the Si-O region (488-468 cm–1); there was also an increase in the Si/Al ratio of pure ONC from 1.7497 to 2.2970 for 3 M ONC-HCl. The concentration of hydrochloric acid did not significantly affect the capacity of ONC as an adsorbent for methylene blue. The adsorption capacity of pure ONC obtained was 4.97215 mg/g, while for ONC-HCl 3 M was 4.97746 mg/g.

Raman spectroscopy investigations of hydrated hydroxypropyl cellulose mixtures with low-soluble salicylic acid: Molecular interactions and the water-binding structure

Highly hydrophilic polymer matrices are limited their in use to the delivery of hydrophilic drugs, and are ineffective for hydrophobic compounds. Therefore, studying hydrogels that can effectively deliver hydrophobic drugs is still an important challenge. The molecular interactions occurring in model hydrated binary mixtures of hydroxypropyl cellulose (HPC) and low-soluble and hydrophobic salicylic acid (SA) (1:1 w/w) were investigated by means of Raman spectroscopy. During the study, the OH stretching vibrations region (in the 3600–3100 cm−1 range) was examined and bands for the three assessed fractions of water were assigned at the wavenumbers 3400 cm−1 (non-freezing water), 3320 cm−1 (freezing bound water) and 3220 cm−1 (free water). The contribution of the OH vibrations of SA (3205 cm−1) was also considered. A significant area for the analysis of changes in the HPC polymer is the glycosidic linkage vibration region ranging from 1250 cm−1 to 1000 cm−1 (at ∼1151 cm−1 and at ∼1093 cm−1) and the 3000–2850 cm−1 region due to the CH stretching of the CH2 and CH3 groups. SA is able to form hydrogen bonds to polymer chains and to water, as well as to another SA molecule to form a dimer. Therefore, bands derived from SA were observed to monitor these interactions (in the 1600–1500 cm−1 range).The obtained results were discussed and partially compared to the corresponding previously published spectroscopic and theoretical outcomes. All observed interactions between the components of the mixture and water molecules were also analyzed as a function of time, which is a novel approach providing a large amount of valuable information about the system. The applied methodology allowed for establishing that the stabilization of the hydrated HPC/SA system took place after one week. The greatest dynamics of changes were observed for the lowest studied water concentration. For the highest water concentration, several low-intensity bands in the CO vibration range seemed to indicate dimer-type interactions.

Daytime radiative cooling capacity of nanoparticle on thermoplastic polyurethane (TPU) film

Radiative cooling, which does not entail any energy consumption, has received considerable attention as a promising, practical, and sustainable solution to heatwaves. This study investigated single layer nanoparticles–polymer films that reflected sunlight and emitted radiation through atmospheric windows. In this paper, the fundamental principles of Mie theory, the cooling power model, and the thermal balance model of metamaterial films were first introduced. Then, the influence of fabrication parameters (nanoparticle materials, mass fractions, and thicknesses) to the reflectivity in solar band was experimentally explained. An increase in the mass fraction enhanced the reflectivity corresponding to the stretching vibration regions of CH, NH, and OH, while an increase in the thickness improved the reflectivity at non-absorption bands. Laboratory measurements indicated that the combination of TiO2, a fluorescent brightener, and a far-infrared ceramic powder on 100 μm thermoplastic polyurethane film achieved excellent solar reflectivity of 92.2 % and infrared emissivity of 96.1 %. Experimental testing and Fluent simulation showed that the film achieved a substantial cooling capacity in both Beijing and Tianjin. Under a transparent atmospheric window, it exhibited a subambient temperature of 3.7 °C when the air temperature reached its peak. The maximum daytime and night-time subambient temperature were 13.4 °C and 14 °C respectively.

Composition Classification of Korea Ancient Glasses by Using Raman Spectroscopy

In this study, investigated the possibility of quantitatively and qualitatively analyzing Korean ancient glasses via Raman Spectroscopy. We subjected four categories of Korean traditional glasses, namely, lead-BaO, lead, potash, and soda glasses (3, 3, 10, and 10 pieces, respectively), to this analytical technique. The results showed significant differences between the stretching and bending Raman vibration regions corresponding to these different Korean ancient glass types. Specifically, the stretching vibration regions corresponding to lead-BaO and lead glasses showed peaks at 1040 and 1000 cm-1, respectively; the stretching vibration region of normal glass appears at 1100 cm-1. The bending vibration regions corresponding to potash and soda glass showed Raman peaks at 490 and 560 cm-1, respectively. Furthermore, the Raman spectra of the lead and lead-BaO glasses showed red shifts, which depended on the amount of PbO present. Thus, our findings highlighted the possibility of quantitatively determining the amount of PbO, a major component of lead glasses, via Raman Spectroscopy.

Ionic conductivity enhancement for PVA/ 20wt.% CuSO4 gel polymer electrolyte by using glycerin

Gel polymer electrolyte based on PVA+20wt.%CuSO4 was plasticized with (1,2 and 3) mL glycerin and prepared by casting method. Ionic conductivity for gel electrolytes enhancement occurs primarily as a result of increased carrier concentration and secondarily as a result of increased carrier mobility. Using X-ray diffraction (XRD) characterization, they observed that the glycerin-free electrolyte matrix has a regular arrangement with the crystalline phase. After adding glycerin, the observed orderly organization and crystalline phase fully transformed to amorphous. Fourier transform infrared spectroscopy (FTIR) result shows that the stretching vibration region of the O–H at 3261 cm−1 The hydrogen bonds formed by the hydroxyl groups of both PVA and glycerol structures explanation for the hydrophilic behavior of glycerol and the increased area. The new intense and strong peak that emerged at 2359.62 cm-1 is related to the aromatic Cu-O stretching of the salt CuSO4, The interaction of the PVA with the electrolyte elements increases its intensity with increasing glycerol.

Unraveling interfacial properties of organic-coated marine aerosol with lipase incorporation

Marine aerosols are believed to have an organic surface coating on which fatty acids act as an important component due to their high surface activity. In addition, various kinds of enzyme species are abundantly found in seawater, some of which have been identified to exist in marine aerosols. Herein, from the perspective of marine aerosol interface simulation, we investigate the effect of Burkholderia cepacia lipase on the surface properties of stearic acid (SA) monolayer at the air-water interface by using surface-sensitive techniques of Langmuir trough and Infrared reflection-absorption spectroscopy (IRRAS). Our findings indicate that the stearic acid film undergoes a significant expansion, especially when the lipase concentration is 500 nM, because of the incorporation of lipase as observed from the surface pressure-area (π-A) isotherms. IRRAS spectra also show reduced intensities and ordering in the methylene stretching vibration region of stearic acid as a result of low surface density and disordered packing as the enzyme concentration increases. In particular, when the concentration of lipase is 500 nM, the lowest Ias/Is values are shown on both pure water subphase and artificial seawater subphase, indicating more gauche conformations for SA. Furthermore, SA films with lipase incorporation were also studied at three different pH of subphase environment, considering the decrease of pH caused by the reaction with acidic gases during the aerosol aging process. The results reflect a more pronounced expansion of SA monolayer in acidic environment at pH 2.5, suggesting that hydrophobic interaction plays an important role in the disorder of the SA monolayer. In view of the coexistence of fatty acids and enzymes in the marine environment, this study provides a further understanding of the surface organization and behavior of organic-coated marine aerosols and deepen the knowledge of lipid-enzyme interfacial interactions occurring in the atmosphere.

Time series Fourier transform infrared spectroscopy for characterization of water vapor sorption in hydrophilic and hydrophobic polymeric films

This work investigates the nature of the molecular interactions between water vapor and polymers using time series Fourier transform infrared (FTIR) spectroscopy. A detailed analysis of the frequency shifts and relative peak intensities led to the conclusion that polyvinyl alcohol (PVOH) sorbed a large quantity of water vapor molecules, resulting in swelling and dissolving of polymer crystallites. Difference spectra were calculated to investigate spectral changes occurring upon sorption by dividing the spectra of polymers during the sorption time series by the spectrum of the dry sample and subsequently subtracting the water vapor spectrum. Based on the absorbance area of the OH stretching vibration region (4000–3000 cm-1) in difference spectra, the amount of water sorbed was significantly higher in poly-L-lactic acid (PLLA) and polyvinyl chloride (PVC) than in polyethylene (PE) and polytetrafluoroethylene (PTFE), increasing with the hydrophilicity of the surface. The OH stretching band of difference spectra shifted from 3499 cm-1 for PVC, to 3416 cm-1 for PE and finally to 3387 cm-1 for PTFE, indicating a more strengthened hydrogen-bonding network in the PTFE matrix upon water vapor sorption.

Infrared spectroscopy of neutral water clusters at finite temperature: Evidence for a noncyclic pentamer

Infrared spectroscopic study of neutral water clusters is crucial to understanding of the hydrogen-bonding networks in liquid water and ice. Here we report infrared spectra of size-selected neutral water clusters, (H2O) n (n = 3-6), in the OH stretching vibration region, based on threshold photoionization using a tunable vacuum ultraviolet free-electron laser. Distinct OH stretch vibrational fundamentals observed in the 3,500-3,600-cm-1 region of (H2O)5 provide unique spectral signatures for the formation of a noncyclic pentamer, which coexists with the global-minimum cyclic structure previously identified in the gas phase. The main features of infrared spectra of the pentamer and hexamer, (H2O) n (n = 5 and 6), span the entire OH stretching band of liquid water, suggesting that they start to exhibit the richness and diversity of hydrogen-bonding networks in bulk water.

Dalnegorskite Ca5Mn(Si3O9)2, a New Pyroxenoid of the Bustamite Structure, a Rock-Forming Mineral of Calcic Skarns in the Dalnegorsk Borosilicate Deposit, Primorsky Krai, Russia

Dalnegorskite, a new pyroxenoid with the crystal chemical formula Ca2Ca2MnCa(Si3O9)2 and simplified formula Ca5Mn(Si3O9)2, is a rock-forming mineral in the B-bearing calcic skarns in the Dalnegorsk borosilicate deposit (Dalnegorsk, Primorsky Krai, Russia). It belongs to the bustamite structural type and forms a continuous solid-solution series with isostructural ferrobustamite Ca2Ca2FeCa[Si3O9]2. These pyroxenoids form beige, pinkish white and milky white radiated aggregates typically consisting of split thin acicular to fiber-like individuals and are associated with hedenbergite, datolite, andradite, galena, sphalerite, and pyrrhotite. Dmeas. = 3.02(2), Dcalc. = 3.035 g cm–3. Dalnegorskite is biaxial negative, α = 1.640 (3), β = 1.647 (3), γ = 1.650 (3)°, 2Vmeas. = 75(10)°. The average chemical composition of the holotype (electron microprobe data) is: 0.23 MgO, 40.02 CaO, 5.02 MnO, 3.64 FeO, 50.65 SiO2, total 99.56 wt %. The empirical formula calculated for 18 O atoms is Ca5.03Mn0.51Fe0.36Mg0.04Si6.01O18. The crystal structure of the new mineral was obtained from X-ray diffraction data using the Rietveld method, Rp= 0.0345, Rwp = 0.0444, R1 = 0.0790, and wR2 = 0.0802. Dalnegorskite is triclinic, P-1, a = 7.2588(11), b = 7.8574(15), c = 7.8765(6) A, α = 88.550(15), β = 62.582(15), γ = 76.621(6)°, V = 386.23(11) A3, and Z = 1. Dalnegorskite is distinct from the related mineral wollastonite in the infrared spectrum. The wave numbers of the maxima of strong bands in the Si–O stretching vibration region in the IR spectrum of dalnegorskite are (cm–1): 905, 937, 1025, and 1070. The holotypic specimen of dalnegorskite is kept in the collection of the Fersman Mineralogical Museum, Russian Academy of Sciences, Moscow, Russia (no. 96201).

The structure and interaction properties of two task-specific ionic liquids and acetonitrile mixtures: A combined FTIR and DFT study.

The mixtures of ionic liquid (IL) and acetonitrile (CH3CN) can be used as reaction media, supercapacitors and thermally stable electrolytes. The macroscopic properties of ILs-CH3CN mixtures have been extensively studied. However, some fundamental questions regarding the microscopic properties of ILs-CH3CN mixtures still remain to be answered. In this work, the structure properties and hydrogen-bond interactions of two task-specific ILs, i.e., 1-propylnitrile-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([PCNMIM][Tf2N]) and 1-(2'-hydroxylethyl)-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([C2OHMIM][Tf2N]), and CH3CN were studied using the combination of Fourier transform infrared spectroscopy (FTIR) and density functional theory (DFT) calculations. The aromatic C‒H stretching vibration region of the cation was an area of special focus. Excess infrared spectroscopy with enhanced resolution was applied to analyse the original infrared spectra. It is found that: (1) The two ILs form stable hydrogen-bonds with CH3CN. (2) Ion cluster, ion cluster-acetonitrile, and ion pair-acetonitrile are identified in the mixture. Acetonitrile cannot break apart the strong electronic interaction between the cation and anion in the examined concentration range. (3) The hydrogen-bonds are weak strength, closed shell and electrostatic dominant interactions. (4) The preferred interaction site of [PCNMIM]+ cation is the hydrogen atom at the C2 site, while that of [C2OHMIM]+ cation is the hydrogen atom in the hydroxyl group.

A combination of FTIR and DFT to study the microscopic structure and hydrogen-bonding interaction properties of the [BMIM][BF4] and water.

The structure and hydrogen-bond interaction property of water and a model ionic liquid (IL): 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM][BF4]) were studied using the combination of Fourier transform infrared spectroscopy (FTIR) and density functional theory (DFT) calculations. The O‒D stretching vibration region of the deuterated water was an area of special focus. Excess infrared spectroscopy with enhanced resolution was applied to analyse the original infrared spectra of v(O‒D). It is found that: (1) [BMIM][BF4] forms stable hydrogen-bonds with water in the mixture. (2) The hydrogen-bonds are weak strength, closed shell and electrostatic dominant interactions. The preferred interaction site of [BMIM]+ cation is the hydrogen atom at the C2. (3) Cage hexamer water, cyclic tetramer water, cyclic trimer water, ion cluster-water complex, ion pair-water, and anion-water complexes are identified in the mixture. When the mole fraction of D2O (x(D2O)) is larger than 0.9, ion cluster and ion pair were broken apart into individual cations and anions. The cage hexamer water, cyclic tetramer water, and cyclic trimer water disappear at x(D2O) < 0.8, 0.5, and 0.3, respectively. HDO formed by H/D isotope exchange was detected when x(D2O) is less than 0.3.

Complex Defects in Mg-Doped Lithium Niobate Crystals Over a Wide Concentration Range and Their Manifestation in IR Absorption Spectra in the OH Stretching Vibration Region

Structural defects of nominally pure congruent and stoichiometric LiNbO3 crystals and a series of congruent crystals doped with 0.91–5.91 mol% MgO were compared and comprised two concentration thresholds at ~3.0 and ~5.5 mol% MgO. The main band parameters of OH stretching vibrations in IR absorption spectra (frequency, half-width, intensity) displayed abrupt changes near the concentration threshold at 5.5 mol% MgO. The OH stretching-vibration band shifted to higher frequency by ~50 cm–1 because of the formation of (MgLi)+–(MgNb)3––OH–complexes upon reaching the second Mg concentration threshold.

Hydrogen-bonded 2-benzylphenol and its crystalline polymorphism

The thermal and infrared (IR) spectroscopic measurements of 2-benzylphenol were performed during the crystallization process of the stable and metastable phases. The analysis of the IR spectra of metastable phases in the OH stretching vibration region allows us to conclude that, in contrast to the structure of the stable polymorph, which consists of cyclic tetramers of hydrogen-bonded molecules, the structure of metastable polymorphs consists of chains of hydrogen-bonded molecules. The differential scanning calorimetry experiments have shown that in purified samples only one metastable polymorph was formed with melting temperature 290.2 K. In the samples which were used without purification two metastable polymorphs were observed, with melting temperatures 290.2 and 296.6 K. Both polymorphs melt well below the stable one, which melts at 324.7 K. At temperature ∼1.1 Tg, generation of the fluctuating crystal nuclei of the metastable phase in supercooled liquid begins.

The Vibrational Circular Dichroism Pattern of the ν(C=O) Bands in Isoindolinones.

The IR and vibrational circular dichroism (VCD) spectra of both enantiomers of Me-, iPr-, nBu-, Ph-, and CH2 Ph-substituted isoindolinones in solution and KBr pellets were measured and interpreted by DFT calculations. The spectra in solution revealed no important differences in the C=O stretching vibration region while the interpretation of very distinct spectra taken in pellets required determining the crystal structures. The studied compounds crystallized in the P21 21 21 (Me, iPr, CH2 Ph), P31 (nBu), and P21 (Ph) space groups. We found that the quality of simulated spectra strongly depends on the substituent, the structure of the molecular cluster assumed, basis set, and use of the dispersion correction. The IR spectra can be reproduced well based on the simplest linear arrangement of hydrogen-bonded chains mimicking the molecular arrangement in the crystals. We found no common approach to reproduce all the registered VCD spectra in the crystal phase. For the Me and nBu isoindolinones, the VCD pattern was the best reproduced by full optimization of the selected large molecular clusters. For iPr, Ph and CH2 Ph derivatives optimizing only the position of H-atoms in a fragment frozen as in the crystal provides the best results. Such an approach can reduce the computation time from months to one week.

The ability of ionic liquids to form hydrogen bonds with organic solutes evaluated by different experimental techniques. Part I. Alkyl substituted imidazolium and sulfonium based ionic liquids

This work is devoted to the quantitative study of hydrogen bond formation of N-alkyl substituted ionic liquids with proton acceptor and proton donor organic solvents. 1-Butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide [BMIM][NTf2], 1-butyl-3-methylimidazolium tetrafluoroborate [BMIM][BF4], 1-butyl-3-methylimidazolium trifluoromethanesulfonate [BMIM][TfO], 1-butyl-3-methylimidazolium hexafluorophosphate [BMIM][PF6], triethylsulfonium bis(trifluoromethylsulfonyl)imide [Et3S][NTf2], 1-butyl-3-methylimidazolium tricyanomethanide [BMIM][TCM], 1-hexyl-3-methylimidazolium tetrafluoroborate [HMIM][BF4] were investigated by solution calorimetry and FTIR-spectroscopy techniques. The stretching vibration region of CO group of 2-pentanone in mixture with N-alkyl substituted ionic liquid in inert solvent carbon tetrachloride was analyzed at different concentrations of components for the estimation of proton donor ability of ionic liquids. Also, the stretching vibration region of the OH-group of methanol was studied in a ternary system carbon tetrachloride (inert solvent), methanol (proton donor) and N-alkyl substituted ionic liquid for the estimation of proton acceptor ability of ionic liquids. The hydrogen bond enthalpy of methanol in ionic liquids was calculated using data of measured solution enthalpies and data extracted from the literature. The frequency shifts of the OH-group of methanol induced by intermolecular interactions within ionic liquids in a carbon tetrachloride solution were compared with the hydrogen bonding enthalpies of methanol with ionic liquids. A linear relationship between the frequency shifts of the OH-groups and hydrogen binding enthalpies of methanol in ionic liquids were found. According to measured FTIR-spectroscopy data, the N-alkyl substituted ionic liquids analyzed in this work possess weak proton donor properties, and at the same time their proton acceptor ability (basicity) is much higher and shows dependency on anion structure.

Analysis of Lipids in the Medulla of Japanese Hair and Their Function

The hair is composed of the cuticle (the outermost surface), cortex (its major part), and medulla (in the hair center). The lipid content of the medulla of Caucasian hair is relatively higher than that of African-American hair. However, the types of lipids therein remain unidentified. The aim of the current study was to analyze the constituent lipids of the medulla of Japanese hair, and to identify their function. A lipid peroxidase fluorescent reagent was used to investigate region-specific differences in the lipid content of the medulla (the tip, middle, and root portions). Since the medulla is important for the hair’s glossiness, we also investigated the relationship between the lipid content and hair glossiness. The lipid content of hair, based on the absence or presence of lipid species in the medulla, was investigated using thin-layer chromatography (TLC). Micro-attenuated total reflectance Fourier-transform infrared spectrophotometry (micro-ATR FTIR) was used to analyze the similarities between the standard and medulla lipids, focusing on the methylene/methyl stretching vibration region. The data indicated that the medulla contained unsaturated lipids, the content of which decreased from the root to the tip of the hair. Hair glossiness was reduced with the decreasing lipid content, suggesting that unsaturated lipids of the medulla play a role in glossiness. The TLC analysis revealed differences in the type and amount of hair lipids in the medulla. While squalene and oleic acid spots were detected in hair with a continuously maintained medulla, these compounds were not detected in hair in which the medulla was not maintained. The medulla constituents similar to oleic acid and squalene were also identified by the micro-ATR FTIR spectrum analysis and the previous report. The findings indicate that the medulla is composed of at least squalene and oleic acid.

Three different kinds of weak C-H⋯O=C inter- and intramolecular interactions in poly(ε-caprolactone) studied by using terahertz spectroscopy, infrared spectroscopy and quantum chemical calculations

The long range structure of poly(ε-caprolactone) (PCL) has been studied by terahertz (THz) spectroscopy, infrared (IR) spectroscopy and quantum chemical calculations (QCCs). Natural bond orbital (NBO) analysis and the calculation of the interatomic distances between C-H and O=C groups in PCL crystalline indicate that the PCL chain has three kinds of weak intermolecular interactions between the CH2 and C=O groups. In the IR spectra, significant changes due to the influence of hydrogen bondings were observed in the CH2 and C=O stretching vibration regions. The results of QCCs performed by using the Cartesian Coordinate Tensor Transfer (CCT) method to assign the THz spectra of PCL suggest that the peaks at 47 and 67 cm−1 reflect the atomic motions of the C=O + CH2 moiety derived from the weak C-H⋯O=C hydrogen bondings. THz spectroscopy allows us to observe the intermolecular hydrogen bondings of the polymer separately, since hydrogen bondings with different strengths yield different peaks in a THz spectrum. The results of THz and IR spectral analysis, and QCCs all indicate that PCL forms three kinds of weak intermolecular C-H⋯O=C hydrogen bondings between the CH2 and C=O groups. This may be one of the causes for the low melting temperature but high crystallinity of PCL. There are about six interactions in PCL and about sixteen interactions in polyglycolic acid (PGA), within the lamellar thickness. Therefore, it is suggested that the difference in the number of intermolecular interactions within the lamellar thickness leads to the difference in melting points between the two polymers.

Synthesized amino-functionalized porous clay heterostructure as an effective thickener in waterborne polyurethane hybrid adhesives for lamination processes

The use of waterborne polyurethane (WPU) adhesives with non-volatile organic compounds (non-VOCs) has essentially expanded in laminating adhesive applications due to stringent environmental regulations, including on the release of VOCs. To function well, the inferior properties of WPUs should be overcome with good adhesion and cohesion mechanisms. High-performance WPU adhesive was synthesized by incorporating an amino-functionalized porous clay heterostructure (APCH) into the WPU to increase its internal strength via formation of urea linkages between fillers and the polymer matrix, to yield an organic/inorganic hybrid adhesive with greater cohesion. Urea linkages, as characterized by Fourier-self deconvolution of the C=O stretching vibration region (1600−1800cm−1), increased with increasing APCH content. In addition, APCH significantly enhanced the adhesion properties of bonded joints together with an improved thermal stability of the adhesive, affirmed by the DSC analysis and higher viscosity observed by a Brookfield viscometer. The highest peel strength (126N/m) was achieved with a WPU hybrid adhesive containing 2.0wt% APCH, which can be used for application in untreated oriented polypropylene (OPP) lamination.

Chemical, Physical, and Barrier Properties of Edible Film from Flaxseed Mucilage

Chemical, physical, and barrier properties of flaxseed mucilage-based films were investigated to determine the appropriate applications for coating or packaging of food or bioproducts. The film samples were formed via casting with the addition of glycerol as a plasticizer up to a maximum of 5 wt.%. Fourier transform infrared (FTIR) spectra showed an increase of intensity in the –OH stretching vibration region and the appearance of a new peak at 2883.1 cm-1 in the plasticized film samples. These changes may indicate possible interactions between the mucilage and glycerol. With increasing glycerol concentration, the water activity decreased, while the moisture content and water solubility increased. With regard to barrier properties, the water vapour permeability (WVP) and oxygen permeability (OP) notably increased with increasing glycerol content. With these high WVP and OP values, the films can be potentially extended for coating or packaging fresh produce.