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Foam-like aerogels based on biodegradable polymers and sodium montmorillonite (Na+-MMT) clay were prepared through an environmentally friendly freeze-drying process. Both synthesized and bio-based polymers were utilized in this thesis, including polyvinyl alcohol (PVOH), carboxylmethylcellulose (CMC), xanthan gum, agar, Arabic gum and starch. The morphologies of aerogels were characterized using scanning electron microscopy. The mechanical properties investigation included compression and impact tests. Porosities and solid densities were measured using a helium pycnometer while the pore size distribution was determined by automated mercury porosimeters. Most of polymer-clay aerogels exhibited porous and layered structures that were formed via ice templating. However, high viscosity of the precursor solution may break the layered architecture by retarding the formation of ice crystals (e.g. 2.5 wt% agar aqueous solution). The structures as well as the properties of aerogels were mainly influenced by polymer/clay proportion. Polymer molecules play a role of glue linking the clay nanoparticles, improving the structural integrity and hence the mechanical performance of the aerogels. On the other hand, clay platelets serve as a physical barrier that increases the heat endurance. Recycled cellulose fibers (RCF) that were isolated from waste paper pulp were also used to prepare bio-based aerogels. Adding another biopolymer CMC into RCF aerogels, the resultant RCF-CMC composite aerogels showed different microstructures and enhanced mechanical properties. Physical blending and chemical crosslinking were used to tailor the mechanical properties of xanthan gum/clay aerogels and starch/clay aerogels, respectively. Blending agar with xanthan gum in aqueous solution, the resultant aerogels displayed a significant improvement in mechanical properties compared with those containing a single biopolymer. Moreover, they exhibited tunable microstructures and mechanical properties by ch, En esta Tesis se han preparado diversos aerogeles usando polímeros biodegradables como matriz y arcilla como refuerzo, a través de un proceso de fabricación amigable con el medio ambiente. Los polímeros empleados han sido tanto de origen natural (goma árabiga, agar-agar, goma xantana, almidón) o sintéticos como la carboximetilcelulosa (CMC) o el alcohol polivinílico. Los compuestos formados se han caracterizado a través de diferentes técnicas con el objeto de relacionar las morfologías generadas con las propiedades térmicas y mecánicas resultantes. La gran mayoría de los aerogeles polímero/arcilla exhiben una estructura porosa y laminar que se forma a raíz de la liofilización. Sin embargo, se ha apreciado que altas viscosidades en la solución precursora puede romper la arquitectura laminar al retardar el crecimiento de los cristales de hielo (ej. Solución acuosa de 2.5 % peso de agar). La estructura y las propiedades de los aerogeles están asimismo y en general influenciados por la relación polímero/arcilla. En estos sistemas, las moléculas de polímero actúan a manera de pegamento uniendo las partículas de arcilla, incrementando de esa manera notablemente la capacidad mecánica de los aerogeles. Por otro lado la arcilla actúa entre otras formas, como barrera térmica incrementando la resistencia térmica y al fuego de las espumas formadas. Dentro de este trabajo se han empleado fibras de celulosa recicladas de residuos de papel en un intento de preparar bio-aerogeles a partir de material de desecho. La unión de estas fibras con CMC permitió obtener aerogeles con propiedades mejoradas y la posibilidad de emplear estos residuos en un segundo uso. Además del mezclado físico, en algunos casos se ha realizado una reacción de entrecruzamiento para ajustar las propiedades finales, como en el caso de los aerogeles goma xantana/arcilla o almidón/arcilla. La mezcla de agar con goma xantana en solución acuosa resultó en un notable aumento de propiedades con respecto a las composi, Postprint (published version)

Within the next project it is developed a breathing injection mould. Its main purpose is to prod techniques such as MuCell® which suppose a great increase of physical properties regarding other foaming types as well as an important weight and material price reduction. The piece it is going to better foamed polymer investigation. The mould type is discussed and compared between the core pull system and the breathing due its cheaper cost and high quality direct piece production, although lack in terms of size versatility. Then, that mould is exhaustively defined and evaluated with all the mechanizations and thermal treatments need difficulties of properly predict all the timings and costs.

Recycled cellulose fibers (RCF) from waste paper were utilized to prepare bio-based aerogels through an environmentally friendly freeze-drying method. Food thickening agent sodium carboxymethyl cellulose (CMC) served as a matrix in the bio-aerogels. The microstructures and mechanical properties of the aerogels have been studied as a function of RCF/CMC content. Sodium montmorillonite (Na+-MMT) and ammonium polyphosphate (APP) were added to enhance the thermal stability and flame retardancy, which were investigated by thermogravimetric analysis (TGA) and cone calorimetry respectively. It was found that the Na+-MMT significantly improved the fire retardancy of the aerogels and APP played a synergistic effect with it. The initial decomposition temperature increased by 15 degrees C and the peak of heat release rate decreased from 90 to 49.5 kW m(-2) in the presence of 33% clay. Addition of APP further increased the residue amount and reduced the fire growth rate. Fourier transform infrared spectroscopy (FTIR) was used to analyse the char formed after cone calorimeter tests., Peer Reviewed, Postprint (author’s final draft)

Toughened carbon fibre fabric-reinforced composites were obtained by compression moulding of powder prepregs, using a modified cyclic butylene terephthalate (pCBT) matrix and a bi-directional [0°/90°] carbon fibre fabric. Modification of the pCBT matrix was done by adding small amounts of epoxy resin or isocyanates, acting as toughening agents. Homogeneous CBT/epoxy and CBT/isocyanate blends were obtained by melt blending in a lab-scale batch mixer by applying low temperatures and short processing times. Melt blending was stopped before the ring-opening polymerization of CBT could start. This was assured by monitoring the torque of the batch mixer. Modified CBT was then used as matrix for carbon fibre reinforced pCBT composites prepared by a simple powder prepreg method with subsequent in situ polymerization during compression moulding. Physical properties such as composite density, fibre- and void content were not significantly altered by the presence of the toughening agents. Mechanical properties were assessed by short beam interlaminar shear strength and flexural tests. ILSS, flexural strength and failure strain of the chemically modified composites increased up to 50-60% with respect to unmodified pCBT composites. Nevertheless, the flexural moduli slightly decreased due to the toughening effect of the chain extender on the pCBT matrix. Moreover, it was found that thermal properties and stability were not affected by the presence of modifiers., Peer Reviewed, Postprint (published version)

Foamlike aerogel composites based on renewable xanthan gum (XG) and sodium montmorillonite clay (Na+- MMT) have been prepared using an environmentally friendly freeze-drying process. Additionally, the biobased polysaccharide agar was used to improve the properties of XG/clay aerogels. Fourier transform infrared spectroscopy showed molecular interactions between biopolymers and clay in the aerogel composites. A wide range of microstructures and mechanical properties were obtained with a minimal variation in the density by changing the blended ratio of xanthan gum and agar, with particular emphasis on the addition of 2.5% agar to XG/clay aerogels, which significantly enhanced the mechanical properties. Thermogravimetric analysis revealed that clay improved the thermal stability of aerogels; however, the thermal stability of blends of xanthan gum and agar worsened. Flammability was analyzed through cone calorimeter, which suggested xanthan gum/clay aerogels possessed lower flammability than other typical foams. Clay served as a heat and mass transport, which significantly improved the flame retardancy of the base aerogels., Peer Reviewed, Postprint (published version)

Se efectuó el estudio de la presión en la cavidad de un molde de inyección en dos posiciones diferentes respecto al punto de inyección para evaluar los efectos de los parámetros del proceso y la distancia de dicho punto en la morfología celular del material resultante. Con los datos obtenidos es factible definir criterios para la aplicación de este método de espumación microcelular en la fabricación de productos viables con materiales poliméricos aligerados., Peer Reviewed, Postprint (published version)

Cyclic butylene terephthalate (CBT (R)) is an interesting matrix material for the preparation of nanocomposites due to its very low, water-like melt viscosity which favours clay exfoliation. Nevertheless, polymerized CBT (pCBT) is inherently brittle. This paper reports the preparation of isocyanate-toughened nanocomposites made from CBT and organo-modified montmorillonite. The role of the organoclay as reinforcement and the polymeric isocyanate (PMDI) as toughening agent on the properties of pCBT was studied. The organoclay increased the stiffness and strength by up to 20% whereas the PMDI improved the deformation behaviour. However, the PMDI did not affect the degree of clay dispersion or exfoliation and flocculated-intercalated structures were observed. The compatibility between the pCBT matrix and clay was further increased by preparing PMDI-tethered intercalated organoclay. The modified organoclay then exfoliated during ring-opening polymerization and yielded true pCBT/clay nanocomposites. This work demonstrates that reactive chain extension of CBT with a polyfunctional isocyanate is an effective method to obtain toughened pCBT nanocomposites. Moreover, isocyanates can enhance the compatibility between pCBT and nanofiller as well as the degree of exfoliation., Peer Reviewed, Postprint (published version)

El objetivo de esta investigación es estudiar el efecto de las variables del proceso de inyección sobre la adhesión entre un polímero y una tela utilizando la técnica de decoración en el molde. Se usaron fibras textiles y PEBD formándose una unión del tipo adhesivo. Se evaluó el efecto de las condiciones de proceso en la adhesión, aplicando una matriz de diseño de experimentos y se evaluó mediante la técnica de Pelado. Se obtuvo que la variable de mayor influencia en la adhesión es la temperatura de inyección, observándose que al incrementar la misma, la resistencia de la unión adhesiva disminuye., Peer Reviewed, Postprint (published version)

En el mundo del procesamiento, especialmente en el moldeo por inyección, se busca mejorar y avanzar tecnológicamente con la finalidad de cumplir con las exigencias del mercado, el cual demanda procesos más eficientes, ciclos más cortos, mayor productividad y menores costos. La inyección multicomponente (bi-inyección o sobreinyección) es una nueva técnica del proceso de inyección que busca la unión de dos o más materiales diferentes de manera secuencial o simultánea, produciendo así piezas terminadas sin necesidad de realizar ensamblajes posteriores, modificando y/o mejorando sus propiedades finales., Postprint (published version)

The thesis at hand deals with the modification of cyclic butylene terephthalate (CBT) with the aim to improve its final properties. CBT polymerizes in an entropically-driven ring-opening polymerization into polymerized CBT (pCBT), which is typically brittle. To increase the toughness of pCBT, a series of chemical and physical modifications of CBT with toughening agents and nano-reinforcements have been investigated. The role of the used processing routes on the properties of unmodified pCBT has been studied and in all cases a brittle pCBT has been obtained. However, it was found that a small amount of tetrahydrofuran can toughen pCBT. Nevertheless, this toughening mechanism was found to be only temporarily. Reactive chain extension using low molecular weight, bi- or polyfunctional chain extenders such as epoxy resins or isocyanates was particularly effective and showed a remarkable toughening effect on pCBT. The epoxy- and isocyanatemodified pCBT polymers exhibited increased failure strain in tensile tests while modulus and strength were not significantly affected; contrary to other common toughening methods such as blending with other polymers, plasticization or copolymerization with soft segments. Nanocomposites of toughened CBT and nano-reinforcements such as organo-montmorillonite, graphene and polyhedral oligomeric silsesquioxanes (POSS) were prepared and thoroughly analysed. The organoclay nanocomposites showed an intercalated-flocculated structure with high stiffness and strength together with a semi-ductile deformation behaviour. The organoclay was further modified by tethering the chain extender to the clay surfactant which resulted in an intercalated organoclay. This chain extender-grafted organoclay reacted then with pCBT and therefore could be exfoliated and randomly dispersed in the pCBT matrix during polymerization. A similar strategy was followed in the synthesis of pCBT/graphene nanocomposites. However, graphene exfoliation could not be achieved due, La presente tesis trata de la modificación del butilén tereftalato cíclico (CBT) con el propósito de mejorar alguna de sus propiedades finales y expandir sus aplicaciones. En presencia de un catalizador y temperatura, el CBT reacciona y a través de un proceso de apertura de anillo, polimeriza dando lugar al pCBT. Sin embargo, el polímero resultante es intrínsecamente frágil. En este trabajo se han estudiado diversas modificaciones tanto físicas como químicas (procesado, extensores de cadena, nanopartículas) con el objetivo de incrementar la tenacidad del pCBT. En primer término se estudió el efecto que la ruta específica de procesado tiene sobre las propiedades y si bien en todos los casos se obtuvo un material frágil, se ha descubierto también que una pequeña cantidad de tetrahidrofurano puede hacer el pCBT más tenaz aunque sea de manera temporal. El uso de extensores de cadena polifuncionales de bajo peso molecular, como resinas epoxídicas o isocianatos ha resultado ser particularmente efectivo. Así en el pCBT modificado con dichos agentes se obtuvieron notables incrementos de tenacidad sin significativa afectación de otras propiedades como el módulo de Young o la tensión de fluencia, como normalmente ocurre en procesos como la plastificación o la copolimerización. Por otra parte se han preparado y analizado diversos nanocompuestos con CBT modificado añadiendo diferentes nanopartículas como montmorillonita, grafeno o polyhedral oligomeric silsesquioxanes (POSS). Los nanocompuestos formados con arcilla exhibieron unas estructuras intermedias entre intercaladas y floculadas, con alta resistencia y rigidez en tracción y deformación a rotura de tipo semi-dúctil. El posterior injerto de un extensor de cadena en la superficie de la arcilla modificada permitió la reacción con el pCBT durante la polimerización, alcanzándose en este caso estructuras con arcilla exfoliada y dispersada a lo largo de la matriz. La aplicación de esta estrategia con el grafeno no dio lugar a su, Postprint (published version)

In this study, a reactive extrusion-calendering process was used in order to manufacture OMMT-based (2.5 wt.%) PLA-REX sheets with a nominal thickness of 1 mm. During processing, the properties of the melt were stabilized and enhanced by the addition of 0.5 wt.% of a styrene-acrylic multi-functional-epoxide oligomeric reactive agent. Rheological experiments highlighted the creation of a possible continuous chemical bonding from the MMT organo-modifier to the PD,L-LA matrix. As a result, a better intercalated-dispersed morphology of the filler into the polymer matrix was observed by TEM analysis. Finally, OMMT-based PLA-REX samples showed semi-ductile behaviour under uniaxial tensile loading after one week storage at room temperature., Postprint (published version)

Toughened carbon fiber-fabric reinforced polymerized cyclic butylene terephthalate (pCBT) composites were obtained by chemical modification of cyclic butylene terephthalate (CBT) with small amounts of epoxy resin and isocyanates as chain extenders. Homogeneous CBT/epoxy and CBT/isocyanate blends were prepared by melt blending the components in a lab-scale batch mixer at low temperatures and high shear rate. Melt blending was stopped before the ring-opening polymerization of CBT could start. The modified CBT was the starting material for carbon fiber fabric-reinforced pCBT composites (fiber content at about 65 wt%) which were prepared by ring-opening polymerization during compression molding using a simple powder prepreg method. Interlaminar shear strength, flexural strength, and failure strain of the chemically modified composites increased up to 60% with respect to unmodified pCBT composites. Nevertheless, the flexural moduli slightly decreased due to the toughening effect of the chain extender on the pCBT matrix. Drop weight impact tests revealed that the energy absorption of the modified composites was relatively higher as compared to unmodified pCBT composites., Peer Reviewed, Postprint (author’s final draft)

En el presente trabajo se ha aplicado el concepto de Trabajo Esencial de Fractura (EWF) a un copolímero etilenopropileno en bloque (EPBC) espumado, cuyas características morfológicas y mecánicas eran conocidas. Las probetas presentaron una propagación de grieta cuasi-estable, con diferentes porcentajes de propagación inestable, lo que pudo relacionarse con el espesor de piel no espumada. Debido a este comportamiento, se llevó a cabo la separación de los parámetros de fractura en iniciación de grieta y propagación, así como el cálculo de la apertura del frente de grieta en el momento de inicio de propagación. Como trabajos futuros se propone la aplicación de modelos de crecimiento y coalescencia de microvacíos, considerando como microvacíos las propias celdillas de la estructura espumada., Postprint (published version)

This PhD thesis investigated the incorporation of Polyhedral Oligomeric Silsesquioxanes (POSS) in thermoplastic base materials via melt-blending procedures. Particularly, a focus is taken on the enhancement of the thermal resistance through the addition of different types of POSS on two popular engineering plastics known by their low thermal stability, one being a semi-crystalline copolymer i.e. polyoxymethylene (POM) and the other an amorphous copolymer i.e. acrylonitrile butadiene styrene grafted with maleic anhydride (ABS-g-Ma). Different nanocomposites have been produced, from which its morphology, miscibility, structure, thermal properties and appearance behaviour before and during the thermoxidative degradation is herein quantified and discussed together with the resulting benefits and drawbacks. All the nanocomposites have been produced via melt-blending, using the nanofillers Glycidyl, Glycidyl-Isobutyl, Aminopropyl-isobutyl and Poly(ethylene-glycol) for the POM matrix, and Amino-Propyl Isobutyl, Glycidyl, and Trisilanol for the ABS-g-Ma matrix. The incorporation adequacy of the nanofillers into the matrix has been pre-assessed with the Hoy¿s solubility calculation method and later on corroborated with scanning electron microscopy (SEM) and differential scanning calorimetry (DSC). The quantification of the thermal degradation behaviour of each sample at different temperatures and exposure times was carried out through Fourier transform infrared spectrography (FTIR), thermogravimetric analysis (TGA) including the degradation kinetics and, ultimately, the sample appearance progress has been assessed in terms of yellowing by means of colour spectrophotometry (Cielab). The results showed that the presence of different POSS's used with the POM matrix improves dramatically the thermal stability of the base material and that such improvement is proportionate to the solubility compatibility between matrix and the nanofiller. The best performance was found with Amino, Los avances producidos en años recientes en el campo de la nanotecnología y sus aplicaciones en los materiales están aportando grandes mejoras en el rendimiento de los mismos en áreas como la resistencia mecánica, estabilidad térmica, propiedades ópticas y eléctricas, entre otras. Por otro lado, el mundo de la ingeniería y el diseño de componentes plásticos está llevando los materiales cada vez más a su límite, con el fin de poder ofrecer el máximo rendimiento al mínimo coste. Esta realidad implica la necesidad creciente de customizar estructuras poliméricas con propiedades mejoradas en áreas específicas para cada aplicación. A pesar de los desarrollos que se han estado produciendo últimamente en nanocompuestos termoplásticos, el conocimiento en este campo es aún limitado, y requiere de más iniciativas de investigación y desarrollo sobre el amplio campo de posibilidades que nos ofrecen los nanocompuestos. El objetivo de esta tesis es contribuir en el conocimiento de los nanocompuestos a través del estudio de los efectos de varias nanocargas del tipo Polyhedral Oligomeric Silsesquioxanes (POSS) en el comportamiento de la resistencia térmica del copolímero semicristalino polióxido de metileno (POM) y del terpolímero amorfo acrilonitrilo‐butadieno‐estireno (ABS), los cuales son dos plásticos técnicos susceptibles a la termoxidación. Diferentes nanocompuestos se han elaborado con el fin de estudiar su morfología, miscibilidad, estructura, propiedades térmicas y apariencia, así como los beneficios y contrapartidas que resultan de ellos. Los nano‐compuestos han sido elaborados mediante el método de mezcla en estado fundido (melt‐blending), utilizando cuatro nano‐cargas distintas para el POM, siendo Glicidil, Glicidil‐Isobutil, Aminopropil‐isobutil y Poli(etilen‐glicol), y tres nano‐cargas para el ABS, siendo Amino‐Propil Isobutil, Glicidil y Trisilanol La compatibilidad teórica de las nano‐cargas se ha calculado mediante el método de solubilidad de “Hoy”, y se ha corrobor, Els avenços produïts en els últims anys tant en el camp de la nanotecnología com en les seves aplicacions en els materials, està contribuint en la millora del rendiment dels mateixos en àeras com la resistència mecànica, l’estabilitat tèrmica, i les propietats òptiques i elèctriques entre d’altres. Per altra banda, el món de l’enginyería i el disseny de components plàstics està portant els materials cada vegada més al seu límit amb la finalitat de poder oferir el màxim rendiment al mínim cost, i això comporta una necessitat creixent de customitzar les estructura polimèriques amb propietats especificament millorades en àreas molt concretes en funció de l’aplicació requerida. A pesar del desenvolupament que s’ha estat produint últimament en l’àrea de nanocompostos plàstics, el coneixement en aquest camp és encara limitat, i requereix de més iniciatives d’investigació per cobrir el potencial que ofereix aquesta classe de materials, així com conèixer també les seves limitacions. L’objectiu d’aquesta tesi es el de contribuïr en l’enteniment dels nanocompostos plàstics a través de l’estudi dels efectes de vàries nanocàrregues del tipus Polyhedral Oligomeric Silsesquioxanes (POSS) en el comportament de la resistència tèrmica del poli(òxid de metilè) (POM) com a material semicristalí, i l’acrilonitril‐butadiè‐estirè (ABS) com a material amorf. Val a dir que la selecció d’aquests dos polímers tècnics ha estat en part motivada per la seva susceptibilitat inherent a la termodegradació. Diferents nanocompostos basats amb aquests materials s’han elaborat amb la finalitat d’estudiar la seva morfología, miscibilitat, estructura, propietats tèrmiques i aparença, així com els beneficis i contrapartides que resulten d’ells. La preparació dels nanocompostos ha sigut mitjançant el mètode de barreja en estat fos (melt‐blending), util.litzant quatre nano‐càrregues diferentes per el POM, siguent glicidil, glicidil‐Isobutil, aminopropil‐isobutil y poli(etilenè‐glicol), i tres nano‐càrregue, Postprint (published version)

Postprint (published version)

El objetivo de esta investigación fue estudiar el efecto de las variables del proceso de sobre inyección sobre la resistencia de la unión adhesiva rígido–rígido entre un par de materiales poliméricos. Se emplearon como materiales el estireno –acrilonitrilo (SAN) y el acrilonitrilo–butadieno –estireno (ABS). Se evaluó el efecto de las condiciones de proceso (Psostenida, vinyección , Tfundido)del material sobreinyectado en la adhesión mediante ensayos mecánicos de tracción, trabajo esencial de fractura interfacial empleando geometría DENT, además de mecánica de la fractura interfacial elástico –lineal. Se obtuvo un incremento de la resistencia de unión adhesiva al aumentar la temperatura de fundido y la rugosidad de la superficie de contacto del sustrato con el material sobreinyectado., Peer Reviewed, Postprint (published version)

La presente publicación comprende el estudio del efecto de las variables de proceso de inyección sobre la morfología obtenida al espumar Polientilentereftalato glicolizado (PETG) con un agente espumante químico endotérmico. La morfología fue estudiada mediante Microscopía Electrónica de Barrido (SEM). Se pudo observar que a medida que la relación gas/polímero se incrementa, la densidad celular de la espuma de PETG aumenta. A medida que la velocidad de inyección se incrementa, la densidad celular aumenta hasta llegar a un comportamiento asintótico. Por último, se encontró que el factor que genera un mayor efecto es la temperatura del molde, la cual al ser incrementada, genera un aumento de la densidad celular y disminución del diámetro celular., Postprint (published version)

El objetivo de esta investigación es estudiar el efecto de las variables del proceso de inyección sobre la adhesión entre un material polimérico y una tela utilizando la técnica de decoración en el molde (IMD). Se usaron fibras textiles y PEBD formándose una unión del tipo adhesivo. Se evaluó el efecto de las condiciones de proceso (Ps, vi, Ti) en la adhesión, aplicando una matriz de diseño de experimentos (DOE) y se evaluó mecánicamente mediante la técnica de Pelado. Se obtuvo que la variable de mayor influencia en la adhesión es la temperatura de inyección, observándose que al incrementar la misma, la resistencia de la unión adhesiva disminuye., Peer Reviewed, Postprint (published version)

Los aerogeles son una clase de materiales que se caracteriza por su extrema ligereza y alto contenido de aire. En este trabajo se han preparado diferentes aerogeles polímero/arcilla (PVOH/Na+-MMT) mediante un proceso simple de congelación y liofilización. Mediante esta técnica se han preparado aerogeles modificados conteniendo diferentes agentes ignifugantes en forma de partículas. La adición de dichos agentes causó un ligero incremento de la densidad aparente. Las propiedades mecánicas en compresión tanto a baja como a alta velocidad en general se vieron ligeramente reducidas debido a una menor unión entre el polímero y la arcilla. La excepción fue la muestra modificada con Al(OH)3 que incrementó la rigidez de los compuestos y la tensión a máxima deformación. En cuanto a las propiedades térmicas, la presencia de polifosfato de amonio (APP) o de silica gel (SG) redujo notablemente la velocidad de descomposición de los aerogeles en el rango de temperaturas entre 250ºC y 650ºC, sin embargo, la temperatura de inicio de descomposición no se vio sensiblemente alterada. El comportamiento a fuego se analizó mediante calorimetría de cono y los resultados han indicado que tanto la presencia de Al(OH)3 como de APP retardan la combustión del sistema y reducen la tasa de liberación de calor., Postprint (published version)

Microcellular injection-molding technology is capable of producing lightweight polymeric products. The foam morphology is determined by the injection-molding parameters, and it has been observed that depending on the parameter variations, the cell structure may exhibit substantial morphological differences through the entire section along the melt flow direction of the injected part. The effects of varying injection-molding parameters on foam morphology and thermal mechanical properties of a multiphase ethylene-propylene block copolymer (EPBC) were tested on 5-mm plaque specimens using a constant temperature profile. It has been found that injection speed does not have a significant effect on the thermal-mechanical properties of the foam, whereas shot volume and mold temperature do have a significant influence. Low shot volume produces uniform density cellular structures and larger cores, whereas lower mold temperatures help maintain small cell sizes. Furthermore, the effect of the copolymer’s crystalline phase on foam morphology has been observed. This study identifies the achievable foam morphologies and the thermal-mechanical performance of cellular molded EPBC parts., Postprint (published version)

Electronic version of an article published as "Express polymer letters" vol. 7, nº. 2, February 2013, p. 172-185. , Cyclic butylene terephthalate oligomers (CBT) were reacted in a ring-opening polymerization with three types of isocyanates: a bifunctional aromatic type, a bifunctional aliphatic type and a polymeric aromatic isocyanate. All reactions took place in a batch mixer. The use of 0.5 to 1 wt% isocyanate led to a dramatic increase in elongation at break of polymerized cyclic butylene terephthalate (pCBT), from 8 to above 100%. The stiffness and strength of the modified pCBT, however, were found to slightly decrease. Proton nuclear magnetic resonance (NMR) analysis shows that the formation of thermally stable amide groups is the dominant chain extension reaction mechanism. Gel content measurements suggest a linear structure for samples containing bifunctional isocyanates while pCBT modified with polyfunctional isocyanate exhibited some gel formation at higher isocyanate content. Melting and crystallization temperatures as well as degree of crystallinity were found to decrease with increasing isocyanate content. No phase separation was detected by scanning electron microscopy (SEM) analysis. Moreover, a high degree of polymerization is deduced due to the absence of CBT oligomer crystals., Peer Reviewed, Postprint (published version)

The influence of the functionalisation of fully or partially condensed POSS cages on the properties of engineering thermoplastic-based nanocomposites is studied. POSS with different organic substituents were selected in accordance with the structure and chemical composition of the host polymer and melt mixed with the corresponding matrix. In general, good dispersion at the nanoscale level was achieved upon the addition of some functionalised POSS, leading to a remarkable increase on the thermal decomposition temperature under nitrogen atmosphere. However, for the polymers having high decomposition temperatures, there were no significant changes on the thermal properties of the nanocomposites. On the other hand, the dispersion of the POSS, whatever its functionalisation was, led to the presence of micron-sized aggregates. The relationships among these effects and the morphological characteristics of the systems were analysed., Peer Reviewed, Postprint (published version)

Aerogel is a class of material characterized by its high void content and extreme lightness. Different polymer/clay aerogels have been prepared by a simply freeze–thaw process from a suspension with poly(vinyl alcohol) (PVOH) and clay (Na+-MMT). Low density polymer/clay aerogels modified with flame retardant agents were prepared using a similar approach. The addition of flame retardant agents slightly increased the apparent density of the final composites whereas the compression properties were reduced due to the decrease in the polymer/clay interfacial bonding. An exception was the sample containing Al(OH)3 that exhibited higher modulus and stress at maximum deformation. Regarding thermal properties, the presence of ammonium polyphosphate (APP) or silica gel (SG) significantly slowed the rate of aerogel decomposition at the temperature range from 250 °C to 500 °C while the onset of polymer decomposition was not affected. Fire behavior was analyzed through cone calorimeter suggesting that either the presence of Al(OH)3 or APP reduced the heat release rate of PVOH/clay systems., Peer Reviewed, Postprint (published version)

Microcellular injection moulding is capable of producing lightweight polymeric products. The present study analyses the influence of several representative injection moulding parameters on the foam’s morphology, apparent density and thermo-mechanical properties of PETG, poly(ethylene terephthalate-co-1,4-cyclohexylene-dimethylene terephthalate) specimens. A strong variation of the cell morphology along the melt flow direction has been found, as well as a dependence on the shot volume. The most homogeneous microcellular structure is achieved when low shot volume, intermediate injection speed and low mould temperature are employed. The skin–core structure of the injected parts, determined the thermo-mechanical features of the specimen, which are ruled by the skin layer., Peer Reviewed, Postprint (published version)

Peer Reviewed, Postprint (published version)

Thermo oxidative degradation at and beyond process- ing temperatures has been carried out on ABS copoly- mer grafted with Maleic Anhydride (ABS- g -Ma) and three nanocomposites with the above material melt-blended with different types of POSS, being amino-propyl isobutyl (APOSS), glycidyl (GPOSS), and trisilanol (TPOSS). The incorporation adequacy of the nanofillers into the matrix has been assessed with scanning electron microscopy (SEM) and differential scanning calorimetry (DSC), whereas the quantification of the thermal degradation behavior of each sample was carried out through infrared spectrography (FTIR), thermogravimetric analysis (TGA) including the degra- dation kinetics and color spectrophotometry (Cielab). Although the results show adequate incorporation and miscibility of the nanofillers into the matrix, the GPOSS and the TPOSS nanocomposites provided no relevant improvements in thermal stability when compared with the base ABS- g -Ma, and the APOSS blend exhibits a very slight decay in almost all the quantitative analysis carried out in this work., Peer Reviewed, Postprint (published version)

A series of polysulfone/phenyl trisilanol POSS nanocomposites were produced by melt blending by twin screw batch mixing. These materials were then injec- tion molded, and their thermal, mechanical, and morpho- logical properties were tested. The tensile properties of polysulfone were moderately compromised by the addition of phenyl TPOSS, because of the formation of large ( 1 l m) voided POSS aggregates. These domains however did cause the improvement of the impact resistance of the composites as described by the mechanism of crack pinning and bow- ing. Flexural properties remained essentially unchanged, which is attributed to the formation of an aggregate free- skin layer, which formed in the injection molded parts. Thermal behavior of the composites also remained largely unchanged due to the lack of POSS-polymer interactions on the molecular/chain segment scale. Initially, it was hypothesized that a high degree of POSS-polymer interac- tions would be present in these composited based on exami- nation of their chemical structures. This however, was not the case as phase separation was clearly present. This work highlights the need for a better understanding of the predic- tion of POSS-polymer interaction., Peer Reviewed, Postprint (published version)

Low flammability, foam-like materials based on bio-based, renewable ammonium alginate and sodium montmorillonite clay were fabricated through a simple, environmentally-friendly freeze-drying process in which water is used as solvent. These materials exhibit mechanical properties similar to those of rigid PU foams or balsa; the compressive modulus (1–97 MPa) and density (0.047–0.174 g/cm3) increase with increasing solids content, with an associated change from a layered to network microstructure structure. Calcium ions, either added directly or indirectly via CaCO3/gluconolactone (GDL) are an effective crosslinking agent for alginate, with the GDL route providing the greatest enhancement of mechanical properties. The thermal stability of the aerogels is also enhanced by the presence of crosslinking. The alginate/clay aerogels possess inherently low flammability, as measured by cone calorimetry, with heat release values decreasing as the proportion of clay in the composites is increased., Peer Reviewed, Postprint (published version)