Computer Simulation of Three-Phase Equilibria for Some Water/n-Alkane Binary Systems.

In this work, the vapor-liquid-liquid equilibrium (VLLE) of the water/n-pentane, water/n-hexane, water/n-octane, and water/n-decane binary systems is calculated by computer simulation using the NVT-Gibbs ensemble (in the version of three simulation boxes) combined with the configurational bias Monte Carlo method. The combination of both methods, the molecular potential models used, and the simulation details allowed us to calculate the triphasic equilibrium properties of the systems studied: the densities of the three phases in equilibrium, their compositions, and potential energies. In previous works, these simulations were not carried out at a temperature range nor water/n-alkanes systems simulated in this work, probably because they are highly nonideal systems; so, to the best of our knowledge, this is the first time that this phenomenon is studied in detail. The results from VLLE simulations of the water/n-pentane system for temperatures from 343.2 to 435 K, the water/n-hexane system for temperatures from 373.11 to 473.15 K, the water/n-octane system for temperatures from 310.9 to 500 K, and for the water/n-decane system for temperatures from 374.15 to 525 K are reported here. The temperature range was selected in concordance with the experimental data available for an adequate study of the VLLE simulation results. The subcritical densities (vapor and liquid rich in n-alkane phases) at various temperatures fit well with the scaling law and the law of rectilinear diameters, allowing the estimation of upper critical end point temperature and density of the VLLE. The simulation results show a good prediction with experimental data reports in the literature.

Foaming of 3D-Printed PLA/CaCO3 Composites by Supercritical CO2 Process for Sustainable Food Contact Materials.

In the last decade, among the emerging technologies in the area of bioplastics, additive manufacturing (AM), commonly referred to as 3D printing, stands out. This technology has gained great interest in the development of new products, mainly due to its capability to easily produce customized and low-cost plastic products. This work aims to evaluate the effect of supercritical foaming of 3D-printed parts based on a commercial PLA matrix loaded with calcium carbonate, for single-use sustainable food contact materials. 3D-printed PLA/CaCO3 parts were obtained by 3D printing with a 20% and 80% infill, and two infill patterns, rectilinear and triangular, were set for each of the infill percentages selected. Supercritical fluid foaming of PLA/CaCO3 composite printed parts was performed using a pressure of 25 MPa, a temperature of 130 °C for 23 min, with a fast depressurization rate (1 s). Closed-cell foams were achieved and the presence of CaCO3 did not influence the surface of the foams or the cell walls, and no agglomerations were observed. Foam samples with 80% infill showed subtle temperature fluctuations, and thermogravimetric analysis showed that samples were thermally stable up to ~300 °C, while the maximum degradation temperature was around 365 °C. Finally, tensile test analysis showed that for lower infill contents, the foams showed lower mechanical performance, while the 80% infill and triangular pattern produced foams with good mechanical performance. These results emphasize the interest in using the supercritical CO2 process to easily produce foams from 3D-printed parts. These materials represent a sustainable alternative for replacing non-biodegradable materials such as Expanded Polystyrene, and they are a promising option for use in many industrial applications, such as contact materials.

Biodegradable nanocomposite poly(lactic acid) foams containing carvacrol-based cocrystal prepared by supercritical CO2 processing for controlled release in active food packaging.

Compounds derived from essential oils have been used in active packaging, but their volatility and degradability negatively affect stability and leads to high release rates. The present study aimed to develop PLA bionanocomposite foams loaded with carvacrol cocrystal by supercritical CO2 and its release into a food simulant for control release in food packaging. For this purpose, 4,4'-bipyridine was used as coformer and carvacrol as active agent. Cocrystallized closed cell foams were obtained using supercritical CO2 and were characterized in terms of their physicochemical and mechanical properties, and release kinetics to a D1 simulant were evaluated as well as the antioxidant ability. A better overall mechanical behavior due to the nanoclay promoting a higher interfacial adhesion with the polymeric matrix was revealed. A higher incorporation of carvacrol was observed in samples with higher C30B content. The incorporated cocrystals showed a decrease of one order of magnitude in the estimated effective diffusion coefficient of carvacrol and showed antioxidant activity. These results suggest that the nanocomposite foam containing carvacrol-based cocrystals could be used in active packaging systems with controlled release characteristics, especially with highly volatile compounds, and can be proposed for other fields such as biomedical applications.

Plasticized Mechanical Recycled PLA Films Reinforced with Microbial Cellulose Particles Obtained from Kombucha Fermented in Yerba Mate Waste.

In this study, yerba mate waste (YMW) was used to produce a kombucha beverage, and the obtained microbial cellulose produced as a byproduct (KMW) was used to reinforce a mechanically recycled poly(lactic acid) (r-PLA) matrix. Microbial cellulosic particles were also produced in pristine yerba mate for comparison (KMN). To simulate the revalorization of the industrial PLA products rejected during the production line, PLA was subjected to three extrusion cycles, and the resultant pellets (r3-PLA) were then plasticized with 15 wt.% of acetyl tributyl citrate ester (ATBC) to obtain optically transparent and flexible films by the solvent casting method. The plasticized r3-PLA-ATBC matrix was then loaded with KMW and KMN in 1 and 3 wt.%. The use of plasticizer allowed a good dispersion of microbial cellulose particles into the r3-PLA matrix, allowing us to obtain flexible and transparent films which showed good structural and mechanical performance. Additionally, the obtained films showed antioxidant properties, as was proven by release analyses conducted in direct contact with a fatty food simulant. The results suggest the potential interest of these recycled and biobased materials, which are obtained from the revalorization of food waste, for their industrial application in food packaging and agricultural films.

Processing Compostable PLA/Organoclay Bionanocomposite Foams by Supercritical CO2 Foaming for Sustainable Food Packaging.

This article proposes a foaming method using supercritical carbon dioxide (scCO2) to obtain compostable bionanocomposite foams based on PLA and organoclay (C30B) where this bionanocomposite was fabricated by a previous hot melt extrusion step. Neat PLA films and PLA/C30B films (1, 2, and 3 wt.%) were obtained by using a melt extrusion process followed by a film forming process obtaining films with thicknesses between 500 and 600 µm. Films were further processed into foams in a high-pressure cell with scCO2 under constant conditions of pressure (25 MPa) and temperature (130 °C) for 30 min. Bionanocomposite PLA foams evidenced a closed cell and uniform cell structure; however, neat PLA presented a poor cell structure and thick cell walls. The thermal stability was significantly enhanced in the bionanocomposite foam samples by the good dispersion of nanoclays due to scCO2, as demonstrated by X-ray diffraction analysis. The bionanocomposite foams showed improved overall mechanical performance due to well-dispersed nanoclays promoting increased interfacial adhesion with the polymeric matrix. The water uptake behavior of bionanocomposite foams showed that they practically did not absorb water during the first week of immersion in water. Finally, PLA foams were disintegrated under standard composting conditions at higher rates than PLA films, showing their sustainable character. Thus, PLA bionanocomposite foams obtained by batch supercritical foaming seem to be a sustainable option to replace non-biodegradable expanded polystyrene, and they represent a promising alternative to be considered in applications such as food packaging and other products.

Manejo quirúrgico del empiema mediante Decorticación Pleural en pacientes del Hospital de Clínicas por el Departamento de Cirugía de Tórax (2016-2019) / Surgical management of empyema through Pleural Decortication in patients of the Clínica´s hospital by the Department of Thoracic Surgery (2016-2019)

El empiema es una colección de líquido purulento en el espacio pleural. La causa más común es la neumonía. Las opciones de tratamiento incluyen toracocentesis terapéutica, colocación de catéter de drenaje, terapia fibrinolítica, pleurodesis y cirugía, como la decorticación pleural. El drenaje pleural es eficaz en la etapa I y la cirugía está reservada para casos complicados (estadios II y III). En estos casos, es necesaria la decorticación pulmonar. Actualmente, el enfoque más favorecido para la decorticación es mediante una toracotomía abierta. Este es un estudio observacional, descriptivo, de corte transversal, retrospectivo, con un muestreo no probabilístico de casos consecutivos que tuvo como población accesible a pacientes con el diagnostico de empiema en quienes se realizó una decorticación pleural en el Hospital de Clínicas por el Departamento de Cirugía de Tórax durante el periodo de marzo 2016 a febrero 2019. Un total de 24 pacientes con el diagnóstico de empiema fueron sometidos a una decorticación pleural. La etiología de empiema más frecuente (75%) fue el derrame paraneumónico. Las complicaciones post quirúrgicas estuvieron presentes en 9 (37,5%) pacientes, de estos, 4 (17%) presentaron fuga aérea durante los primeros días postoperatorios. Se constató la resolución completa del cuadro en 21 (87,5%) pacientes y 3 (12,5%) pacientes presentaron colección residual pleural. Se constató recurrencia en 1 (4%) paciente, requiriendo un re intervención quirúrgica. En conclusión, la casuística de nuestro departamento de tórax coincide en cuanto a valores internacionales de complicaciones, resolución y mortalidad.

Empyema is a collection of purulent fluid in the pleural space. The most common cause is pneumonia. Treatment options include therapeutic thoracentesis, drainage catheter placement, fibrinolytic therapy, pleurodesis, and surgery, such as pleural decortication. Pleural drainage is effective in stage I and surgery is reserved for complicated cases (stages II and III). In these cases, pulmonary decortication is necessary. Currently, the most favored approach to decortication is by open thoracotomy. This is an observational, descriptive, cross-sectional, retrospective study, with a non-probabilistic sampling of consecutive cases that had as the accessible population, patients with the diagnosis of empyema in whom pleural decortication was performed at the Clinica´s Hospital of San Lorenzo, by the Department of Thoracic Surgery during the period from March 2016 to February 2019. A total of 24 patients with the diagnosis of empyema underwent pleural decortication. The most frequent aetiology of empyema (75%) was parapneumonic effusion. Post-surgical complications were present in 9 (37.5%) patients, of these, 4 (17%) presented air leakage during the first postoperative days. Complete resolution of the condition was verified in 21 (87.5%) patients and 3 (12.5%) patients presented residual pleural collection. Recurrence was found in 1 (4%) patient, requiring reoperation. In conclusion, the casuistry of our thoracic department coincides in terms of international values of complications, resolution and mortality.

Evaluation of Different Compatibilization Strategies to Improve the Performance of Injection-Molded Green Composite Pieces Made of Polylactide Reinforced with Short Flaxseed Fibers.

Green composites made of polylactide (PLA) and short flaxseed fibers (FFs) at 20 wt % were successfully compounded by twin-screw extrusion (TSE) and subsequently shaped into pieces by injection molding. The linen waste derived FFs were subjected to an alkalization pretreatment to remove impurities, improve the fiber surface quality, and make the fibers more hydrophobic. The alkali-pretreated FFs successfully reinforced PLA, leading to green composite pieces with higher mechanical strength. However, the pieces also showed lower ductility and toughness and the lignocellulosic fibers easily detached during fracture due to the absence or low interfacial adhesion with the biopolyester matrix. Therefore, four different compatibilization strategies were carried out to enhance the fiber-matrix interfacial adhesion. These routes consisted on the silanization of the alkalized FFs with a glycidyl silane, namely (3-glycidyloxypropyl) trimethoxysilane (GPTMS), and the reactive extrusion (REX) with three compatibilizers, namely a multi-functional epoxy-based styrene-acrylic oligomer (ESAO), a random copolymer of poly(styrene-co-glycidyl methacrylate) (PS-co-GMA), and maleinized linseed oil (MLO). The results showed that all the here-tested compatibilizers improved mechanical strength, ductility, and toughness as well as the thermal stability and thermomechanical properties of the green composite pieces. The highest interfacial adhesion was observed in the green composite pieces containing the silanized fibers. Interestingly, PS-co-GMA and, more intensely, ESAO yielded the pieces with the highest mechanical performance due to the higher reactivity of these additives with both composite components and their chain-extension action, whereas MLO led to the most ductile pieces due to its secondary role as plasticizer for PLA.

Study of the Influence of the Reprocessing Cycles on the Final Properties of Polylactide Pieces Obtained by Injection Molding.

This research work aims to study the influence of the reprocessing cycles on the mechanical, thermal, and thermomechanical properties of polylactide (PLA). To this end, PLA was subjected to as many as six extrusion cycles and the resultant pellets were shaped into pieces by injection molding. Mechanical characterization revealed that the PLA pieces presented relatively similar properties up to the third reprocessing cycle, whereas further cycles induced an intense reduction in ductility and toughness. The effect of the reprocessing cycles was also studied by the changes in the melt fluidity, which showed a significant increase after four reprocessing cycles. An increase in the bio-polyester chain mobility was also attained with the number of the reprocessing cycles that subsequently favored an increase in crystallinity of PLA. A visual inspection indicated that PLA developed certain yellowing and the pieces also became less transparent with the increasing number of reprocessing cycles. Therefore, the obtained results showed that PLA suffers a slight degradation after one or two reprocessing cycles whereas performance impairment becomes more evident above the fourth reprocessing cycle. This finding suggests that the mechanical recycling of PLA for up to three cycles of extrusion and subsequent injection molding is technically feasible.

Optimization of the Loading of an Environmentally Friendly Compatibilizer Derived from Linseed Oil in Poly(Lactic Acid)/Diatomaceous Earth Composites.

Maleinized linseed oil (MLO) has been successfully used as biobased compatibilizer in polyester blends. Its efficiency as compatibilizer in polymer composites with organic and inorganic fillers, compared to other traditional fillers, has also been proved. The goal of this work is to optimize the amount of MLO on poly(lactic acid)/diatomaceous earth (PLA/DE) composites to open new potential to these materials in the active packaging industry without compromising the environmental efficiency of these composites. The amount of DE remains constant at 10 wt% and MLO varies from 1 to 15 phr (weight parts of MLO per 100 g of PLA/DE composite). The effect of MLO on mechanical, thermal, thermomechanical and morphological properties is described in this work. The obtained results show a clear embrittlement of the uncompatibilized PLA/DE composites, which is progressively reduced by the addition of MLO. MLO shows good miscibility at low concentrations (lower than 5 phr) while above 5 phr, a clear phase separation phenomenon can be detected, with the formation of rounded microvoids and shapes which have a positive effect on impact strength.

Estenosis esofágica benigna / Benign esophageal stricture

La estenosis esofágica benigna puede ser complicación demúltiples patologías. Reportamos el caso de un adolescente, de16 años de edad, con disfagia y pérdida de peso, con internaciónprevia por neumonía adquirida en la comunidad complicadacon derrame pleural, en asistencia respiratoria mecánica, consonda nasogástrica y sonda transpilórica para alimentación enteral.Se diagnostica estenosis esofágica benigna por endoscopíadigestiva alta. Se realiza manejo conservador con dilatacionescon bujías de Savary, con buena evolución clínica.