Abstract  Dibutyl Adipate, the diester of butyl alcohol and adipic acid, functions as a plasticizer, skin-conditioning agent, and solvent in cosmetic formulations. It is reportedly used at a concentration of 5% in nail polish and 8% in suntan gels, creams, and liquids. Dibutyl Adipate is soluble in organic solvents, but practically insoluble in water. Dibutyl Adipate does not absorb radiation in the ultraviolet (UV) region of the spectrum. Dibutyl Adipate is not toxic in acute oral or dermal animal toxicity tests. In a subchronic dermal toxicity study, 1.0 ml/kg day-1 caused a significant reduction in body weight gain in rabbits, but 0.5 ml/kg/day was without effect. In a study with dogs, no adverse effects were observed when an emulsion containing 6.25% Dibutyl Adipate was applied to the entire body twice a week for 3 months. Dibutyl Adipate was tested or dermal irritation using rabbits and mice and a none to minimal irritation was observed. Dibutyl Adipate at a concentration of 25 % was not a sensitizer in a guinea pig maximization study. Undiluted Dibutyl Adipate was minimally irritating to the eyes of rabbits and 0.1 % was nonirritating. A significant increase in fetal gross abnormalities was observed in rats given intraperitoneal injections of Dibutyl Adipate at 1.75 ml/kg on 3 separate days during gestation, but no effect was seen in animals given 1.05 ml/kg Dibutyl Adipate was as not genotoxic in either bacterial or mammalian test systems. Clinical patch tests confirmed the absence of skin irritation found in animal tests. Clinical phototoxicity tests were negative. Dibutyl Adipate at 0.1 % was not an ocular irritant in two male volunteers. In a clinical test of comedogenicity, Dibutyl Adipate produced no effect. The Cosmetic Ingredient Review (CIR) Expert Panel recognized that use of Dibutyl Adipate in suntan cosmetic products will result in repeated, frequent exposure in a leave-on product. The available data demonstrate no skin sensitization or cumulative skin irritation, no comedogenicity, and no genotoxicity. Combined with the data demonstrating little acute toxicity, no skin or ocular irritation, and no reproductive or developmental toxicity, these data form an adequate basis for reaching a conclusion that Dibutyl Adipate is safe as a cosmetic ingredient in the practices of use and concentrations as reflected in this safety assessment.

Abstract  This study examined the antimicrobial/antifungal ability of a tissue conditioner containing a photocatalyst for Escherichia colt, Streptococcus mutans, Staphylococcus aureus and Candida albicans. The photocatalyst was mixed with tissue conditioners powders at concentrations of 0, 10, 15, and 20 wt%. Tissue conditioners powders containing a photocatalyst were mixed with liquid to make test specimens. Test specimens inoculated by each microorganism were irradiated by ultraviolet light for 0-, 2- and 4 hours. The antimicrobial/antifungal effects were evaluated by the CFU technique. The CFU values of each microorganism for tissue conditioners containing a photocatalyst showed significant decrease following UV-irradiation. The improvement in antimicrobial/antifungal effects was concomitant with the increase of the mixing ratio and the irradiation time. Therefore, the results indicated that tissue conditioners containing a photocatalyst might have photocatalytic ability.

Abstract  A colonic-release delivery system containing naproxen inclusion complex with 2-hydroxypropyl-beta-cyclodextrin (2-HPPCD) was originally proposed. The core tablets consisting of the naproxen inclusion complex and disintegrants (Ac-Di-Sol (R), Primojel (R), Avicel (R) or Polyplasdone (R)) were formed by direct compression, and then coated with the polymers, either pH-dependent Eudragit (R) S 100 and/or pH-independent Eudrag (R) RS 100 with plasticizers like dibutyl sebacate (DBS) and aluminum tristearate (AT). The in vitro release characteristics were evaluated in simulated gastric fluid for 2 h and then subsequently in simulated intestinal fluid for 12 It. The potential histological changes were also evaluated after direct dosing of suspensions of naproxen alone and powdered mixtures of inclusion complex-loaded tablet into rat intestinal segments. No distinct colonic release was observed when disintegrants were excluded in the single-layered coated tablets regardless of coated structures, giving a zero-order fashion over 12 h. The coated tablet with double-layered structures of Eudragi (R) S 100 and Eudragi (R) RS 100 was not also applicable. In contrast, colonic release was achieved when the core tablet containing inclusion complex and disintegrant was coated with only Eudragit (R) S100 in a single-layered structure. The colonic-release tablet was resistant in gastric fluid for 2h and for 2-4h in intestinal fluid, followed by rapid release of the drug after a total of 4-6 h of lag time depending on the type of disintegrants. The lag time was advanced in case of DBS while delayed in case of AT. On histological examination, the inclusion complex-loaded suspension caused less intestinal tissue damage than naproxen alone. Based on these findings, the colonic-release tablet with enteric coatings which contains inclusion complex and disintegrants could be useful to deliver drugs like naproxen to the lower small intestine and upper colon with increased dissolution and reduced intestinal tissue damage. (c) 2007 Published by Elsevier B.V.

Abstract  Six potential plasticizers for an ethylcellulose (EC) pseudolatex coating system (Aquacoat) were evaluated at three levels (25, 30, and 35%) to study the influence of these additives on the release of a model compound, propranolol hydrochloride, from pellets in two different media, dilute HCl and phosphate buffer, pH 7.4. For the majority of the plasticizers, the release rate decreased when larger amounts of plasticizer were incorporated into the coating. However, for the plasticizers dibutyl sebacate and dibutyl adipate, no further reduction in the release rate was observed following dissolution testing in dilute HCl when the level of plasticizer was increased from 30 to 35%. This suggests that the saturation capacity of these plasticizers in the film coating had been exceeded. The media pH was found to influence the dissolution characteristics of the coatings. Faster release rates as well as earlier curve inflection points and T50% values were observed for plasticizers evaluated in phosphate buffer. All plasticizers used were independent of pH. Correlation of the dissolution results with properties of free films indicated that slower release (more complete film formation) is associated with softer and weaker films with greater elongation.

Abstract  A potentiometric chemosensor for selective determination of sertraline was developed based on the molecular imprinting technique. The molecularly imprinted polymer was synthesized by precipitation polymerization, using sertraline hydrochloride as a template molecule, methacrylic acid as a functional monomer and ethylene glycol dimethacrylate as a cross-linking agent. The sensor was developed by dispersing the sertraline imprinted polymer particles in dibutyl sebacate plasticizer and embedding in poly(vinyl chloride) matrix. Characteristics of the proposed sensor were evaluated by measuring the potential response to sertraline hydrochloride in the range from 1.0 mu mol L-1 to 10 mmol L-1 with a near Nernstian response of 57.7 mV decade(-1) and a limit of detection of 0.8 mu mol L-1. The potentiometric selectivity coefficients of the proposed sensor were evaluated and it exhibited good selectivity to sertraline with respect to the other antidepressants. It was used as indicator electrode in potentiometric determination of sertraline in tablets and biological fluids.

Abstract  PURPOSE: A microencapsulation method that preserves the activity of an acid labile protein was developed. Methods: Solvent evaporation technique that employed ICH class 2 and 3 solvents methanol and acetone, respectively to dissolve pH-sensitive Eudragit polymers was investigated. Total protein released and lactase activities were measured using the USP method A for enteric cores and optimized with respect to process parameters.

RESULTS: The percentage yields and entrapment efficiencies were directly proportional to solid content. The mean percentage yield and entrapment efficiency of selected sample was 84 +/- 0.9% and 88 +/- 0.7%, respectively. The residual specific activity of lactase in the selected sample was 89% +/- 0.8 with a net activity loss of 2 +/- 0.28% and 4 +/- 0.52% under ambient and stressed storage, respectively. Dibutyl sebacate levels, lower processing temperatures and lower processing speeds were influential in modulating enzyme activity. The most important formulation factor affecting lactase stability was Eudragit type, followed in decreasing order by processing temperature, processing speed, and solid percentage.

CONCLUSIONS: Reliable control of lactase release was achieved by microencapsulating the enzyme with pH-sensitive Eudragit L and S enteric polymers using either acetone- or methanol-based solvent but lactase activity was preserved only in acetone-based formulations.

Abstract  Stabilizers (epoxidized linseed oil and epoxidized soybean oil) and plasticizers (acetyl tributyl citrate, diacetyl monolauryl glyceride and dibutyl sebacate) commonly used in polyvinylidene chloride (PVDC) films and extracts of such films were investigated for estrogenic and androgenic activity by means of estrogen receptor (ER) and androgen receptor (AR) competitive ligand-binding assays. Further, in in vivo experiments, ovariectomized Sprague-Dawley rats were observed for uterine wet weight change, uterine endometrium hyperplasia and vaginal mucosa cornification, following administration of each test compound or extract orally (0.5 or 500 mg/kg) or subcutaneously (0.5 or 100 mg/kg). No significant response or change was observed with any of the test compounds or extracts, either in vitro or in vivo. The results thus indicate that neither the stabilizers and plasticizers used in PVDC films, nor their extracts, exert sex-hormonal activity.

Abstract  The present work investigates release mechanisms of theophylline pellets coated with an aqueous ethyl cellulose (EC) dispersion containing plasticizers and hydroxypropyl methylcellulose (HPMC) as a water soluble pore former. Three different drug release mechanisms from coated pellets can be determined as a function of the water solubility of the plasticizers and the ionic strength of the release medium. Coated pellets with the addition of more hydrophilic plasticizers such as triethyl citrate (TEC) or diethyl phthalate (DEP) show an approximate zero-order-release rate. In contrast, two-phase release profiles can be observed from pellets coated with dispersions containing hardly soluble plasticizers such as dibutyl phthalate (DBP) or dibutyl sebacate (DBS). Only in a release medium of high ionic strength the water soluble pore former will remain in the coating. Thus the drug diffuses through a hydrated swollen membrane containing EC, HPMC and insoluble plasticizer. The release mechanisms depend on the glass transition temperature of the ethyl cellulose and therefore on the migration of the plasticizers and the pore former. This was shown by investigation of the migration of the additives and the influence of the temperature of the release medium on the release. Additionally, the study investigates the effect of curing and storage conditions of coated pellets on the drug release rate.

Abstract  A series of systemic toxicity tests for various types of compounds are presented with illustrative data and discussed in regard to their relevance as potential screening tests for dental compounds and products. In developing and marketing a new dental material, it is important not only to ensure safety for the patient but also for the dentist, dental assistant, and laboratory worker who routinely handles and uses the product. Data are presented on a number of commercially available dental products as well as various chemical entities, which were tested by one or more of the methods described.

Abstract  Otto Fuel II, a propellant in torpedoes, is composed of 76% 1,2 propanediol dinitrate (PGDN), 22.5% di-n-butyl sebacate, and 1.5% 2-nitrodiphenylamine (NDPA), and is largely recalcitrant to aerobic microbial degradation. Anaerobic microbial degradation of Otto Fuel II was tested by inoculating anaerobic enrichment media, containing either 2% (vol:vol) complete Otto Fuel II or 2% of a 0.02% solution of Otto Fuel II in methanol, with soil and water from sites contaminated with munitions or with landfill leachate. Anaerobic bacterial growth was completely inhibited by 2% Otto Fuel II. Two mixed bacterial enrichments developed in anaerobic media containing 2% (v/v) of a 0.02% solution of Otto Fuel II in methanol. After incubation, PGDN could not be detected in either enrichment, but was also not detectable in sterile controls, suggesting abiotic degradation of low concentrations of PGDN in reduced anaerobic medium. NDPA did not degrade in either enrichment. Similarly, complete Otto Fuel was recalcitrant to degradation by highly reducing methanogenic biomass collected from an upflow anaerobic sludge blanket bioreactor (UASB). A comparison of the degradative ability of autoclaved and viable biomass showed that low concentrations of PGDN autodegraded, however unlike the autoclaved anaerobic biomass, the viable anaerobic biomass degraded the NDPA component of Otto Fuel II. Two strains of anaerobic clostridia, strains SP3 and SPF, that caused the disappearance of NDPA at its limit of solubility in culture media, were isolated from the UASB bioreactor biomass. SP3 and SPF were shown, by comparison of 16S rDNA sequences, to be most closely related to Clostridium butyricum and Clostridium cochlearium respectively. Although NDPA was lost from cultures of both strains, metabolic end products were not identified. Neither strain could degrade NDPA unless supplied with an alternative energy source. In the culture system used, NDPA stimulated the growth of SP3 but it had no appreciable effect on the growth of SPF. Both SP3 and SPF degraded low concentrations of trinitrotoluene (TNT), without the production of detectable concentrations of aromatic amines. A possible method for the remediation of small spills of Otto Fuel II is suggested.

Abstract  Different ammonium nitrate controlled-release (CR) systems based on ethylcellulose have been investigated to reduce environmental pollution derived from nitrogen-fertilizer use. Coated ammonium nitrate granules were produced in Wurster-type fluidized-bed equipment using two different amounts of ethylcellulose. The highest one was modified by the addition of two plasticizers, dibutyl sebacate, and dibutyl phthalate. Having researched the encapsulation efficiency and the homogeneity of the coated granules, we carried out the kinetic-release experiments in water and soil. The release rate of the active ingredient was related to the thickness of the coating film, granule size, and type of plasticizer used. Using an empirical equation, the time taken for 50% of the active ingredient to be released into water and soil (T-50) was calculated. From the analysis of the T-50 values, we can deduce that the release rate of ammonium nitrate can be controlled, mainly changing the thickness of the coating film and using plasticizer as well. In water experiments, T-50 values for granules prepared without plasticizers ranged between 7.47 h for 1 mm < d < 2 mm granules coated with 10% of ethylcellulose and 24.06 h for 2 mm < d < 3 mm granules coated with 20% of ethylcellulose. For those prepared with plasticizers, T-50 ranged between 22.80 h for 1 mm < d < 2 mm granules containing dibutyl sebacate and 35.74 h for 1 mm < d < 2 mm granules containing dibutyl phthalate. However, in soil experiments T-50 values ranged between 10.24 h for 1 mm < d < 2 mm granules coated with 10% of ethylcellulose and 38.80 h for 1 mm < d < 2 mm granules containing dibutyl sebacate. Finally, a linear regression of the T-50 values was obtained by the results of the study carried out in water and soil. This allows us to predict the behavior of the formulations in soil. This could be useful in the design of systems which control the nitrogen release.

Abstract  Swellable porous hydrogel beads were loaded with diclofenac sodium and then coated with pseudo-latex ethylcellulose (EC) in a fluidized-bed spray coater. The drug release profile in-vitro can be modified by adding 25% or more triethyl citrate (TEC) or dibutyl sebacate (DBS) as a plasticizer. The plasticized coating film can overcome the swelling stress of the core and function as a barrier for sustained drug release. Adding TEC resulted in a near-zero order kinetics after an initial burst in the release profile, and adding DBS showed a first initial burst, a second stage of linear release, a third stage of slow release. The initial burst is due to the flaws or cracks on the surface of the coated-beads and it can be reduced by increasing the amount of plasticizer or film thickness and also by adjusting the thermal treatment time. A 4- to 6-h treatment at 60 degrees C was found to be the optimal condition to give the smallest initial burst for coating film containing TEC as a plasticizer. Adding hydrophilic hydroxylpropyl methylcellulose (HPMC) could smooth the initial burst and change the release profile to a Fickian-type release, and in this case increasing the thermal treatment time could reduce the release rate. Two kinds of EC-coated beads were tested in-vivo by using rabbits as animal models and showed good sustained release behaviors as the drug concentration in plasma could be maintained above 0.4 mu g/ml and lower than 1.5 mu g/ml for 24 h. (C) 1997 Elsevier Science Ireland Ltd.

Abstract  Recycled polyvinyl butyral (PVB) from the automotive industry was chemically modified by melt mixing with a vinyl trimethoxysilane (VTMS) silanation reagent, which tends to react with the hydroxyls present in the PVB structure to generate crosslinked bonds between the chains. This chemical modification resulted in the improvement of the solvent resistance to organic solvents without deeply impairing the mechanical properties of the polymer. The mixing of PVB with VTMS was carried out in an internal mixer equipped with roller type rotors and the mixture was subsequently compression molded. Soxhlet extraction confirmed a 70% increase in the modified polymer gel content. Depending on the mixing time, the dynamic crosslinking reactions occurring during this time did not prevent the compression molding of the polymer. Furthermore, static crosslinking was observed during compression molding, which resulted in the maximum crosslinking degree and solvent resistance. DMA analysis indicated different molecular structures produced by different mixing times and varying static and dynamic crosslink ratios. Infrared spectroscopy (FTIR) indicated that dibutyl sebacate was the main plasticizer of the recycled PVB. Thermogravimetric analysis suggested that the molecular structure of the modified polymer affected the decomposition of PVB. (C) 2016 Society of Plastics Engineers

Abstract  Vapor-liquid equilibrium (VLE) data for maleic anhydride( MAN) and its absorption solvents are important for developing and researching the MAN production process. Isothermal VLE data for MAN and di-n-butylsebacate (DBS) binary system at 413. 15, 433. 15 and 453. 15 K were determined with a modified ebulliometer in this work. Saturated pressure of pure DBS and MAN were measured and their Antoine constants were obtained. The experimental results were correlated and calculated using the NRTL model. The UNIFAC model was also used to predict the VLE data. At the same time, the parameters of the NRTL model for the MAN(1) + DBS (2) binary system were obtained. And the predicted results show a good agreement between the correlated data and the experimental data.

Abstract  Electrochemical Oxidation can offer a viable alternative to incineration, landfill, and deep well injection for disposal of harmful chemicals. The U.S. Navy generates about one million pounds of Otto Fuel LI waste per year. About two thirds of the waste is liquid and one third of it is solid waste contaminated with the fuel. Otto Fuel II is a three component liquid monopropellant used for torpedo propulsion. The Indian Head Division, Naval Surface Warfare Center has been tasked to conduct a feasibility study utilizing an indirect electrochemical oxidation process for the destruction of Otto Fuel II waste, and provide technical and engineering support for construction of a full scale disposal facility at the Naval Undersea Warfare Center, Keyport, WA. Indirect electrochemical oxidation of organic materials is facilitated by using metals ions in a mineral acid electrolyte as a regenerative catalyst or mediator. Silver, cobalt, nickel, cerium, magnesium, and iron have been used as regenerative oxidants(1).

Catalyzed Electrochemical Oxidation (CEO), a low temperature and low pressure electrochemical oxidation process developed by Battelle Pacific Northwest Laboratories (PNL) is being examined for use in the destruction of Otto Fuel II Waste(2,3). The CEO process uses the regenerative oxidant cerium (Ce3+/Ce4+) for the treatment of organic waste. Laboratory and bench scale studies showed that Otto Fuel II is readily destroyed by the CEO process. Pilot scale CEO studies are planned to determine the operational requirements for a full scale CEO plant to treat Otto Fuel LI waste. A summary of this work will be presented in this paper. The primary focus of the paper centers around the establishment of requirements for a full scale CEO facility.

Abstract  The mechanical and permeability properties of mixed ethylcellulose/pectin films cast from dibutyl sebacate (DBS) plasticised aqueous dispersions of Aquacoat(R) and Pectin USP have been investigated. The films were subjected to tensile testing and the tensile strength (sigma), work of failure, elongation at break, elastic modulus (E) and the sigma/E ratio have been determined. Increasing concentrations of pectin imparted increasing brittleness and decreasing toughness to the films. Despite the inclusion of increasing quantities of the hydrophilic pectin into the films, the permeability to moisture remained essentially the same. The results imply that there is a limit to the amount of pectin that can be included in the coating material to still produce a satisfactory film, but the protective nature of the ethylcellulose to moisture is not compromised. (C) 1997 Elsevier Science B.V.

Abstract  A novel cellulose-based oil absorbent crosslinked cellulose-dibutyl sebacate copolymers was prepared by the graft crosslinking polymerization of in situ synthesized dibutyl sebacate and cotton cellulose using potassium persulfate as an initiator. The copolymers were characterized by infrared spectroscopy, X-ray diffraction, scanning electron microscopy, thermogravimetry, differential scanning calorimetry, etc. The effects of reaction conditions, such as, ratio of reaction regents, reaction temperature, reaction time, etc, on the efficiency of oil absorbency were examined. The optimized reaction conditions for the synthesis of crosslinked cellulose-dibutyl sebacate copolymers were: m(cotton pulp):m(K2S2O8 initiator):m(dibutyl sebacate) = 1:0.025 :2.0(W/W), 75 degrees C, and 5-6 h. The resulting crosslinked cellulose-dibutyl sebacate copolymers were floppy and exhibited excellent oil absorbency efficiency.

Abstract  Properties of pharmaceutical drug polymer mixtures like miscibility, stability and drug release are determined by the interactions of active pharmaceutical ingredients (APIs) and excipients (e.g. plasticisers) with functional polymers. Molecular dynamics (MD) simulations (Materials Studio, COMPASS force field) are used to predict the principal behaviour of such drug products, especially miscibility and glass transition temperature (Tg). Different mixtures containing APIs (theophylline or ibuprofen (IBU)) and water-soluble (triethyl citrate, (TEC)) or water-insoluble plasticiser (acetyl tributyl citrate (ATBC) or dibutyl sebacate (DBS)) dissolved/dispersed in a cationic polymethacrylate (EUDRAGIT RS) were studied. Force field-based calculations of the cohesive energy densities of single constituents led to a qualitative approach according to Hanson describing the solid state of the mixture, while further calculations on the basis of the theory of free energy of mixing facilitated a semi-quantitative prediction. In the case of miscibility also calculation of Tg was possible via modelling specific volumes of amorphous cells at various temperatures. The simulated data correlated well with the experimental data obtained from differential scanning calorimetry (DSC) of drug products processed via hot-melt extrusion. Accordingly, the described method facilitates a good estimate of pharmaceutical polymer drug mixtures, thus decreasing product development time, as well as the consumption of active ingredients.

Abstract  The essential oils from the leaves and fruits of Bridelia retusa (L.) A.Juss. were isolated by hydrodistillation. The essential oils were obtained in 0.0013% yield as a pale yellow liquid and 0.0026% yield as a violet-light brown liquid for the leaf oil and fruit oil respectively. The composition of each essential oil was analysed by means of GC-(FID) and GC-MS. Eleven constituents accounting for 48.77% of total leaves oil were identified. The most abundant compound was phytol (33.4%), followed by phthalic acid (5.2%), 6, 13-dimethoxy-2, 3, 9, 10-tetramethylpentacene-1, 4, 8, 11-tetrone (3.4%), heptacosane (2.3%) and nonacosane (1.2%). Sixteen constituents accounting for 51.8% of total fruits oil were identified. The major components were dibutyl sebacate (25.6%), phytol isomer (4.8%), diacetin (4.3%), tricosane (3.9%), isophytol (2.7%), erucylamide (2.5%), phthalic acid (1.9%), hexadecanoic acid (1.5%) and eicosane (1.2%). The essential oils exhibited strong antioxidant activities with the IC50 values of 1.12 +/- 0.0010 mg/mL and 1.79 +/- 0.0005 mg/mL for the leaf and fruit essential oils respectively, by using the ABTS radical cation scavenging assay. The antibacterial activity of the essential oils was performed by using the standard disc diffusion method. The results revealed that the leaf and fruit essential oils of B. retusa were active against Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa with the minimum inhibitory concentrations (MICs) between 20-50 mg/mL.

Abstract  Plasticized systems of poly-beta-hydroxybutyrate (PHB) are studied, where low-molecular compounds traditionally used for this purpose for various systems, i.e., dioctyl sebacate, dibutyl sebacate, polyethylene glycol, Laprol 503, and Laprol 5003, are used as plasticizers. All of them are nontoxic and biodegradable compounds with a similar molecular weighs and comparable polarity of molecules. The main purpose of this study is to improve the deformability of PHB taking into account the structural changes in plasticized PHBs. The plasticizers chosen are completely compatible with the polymer and form a monophase system up to a plasticizer content of 15-20%. Art increase in the plasticizer content allows us to increase efficiently the deformability of the polymer (the relative breaking elongation of PHB at room temperature grows zip to 250-300%). At the same time, the system becomes considerably weaker and obtained from DSC measurements, the ratio between the amorphous and crystalline regions of PHB in the presence of plasticizers mentioned remains practically constant The changes in the elastic propel-ties of PHB/low-molecular plasticizer systems are mainly die to efficient weakening of intermolecular interactions in the amorphous regions of the polymer. A slight decrease in the crystalline order of PHB is of secondary importance.

Abstract  Four different plasticizers have been used to make the PVC gels: poly(vinyl chloride)-diethyl adipate (PVC-DEA), poly(vinyl chloride)-dibutyl sebacate (PVC-DBS), poly(vinyl chloride)-dioctyl phthalate (PVC-DOP) and poly(vinyl chloride)-dibutyl phthalate (PVC-DBP). The chemical structure and molecular weight of the plasticizers significantly affected the electric-field-induced adhesion of the gels. To explain the variations, the dielectric properties, space charge distributions, tensile properties and Raman spectra of the PVC gels were compared. Aliphatic ester (DEA and DBS) plasticizer-containing PVC gels showed larger electric-field-induced adhesion and dielectric constants than phthalate plasticizer (DBP and DOP)-containing gels. Raman spectroscopy suggested that there were different molecular interactions between PVC and the plasticizers. The dielectric constant and mechanical properties of the PVC gels were determined to be the key factors for determining the electric-field-induced adhesion.

Abstract  An experimental investigation was conducted to characterize the monopropellant droplet combustion of pure and blended isopropyl nitrate (IPN), suspended on quartz fibers in a quiescent atmosphere. The blends were prepared by mixing varying percentages by weight of IPN with less viscous n-heptane, as well as highly viscous desensitizer dibutyl sebacate (DBS). Ignition was achieved by using a heated 60 mu m Nichrome wire. The dependence of the burning rate constant of pure IPN on initial droplet diameter was investigated in the droplet size range of 0.79-1.97 mm. The blended IPN studies were carried out with initial droplet diameters of 2 and 1.5 mm for IPN-n-heptane and IPN-DBS blends respectively, to characterize the effect of gravimetric composition. The experiments revealed a strong dependence of IPN burning rate on droplet size. The IPN-DBS blends were characterized by severe micro-explosions, further atomizing the droplet, governed by the preferential evaporation of IPN over DBS. However, micro-explosions were conspicuously absent in case of IPN-n-heptane blends due to simultaneous gasification of both components. (C) 2013 Elsevier Ltd. All rights reserved.

Abstract  Gas chromatography (GC) with a Flame Ionisation Detector (FID) has been used to determine changes in the concentrations of the components of Otto Fuel II (OF) in contact with an 82% aqueous solution of hydroxylammonium perchlorate (HAP) in sealed vials at 31.7 degrees C during the period leading up to auto- ignition of the two liquids. The concentration of hydroxylamine in HAP was monitored over the same period using a titration method. It was found that 2-nitrodiphenylamine (2NDPA), the stabiliser in the OF, is completely consumed after about 65-70 h and that the concentration of hydroxylamine begins to fall at this point. 1,2-Propanediol dinitrate (propylene glycol dinitrate, PGDN), the energetic component in the OF, is not depleted significantly until after about 90 h. The evolution of nitrous oxide (N2O) between 65 and 90 It is attributed to the reaction of the hydroxylammonium ion with nitrous acids produced by PGDN decomposition at the liquid-liquid interface. Carbon dioxide (CO2) is evolved after similar to 90 h and is attributed to PGDN decomposition. HAP and PGDN are each thought to contribute to N2O evolution after similar to 90 h.

Abstract  The distribution of water-soluble (triethyl citrate and triacetin) and water-insoluble (acetyltriethyl citrate, acetyltributyl citrate, dibutyl phthalate, dibutyl sebacate, diethyl phthalate and tributyl citrate) plasticizers between the aqueous and polymer phases in an aqueous colloidal ethylcellulose dispersion, Aquacoat(R), was determined. A separation scheme was developed, which allowed the determination of the amounts of plasticizers dissolved and, in the case of water-insoluble plasticizers, also emulsified in the aqueous phase, and dissolved in the colloidal polymer particles. The plasticized ethylcellulose dispersion was separated by centrifugation and/or ultracentrifugation to obtain the various plasticizer-containing fractions. The plasticizer concentration in each phase was determined by a HPLC assay. The extent of the plasticizer partitioning was investigated with respect to the type (water-soluble or water-insoluble) and concentration of the plasticizer, and the solids content of the polymer dispersion. Water-insoluble plasticizers mainly partitioned into the polymer particles due to the higher affinity towards the polymer phase, however, the amount of emulsified plasticizer droplets increased with increasing plasticizer concentration after a plasticization time of 24 h. An 'association' coefficient, which was obtained from the ratio of the plasticizer concentration in the polymer to the concentration in the aqueous phase, was used to characterize the plasticizer partitioning. The fraction of plasticizer taken up by the colloidal polymer particles increased with increasing solids content of the polymer dispersion. It is therefore recommended to add the plasticizer to the undiluted dispersions followed by dilution to the desired solids content just prior to coating, rather than first diluting the dispersion followed by addition of the plasticizer.