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1.
Acta Obstet Gynecol Scand ; 101(2): 241-247, 2022 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-35049047

RESUMO

INTRODUCTION: In this feasibility study, we hypothesize that the evaluation of cervical biomechanical strength can be improved if cervical length measurement is supplemented with quantitative elastography, which is a technique based on conventional ultrasound elastography combined with a force-measuring device. Our aims were to: (a) develop a force-measuring device; (b) introduce a cervical elastography index (CEI) and a cervical strength index (CSI; defined as cervical length × CEI); (c) evaluate how these indexes assess the cervical softening that takes place during normal pregnancy; and (d) how these indexes predict the cervical dilatation time from 4 to 10 cm. MATERIAL AND METHODS: An electronic force-measuring device was mounted on the handle of the transvaginal probe, allowing for force measurement when conducting elastography. The study group concerned with normal cervical softening included 44 unselected pregnant women. Outcomes were CEI and CSI at different gestational ages. The study group for labor induction included 26 singleton term pregnant women admitted for labor induction. Outcome was defined as cervical dilatation time from 4 to 10 cm. Elastography measured the changes in mean gray value (intensity) during manual compressions. Region of interest was set within the anterior cervical lip. RESULTS: We found that the mean of all variables regarding cervical softening decreased from early to late pregnancy: ie cervical length from 34 to 29 mm, CEI from 0.17 to 0.11 N, and CSI from 5.9 to 3.1 N mm. Moreover, the cervical dilatation time during labor induction was associated with CEI, although not statistically significantly (area under the ROC curve of 0.67), but not with the Bishop score, the cervical length, or the CSI. CONCLUSIONS: We propose that quantitative elastography based on changes in the intensity of the B-mode ultrasound recording, in combination with a force-measuring device on the handle of the vaginal probe, deserves further investigation as an approach for evaluation of cervical biomechanical strength.


Assuntos
Colo do Útero/fisiologia , Técnicas de Imagem por Elasticidade/instrumentação , Ultrassonografia Pré-Natal , Adolescente , Adulto , Colo do Útero/diagnóstico por imagem , Desenho de Equipamento , Feminino , Idade Gestacional , Humanos , Recém-Nascido , Valor Preditivo dos Testes , Gravidez , Trimestres da Gravidez , Nascimento Prematuro , Adulto Jovem
2.
Acta Obstet Gynecol Scand ; 100(10): 1814-1821, 2021 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-34255864

RESUMO

INTRODUCTION: Vaginal colonization with Streptococcus agalactiae (group B streptococci) is hypothesized to constitute a risk factor for preterm prelabor rupture of membranes. In vitro studies have shown that S. agalactiae strains isolated from infants with neonatal sepsis adhere to chorion cells of the human chorioamniotic membrane. However, it is still unknown whether S. agalactiae strains penetrate the chorioamniotic membranes and whether S. agalactiae colonization affects the biomechanical properties of the membranes and thus contributes to increased risk of preterm prelabor rupture. The aim of this in vitro study was to explore if different strains of S. agalactiae penetrate and affect the biomechanical properties of human chorioamniotic membranes. MATERIAL AND METHODS: Three different strains of S. agalactiae were obtained, one from an early-onset neonatal infection, one from a case of preterm prelabor rupture of membranes and one from a healthy pregnant carrier. Chorioamniotic membranes from elective cesarean deliveries were either incubated with S. agalactiae or mounted in a two-chamber incubation cell generating a "maternal" and a "fetal" chamber and incubated with S. agalactiae in the maternal chamber. Subsequently the membranes were examined to evaluate S. agalactiae attachment, penetration and the effect on the biomechanical properties. RESULTS: At 5 h after incubation, S. agalactiae adhered to the chorioamniotic membranes with increased number at 20 h. Streptococcus agalactiae did not penetrate the membranes even after 20 h of incubation. Streptococcus agalactiae increased the ultimate tensile stress needed to rupture the membranes and increased the work needed to rupture the membranes as well as the elastic modulus. CONCLUSIONS: Human chorioamniotic membranes constitute a physical barrier against S. agalactiae infections. Moreover, S. agalactiae infection leads to increased strength of the membranes.


Assuntos
Córion/microbiologia , Ruptura Prematura de Membranas Fetais/microbiologia , Complicações Infecciosas na Gravidez , Infecções Estreptocócicas , Streptococcus agalactiae/patogenicidade , Feminino , Humanos , Técnicas In Vitro , Gravidez
3.
Appl Microbiol Biotechnol ; 104(1): 365-375, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31768610

RESUMO

Microbially induced CaCO3 precipitation (MICP) can give concrete self-healing properties. MICP agents are typically bacterial endospores which are coated into shelled granules, infused into expanded clay, or embedded into superabsorbent polymer (SAP). When small cracks appear in the cured concrete, the encapsulation is broken and the metabolic CO2 production from the germinated bacteria causes healing of the cracks by precipitation of CaCO3. Such systems are being tested empirically at large scales, but survival of endospores through preparation and application, as well as germination and growth kinetics of the germinated vegetative cells, remains poorly resolved. We encapsulated endospores of Bacillus subtilis and Bacillus alkalinitrilicus in crosslinked acrylamide-based SAP and quantified their germination, growth, and, in the case of B. alkalinitrilicus, CaCO3 precipitation potential. The endospores survived crosslinking and desiccation inside the polymer matrix. Microcalorimetry and microscopy showed that ~ 80% of the encapsulated endospores of both strains readily germinated after rehydration of freeze-dried SAP. Germinated cells grew into dense colonies of cells inside the SAP, and those of B. alkalinitrilicus calcified with up to 0.3 g CaCO3 produced per g desiccated SAP when incubated aerobically. Measurements by planar optodes indicated that the precipitation rates were inherently oxygen limited due to diffusional constraints, rather than limited by electron donor or Ca2+ availability. Such oxygen limitation will limit MICP in all water-saturated and oxygen-dependent systems, and MICP agents based on anaerobic bacteria, e.g., nitrate reducers, should be developed to broaden the applicability of bioactive self-healing concretes to wet and waterlogged environments.


Assuntos
Bacillus subtilis/metabolismo , Bacillus/metabolismo , Carbonato de Cálcio/metabolismo , Precipitação Química , Polímeros/química , Acrilamida/química , Bacillus/crescimento & desenvolvimento , Bacillus subtilis/crescimento & desenvolvimento , Bactérias Aeróbias/crescimento & desenvolvimento , Bactérias Aeróbias/metabolismo , Fenômenos Bioquímicos , Dióxido de Carbono/metabolismo , Oxigênio/metabolismo , Esporos Bacterianos/metabolismo , Água/metabolismo
4.
Spectrochim Acta A Mol Biomol Spectrosc ; 311: 123984, 2024 Apr 15.
Artigo em Inglês | MEDLINE | ID: mdl-38320471

RESUMO

The extensive use of aluminium trihydrate (ATH) flame retardant in plastics poses challenges and hazards in plastic waste recycling, thus it is crucial to accurately identify ATH. This study demonstrates the effectiveness of an industrial in-line shortwave infrared (SWIR) hyperspectral imaging system and principal component analysis (PCA) for detecting and quantifying ATH in low-density polyethylene (LDPE) and polypropylene (PP). The samples were characterized by elemental analysis, ATR-FTIR, DSC, and TGA. A quantitative estimation model was developed by analysing spectra with varying ATH concentrations. PCA and SWIR band area ratio were fitted to estimate the ATH concentration. The PCA model outperformed the SWIR band area ratio model and achieved good predictions between measured and predicted ATH concentrations ranging from 22.9 to 1.6 wt% (R2LDPE = 0.95) in LDPE and from 24.0 to 2.5 wt% in PP (R2PP = 0.94). The obtained in-line control tool is relevant to the recycling industries, enabling real-time assessment of additives.

5.
Langmuir ; 29(11): 3791-6, 2013 Mar 19.
Artigo em Inglês | MEDLINE | ID: mdl-23421711

RESUMO

We describe for the first time the electro-oxidative synthesis and passivating properties of surface films of poly(allylamine) and copolymers of allylamine and diallylamine. Cyclic voltammetry and impedance spectra show that the films exhibit high charge-transfer resistance and that the addition of diallylamine causes improvements in the compactness and stability toward swelling of the films when compared to both allylamine and diallyamine, leading to coatings with high charge-transfer resistance up to 70 MΩ. We also show that removing oxygen before the polymerization further improves the films' passivating properties.


Assuntos
Alilamina/química , Polimerização , Eletroquímica , Oxigênio/química , Poliaminas/química
6.
Sci Total Environ ; 895: 165154, 2023 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-37385513

RESUMO

Plastics underpin modern society but also threaten to choke it. Only 9 % of all plastic waste is recycled, usually with loss of quality ("downcycling"); the rest is landfilled or dumped (79 %) or incinerated (12 %). Put bluntly, the "plastic age" needs a "sustainable plastic culture." Consequently, we urgently need to develop a global and transdisciplinary approach not only to fully recycle plastics but also to manage the harms across their life cycle. The past decade has witnessed an explosion in research on new technologies and interventions that purport to help solve the plastic waste challenge; however, this work has, in most cases, been carried forward within single disciplines (for example, researching novel chemical and bio-based technologies for plastic degradation, engineering processing equipment innovations, and mapping recycling behaviours). In particular, although there has been vast progress within individual scientific fields, such work does not address the complexities of various plastic types and waste management systems. Meanwhile, research on the social contexts (and constraints) of plastic use and disposal is rarely in conversation with the sciences to drive innovation. In short, research on plastics typically lacks a transdisciplinary perspective. In this review, we urge the adoption of a transdisciplinary approach that focuses on pragmatic melioration; such an approach combines the natural and technical sciences with the social sciences to focus on the mitigation of harms across the plastic life cycle. To illustrate our case, we review the status of plastic recycling from these three scientific perspectives. Based on this, we advocate 1) foundational studies to identify sources of harm and 2) global/local interventions aimed at those plastics and aspects of the plastic life cycle that cause maximal harm, both in terms of planetary welfare and social justice. We believe this approach to plastic stewardship can be a showcase for tackling other environmental challenges.


Assuntos
Plásticos , Gerenciamento de Resíduos , Redução do Dano , Reciclagem , Tecnologia
7.
Waste Manag ; 170: 1-7, 2023 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-37531740

RESUMO

Due to developments in European legislation, several halogenated flame retardants are banned due to their toxicity, and the use of phosphor-based flame retardants in plastics is increasing. A revision of ammonium polyphosphate (APP) flame retardant revealed that it is an eye irritant and toxic, thus posing a health issue. Hence APP identification is needed for enabling safe recycling of plastic waste streams. Herein an industrial in-line method for quantitative estimation of APP in low density polyethylene (LDPE) and polypropylene (PP) is demonstrated, by using an industrial hyperspectral imaging system (955 to 1700 nm) and principal component analysis (PCA). Spectra of plastic samples with varying concentrations of APP were applied to build and calibrate a quantitative determination method. PCA and band area ratios (of selected bands) were made and fitted with continuous functions for concentration determination. The plastic samples were characterised by elemental analysis, attenuated total reflection, differential scanning calorimetry, and thermogravimetric analysis. The PCA model outperforms the band area ratio model and predicts APP concentrations between 24.3 and 1.5 wt% in LDPE (R2 = 0.98) and 20.0 and 1.7 wt% in PP (R2 = 0.97). Unknown samples with APP ranging from 23.7 to 2.7 wt% in LDPE and from 18.6 to 2.3 wt% in PP were predicted and correlated to the actual concentrations. The proposed approach is valuable for the plastic recyclers and waste management industries where inline concentration determination of flame retardants is key.

8.
Mar Pollut Bull ; 191: 114910, 2023 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-37062129

RESUMO

Fishing lines, nets, and ropes represent a significant portion of plastic pollution in marine environments, and can contain hazardous additives. The development of less laborious and faster methods aiming at identifying plastic-related additives is therefore needed, in order to facilitate effective recycling. This work aims to develop an industrial inline method to identify lead-based pigments in fishnets by an industrial hyperspectral imaging (HSI) system working in visible-near-infrared spectral range (Vis-NIR, 450 to 1050 nm) and machine learning. A Vis-NIR spectral sample set comprising un-contaminated and lead contaminated (143 to 2430 mg L-1) plastic classes were used to build the classification model via Principal Component Analysis and clustering. The content of the samples was characterized by X-ray fluorescence (XRF), Attenuated Total Reflection (ATR-FTIR), differential scanning calorimetry, thermogravimetric analysis, and burning in astmospheric air. Fishnets containing lead-based pigments with lead concentrations > 1000 mg L-1 (0.1 wt%) were accurately identified by the industrial HSI, and the lead content was corroborated with ATR-FTIR and XRF measurements. In addition, lead contaminated plastic area and mass can be estimated via calibration curve using the pixels numbers vs mass of fibrous plastics with a detectability of 120 mg (R2 = 0.997).


Assuntos
Imageamento Hiperespectral , Chumbo , Caça , Plásticos , Aprendizado de Máquina
9.
Sci Rep ; 13(1): 22399, 2023 Dec 16.
Artigo em Inglês | MEDLINE | ID: mdl-38104201

RESUMO

Several optical spectroscopy and imaging techniques have already proven their ability to identify different plastic types found in household waste. However, most common optical techniques feasible for plastic sorting, struggle to measure black plastic objects due to the high absorption at visible and near-infrared wavelengths. In this study, 12 black samples of nine different materials have been characterized with Fourier-transform infrared spectroscopy (FTIR), hyperspectral imaging, and terahertz time-domain spectroscopy (THz-TDS). While FTIR validated the plastic types of the samples, the hyperspectral camera using visible and near-infrared wavelengths was challenged to measure the samples. The THz-TDS technique was successfully able to measure the samples without direct sample contact under ambient conditions. From the recorded terahertz waveforms the refractive index and absorption coefficient are extracted for all samples in the range from 0.4 to 1.0 THz. Subsequently, the obtained values were projected onto a two-dimensional map to discriminate the materials using the classifiers k-Nearest Neighbours, Bayes, and Support Vector Machines. A classification accuracy equal to unity was obtained, which proves the ability of THz-TDS to discriminate common black plastics.

10.
J Matern Fetal Neonatal Med ; 36(1): 2213797, 2023 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-37202178

RESUMO

OBJECTIVE: During pregnancy, the stiffness of the cervical tissue decreases long before the cervical length decreases. Therefore, several approaches have been proposed in order to ensure a more objective assessment of cervical stiffness than that achieved by digital evaluation. Strain elastography has shown promising results. This technique is based on an ultrasound assessment of the tissue deformation that occurs when the examiner applies pressure on the tissue with the ultrasound probe. However, the results are only semi-quantitative as they depend on the unmeasured force used by the examiner. We, therefore, hypothesized that a force-measuring device applied to the handle of the ultrasound probe may render the technique quantitative. With this approach, the stiffness is the force (measured by the device) divided by the compression (measured by the elastography platform). One perspective is the early identification of women at risk of preterm birth in whom cervical stiffness may decrease long before cervical shortening. Another perspective is cervical evaluation when planning labor induction. In this feasibility study, we aimed to evaluate how quantitative strain elastography performs when a commercially available strain elastography platform (by which the algorithm is unavailable) is combined with a custom-made, force-measuring device. We studied how the assessments were associated with the gestational age in women with uncomplicated pregnancies and how they were associated with cervical dilatation time from 4 to 10 cm in women undergoing labor induction. METHODS: In the analysis, we included quantitative strain elastography assessments from 47 women with uncomplicated singleton pregnancies, with gestational age between 12+0 and 40+0, and from 27 singleton term-pregnant women undergoing labor induction. The force-measuring device was mounted on the handle of a transvaginal probe. The strain values (i.e. the compression of the cervical tissue) were obtained by the elastography software of the ultrasound scanner (GE Voluson E10). The region of interest was placed within the central part of the anterior cervical lip. Based on the force data and strain values, we calculated the outcomes cervical elastography indexGE (CEIGE) and the cervical strength indexGE (CEIGE x cervical length: CSIGE). RESULTS: The average CEIGE was 0.24 N at week 12 and 0.15 N at week 30-34. For CSIGE these figures were 8.2 and 4.7 N mm, respectively (p = 0.002). Among women undergoing labor induction, the CEIGE was associated with a cervical dilatation time (4-10 cm) beyond 7 h. For nulliparous women, this area under the ROC curve was 0.94. CONCLUSION: Quantitative strain elastography may constitute a tool for the evaluation of a uterine cervix with normal length in women at risk of preterm birth and in women undergoing labor induction. The performance of this tool deserves evaluation in larger clinical trials.


Assuntos
Técnicas de Imagem por Elasticidade , Nascimento Prematuro , Neoplasias do Colo do Útero , Gravidez , Feminino , Recém-Nascido , Humanos , Criança , Técnicas de Imagem por Elasticidade/métodos , Colo do Útero/diagnóstico por imagem , Curva ROC
11.
Langmuir ; 28(2): 1267-75, 2012 Jan 17.
Artigo em Inglês | MEDLINE | ID: mdl-22175534

RESUMO

Thick conductive layers containing anthraquinone moieties are covalently immobilized on gold using redox grafting of the diazonium salt of anthraquinone (i.e., 9,10-dioxo-9,10-dihydroanthracene-1-diazonium tetrafluoroborate). This grafting procedure is based on using consecutive voltammetric sweeping and through this exploiting fast electron transfer reactions that are mediated by the anthraquinone redox moieties in the film. The fast film growth, which is followed by infrared reflection absorption spectroscopy, atomic force microscopy, X-ray photoelectron spectroscopy, ellipsometry, and coverage calculation, results in a mushroom-like structure. In addition to varying the number of sweeps, layer thickness control can easily be exerted through appropriate choice of the switching potential and sweep rate. It is shown that the grafting of the diazonium salt is essentially a diffusion-controlled process but also that desorption of physisorbed material during the sweeping process is essentially for avoiding blocking of the film due to clogging of the electrolyte channels in the film. In general, sweep rates higher than 0.5 V s(-1) are required if thick, porous, and conducting films should be formed.


Assuntos
Antraquinonas/química , Compostos Azo/química , Microscopia de Força Atômica , Oxirredução , Espectroscopia Fotoeletrônica
12.
Langmuir ; 28(49): 16828-33, 2012 Dec 11.
Artigo em Inglês | MEDLINE | ID: mdl-23163591

RESUMO

This study shows that diazotized ß-cyclodextrin (ß-CD) can be produced, isolated, and immobilized onto glassy carbon and gold surfaces. 4-(1,2,3-Triazol-4-yl)benzenediazonium-ß-CD tetrafluoroborate (pDz-ß-CD) and 3-(1,2,3-triazol-4-yl)benzenediazonium-ß-CD tetrafluoroborate (mDz-ß-CD) were successfully prepared by Cu((I))-catalyzed azide alkyne coupling (CuAAC) of 6-monodeoxy-6-monoazido-ß-cyclodextrin (N(3)-ß-CD) and 4-ethynylaniline and 3-ethynylaniline, respectively, followed by diazotization. The products were isolated and stored successfully for several months at -18 °C. The intermediates and products were verified by Attenuated Total Reflectance Fourier Transform Infrared, Nuclear Magnetic Resonance, and Heteronuclear Single Quantum Coherence. pDz-ß-CD and mDz-ß-CD were immobilized onto glassy carbon and gold surfaces facilitated by electrochemical reduction of the diazonium group. The thus generated aryl radical reacted with the surface. The modified gold surfaces were investigated by Polarization Modulation Infrared Reflection Absorption Spectroscopy and cyclic voltammetry employing the redox probe K(3)Fe(CN)(6) to analyze the extent of blocking of the surfaces. Finally, the availability of the cavity of surface-immobilized ß-CD was shown by complexation of ferrocene followed by cyclic voltametric analysis.

13.
Langmuir ; 27(3): 1070-8, 2011 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-21174427

RESUMO

This work features the controllability of surface-initiated atom transfer radical polymerization (SI-ATRP) of methyl methacrylate, initiated by a multilayered 2-bromoisobutyryl moiety formed via diazonium chemistry. The thickness as a function of polymerization time has been studied by varying different parameters such as the bromine content of the initiator layer, polarity of reaction medium, ligand type (L), and the ratio of activator (Cu(I)) to deactivator (Cu(II)) in order to ascertain the controllability of the SI-ATRP process. The variation of thickness versus surface concentration of bromine shows a gradual transition from mushroom to brush-type conformation of the surface anchored chains in both polar and nonpolar reaction medium. Interestingly, it is revealed that very thick polymer brushes, on the order of 1 µm, can be obtained at high bromine content of the initiator layer in toluene. The initial polymerization rate and the overall final thickness are higher in the case of nonpolar solvent (toluene) compared to polar medium (acetonitrile or N,N-dimethylformamide). The ligand affects the initial rate of polymerization, which correlates with the redox potentials of the pertinent Cu(II)/Cu(I) complexes (L = Me(6)TREN, PMDETA, and BIPY). It is also observed that the ability of polymer brushes to reinitiate depends on the initial thickness and the solvent used for generating it.

14.
Langmuir ; 26(13): 10812-21, 2010 Jul 06.
Artigo em Inglês | MEDLINE | ID: mdl-20411950

RESUMO

Various nitrophenyl-containing organic layers have been electrografted to glassy carbon surfaces using diazonium chemistry to elucidate the extent by which the layer structure influences the solvent (i.e., acetonitrile) accessibility, electroactivity, and chemical reactivity of the films. For most of these films, cyclic voltammetric and impedance spectroscopy measurements show that the electron-transfer process at the electrode is facile and independent of film thickness and structure. This is consistent with the occurrence of self-mediated electron transfers throughout the film with nitrophenyl groups serving as redox stations. Importantly, this behavior is seen only after the first potential sweep, the effect of which is to increase the porosity of the layer by inducing an irreversible desorption of nonchemisorbed material along with a reorganization of the film structure. From a kinetic point of view, the radical anions of surface-attached nitrophenyl groups are reactive toward the residual water present in acetonitrile. Thin layers (thickness of 1 to 2 nm) containing redox-active groups only in the outer part of the layer are protonated two to three times as fast as groups located in a more hydrophobic but still solvent-accessible inner layer. Hence, kinetic measurements can detect small differences in the layer environment. Finally, a deconvolution of the cyclic voltammetric response of an electrode grafted from 4-nitrobenzenediazonium discloses that roughly 25% of the overall signal can be attributed to the presence of 4-azonitrophenyl moieties introduced during the electrografting process.

15.
RSC Adv ; 9(54): 31378-31385, 2019 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-35527981

RESUMO

Recyclable composites are of industrial relevance and benefits the environment, which initiates research towards more sustainable solutions. In this study, a commercial epoxy thermoset, modified by a bio-based additive is used as an infusion resin making recyclable carbon fibre composites. The matrix fractionation process was investigated and optimized with respect to additive & solvent concentration, and temperature. Fully cured carbon reinforced composites were dismantled under the optimum condition and after drying, reinfused, and cured into a new composite, repeated three times on the same carbon fibre material. A decrease in fibre volume fraction and composite performance was found as a number of recyclings were performed. Finally, it was demonstrated that the recycled carbon fibre ply could be reshaped, infused, and cured and thus be applied in new components.

16.
RSC Adv ; 9(25): 14209-14219, 2019 May 07.
Artigo em Inglês | MEDLINE | ID: mdl-35692892

RESUMO

Successfully evaluating plastic lifetime requires understanding of the relationships between polymer dynamics and mechanical performance as a function of thermal ageing. The relatively high T g (T g = 110 °C) of poly(1,4-cyclohexylenedimethylene-co-2,2,4,4-tetramethyl-1,3-cyclobutanediol terephthalate) (PCTT) renders it useful as a substituent for PET in higher temperature applications. This work links thermal ageing and mechanical performance of a commercial PCTT plastic after exposure to 40-80 °C for up to 2950 h. No chemical or conformational changes were found while pronounced physical ageing, measured as enthalpic relaxation, caused yield hardening (28% increase in yield strength) and embrittlement (80% decrease in toughness). Enthalpic relaxation increased with temperature and time to 3.8 J g-1 and correlated to the determined toughness and yield strength. Finally, a 9% increase in Young's modulus was observed independent of temperature and with no correlation to enthalpic relaxation. Enthalpic relaxation followed Vogel-Fulcher-Tammann behaviour, while yield strength and charpy v-notch toughness followed Arrhenius behaviour enabling prediction of the different properties with time and temperature.

17.
ACS Omega ; 3(12): 17511-17519, 2018 Dec 31.
Artigo em Inglês | MEDLINE | ID: mdl-31458355

RESUMO

Stainless steel (SS) surfaces were grafted with poly(glycidyl methacrylate) (PGMA) brushes that were post-modified using allylamine, diallylamine, and propylamine as reagents. Likewise, poly[2-(diethylamino)ethyl methacrylate] brushes were synthesized. All samples were compression molded with uncured ethylene-propylene-diene M-class rubber and dicumyl peroxide and vulcanized for 12 min at 170 °C. The efficiency of the novel bonding solution was evaluated through peel experiments. Two parameters, the fracture toughness () and the cohesive-to-adhesive fracture ratio (A r), were calculated to evaluate the strength and the performance of the coupling, respectively. For the nanometer-thin PGMA films modified with allylamine, in particular, full cohesive fracture was obtained. The obtained values of (15.4 ± 1.1 N mm-1) and A r (1.00 ± 0.01) matched those obtained for a micrometer-thick commercial bonding agent. Cross-linking of polymer brushes by intermolecular reactions by the primary amines proved to have a significant impact on the type of fracture (cohesive/adhesive) and the performance of the adhesives.

18.
ChemSusChem ; 10(14): 2936-2944, 2017 07 21.
Artigo em Inglês | MEDLINE | ID: mdl-28558172

RESUMO

Epoxy-based thermosets are one of the most popular matrix materials in many industries, and significant environmental benefits can be obtained by developing a recyclable variant of this widely utilized material. Incorporation of a bio-based disulfide additive within a commercial epoxy system leads to a cross-linked material that can be fractionated under mild and environmentally benign conditions. The material has been analyzed by FTIR and solid-state NMR. Furthermore, modified epoxy matrices with low additive concentrations are demonstrated to have similar mechanical and thermal properties compared to commercially available benchmarks. Thus, additive formulation and fractionation based on green chemistry principles have been demonstrated, and a recyclable epoxy matrix has been developed.


Assuntos
Compostos de Epóxi/química , Química Verde , Reciclagem , Temperatura , Resistência à Tração
19.
ACS Nano ; 10(2): 2415-23, 2016 Feb 23.
Artigo em Inglês | MEDLINE | ID: mdl-26771258

RESUMO

The electrokinetic energy conversion (EKEC) of hydraulic work directly into electrical energy has been investigated in charged polymeric membranes with different pore charge densities and characteristic diameters of the nanoporous network. The membranes were synthesized from blends of nitrocellulose and sulfonated polystyrene (SPS) and were comprehensively characterized with respect to structure, composition, and transport properties. It is shown that the SPS can be used as a sacrificial pore generation medium to tune the pore size and membrane porosity, which in turn highly affects the transport properties of the membranes. Furthermore, it is shown that very high EKEC efficiencies (>35%) are encountered in a rather narrow window of the properties of the nanoporous membrane network, that is, with pore diameters of ca. 10 nm and pore charge densities of 4.6 × 10(2) to 1.5 × 10(3) mol SO3(-) m(-3) for dilute solutions (0.03 M LiCl). The high absolute value of the efficiency combined with the determination of the optimal membrane morphology makes membrane-based EKEC devices a step closer to practical applications and high-performance membrane design less empirical.

20.
ACS Appl Mater Interfaces ; 7(7): 4160-8, 2015 Feb 25.
Artigo em Inglês | MEDLINE | ID: mdl-25639169

RESUMO

Polymeric ß-cyclodextrin (ßCD) films tunable with respect to thickness and ßCD content were prepared in order to develop a suitable platform, allowing for inclusion of nonpolar guest molecules in the ßCD cavity, while suppressing nonspecific protein adsorption. The ßCD films were synthesized from linear ßCD dextran polymers, and grafted onto silicon oxide surfaces by "click" chemistry. Topographic and morphological characteristics are controllable by reaction conditions and polymer type, with average film heights from 2.5 to 12.5 nm. Reversible introduction of electrostatic charges in the ßCD dextran by complex formation with 1-adamantanecarboxylic acid prior to surface grafting resulted in a thinner and denser film, presumably by decompaction of the polymers. Total internal reflection fluorescence spectroscopy (TIRF) was employed to evaluate the accessibility of ßCD cavities to the fluorescent probe 2-anilinonaphthalene-6-sulfonic acid. Only a minor fraction of the ßCD cavities was accessible in the thicker and less dense films; however, accessibility was largely improved with increased ionic strength using NaCl up to 1 M. Antifouling properties of the ßCD dextran polymer films were assessed by TIRF real-time monitoring, using bovine serum albumin as a model protein, and showed a 5- to 10-fold reduction in nonspecific adsorption as compared to a bare quartz surface with the degree of reduction reflecting film thickness and interfacial polymer density.


Assuntos
Dextranos/química , Polímeros/química , Soroalbumina Bovina/química , beta-Ciclodextrinas/química , Adsorção , Animais , Incrustação Biológica , Bovinos , Concentração Osmolar , Polímeros/síntese química , Soroalbumina Bovina/isolamento & purificação , Dióxido de Silício/química , Espectroscopia de Infravermelho com Transformada de Fourier
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