On the design of co-extrusion dies for polymeric multilayer products

The authors would like to acknowledge the funding by FEDER funds through the COMPETE 2020 Programme and National Funds through FCT - Portuguese Foundation for Science and Technology under the projects UIDB/05256/2020/UIDP/05256/2020 and TSSiPRO - Technologies for Sustainable and Smart Innovative Products (NORTE-01- 0145-FEDER-000015). The authors also acknowledge the support of the computational clusters Search-ON2 (NORTE-07-0162-FEDER-000086) and Minho Advanced Computing Center (MACC). M.M. Martins would like to thank also the support of the University Centre - Catholic of Santa Catarina (Brazil)

Using computational modelling to improve the insight regarding multi-layer polymer flows in co-extrusion

Polymer multilayer co-extrusion is a manufacturing process wherein two or more polymers feed a common extrusion die to form a layered product, aiming to combine in a synergic way the properties of the individual polymers comprising each layer [1]. The usual manufacturing approach starts by co-extruding two layers which are duplicated in each Interfacial Surface Generator Module (ISGM) employed, see Figure 1. This is achieved by dividing the flow of the two inlet layers (AB) in the division region, deforming and overlapping the two individual streams, which are subsequently joined in the junction region to reach a 4 layer structure (ABAB) [2]. In this way, each ISGM employed allows duplicating the number of layers in the final product.This work is funded by National Funds through FCT - Portuguese Foundation for Science and Technology, Reference UID/CTM/50025/2019. The authors would like also to thank the support of the Search Cluster, Project TSSIPRO - Portugal and University Centre - Catholic of Santa Catarina - Brazil

Verification and validation of openInjMoldSim, an open-source solver to model the filling stage of thermoplastic injection molding

In the present study, the simulation of the three-dimensional (3D) non-isothermal, non-Newtonian fluid flow of polymer melts is investigated. In particular, the filling stage of thermoplastic injection molding is numerically studied with a solver implemented in the open-source computational library O p e n F O A M ® . The numerical method is based on a compressible two-phase flow model, developed following a cell-centered unstructured finite volume discretization scheme, combined with a volume-of-fluid (VOF) technique for the interface capturing. Additionally, the Cross-WLF (Williams–Landel–Ferry) model is used to characterize the rheological behavior of the polymer melts, and the modified Tait equation is used as the equation of state. To verify the numerical implementation, the code predictions are first compared with analytical solutions, for a Newtonian fluid flowing through a cylindrical channel. Subsequently, the melt filling process of a non-Newtonian fluid (Cross-WLF) in a rectangular cavity with a cylindrical insert and in a tensile test specimen are studied. The predicted melt flow front interface and fields (pressure, velocity, and temperature) contours are found to be in good agreement with the reference solutions, obtained with the proprietary software M o l d e x 3 D ® . Additionally, the computational effort, measured by the elapsed wall-time of the simulations, is analyzed for both the open-source and proprietary software, and both are found to be similar for the same level of accuracy, when the parallelization capabilities of O p e n F O A M ® are employed.This work is funded by FEDER funds through the COMPETE 2020 Programme and National Funds through FCT (Portuguese Foundation for Science and Technology) under the projects UID-B/05256/2020, UID-P/05256/2020, MOLDPRO-Aproximações multi-escala para moldação por injeção de materiais plásticos (POCI-01-0145-FEDER-016665), and FAMEST-Footwear, Advanced Materials, Equipment’s and Software Technologies (POCI-01-0247-FEDER-024529)

Development of the drag coefficient of a sphere translating through a viscoelastic fluid

Presentation at 15th OpenFOAM Workshop, June 22-25, 2020, Arlington, VA, USA

Using computational modelling to study extensional rheometry tests for inelastic fluids

The present work focuses on the extensional rheometry test, performed with the Sentmanat extensional rheometer (SER) device, and its main objectives are: (i) to establish the modelling requirements, such as the geometry of the computational domain, initial and boundary conditions, appropriate case setup, and (ii) to investigate the effect of self-induced errors, namely on the sample dimensions and test temperature, on the extensional viscosity obtained through the extensional rheometry tests. The definition of the modelling setup also comprised the selection of the appropriate mesh refinement level to model the process and the conclusion that gravity can be neglected without affecting the numerical predictions. The subsequent study allowed us to conclude that the errors on the sample dimensions have similar effects, originating differences on the extensional viscosity proportional to the induced variations. On the other hand, errors of a similar order of magnitude on the test temperature promote a significant difference in the predicted extensional viscosity.This work was funded by FEDER funds through the COMPETE 2020 Program and National Funds through FCT-Portuguese Foundation for Science and Technology under the projects UIDB/05256/2020/, UIDP/05256/2020, CPCA/A2/6202/2020, CPCA_A2_6231_2020, NORTE-08-5369- FSE-000034, under program IMPULSE-Polímeros e Compósitos: Drivers da Inovação Tecnológica e da Competitividade Industrial

Preparo de soluções.

Introdução; Cuidados gerais no preparo das soluções; Concentração de soluções; Diluição de soluções; Transformações mais usadas; exercicios sobre calculos de soluções;bitstream/CNPA-2009-09/14619/1/CIRTEC42.pd

Eco-friendly polymeric material for horticulture application

Poly(lactic acid) (PLA), was mixed with wood fibers, coffee grounds, fertilizer and a foaming agent to developed a ecofriendly material to be used in horticulture. The developed materials should have mechanical properties similar to PLA, increasing biodegradability and lower price. The materials were prepared by melt processing in an internal mixer at 190ºC and were characterized by several techniques. The mechanical properties of the bio-composites, measured by flexural tests, were similar to neat PLA even with a reduction of 40 wt. % of polymer. Biodegradation assessment by composting tests in aerobic environment demonstrated that the green materials developed exhibited higher biodegradability than PLA. Bio-composites containing wood fibers and fertilizer revealed to be the most suitable for horticulture application, since these can combine mechanical properties, biodegradability and fertilizer release. Moreover, this green material has two main advantages, it can be prepared using materials from natural resources and does not generate any residue after use

Are the Tails of Percolation Thresholds Gaussians ?

The probability distribution of percolation thresholds in finite lattices were first believed to follow a normal Gaussian behaviour. With increasing computer power and more efficient simulational techniques, this belief turned to a stretched exponential behaviour, instead. Here, based on a further improvement of Monte Carlo data, we show evidences that this question is not yet answered at all.Comment: 7 pages including 3 figure