Browsing by Keyword "Rheology"
Now showing 1 - 7 of 7
Results Per Page
Sort Options
Item Additive Manufactured Scaffolds for Bone Tissue Engineering: Physical Characterization of Thermoplastic Composites with Functional Fillers: Physical Characterization of Thermoplastic Composites with Functional Fillers(2021-08-13) Sinha, Ravi; Sanchez, Alberto; Camara-Torres, Maria; Uriszar-Aldaca, Iñigo Calderon; Calore, Andrea Roberto; Harings, Jules; Gambardella, Ambra; Ciccarelli, Lucia; Vanzanella, Veronica; Sisani, Michele; Scatto, Marco; Wendelbo, Rune; Perez, Sergio; Villanueva, Sara; Matanza, Amaia; Patelli, Alessandro; Grizzuti, Nino; Mota, Carlos; Moroni, Lorenzo; ECOEFICIENCIA DE PRODUCTOS DE CONSTRUCCIÓN; Tecnalia Research & InnovationThermoplastic polymer–filler composites are excellent materials for bone tissue engineering (TE) scaffolds, combining the functionality of fillers with suitable load-bearing ability, biodegradability, and additive manufacturing (AM) compatibility of the polymer. Two key determinants of their utility are their rheological behavior in the molten state, determining AM processability and their mechanical load-bearing properties. We report here the characterization of both these physical properties for four bone TE relevant composite formulations with poly(ethylene oxide terephthalate)/poly(butylene terephthalate (PEOT/PBT) as a base polymer, which is often used to fabricate TE scaffolds. The fillers used were reduced graphene oxide (rGO), hydroxyapatite (HA), gentamicin intercalated in zirconium phosphate (ZrP-GTM) and ciprofloxacin intercalated in MgAl layered double hydroxide (MgAl-CFX). The rheological assessment showed that generally the viscous behavior dominated the elastic behavior (G″ > G′) for the studied composites, at empirically determined extrusion temperatures. Coupled rheological–thermal characterization of ZrP-GTM and HA composites showed that the fillers increased the solidification temperatures of the polymer melts during cooling. Both these findings have implications for the required extrusion temperatures and bonding between layers. Mechanical tests showed that the fillers generally not only made the polymer stiffer but more brittle in proportion to the filler fractions. Furthermore, the elastic moduli of scaffolds did not directly correlate with the corresponding bulk material properties, implying composite-specific AM processing effects on the mechanical properties. Finally, we show computational models to predict multimaterial scaffold elastic moduli using measured single material scaffold and bulk moduli. The reported characterizations are essential for assessing the AM processability and ultimately the suitability of the manufactured scaffolds for the envisioned bone regeneration application.Item Effect of Different Nanoparticles on Mechanical Properties and Curing Behavior of Thermoset Polyurethane Adhesives(2014-10-03) Rodriguez, R.; Perez, B.; Florez, S.; POLIMEROSThree different kinds of nanoparticles (nano-Al2O3, nano-SiO2, and nano-CaCO3) were incorporated into a thermoset polyurethane adhesive. The influence of the type of nanoparticle and concentration on nanoadhesives mechanical, rheological properties, and dispersion degree was analyzed. It was found that as nanoparticle concentration increases tensile strength and Young’s modulus increases. However, there was a maximum concentration from which mechanical properties were reduced. Nanoadhesive mechanical properties were controlled by nanoparticles specific surface area, hardness, and surface treatment. In addition, it was found that the addition of nanoparticles accelerates nanoadhesives curing rate.Item Estudio reológico de mezclas de porcelana reciclada para el moldeo por inyección(2001) Agote, I.; Odriozola, A.; Gutiérrez, M.; Santamaría, A.; Quintanilla, J.; Coupelle, P.; Soares, J.; EXTREMAT; Centros PRE-FUSION TECNALIA - (FORMER); SGThe aim of this work is to investigate the possibility of using waste porcelain for injection moulding. Five formulations of porcelain containing different amounts of recycled porcelain have been studied. Flow properties of these formulations have been analysed and related to injection behaviour.Item Novel bituminous mastics for pavements with improved fire performance(2012-05) Barral, M.; Garmendia, P.; Muñoz, M. E.; Palmillas, Z.; Romera, R.; Santamaria, A.; Villanueva, S.; Ingenieria del Fuego; ECOEFICIENCIA DE PRODUCTOS DE CONSTRUCCIÓNNovel bituminous mastic formulations with performing viscoelastic and mechanical properties and improved resistance to fire, are investigated. The practical performance of the mastics for pavement purposes is analysed. The study is focused on the effectiveness of different sepiolite clays and their mixtures, combined with the fire retardant action of aluminium trihydrate (ATH). Our results indicate that the performance against fire is favoured by the high porosity and density of the sepiolite, and by its lack of affinity with bitumen. Mixing two types of sepiolites we obtain a mastic which presents a synergism between the good cohesion/adhesiveness of one of the formulations and the improved fire performance of other one.Item Novel dynamic viscoelastic measurements of polyurethane copolymer melts and their implication to tack results(2006-10-20) Florez, Sonia; Muñoz, María Eugenia; Santamarín, Anton; POLIMEROSA series of polyurethane multiblock copolymers with different proportions of hard segments (urethane) to soft segments (polyadipate of hexane-1,6-diol), are investigated. Dynamic viscoelastic functions of homogeneous melts in the terminal zone are determined. For the first time, entanglement modulus values of such copolymers are reported, which allows estimation of the packing length. These parameters do not vary with changing the hard-to-soft segment ratio, a result that is explained by u compensating effect of the chain architecture. For samples of similar molecular weight, the relaxation time of the terminal zone increases as the hard-to-soft segment ratio augments. The adhesives obtained from PUR solutions show a correlation between the elastic modulus and the debonding stress-strain curves in tack experiments.Item Rheological study of waste porcelain feedstocks for injection moulding(2001-12) Agote, I.; Odriozola, A.; Gutierrez, M.; Santamaría, A.; Quintanilla, J.; Coupelle, P.; Soares, J.; EXTREMAT; Centros PRE-FUSION TECNALIA - (FORMER); SGFive types of hard porcelain powders for injection moulding have been studied, using the same commercial binder in all cases. These powders contained different amounts of recycled porcelain, since one of the principal aims of this work is to reuse waste porcelain in the injection moulding process. The evaluation of the flowability of different feedstocks was carried out using rheological parameters, like critical powder volume concentration (CPVC), melt viscosity, activation energy, yield stress, powder law index and rheological index. The correlation of these parameters with injection behaviour was established, in order to confirm the possibility of using this moulding process with recycled porcelain powders.Item Rheology of Solar-Salt based nanofluids for concentrated solar power. Influence of the salt purity, nanoparticle concentration, temperature and rheometer geometry(2018-03) Muñoz-Sánchez, Belén; Nieto-Maestre, Javier; Veca, Elisabetta; Liberatore, Raffaele; Sau, Salvatore; Navarro, Helena; Ding, Yulong; Navarrete, Nuria; Juliá, J. Enrique; Fernández, Ángel G.; García-Romero, Ana; Tecnalia Research & Innovation; VALORIZACIÓN DE RESIDUOSSolar Salt-based nanofluids have attracted significant scientific interest in recent years due to their improved thermal properties, making them strong candidates as thermal energy storage materials and/or heat transfer fluids in CSP plants. There have been reports on increased specific heat due to the addition of nanoparticles, however, there is a lack of comprehensive information on other essential properties affecting the heat transfer, such as the viscosity. This article concerns the rheological behaviour of nanofluids made of Solar Salt (mass percentage at 60% NaNO3 – 40% KNO3) as the base fluid and silica or alumina nanoparticles as additives. The evolution of these nanofluids viscosity as a function of the shear rate (1–1000 s−1) at a temperature range of 250–400 °C was measured and analysed. The impact of the salt purity (refined or industrial grade), the nanoparticle concentration (0.5–1.5 wt%) and the rheometer measuring configuration (coaxial cylinder or parallel plate) are examined. The results showed in general a Newtonian behaviour of the nanofluids with independency of the rheometer configuration. The relationship between the viscosity and the temperature follows an Arrhenius model. The influence of the nanoparticle concentration on the viscosity of the refined grade Solar Salt is analysed according to the Maron-Pierce and Kriegher-Dougherty models for the nanofluids containing alumina and silica nanoparticles respectively, due to their different shape.