pinecone/core-2020-05-10-deduplication huggingface dataset:
Acetylacetonates of Nickel( 11) and Copper( 11) as\ud
Accelerators for the Epoxy Resin System

The acetylacetonates of nickel(II) and copper(II) serve as accelerators for the anhydride-curable epoxy resin system. An appreciable lowering in the cure gel time and a substantial increase in the rate of curing is observed with enhanced concentrations of the metal chelates. Cure kinetic studies and cure schedules have been followed using a differential scanning calorimeter. The thermal and electrical insulation characteristics of the cured epoxy system are little affected by the variation of temperature, voltage, and aging under UV radiation. (C) 1994 John Wiley & Sons, Inc
Cure characterization of triglycidyl epoxy/aromatic amine systems

The curing of triglycidyl para-aminophenol (TGPAP) epoxy resin with three aromatic amine hardeners, diaminodiphenye sulphone (DDS), pyridinediamine (PDA), and toluenediamine (TDA), has been investigated. A series of isothermal cures was conducted and analyzed by Fourier transform infrared spectrometry (FTIR) and differential scanning calorimetry (DSC). The chemical reactions occurring during cure were monitored at different temperatures by qualitative and quantitative estimation of different groups in the IR spectra, and the ratio of rate constants (k2/k1) were evaluated. Dynamic DSC analysis of TGPAP/TDA resulted in two exothermal peaks, indicating cure kinetics different from those of TGPAP/DDS and TGPAP/PDA systems, which gave a single exothermal peak. Various kinetic parameters such as total heat of reaction ?H?, activation energy Ea, Frequency factor z, and order of reaction n were evaluated for all the three systems. From the initial kick-off temperatures and activation energy values it was concluded that the rate of curing followed the order TDA amp;gt; PDA amp;gt; DDS. The reaction conversions during cure, evaluated from IR analysis, were exactly the same as those obtained from DSC Borchardt-Daniels kinetics. Using this model, the plots of time vs. temperature for different conversions were constructed for all the three systems; on the basis of these, the cure cycles can be fixed
Modeling the tensile behavior of fiber bundles with irregular constituent fibers

In this paper, the effect of fiber dimensional irregularities on the tensile behavior of fiber bundles is modeled, using the finite element method (FEM). Fiber dimensional irregularities are simulated with sine waves of different magnitude. The specific stress-strain curves of fiber bundles and the constituent single fibers are obtained and compared. The results indicate that fiber diameter irregularity along fiber length has a significant effect on the tensile behavior of the fiber bundle. For a bundle of uniform fibers of different diameters, all constituent fibers will break simultaneously regardless of the fiber diameter. Similarly, if fibers within a bundle have the same pattern and level of diameter irregularity along fiber length, the fibers will break at the same time also regardless of the difference in average diameter of each fiber. In these cases, the specific stress and strain curve for the bundle overlaps with that of the constituent fibers. When the fiber bundle consists of single fibers with different levels of diameter irregularity, the specific stress-strain and load-elongation curves of the fiber bundle exhibit a stepped or &ldquo;ladder&rdquo; shape. The fiber with the highest irregularity breaks first, even when the thinnest section of the fiber is still coarser than the diameter of a very thin but uniform fiber in the bundle. This study suggests that fiber diameter irregularity along fiber length is a more important factor than the fiber diameter itself in determining the tensile behavior of a fiber bundle consisting of irregular fibers.<br /
Preparation of aqueous anionic poly-(urethane-urea) dispersions: Influence of the nature and proportion of the urethane groups on the dispersion and polymer properties

Aqueous poly(urethane‐urea) dispersions were prepared by the prepolymer mixing technique without the use of any organic solvent. Most of the work focused on the use of two aliphatic diisocyanates (α,α, α', α'‐tetramethyl‐1,3‐xylylene diisocyanate and isophorone diisocyanate) and two macrodiols (α,ω‐poly(propylene glycol) (Mn = 1000) and α,ω‐poly(caprolactone) (Mn = 530)) in conjunction with a fixed proportion of emulsifying agent (dimethylol propionic acid, neutralized with triethyl amine) and the same chain extender (1,2‐ethylene diamine). The properties of both the dispersions and the dried polymer films, as well as those of some model prepolymers, were characterized as a function of the initial composition to establish criteria leading to the optimized performance in terms of dispersion stability and particle size and polymer properties. The most important parameter in this search was found to be the [NCO]/[OH] ratio, which gave the best results when it approached a value of 2
Natural zeolite polypropylene composite film preparation and characterization

In this research, the preparation and characterization of polypropylene (PP) and natural zeolite composites were studied. Natural zeolite mined in Gördes, Turkey was used as an alternative filler to CaCO3. Films were prepared by the extrusion of PP, and surface-modified zeolite was made by polyethylene glycol 4000 with 2-4% zeolite. Zeolite-filled composites had densities between 0.73 and 0.83 g/cm3 and had void fractions of 0.07-0.20. Although the permeability of water vapour through 2% zeolite-filled composites was very small, 4% zeolite-filled films had very high permeabilities. The yield stresses of 2-4% zeolite-containing films were around 26-27 N/mm2 and were lower than that of PP, which indicated no adhesion between PP and zeolite. The effect of zeolite on the thermal degradation behaviour in air and in a N2 atmosphere was also studied. In air, zeolites did not cause the oxidation of PP. In a N2 atmosphere, although the start of the thermal degradation of PP was retarded by zeolite, composites degraded at a faster rate than PP once the degradation started. At a processing temperature of 200°C, zeolites had no effect on the degradation of PP
A cross self-curing system for an aqueous-based PU hybrid

[[abstract]]Isocyanate (NCO)-terminated polyurethane (PU) prepolymer comprises carboxylic acid, which is obtained from a conventional PU preparation procedure. Aziridine-terminated PU oligomer is prepared by an addition reaction of aziridine to NCO-terminated PU prepolymer after it is neutralized with triethylamine. This PU oligomer is then dispersed with water and becomes a single-component self-curable aqueous-based PU dispersion (PU-AZ). PU carboxyl groups are not only the ionic centers stabilizing the aqueous polymer dispersion, but also serve as PU curing sites toward the curing reaction with its aziridine terminal groups on drying. This self-curable PU-AZ dispersion is miscible and compatible with other carboxyl groups containing aqueous-based PU dispersion in any ratio, which results in a cross self-cured PU hybrid formation on drying. This cross self-cured PU hybridization process allows property modification and the curing of PU simultaneously without the addition of any external curing agent.[[notice]]補正完畢[[journaltype]]國外[[incitationindex]]SC
Rubber-Toughened Polypropylene Nanocomposite: Effect of Polyethylene Octene Copolymer on Mechanical Properties and Phase Morphology

Rubber-toughened polypropylene (PP)/org-Montmorillonite (org-MMT) nanocomposite with polyethylene octene (POE) copolymer were compounded in a twinscrew extruder at 230Â°C and injection-molded. The POE used had 25 wt % 1-octene content and the weight fraction of POE in the blend was varied in the range of 0â€“20 wt %. X-ray diffraction analysis (XRD) revealed that an intercalation\ud
org-MMT silicate layer structure was formed in rubber toughened polypropylene nanocomposites (RTPPNC). Izod\ud
impact measurements indicated that the addition of POE led\ud
to a significant improvement in the impact strength of the\ud
RTPPNC, from 6.2 kJ/m2 in untoughened PP nanocomposites\ud
to 17.8 kJ/m2 in RTPPNC containing 20 wt % POE. This\ud
shows that the POE elastomer was very effective in converting brittle PP nanocomposites into tough nanocomposites. However, the Youngâ€™s modulus, tensile strength, flexural modulus, and flexural strength of the blends decreased with respect to the PP nanocomposites, as the weight fraction of POE was increased to 20 wt %. Scanning electron microscopy (SEM) was used for the investigation of the phase morphology and rubber particles size. SEM study revealed a two-phase morphology where POE, as droplets was dispersed finely and uniformly in the PP matri
Effect of zeolite filler on the thermal degradation kinetics of polypropylene

In this study, the thermal degradation behavior of polypropylene (PP) and PP-zeolite composites was investigated, Clinoptilolite, a natural zeolitic tuff, was used as the filler material in composites. The effects of both pure clinoptilolite and silver-ion-exchanged clinoptilolite on the thermal degradation kinetics of the PP composites was studied with differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Polymer degradation was evaluated with DSC at heating rates of 5, 10, and 20°C/ min from room temperature to 500°C. The silver concentration (4.36, 27.85, and 183.8 mg of Ag/g of zeolite) was the selected parameter under consideration. From the DSC curves, we observed that the heat of degradation values of the composites containing 2-6% silver-exchanged zeolite (321-390 kj/kg) were larger than that of the pure PP (258 kj/kg). From the DSC results, we confirmed that the PPzeolite composites can be used at higher temperatures than the pure PP polymer because of its higher thermal stability, The thermal decomposition activation energies of the composites were calculated with both the Kissinger and Ozawa models. The values predicted from these two equations were in close agreement. From the TGA curves, we found that zeolite addition into the PP matrix slowed the decomposition reaction; however, silver-exchanged zeolite addition into the matrix accelerated the reaction. The higher the silver concentration was, the lower were the thermal decomposition activation energies we obtained. As a result, PP was much more susceptible to thermal decomposition in the presence of silver-exchanged zeolite
DSC study of transitions involved in thermal treatment of foamable mixtures of PE and EVA copolymer with azodicarbonamide

The transitions and reactions involved in the thermal processing of binary mixtures of polyethylene and poly(ethylene-co-vinyl acetate) copolymers with different concentrations of a foaming agent (azodicarbonamide) were studied using differential scanning calorimetry (DSC). The effect of ZnO as a kicker also was discussed. The temperature at the maximum rate and the heat evolved were measured for all the processes—melting, transitions, and reactions—all the mixtures prepared were measured and compared. Azodicarbonamide decomposed differently depending on the polymeric matrix. These data can be very useful for the plastic processing industry.Contract grant sponsor: Generalitat Valenciana; contract grant number: GV01-42 and GR01-36
Moisture sorption and thermal characteristics of polyaramide blend fabrics

Four types of fabrics woven from various polyaramid fibers of Nomex and Kevlar blends were characterized by morphology, XRD, elemental analysis, thermal analysis, and moisture adsorption isotherms. The blends consisted of Polybenzimidazole/ Kevlar blend (40% FBI and 60% Kevlar®), Nomex Delta A (blend of 60% Kevlar and 40% Nomex®), Nomex Delta T (blend of 75% Nomex, 23% Kevlar, and 2% P140 antistatic fiber), and Nomex III (fabric with a 95/5 blend of Nomex and Kevlar) containing 1% steel fiber. TGA and DTG curves have been compared to evaluate thermal behavior of the FBI, Kevlar, and Nomex blends and the resuls were correlated with the moisture sorption data. The data were also compared with fiber morphologies provided by SEM and crystallinities derived from XRD diffrac tograms. Moisture adsorption isotherms were correlated with a number of empirical models, including Nernst, Freundlich, Handersen, Iglesias-Chirife, and with the models having a theoretical background such as Langmuir, BET, GAB, and Hüttig. The linear regression models were statistically analyzed to obtain the best fitting model that explains the sorption profiles of the samples and theoretical monolayer moisture capacities of Nomex and Kevlar blends were calculated by using Hüttig isotherms
Determination of thermodynamic and transport properties of solvents and non solvents in poly(L-lactide-co-glycolide)

Thermodynamic properties, partition coefficient, and diffusion coefficients of the various solvents (acetone, dichloromethane, trichloromethane, ethyl acetate, ethyl alcohol, tetrahydrofuran, and water) in poly(lactide-co- glycolide) (PLGA) at infinite dilution of the solvent have been determined by inverse gas chromatography (IGC). In IGC method, which is based on the characteristic equilibrium partitioning of a solute between a mobile phase and a stationary phase, a small pulse of solvent is introduced into the column and by the aid of retention volume of the solvent, several polymer solvent interaction properties, namely retention volume (Vg), infinitely dilute weight fraction activity coefficient (Ω1∞), Flory-Huggins interaction parameter (χ), and solubility parameters of the polymer (δ2∞) can be determined. The thermodynamic results indi cated that trichloromethane and dichloromethane were the most suitable solvents among all the solvents studied for PLGA. The partition (K) and diffusion coefficients (Dp) of various solvents at infinite dilution of the solvent were calculated by using the model developed by Pawlisch et al. (Macromolecules 1987, 20, 1564). The optimum K and D p values that best fit the data were found and the model predicted experimental data very well. So IGC method is a powerful tool for the determination of thermodynamic and diffusion properties of solvent in polymer at infinite dilution of the solvent
Mechanical and morphological properties of recycled high-density polyethylene, filled with calcium carbonate and fly ash

In this study, mechanical and morphological properties of composites made up of recycled high-density polyethylene (HDPE) filled with calcium carbonate and fly ash (FA) were studied. Interfacial interactions were modified to improve the filler compatibility and mechanical properties of the composites by surface treatment of the FA filler with 3-amino propyl triethoxy silane. The composites were prepared by using a Thermo Haake Rheomixer. Effect of filler loading and treatment of FA with silane coupling agent on mechanical and morphological properties were investigated and it was found that silane treatment indicated significant improvements on the mechanical properties of the HDPE-FA composites. The improvement with silane treatment of FA was also confirmed by applying the Pukanszky model. Scanning electron microscopy on the fracture surface of composites had given direct evidence of better interfacial adhesion via silane treatment
Toughened electrospun nanofibers from crosslinked elastomer-thermoplastic blends

A crosslink-able elastomeric polyester urethane (PEU) was blended with a thermoplastic, polyacrylonitrile (PAN), and electrospun into nanofibres. The effects of the PEU/PAN ratio and the crosslinking reaction on the morphology and the tensile properties of the as-spun fibre mats were investigated. With the same overall polymer concentration (9 wt %), the nanofibre containing higher composition of PEU shows a slight decrease in the average fibre diameter, but the tensile strength, the elongation at break and tensile modulus of the nanofibre mats are all improved. These tensile properties are further enhanced by slight crosslinking of the PEU component within the nanofibres.<br /
In vitro monitoring of surface mechanical properties of poly(L-lactic acid) using microhardness

Poly(L-lactic acid) (PLLA) was immersed in
a simulated body fluid (SBF) solution at 37.58C for distinct
times. The variation of the surface mechanical properties
of PLLA samples with immersion time was followed by
microhardness. These measurements showed that PLLA
microhardness decreased significantly (  60%) after only
30 days of immersion. The results were explained in terms
of hydrolytic degradation of the samples. The dependence
of microhardness with the applied dwell time was also analyzed.
The creep curves were successfully described by a
power law. A decrease of the creep constant k as the
immersion time increased was found. Differential scanning
calorimetry was also used to analyze the changes in the
physical properties of PLLA, namely in crystallinity degree
(Xc) and glass transition temperature (Tg), as a function of
the immersion time in SBF. A significant variation in the
crystallinity degree of PLLA, initially nearly amorphous
(Xc 5 9%), was detected after only 3 days of immersion
(Xc 5 37%). The interpretation of this behavior was based
on the hydrolysis process suffered by PLLA
Kinetic study of the decompositions involved in the thermal degradation of commercial azodicarbonamide

The transitions and reactions involved in the thermal treatment of several commercial azodicarbonamides (ADC) in an inert atmosphere have been studied by dynamic thermogravimetry analysis (TGA), mass spectrometry and Fourier transform infrared (FTIR) spectroscopy. A pseudo-mechanistic model, involving several competitive and non-competitive reactions, has been suggested and applied to the correlation of the weight loss data. The model applied is capable of accurately representing the different processes involved, and can be of great interest in the understanding and quantification of such phenomena, including the simulation of the instantaneous amount of gases evolved in a foaming process. In addition, a brief discussion on the methodology related to the mathematical modeling of TGA data is presented, taking into account the complex thermal behaviour of the ADC.Contract grant sponsor: Generalitat Valenciana; contract grant numbers: GRUPOS03/159, GV01-42, GR01-36
Interfacial Conversion for Poly(para-phenylenevinylene) at a Cholesteric Liquid Crystal Surface

A new approach for the preparation of poly(para-phenylenevinylene) (PPV) with an ordered structureis presented. PPV is synthesized by a precursor methodusing a cholesteric liquid crystal medium. The resultantPPV film is observed to have a cholesteric fingerprint-liketexture, indicating replication of the cholesteric liquid crystalmedium. Infrared absorption measurements confirmthat the PPV has essentially the same molecular structureas normal PPV film. Ultraviolet–visible absorption measurementsshow that the absorption band due to p2p* transitionof the conjugated main-chain is located at 402 nm.The conversion is found to occur at the interface with thecholesteric liquid crystal medium as a mechanical process
Preparation of Emulsifier-Free Polystyrene by Conventional Emulsion Polymerization with a Hydrolysable Emulsifier

An alkali-hydrolysable surfactant, (1-tetradecyloxycarbonylmethyl)trimethylammonium chloride, was used as an emulsifier for emulsion polymerization of styrene in water. The polymerization yielded a high molecular-weight polymer almost quantitatively. Addition of a small amount of NaOH to the resulting latex solution precipitated the polymer immediately. Analysis of the centrifuged solid indicated almost perfection of both recovery of the polymer and removal of surface-active species from it. Minimization of ionic species in the polymer solid was confirmed by a high contact angle of the polymer film with water
Layered clay/epoxy nanocomposites: Thermomechanical, flame retardancy, and optical properties

In this study, layered clay/polymer nano-composites were developed based on epoxy resins and montmorillonite as the nanoplatelet reinforcement. Clay particles were treated with hexadecyltrimethylammonium chloride (HTCA) through an ion exchange reaction. In this way, Na+ interlay er cations of the clay is exchanged with onium cation of the surfactant that turns the hydrophilic clays (MMT) to organophilic (OMMT) characteristics. Thermal analysis results revealed that the glass transition temperature (Tg) and the dynamic mechanical properties including the storage and loss modulus of the neat epoxy resin increases by the incorporation of clay particles. It was also found that flame resistance of the polymer is improved by the addition of the clay particles
Anhydride Production as an Additional Mechanism of Poly(3-hydroxybutyrate) Pyrolysis

Anhydrides production is newly proposed as an additional pyrolysis mechanism of a biopolymer, poly(3‐hydroxybutyrate) (PHB). In spite of many suggestions of multiple degradation mechanisms, simple random chain scission by β‐elimination has been accepted as an exclusive mechanism of the thermal degradation of PHB. However, a wide range of activation energy value of the degradation and the deviation from the random chain scission statistics have suggested the presence of other kinds of mechanism out of the random scission. To confirm other mechanisms out of the random scission, minor pyrolyzates from PHB were characterized with 1H/13C‐NMR, Fourier transform infrared spectroscopy, and fast atom bombardment mass spectrometry. As a result, crotonic anhydride and its oligomers were detected as minor products from condensation reactions between carboxyl groups. The anhydrides production must be one reaction out of the conforming process to the random degradation statistics and contribute to the complexity of PHB pyrolysis. An expected thermal degradation pathway of PHB was proposed
Linear Viscoelastic and Morphological Description of Multiphase Systems Affected by Processing Parameters

Influence of processing methods, in terms of comparing compression and injection moldings, on the rheological behavior of polycarbonate (PC)/acrylonitrile-butadiene-styrene (ABS) blends and PC/ABS/glass fibers composites is presented. Blend compositions and fiber content are considered as material variables. For blends, the effect of the processing route on the viscoelastic functions is evident only for low shearing frequencies. Injection molding created morphology with cocontinuous character, while compression molded blends have "relaxed'' structure, where dispersed phase domains are several times larger than in injection molded ones. The glass fiber reinforcement led to the significant differences in viscoelastic properties of composites processed by injection and compression molding. Injected composites have both moduli always higher than compression molded. Also, fiber lengths are reduced more for compressing molding. (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 119: 989-999, 201
Effect of antistatic additives on mechanical and electrical properties of polyethylene foams

Polyethylene foams with different antistatic additives (Atmer 7325, Atmer 7105, and Atmer 190) were prepared by extrusion and stored during 6 months of time span in a real life environment. The antistatic performance was evaluated by measuring the surface resistivity and throughout decay-time experiments. Mechanical properties and migration tests were also performed. It was found that the migration of antistatic agents is in general low enough, which allows to maintain the antistatic performance for periods of time larger than 6 months. The tests revealed that the desired low surface resistance and required low static decay time could be achieved with all the antistatic agents under test. Moreover, the additives with amina (Atmer 7105 and 7325) as an active agent showed slightly better antistatic performance than the one with the ionic agent (Atmer 190). The addition of an antistatic agent does not significantly affect the mechanical behavior of the foam indicating a desired feature concerning industrial applications