pinecone/core-2020-05-10-deduplication huggingface dataset:
Thermal and dynamic mechanical properties of vitamin E infused and blended ultra-high molecular weight polyethylenes

10 páginas, 10 figuras.Vitamin E (or α-tocopherol) is an alternative via to thermal treatments to achieve oxidative stability of gamma or electron beam irradiated ultra-high molecular weight polyethylenes (UHMWPE) used in total joint replacements. Our aim was to study the effects of vitamin E on the molecular dynamics and microstructural properties of UHMWPE. We hypothesized that the antioxidant would plasticize UHMWPE. Vitamin E was incorporated into UHMWPE at different concentrations by diffusion and blending and detected by ultraviolet and infrared spectroscopies from 500 ppm and 4000 ppm, respectively. Dynamic mechanical thermal analysis was used to characterize the influence of this antioxidant in the relaxations of the raw material. Differential scanning calorimetry and transmission electron microscopy served to characterize thermal and microstructure properties, respectively. Vitamin E concentrations above 3% by weight significantly reduced the degree of crystallinity and increased the melting transition temperature of raw UHMWPE. The presence of increasing concentrations of α-tocopherol introduced and/or strengthened the beta relaxation, which was also shifted toward gradually lower temperatures and had rising activation energies up to 188 kJ/mol. In addition, the gamma relaxation remained unaltered on vitamin E addition. Therefore, no plasticizing effects of vitamin E on the molecular dynamics of UHMWPE could be confirmed from mechanical spectroscopy data. However, the α relaxation was modified in intensity and location due to the changes in the degree of crystallinity introduced by the incorporation of vitamin E.Contract grant sponsor: Comisión Interministerial de\ud
Ciencia y Tecnología (CICYT), Spain.\ud
Contract grant sponsor: Ministerio de Ciencia e\ud
Innovación; contract grant number: MAT 2006-12603-C02-\ud
01 and Consolider-Ingenio CDS2008-0023.Peer reviewe
On the structure-properties relationship in montmorillonite-filled polyamide 6 nanocomposites

Polyamide 6/montmorillonite (MMT) nanocomposites were prepared by melt compounding method comprising 1–7.5 wt % of Nanomer I.24 TL or 5 and 10 wt % of Cloisite 15A organically modified nanoclays. The composite samples were characterized by synchrotron X-ray, thermal and FT-IR spectroscopy methods looking for changes in the micro- and nanostructure of both PA6 matrix and MMT reinforcement as a function of the clay content and type. These data were discussed in conjunction with the mechanical properties of the respective nanocomposites. Generally, the Young’s modulus was found to increase proportionally to the clay content being the highest in samples with strong aggregation of MMT at micron length scale. The tensile strength passed through a maximum at 2.5 wt % clay load presenting a homogeneous microstructure with almost no agglomeration. Increasing the amount of MMT produced less crystalline PA6 matrices, richer in gamma-PA6 polymorph and resulted in larger long spacings of PA6 due to expansion of both crystalline and amorphous domains.Fundação para a Ciência e a Tecnologia (FCT), Portugal; HASYALb at DESY, Hamburg, German
Properties of n-eicosane-loaded silk fibroin-chitosan microcapsules

PCM microcapsules containing n-eicosane were prepared by complex coacervation of silk fibroin (SF) and chitosan (CHI). Chemical characterization of microcapsules was carried out using Fourier-transform infrared (FT-IR) spectroscopy. Thermal properties and thermal stability of microencapsulated n-eicosane were determined by differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA). FTIR spectra confirmed the encapsulation of n-eicosane within the microcapsules. Results from thermal analyses showed that microcapsules consisted of an average of 45.7 wt % n-eicosane, and had a thermal energy storage and release capacity of about 93.04 J/g and 89.68 J/g, respectively.Ege University Research Foundation (08-MUH-042
Tuning the thermoresponsive properties of Hyperbranched Poly(ester amide)s based on diisopropanolamine and cyclic dicarboxylic anhydrides

‘This is the peer reviewed version of the following article: Kelland, M. (2011) Tuning the Thermoresponsive Properties of
Hyperbranched Poly(ester amide)s Based on Diisopropanolamine and Cyclic
Dicarboxylic Anhydrides. Journal of Applied Polymer Science, 121(4),
2282-2290, which has been published in final form at doi: 10.1002/app.33942. This article may be used for non-commercial purposes in accordance With Wiley Terms and Conditions for self-archiving.A range of water-soluble hyperbranched poly(ester amide)s has been synthesized with a view to studying their
thermoresponsive behavior in water. Poly(ester amide)s with lower critical solution temperature (LCST) values around
physiological temperatures are of interest for biological and medical applications, whereas poly(ester amide)s with high
LCST values may be useful as kinetic hydrate inhibitors for high salinity produced fluids in the oil and gas industry. The
LCST of these polymers was measured as the optical cloud point. The LCST can be tuned in various ways for these
applications, for example, by varying the hydrophobicity of the groups on the cyclic anhydride monomer or by adjusting
the hydrophilicity of the imine used to make the peripheral groups of the polymer
Two advanced styrene-butadiene/polybutadiene rubber blends filled with a silanized silica nanofiller for potential use in passenger car tire tread compound

This is the peer reviewed version of the following article: Journal of Applied Polymer Science, which has been published in final form at http://dx.doi.org/10.1002/app.34221. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving.Styrene-butadiene rubber (SBR) and poly-\ud
butadiene rubber (BR) were mixed together (75:25 by\ud
mass) to produce two SBR/BR blends. The blends were re-\ud
inforced with a precipitated amorphous white silica nano-\ud
filler the surfaces of which were pretreated with bis(3-\ud
triethoxysilylpropyl)-tetrasulfide (TESPT). TESPT is a sul-\ud
fur-bearing bifunctional organosilane that chemically\ud
bonds silica to rubber. The rubbers were primarily cured\ud
by using sulfur in TESPT and the cure was optimized by\ud
adding non-sulfur donor and sulfur donor accelerators\ud
and zinc oxide. The hardness, Young’s modulus, modulus\ud
at different strain amplitudes, tensile strength, elongation\ud
at break, stored energy density at break, tear strength,\ud
cyclic fatigue life, heat build-up, abrasion resistance, glass\ud
transition temperature, bound rubber and tan d of the\ud
cured blends were measured. The blend which was cured\ud
with the non-sulfur donor accelerator and zinc oxide had\ud
superior tensile strength, elongation at break, stored\ud
energy density at break and modulus at different strain\ud
amplitudes. It also possessed a lower heat build-up, a\ud
higher abrasion resistance and a higher tan d at low tem-\ud
peratures to obtain high-skid resistance and ice and wet-\ud
grip. Optimizing the chemical bonding between the rubber\ud
and filler reduced the amount of the chemical curatives by\ud
approximately 58% by weight for passenger car tire tread.\ud
This helped to improve health and safety at work and\ud
reduce damage to the environment
Functionalization of wool with L-cysteine : process characterization and assessment of antimicrobial activity and cytotoxicity

This investigation reports a new biotechnological process that uses L-cysteine (L-Cys) which provides a permanent, nontoxic and effective antimicrobial effect over wool-based materials. This process is simple and carried out via idespread exhausting methods. Typically, wool fabrics are incubated with L-Cys for 50 min at 60°C in a pH 4.8 acetate buffer solution 25 mM, under mild agitation to give a good absorption rate. The minimal inhibitory concentration (MIC) of L-Cys was evaluated by the NCCLS M07-A6 standard method, and the results showed a good antibacterial activity against S. aureus and K. pneumoniae within the range of 6.0 × 10−3 − 4.8 × 10−2 g/mL [MIC 0.6% (w/v)] and 6.0 × 10−3 − 4.8 × 10−2 g/mL [MIC 0.6% (w/v)], respectively. In addition, the antimicrobial activity of the functionalized wool was assessed by the international standard JIS 1902-2002 showing a good inhibition of bacterial growth for an L-Cys concentration of 1% over the weight of fabric, both against Staphylococcus aureus and Klebsiella pneumoniae. Moreover, the biocidal mechanism was found to be related with the increase of sulfhydryl's groups onto wool fibers, which were quantified by the Ellman's reagent (5,5′-Dithio-bis(2-nitrobenzoic acid) method. The new process is easy to perform, non toxic, preserve wool quality and is a novel biomimetic approach that uses antimicrobial amino acids and may open new avenues for the design of biomedical textiles with a broad range of applications in healthcare.Contract grant sponsor: FCT; contract grant number: PTDC/EBB-BIO/113671/2009.Contract grant sponsor: R and D Unit of Textile and Paper Materials, Faculty of Engineering, University of Beira Interior
Compatibilization of polypropylene/poly(3-hydroxybutyrate) blends

Blending polypropylene (PP) with biodegradable poly(3-hydroxybutyrate) (PHB) can be a nice alternative to minimize the disposal problem of PP and the intrinsic brittleness that restricts PHB applications. However, to achieve acceptable engineering properties, the blend needs to be compatibilized because of the immiscibility between PP and PHB. In this work, PP/PHB blends were prepared with different types of copolymers as possible compatibilizers: poly(propylene-g-maleic anhydride) (PPMAH), poly (ethylene-co-methyl acrylate) [P(EMA)], poly(ethylene-co-glycidyl methacrylate) [P(EGMA)], and poly(ethylene-co-methyl acrylate-co-glycidyl methacrylate) [P(EMAGMA)]. The effect of each copolymer on the morphology and mechanical properties of the blends was investigated. The results show that the compatibilizers efficiency decreased in this order: P(EMAGMA) &gt; P(EMA) &gt; P(EGMA) &gt; PP-MAH; we explained this by taking into consideration the affinity degree of the compatibilizers with the PP matrix, the compatibilizers properties, and their ability to provide physical and/or reactive compatibilization with PHB. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci 123: 3511-3519, 2012Fundacao de Amparo a Pesquisa do Estado de Sao PauloCoordenacao de Aperfeicoamento de Pessoal de Nivel SuperiorConselho Nacional de Desenvolvimento Cientifico e Tecnologico (Brazil
Sulphonated Poly Ether Ether Ketone/Aminodiphenylsilandiol\ud
Composite Electrolyte for\ud
PEM Fuel Cells

A composite polymeric membrane to be\ud
used as electrolyte in polymer electrolyte membrane fuel\ud
cells has been prepared and characterized. The membrane\ud
is composed of an acidic polymer, sulfonated polyetheretherketone,\ud
and of basic filler, amino-diphenylsilandiol,\ud
a functionalized organically modified silane. Attenuated\ud
total reflectance (ATR)/fourier transform infrared spectroscopy\ud
(FTIR) demonstrated the occurrence of a specific\ud
interaction of the polymer ASO3H groups with the basic\ud
function of the filler. Such interaction reflected in reduced\ud
swelling, enhanced thermal stability, and good proton conductivity\ud
values at intermediate temperatures (r   10\ud
 2 S\ud
cm\ud
 1 at 100 C)
Measuring effect of the blooming of chemical curatives on the rate of cyclic fatigue crack growth in natural rubber filled with a silanized silica nanofiller

This is the peer reviewed version of the following article: SAEED, F. ... et al., 2012. Measuring effect of the blooming of chemical curatives on the rate of cyclic fatigue crack growth in natural rubber filled with a silanized silica nanofiller. Journal of Applied Polymer Science, 124 (2), pp.1372-1383, which has been published in final form at: http://dx.doi.org/10.1002/app.34913. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving.Two rubber compounds with different amounts of chemical curatives were prepared by mixing natural rubber with a high loading of a sulfur-bearing silanized precipitated amorphous white silica nanofiller. The chemical bonding between the filler and rubber was optimized via the tetrasulfane groups of the silane by adding a sulfenamide accelerator and zinc oxide. The rubber compounds were cured and stored at ambient temperature for 65 days before they were tested. One compound showed extensive blooming as a function of storage time. Thin tensile strips of the rubber vulcanizates containing an edge crack were repeatedly stressed at constant strain amplitude and test frequency at ambient temperature and crack length c was measured as a function of the number of cycles n. The cut growth per cycle, dc/dn, was calculated and plotted against the tearing energy, T. The blooming of the chemical curatives increased dc/dn by up to an order of magnitude at a constant T. This was due to the reagglomeration of the chemical curatives in the rubber and also within a thin layer approximately 15 to μm in size beneath the rubber surface. Under repeated stressing, cracks grew through the relatively weak agglomerated areas in the rubber and this caused the rate of crack growth to increase at a constant T
Polyacrylonitrile-based electrospun carbon paper for electrode applications

Polyacrylonitrile (PAN)-based carbon paper with fiber diameters of 200–300 nm was developed through hot-pressing, pre-oxidation, and carbonization of electrospun fiber mats. Changes in morphology, crystallinity, and surface chemistry of the hot-pressed carbon paper were investigated. More junctions between fibers were formed with increasing hot-press time, which is attributed to melting and bonding of fibers. The bulk density increased to 0.5–0.6 g/cm[superscript 3], which could help to improve the volume energy density for electrode applications. The conductivity of the carbon paper was found to be about 40 S/cm when the surface area was ∼ 2 m[superscript 2]/g, and depends not only on the conductivity of the individual nanofibers but also on the contacts between the nanofibers. The performance of the electrospun carbon paper as an electrode for electrochemical reactions involving ferrocene molecules was affected by the preparation protocol: the higher surface area of the electrodes formed with shorter hot-press times provided a higher current generated per unit mass than that obtained with electrodes prepared using longer hot-press time, but electrodes prepared with longer hot-press times exhibited higher electrical conductivity and faster electron transfer kinetics
Preparation and characterization of flexible poly(vinyl chloride) foam films

In this study, the effect of activator ZnO and heating time at 190°C on foaming, gelation, and dehydrochlorination of poly(vinyl chloride) (PVC) plastisol was investigated. For this purpose, a PVC plastisol was prepared by mixing PVC, dioctyl phthalate (DOP), azodicarbonamide (ADC), ZnO, and the heat stabilizers calcium stearate (CaSt 2) and zinc stearate(ZnSt 2). PVC plastisol films were heated for 3, 6, 12, and 24 min periods at 190°C to see the effect of heating time on the gelation and foaming processes of the PVC foam. The time of 12 min was determined to be optimum for the completion of gelation and foaming processes without thermal degradation of PVC. No foaming was observed under the same conditions for the samples without ZnO. ZnO had a significant catalytic effect on ADC decomposition, accelerating the foaming of the films. Average porosity measurement showed a consistent increase in porosity with heating time up to 76% and the average density decreased from 1.17 to 0.29 g/cm 3 on foaming. Tensile tests showed that the tensile strength and tensile strain both increased considerably up to 0.98 MPa and 207%, respectively, with heating time and the elastic modulus was seen to gradually decrease from 4.7 to 0.7 MPa with heating time. Films without ZnO had higher tensile strength since there were no pores. PVC thermomat tests showed that ZnO lowered the stability time of plastigel film with azodicarbonamide
Influence of acrylic fibers geometry on the mechanical performance of fiber-cement composites

This article analyses the influence of acrylic
fibers shape on the flexural behavior of cement composite. The fibers differ in their cross-sectional shapes due to the spinning process (wet-spun and dry-spun). The fibers
were characterized by optical microscopy, and the shape factors were calculated on the basis of their geometric characteristics. Results showed that both types of acrylic
fiber remarkably improved the flexural performance of the composites. Wet-spun acrylic fibers lead to high flexural strength and toughness. It was found that by increasing the fibers’ shape factor by a factor of 10%, flexural strength and toughness increase to 26% and 23%, respectively
The Role of Oxidation Compounds in Biofilm Growth on Polyethylene Geomembrane Barriers Used in Landfill

In a model study, polyethylene was preoxidized and incubated for a period of 7 months at 40°C in two different municipal solid waste leachates. During the postexperimental analyses, specific attention was paid to the carbonyl species and carboxylic acid depletion during the environmental exposure because it is well known that carboxylic acids are believed to be a potential substrate for the development of microorganisms. The results showed that the carbonyl as well as the carboxylic acid depletion observed follows first-order kinetics. The biofilm formation was characterized using a suite of analytical techniques, and its formation was compared with the carboxylic acid and carbonyl depletion profil
Fatigue Damage Initiation of a PA66/Glass Fibers Composite Material

Fatigue damage initiation of a PA66/glass fiber composite material is studied with interrupted tests carried out with an “alternative bending device” and a small applied strain. During the damage initiation period, no change of macroscopic properties, density, cristallinity ratio, glass transition temperature, and flexural elastic modulus is observed. Polysequential tests are carried out with three rest times differing by their length. These rest times allow the relaxation of macromolecular chains in the region of the microdefects and increase the number of cycles at fracture. The most efficient stop is the one just before the final fracture. The comparison of the fatigue behavior of the composite and its neat matrix shows that the microdefects relaxed during the break are identical to those which initiate damage and final fracture
Investigation of the effect of double-walled carbon nanotubes on the curing reaction kinetics and shear flow of an epoxy resin

In this article, the effect of combined temperature-concentration and shear rate conditions on the rheology of double-walled carbon nanotubes (DWCNTs)/RTM6-Epoxy suspension was investigated to determine the optimum processing conditions. The rheological behavior and cure kinetics of this nanocomposite are presented. Cure kinetics analysis of the epoxy resin and the epoxy resin filled with DWCNTs was performed using Differential Scanning Calorimeter (DSC) and parameters of the kinetics model were compared. The DWCNTs have an acceleration effect on the reaction rate of the epoxy resin but no significant effect is noted on the glass transition temperature of the epoxy resin. This study reveals that the effect of shear-thinning is more pronounced at high temperatures when DWCNTs content is increased. In addition, the steady shear flow exhibits a thermally activated property above 60°C whereas the polymer fluid viscosity is influenced by the free volume and cooperative effects when the temperature is below 60°C
Synthesis, Characterization and Thermal Properties of Alkyl-functional Naphthoxazines

Cataloged from PDF version of article.A series of alkyl-functional naphthoxazine resins having various alkyl chain lengths from C1 to C18 are synthesized with a high yield and high purity by the reactions of 1,5-dihydroxynaphthalene, formaldehyde, and aliphatic amines. The proposed chemical structures of the naphthoxazines are confirmed by high-resolution mass spectrometry, H-1 nuclear magnetic resonance spectroscopy, Fourier transform infrared spectroscopy, and pyrolysis mass spectrometry studies. The alkyl-functional naphthoxazines have shown low polymerization temperature characteristics where polymerization of these monomers is achieved in the range of 150-170 degrees C yielding cross-linked polynaphthoxazines. The low-temperature polymerization characteristics and the associated thermal degradation behaviors are studied. (C) 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 127: 3114-3123, 201
Similarity and grouping of perlite and zeolite abrasive fillers. A replacement test

Inverse Gas Chromatography was used to estimate surface activity expressed by the\ud
dispersive component of the surface free energy, D\ud
S g , as well as parameters KA and KD\ud
describing surface ability to act as electron acceptor and donor, respectively. These\ud
parameters characterize the ability of the surface to specific interactions. The method was also\ud
applied to describe the magnitude of filler-phenolic resin interaction by Flory-Huggins\ud
parameter, . Granulation, surface area and porosity were also determined.\ud
The minimum number of parameters required to complete characterization of filler\ud
properties has been selected by principal component analysis. The usefulness of the selection\ud
for the abrasive industry has been proven. Moreover, the similarities and deviations from “an\ud
average” filler was determined by chemometric methods.\ud
Principal component analysis (PCA) and a novel procedure based on sum of ranking\ud
differences (SRD) were successfully applied for selection of the best fillers, and of\ud
advantageous parameters for characterization of the fillers. Similar and diverse fillers have\ud
been chosen based on clustering pattern by PCA and SRD
A new insight into interface widths in binary polymer blends based on ortho-positronium lifetime studies.

The interface widths in two immiscible polymer blend Poly vinyl chloride (PVC)/Polystyrene (PS) and PVC/Ethylene Vinyl Acetate (EVA) are detd. exptl. using hydrodynamic interaction approach through free vol. measurement by positron annihilation lifetime spectroscopy.  For comparison, the same study is performed in a miscible blend Styrene Acrylonitrile copolymer (SAN)/Poly Me Methacrylate (PMMA).  The interfacial width (Î”l) is evaluated from the hydrodynamic interaction (Î±) based on Kirkwood-Risemann theory and friction coeff. from Stokes equation.  Friction at the interface of a binary blend evidences how close the surfaces of the polymer chains come or stay apart which in turn depends on the type of force/interaction at the interface.  In this work, we define interface width from a different perspective of Flory-Huggins interaction approach.  Measured compn. dependent interface widths in the three blends studied clearly demonstrate the sensitivity of the present method.  In miscible blend, high friction at the interface results in stronger hydrodynamic interaction and hence smaller interface widths (0.36-1.97 Ã…), whereas weak or no interaction in immiscible blends produce wider widths (2.81-25.0 Ã…). Â© 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2012. [on SciFinder(R)