Synthesis of Disentangled Ultra-High Molecular Weight Polyethylene: Influence of Reaction Medium on Material Properties

The polymerization of ethylene to Ultra-High Molecular Weight Polyethylene (UHMWPE) in certain reaction conditions allows synthesis of nascent powders with a considerably lower amount of entanglements: the material obtained is of great interest from both academic and industrial viewpoints. From an academic point of view, it is interesting to follow the evolution of the metastable melt state with the progressive entanglements formation. Industrially, it is valuable to have a solvent-free processing route for the production of high modulus, high strength tapes. Since the polymer synthesis is performed in the presence of a solvent, it is interesting to investigate the influence that the reaction medium can have on the catalyst activity, resultant molecular characteristics, and polymer morphology at the macroscopic as wells as microscopic level. In this paper, we present the effect that two typical polymerization solvents, toluene and heptane, and mixtures of them, have on the catalytic performance and on the polymer properties. The observations are that an unexpected increase of catalyst activity, accompanied by a significant improvement in mechanical properties, is found when using a carefully chosen mixture of solvents. A tentative explanation is given on the basis of the presented results

Synthesis of disentangled Ultra-High Molecular Weight Polyethylene: influence of reaction medium on material properties

The polymerization of ethylene to Ultra-High Molecular Weight Polyethylene (UHMWPE) in certain reaction conditions allows synthesis of nascent powders with a considerably lower amount of entanglements: the material obtained is of great interest from both academic and industrial viewpoints. From an academic point of view, it is interesting to follow the evolution of the metastable melt state with the progressive entanglements formation. Industrially, it is valuable to have a solvent-free processing route for the production of high modulus, high strength tapes. Since the polymer synthesis is performed in the presence of a solvent, it is interesting to investigate the influence that the reaction medium can have on the catalyst activity, resultant molecular characteristics and polymer morphology at the macroscopic as wells as microscopic level. In this paper we present the effect that two typical polymerization solvents, toluene and heptane, and mixtures of them, have on the catalytic performance and on the polymer properties. The observations are that an unexpected increase of catalyst activity, accompanied by a significant improvement in mechanical properties, is found when using a carefully chosen mixture of solvents. A tentative explanation is given on the basis of the presented results

Pelvetia canaliculata como suplemento de ração para dourada (Sparus aurata): uma abordagem de biorrefinaria para valorização da biomassa de algas

O contínuo aumento do setor da aquacultura tem trazido várias preocupações, sendo uma delas os impactos ambientais que provoca, visto que as rações são fabricadas à base de ingredientes de origem marinha, tais como a proteína e o óleo de peixe. As algas marinhas têm sido alvo de estudos, devido aos seus compostos bioativos com diversas atividades como antioxidante, com o propósito de tornar as aquaculturas sustentáveis e economicamente viáveis. Este estudo teve como objetivo avaliar a incorporação da alga P. canaliculata em pó (1%, 5% e 10%) e resíduo da mesma alga (1% e 10%), obtidos após a sua suplementação em óleo de girassol, em rações para aquacultura de dourada (Sparus aurata), e os efeitos que esta incorporação teve no desempenho de crescimento, perfil hematológico, parâmetros imunológicos, metabólicos, stress oxidativo e perfil nutricional do músculo. A suplementação das rações melhorou os parâmetros de crescimento, especialmente nos peixes alimentados com a dieta Resíduo 1%, não tendo afetado significativamente o perfil hematológico. No que respeitaao stress oxidativo, as douradasalimentadas com as dietas Pel 5% e 10% apresentaram melhores resultados, nomeadamente, nas atividades das enzimas catalase e superóxido dismutase. Nas análises da peroxidação lipídica, glutationa-s-transferase e glutationa total não se registaram diferenças provocadas pelas várias dietas estudadas. As amostras de músculo de peixes alimentados com a ração Pel 5% apresentaram o menor teor de lípidos, quantidade superior de proteína e maior percentagem de PUFA, características particularmente apreciadas pelos consumidores. Os resultados obtidos indiciam que a suplementação de rações com P. canaliculata liofilizada oucom oseu resíduo, obtidoapósincorporação em óleo de girassol, é adequada para a alimentação de juvenis de douradas em aquacultura.The continuous development of the aquaculture sector has brought several concerns, one of which is the environmental impacts it causes, as aquafeeds are made from ingredients of marine origin, such as protein and fish oil. Seaweed has been the subject of studies due to its bioactive compounds with various activities such as antioxidant, with the purpose of making aquaculture sustainable and economically viable. This study aimed to evaluate the effect of incorporating algae powder (1%, 5% and 10%) and algae waste, obtained after sunflower oil supplementation (1% and 10%) in aquafeeds for gilthead seabream (Sparus aurata), and the effects this incorporation had on growth performance, hematological profile, immunological parameters, metabolic, oxidative stress and muscle nutritional profile. Supplementation improved growth parameters, especially in fish fed with Waste 1%, not having greatly affected the hematological profile. Regarding oxidative stress, the sea bream fed with the Pel 5% and 10% diets showed better results, especially in the activities of the enzymes catalase and superoxide dismutase. In the analyses of lipid peroxidation, glutathione-s-transferase and total glutathione there were no differences caused by the various diets studied. Muscle samples from fish fed with 5% Pel diet showed the lowest lipid content, higher amount of protein and higher percentage of PUFA, characteristics particularly appreciated by consumers. The results obtained indicate that the supplementation of diets withfreeze-dried P. canaliculata, or its residue, obtained after incorporation into sunflower oil, is suitable for the feeding of juvenile sea bream in aquaculture

Metodologia de projeto de arquitetura paisagista: aplicação ao caso de jardins terapêuticos

Mestrado em Arquitetura Paisagista - Instituto Superior de AgronomiaThe evolution of times led to the advancement of medicine and living conditions, and the improvement of hygiene and food, resulting in social and demographic changes, especially the increase of life expectancy, and the consequent increase number of elderly. At a time when there exist a greater awareness of social problems, and the difficulties of some citizens, particularly in terms of accessibility and the lack of response to their needs, it becames increasingly relevant solve these problems, mainly because besides Portugal tend to increase elderly population, the social conscience also appeals that people with disability or disabilities are entitled to enjoy the day-to-day basis, without feelings of exclusion. Thus, this work explores how the Therapeutic Gardens and their components contribute to the recovery of people and provide a sense of well-being, in environments related to health, making reference to the principles of Inclusive Design, which establish guidelines for that products, equipment and services are accessible to anyone, regardless of their age group or limitations. As a result of this study presents a preliminary study for a landscape intervention on Hospital de São Francisco Xavier, in Lisbon

Process for manufacturing ultra high molecular weight polyethylene catalyst

The present invention pertains to a process for manufacturing an ultra-high molecular weight polyethylene, wherein olefin monomers are contacted with a catalytic system under polymerisation conditions under formation of a polyethylene, wherein the catalytic system comprises an active component on a particulate carrier in a site density in the range of 5* 10 (- 9) to 5*10 (-6) mole of catalytic sites per m2 of carrier surface area, the particulate carrier having an average particle diameter in the range of 1-300 nm, wherein the polyethylene has a weight average molecular weight (Mw) of at least 500 000 gram/mole, and an elastic shear modulus G0 N, determined directly after melting at 160°C of at most 1.4 MP a

Laser-flash in-plane thermal analysis: the case of oriented UHMWPE

Laser-flash thermal analysis has been applied to measure the thermal diffusivity of highly oriented samples of Ultra High Molecular Weight Polyethylene. Due to the anisotropy of the sample, in-plane measurements are required instead of through-plane ones

Revisiting Strategy and Performance Concepts in the Strategy Tripod Framework

The association between Strategy and Financial Performance is commonly used in scientific research. However, the dichotomy between deliberate and emergent strategies, although already discussed by several researchers, does not have a consensus in the literature. Also, the predominant practice in the academy investigates the financial perspective of performance and usually does not consider its plural aspects. Based on this reflection, this theoretical study discusses gaps in Peng's et al. (2009) strategy framework focusing on Strategy and Performance. As a result, we propose a review of the strategy framework, incorporating four strategic stages (deliberate, delibergent, emergent, and emergerate) and plural performance. We also propose methodological research that can be performed in business strategy.info:eu-repo/semantics/publishedVersio

Improved high-resolution GPR imaging and characterization of prehistoric archaeological features by means of attribute analysis

We propose a novel procedure for the analysis and interpretation of Ground-Penetrating Radar (GPR) data from archaeological data and we test the method in challenging conditions at a prehistoric settlement on the Stromboli Island (Italy). The main objective of the proposed procedure is to enhance the GPR capability of identifying and characterizing small-size and geometrically irregular archaeological remains buried beneath rough topographic surface conditions. After the basic GPR processing sequence, including topographic correction using a high-resolution Digital Elevation Model acquired from 3-D Laser Scanner, the procedure encompasses a multi-attribute analysis and iso-attribute surfaces calculation with different volume extraction solutions to emphasize vertical and lateral variations within GPR data cubes. The test was performed in cooperation with the archaeological team to calibrate the results and to provide detailed information about buried targets of potential archaeological interests to plan further excavations. The results gave evidence of localized buried remains and allowed detailed preexcavation planning. The archaeological excavations validated the results obtained from the GPR survey. The research demonstrates that the proposed GPR procedure enhances the ability to identify and characterize archaeological remains with high accuracy even in complex surface and subsurface conditions. Such logistical situation is very common, particularly in prehistoric sites, which are often characterized by discontinuous, small and irregular targets that cannot be identified by standard processing and analysis strategies

Metallic-like thermal conductivity in a lightweight insulator: solid-state processed Ultra High Molecular Weight Polyethylene tapes and films

Ultra High Molecular Weight Polyethylene with a reduced number of entanglements can be stretched in the solid state both uni- or biaxially to produce highly oriented tapes and films. The chain orientation, in combination with the reduced number of chain ends, is responsible for the high tensile modulus and tensile strength of the drawn materials, and, as we report here, also for the high thermal conductivity achieved through lattice movements. A property such as thermal conductivity in an electrical insulator makes UHMWPE tapes and films of great applicative interest. In-plane laser-flash thermal analysis has been applied to measure the thermal diffusivity of samples of different molecular weights stretched both uni- and biaxially, and a strong correlation has been found between the drawing ratio and the resulting in-plane thermal conductivity. Values of at least 40 W/m K have been achieved for UHMWPE having Mw comprised between 2 and 10 million, while higher values of 65 W/m K are observed for the higher Mw samples having relatively lesser number of chain ends. Surprisingly the biaxially stretched samples also show in-plane conductivity, with the highest value reaching 18 W/m K, comparable to stainless steel

High-toughness carbon cloth composites for low temperature applications

Carbon Fibre Reinforced Polymers based on a thermoplastic, high performance matrix such as Ultra High Molecular Weight Polyethylene have been produced using two different routes and it was found that in-situ polymerization of the matrix is a possible way forward to achieve a combination of high strength and high toughness in composites