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Las ficciones audiovisuales seriadas que circulan por los diversos medios, tanto canales como plataformas, participan a través de ciertas estrategias textuales, narrativas y discursivas, en conjunción con sus audiencias en la construcción de sentido sobre la historia y el pasado. Se busca ahondar en la implementación de dichas estrategias en la serie de ficción audiovisual Narcos México (2018) ofertada en la plataforma de contenidos audiovisuales bajo demanda Netflix, mismas que inciden en un apuntalamiento ideológico de una versión del pasado. Para ello se observaron en el plano de lo textual, la dimensión de la expresión y del contenido, así como la conjunción de elementos que conforman lo narrativo, lo retórico y lo estético para explicar las implicaciones en la memoria colectiva sobre el pasado que la serie de ficción audiovisual pretende representar

Lignin-capped silver nanoparticles were incorporated in situ into polyurethane foams during their polymerization to obtain multifunctional materials suitable for chronic wound dressing. Lignin with increased phenolic content, achieved through the enzymatic grafting of natural phenolic compounds, played the dual role of a silver reducing agent in the synthesis of the lignin-capped silver nanoparticles and as a nanoformulated polyol additive in the polyurethane composition able to react with isocyanate. The nanoparticles-embedded polyurethane foams showed over 4 and 5 logs bacterial growth reduction against the Gram-positive S. aureus and the Gram-negative P. aeruginosa, respectively, attributed to both the direct contact- and release-killing mechanisms. The swelling properties of the foams, related to their capacity to remove the excess of wound exudates containing deleterious oxidative species and enzymes, varied from 585 to 1145 % as a function of the content of nanoparticles. Overall, the physicomechanical and antibacterial properties of the foams, together with their biocompatibility and sustained release of silver, make these multifunctional materials suitable candidates for chronic wound dressings.

El presente trabajo propone reconstruccion de la poetica estetica del filme El demonio neon (2016), empleando un analisis hermeneutico de las relaciones que se establecen entre, las referencias hipotextuales a las tradiciones judeocristianas y el mito de Narciso articuladas en el discurso audiovisual y la exposicion dialectica de la consecucion de lo bello a traves de diversos medios como deber y fin ultimo del ser humano.

This work presents the experimental results of the mechanical and fracture behaviour of three polymeric blends prepared from two recycled plastics, namely polypropylene and opaque poly (ethylene terephthalate), where the second one acted as a reinforcement phase. The raw materials were two commercial degrees of recycled post-consumer waste, i.e., rPP and rPET-O. Sheets were manufactured by a semi-industrial extrusion-calendering process. The mechanical and fracture behaviours of manufactured sheets were analyzed via tensile tests and the essential work of fracture approach. SEM micrographics of cryofractured sheets revelated the development of in situ rPP/rPET-O microfibrillar composites when 30 wt.% of rPET-O was added. It was observed that the yield stress was not affected with the addition of rPET-O. However, the microfibrillar structure increased the Young’s modulus by more than a third compared with rPP, fulfilling the longitudinal value predicted by the additive rule of mixtures. Regarding the EWF analysis, the resistance to crack initiation was highly influenced by the resistance to its propagation owing to morphology-related instabilities during tearing. To analyze the initiation stage, a partition energy method was successfully applied by splitting the total work of fracture into two specific energetic contributions, namely initiation and propagation. The results revelated that the specific essential initiation-related work of fracture was mainly affected by rPET-O phase. Remarkably, its value was significantly improved by a factor of three with the microfibrillar structure of rPET-O phase. The results allowed the exploration of the potential ability of manufacturing in situ MFCs without a “precursor” morphology, providing an economical way to promote the recycling rate of PET-O, as this material is being discarded from current recycling processes.

This work provides an experimental analysis regarding the fracture behavior of recycled opaque PET (rPET-O) containing titanium dioxide (TiO2) under plane stress conditions. For this purpose, a commercially post-consumer transparent colored/opaque PET flakes mix was processed using a semi-industrial extrusion calendering process. The manufactured rPET-O sheets had a TiO2 content of 1.45 wt.%. The mechanical and fracture properties of unaged and physically aged (1 year) samples were determined through uniaxial tensile experiments and the Essential Work of Fracture (EWF) methodology, respectively, and were compared to those of recycled transparent PET (rPET-T). Under tensile loading, independently of the aging time, rPET-O samples exhibited similar mechanical behavior as rPET-T up to the yield point. The main differences remained in the post-yielding region. The presence of TiO2 particles allowed reducing the strain energy density up to neck formation in aged samples. Regarding the EWF analysis, it is argued that the energy consumed up to the onset of crack propagation (we) for rPET-T was mainly dependent of the molecular mobility. That is, the we value decreased by 26% when rPET-T was physically aged. Interestingly, we values remained independent of the aging time for rPET-O. In fact, it was highlighted that before crack propagation, the EWF response was principally governed by matrix cavitation ahead of the crack tip, which allowed a significant release of the triaxial stress state independently of the molecular mobility. This property enabled rPET-O to exhibit a resistance to crack initiation 17% higher as compared to rPET-T when the material was physically aged. Finally, independently of the aging time, rPET-O exhibited a resistance to crack growth approximately 21% larger than rPET-T due to matrix fibrillation in large scale deformation.

Adding textures to surfaces is known to improve the external appearance of injection moulded components. However, when high surface quality is required, normally a paint coating is applied on top of the moulded textured surface. In this work, an alternative to painting for obtaining high quality surfaces is proposed, following an environmental-friendly process and having low production cost. Three different surface textures obtained by injection moulding have been characterized and compared with a painted one. Alternative topographical parameters such as the absolute functional height (AFH), the functional height distribution (FHD), texture slope (TS) or texture aperture angle (TAA) besides to the traditional roughness parameters such as the arithmetical mean height (Sa) and the root mean square height (Sq) have been utilized to characterize the random surface textures. The relationships between these parameters and the surface quality appearance represented by gloss and reflectivity contrast have been established using a new total appearance measurement (TAM) apparatus. It was found that by applying secondary operation on the textured mould cavity, such as adding micro roughness features or coatings, equal apparent quality to the ones obtained by painting can be reached.

Poly(lactic) acid, (PLA) is a biodegradable polymer that has attracted interest as a potential substitute for some thermoplastic polymers. However, its advanced brittleness at room temperature represents one of the major drawbacks for its general use. In this work, PLA was modified by reactive extrusion (PLAREx) to enhance the rheological behavior and to limit its degradation. The modified material was melt blended with ABS, analyzing the resultant morphology, rheological, thermo-mechanical and fracture behavior. Since PLA does not have reasonable compatibility with ABS, maleic anhydride-grafted ABS (ABS-g-Ma) was used as compatibilizer. The morphology of the PLAREx/ABS samples resulted in the formation of small ABS rods in the matrix. The presence of maleic anhydride contributed to reduce the interfacial energy of the blends and to obtain finer micro-domains of the ABS-rich phase in the PLAREx matrix. In the compatibilized blends, the presence of elongated ABS-rich phases opposed the free crack propagation and contributed to the increase in the fracture energy in comparison to neat PLA.

PLA bio-blends with a predominantly biosourced PA10.10 in the composition range 10-50wt.% were prepared by melt blending in order to overcome the advanced brittleness of PLA. Due to the inherent immiscibility of the blends, 30 wt.% of PA was needed to achieve a brittle-to-ductile transition and a co-continuous morphology was predicted at 58 wt.% of PA. The initial enhancement of the PLA rheological behaviour through the environmentally friendly reactive extrusion process yielded a finer and more homogeneous microstructure and hence enhanced the mechanical properties of the bio-blends at much lower PA contents. The brittle-to-ductile transition could be achieved with only 10 wt.% and co-continuity was observed already at 44 wt.% of PA. Results indicate the significant potential of modifying PLA flow behaviour as a promising green manufacturing method toward expanding PLA-based bio-blends applications.

Square plates (nominal thickness: 3 mm, nominal width: 100 mm) of different rheologically modified PLA/ABS blends were manufactured through injection molding, with or without adding ABS grafted with maleic anhydride (MAH). 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). PLA-REX was obtained by reactive extrusion of PLA. A general analytical equation was used in order to evaluate the kinetic parameters of the thermal degradation of PLA−REX/ABS and PLA−REX/ABS/ABS−g−MAH blends through thermogravimetric analysis. The thermal degradation of these blends occurred through two different reaction steps. Various empirical and theoretical solid-state mechanisms were tested to elucidate the best kinetic model. In order to reach this goal, plots of standardized conversion functions were 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 was determined to quantitatively identify the best mechanism. By doing that, it has been possible to determine the right activation energy of the thermal degradation. It has been demonstrated that the best mechanisms for these materials were R2 (i.e. phase-boundary-controlled reaction (contracting area)) for the first step (α 70%). The thermal stability of PLA−REX/ABS blend was greatly improved by adding the ABS−g−MAH compatibilizer. These findings were also confirmed by means of morphological characterization through scanning electron microscopy.

Reducing the weight of petrol-derived plastics is a common way to decrease the environmental impact of several products. Another option consists in using biopolymers instead. However, most of the times, the complete substitution is not possible and partial replacement, usually obtained by blending, appears as a solution. The foaming of these blends combines both strategies and constitutes a further step to reduce the amount of petrol-derived plastics. In this study, PLA/ABS blends were prepared by melt blending without using any type of compatibilizer and were foamed by batch using super critical carbon dioxide as foaming agent. The final morphology of the blends was studied by SEM as a function of pressure and process temperature. Results shows that PLA/ABS blends can be successfully foamed under different conditions to obtain better structures than those known for pure components.

Foaming is a powerful method that allows lightening of products and reducing the amount of material used. Poly(lactic) acid (PLA) is considered a promising thermoplastic for the replacement of traditional non-biodegradable polymers. In this study, PLA was modified with an epoxide chain extender via reactive extrusion and blended with Acrylonitrile – Butadiene – Styrene (ABS) in the presence of a compatibilizer. The MuCell® process was applied to obtain foams from the previous prepared blends. Results shows that the presence of the epoxide and ABS inhibit the degradation during processing making foaming possible. Under flexural conditions where foamed are designed to work, the mechanical properties of the foamed blends were very similar to the solid counterparts.

The effect of processing conditions on the final morphology of Poly(Lactic Acid) (PLA) with bio-based Polyamide 10.10 (PA) 70/30 blends is analyzed in this paper. Two types of PLA were used: Commercial (neat PLA) and a rheologically modified PLA (PLAREx), with higher melt elasticity produced by reactive extrusion. To evaluate the ability of in situ micro-fibrillation (f) of PA phase during blend compounding by twin-screw extrusion, two processing parameters were varied: i) Screw speed rotation (rpm), and ii) take-up velocity, to induce a hot stretching with different Draw Ratios (DR). The potential ability of PA-f in both bio-blends was evaluated by the viscosity (p) and elasticity (k&rsquo, ) ratios determined from the rheological tests of pristine polymers. When PLAREx was used, the requirements for PA-f was fulfilled in the shear rate range observed at the extrusion die. Scanning electron microscopy (SEM) observations revealed that, unlike neat PLA, PLAREx promoted PA-f without hot stretching and the aspect ratio increased as DR increased. For neat PLA-based blends, PA-f was promoted during the hot stretching stage. DMTA analysis revealed that the use of PLAREx PLAREx resulted in a better mechanical performance in the rubbery region (T &gt, Tg PLA-phase) due to the PA-f morphology obtained.

Low-flammability freeze-dried cellulose nanofibril (CNF)/sodium montmorillonite (MMT) aerogels with improved mechanical properties were fabricated via a facile cross-linking of boric acid (BA) and melamine-formaldehyde (MF) resins. Scanning electron microscopy analysis showed that BA cross-linking reduced the interspacing of layered CNF/MMT aerogels whereas introduction of MF formed polymeric fibrils that connected the layers. These changes on microstructures resulted in the improvement on compressive mechanical properties of the cross-linked aerogels. Moreover, the boron (B)/nitrogen (N) containing flame retardant cross-linkers greatly increased the limiting oxygen index values that could reach 85% and leveled the UL-94 rating from no rating to V-0. Cone calorimetric results suggested that BA and MF induced a synergistic effect on the flame retardant properties of the CNF/MMT aerogels. However, the thermal conductivity was little affected because pore structure and size was not substantially modified. This simple approach fabricated highly flame-resistant and mechanically strong CNF-based aerogels that could be used in various engineering fields

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 this work, the relations between the replication quality of random, coarse textured, surfaces with the injection-moulding process has been analysed through 3D areal characterisation techniques. The multi-scale surface approach has been applied to effectively separate the main surface components, roughness, waviness and form. Amplitude, functional, hybrid and spatial parameters, as well as alternative surface characteristics such as the number of micro-cavities (NG), grain area ( G A ¯ ) and grain volume ( G V ) , ¯ were used as a way to determine the influence of the manufacturing process on the replication quality of the mould texture, either at the macro- or micro-scale. A model to quantify the effect of the injection-moulding parameters on surface texture replication has been obtained through a 24 factorial design of experiments. It was found that the holding pressure was the main parameter to enhance the mould texture replication, followed by the melt and mould temperatures. The injection volumetric flow rate did not have a significant effect on the texture replication ratio. The surface analysis, at the human eye resolution, only allows the detection of macro-defects such as form deviation. On the other hand, the surface characterisation at the micro-scale allows the detection of roughness differences, up to 30% on average, as a function of the injection conditions.

In this research, the influence of the macro- and micro-topography on randomly micro-textured polypropylene surfaces has been studied. An initial characterization of the underlying surface was carried out using three-dimensional (3D) technologies such as chromatic and white light confocal microscopy. A multi-scale analysis methodology was employed for analysing the surface at either macro- or micro-scales. Among others, topographic characteristics such as peak-to-valley symmetry and the amount of micro-asperities were analysed to quantitatively determine the scratch and mar visibility resistance. The results show that surfaces with higher symmetry in their functional height distributions yield lower lightness variation (¿L*) between the scratch pattern and its residual background height (RBH). This allows for a better suitability in hiding the scratch damage. On the other hand, topographies with less amount of micro-asperities on top of the texture provided a better mar resistance. In these cases, deformation mechanisms such as ironing are minimized, resulting in a lower gloss variation and lower contrast between the damaged area and its surroundings.

A series of low density, highly porous clay/poly(vinyl alcohol) composite aerogels, incorporating ammonium alginate, were fabricated via a convenient and eco-friendly freeze drying method. It is significant to understand rheological properties of precursor gels because they directly affect the form of aerogels and their processing behaviors. The introduction of ammonium alginate impacted the rheological properties of colloidal gels and improved the mechanical performance of the subject aerogels. The specific compositions and processing conditions applied to those colloidal gel systems brought about different aerogel morphologies, which in turn translated into the observed mechanical properties. The bridge between gel rheologies and aerogel structures are established in the present work.

Low density composites of sodium montmorillonite and poly(amide-imide) polymers have been created using an ice templating method, which serves as an alternative to the often-difficult foaming of high temperature/high performance polymers. The starting polymer was received in the poly(amic acid) form which can be cured using heat, into a water insoluble amide-imide copolymer. The resulting materials have densities in the 0.05 g/cm3 range and have excellent mechanical properties. Using a tertiary amine as a processing aid provides for lower viscosity and allows more concentrated polymer solutions to be used. The concentration of the amine relative to the acid groups on the polymer backbone has been found to cause significant difference in the mechanical properties of the dried materials. The synthesis and characterization of low density versions of two poly(amide-imide) polymers and their composites with sodium montmorillonite clay are discussed in the present work.

In this work, microcellular ABS foams were studied. A series of injection molding samples defined by a design of experiments was carried out to analyze the effect of shot volume, mold temperature, and injection velocity on the morphology, mechanical properties, and surface roughness of microcellular samples. A predominant influence of shot volume on the cell structure and tensile properties was evidenced. Higher cell densities and narrower cell size distributions were obtained at lower injection volume. However, elastic modulus and tensile strength were improved by increasing the shot size. The effect of mold temperature and injection velocity was secondary. Higher levels of mold temperature and injection rate provided finer cell morphologies, but their effects on the elastic modulus and tensile strength were negligible. The decrease in shot volume and increase in gas content led to poor surface quality, whereas it was greatly improved by raising both mold temperature and injection velocity

Some of the main properties of polysaccharide and protein-based aerogels are discussed in this chapter. The fundamentals of thermal conductivity governing the insulation properties of these materials are presented and related to the aerogel microstructure. In particular, obtaining aerogels with evenly distributed nanometric pore sizes is crucial to decreasing the thermal conductivity and to achieve super-insulation materials. Secondly, an insight into the different approaches that can be used to impart electrical conductivity or magnetic properties of bio-based aerogels is highlighted. Apart from the addition of different conductive fillers traditionally used as a second phase, the synthesis with conductive polymers and the conversion of the aerogel structure in a conductive carbon-based path enables the formation of aerogels with a wide range of electrical properties. Finally, this chapter focuses on the fire behavior of polysaccharide and protein aerogels. The basic carbohydrate structure presents a serious challenge when trying to prevent fast combustion, especially in aerogels formed from polysaccharides. However, the development of hybrid organic–inorganic systems using graphene, silicon, clay or their combination with intrinsically flame-retardant materials, such as alginates, are powerful tools in the design of aerogels with low flammability and potential industrial applications.

A facile cross-linking strategy to construct flame retardant cellulose nanofibril (CNF)/sodium montmorillonite (MMT) aerogels with improved mechanical properties, by incorporating melamine-formaldehyde (MF) resins into precursor suspensions followed by a freeze-drying process, is reported in this work. Scanning electron microscopy images indicate that MF cross-linking does not significantly change the microstructures of CNF and CNF/MMT aerogels. However, the cross-linking improves the materials’ mechanical and flame properties. By incorporating 50 wt% of MF, the compression moduli and compressive stress of CNF aerogels increase by 316% and 114%, respectively. The limiting oxygen index (LOI) value of CNF aerogels also increases from 17.1% to 23.4%. Further addition of MMT increases the CNF aerogels’ LOI value to 57% and increases the maximum decomposition temperature by nearly 20 °C. This occurs because MMT and MF induce a synergistic effect which improves the flame retardant properties of the CNFs aerogels. In CNF/MMT composite aerogels, the introduction of 34 wt% of MF leads to a 54.6% reduction of the peak of heat release rate and a 53.2% decrease in total heat release. CNF aerogels made from sustainable feedstocks with excellent mechanical properties and high flame retardancy, like those discussed herein, show promise as fire resistant biofoams

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.

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 w e , 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, J o . 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 detail.

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

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 (α < 60%) took place through an R2 mechanism whereas the second step (α > 75%) did it according an F3 mechanism. Moreover, y(α) master plots have also been used in order to confirm that the selected reaction mechanisms were adequate The Ministry of Economy and Competitiveness projects MAT2013-40730-P and MAT2016-80045-R (AEI/FEDER, UE) of the Spanish Government financially supported this work

Carbon fiber reinforced cyclic butylene terephthalate composites have been processed by vacuum infusion under two different non-isothermal processing routes starting from a one-component cyclic butylene terephthalate resin system. One of them was processed under a short cycle with fast cooling, and another one was processed under a long cycle with slow cooling. Both the micro-structure and low-energy impact properties of the composites have been investigated. On one hand, the fast cooling generates randomly dispersed voids and porosities in the resin-rich regions during the crystallization-induced shrinkage. On the other hand, the slow cooling generates a highly crystalline and brittle matrix without porosity. However, many micro-cracks appear in the resin-rich regions due to the combination of the brittleness and longitudinal shrinkage of the matrix. The critical delamination energy of the slow cooled composite is slightly higher than that of the fast cooled one, whereas this latter absorbs over 25% more energy before being penetrated, as well as performing in a less brittle way. The lower interlaminar shear strength of the fast cooled composite is suggested to be the origin of its higher energy absorbing capability and less brittle behavior.

The rejected fraction of plastics from different sorting plants has been studied in terms of composition, processability and enhancement potential. This waste stream consists of a coarse range of plastics families, polyethylene constituting the most abundant one. Blends with two recycled polyethylenes in different proportions were analyzed. The results showed that the mixed fraction was easy to process although it showed a brittle behavior. The addition of recycled polyethylene caused limited ductility improvements, although acceptable levels were achieved in certain mixing ratios. This work demonstrates that mixed plastic wastes can be transformed into a useful material.

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.

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.

Both inorganic and polymeric aerogels are well-known in the materials field. Inorganic aerogels are generally susceptible to brittle fracture, while polymeric aerogels tend to exhibit low modului and high flammability. To overcome these disadvantages, we introduce a new approach to the design of aerogels. A microporous poly(vinyl alcohol) (PVA) aerogel/silica nanocomposite was prepared by growing a silica conformal coating onto a PVA aerogel scaffold. Such aerogel/silica nanocomposites show significant improvement in their mechanical properties over either individual component. The nanocomposites show excellent fire resistance since the silica conformal coating serves as a barrier for heat transfer and mass loss of the coated organic materials. After a fluorocarbon silane treatment, the nanocomposites also show durable superhydrophobicity.

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.

Cyclic butylene terephthalate (CBT) was polymerized in the presence of a low molecular weight bifunctional epoxy resin. The resultant chain extended polymerized CBT (pCBT) showed an increased ductility compared to that of conventionally polymerized pCBT for all analyzed epoxy concentrations (1–4 wt.%). The best results were obtained with 2 wt.% of epoxy resin. Other mechanical properties remained relatively unaffected by the epoxy resin. 1 H NMR analysis suggested an esterification reaction of the carboxyl end groups of pCBT and the glycidyl functional groups of the diepoxide. With increasing epoxy content, the chain extended pCBT showed an increasing molecular weight and a decreasing glass transition. Crystallization and melting temperatures as well as crystallinity also decreased with increasing epoxy concentration.

Thermooxidative degradation at and beyond processing temperatures has been carried out on polyoxymethylene (POM) enhanced with four different types of POSS, being Glycidyl, GlycidylIsobutyl, Aminopropylisobutyl, and Poly(ethylene glycol). The quantification of such degradation was carried out through FTIR spectrography, color spectrophotometry, and thermogravimetric analysis methods. The results showed that the presence of POSS in the blend improves dramatically the thermal stability of the POM matrix. The best performance was found with Aminopropylisobutyl, whereby the onset of degradation temperature increased by more than 50°C. Said improvement is referred to the conditions where the nanocomposite developed only 2% of carbonyl yield and 8% of yellowing of the 100% deterioration suffered by the standard POM copolymer.

In this study, the morphology and thermo-mechanical behavior of composites formed by a polyoxymethylene (POM) matrix and monosilanolisobutyl polyhedral oligomeric silsesquioxane (msib-POSS) filler have been studied. The msib- POSS molecules were added to the POM by direct melt blending at loadings between 0 and 10 wt.%. Hydrogen bonding interactions were detected between POM and msib-POSS Si–OH groups, increasing their mutual compatibility and leading to nanometer-size dispersion of some msib-POSS molecules. These interactions do not prevent POSS aggregation during blending, but lead to micron-scale msib-POSS domains. The thermal decomposition temperature of the composites remained practically constant under inert and oxidative conditions. The low temperature thermal transition (g) and glass transition temperature (Tg) of POM were found to move to higher temperatures only when 2.5 wt.% of msib-POSS was added, indicating that POSS is physically linked to the POM chains, restricting their motion under those conditions. Low content (2.5 wt.%) of msib-POSS results in antiplastization, whereas higher levels of POSS lead to a decrease in the storage modulus of the polymer. The relationships among these effects and the morphological characteristics of the systems will be discussed herein

The influence of the functionalization of fully condensed POSS cages on the properties of POMbased nanocomposites is studied. POSS with different organic substituents [glycidylethyl, aminopropylisobutyl, and poly(ethylene glycol)] are taken into account and melt mixed with POM. Good dispersion was achieved upon the addition of amino functionalized POSS, leading to an increase on the thermal decomposition temperature under nitrogen atmosphere up to 50 8C. However, mm-size aggregates were observed for other nanocomposites. There is no significant change in other thermal properties of the nanocomposites. The relationships among these effects and the morphological characteristics of the systems were analyzed.

Ethylene–(vinyl alcohol) (EVOH)/organo-modified montmorillonite clay (OMMT) composites were prepared using commercial OMMTs with two different organo-modifiers. The first one has polar groups, which interact with EVOH chains, whereas the second one is non-polar. Composites with a high weight percentage of OMMT were prepared by melt-extrusion in a twin-screw extruder. Films were prepared in a cast-film line in order to evaluate the tensile and fracture parameters. The morphology of the EVOH/OMMT composites was characterized using wide-angle X-ray scattering and transmission electron microscopy, complemented by image analysis. The mechanical properties were evaluated using uniaxial tensile tests; the fracture behaviour was analysed using the essential work of fracture (EWF) method. Results show differences in composite morphologies and crystalline fraction, depending on the content and the nature of the organo-modifier. The mechanical and fracture behaviours are strongly influenced by those parameters, which act in opposite senses. The EWF method is shown to be a useful tool for the analysis of the structure–properties relationships of these composites. Copyright © 2010 Society of Chemical Industry

Hybrid nanocomposites formed with polyoxymethylene copolymer (POM) and different types of polyhedral oligomeric silsesquioxane (POSS) nanoparticles have been investigated. Four types of POSS have been studied in contents of 2.5% and 5% wt. The POSS were incorporated by direct melt-mixing. Traditionally copolymerization has been the preferred approach used to form polymer-POSS nanocomposites because the possibility of immiscibility with the polymer matrix is reduced. However, melt-blended POSS nanoparticles can also improve the thermo-mechanical properties of some polymers. Different morphologies were obtained depending on the type of POSS used. GI-POSS and O-POSS exhibit sub-micron or micron-sized inclusions which size increased with increasing percentages of POSS added. On the other hand, both G-POSS and T-POSS appeared to be uniformly dispersed in the POM matrix probably at a molecular level. This is a clear indication of miscibility between these systems and also that POSS solubility in POM is higher than 5 wt%. G-POSS improved the thermal stability of the systems. However, the melting temperature and the modulus of elasticity were found to slightly decrease. On the other hand, the O-POSS produced the opposite effect in the matrix. Finally T-POSS filled systems do not yield important variations in regard to polymethylene oxide properties although interaction between T-POSS and the matrix was detected.

The strength of adhesion between two over-moulded polymers, methylmethacrylate–butadiene–styrene copolymer (MABS) and thermoplastic polyurethane (TPU) that constitute a bi-component laminar system has been the subject of study. Results showed that at the bi-layer interface the adhesive fracture toughness increases as temperature and surface roughness are increased. Roughness has been demonstrated to be the most important parameter defining adhesion strength and failure. With the increase of roughness the failure was observed to change from adhesive towards cohesive type. An increase in either the temperature or the pressure applied to the samples caused a rise in adhesion energy. However, pressure seemed to have a minor effect in comparison to temperature. Significant increments in adhesion were obtained after applying the corona discharge treatment (CDT) to the attaching surfaces resulting in adhesion strengths almost double those of non-treated systems.

BACKGROUND: Ethylene–(vinyl alcohol) (EVOH) copolymer/organo-modified montmorillonite (OMMT) composites were investigated. Composites with two different percentages by weight of OMMT were prepared using a melt-extrusion procedure in a twin-screw extruder, using EVOH as matrix. Films made of EVOH and EVOH/OMMT composites were prepared in a cast-film extrusion line. RESULTS: The mechanical properties were evaluated by tensile tests and the fracture behaviour was analysed using the essential-work-of-fracture (EWF) method. Fracture characterization was carried out for the two main processing directions: melt flow direction and transverse direction. Fractographic observations were made using scanning electron microscopy. CONCLUSION: The tensile test results indicated good compatibility between EVOH and OMMT. In addition, the fracture tests showed the influence of the clay particle arrangement on the fracture behaviour, showing an increase in the specific essential work of fracture, we, which was attributed to the EVOH–OMMT interaction. The plastic term, βwp, showed different trends depending on the test direction, explained by the size of the plastic zone and the restrictions to the EVOH plastic flow promoted by the clay particles. In this sense, the EWF method is shown to be a very useful tool for the analysis of structure–property relationships in polymer–organo-clay composites. Copyright © 2009 Society of Chemical Industry

Thermooxidative degradation at and beyond processing temperatures of a polyoxymethylene copolymer has been progressively accelerated to carbonisation through oven-storage aging. The quantification of such degradation was carried out through FTIR spectrography and colour spectrophotometry methods. The state of thermo-oxidation was monitored through the FTIR spectra corresponding to the carbonyl aldehyde group (O=CH) and methylene bending (–CH2), as well as the chromaticity changes experienced on the sample surface. The results showed that the FTIR bands suggested are a reliable indicator during the initial conditions of degradation, however, the spectrophotometry becomes more appropriate method for more aggressive conditions leading to carbonisation.

In this work, the morphology and thermo-mechanical behaviour of nanocomposites formed by a polycarbonate (PC) matrix and polyhedral oligomeric silsesquioxane with phenethyl substituents (Ph-POSS) have been studied. The Ph-POSS nanocages were added to the PC by direct melt blending at loadings between 0% and 15 wt%. Good dispersion was achieved up to 5 wt% of nanofiller. At higher loadings micron-sized aggregates were observed in the nanocomposites by scanning and transmission electron microscopy. Increasing of Ph-POSS content lead to phase separation, agglomeration and low values on the final properties. The DSC and DMA analyses showed that increasing the amount of nanocages caused a continuous decrease on the composite’s Tg. Although little increments on the polycarbonate decomposition temperature were found, the presence of Ph-POSS did not improve significantly the thermal stability. Under nitrogen atmosphere the degradation mechanism of PC was not affected by the POSS. The residual weights obtained under oxygen atmosphere were in agreement with the theoretical weights of the Ph-POSS added. With respect to the nanocomposites mechanical properties the most remarkable trend was an improvement on the composite’s yield stress having the maximum at 5 wt% of nanofiller. Higher amounts of Ph-POSS lead to a decrease on the yield stress, finding even lower values than the one corresponding to the neat matrix. This behaviour has been attributed to the presence of large POSS agglomerates with low adhesion to the polymer matrix. A continuous decrease on the strain at break was also observed, reflecting the brittle character of the formed composites.

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.

In the present work, poly(lactic acid) (PLA) sheets reinforced with organically modified montmorillonite (o-MMT) were manufactured through reactive extrusion-calendering using a masterbatch approach in a pilot plant. Reaction monitoring analysis suggests the occurrence of premature reactions between o-MMT and the reactive agent; lowering further structural changes in the polymeric matrix. While calendered sheets exhibited a homogenous and preferential distribution of clay particles in MD, the coexistence of mixed structures, involving tactoids of various sizes as well as intercalated clay layers was observed. However, a higher and finer dispersion of o-MMT particles was achieved through clay–polymer tethering via chain extender molecules. Under tensile loading, the aforementioned clay dispersion enhanced multiple cavitation processes, notably improving PLA shear flow.

The cure process of a composite formed by a trifunctional epoxy resin filled with glass beads has been analyzed using Fourier transform infrared spectroscopy (FTIR). With this technique it was possible to follow the curing reactions, studying and quantifying the conversion of different representative functional groups. The evolution of concentration of primary and secondary amines as well as epoxide groups has been followed as a function of the applied curing process. The primary amines were found to be the most useful band in the monitoring process due to the absence of overlapping. The introduction of the rigid phase had a remarkable influence on the curing process, especially when the glass beads where treated with a silane coupling agent. In this latter case the rate of amine conversion was faster than that observed in the unfilled matrix or for the untreated glass-filled composite. However, the filler treatment with a coupling agent was revealed to be inefficient in terms of mechanical properties, probably due to the high temperatures involved during the epoxy curing process. The mechanical properties like Young’s modulus and composite stress at break where found to largely increase and hold its original value, respectively, on the contrary, the strain at break decreased at a value near 50% of the neat matrix. The mechanical composite properties were also evaluated in terms of the stress intensity factor ( K I ) and the energy release rate ( G I ). Both values achieved a maximum around the 20%v of glass-beads and were found to decrease slightly with higher volumes of filler. Scanning electron microscopy (SEM) was carried out in order to assess the toughening mechanism associated with the presence of glass beads.

In this work, the properties of microcellular ABS were studied. Foamed samples exhibited a solid skin/foamed core struc- ture, with some elongated cells in the flow direction, while spherical cells were mostly observed in the transversal direction. The flex- ural modulus, flexural strength, and fracture toughness K Ic decreased with the density. However, the crack tip opening displacement (CTOD) was found to increase with the foaming ratio. The evolution of the mechanical properties and fracture toughness was well described by prediction models considering the skin/core morphology of these microcellular materials. Foaming increased the aniso- tropic behavior of the material, due to the cell elongation caused by the fountain flow during injection

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.