Recerca i desenvolupament sobre materials polimèrics polifuncionals. Es tracta de nanocomposites lleugers, amb una acurada composició a base de polímers, nanopartícules de diversa naturalesa (grafè, òxids, silicats...) i celles gasoses. Ja sigui en forma compacta (films i làmines, principalment) com cel•lular (escumes, aerogels i membranes) permeten satisfer les més exigents demandes d'eficiència que imposen els sectors industrials punters als materials d'enginyeria, als quals s'exigeix, a part d'un baix cost, lleugeresa, durabilitat i respecte pel medi ambient. Amb la nostra recerca pretenem potenciar el concepte de polifuncionalitat en els materials polimèrics, amb l'objectiu general de fer que un mateix material pugui satisfer més d'una funció en una determinada aplicació, com a conseqüència d'un conjunt particular de propietats que resulten d'una precisa composició química i d'un racional control estructural aplicat durant el seu processament.
The structural modifications of a commercially available poly(lactid acid) grade were induced through reactive extrusion using a multi-epoxide reactive agent in a pilot plant. The statistical nature of the chemical reactions led to the generation of several types of non-uniform molecular architectures. Even though conventional spectroscopic (NMR) or chromatographic (SEC-static light scattering) techniques are placed at the forefront of the molecular characterization, both methods usually failed in characterizing non-uniform structures. In this study, a promising approach was applied to automatically classify modified PLA samples. It is based on the analysis of FTIR spectral data by means of multivariable methods, including feature extraction and classification algorithms. The fast and accurate results presented in this paper show the potential of the proposed approach.
Gomez, J.; Sanchez-Soto, M.; Maspoch, M. Composites. Part A, applied science and manufacturing Vol. 104, p. 1-13 DOI: 10.1016/j.compositesa.2017.10.014 Data de publicació: 2018-01-01 Article en revista
The aim of the present work is to analyze the morphology, mechanical properties and fracture behaviour of solid and foamed plates made of glass fiber-reinforced PP. The morphology exhibited a solid skin/foamed core structure, dependent on the foaming ratio. Simulation of the microcellular injection molding process with Moldex 3DR software provided a good approach to the experimental results. The flexural properties and impact resistance showed lower values as the apparent density decreased, but constant specific properties. The fracture characterization was carried out by determining the Crack Tip Opening Displacement (CTOD) at low strain rate, as well as the fracture toughness (KIc) at impact loading. Foamed specimens presented higher values of CTOD than the solid ones and higher as the foaming ratio increases, due to cells acting as crack arrestors by blunting the crack tip. However, the fracture toughness KIc decreased with decreasing the apparent density. Anisotropy due to fiber orientation was also observed. Fibers were aligned in the filling direction in the surface layers, while they were oriented in the transverse direction in the core. According to the amount of fibers oriented in one direction or another, different properties were obtained
Matta, F.; Martelli, S.; Caon, T.; Velasco J.I.; Cardoso, R.; Bilck, A.; Innocentini, L. LWT-food science and technology Vol. 87, p. 293-300 DOI: 10.1016/j.lwt.2017.08.056 Data de publicació: 2018-01-01 Article en revista
In this study, edible films were prepared with different wheat gluten (GLU) and gelatin (GEL) ratios by the solvent casting technique using glycerol (GLY) or sorbitol (SOR) as plasticizers. Fatty acids (caproic, caprylic, capric, lauric, myristic or palmitic) were also added to a previously selected GLU/GEL/sorbitol film, and the effect of GLU:GEL proportion and type of fatty acid on the film properties were tested. Films plasticized with GLY presented a more significant reduction in the elongation at break (EB). In contrast, films plasticized with SOR did not show a significant difference in the EB. The film's water vapor permeability (WVP) and acid solubility increased with increasing proportions of GEL while the water solubility was decreased. On the other hand, the elongation at break of the films decreased with increasing GEL content, which may be associated with its more rigid structure. The addition of fatty acids resulted in lower WVP and the plasticizing effect was dependent on the degree of interaction with the proteins of the film (identified by thermal analysis). The GLU:GEL proportion and the type of fatty acid affect the film properties (mechanical, solubility, opacity, water vapor barrier), allowing the development of new materials with different and useful functional properties according to the desired application
Several commercial grades of homo-polymer and its blends were selected to prepare microporous membranes through melt extrusion-annealing-uniaxial stretching technique (MEAUS). Branched or very fluid polypropylene was employed to modify the polymeric composition. In some blends, micro-sized calcium carbonate was added. We analysed the influence of sample composition, extrusion draw ratio, and we performed a deep study concerning the uniaxial strain rate, using in some cases extreme strain rates and strain extents. The crystalline features were studied by Differential Scanning Calorimetry (DSC), and the morphology of porous structure was analysed through Scanning Electron Microscopy (SEM). Thermal stability and thermomechanical performance was measured by thermogravimetric analysis (TGA) and dynamic-mechanical-thermal (DTMA) study. A close relationship was found between crystalline characteristics, porous morphology and the trends registered for permeability
The fracture of a ductile polymer film, a heterophase ethylene-propylene block copolymer, has been studied, combining a range of characterisation methods in an attempt to provide a better understanding of the intricate details that play an important role in the repeatability and reproducibility of the essential work of fracture test. The experimental factors that have a strong influence on the resulting parameters are clearly explained, with particular attention to the effect of the quality of the notches, the non-collinearity of the two edge notches in double edge notched tension specimens, and the lack of alignment of the specimen with the load axis once it is mounted on the load train. Furthermore, the influence of these experimental factors on the registered stress-displacement curves is also studied, and a criterion and the method for separating non-valid specimens are established.
Carrasco, F.; Santana, O.; Cailloux, J.; Sanchez-Soto, M.; Bou, J. J.; Maspoch, M. Congreso Interamericano de Computación Aplicada a la Industria de Procesos p. 943-952 Data de presentació: 2017-09-27 Presentació treball a congrés
En este trabajo se han fabrico, mediante extrusión reactiva, láminas de 1 mm de espesor de ácido poliláctico y de su nanocompuesto con un 2.5% en masa de montmorillonita organomodificada. En este proceso de extrusión reactiva se ha utilizado un extensor de cadena, al 0.5% en masa, con el fin de mejorar las propiedades de estos materiales. Se ha empleado la ecuación analítica general para evaluar los parámetros cinéticos de la descomposición térmica del PLA y de su nanocompuesto. Se han analizado diferentes mecanismos empíricos y teóricos de reacciones en estado sólido con el fin de elucidar cuál es el mejor modelo cinético. Para alcanzar este objectivo, se han construido las funciones de conversión estandarizadas, f(a)/f(0.5). Puesto que estas curvas patrón suministran información tan solo cualitativa, se ha propuesto un índice cuantitativo, basado en el error medio integral (EMI) entre los valores teóricos y experimentales de la función de conversión estandarizada. De esta forma, ha podido demostrase que el mejor modelo cinético teórico es el de escisión aleatoria de cadenas macromoleculares. La presencia de nanopartículas ha sido beneficiosa, al mejorar la resitencia a la degradación térmica del PLA.
Cailloux, J.; Abt, T.; Garcia, V.; Santana, O.; Sanchez-Soto, M.; Carrasco, F.; Maspoch, M. International Conference on Biobased and Biodegradable Polymers p. 1-2 Data de presentació: 2017-09-12 Presentació treball a congrés
Fakhouri, F.; Dambrós, A.; De Sousa Pais, M.; Innocentini, L.; Yamashita, F.; Velasco J.I. International Conference on Biodegradable and Biobased Polymers Data de presentació: 2017-09-12 Presentació treball a congrés
Bin, R.; Cailloux, J.; Santana, O.; Bou, J. J.; Sanchez-Soto, M.; Odent, J.; Raquez, J.; Dubois, P.; Carrasco, F.; Maspoch, M. Journal of applied polymer science Vol. 134, p. 45367-45379 Data de publicació: 2017-06-14 Article en revista
Films of an architecturally modified poly(lactic acid) (PLAREx) with three different types of fumed silica nanofillers (SiO2) were processed through reactive extrusion-calendering in a pilot plant. The effects of the SiO2 type on both the dispersion and the crystallization behaviour under dynamic and isothermal conditions are investigated using transmission electron microscopy (TEM) and differential scanning calorimetry (DSC). The mechanical properties are assessed by tensile testing. TEM micrographs showed that the improved chemical affinity of both surface-treated SiO2 towards PLAREx end groups did not improve particle dispersion. DSC results revealed that untreated SiO2 nucleated PLAREx more efficiently than both surface-modified silicas. The activation energy for the isothermal crystallization process, as determined by an Arrhenius method, suggests that addition of untreated SiO2 enhances the crystallization rate of PLAREx. However, it seems that the tensile behaviour remained unchanged whether silicas were added or not.
Martinez, A.; León, N.; Segovia, A.; Cailloux, J.; Martínez, P. Engineering fracture mechanics Vol. 180, p. 296-314 DOI: 10.1016/j.engfracmech.2017.06.007 Data de publicació: 2017-06-07 Article en revista
The essential work of fracture approach has been employed to analyse the effect of notch sharpening on the fracture toughness of a semicrystalline multiphase ethylene-propylene block copolymer. Double edge notched tension specimens were sharpened using different techniques: femtolaser ablation, razor blade sliding at room and liquid nitrogen temperatures, saw cutting, plastically deformed saw cutting, and scalpel sliding. The notch sharpening techniques provide notches of different quality in relation to both the notch tip radius and the plastic deformation in front of the crack tip. The best quality notches were produced by the femtolaser ablation technique, which provides very sharp notches without plastic deformation ahead of the crack tip. The effects of the non-collinearity of the notches and tilted specimens on the testing machine grips were also analysed. The shape of the registered stress–displacement curves shows differences, but only in the range comprised between the displacements corresponding to the maximum stress and the onset of crack initiation. A larger crack tip radius and/or larger extent of plastic deformation in front of the notch root leads to larger values of the displacement at the onset of crack initiation, resulting in higher values for the specific essential work of fracture. Yet on the other hand, the values of the slope of the essential work of fracture plot remain unchanged. A lower value for the specific essential work of fracture was obtained for the specimens sharpened using the femtolaser ablation technique.
Square plates (nominal tickness: 3 mm, nominal width: 100 mm) of diferent rheolgically modified PLA/acrylonitrile-butadiene-styrene (ABS) blends were manufactured through injection molding process. During processing, the properties of the melt were stabilized and enhanced by the addition of a styrene-acrylic multi-functional-epoxide oligomeric reactive agent (SAmfE). The general analytical equation has been used in order to evaluate the kinetic parameters of the thermal degradation of PLA-REX, ABS and its bioblend with a weight content of 70/30. Various empirical and theoretical solid-state mechanisms have been tested to elucidate the best kinetic model. In order to reach this goal, activation energy values were calculated by means of the Kissinger–Akahira–Sunose method. On the other hand, the standardized conversion functions have been constructed. Given that it is not always easy to visualize the best accordance between experimental and theoretical values of standardized conversion functions, a recently proposed index has been determined to quantitatively support our findings relative to the best reaction mechanisms. It has been demonstrated that the best mechanism for the thermal degradation of PLA-REX and ABS was the random scission of macromolecular chains. The bioblend thermal degradation occurred in two steps: the first step (a < 60%) took place through an R2 mechanism whereas the second step (a > 75%) did it according an F3 mechanism. Moreover, y(a) master plots have also been used in order to confirm that the selected reaction mechanisms were adequate.
The present work deals with foaming plastic materials in order to reduce weight, cost and carbon footprint in automative parts. Glass-fiber-reinforced polypropylene (PP GF) was injection-modded in the solid and foamed states by means of the already known MuCell process and a newly emerged technology. IQ Foam, developed by Volkswagen AG. Both processes were combined with the complementary tool technology of core-back expansion molding. By increasing the thickness of the part, the apparent density decreased but the flexural stiffness was greatly enhanced. The new IQ Foam technology is able to produce foamed parts with properties compareble to that of the MuCell process, offering additional benefits such as cost-effectiveness, ease of use and machine-independence.
PLA/ABS: 70/30 w/w blends have attracted special interest in the automotive industry being its main handicap the absence of miscibility between phases. The emphasis is focused on the content of renewable raw materials in order to reduce CO2 emissions associated with the finished product. Most of the scientific communications reports the need to perform a compatibilization between these phases using a third polymer with reactive groups based on epoxide groups or anhydride . In this study we propose to profit the residual reactivity, due to the unreacted epoxide groups of the “grafted”
multifunctional chain extender, of a PLA modified by reactive extrusion with a commercial multiepoxide olygo-copolymer (REX-PLA) . The aim of this communication is to analyse the influence of remanent reactivity of REX-PLA and the addition of an Maleic Anhydride grafted ABS (ABS-g-MAH) as a external compatibilizer on the morphology and fracture behavior at low strain rates of extruded sheets prepared form REX-PLA/ABS Bioblends. According to the calorimetric fractionation technique SSA, the confinement effect observed in the PLA phase of Bioblend without ABS-g-MAH is lost with the addition of grafted copolymer, which can be correlated with the thinner stratified morphology of ABS phase obtained when grafted terpolymer is added as observed by SEM analysis. The fracture behavior after one week of storage at
room temperature was evaluated by applying the concept of the Essential Work of Fracture (EWF) on DDENT specimens. Although the Load-displacement traces seem to satisfy the requirements of the technique, the only system that preserves the behavior when varying the length of ligament is of the one with 3%w/w of ABS-g-MAH added, being practically impossible to apply the technique in the other mixtures given the instability and great dispersion that presented during the crack propagation
stage. The addition of only 3% by weight of ABS-g-MAH causes an increase of almost 50% in the work necessary to start crack propagation (essential term of the concept, we) with respect to its nonaddition, and almost 70% when compared to Rex-PLA . The above allows asserting that the effect of physical aging seems to be minimized with the addition of this functionalized terpolymer. The correlation of the results obtained with the morphology generated during the processing and that
has been evaluated by observations of cryogenic fracture surfaces in parallel (MD) and perpendicular (TD) directions to the extrusion direction, allows to assert that an appropriate control of the conditions of the calendering stage can generate a synergistic effect on the final performance of these blends.
Within the framework of industrial production, poly (lactic acid) (PLA) is the front runner in the emerging bio-based and compostable plastic market. Despite all its advantages, some PLA properties have been its principal drawbacks for large-scale commercial applications. They include its advanced brittleness at room temperature, low melt strength and its poor thermal resistance. Among all the promising techniques developed to overcome these issues, polymer blending represents one of the interesting approaches to implement PLA into high-value and durable applications. In the present investigation, an evaluation of the miscibility extent between PLA and a predominantly biobased Polyamide 1010 (PA) is proposed, upon either melt blending or reactive melt blending, in order to tune both morphologies and mechanical properties. Dependence between morphology and toughness improvement was established in terms of average size and related size-distribution of the dispersed
PA within the PLA matrix, as shown using SEM. The overall results suggested an improvement of the distribution coupled with a reduction of the PA average size particles through reactive melt blending using a melt strengthened PLA extrusion grade (REX-PLA). Under tensile loading, the aforementioned PA size-distribution enhanced plastic deformation, thus drastically improving PLA toughening.
The healing of chronic wounds requires intensive medical intervention at huge healthcare costs. Dressing materials should consider the multifactorial nature of these wounds comprising deleterious proteolytic and oxidative enzymes and high bacterial load. In this work, multifunctional hydrogels for chronic wound application were produced by enzymatic cross- linking of thiolated chitosan and gallic acid. The hydrogels combine several beneficial to wound healing properties, controlling the matrix metalloproteinases (MMPs) and myeloperoxidase (MPO) activities, oxidative stress, and bacterial contamination. In vitro studies revealed above 90% antioxidant activity, and MPO and collagenase inhibition by up to 98 and 23%, respectively. Ex vivo studies with venous leg ulcer exudates confirmed the inhibitory capacity of the dressings against MPO and MMPs. Additionally, the hydrogels reduced the population of the most frequently encountered in nonhealing wounds bacterial strains. The stable at physiological conditions and resistant to lysozyme degradation hydrogels showed high biocompatibility with human skin fibroblasts
In this study low density poly-ethylene (LDPE)/electrical cable waste blends were prepared using asingle-screw extruder at pilot plant level. The cable waste was mainly composed of LDPE, synthetic rubbers, flexible poly-vinyl chloride (PVC) and traces of conductive metal. Recycled LDPE was recovered by using the gravimetric separation approach. Heterogeneous extruded filaments were obtained because of the presence of not-melted waste particles that caused the interruption of the extrusion process. In order to improve the mixing and the homogeneity of the extruded filaments, LDPE waste was collected usingnest sieves with opening mesh of 1.68 and 0.59 mm. The mechanical properties of the blends were related to the LDPE waste content and processing. In general, the mechanical parameters corresponding to the heterogeneous extruded filaments were notoriously lower than the LDPE because of large and not-meltedwaste particles caused the premature failure of thematerial. The blends containing sieved LDPE waste particles showed higher values in stiffness and ductility with respect to the rest of the blends.
A novel assessment method based on three-dimensions technology has been proposed for analysing the surface quality of injection-molded parts. Starting from a mold having a leather texture engraved on it, the quality of replication on the surface of a polypropylene molded part has been studied as a function of the injection parameters. In order to establish a relationship between quality appearance and surface topography, amplitude parameters and functional parameters have been compared. A white light interferometer (WLI) was used to assess the surface and a scanning electron microscope (SEM) was employed to detect small features on the surface. The results indicated that, in terms of quality perception, functional parameters are more accurate than amplitude parameters for quantifying the mold replication on the polypropylene surface
El objetivo de este trabajo ha sido estudiar el efecto de la adición de un ABS funcionalizado con un 0,6 % molar de Anhídrido Maléico (ABS-g-MAH) en el comportamiento a fractura a bajas velocidades de solicitación de mezclas
REX-PLA/ABS preparadas mediante extrusión reactiva. Se ha aplicado el concepto de Trabajo Esencial de Fractura sobre láminas extruidas a partir de las mezclas y almacenadas durante una semana a 25ºC. La adición de tan solo un 3
% w/w de ABS-g-MAH ocasiona un incremento de un 163% en el trabajo necesario para inicio de propagación de grieta (término esencial del concepto, we) respecto al REX-PLA o su no adición a la mezcla. Esto es consecuencia de un
efecto combinado entre la morfología laminar estratificada fina generada y el incremento en la interacción entre las fases. Esto fomenta que el mecanismo principal de deformación involucrado sea la cavitación de partículas de
butadieno, disminuyendo la proporción de la cavitación de la fase ABS. Lo anterior permite aseverar que el efecto del envejecimiento físico de la fase PLA parece ser minimizado con la adición de este terpolímero funcionalizado.
Double edge notched tension (DENT) specimens of a polyethylene terephthalate (PET) film were tested in an universal testing machine, measuring the displacements and the ligament lengths with a digital image correlation (DIC) system. With these data the essential work of fracture (EWF), crack tip opening displacement (CTOD), and the J-integral fracture methods were compared. The specimens were tested in mode I under plane stress conditions, verifying that the crack always propagated through a fully yielded ligament. It has been proved that we, the specific essential work of fracture was the specific energy just up to crack initiation and has the same value that J-integral at crack initiation, Jo. The relationship of these parameters with the CTOD was also shown. The influence of the notch quality on the fracture behaviour when the specimens were sharpened by two different methods, femtosecond laser ablation or by razor blade sliding, has also been analysed in detai
ABS (acrylonitrile-butadiene-styrene) copolymer is one of the most used engineering polymers due its good combination of properties and low cost, being vastly used in industrial sectors such as automotive, construction, electrical and electronic. Nevertheless, ABS is highly flammable, generating gases and toxic fumes during combustion. Traditionally, the improvement of ABS’s flame retardancy has been associated to the use of brominated additives, very effective at low concentrations. Nonetheless, the use of these halogenated flame retardants has been highly limited due to recent European environmental restrictions, converting in critical to find alternative halogen free flame retardant formulations.
The present work focuses on the study of the fire behaviour of ABS-based foams prepared by supercritical CO2 dissolution containing different amounts of halogen free phosphate flame retardants, particularly ammonium polyphosphate (APP) and aluminium diethyl phosphinate (AlPi), and the possible synergistic effects of combining said flame retardant formulations with different types of nanoparticles.
It is shown that the addition of the phosphate flame retardants to ABS leads to higher ABS initial decomposition temperatures determined by thermogravimetric analysis, which was related to a synergistic effect between ABS, APP and AlPi, delaying the release of ammoniac and advancing the liberation of water , as well as to lower values of the maximum peak of heat release rate (PHRR) and lower effective heats of combustion obtained by cone calorimetry. Further enhanced flame retardancy was observed when montmorillonite nanoclay, layered double hydroxides and/or nanosilica were used in combination with the phosphate flame retardants, resulting in a more cohesive protective layer during the cone calorimeter tests and as a result in lower PHRR values.
The results presented here demonstrate the great potential of nanoclays, layered double hydroxides and nanosilica as effective synergists in halogen free flame retardant formulations for ABS-based foams.
The increasingly demanding industrial requirements for materials with enhanced specific and functional properties have aroused a great interest in the development of polymer nanocomposite foams by combining foaming with the addition of nanosized reinforcements. Among these, carbon nanoparticles-based materials have been gaining importance due to their high mechanical and transport properties, which for instance could overcome some limitations of conducting polymers, such as low thermal stability and poor mechanical performance.
On the other hand, there is still lack of information regarding possible changes in the microstructure of polymer foams due to the addition of nanosized phases and foaming and their relation with the final properties. These microstructural changes have already been shown to influence the properties of polycarbonate (PC) nanocomposites, for instance resulting in significant thermal stability improvements.
This work studies the effects of adding conductive carbon-based nanoparticles and foaming on the microstructure of polymer foams, particularly polypropylene (PP) and PC foams, and how this microstructure affects the final properties. To this end, polymer nanocomposite foams containing graphene nanoplatelets (GnP) were prepared by both one and two-step supercritical CO2 dissolution and analyzed by Raman spectroscopy.
Raman spectroscopy allowed to correlate the changes in characteristic bands related to intrachain and interchain molecular ordering, for instance showing that while the simultaneous presence of GnP and CO2 during one-step foaming induced the mobility of PC molecules and led to partially crystalline foams, foams prepared in two-steps resulted fully amorphous. In these foams the lower CO2 dissolution temperatures were not enough to favour molecular ordering, GnP addition further limiting molecular rearrangement. In addition, shifting of the G and G’ bands of GnP was detected in the nanocomposite foams and related to an improved separation and exfoliation of the nanoplatelets during foaming, especially in the case of foams prepared by one-step foaming.
La presente tesis doctoral se enmarca dentro del Plan de Doctorats Industrials convocado por la Generalitat de Catalunya y se ha desarrollado como colaboración entre la Universitat Politècnica de Catalunya-BarcelonaTech, el Centre Català del Plàstic, SEAT SA y Volkswagen AG. El proyecto de investigación tiene como principal objetivo la caracterización de plásticos microcelulares, motivado por el interés en reducir peso, coste e impacto ambiental en piezas de plástico de automoción.En primer lugar, se obtuvieron mediante moldeo por inyección barras cilíndricas y placas cuadradas fabricadas con Acrilonitrilo-Butadieno-Estireno (ABS) y Polipropileno reforzado con un 20% de fibra de vidrio (PP 20GF), espumadas con la tecnología MuCell®. El volumen de dosificación es el parámetro más influyente sobre la estructura celular y las propiedades a tracción y a flexión. El efecto de la temperatura de molde y velocidad de inyección, en cambio, es secundario y no introduce variaciones estadísticamente significativas sobre el rendimiento mecánico.Las propiedades a tracción y flexión se reducen de manera prácticamente lineal con la disminución de densidad, mientras que la resistencia a impacto decrece drásticamente debido a la espumación. El efecto reforzante de las fibras de vidrio contribuye a compensar parcialmente la caída de propiedades debido a la reducción de densidad. Las celdas tienden a enromar el frente de grieta, retrasando así el inicio de propagación. Sin embargo, una vez la grieta comienza a propagar, las celdas actúan como concentradores de tensión provocando una disminución en la tenacidad a fractura. El reducido contenido de agente espumante inyectado durante el proceso de espumación no es suficiente para producir cambios en las propiedades térmicas en comparación con las del material macizo.La simulación del proceso de inyección microcelular con el software Moldex 3D® y los modelos de predicción de propiedades mecánicas basados en la densidad y características morfológicas proporcionaron valores cercanos a los obtenidos experimentalmente.Por otro lado, en este trabajo también se estudió el efecto de la tecnología de molde Core Back en combinación con el proceso de espumado mediante moldeo por inyección. A través del movimiento de la cavidad y el aumento del espesor final de la pieza inyectada, la densidad aparente se reduce al mismo tiempo que la rigidez a flexión se incrementa considerablemente. Finalmente, una nueva tecnología de espumación desarrollada por Volkswagen AG, llamada IQ Foam®, se utilizó para la inyección de placas rectangulares y la comparación de sus propiedades con las de placas análogas obtenidas mediante el proceso MuCell®. Mediante la utilización de un contenido mínimo de agente espumante, las placas espumadas con IQ Foam® exhibieron mayores espesores de piel y menores densidades celulares, y por tanto, propiedades mecánicas ligeramente superiores. Esta nueva tecnología ofrece también otras ventajas, como una menor inversión inicial, facilidad de operación y posibilidad de utilización en cualquier máquina de inyección convencional.
Cyclic butylene terephthalate (CBT®) oligomers are a relatively new class of material and are capable of polymerizing in an entropically driven ring-opening polymerization into high-molecular-weight polymerized CBT (pCBT) in very short times, i.e., within minutes. The most important feature of CBT is its very low, water-like melt viscosity prior to polymerization which gives rise to an excellent impregnation of fibrous reinforcements in contrast to conventional, high viscous thermoplastic resins. This opens up new possibilities in the thermoplastic composite production since thermoplastic-based composites show some advantages over thermoset-based ones. Specifically, they have a higher toughness and impact strength and they can be welded, postformed, and recycled due to their thermoplastic nature. CBT has the potential to substitute thermoset matrices in fiber-reinforced composites and may solve some of the today´s recycling issues associated with thermoset-based composites. Moreover, the low melt viscosity of CBT enhances the dispersion of nano- or conductive particles and can yield superior nano- and conductive composites. This article reviews the recent advances in processing–structure–property relationship, physical and chemical modification of pCBT, as well as the preparation of fiber-reinforced pCBT composites, pCBT nanocomposites, and conductive pCBT composites.
Rodríguez, M.; Cuesta, I.; Maspoch, M.; Belzunce Varela, Javier Theoretical and applied fracture mechanics Vol. 86, p. 78-83 DOI: 10.1016/j.tafmec.2016.10.001 Data de publicació: 2016-12-01 Article en revista
The aim of this paper is to demonstrate the applicability of the Small Punch Test (SPT) in the mechanical characterization of polymers, following previous achievements in metallic materials. For this purpose, different polymers with a wide variation of tensile properties were examined. The applicability of this type of test to characterize polymeric materials is especially interesting when these products are in the form of films, as their greatly reduced thickness enables an easy preparation of the SPT specimens.
All the polymer materials were characterized by means of small punch and tensile tests. The tensile stress-strain curves were compared with the load-displacement SPT curves and the representative SPT parameters were defined accordingly. A good correspondence was found between the tensile elastic modulus and the initial slope of the SPT plot (Slopeini/t), with t being the specimen thickness, and a good correlation was also observed between the tensile yield strength and the SPT Pym/t2 parameter. On the contrary, no corresponding relationship was found to predict the ultimate tensile strength or the failure elongation, since these properties depend greatly on the stress state of the test (uniaxial or biaxial).
Fakhouri, F.; Velasco J.I.; Dambrós, A.; Martelli, S.; De Sousa Pais, M.; Inocentini, L. Journal of Bioremediation and Biodegradation Vol. 7, num. 6 (Supl.), p. 65- DOI: 10.4172/2155-6199.C1.006 Data de publicació: 2016-12 Article en revista
The trend towards environmental preservation and the need for new sources of raw materials to reduce dependence on oil
are a major incentive for the development. The use of edible and biodegradable films obtained from renewable materials,
thus reduce the use of petroleum-derived polymers. The babassu (Orbignya sp) is a palm of great socio-economic importance
in Brazil, especially in the states of Maranhão, Piauí, Tocantins and Mato Grosso. The babassu consists of exocarp, mesocarp
and endocarp. The mesocarp is composed of 60% starch. The starch structure resembles the structure of starch found in cereals
such as corn. The starch is widely used in the preparation of biodegradable films for its thermoplastic capacity. The starch
gelation temperature ranges from 63-73ºC, similar to corn starch, in addition to presenting a considerable amount of amylose.
In this context, the objective of this study was to use the flour made from babassu mesocarp to produce biodegradable films by
thermoplastic extrusion process. For the process, an extruder brand BGM (EL-25 model, SãoPaulo, Brazil) was used with the
processing conditions demonstrated by Farayde (2009). For the preparation of the sample babassu mesocarp flour was used
and as a plasticizer, 30% glycerol in relation to the mass of flour. After extrusion, the film was conditioned for 48 hours at 25°C
and 50% RH so as to be characterized as to its thickness, permeability to water vapour (PWV) and for its solubility in water and
acid. The film extrudate showed a dark coloration through the naked eye and was malleable to the touch and had an average
thickness of 0.5353 mm. The babassu film was 100% soluble in acid and approximately 40% soluble in water.
Lightweight bio-based aerogels from sustainable gum Arabic (GA) and sodium montmorillonite (Na+-MMT) clay were prepared by means of a simple freeze-drying process. GA/clay aerogels showed high porosity (87.9%–94.9%) of mainly open type and the mechanical properties were improved by the clay. When 40% of clay was added to pure GA, the specific modulus and the absorbed energy of resultant aerogels increased by 1.6 and 4.2 times respectively. On the other hand, the exponent value for modulus in the power-law model for cellular materials increased from 1.95 to 3.28 due to the more anisotropic structures induced by the presence of the clay. In terms of thermal stability and flame retardancy, clay content played a dominant role. With 50% of clay loading, the initial decomposition temperature increased by nearly 16 °C and the peak of heat release rate was 3-fold reduced.
In the present work, poly(lactic acid) sheets (with a nominal width of 1 mm) reinforced with organically modified montmorillonite (with a mass content of 2.5%) have been manufactured through a reactive extrusion process. A chain extensor (with a mass content of 0.5%) has been used in order to improve poly(lactic acid) properties. The kinetics of the thermal degradation has been analyzed by means of the general analytical equation. Various empirical and theoretical solid-state mechanisms have been tested to elucidate the best kinetic model. In order to reach this goal, master plots have been constructed by means of standardized conversion functions. Given that it is not always easy to visualize the best accordance between experimental and theoretical values of standardized conversion functions, a new index, based on integral mean errors, has been developed to quantitatively discern the best mechanism. By doing that, it has been possible to ascertain that random scission of macromolecular chains was the best kinetic model. The presence of nanoparticles has been beneficial, thus enhancing the thermal resistance of poly(lactic acid).
A unique set of double-edge notched tension specimens of a Polyethylene Terephthalate Glycol-modi¿ed ¿lm was tested in mode I, plane stress. The load was registered on a universal testing machine. The displacements, ligament lengths, and video frames were recorded by a Digital Image Correlation system. With these registered data, the essential work of fracture, J-integral, and crack tip opening displacement (CTOD) fracture concepts have been applied. The onset of crack initiation was through a complete yielded ligament. The analysis showed that the intrinsic speci¿c work of fracture, we, is the speci¿c energy just up to crack initiation, which is an initiation value. we has both a coincident value and the same con-ceptual meaning as Jo, the J-integral at the onset of crack initiation. The relationship between Jo and CTOD is also determined. The in¿uence on the notch quality when the specimens were sharpened by two different procedures, femtosecond laser ablation and razor blade sliding, was analysed in detail.
Cailloux, J.; Bin, R.; Santana, O.; Bou, J. J.; Raquez, J.; Dubois, P.; Maspoch, M. Reunión del Grupo Especializado de Polímeros (GEP) de la RSEQ y RSEF p. 159-161 Data de presentació: 2016-09-08 Presentació treball a congrés
Since poly(lactic acid) is a n environmentally friendly aliphatic polyester with mechanical pe rformances similar to those of PS or PET, it has been viewed as a promising alternative to petroleum - based commodity polymers. However, it uses in high performance applications ( i.e. electronic, automotive, etc.) is still complicated due to both its insuff icient thermal stability during processing and its slow crystallization rate. On this basis, this work aims in investigating the thermal stability and the nucleation/crystallization ability of a melt strengthened PLA (referred to as REX - PLA) through the ad dition of 3D reactive fumed silica nanofillers via reactive extrusion at pilot plant
Santana, O.; Cailloux, J.; Sanchez-Soto, M.; Carrasco, F.; Maspoch, M. Reunión del Grupo Especializado de Polímeros (GEP) de la RSEQ y RSEF p. 156-158 Data de presentació: 2016-09-08 Presentació treball a congrés
Maspoch, M.; Santana, O.; Cailloux, J.; Sanchez-Soto, M.; Bou, J. J.; Carrasco, F. Reunión del Grupo Especializado de Polímeros (GEP) de la RSEQ y RSEF p. 30-31 Data de presentació: 2016-09-07 Presentació treball a congrés