pinecone/core-2020-05-10-deduplication huggingface dataset:
Monitoring cure in epoxies containing carbon nanotubes with an optical-fiber fresnel refractometer

Fresnel refractometry was used to follow the changes in the refractive index
during the isothermal curing of a simple difunctional epoxy resin, a commercial
formulated multifunctional epoxy blend, and the same two resin systems modified
by the addition of multiwalled carbon nanotubes. The refractive index change,
monitored via an embedded optical fiber, was correlated with the degree of cure
established from isothermal differential scanning calorimetry measurements. A
good correlation was established in all cases, indicating the potential of the
technique to be used for online cure monitoring in thermosetting resin carbon
nanocomposites
Modeling and simulation of photofabrication processes using unsaturated polyester resins

Several kinetic models have been proposed
to simulate thermosetting cure reactions. The most complex
models, based on a mechanistic approach of cure reactions,
are developed based on the concepts of free radical polymerization
and the mechanism of reactions with diffusion.
However, mechanistic models are usually quite impractical
for engineering purposes because of the difficulty in obtaining
the model parameters. An alternative to these mechanistic
models are the phenomenological models, formulated
in terms of the degree of cure and much easier to apply.
Phenomenological models have been largely used to study
thermal-initiated cure reactions, although only few works
used them to model the kinetics of ultraviolet-initiated cure
reaction. This work proposes a photo-thermal-kinetic model
to study the behavior of unsaturated polyester resins during
ultraviolet-initiated cure reactions. The model considers
samples with different amounts of initiator concentration
and cure reactions performed under different ultraviolet
light intensities. The model has been numerically solved
using the finite element techniquePortuguese Foundation for Science and Technology; contract grant number: POCTI/EME/58405/2004
Synthesis and characterization of copolymers of alkyl- and azo-thiophenes: chromic properties and photoinduced birefringence

Polyazothiophene is a type of polythiophene derivative that combines the electrical and luminescent properties of polythiophenes with the photoisomerization property of azopolymers. Extensive efforts have been made to improve the properties of polyazothiophenes, such as solubility, optical, and chromic properties. We report the preparation of copolymers of an alkylthiophene (3-octylthiophene, 3-OT) and an azothiophene (2-[N-ethyl-N-[4-[(4-(4-nitrophenyl)azo]phenyl]amino]ethyl 3-thienylacetate, 3-AzoT) in different ratios as an alternative route to improve these properties. The azosubstituted monomer contents in these copolymers were 6, 9, 12, and 51% (in mol), as evaluated by elemental analysis. Their chemical structures were confirmed by FTIR and 1H-NMR. HPSEC and thermal analysis were used to characterize the polymers. The presence of thermochromic and solvatochromic properties was demonstrated by UV-Vis spectroscopy. Optically induced birefringence was detected only in polymers with 12 and 51 mol % of azo-units. The introduction of different ratios of the azothiophene in the copolymer alters the polymer solubility and emissive properties. The results indicate that the polyazothiophene copolymers presented are promising active layers for optical devices and sensor
Flexural properties of sawdust reinforced phenolic composites: pilot study

The advantageous properties of sawdust and phenolic resins were combined by making sawdust reinforced phenolic composites with different percentages by weight of sawdust.  The sawdust was divided into three grades in accordance with its particulate size.  Garamite and propylene glycol were added individually and together to enhance the flexural properties of the composites obtained.  Without any garamite and propylene glycol, it was discovered that the best flexural properties of the composites were obtained when the percentage by weight of sawdust (< 300µ m) is up to 15%. Beyond this, the flexural properties dropped significantly; in addition, the fluidity of the composite was very low and the mixture was not suitable for casting.  In general, the flexural modulus of the composites decreases with an increase in sawdust content, i.e. they are more elastic but their maximum flexural strain does not improve.  Garamite was therefore added to improve the maximum flexural strains of the composites and this was successful.  The addition of propylene glycol makes the composite more plastic
Correlation between Sub-Tg relaxation processes and\ud
mechanical behavior for different hydrothermal ageing\ud
conditions in epoxy assemblies

The aim of this study is to understand aging phenomena by monitoring physical parameters after real and simulated aging experiments. This study focuses on aluminum-epoxy assemblies, which are commonly used on spacecraft structures. Different samples are submitted to simulated aging tests. Influence of temperature and moisture is analyzed. Evolution with aging is characterized at two different scales. The macroscopic behavior of the assemblies\ud
is studied by single lap shear test. A decrease in the\ud
shear rupture stress is observed with increasing temperature\ud
and relative humidity. It is demonstrated that temperature\ud
has more important influence. The molecular behavior in\ud
the adhesive joint is studied by dynamic dielectric spectroscopy measurements. This experiment gives access to molecular mobility in the adhesive. Dipolar entities are identified as evolving with aging conditions. The temperature is more effective than moisture at this scale. An interpretation of the molecular mobility before and after aging shows that water is an important parameter of this study. A link between mechanical and molecular behavior with hydrothermal aging is found. The decrease of mechanical properties occurs while failures become interfacial. In the same time, the interactions between hydroxyether and water increase. The evolution of the macroscopic behavior of the bonded assemblies is due to this combination observed at different scales
Poly(ethylene terephthalate-co-isophthalate) copolyesters obtained from ethylene terephthalate and isophthalate oligomers

A series of poly(ethylene terephthalate-co-isophthalate) copolyesters\ud
containing up to 50%-mole of isophthalic units were prepared by polycondensation\ud
from ethylene terephthalate and ethylene isophthalate fractions of linear oligomers\ud
containing from 5 to 6 repeating units in average. The polyesters were obtained in good\ud
yields and with high molecular weights. The microstructure of the copolyesters was\ud
studied as a function of reaction time by 13C-NMR showing that a random distribution of\ud
the comonomers was achieved since the earlier stages of polycondensation. The\ud
melting temperature and enthalpy of the copolyesters decreased with the content of\ud
isophthalic units so that copolyesters containing more than 25% of these units were\ud
amorphous. Isothermal crystallization studies made on crystalline copolyesters\ud
revealed that the crystallization rate of copolyesters decreased with the content in\ud
isophthalic units.Peer ReviewedPostprint (author’s final draft
Statistical thermal stability of PVC

Experimental design was used to optimize the processing parameters for the decomposition of poly (vinyl chloride). Factorial design and face centered composite design (FCC) were applied to determine the optimum conditions. A total of 10 g PVC powder was mixed with different amounts of zinc stearate (ZnSt 2) and natural zeolite and tested for thermal stability. Factorial fitted model was explained by first order pattern due to the significant main effect regression constants, and FCC model was described by second order model owing to higher order polynomial coefficients. FCC design was superior to factorial design as FCC considers not only its pure quadratic effects contribution but also its higher overall desirability for thermal stability of PVC. For factorial design the optimum conditions were determined as 163.06 mg for ZnSt2, 399.99 mg for zeolite, and 140°C for temperature with desirability of 0.933. However, 400 mg for ZnSt2, 333.24 mg for zeolite, and 140°C for temperature with desirability of 0.956 were obtained as the optimum conditions by FCC design. © 2010 Wiley Periodicals, Inc
Macroscopic N-Halamine Biocidal Polymeric Beads

The particle size of N-halamine biocidal polymers was methodically modified forming beads of different sizes by blending water-insoluble N-halamine polyurethane with sodium alginate as the matrix and loading heterocyclic rings onto modified silica gels. The biological activity of the prepared beads and halogenated modified silica derivatives was evaluated against examples of Gram-positive (Staphylococcus aureus) and Gram-negative (Escherichia coli) bacteria. The recycling possibilities and the optimum preparation conditions of the blended beads were investigated; blending prehalogenated polyurethane (5%, w/v) with sodium alginate (3%, w/v) followed by crosslinking with CaCl2 (10%, w/v) at 40°C are the optimum preparation conditions for the alginate beads. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 201
The effect of anionic clay particles on the structure and thermomechanical behavior of sodium partially-neutralized EMAA ionomer

Electronic version of an article published as "Journal of Applied Polymer Science", Vol. 116, issue 5, p.2573–2579 (2010)Nanocomposites based on a sodium partially-neutralized ionomer of poly (ethylene-comethacrylic acid) (EMAA) and MgAl layered double hydroxide (LDH) particles with and without organic modification were prepared from a melt mixing process. The structure was characterized using X-ray diffraction analysis (XRD) and transmission electron microscopy (TEM). Although TEM micrographies revealed the presence of agglomerates of LDH sheets, the achievement of an exfoliated structure was observed when dodecyl sulphate-modified LDH particles were used. The effects of the LDH particles on the thermomechanical properties of EMAA were analyzed using differential scanning calorimetry (DSC) and dynamic mechanical thermal analysis (DMTA). The thermal transition of the ionic aggregates and dynamic mechanical response of EMAA were found strongly modified by these particles, resulting in an increase on the storage modulus and a decrease on the loss factor values. Moreover, the alpha relaxation of the composites was visibly shifted to higher temperaturesPreprin
Flocculation by Cationic Polyelectrolytes: Relating Efficiency with Polyelectrolyte Characteristics

A series of acrylamide/dimethylaminoethylacrylate
methyl chloride copolymers (AM-co-DMAEA) was evaluated as flocculants for model Precipitated Calcium Carbonate (PCC) in distilled water. These cationic polyelectrolytes
(PEL) differed by their AM/DMAEA ratio, i.e., their charge density, chain architecture (linear and branched), their intrinsic viscosity (IV), and zeta potential of their aqueous
solutions. The IV being directly related to the hydrodynamic volume of the PEL and the zeta potential reflecting the effective charge  in suspension were selected for practically
useful correlations with flocculation performance. The fractal dimension (dF) and the scattering exponent (SE) of the flocs, analyzed by the laser diffraction method, were
taken as indication of primary particle and aggregate assembly.
For the optimum PEL dosage, SE and dF varied with the IV and zeta potential. It was observable that floc size, floc resistance,
and floc reorganization correlate with the PEL characteristics.
Copolymers with lower IV, which is here
associated with PEL of similar molar mass but lower charge density, yielded larger and less resistant flocs. Copolymers with higher IV originated smaller more compact flocs being
more resistant. In high shear situations, where floc breakage should be avoided, as it is the case in papermaking, polymers with high IV yielding large SE are advantageous
Physico-Chemistry Characterization of Sulfonated Polyacrylamide Polymers for Use in Polymer Flooding

Hydrolyzed polyacrylamide polymer (HPAM) as a feasible and effective viscosifier has
been fully studied and used for polymer flooding processes in several oil field, e.g.
Daqing oil field. It has been shown that Hydrolyzed polyacrylamide polymers (HPAM)
may be a good choice for high temperature condition with no oxygen and no divalent
ions presence. At high temperature and high salinity conditions, polymer may precipitates
and loss their viscosyfing properties. Also adsorption and retention of polymer in porous
medium may change rheological properties of polymers. Thus, the viscosyfing property
of polymers is influenced by several important parameters, e.g. salinity, hardness,
temperature, adsorption, retention, polymer structure, and etc.
By replacing some of carboxylate group of HPAM with another monomer, e.g. sodium
salt of acrylic acid and 2-acrylamido-2-methylpropane sulfonic acid (AMPS), effect of
high salinity/hardness and temperature seems to be reduced specially for the samples with
higher percentage of AMPS co-monomer.
The ultimate aim of this work is to develop an understanding of the sulfonated
polyacrylamide copolymers with a range of different sulfonation and molecular weight at
high salinity and high temperature conditions. Most of the work in this thesis deals with
viscosity and adsorption/retention measurements of the sulfonated copolymers and
HPAM.
The factors which may affect the viscosity of the polymers and have been identified in
this work as most likely influencing also adsorption and retention of the polymers are
shear rate, polymer concentration, sulfonation degree, molecular weight, NaCl
concentration, divalent ion concentration, and temperature
Novel Hydrogels of PVP-CMC and Their Swelling Effect on Viscoelastic Properties

Polyvinylpyrolidon (PVP) a karboxymetylceluloza (CMC) byly použity na přípravu hydrogelu za tepla. Fyzikální charakteristiky byly studovány pomocí infračervené spektroskopie, skenovací elektronové mikroskopie. Výsledky ukazují, že hydrogel o kompozici 20/80 (PVP/CMC) má nejlepší vlastnosti.Polyvinylpyrrolidone (PVP) and carboxymethyl cellulose (CMC) mixed hydrogels were prepared by heat treatment. The physical characteristics of the hydrogels were studied by Fourier transform infrared spectroscopy and scanning electron microscopy. The swelling study of the hydrogels in water shows remarkable water absorption property. The swelling effect on the theological behavior of PVP-, PVP-CMC-, and CMC-based hydrogels was investigated to judge its application on uneven surface of body. The rheological properties (storage modulus, loss modulus, and complex viscosity) of samples before drying and swelled (15, 30, and 60 min) were measured against angular frequency and composition. The hydrogel containing PVP/CMC ratio of 20 : 80 appeared to be the best hydrogel from rheological and water absorbent points of view. These properties and low cost of the materials utilized in this work suggest that this hydrogel is a viable alternative product for dressing materials
Effect of corn-zein coating on the mechanical properties of polypropylene packaging films

In this study, a novel film structure of corn zein coated on polypropylene (PP) synthetic films for food packaging applications was developed, and the mechanical properties of the resulting coated film, as affected by the coating formulation, were investigated. Composite structures of PP films coated with corn zein were obtained through a simple solvent casting method. Different amounts of corn zein (5 and 15%) were dissolved in 70 and 95% aqueous ethanol solution at 50 C. Solutions of corn zein plasticized with poly(ethylene glycol) and glycerol (GLY) at various levels (20 and 50%) were applied on corona-discharge-treated PP. A statistical analysis based on full factorial design was performed to examine the influence of the coating formulation on the final properties of the corn-zein-coated PP films. A significant (p < 0.05) improvement in the coated film’s mechanical properties
was observed compared to those of the uncoated PP. The effect of the plasticization of the coating solutions was also quite significant. In general, GLY provided better improvements in the mechanical properties of the corn-zein-coated PP films. The statistical analysis of the results showed that the corn-zein and plasticizer concentrations and plasticizer type used in the coating formulations were more effective parameters and had significant effects on the mechanical behavior of the coated PP films. In conclusion, corn-zein coatings could have potential as alternatives to conventional synthetic polymers used in composite multilayer structures for food packaging applications
Metabolomic Profiling Can Differentiate Between Bactericidal Effects of Free and Polymer Bound Halogen

The effects of two halogenated compounds (sodium hypochlorite and N-halamine polymers) on the Escherichia coli metabolome were investigated. Changes in the intracellular metabolite pools of bacterial cells treated with different formulations of these compounds were analysed using FTIR (Fourier Transform Infra Red) spectroscopy and LC-MS (Liquid Chromatography-Mass Spectroscopy). Principal component analysis was used to generate metabolic profiles of the intracellular metabolites to investigate the effect of sublethal concentrations on the metabolome of treated cells. The effect of treatment with sodium hypochlorite was quantitatively dependent on the exposure time. The resulting metabolic profiles supported our previous hypothesis that the mode of action of some halogenated compounds, such as N-halamine polymers, can be initiated by release of halogen ions into the aqueous environment, in addition to direct contact between the solid polymer material and the bacterial cells. Moreover, the metabolic profiles were able to differentiate between the effect of free and polymer-bound halogen. Our metabolomic approach was used for hypothesis generation to distinguish apparently different bactericidal effects of free and polymer-bound halogen
Morphology, order, light transmittance, and water vapor permeability of aluminum-coated polypropylene zeolite composite films

In this study, the polypropylene-zeolite composite films having 2-6 wt % natural zeolite were coated with a thin film of aluminum (Al) by magnetron sputtering, and the contribution of the Al coating on film properties was investigated. The samples were characterized by EDX, X-ray diffraction, SEM, AFM, UV-visible spectroscopy, and water vapor permeation analyses. The surface of the films coated with a smooth Al film having 98-131 nm thickness. EDX revealed that Al percentage on the surface appeared to be as 8-10 wt % indicating contribution of polymer surface under Al film to analysis. XRD analysis showed that the grain size of Al at the surface was 22-29 nm. The surface roughness increased after Al-coating process. The transmission of coated films was very low for both UV and visible regions of the light spectrum. Permeation analysis indicated that water vapor permeation was lower for Al-coated material.State Planning Organization (2002K 120390
Synthesis and characterization of novel graft copolymers by radiation induced grafting

The radiation-induced graft copolymerization of N-vinyl-2-pyrrolidone (NVP), 4-vinyl pyridine (4VP), 2-vinyl pyridine (2VP) monomers onto poly (ethylene-alt-tetrafluoroethylene) (ETFE) was investigated. The influence of synthesis conditions particularly the solvent was studied. Various solvents, such as n-propanol, isoproponol, benzyl alcohol, methanol, ethanol, cyclohexanone, tetrahydrofuran (THF), nitromethane, 1,4-dioxane and n-heptane were examined for this purpose. Graft copolymers were characterized by Fourier transform infrared (FTIR) spectroscopy, dynamic mechanical analysis (DMA), and scanning electron microscopy-energy dispersive spectroscopy (SEM-EDAX). It was found that the nature of the solvent had profound influence over the grafting reaction. Cyclohexanone, n-propanol and isoproponol for 4VP/ETFE grafting, THF and 1,4-dioxane for NVP/ETFE grafting and benzyl alcohol and methanol for 2VP/ETFE grafting were found to be the suitable solvents yielding highest graft levels. Isoproponol and n-propanol are promising in terms of both graft level and mechanical properties for 4VP/ETFE. Grafting of NVP, 4VP and 2VP onto ETFE were verified through FTIR spectroscopy. Storage modulus and glass transition temperature of the copolymers were found to increase as graft level increased. Surface profile of representative films was also investigated by viewing the distribution of elemental nitrogen using SEM-EDAX. Results indicated that copolymers of 4VP, NVP and 2VP are considerably different from each other. 4VP based copolymers exhibited relatively more homogenous grafting over the surface compared to NVP and 2VP based copolymers
Biodegradable nanoparticles containing benzopsoralens : an attractive strategy for modifying vascular function in pathological skin disorders

Psoralens are often used to treat skin disorders such as psoriasis, vitiligo and others. The toxicity and fast degradation of these drugs can be diminished by encapsulation in drug delivery systems (DDS). Nanoparticles (NPs) containing the benzopsoralen (BP) (3-ethoxy carbonyl-2H-benzofuro[3,2-e]-1-benzopiran-2-one) were prepared by the solvent evaporation technique, and parameters such as particle size, zeta potential, drug encapsulation efficiency, and external morphology were evaluated. The analysis revealed that the NPs are spherical and possessed a smooth external surface with diameter of 815 ± 80 nm, they present low tendency toward aggregation, as confirmed by their zeta potential (+17.3±2.9 mV) and the encapsulation efficiency obtained was 74%. The intracellular distribution of NPs as well as their uptake by tissues was monitored by using laser confocal microscopy and transmission electron microscopy. The use of benzopsoralen in association with ultraviolet light (360 nm) revealed morphological characteristics of cell damage such as cytosolic vesiculation, mitochondria condensation, and swelling of both the granular endoplasmic reticulum and the nuclear membrane. The primary target of DDS and drugs in vascular system are endothelial cells and an attractive strategy for modifying vascular function in various pathological states of skin disorders, cancer and inflammation. The result presented in this work indicates that PLGA NP could be a promising delivery system for benzopsoralen in connection with ultraviolet irradiation therapy (PUVA) for further application in different therapies.CNPq , CAPES, FAPESP (Braisl