Página 1 dos resultados de 209 itens digitais encontrados em 0.032 segundos

Reticulação da poli (N-vinil-2-pirrolidona) e copolímeros por processos químicos; Poly (N-vinyl-2- pyrrolidone) and copolymers crosslinking by chemical process

Barros, Janaina Aline Galvão
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 05/10/2007 PT
Relevância na Pesquisa
47.565947%
Hidrogéis são materiais poliméricos com habilidade em intumescer em água e fluidos biológicos sem, contudo, se dissolver. Devido às suas propriedades de maciez e biocompatibilidade, estes materiais têm tido um crescimento enorme na área de engenharia de tecido, encapsulamento de células e liberação de drogas. Este trabalho visa a produção de hidrogéis de poli(N-vinil-2-pirrolidona) e seus copolímeros a partir de reticulações químicas. Como metodologia alternativa de produção de hidrogéis de poli(N-vinil-2-pirrolidona), foi estudada a reticulação do PVP por reação de Fenton, sendo que as concentrações dos reagentes foram avaliadas a fim de produzir um hidrogel com características semelhantes aos hidrogéis de PVP por radiação ionizante. O grande diferencial desta metodologia foi a rápida cinética de gelificação apresentada, creditanto um potencial de aplicação inédito. A partir de reticulações químicas mais brandas, foi estudada a produção de hidrogéis de copolímeros de N-vinil-2-pirrolidona e aldeídos com quitosana, e íons divalentes. Além de estudadas as propriedades relativas ao hidrogel tais como: conteúdo de gel, grau de intumescimento, cinética de reação...

Estudo da caracterização de espumas de polietileno reticulado pelo processo de irradiação com feixe de elétrons; Study of the caracterization of crosslinking polyethylene foam by irradiation process with electron beam

Dias, Djalma Batista
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 28/02/2007 PT
Relevância na Pesquisa
27.989756%
As espumas de polietileno são amplamente utilizadas. Suas aplicações vão de aparelhos domésticos a artefatos médicos, incluindo aplicações nas indústrias de construção civil e automobilística. As propriedades das espumas dependem da densidade e da sua estrutura celular, em outras palavras, da quantidade de células abertas e fechadas, da distribuição e do tamanho das células. Os métodos de produção de espumas de polietileno reticulado são classificados em dois tipos, de acordo com o método de reticulação. Um dos métodos é a reticulação química, que utiliza peróxidos como agente reticulante, O outro método é a reticulação por irradiação, utilizando feixe de elétrons. As espumas obtidas a partir do polietileno reticulado pelo processo de irradiação apresentam superfície lisa e homogênea, e são formadas basicamente por células fechadas. O objetivo deste trabalho foi utilizar a radiação ionizante para a formação de ligações cruzadas entre as moléculas de polietileno de baixa densidade (LDPE), que permitiu a obtenção das espumas. As suas propriedades mecânicas, térmicas e morfológicas foram avaliadas. As amostras de polietileno com densidade de 0,946 g/cm3, contendo 5% de azodicarbonamida (ADCA)...

Caracterização da sílica amorfa extraída da casca de arroz obtida por pré-hidrólise ácida e calcinação, e sua aplicação em borracha de estireno-butadieno (SBR); Characterization of amorphous rice husk silica obtained by acidic prehydrolysis and calcination, and its application in styrene-butadiene rubber (SBR)

Budemberg, Eduardo Roque
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 14/06/2013 PT
Relevância na Pesquisa
36.84119%
O crescimento dos países em desenvolvimento aumentará em várias vezes o consumo de energia, materiais e alimentos. Para suprir essa demanda é necessário o aproveitamento racional dos resíduos gerados por processos industriais, agrícolas e lixo urbano, transformando-os em energia economicamente competitiva com as outras formas de energia, e em materiais com propriedades otimizadas. O objetivo do presente trabalho foi comparar o comportamento da sílica da casca de arroz obtida por pré-hidrólise ácida seguida de calcinação controlada (Sil-PH) com sílicas de casca de arroz comerciais obtidas simplesmente pela queima da casca (Sil-B e Sil-C) e com a sílica comercial obtida da areia quartzítica (Sil-Z), como carga de reforço em borracha de estireno-butadieno (SBR), que é a mais usada na indústria de fabricação de pneus. Estudos foram conduzidos em SBR 1502, preparados conforme norma ASTM 3191-2010. Foram adicionadas à borracha as sílicas em concentrações de 0, 10, 20 e 40 ppcb. Foram conduzidos testes físicos, químicos, mecânicos, reométricos, dinâmico-mecânicos e análise térmica, bem como ensaios de inchamento dos corpos de prova em toluol e análise microestrutural das sílicas e dos compostos por microscopia eletrônica de varredura...

Platelets lysate-based membranes for periodontal ligament regeneration

Babo, P. S.; Santo, Vítor E.; Duarte, Ana Rita C.; Gomes, Manuela E.; Reis, R. L.
Fonte: Wiley & Sons, Inc. Publicador: Wiley & Sons, Inc.
Tipo: Conferência ou Objeto de Conferência
Publicado em /10/2013 ENG
Relevância na Pesquisa
27.804526%
Publicado em "Journal of Tissue Engineering and Regenerative Medicine", vol. 7, supp. 1 (2013); The periodontal ligament (PDL) is a group of specialized connective tissue fibers that attach a tooth to the alveolar bone where it is deployed. These fibers help the tooth withstand the substantial compressive forces which occur during chewing and remain embedded in the bone. Periodontitis is a prevalent infection disease that causes the destruction of the tooth supportive tissues including the PDL. Given its low ability of regeneration in adult patients, concerted efforts have been made to accelerate periodontal tissue regeneration. Nevertheless, a strategy for predictable reconstruction of normal structure and functionality of periodontal damaged tissue is yet to be achieved. In this work, we present a novel membrane based on platelets lysate (PL) aiming for PDL regeneration. PL is a source of multiple growth factors (GFs) such as PDGF-BB, VEGF, and TGF-β1, which are prompt to induce wound healing and the recruitment of cells for tissue regeneration. In this work, we propose the development of PL-based membranes prepared by crosslinking PL proteins with genipin for periodontal tissue regeneration. Increasing concentrations of genipin (0.10...

Low density lipoprotein receptor-related protein/alpha 2-macroglobulin receptor is an hepatic receptor for tissue-type plasminogen activator.

Bu, G; Williams, S; Strickland, D K; Schwartz, A L
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em 15/08/1992 EN
Relevância na Pesquisa
27.47505%
Tissue-type plasminogen activator (t-PA), a serine protease that catalyzes the initial and rate-limiting step in the fibrinolytic cascade, is cleared rapidly in vivo by the liver. Using chemical crosslinking, we have recently identified a plasminogen-activator inhibitor type 1 (PAI-1)-independent t-PA clearance receptor on rat hepatoma MH1C1 cells with a relative molecular mass of approximately 500 kDa. Another recently identified membrane receptor, low density lipoprotein receptor-related protein/alpha 2-macroglobulin receptor (LRP/alpha 2MR), was also detected on MH1C1 hepatoma cells by using immunoprecipitation with anti-LRP/alpha 2MR antibody. When analyzed by SDS/PAGE, we found the t-PA receptor identified on MH1C1 cells comigrated with the large subunit of LRP/alpha 2MR. The t-PA receptor was immunoprecipitated by an anti-LRP/alpha 2MR antibody after chemical crosslinking of specifically bound 125I-labeled t-PA to its receptor. Through chemical crosslinking studies, we found that t-PA and methylamine-activated alpha 2-macroglobulin could bind to LRP/alpha 2MR simultaneously without competing with one another for binding, suggesting that the two ligands bound to two independent sites on the LRP/alpha 2MR molecule. Furthermore...

Covalent crosslinking of human chorionic gonadotropin to its receptor in rat testes.

Rebois, R V; Omedeo-Sale, F; Brady, R O; Fishman, P H
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /04/1981 EN
Relevância na Pesquisa
27.500347%
The bifunctional crosslinking reagents disuccinimidyl suberate and dithiobis(succinimidyl propionate) were used to attach 125I-labeled human chorionic gonadotropin (125I-hCG) covalently to rat testicular membranes. The extent of crosslinking was dependent on time and concentration; routinely, 30% of the specifically bound hormone was covalently linked to the membranes in the presence of 0.5 mM crosslinking reagent when incubated at 25 degrees C for 15 min. Excess unlabeled hCG blocked the crosslinking of 125I-hCG to the membranes. When solubilized with Triton X-100 and analyzed by sucrose density gradient centrifugation, both the native and the crosslinked hormone-receptor complex sedimented with an apparent Mr of 220,000. Thus, the receptor itself would have Mr 180,000. When the crosslinked complex was analyzed by sodium dodecyl sulfate/polyacrylamide gel electrophoresis, the predominant species had a Mr of 123,000 and appeared to represent the labeled alpha subunit of hCG covalently linked to a membrane component. The Mr of this receptor component would be 100,000, a value approximately half that of the Triton X-100-solubilized receptor. Thus, the membrane receptor for hCG may consist of a dimer of two binding subunits or a binding subunit associated with one or more additional subunits that might play a coupling or regulatory function.

Histone H1 and HMG 14/17 are deposited nonrandomly in the nucleus.

Leffak, M; Trempe, J P
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em 11/07/1985 EN
Relevância na Pesquisa
27.609133%
We have studied the assembly of histone H1 and the high mobility group nonhistones 14/17 by isopycnic analysis after crosslinking density labeled MSB cell nuclei or chromatin. Carbodiimide crosslinking produces dense poly-H1 and hybrid density H1-H2A histone dimers, indicating that new H1 is deposited nonrandomly, albeit nonconservatively relative to new core histones. Core histone-HMG crosslinking with succinimidyl propionate yields dense HMG 14 in uniformly dense particles and new HMG 17 crosslinked to both dense and light protein, implying that HMG 14 and 17 each deposit nonrandomly; but differently with respect to new core octamers. Propionimidate crosslinking yields dense H1-HMG 17 dimers, suggesting that the interactions of new 14/17 with H1 (new HMG 14-old H1, new HMG 17-new H1) are reciprocal to their interactions with the core histones.

The Impact of HA Oligomer Content on Physical, Mechanical, and Biologic Properties of Divinyl Sulfone-Crosslinked HA Hydrogels

Ibrahim, Samir; Kang, Qian K; Ramamurthi, Anand
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /08/2010 EN
Relevância na Pesquisa
27.500347%
In recent studies, we showed that exogenous hyaluronic acid oligomers (HA-o) stimulate functional endothelialization, though native long-chain HA is more bioinert and possibly more biocompatible. Thus, in this study, hydrogels containing high molecular weight (HMW) HA (1×106 Da) and HA oligomer mixtures (HA-o: 0.75–10 kDa) were created by crosslinking with divinyl sulfone (DVS). The incorporation of HA oligomers was found to compromise the physical and mechanical properties of the gels (rheology, apparent crosslinking density, swelling ratio, degradation) and to very mildly enhance inflammatory cell recruitment in vivo; increasing the DVS crosslinker content within the gels in general, had the opposite effect, though the relatively high concentration of DVS within these gels (necessary to create a solid gel) also stimulated a mild sub-cutaneous inflammatory response in vivo and VCAM-1 expression by ECs cultured atop; ICAM-expression levels remained very low irrespective extent of DVS crosslinking or HA-o content. The greatest EC attachment and proliferation (MTT assay) was observed on gels that contained the highest amount of HA-o. The study shows that the beneficial EC response to HA oligomers and biocompatibility of HA is mostly unaltered by their chemical derivatization and crosslinking into a hydrogel. However...

The effects of PEG hydrogel crosslinking density on protein diffusion and encapsulated islet survival and function

Weber, Laney M.; Lopez, Christina G.; Anseth, Kristi S.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em 01/09/2009 EN
Relevância na Pesquisa
47.77804%
The rational design of immunoprotective hydrogel barriers for transplanting insulin-producing cells requires an understanding of protein diffusion within the hydrogel network and how alterations to the network structure affect protein diffusion. Hydrogels of varying crosslinking density were formed via the chain polymerization of dimethacrylated PEG macromers of varying molecular weight, and the diffusion of six model proteins with molecular weights ranging from 5,700 to 67,000 g/mol was observed in these hydrogel networks. Protein release profiles were used to estimate diffusion coefficients for each protein/gel system that exhibited Fickian diffusion. Diffusion coefficients were on the order of 10−6 to 10−7 cm2/s, such that protein diffusion time scales (td = L2/D) from 0.5 mm thick gels vary from 5 minutes to 24 hours. Adult murine islets were encapsulated in PEG hydrogels of varying crosslinking density, and islet survival and insulin release was maintained after two weeks of culture in each gel condition. While the total insulin released during a one hour glucose stimulation period was the same from islets in each sample, increasing hydrogel crosslinking density contributed to delays in insulin release from hydrogel samples within the one hour stimulation period.

Photo-Crosslinked Poly(ε-caprolactone fumarate) Networks: Roles of Crystallinity and Crosslinking Density in Determining Mechanical Properties

Wang, Shanfeng; Yaszemski, Michael J.; Gruetzmacher, James A.; Lu, Lichun
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em 08/12/2008 EN
Relevância na Pesquisa
37.500347%
We present a material design strategy of combining crystallinity and crosslinking to control the mechanical properties of polymeric biomaterials. Three polycaprolactone fumarates (PCLF530, PCLF1250, and PCLF2000) synthesized from the precursor polycaprolactone (PCL) diols with nominal molecular weights of 530, 1250, and 2000 g.mol-1, respectively, were employed to fabricate polymer networks via photo-crosslinking process. Five different amounts of photo-crosslinking initiator were applied during fabrication in order to understand the role of photoinitiator in modulating the crosslinking characteristics and physical properties of PCLF networks. Thermal properties such as glass transition temperature (Tg), melting temperature (Tm), and degradation temperature (Td) of photo-crosslinked PCLFs were examined and correlated with their rheological and mechanical properties.

Hydrogel crosslinking density regulates temporal contractility of human embryonic stem cell-derived cardiomyocytes in 3D cultures

Chung, Cindy; Anderson, Erica; Pera, Renee Reijo; Pruitt, Beth L.; Heilshorn, Sarah C.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
48.027666%
Systematically tunable in vitro platforms are invaluable in gaining insight to stem cell-microenvironment interactions in three-dimensional cultures. Utilizing recombinant protein technology, we independently tune hydrogel properties to systematically isolate the effects of matrix crosslinking density on cardiomyocyte differentiation, maturation, and function. We show that contracting human embryonic stem cell-derived cardiomyocytes (hESC-CMs) remain viable within four engineered elastin-like hydrogels of varying crosslinking densities with elastic moduli ranging from 0.45 to 2.4 kPa. Cardiomyocyte phenotype and function was maintained within hESC embryoid bodies for up to 2 weeks. Interestingly, increased crosslinking density was shown to transiently suspend spontaneous contractility. While encapsulated cells began spontaneous contractions at day 1 in hydrogels of the lowest crosslinking density, onset of contraction was increasingly delayed at higher crosslinking densities up to 6 days. However, once spontaneous contraction was restored, the rate of contraction was similar within all materials (71 ± 8 beats/min). Additionally, all groups successfully responded to electrical pacing at both 1 and 2 Hz. This study demonstrates that encapsulated hESC-CMs respond to 3D matrix crosslinking density within elastin-like hydrogels and stresses the importance of investigating temporal cellular responses in 3D cultures.

Genipin-Crosslinked Cartilage-Derived Matrix as a Scaffold for Human Adipose-Derived Stem Cell Chondrogenesis

Cheng, Nai-Chen; Estes, Bradley T.; Young, Tai-Horng; Guilak, Farshid
Fonte: Mary Ann Liebert, Inc. Publicador: Mary Ann Liebert, Inc.
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
27.500347%
Autologous cell-based tissue engineering using three-dimensional scaffolds holds much promise for the repair of cartilage defects. Previously, we reported on the development of a porous scaffold derived solely from native articular cartilage, which can induce human adipose-derived stem cells (ASCs) to differentiate into a chondrogenic phenotype without exogenous growth factors. However, this ASC-seeded cartilage-derived matrix (CDM) contracts over time in culture, which may limit certain clinical applications. The present study aimed to investigate the ability of chemical crosslinking using a natural biologic crosslinker, genipin, to prevent scaffold contraction while preserving the chondrogenic potential of CDM. CDM scaffolds were crosslinked in various genipin concentrations, seeded with ASCs, and then cultured for 4 weeks to evaluate the influence of chemical crosslinking on scaffold contraction and ASC chondrogenesis. At the highest crosslinking degree of 89%, most cells failed to attach to the scaffolds and resulted in poor formation of a new extracellular matrix. Scaffolds with a low crosslinking density of 4% experienced cell-mediated contraction similar to our original report on noncrosslinked CDM. Using a 0.05% genipin solution...

The influence of hyaluronic acid hydrogel crosslinking density and macromolecular diffusivity on human MSC chondrogenesis and hypertrophy

Bian, Liming; Hou, Chieh; Tous, Elena; Rai, Reena; Mauck, Robert L.; Burdick, Jason A.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
48.152974%
Hyaluronic acid (HA) hydrogels formed via photocrosslinking provide stable 3D hydrogel environments that support the chondrogenesis of mesenchymal stem cells (MSCs). Crosslinking density has a significant impact on the physical properties of hydrogels, including their mechanical stiffness and macromolecular diffusivity. Variations in the HA hydrogel crosslinking density can be obtained by either changes in the HA macromer concentration (1, 3, or 5% w/v at 15 min exposure) or the extent of reaction through light exposure time (5% w/v at 5, 10, or 15 min). In this work, increased crosslinking by either method resulted in an overall decrease in cartilage matrix content and more restricted matrix distribution. Increased crosslinking also promoted hypertrophic differentiation of the chondrogenically induced MSCs, resulting in more matrix calcification in vitro. For example, type X collagen expression in the high crosslinking density 5% 15 min group was ~156 and 285% higher when compared to the low crosslinking density 1% 15 min and 5% 5 min groups on day 42, respectively. Supplementation with inhibitors of the small GTPase pathway involved in cytoskeletal tension or myosin II had no effect on hypertrophic differentiation and matrix calcification...

Three-dimensional hMSC Motility within Peptide-Functionalized PEG-Based Hydrogel of Varying Adhesivity and Crosslinking Density

Kyburz, Kyle A; Anseth, Kristi S
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
47.643955%
Human mesenchymal stem cell (hMSC) migration and recruitment play a critical role during bone fracture healing. Within the complex 3D in vivo microenvironment, hMSC migration is regulated through a myriad of extracellular cues. Here, we use a thiol-ene photopolymerized hydrogel to recapitulate structural and bioactive inputs in a tunable manner to understand their role in regulating 3D hMSC migration. Specifically, peptide-functionalized poly(ethylene glycol) hydrogels were used to encapsulate hMSC while varying the crosslinking density, 0.18 ± 0.02 - 1.60 ± 0.04 mM, and the adhesive ligand density, 0.001 to 1.0 mM. Using live cell videomicroscopy migratory cell paths were tracked and fit to a persistent random walk model. It was shown that hMSC migrating through the lowest crosslinking density and highest adhesivity had more sustained polarization, higher migrating speeds (17.6 ± 0.9 μm/hr), and higher cell spreading (Elliptical Form Factor = 3.9 ± 0.2). However, manipulation of these material properties did not significantly affect migration persistence. Further, there was a monotonic increase in cell speed and spreading with increasing adhesivity showing a lack of the biphasic trend seen in two dimensional cell migration. Immunohistochemistry showed well-formed actin fibers and β1 integrin staining at the ends of stress fibers. This thiol-ene platform provides a highly tunable substrate to characterize 3D hMSC migration with application as an implantable cell carrier platform or for the recruitment of endogenous hMSC in vivo.

Development of a biodegradable interbody fusion device

Timmer, Mark Davis
Fonte: Universidade Rice Publicador: Universidade Rice
ENG
Relevância na Pesquisa
27.654368%
Novel polymer networks based on poly(propylene fumarate) (PPF) and the crosslinking agent poly(propylene fumarate)-diacrylate (PPF-DA) were investigated as a material for a biodegradable interbody fusion cage. The aim of this work was to establish the effect of the macromolecular network structure on the physical properties in order to tailor the material to demonstrate high strength, controllable degradation, and suitable biocompatibility for this implant. The PPF/PPF-DA network structure was characterized with a newly developed technique in which the networks were degraded into simpler linear constituents that provided insight to the macromolecular structure. The double bond conversion and crosslinking density of the polymer networks was controlled by the concentrations of PPF and PPF-DA in the network, as dictated by the double bond ratio of fumarate groups in the PPF backbone to acrylate groups in the PPF-DA crosslinker. Lower double bond ratios yielded higher conversions and a more densely crosslinked network. The network structure was further influenced by the free radical initiator system. The mechanical properties of the PPF/PPF-DA networks increased with decreasing double bond ratios as a result of higher crosslinking densities. Photo-crosslinking produced a stronger material and also facilitated processing of PPF/PPF-DA networks because there is greater control over the crosslinking reaction. Examination of the in vitro degradation behavior of PPF/PPF-DA networks in simulated body fluids showed that the degradation rate was faster for networks with lower crosslinking densities. The biocompatibility of the material was also controlled by the macromolecular structure as PPF/PPF-DA networks with higher double bond conversions and crosslinking densities exhibited no adverse cytotoxicity and enabled fibroblast attachment. A prototype PPF/PPF-DA interbody fusion cage was fabricated by photo-crosslinking the polymers in transparent silicone molds. The PPF/PPF-DA implant demonstrated similar mechanical properties as a clinical approved allograft spacer and suggested that the device can provide sufficient support for interbody fusion. This work demonstrated that PPF/PPF-DA networks are a suitable material for a biodegradable interbody fusion device as well as other load bearing orthopaedic implants.

Role of strain induced crystallization and oxidative crosslinking in fracture properties of rubbers

LE GAC, Pierre Yves; BROUDIN, Morgane; ROUX, Gérard; VERDU, Jacques; DAVIES, Peter; FAYOLLE, Bruno
Fonte: Elsevier Publicador: Elsevier
EN
Relevância na Pesquisa
27.815168%
Tensile properties and crack propagation properties, especially critical strain energy release rate in mode I, GIC, have been used to investigate fracture properties of elastomers and their relationships with microstructure. These investigations were mainly based on a series of comparisons: first, the behaviour of polychloroprene rubber (CR), undergoing stress hardening due to strain induced crystallization (SIC) and oxidative crosslinking (OCL) was compared with that of chlorinated polyethylene (CPE), which undergoes SIC but not OCL, and with a polyurethane based on hydroxyl terminated polybutadiene (PU) which undergoes OCL but not SIC. Comparisons were also made on CR between fracture behaviour at ambient temperature, where SIC occurs and at 100°C where there is no SIC. Finally, oxidative crosslinking was used to vary in a continuous way the crosslink density in CR and PU, in order to evaluate the role of crosslinking in fracture behaviour. The results reveal the strong contribution of SIC to fracture strength. Crosslinking, even at low conversion, inhibits SIC which explains the sharp decrease of CR toughness in the early period of exposure to oxidation. When SIC has disappeared, it is possible to appreciate the effect of crosslinking on fracture behaviour. This effect...

Effects of the Amount of Fillers and of the Crosslink Density on the Mechanical Behavior of Carbon-Black Filled Styrene Butadiene Rubbers

MERCKEL, Yannick; DIANI, Julie; BRIEU, Mathias; CAILLARD, Julien
Fonte: Wiley Publicador: Wiley
EN
Relevância na Pesquisa
36.945752%
Several carbon-black filled styrene-butadiene rubbers are subjected to monotonic uniaxial tension tests in order to investi-gate the effects of the amount of fillers and of the crosslink density on their mechanical properties. The Young modulus, the volume changes associated with material damage and the stretch to failure are extracted and discussed. Results compare well to the literature results when exist and quantitative analysis are proposed when possible. Results show that filled rubbers are not incompressible when submitted to uniaxial tension tests and their volume changes are strongly dependent of the amount of fillers but are unaffected by the crosslink density. The latter shows strong impact on the filled rubbers stretch to failure but more interestingly this impact is com-parable to what is encountered in unfilled rubbers. The stretch to failure is improved by the addition of fillers with an optimum for material filled around 30 phr.

Influencia da densidade de reticulação, na liberação da rodamina B, em agua, a partir de hidrogeis de PVAI : aplicação em liberação controlada de drogas

Rosana Costa Leite
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 07/03/1996 PT
Relevância na Pesquisa
27.804526%
Neste trabalho, hidrogéis de Poli(Álcool Vinílico) ? PVAI foram preparado por reticulação química, usando Ácido Adípico como agente reticulante. Hidrogéis de diferentes graus de reticulação foram obtidos variando-se a concentração do reticulante de 0,5% a 4% (w/w). Os filmes de PVAI reticulados foram caracterizados através das técnicas de Infra-vermelho e Análise Dinâmico-Mecânica. O intumescimento foi estimado a partir da variação ocorrida no peso quando as amostras de hidrogéis foram imersas em água destilada à temperatura ambiente. Através dessas medidas foi determinada a densidade de reticulação das amostras aplicando-se a equação clássica de Flory-Rehner. O efeito que a reticulação do material exerce sobre a difusão da Rodamina B, a partir do hidrogel, para o meio aquoso, foi estudado utilizando as amostras obtidas com diferentes concentrações de reticulante. Através da '2 POT. A' lei de Fick, utilizada para calcular o coeficiente de difusão do soluto, pode-se observar que, com o aumento da densidade de reticulação, a resistência das cadeias da rede, em se expandir, também aumentou. Como conseqüência, o grau de intumescimento do hidrogel diminuiu acarretando menores coeficientes de difusão. Assim sendo...

Raw Data for Article "Control of crosslinking for tailoring collagen-based scaffolds stability and mechanics"

Davidenko, N.; Schuster, C. F.; Bax, D. V.; Raynal, N.; Farndale, R. W.; Best, S. M.; Cameron, R. E.
Fonte: Universidade de Cambridge Publicador: Universidade de Cambridge
Tipo: Relatório Formato: Zipp Excel files
Relevância na Pesquisa
37.05754%
The zipped folder called ?Raw Data for Article? contains 8 files as described below: File cold ?Rheology? contains raw data of viscosity study (Fig 1). File ?Density? contains raw data of dimensional properties showed in Table 1. File ?Amine? contains results of amine group content testing and calculation of the degree of cross-linking (Fig 4 and Table 2). Files ?Sigma? and ?Devro? contain raw data of degradation studies on collagen (sigma)- and collagen (devro)-based scaffolds, respectively (Fig 5, 6 and 7). Files ?Mechanics? and ?Art EDC OA mechanics repeated test? contain results of the mechanical testing: the first file shows the raw data for compressive modulus of the scaffolds of different compositions (Fig 8a) and the second shows the data for stress?strain curves (Fig 8b). File ?Cells? contains results of static adhesion of platelets and HT1080 cells on collagen(sigma), collagen-gelatin and gelatin films (Fig 9).; This record will be updated with publication details.; This work was supported by the ERC [grant number 320598 3D-E]; the EPSRC [IKC Proof of Concept Award 028]; the BHF [grant numbers NH/11/1/28922, RG/09/003/27122]; and The Peoples Programme of the EU 7th Framework Programme [RAE no: PIIF-GA-2013-624904].

The I-V characteristics of organic hole-only devices based on crosslinked hole-transport layer

Rudati,P.S.; Mueller,D.C.; Meerholz,K.
Fonte: UNAM, Centro de Ciencias Aplicadas y Desarrollo Tecnológico Publicador: UNAM, Centro de Ciencias Aplicadas y Desarrollo Tecnológico
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2015 EN
Relevância na Pesquisa
27.500347%
Commonly, organic electronics devices are build up from the organic semiconductor thin films which are prepared either by thermal vacuum evaporation or by solution-processing techniques such as spin casting, inkjet printing, or roll-to-roll printing. The solution-processing has several advantages although it has a crucial problem for multilayer device preparation where the first layer will be dissolved by the solvent of the second layer. The using of insoluble layer is a solution of this problem. This paper reports the electrical (I-V) characteristics of Hole-Only Devices (HOD) which are prepared via solution processing by using insoluble layer. The insoluble layer based on triphenylamine dimmer was sandwiched in the two electrodes as anode and cathode. This insoluble layer was prepared via oxetane ring-opening polymerisation either oxidative crosslinking, photo crosslinking, or trityl crosslinking. The measurement was carried out to get current density versus electric-field strength characteristic as a function of oxidation potential, polymerisation mechanism, the amount of oxidant, and curing temperature. The measurement confirmed that the crosslinked hole-transport layers are successfully applied in HOD, the oxidative crosslinking mechanism showed the doping effect...