Papers by Antxon Santamaria
Polymers, Jul 14, 2021
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
Nanomaterials, 2013
Non-modified Multiwalled Carbon Nanotubes (MWCNT) and polypropylene (PP) in absence of compatibil... more Non-modified Multiwalled Carbon Nanotubes (MWCNT) and polypropylene (PP) in absence of compatibilizer have been chosen to elaborate MWCNT/PP nanocomposites using a simple melt-mixing dispersing method. Calorimetry results indicate little effect of MWCNTs on crystallinity of PP, revealing not much interaction between nanotubes and PP chains, which is compatible with the employed manufacturing procedure. In any case, a hindering of polymer chains motion by MWCNTs is observed in the molten state, using oscillatory flow experiments, and a rheological percolation threshold is determined. The percolation limit is not noticed by Pressure-Volume-Temperature (PVT) measurements in the melt, because this technique rather detects local motions. Keeping the nanocomposites in the molten state provokes an electrical conductivity increase of several orders of magnitude, but on ulterior crystallization, the conductivity decreases, probably due to a reduction of the ionic conductivity. For a concentration of 2% MWCNTs, in the limit of percolation, the conductivity decreases considerably more, because percolation network constituted in the molten state is unstable and is destroyed during crystallization.
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Journal of Rheology
Linear and nonlinear viscoelastic approaches are used to study multiphase biobased blends of poly... more Linear and nonlinear viscoelastic approaches are used to study multiphase biobased blends of poly(lactic acid), poly(amide 11), poly(ether-b-amide) (PEBA), and poly(ethylene oxide) (PEO) in a wide range of compositions. The novelty of this work resides in (a) the study of hybrid quaternary blends with droplet-matrix as well as cocontinuous morphology, (b) the effect of the PEO and PEBA blend components on the rheological properties, and (c) the investigation of the nonlinear viscoelastic regime for complex hybrid blends. Correlations are established between blend morphology and rheological behavior. Among the different linear rheological approaches, i.e., elastic modulus, complex viscosity, yield stress, Cole–Cole plots, Han plots, and Mavridish–Shroff or Booij–Palmen plots, the latter is the most sensitive allowing extraction of a relaxation time from the plot. The results correlate reasonably well with the different morphologies of the blends. Both, linear and nonlinear methods lead to compatible results, distinguishing among blends with droplet-matrix, partially continuous dispersed phase and fully cocontinuous morphologies. Moreover, for the first time, the analysis of the nonlinear parameter, Q0, allows a qualitative comparison of the interfacial areas of blends with a dispersed phase-matrix morphology at different continuity levels and those with cocontinuous morphology.
Polymers, 2022
The sole effect of the microstructure of biodegradable isodimorphic poly(butylene succinate)-ran-... more The sole effect of the microstructure of biodegradable isodimorphic poly(butylene succinate)-ran-poly(ε-caprolactone) random copolyesters on their rheological properties is investigated. To avoid the effect of molecular weight and temperature, two rheological procedures are considered: the activation energy of flow, Ea, and the phase angle versus complex modulus plots. An unexpected variation of both parameters with copolyester composition is observed, with respective maximum and minimum values for the 50/50 composition. This might be due to the peculiar chain configurations of the copolymers that vary as a function of comonomer distribution within the chains. The same chain configuration variations are responsible for the isodimorphic character of the copolymers in the crystalline state. Tack tests, performed to study the viability of the copolyesters as environmentally friendly hot melt adhesives (HMA), reveal a correlation with rheological results. Tackiness parameters, particula...
Springer Proceedings in Materials, 2019
The aim of this work is to present the two most important contributions of Rheology to the field ... more The aim of this work is to present the two most important contributions of Rheology to the field of polymer science and technology: (a) Non Newtonian flow and relevance of shear thinning in polymer processing (b) Significance of chain entanglements in polymers viscoelasticity.
Polymers, 2021
We investigated polyurethane (PU)–carbon nanotube (CNT) nanocomposites (PU/CNT) in a range of con... more We investigated polyurethane (PU)–carbon nanotube (CNT) nanocomposites (PU/CNT) in a range of concentrations from 1 to 8 wt% CNT as hot melt adhesives. We studied the thermal properties of the nanocomposites, which is relevant from an applied point of view. The phase angle plots versus complex modulus results revealed the existence of a maximum above a given CNT concentration. The intensity of the peak and associated relaxation time was analyzed with percolation theory, leading to a new method to determine the rheological percolation threshold. A lower threshold value was obtained from the electrical conductivity data, which was justified recalling that the hopping/tunnelling effect takes place in the nanocomposite, as stated by previous studies in the literature. Joule effect studies indicated that the heating effect was very significant, reaching temperature increases, ΔT, of 60 °C for low voltages. For the first time, the percolation equation was applied to the ΔT to obtain the c...
EKAIA Euskal Herriko Unibertsitateko Zientzia eta Teknologia Aldizkaria, Mar 12, 2018
Laburpena: Polipropileno/Poliamida (PP/PA) nahasteak prestatu dira eta kopolimerokonpatibilizatza... more Laburpena: Polipropileno/Poliamida (PP/PA) nahasteak prestatu dira eta kopolimerokonpatibilizatzailea eta nanosilika gehitzeak nahaste horietan duen eragina aztertu da. Azterketa mikroskopikoak erakusten duenez, nahasteek emultsio antzeko morfologia dute, polipropilenoak fase jarraitua osatzen duelarik. Konpatibilizatzailea zein nanosilika gehitzeak PA tanten tamaina nabarmen murrizten duela antzematen da. Nahaste bitarrak fluxu jarraitu baten eraginpean daudenean, PA tanten koaleszentzia gerta daiteke eta, ondorioz, tanten tamaina handitu egiten da. Kopolimeroa zein nanosilika daukaten nahasteen kasuan, ordea, morfologia ez da eraldatzen fluxuaren eraginez. Fluxu oszilakorrak burutu dira nahaste desberdinen ezaugarri biskoelastikoak lortzeko. Neurketa biskoelastikoen bidez lortzen diren erlaxazio-espektroen azterketak morfologian gertatutako aldaketak detektatzeko gai direla frogatzen da.
Polymer, 2019
DOI to the publisher's website. • The final author version and the galley proof are versions of t... more DOI to the publisher's website. • The final author version and the galley proof are versions of the publication after peer review. • The final published version features the final layout of the paper including the volume, issue and page numbers. Link to publication General rights Copyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright owners and it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights. • Users may download and print one copy of any publication from the public portal for the purpose of private study or research. • You may not further distribute the material or use it for any profit-making activity or commercial gain • You may freely distribute the URL identifying the publication in the public portal. If the publication is distributed under the terms of Article 25fa of the Dutch Copyright Act, indicated by the "Taverne" license above, please follow below link for the End User Agreement:
Macromolecules, 2018
Melt memory effects on polymer crystallization are commonly reported in the literature, even when... more Melt memory effects on polymer crystallization are commonly reported in the literature, even when they are not completely understood. In particular, the exact nature of the melt heterogeneities that cause an enhanced nucleation (i.e., the "self-nuclei") is unknown. This is partly due to sensitivity limitations of the experimental techniques employed to study melt memory. In this work, the melt memory effect of semicrystalline polymers is studied for the first time by dielectric measurements. Polycaprolactones of two different molecular weights have been investigated. Isotropic or selfnucleated melt states are obtained, at a given experimental temperature, by cooling from the isotropic melt or heating from the semicrystalline solid, respectively. A detectable decrease in electrical permittivity is obtained for a self-nucleated melt, consistent with the presence of molecular dipoles with restricted mobility in the case of samples displaying crystalline memory. The volume fraction of repeating units involved in the formation of self-nuclei is estimated to be lower than 0.4%. The relative difference in dielectric permittivity between self-nucleated and isotropic melt state shows excellent correlation with rheological measurements that detect an increase in Newtonian viscosity and with the enhancement of nucleation density, measured by DSC. Each of these measured parameters showed a different sensitivity to the presence of self-nuclei, which is linked both to their nature and to the features of the specific measurements. It is suggested that the relatively strong memory effect displayed by PCL, which can be evidenced by different techniques, is related to the presence of weak intermolecular hydrogen-bonding interactions.
European Polymer Journal, 2019
Although various chemistries have been introduced into polyurethanes in order to obtain self-heal... more Although various chemistries have been introduced into polyurethanes in order to obtain self-healing abilities, implementing these materials in applications requiring high strength is challenging as strong materials imply a limited molecular motion, but without movement of polymer chains self-healing is not possible. Here, waterborne poly(urethane-urea)s (PU(U)s) based on aromatic disulfide compounds are developed which balance these contradictory requirements by presenting good mechanical properties at room temperature, while showing the mobility necessary for healing when moderately heated. The influence of hard monomers on the stability and mobility of the materials is investigated by qualitative scratch closure and rheological measurements, so that the limits of the readily available aromatic disulfide compounds, bis(4-aminophenyl)-and bis(4hydroxyphenyl)disulfide, can be determined. Subsequently, a modified aromatic disulfide compound, bis[4-(3'-hydroxypropoxy)phenyl]disulfide, with increased reactivity, solubility and flexibility is synthesized and incorporated into the PU backbone, so that materials with more attractive mechanical properties, reaching ultimate tensile strengths up to 23 MPa, and self-healing abilities could be obtained.
Fluids, 2019
Linear and nonlinear rheological features and electrical conductivity of two nanocomposite system... more Linear and nonlinear rheological features and electrical conductivity of two nanocomposite systems based on polypropylene/multiwall carbon nanotubes (PP/MWCNT) are investigated. The nanocomposites were irradiated with an electron beam following two different procedures. Protocol A, where the nanocomposite mixture is irradiated, and Protocol B where only the PP matrix is irradiated before mixing with MWCNT. The same irradiation dose adjusted to bring about long chain branching (LCB) but not crosslinking, is used in both types of nanocomposites. The modification of the polymer matrix viscosity caused by irradiation determines the MWCNT dispersion and therefore the rheological and percolation thresholds. Elongational flow results reveal that strain hardening, typical of irradiated PPs, is observed for the nanocomposites irradiated, but not for the nanocomposites prepared with the irradiated PP. The hypothesis of a shear flow modification that aligns the branches into the backbone, elim...
Macromolecules, 2017
A novel approach to study self-nucleation in semicrystalline polymers is presented. Self-nucleati... more A novel approach to study self-nucleation in semicrystalline polymers is presented. Self-nucleation, i.e., the peculiar increase of recrystallization kinetics associated with a range of melting temperatures above or below the melting point, is investigated in parallel with differential scanning calorimetry (DSC) and rheological measurements, for a series of metallocene propene/ethylene random copolymers of varying comonomer content. DSC experiments revealed the exact temperature region where self-nucleation effects are detected in the various samples, while with dynamic viscoelastic results the obedience to the time−temperature superposition principle (TTS) is tested, for both self-nucleated and homogeneous melts. Self-nucleated melts do not obey to the TTS principle, contrary to fully isotropic copolymer melts. Such rheological thermocomplexity constitutes the first physical experimental evidence of the presence of melt heterogeneities, which act as self-nuclei when the melt is cooled and recrystallizes. The degree of thermorheological complexity of the different copolymers is quantified and correlated with the original crystalline content of the copolymer.
Proceedings of 6th Eurasphalt & Eurobitume Congress, 2016
Most roads and tunnels in Europe use asphalt mixtures as upper layer due to their excellent prope... more Most roads and tunnels in Europe use asphalt mixtures as upper layer due to their excellent properties, but the fire performance of these materials has been always a subject of discussion. In this paper the study of the fire performance of different asphalt mixes (conventional and modified with different aditives) is reported. The study was carried out at laboratory and full scale. Asphalt mixtures were evaluated at laboratory level using two different tests: The cone calorimeter test, as described in the ISO 5660, and a new test developed to study fire propagation in asphalt mixtures slabs. Then, the best rated modified mixture and the conventional one were tested at full scale using different fire loads in the San Pedro de Anes test tunnel (Asturias, Spain). The main conclusion obtained from the different tests carried out during this four years project is that there is no fire propagation over asphalt mixtures, but a surface degradation in those zones were, due to an external heat source (> 400 ºC), asphalt burns. Results showed in this paper have been obtained in the development of the PAVIREX project, granted by the Spanish "Ministerio de Economía y Competitividad", call "Innpacto 2011".
European Polymer Journal, 2016
The morphology of immiscible 80/20 polypropylene/polyamide 6 (PP/PA) blends that contain differen... more The morphology of immiscible 80/20 polypropylene/polyamide 6 (PP/PA) blends that contain different types of nanosilica and a compatibilizer agent was correlated with their linear and non-linear rheological behavior. Polypropylene grafted with maleic anhydride (PPgMA) was used as compatibilizer agent. Two types of modified silica nanoparticles were added to the blends, one hydrophilic (NSE) and the other hydrophobic (NSH). SEM and TEM microscopy were employed to observe the sea-island morphology of the 80/20 blends. The size of the PA droplets was reduced 12 times when the compatibilizer agent was added; and 25 times when hydrophobic nanosilica (NSH) was additionally included in the formulation. TEM results revealed that NSH particles are preferentially located at the PP-PA interface, whereas NSE particles remain inside the PA droplets. A good agreement between morphology and Small Amplitude Oscillatory Shear tests (SAOS) was observed. At low frequencies a suspension-like rheological behavior was identified for the blends containing nanosilica. The results at intermediate frequencies allowed the evaluation of the shape relaxation time of the droplets. Large Amplitude Oscillatory Shear tests (LAOS) results correlate well with droplets size. The coalescence promoted by flow was investigated, and in the case of the neat binary blend, coalesced blends were obtained. Employing LAOS results determined by measuring blends with a wide range of droplet sizes, an inversely proportional function of a characteristic LAOS parameter with the diameter of the droplets was obtained.
Separation and Purification Technology, 2015
The rheological properties of the ionic liquid 1-hexyl-3-methylimidazolium chloride ([hmim][Cl]) ... more The rheological properties of the ionic liquid 1-hexyl-3-methylimidazolium chloride ([hmim][Cl]) along with that of its mixtures with CuCl, which form the corresponding chlorocuprate(I)-based ionic liquids ([hmim][Cu(Cl)x]) are reported. In addition, the flow behaviour of these ionic liquids is thoroughly described for the first time. In previous works we have reported that these Lewis-acid-based ionic liquids exhibit high chemisorption capacity towards carbon monoxide which can be employed to design novel ionic liquid-based CO separation processes. Therefore, accurate knowledge of the transport properties is of utmost importance given the considerable influence of viscosity on mass transfer. Results showed that both [hmim][Cl] and [hmim][Cu(Cl)x] ionic liquids exhibited shear-thinning non-Newtonian behaviour associated to the presence of a hydrogen-bonding network. However, the onset of shear-thinning progressively shifted to higher frequencies upon increasing temperature for all measured samples. Moreover, a drastic [hmim][Cl] viscosity decrease from 14.2 to 3.98 Pa s was observed after addition of 2 mol CuCl L−1 at 293 K. In addition, the parameters of Cross model that describes shear-dependant viscosity have also been obtained.
Materials Sciences and Applications, 2013
The aging of bitumen has a significant impact on the mechanical behavior of asphalt. This aging i... more The aging of bitumen has a significant impact on the mechanical behavior of asphalt. This aging is carried out at the mixing operation with the aggregates generally at 163˚C in the case of pure mixtures or at temperatures higher than in the case of the modification by polymers or industrial waste. This paper presents experimental results of a study of the rheological behavior of a class of bitumen 40/50 to the artificial aging. Three aging temperatures were selected: 163˚C, 173˚C and 183˚C. From obtained results, a study of the risk of deformation of asphalt is performed, based on the results of correlation between the behavior of the coated and his binder deducted SHRP specifications and technical advice French. These results show that the stiffness of the aged binders increases with aging temperature. Moreover, there is no risk of rutting and fatigue cracking for thermal coated projected.
RSC Advances, 2015
Is it possible to blend two immiscible polymer networks starting from their cured state? A simple... more Is it possible to blend two immiscible polymer networks starting from their cured state? A simple thermomechanical approach permits blending two dynamically crosslinked polymer networks, to give blends with superior mechanical properties.
Polymer Engineering & Science, 1996
Dynamic viscoelastic measurements and extrusion rheometry results of immiscible and partially mis... more Dynamic viscoelastic measurements and extrusion rheometry results of immiscible and partially miscible PVC/EVA blends from 50 to 90 wt% in PVC are presented and compared with those of plasticized PVCs. From loss modulus data the plateau modulus, G o N , associated with entanglements, is calculated. The variation of G o N with composition is analyzed using the theory of Tsenoglou. A simple model, which accounts for the effect of a structural parameter and the effect of free volume, is used to adjust viscosity data, taken at several frequencies and shear rates. For both types of blends, best fits are obtained using a model that establishes that the free volume of each polymer is not measurably altered by the other.
Polymer Composites, 2014
The properties of multiwall carbon nanotubes (MWCNT)/polyurethane (PUR) nanocomposites after bein... more The properties of multiwall carbon nanotubes (MWCNT)/polyurethane (PUR) nanocomposites after being submitted to flow, i.e., in conditions similar to their application as electrically conductive adhesives (ECA), are investigated. A decrease of the elastic modulus is observed after flow is stopped, compatible with a rearrangement of the MWCNT/PUR network during flow. The implications of the viscoelastic results on probe-tack data are elucidated and a slightly higher energy of adhesion is observed for sheared samples. Dynamic viscoelastic measurements reveal that crystallization of PUR is fastened with MWCNTs, shortening the solidification process for samples submitted to flow or not. Electrical conductivity results show that the 4 wt% MWCNT/PUR nanocomposite can be submitted to flow and give, on cooling to room temperature, values of the electrical conductivity between 10 22 and 10 21 Siemens / m. 2 wt% MWCNT/PUR sample presents a shear induced semiconductor to insulator transition and a temperature-induced isolator to semiconductor transition. We conclude that MWCNT/PUR nanocomposites are good candidates to develop Hot Melt ECAs, since they display satisfactory viscosity, tack, crystallization (linked to permanent adhesion), and electrical conductivity.
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Papers by Antxon Santamaria