Stearic Acid Salts Research Articles

Effect of Composition on Adhesion and Chemical Resistance in Multilayer Elastomer Laminates

The defense against dangerous chemical agents imposes demanding requirements for the development of protective materials, such as elastomers, plastics, and fabrics. While chemical protective clothing is commercially available, its elasticity, flexibility, stretchability, and chemical resistance spectrum may be restrictive and in need of further improvement. In this paper, a multilayer elastomer laminate, consisting of bromobutyl rubber (BIIR), acrylonitrile-butadiene rubber (NBR), and a fluoroelastomer (FKM), was fabricated to meet broad-range protection against chemical agents, while remaining flexible and stretchable. The bonding between the multiple layers was investigated via formulations designed to promote interlayer adhesion. The effects of magnesium oxide (MgO), zinc oxide (ZnO), stearic acid, carbon black, and phosphonium salt on the vulcanization and adhesion of the BIIR–NBR–FKM laminate were systematically studied using cure rheometry and T-peel tests. The optimized formulations of each rubber yielded adhesion strengths of 19 N/2.5 cm and >65 N/2.5 cm for the BIIR–NBR laminate and NBR–FKM laminate, respectively. The chemical resistance of these three elastomer sheets and their strongly bonded laminates was measured according to ASTM F739 and the time-lag method for methyl ethyl ketone, toluene, and butylamine. The laminates showed excellent resistance to the selected chemicals, with detected breakthrough times of longer than 1000 min. Also, some laminates were observed to have longer breakthrough times than the equivalent thickness of the individual elastomers making up the laminate.

Self-organization of stearic acid salts on the hemispherical surface of the aqueous subphase allows functionalization of matrix-assisted laser desorption/ionization mass spectrometry target plates for on-plate immobilized metal affinity chromatography enrichment

In this work we propose an approach for formation of periodic two-dimensional structures on a solid substrate via self-assembly of stearic acid molecules on an aqueous subphase drop containing metal ions. It was shown that when a saturated solution of stearic acid in n-hexane was applied to the hemispherical surface of an aqueous media containing barium ions, barium stearate monolayer was formed, which spontaneously collapsed during movement from the drop surface to the substrate. By means of infrared and Raman spectroscopy, light and scanning electron microscopy, atomic force microscopy and matrix-assisted laser desorption/ionization mass spectrometry it was proved that a multi-structure of collapsed metal stearate monolayers with a developed surface was formed on the substrate surface. Thin films formed by a single application of stearic acid solution in n-hexane to a drop of aqueous lanthanum nitrate solution were used for selective enrichment of human butyrylcholinesterase adducts with diisopropyl fluorophosphate.

Effect of Sealing Treatments on Erosion–Corrosion of a Fe-Based Amorphous Metallic Coating in 3.5 wt.% NaCl Solution with 2 wt.% Sand

In this study, a Fe-based amorphous metallic coating (AMC) was sealed with three sealants, i.e., stearic acid, aluminum phosphate and cerium salt, respectively. Two types of electrochemical tests, namely the ex situ electrochemical impedance spectroscopy test and the in situ potentiostatic polarization test, were conducted to evaluate the erosion–corrosion resistance of as-sprayed and as-sealed AMCs. The results show that the aluminum phosphate–sealed AMC exhibits the best erosion–corrosion resistance with the higher critical flow velocity compared with the as-sprayed AMC, which is attributed to the deep penetration of aluminum phosphate and high hardness of the sealed layer. In contrast, the sealants of stearic acid and cerium salt are easily removed by sand particle impacting, deteriorating their erosion–corrosion resistance.

Wastewater Treatment for Mercury and Arresting Mercury Contaminants Movement Within Industrial Soil

We have proposed optimal methods of treating both the waste- and stormwater for metallic and soluble mercury within the soil of mercury-based chlorine- and sodium-hydroxide production sites. The problem has been solved by combining physical, chemical and physicochemical treatment methods. Through the use of various filtering materials, coagulants and flocculants followed by sorption through AB-17-8 and Lewatit TR-214 ion exchangers, the level of mercury within wastewater has been decreased by about 99.9%. Demercurization of mercury-contaminated areas to the complete extraction of metallic mercury has been carried out by draining and the subsequent transfer of water-based compounds into a stable form through chemical immobilization without any prior soil removal. To achieve the aforesaid result we have treated the soil with stearic-acid salts solutions, which resulted in almost complete arrest of mercury within the soil.

THERMO- AND LIGHT STABILIZING ACTIVITY OF VINYLOXYCLOPROPANE ADDUCTS WITH THIOLS IN THE COMPOSITIONS BASED ON PVC

During exploitation of PVC products, the negative impact of high temperatures and light, and also the destructive influence of various microorganisms, leads to the deterioration of physical-mechanical properties and change of products painting. For prevention of the dehydrochlorination process of PVC, it is necessary to use the effective complex stabilizers, including biostabilizers, differing with their high processability and simultaneously possessing biocidal properties. 
 In this work the results of investigations of influence of the synthesized sulphur-containing epoxycyclopropanes as stabilizing additives for prevention of the dehydrochlorination process of the compositions based on plasticized PVC have been presented. The influence of these compounds as co-stabilizers in the composition of complex stabilizers – stearates Ca (CaSt2) and Zn (ZnSt2) on thermo- and light stability of PVCcompositions and also on their physical-mechanical and exploitation indices has been studied. It has been established the synthesized epoxy- and cyclopropane-containing mono- and disulphides jointly with stearic acid salts form the synergic mixtures, which can improve the physical-mechanical properties of PVC compositions, their thermal and light stability.

Alteration of crystallinity and thermal properties from incompatibility between ibuprofen and boundary lubricants

Lubricant is an essential compound for pharmaceutical formulation since it is often required to ensure the success of pharmaceutical manufacturing especially tablet compression and capsule filling process. Most lubricants used in pharmaceutical industry are boundary lubricants. The most commonly used boundary lubricants are metallic salts of fatty acids such as magnesium stearate and stearic acid. However, other lubricants, including fatty acid esters, inorganic materials and polymers have been used in the cases when stearic acid and metallic salts of fatty acids do not meet the performance expectation. In this study, stearic acid, magnesium stearate, aluminium monostearate and glyceryl dibehenate were chosen as the boundary lubricants whereas ibuprofen (IBU) was employed as the model drug. The aims of this study are to investigate the incompatibility between IBU and these boundary lubricants and to observe the alteration of crystallinity and thermal properties with differential scanning calorimetry (DSC), hot stage microscopy (HSM) and powder X-ray diffraction (PXRD) techniques. The eutectic formation between IBU and all boundary lubricants was revealed with DSC, PXRD and HSM techniques. The thermal properties of individual substance and all physical mixture (PM) between IBU and lubricants from DSC analysis were confirmed with the HSM technique. The partial melting temperature (PMT) and complete melting temperature (CMT) observed from HSM were close to the thermal parameters obtained from DSC results. Moreover, FT-IR spectra indicated an interaction between IBU and boundary lubricants via hydrogen bonding since the vibrational frequency in the region 1700–1400 cm−1 shifted to lower value. This understanding of alteration of crystallinity and thermal properties from incompatibility between compounds is beneficial for pharmaceutical solid dosage form development.

Efficient Fractionation and Analysis of Fatty Acids and their Salts in Fat, Oil and Grease (FOG) Deposits.

A fractionation methodology of fat, oil and grease (FOG) deposits was developed based on the insolubility of fatty acid salts in dichloromethane (DCM) and the relatively high solubility of fatty acids and triglycerides in DCM. Using this method, coupled with spectral analysis, it was shown that fatty acids rather than fatty acid salts were the predominant species in FOG deposits obtained from three metropolitan locations in the United States and that fatty acid triglycerides were either not detected or were present in very small concentrations. This solubility-based fractionation approach also revealed the presence of nitrogen-containing compounds that had not been previously detected in FOG deposits including peptides and (or) proteins. The comparison of the ratios of stearic acid salts to stearic acid versus the ratio of palmitic acid salts to palmitic acid in FOG deposits may indicate that the initial step in FOG deposit formation is the preferential precipitation of stearic acid salts.

Zeta potential study of biodegradable antimicrobial polymers

Abstract Biodegradable polymers have gained increasing interest in recent years, especially in food packaging industry. The biodegradation process is intrinsically related to adhesion of degradation-promoting bacteria on the surface of a biodegradable packaging. On the other hand, because of a direct contact with food, these materials should be resistant to colonisation by pathogenic bacteria. Thus, successful design of a biodegradable antimicrobial material critically depends on the interplay between the ability to control the strength of bacteria–polymer interactions. The aim of this work was to measure and analyse the effect of three positively charged antibacterial polyhexamethylene guanidine hydrochloride (PHMG) derivatives (sulfanilic acid salt, stearic acid salt, and polyethylene (PE) wax blend) on electrokinetic potential ( ζ ) of three biodegradable polymers: poly(hydroxybutyric acid) (PHB), polycaprolactone (PCL) and poly(lactic acid) (PLA). For this purpose, the streaming current vs pressure curves were recorded and analysed using the Helmholtz–Smoluchowski theory. The ζ vs pH dependency provides a simple and useful characterisation of an electrical double layer forming on the surface of biodegradable polymers in contact with an aqueous electrolyte. The undoped polymers displayed the ζ vs pH curves typical for electrically neutral polymers, with the isoelectric point, IEP = 3.5–4.0. The effect of PHMG on ζ vs pH curves depends on both the nature of the matrix polymer and the chemical form of PHMG. The stearate salt is shown to affect the curves to the smallest extent, while the most pronounced shifts towards higher pH were observed for PHMG in the form of PE wax (for PCL and PHB), or sulfanilic acid salt (for PLA). The surface of almost all PHMG-doped polymers used in this study (with exception of PLA doped with PHMG stearate) was more positive than the bare biodegradable polymers. From the point of view of electrostatic interactions, the addition of PHMG (especially in the form of PE wax, and especially for PHB) would thus probably enhance electrostatic polymer–bacteria interactions, possibly altering the antimicrobial activity of such polymers.

Average Orientation of a Molecular Rotor Embedded in a Langmuir–Blodgett Monolayer

A molecular rotor in which a naphthalene rotator is attached through a silicon atom to three fatty acid chains has been synthesized, and Langmuir-Blodgett techniques were used to deposit on silica surfaces monolayers of its calcium salt, both neat and diluted with stearic acid salts. The monolayer films have been characterized by ellipsometry and Fourier transform infrared (FT-IR) grazing-incidence attenuated total internal reflection (GATR) spectroscopy on Si-SiO(2) and by UV-vis absorption spectroscopy on SiO(2). The measurements were combined with calculations of the electronic (INDO/S) and vibrational (DFT) transition moment directions to deduce the average orientation of the rotor molecules, including the naphthalene ring, relative to the surface. In both neat and mixed films, the naphthalene ring is found to preferentially tilt toward the surface, enough that its rotation is most likely hindered. A comparable picture was obtained from molecular mechanics calculations on a mixed film of the naphthalene rotor and stearic acid.

Influence of Cationic Composition and pH on the Formation of Metal Stearates at Oil–Water Interfaces

We study the formation of layers of metal stearates at the interface between a decane solution of stearic acid and aqueous salt solutions of variable composition and pH by monitoring the evolution of their mechanical, optical, and chemical properties as a function of time after formation of the interface. For values of the pH below the pK(a) of stearic acid hardly any interfacial activity is observed. For pH > pK(a), stearic acid deprotonates at the interface and forms metal stearates, eventually leading to the formation of macroscopic solid layers. Dynamic interfacial tension measurements reveal that the process takes place in several stages, which we attribute to the successive formation of dilute and dense monolayers followed by three-dimensional growth. In the presence of divalent ions, the solid layers display a significant increase in the dilatational storage modulus. Experiments performed with an aqueous phase containing multiple cation species (artificial seawater) give rise to particularly pronounced growth of solid layers, which preferentially incorporate Ca(2+) as revealed by X-ray photoelectron and infrared spectroscopy. Our results highlight in particular the importance of the complex synergistic effects of simultaneously present monovalent and divalent cation species on the interfacial adsorption.

Preparation of coral-like porous gold for metal ion detection

Coral-like porous gold (PAu) as a sensing substrate for metal ion was prepared using a templating method with an aluminum precursor and stearic acid salts. After selective etching of the nanoporous alumina in bicontinuous phase, free-standing pure gold on the ITO substrate was obtained. The resulting materials showed submicron-sized pores in a pure gold network and high electro-conductivity as bulk gold. In a proof-of-concept test, we found that SH-modifed PAu/ITO electrode was good applicable sensing materials in low concentration of Hg(II).

Calcium Sulfate as High-Performance Filler for Polylactide (PLA) or How to Recycle Gypsum as By-product of Lactic Acid Fermentation Process

Reinforcing of polylactide (PLA) with fillers can be an interesting solution to reduce its global price and to improve specific properties. Starting from calcium sulfate (gypsum) as by-product of the lactic acid fermentation process, novel high performance composites have been produced by melt-blending PLA and this filler after a previous specific dehydration performed at 500°C for min. 1 h. Due to PLA sensitivity towards hydrolysis, it has first been demonstrated that formation of β-anhydrite II (AII) by adequate thermal treatment of calcium sulfate hemihydrate is a prerequisite. Then, the modification of filler interfacial properties with different coating agents such as stearic acid (SA) and stearate salts has been considered. The effect of surface treatment on molecular, thermal and mechanical properties has been examined together with the morphology of the resulting composites. To take advantage of the improved lubricity and better wetting characteristics, the filler was coated by up to 2% (by weight) SA. The coating of the filler leads to PLA–AII composites that surprisingly exhibit thermal stability, cold crystallization and enhanced impact properties. Such remarkable performances can be accounted for by the good filler dispersion as evidenced by SEM–BSE imaging of fractured surfaces. As far as tensile proprieties are concerned, notable utilization of uncoated filler or filler coated by stearate salts leads to PLA–AII composites characterized by higher tensile strength and Young's modulus values. The study represents a new approach in formulating new melt-processable grades with improved characteristic features by using PLA as polymer matrix.

Ozonolysis of model olefins—Efficiency of antiozonants

In this study, the efficiency of several potential long lasting antiozonants was studied by ozonolysis of model olefins. 2-Methyl-2-pentene was selected as a model for natural rubber (NR) and 5-phenyl-2-hexene as a model for styrene butadiene rubber (SBR). A comparison was made between the efficiency of conventional antiozonants like N-(1,3 dimethylbutyl)-N′-phenyl-p-phenylene diamine (6PPD), N-isopropyl-N′-phenyl-p-phenylene diamine (IPPD), and a mixture of diaryl p-phenylene diamines (Wingstay 100) and some newly synthesized antiozonants. The stearic acid salt of 6PPD (PPD-C18), 2,4,6-tris(4-(phenylamino)phenyl)-1,3–5-triazinane (ADPAT), and 4-pyrole diphenylamine (PDPA) showed a higher efficiency than the conventional antiozonants in both NR as well as SBR model system. Special attention was paid to the carboxylic acid salts of 6PPD such as PPD-C18, which has shown good long-term protection of passenger tire sidewall compounds. It was demonstrated that by varying the chain length, C7, C18, and C22, of the carboxylic acid part of the 6PPD salts, the ozone protection was not influenced under the selected test conditions. The 6PPD salts made from strong acids like succinic acid (SA) and methyl sulfonic acid (MSA) appeared to be less efficient than PPD-C18. It was also investigated whether the reactions between ozone and the double bonds of the model rubber could be measured online by a spectroscopic technique. It was demonstrated that near infrared spectroscopy is a suitable technique to study these reactions. FT Raman looked also a promising technique because of the high response factor of double bonds. However, the addition of p-phenylene diamines (PPDAs) to the sample solution resulted in a strong discoloration (dark brown) and therefore in a high fluorescence background signal. This technique can therefore not be used for the evaluation of staining antiozonants. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci, 100: 853–866, 2006

A novel method for synthesis of a Ni/Al2O3 catalyst with a mesoporous structure using stearic acid salts

Nickel stearate was used as a chemical template and metal source for the easy-and-fast preparation of Ni/Al2O3 catalyst with a mesoporous structure. Ni-Nx and Ni-Hx were prepared using an NH4OH-treated precipitate and a HCl-treated solution as the chemical template, respectively, and these materials show only the effect of the chemical template, a regular pore size distribution. Ni-Nx with both a developed framework and textural porosity show a larger surface area and pore volume but a less irregular pore structure than Ni-Hx which shows a well-developed framework porosity. The 27Al NMR MAS analysis showed that nickel oxide supported on active alumina allows Ni2+ ions to diffuse into the surface lattice vacancies of the alumina spinel structure. Such a migration of metal ions may be limited to the first few layers of the supports, but leads to the production of hard-to-reduce metal oxide (i.e. a high metal-to-support interaction). Ni-Nx was also found to have a more dispersed nickel particle configuration than Ni-Hx after reduction.

Plasticization of poly(styrene‐b‐isobutylene‐b‐styrene) ionomers by acid salts of 2‐ethylhexyl‐p‐dimethylaminobenzoate

AbstractPoly(styrene‐b‐isobutylene‐b‐styrene) block copolymer ionomer (overall molecular weight = 71,200 g/mole; 25.5 wt% polystyrene, 4.7% sulfonation of phenyl units, 100% neutralized with KOH) was compounded with various organic and inorganic acid salts of 2‐ethylhexyl‐p‐dimethylaminobenzoate (ODAB) to explore the efficacy of these compounds as ionic plasticizers. Results were compared to the same polymer plasticized by zinc stearate. Plasticizers were added to the polymer at levels of ≈5 wt%. Films were prepared by solution casting from tetrachloroethylene. Thermogravimetric analysis (TGA) showed all ODAB derivatives to have lower decomposition temperatures than zinc stearate. Dynamic mechanical analysis (DMA) of the films showed varying degrees of ionic plasticization as evidenced by a lowering of the temperature at which the onset of flow occurred. With the exception of the stearic acid salt of ODAB, all ODAB derivatives were more efficient ionic plasticizers than zinc stearate. Among the ODAB derivatives, the degree of ionic plasticization varied, with the methane sulfonic and p‐toluene sulfonic acid salts being most effective, leading to the conclusion that processing temperatures could be tailored to specific applications by choice of plasticizer and level of incorporation.

Raman Spectroscopy of Langmuir Monolayers at the Air−Water Interface

A new approach for the acquisition of Raman spectra of Langmuir layers at the air−water interface is presented. Colloidal Ag is grown electrochemically under layers of the anionic surfactants stearic acid and dipalmitoylphosphatidic acid sodium salt (DPPA) on an aqueous AgNO3 subphase. The Ag colloid layer supports surface-enhanced Raman scattering (SERS) of the Langmuir layers with minimal interference from the subphase. Spectra of good signal-to-noise ratio have been acquired. These spectra are interpreted in terms of the headgroup chemistry and the degree of alkane chain order as a function of surface pressure.

The influence of counterions and hydrophobic moieties on the thermostability of Langmuir-Blodgett multilayers

Langmuir-Blodgett (LB) multilayers with various counterions and different organic moieties (one- and two-chain fatty acids, polymeric acid) are prepared to investigate on line temperature-dependent structural changes and desorption by small-angle X-ray scattering (SAXS), interference-enhanced reflection and Nomarsky microscopy. On temperature increase a sequence of phase transitions can be observed. A crystalline LB film melts to a fluid phase and eventually desorbs either from droplets or from a homogeneous film. The phase sequence depends on the counterion: nickel stearate and magnesium stearate melt while the layered structure is conserved; SAXS measurements reveal a continuous, multistage decrease in the layer spacing as well as the total film thickness. In case of magnesium stearate it can be shown that a thickness loss at T = 53°C is due to the evaporation of water from the polar head group planes. Lead stearate exhibits the opposite behaviour: before rupturing, a coexistence of two phases is observed. These general features do not depend on the substrate (pure silicon or silanized silicon); the coating only influences size and lateral distribution of the droplets. The hydrophobic moiety shifts the temperature of these phase transitions: salts of a double-chain fatty acid display a decreased thermal stability, and salts of a polymeric acid an increased stability compared with the stearic acid salts.

Quantitative AFM of langmuir-blodgett films

Because of their applications in the areas of non-linear optics, molecular electronics, and biosensors, Langmuir-Blodgett (LB) films have been extensively studied by a wide variety of scattering and spectroscopic techniques. The atomic force microscope has emerged as an important tool for studying LB films because of its unprecedented ability to quantitatively measure films with high resolution.The unique abilities of quantitative AFM imaging motivated us to investigate the effect of incorporating different divalent metal cations and fatty acids of different chain length into films deposited on both amorphous and ordered substrates. Once substrate effects have been accounted for, multilayer Langmuir-Blodgett films of palmitic, stearic and arachidic acid salts show that the area per molecule is primarily controlled by the detailed interactions of the counterion with the carboxylic acid group. However, the lattice dimensions and symmetry are dictated by the close packing of the alkane chains, given the constraint of area per molecule set by the counterion.

On the Structure of Mixed Langmuir‐Blodgett Films of Two Different Fatty Acid Salts

Abstract Langmuir-Blodgett films of mixed behenic and stearic acid salts of cadmium were deposited and investigated by small-angle X-ray scattering. The ratio of compounds was varied from 1:4 to 4:1. It was found that for 1:1 ratio the lattice spacing was equal to 54.0 Å, which corresponds to double chain length of arachidic acid or to a sum of one chain length of stearic and behenic acid salts. In this case a single completely mixed phase was obtained. For the other ratio X-ray patterns contained two systems of reflections, each of them corresponding to one of the pure fatty acid salts (49.0 Å and 58.5 Å respectively), implying the coexistence of two phases.

On the structure of mixed Langmuir-Blodgett films

Langmuir-Blodgett films of two mixed cadmium fatty acid salts were deposited and investigated by small-angle X-ray scattering. For one of the systems investigated (a mixture of stearic and behenic acids) it was found that for a 1:1 ratio, the lattice spacing corresponds to the sum of stearic and behenic acid salts, while, for any other ratio, the X-ray patterns contained two systems of reflections, each of them corresponding to one of the pure acid salts (49.0 Å and 58.5 Å, respectively). The other system investigated (a mixture of behenic and palmitic acid salts) gave a completely different result: a single phase was present for any molar ratio of compounds and the lattice spacing varied with the molar ratio itself.