Impact performance prediction of injection-molded talc-filled polypropylene through thermomechanical environment assessment

Due to the fact that different injection molding conditions tailor the mechanical response of the thermoplastic material, such effect must be considered earlier in the product development process. The existing approaches implemented in different commercial software solutions are very limited in their capabilities to estimate the influence of processing conditions on the mechanical properties. Thus, the accuracy of predictive simulations could be improved. In this study, we demonstrate how to establish straightforward processing-impact property relationships of talc-filled injection-molded polypropylene disc-shaped parts by assessing the thermomechanical environment (TME). To investigate the relationship between impact properties and the key operative variables (flow rate, melt and mold temperature, and holding pressure), the design of experiments approach was applied to systematically vary the TME of molded samples. The TME is characterized on computer flow simulation outputsanddefined bytwo thermomechanical indices (TMI): the cooling index (CI; associated to the core features) and the thermo-stress index (TSI; related to the skin features). The TMI methodology coupled to an integrated simulation program has been developed as a tool to predict the impact response. The dynamic impact properties (peak force, peak energy, and puncture energy) were evaluated using instrumented falling weight impact tests and were all found to be similarly affected by the imposed TME. The most important molding parameters affecting the impact properties were found to be the processing temperatures (melt andmold). CI revealed greater importance for the impact response than TSI. The developed integrative tool provided truthful predictions for the envisaged impact properties.

Biotechnological approaches for yield improvement of anticancer alkaloids in the plant Catharanthus roseus

Dissertação de mestrado em Biologia Molecular, Biotecnologia e Bioempreendedorismo em Plantas

Development of advanced cell/tissue culture systems, based on enhanced polymeric scaffolds and sophisticated bioreactors, for tissue engineering applications

Programa Doutoral em Engenharia Biomédica

Enzymes which detoxify ochratoxin A

Mycotoxins are fungal secondary metabolites found in some agricultural commodities which are toxic for humans and animals in small amounts. Mycotoxins are a global problem which can be partially controlled through prevention strategies that can be applied along the food and feed chain production. However, when mycotoxin formation can not be avoided and they come to be present in commodities some remediation strategies can also be used to reduce its levels on products, its bioavailability or its toxic effects. Among these remediation strategies, the biological methods are recently holding a relevant position, being widely studied in the last years. As a result, a great number of microorganisms that can degrade or detoxify several mycotoxins and the application of some of them were reported. Moreover, several enzymes which mediate these biological processes were identified, being by themselves studied in order to develop new biotechnological approaches to control the mycotoxin problem on commodities. The main enzymes known to detoxify ochratoxin A, their action and their present application in order to counteract the referred problem are reviewed and critically assessed.