Optimization of screw extrusion-based additive manufacturing process for direct extrusion of polyketone

La policetona alifática (PK) es una clase relativamente nueva de polímero semicristalino, conocida por sus propiedades químicas, térmicas y mecánicas mejoradas, así como por su respeto al medio ambiente. Estos atributos lo convierten en un candidato prometedor para reemplazar varios otros polímeros. Sin embargo, la producción de este polímero plantea un desafío debido a su limitada estabilidad térmica. Esta tesis se centra en evaluar la viabilidad de producir piezas estables mediante fabricación aditiva basada en extrusión de tornillo para dos tipos de polecetonas alifáticas. Las policetonas utilizadas en este estudio son PK6246 (policetona base) y PK8655 (policetona reforzada con fibra de vidrio). Se empleó una metodología experimental y una caracterización detallada. Inicialmente, se realizaron pruebas preliminares para determinar y limitar parámetros como el rango de velocidad de la mesa, las dimensiones de la pieza de trabajo y las temperaturas de extrusión. Las dimensiones de la pieza de trabajo se definieron en función de las limitaciones de la mesa de impresión, mientras que el rango de velocidad de la mesa y las temperaturas de extrusión se determinaron según las recomendaciones del proveedor. Posteriormente se imprimieron 30 piezas de cada tipo de policetona. Los resultados revelaron que se pueden producir piezas estables de PK6246 mediante fabricación aditiva basada en extrusora, cuando se eligen los parámetros de impresión correctos. Por el contrario, las piezas fabricadas con PK8655 mostraron un rendimiento deficiente. Las muestras PK6246 demostraron que las resistencias a la tracción entre capas (ángulo de impresión de 90°) pueden alcanzar valores de hasta 42 MPa, un valor razonablemente confiable considerando un ángulo de impresión de 90° y cercano a los 60 MPa especificados por el proveedor. Sin embargo, las muestras de PK8655 apenas excedieron los 30 MPa, significativamente más bajo que el valor especificado por el proveedor de 130 MPa. Además, la microestructura de las muestras de PK8655 mostró una porosidad significativamente mayor en comparación con cualquier muestra de PK6246. Además, la temperatura entre capas jugó un papel crucial en la determinación de los parámetros de impresión óptimos. Esto afecta la resistencia a la tracción y está influenciado por la velocidad de enfriamiento entre las capas, que a su vez depende de la velocidad de la mesa y la geometría de la capa. Una temperatura entre capas alta puede hacer que la pieza se hunda debido a la acumulación de calor, mientras que una temperatura entre capas baja puede provocar deformaciones, especialmente en las capas iniciales de la impresión.Aliphatic polyketone (PK) is a relatively new class of semicrystalline polymer, known for its enhanced chemical, thermal, and mechanical properties, as well as its environmental friendliness. These attributes make it a promising candidate to replace several other polymers. However, the production of this polymer is challenging by its limited thermal stability. This thesis focuses on assessing the feasibility of producing stable parts through screw extrusion-based additive manufacturing for two types of aliphatic polyketones. The polyketones used in this study are PK6246 (base polyketone) and PK8655 (glass fiberreinforced polyketone). An experimental methodology and detailed characterization were employed. Initially, preliminary tests were conducted to determine and constrain parameters such as table speed range, workpiece dimensions, and extrusion temperatures. The workpiece dimensions were defined based on printing table limitations, while the table speed range and extrusion temperatures were determined according to supplier recommendations. Subsequently, 30 pieces of each type of polyketone were printed. The results revealed that stable parts of PK6246 can be produced through extruder-based additive manufacturing, when the correct printing parameters are chosen. In contrast, parts made from PK8655 exhibited poor performance. PK6246 samples demonstrated inter-road tensile strengths (raster angle 90°) can reach values up to 42 MPa, a reasonably reliable value considering a raster angle of 90° and close to the 60 MPa specified by the supplier. However, PK8655 samples barely exceeded 30 MPa, significantly lower than the supplierspecified value of 130 MPa. Additionally, the microstructure of the PK8655 samples showed significantly higher porosity compared to any PK6246 sample. Furthermore, the interpass temperature played a crucial role in determining the optimal printing parameters. This affects tensile strength and is influenced by the cooling rate between strands, which in turn depends on the table speed and strand geometry. A high interpass temperature can cause the piece to sink due to heat accumulation, while a low interpass temperature can lead to warping, especially on the initial strands of printing.Aliphatische Polyketone (PK) ist eine relativ neue Klasse teilkristalliner Polymere, die für ihre verbesserten chemischen, thermischen und mechanischen Eigenschaften sowie ihre Umweltfreundlichkeit bekannt sind. Diese Eigenschaften machen sie zu einem vielversprechenden Kandidaten für den Ersatz mehrerer anderer Polymere. Die Herstellung dieses Polymers ist jedoch aufgrund seiner begrenzten thermischen Stabilität eine Herausforderung. Der Schwerpunkt dieser Arbeit liegt auf der Bewertung der Machbarkeit der Herstellung stabiler Teile durch additive Fertigung auf Basis der Schneckenextrusion für zwei Arten aliphatischer Polyketone. Die in dieser Studie verwendeten Polyketone sind PK6246 (Basispolyketon) und PK8655 (glasfaserverstärktes Polyketon). Es wurden eine experimentelle Methodik und eine detaillierte Charakterisierung verwendet. Zunächst wurden Vorversuche durchgeführt, um Parameter wie Plattformgeschwindigkeitsbereich, Werkstückabmessungen und Extrusionstemperaturen zu bestimmen und einzuschränken. Die Abmessungen der Werkstücke wurden auf der Grundlage der Einschränkungen der Druckplattform definiert, während der Geschwindigkeitsbereich der Plattform und die Extrusionstemperaturen auf der Grundlage der Empfehlungen des Lieferanten bestimmt wurden. Anschließend wurden 30 Stück jedes Polyketontyps gedruckt. Die Ergebnisse zeigten, dass sich durch Extruder basierte additive Fertigung stabile Teile aus PK6246 herstellen lassen, wenn die richtigen Druckparameter gewählt werden. Im Gegensatz dazu zeigten Teile aus PK8655 eine schlechte Leistung. PK6246-Proben wiesen eine Zugfestigkeit zwischen den Schichten (Rasterwinkel 90°) auf, die Werte von bis zu 42 MPa erreichen kann, ein einigermaßen zuverlässiger Wert in Anbetracht eines Rasterwinkels von 90° und nahe an den vom Lieferanten angegebenen 60 MPa. PK8655-Proben überstiegen jedoch kaum 30 MPa und lag damit deutlich unter dem vom Lieferanten angegebenen Wert von 130 MPa. Darüber hinaus zeigte die Mikrostruktur der PK8655- Proben eine deutlich höhere Porosität als jede PK6246-Probe. Darüber hinaus spielte die Zwischenlagentemperatur eine entscheidende Rolle bei der Bestimmung der optimalen Druckparameter. Diese wirkt sich auf die Zugfestigkeit aus und wird von der Abkühlrate zwischen den Strängen beeinflusst, die wiederum von der Plattformgeschwindigkeit und der Stranggeometrie abhängt. Eine hohe Zwischenlagentemperatur kann dazu führen, dass das Teil aufgrund von Hitzestau absinkt, während eine niedrige Zwischenlagentemperatur insbesondere bei den ersten Druckschichten zu Verformungen führen kann

RELACIÓN ENTRE LA ESTABILIDAD MUSCULAR LUMBOPÉLVICA Y LA VELOCIDAD DEL BALÓN EN EL DISPARO DE JUGADORES DE FÚTBOL ASOCIACIÓN.

En el futbol asociación uno de los elementos más importantes es el disparo. En el disparo de balón se requiere la transmisión de fuerzas generadas en la musculatura lumbopélvica, a través del tronco, tren inferior y finalmente al balón. La interrupción en esta cadena cinética se asocia a una disminución de la velocidad de disparo del balón y mayor riesgo de lesiones. Se realizó un estudio no experimental, transversal, de tipo correlacional el objetivo fue determinar la relación entre la estabilidad muscular lumbopélvica y la velocidad del balón en el disparo de jugadores de futbol. Se incluyeron 21 futbolistas varoniles sub-15. La relación se estableció entre las variables de estabilidad muscular lumbopélvica y velocidad de balón mediante el protocolo de McGuill que es una herramienta que mide la duración de ejercicios isométricos que implican la musculatura lumbopélvica y la cuantificación de velocidades de disparo mediante un radar deportivo.UAEM, el autor

Metodología para el dimensionamiento de un molino de martillo

El presente documento comprende el desarrollo de una metodología para el dimensionamiento de un molino de martillos, las cuales tienen un potencial energético importante que debe ser aprovechada. Por un lado, se realiza una caracterización de los residuos agrícolas cañeros (RAC) con la finalidad de conocer las principales características del material a procesar. Por otro lado, se realiza el estado de arte de los principales equipos de molienda, principalmente, del molino de martillos; esto con la finalidad de conocer las ventajas y desventajas de cada tipo de molino y así compararlos con el molino de martillos. Asimismo, se analiza las principales tecnologías de los molinos martillos en la actualidad en base a investigaciones bibliográficas que exponen una comparación entre los molinos de martillos tradicionales con los de nueva tecnología, así como un estudio de materiales a triturar. Estas nuevas tecnologías incluyen información reciente y se aplica en el diseño de un molino de martillos. Finalmente, se desarrolla diagramas de flujo de la secuencia de cálculo para el dimensionamiento de los principales componentes mecánicos del molino de martillos, así como la propuesta para la metodología de ensayo para determinar las fuerzas de impacto sobre las hojas y con ello dimensionar los martillos del molino. Los principales componentes de un molino de martillos son: los martillos, disco porta-martillos, eje principal, perno de sujeción, disco de separación, carcaza del molino, motor eléctrico y la rejilla de filtro; sin embargo, en el presente documento se abarca solamente la metodología para el dimensionamiento de algunos componentes tales como los martillos, discos porta-martillos, perno de sujeción y eje principal debido a que estos son la base del principio de funcionamiento de un molino de martillos.Trabajo de investigació

An invariant based transversely-isotropic constitutive model for unidirectional fibre reinforced composites considering the matrix viscous effects

Fibres Reinforced Polymers (FRPs) are found in several applications in aeronautics, space and in the automotive industry. These applications are exposed to loading conditions, including impact, which results in a complex mechanical response that is vital to accurately predict. This is particularly important for a new generation of thermoplastic-based composites. The model proposed in this work is an invariant-based approach to represent viscous effects in polymer composites. The model developed only requires two viscous parameters to calibrate the viscoelastic behaviour. A good correlation between the simulations and experimental data obtained in off- axis tests in tension and compression is obtained.Postprint (author's final draft

Interplay of early-life nutritional programming on obesity, inflammation and epigenetic outcomes

The huge health burden accompanying obesity is not only attributable to inadequate dietary and sedentary lifestyle habits, since a predisposing genetic make-up and other putative determinants concerning easier weight gain and fat deposition have been reported. Thus, several investigations aiming to understand energy metabolism and body composition maintenance have been performed considering the participation of perinatal nutritional programming and epigenetic processes as well as inflammation phenomena. The Developmental Origins of Health and Disease hypothesis and inheritance-oriented investigations concerning gene–nutrient interactions on energy homoeostasis and metabolic functions have suggested that inflammation could be not only a comorbidity of obesity but also a cause. There are several examples about the role of nutritional interventions in pregnancy and lactation, such as energetic deprivation, protein restriction and excess fat, which determine a cluster of disorders affecting energy efficiency in the offspring as well as different metabolic pathways, which are mediated by epigenetics encompassing the chromatin information encrypted by DNA methylation patterns, histone covalent modifications and non-coding RNA or microRNA. Epigenetic mechanisms may be boosted or impaired by dietary and environmental factors in the mother, intergenerationally or transiently transmitted, and could be involved in the obesity and inflammation susceptibility in the offspring. The aims currently pursued are the early identification of epigenetic biomarkers concerned in individual's disease susceptibility and the description of protocols for tailored dietary treatments/advice to counterbalance adverse epigenomic events. These approaches will allow diagnosis and prognosis implementation and facilitate therapeutic strategies in a personalised ‘epigenomically modelled’ manner to combat obesity and inflammation

Fat-to-glucose interconversion by hydrodynamic transfer of two glyoxylate cycle enzyme genes

The glyoxylate cycle, which is well characterized in higher plants and some microorganisms but not in vertebrates, is able to bypass the citric acid cycle to achieve fat-to-carbohydrate interconversion. In this context, the hydrodynamic transfer of two glyoxylate cycle enzymes, such as isocytrate lyase (ICL) and malate synthase (MS), could accomplish the shift of using fat for the synthesis of glucose. Therefore, 20 mice weighing 23.37 +/- 0.96 g were hydrodinamically gene transferred by administering into the tail vein a bolus with ICL and MS. After 36 hours, body weight, plasma glucose, respiratory quotient and energy expenditure were measured. The respiratory quotient was increased by gene transfer, which suggests that a higher carbohydrate/lipid ratio is oxidized in such animals. This application could help, if adequate protocols are designed, to induce fat utilization for glucose synthesis, which might be eventually useful to reduce body fat depots in situations of obesity and diabete

Dietary supplementation with methyl donors reduces fatty liver and modifies the fatty acid synthase DNA methylation profile in rats fed an obesogenic diet

Non-alcoholic fatty liver disease (NAFLD) is one of the first hepatic manifestations of metabolic syndrome, whose progression can lead to cirrhosis and hepatic carcinoma. Interestingly, methyl donor supplementation could improve obesogenic diet-induced hepatic triglyceride accumulation. The aim of this research is to describe methyl donor effects on a high-fat-sucrose (HFS) diet in both sexes and epigenetic changes induced on fatty acid synthase (FASN) promoter methylation pattern as well as gene expression of NAFLD key metabolic genes. Twenty-four male and 28 female Wistar rats were assigned to three dietary groups: control, HFS, and HFS supplemented with methyl donors (choline, betaine, vitamin B12, and folic acid). After 8 weeks of treatment, somatic, biochemical, mRNA, and epigenetic measurements were performed. Rats fed the HFS diet presented an overweight phenotype and alterations in plasma biochemical measurements. Methyl donor supplementation reverted the HFS-diet-induced hepatic triglyceride accumulation. Analysis of FASN promoter cytosine methylation showed changes in both sexes due to the obesogenic diet at -1,096, -780, -778, and -774 CpG sites with respect to the transcriptional start site. Methyl donor supplementation modified DNA methylation at -852, -833, -829, -743, and -733 CpGs depending on the sex. RT-PCR analysis confirmed that FASN expression tended to be altered in males. Our findings reinforce the hypothesis that methyl donor supplementation can prevent hepatic triglyceride accumulation induced by obesogenic diets in both sexes. Changes in liver gene expression profile and epigenetic-mediated mechanisms related to FASN DNA hypermethylation could be involved in methyl donor-induced NAFLD improvement

Leptin and TNF-alpha promoter methylation levels measured by MSP could predict the response to a low-calorie diet

Obesity-associated adipose tissue enlargement is characterized by an enhanced proinflammatory status and an elevated secretion of adipokines such as leptin and cytokines such as TNF-alpha. Among the different mechanisms that could underlie the interindividual differences in obesity, epigenetic regulation of gene expression has emerged as a potentially important determinant. Therefore, twenty-seven obese women (age: 32-50 years; baseline Body Mass Index, BMI: 34.4±4.2 Kg/m2) were prescribed an eight-week Low-Calorie-Diet and epigenetic marks were assessed. Baseline and endpoint anthropometric parameters were measured and blood samples were drawn. Genomic DNA and RNA from adipose tissue biopsies were isolated before and after the dietary intervention. Leptin and TNF-alpha promoter methylation were measured by MSP after bisulfite treatment and gene expression was also analyzed. Obese women with a successful weight loss (≥5% of initial body weight, n=21) improved the lipid profile and fat mass percentage (-12%, p<0.05). Both systolic (-5%, p<0.05) and diastolic (-8%, p<0.01) blood pressures significantly decreased. At baseline women with better response to the dietary intervention showed lower promoter methylation levels of leptin (-47%, p<0.05) and TNF-alpha (-39%, p=0.071) than the non-responder group (n=6), while no differences were found between responder and non-responder group in leptin and TNF-alpha gene expression analysis. These data suggest that leptin and TNF-alpha methylation levels could be used as epigenetic biomarkers concerning the response to a Low-Calorie-Diet. Indeed, methylation profile could help to predict the susceptibility to weight loss as well as some comorbidities such as hypertension or type 2 diabetes

A dual epigenomic approach for the search of obesity biomarkers: DNA methylation in relation to diet-induced weight loss

Epigenetics could help to explain individual differences in weight loss after an energy-restriction intervention. Here, we identify novel potential epigenetic biomarkers of weight loss, comparing DNA methylation patterns of high and low responders to a hypocaloric diet. Twenty-five overweight or obese men participated in an 8-wk caloric restriction intervention. DNA was isolated from peripheral blood mononuclear cells and treated with bisulfite. The basal and endpoint epigenetic differences between high and low responders were analyzed by methylation microarray, which was also useful in comparing epigenetic changes due to the nutrition intervention. Subsequently, MALDI-TOF mass spectrometry was used to validate several relevant CpGs and the surrounding regions. DNA methylation levels in several CpGs located in the ATP10A and CD44 genes showed statistical baseline differences depending on the weight-loss outcome. At the treatment endpoint, DNA methylation levels of several CpGs on the WT1 promoter were statistically more methylated in the high than in the low responders. Finally, different CpG sites from WT1 and ATP10A were significantly modified as a result of the intervention. In summary, hypocaloric-diet-induced weight loss in humans could alter DNA methylation status of specific genes. Moreover, baseline DNA methylation patterns may be used as epigenetic markers that could help to predict weight loss