Functionalized carbon nanotubes-polyamide composites produced by microinjection moulding

Polymer composites containing carbon nanotubes (CNT) have attracted much attention due to the possibility to obtain electrically conductive and reinforcing materials at relatively low CNT concentrations, and for their potential applications in electronics, and chemical and biological sensing. Microinjection molding (μIM) is an emerging efficient and cost-effective process for the large-scale production of thermoplastic nanocomposite microparts. The present work reports the dispersion of CNT in polyamide 6 (PA 6) for the production of nanocomposites with different amounts of functionalized and non-functionalized CNT. The nanocomposites were microinjection molded under specific conditions and the electrical and mechanical properties of the specimens obtained were measured.Fundação para a Ciência e a Tecnologia (FCT) - POCI/QUI/59835/2004, bolsa de doutoramento T. Ferreira (SFRH/BD/39119/2007)

Linfangioleiomiomatose pulmonar inicial provável e linfangioleiomioma mediastinal

A 68 year old woman was submitted to a mediastinal lymphangioleiomyoma resection found in a follow-up study of lower left lung resection due to bronchiectasis complicated by chylothorax. This led to a revaluation of the pulmonary specimen that revealed, in addition to inflammatory bronchiectasis, small spindle cell nodules in the lung parenchyma, similar to minute pulmonary meningothelial-like nodules, but with smooth muscle actin immunohistochemical positivity. The possibility of initial pulmonary development of lymphangioleiomyomatosis is discussed

Influence of the local morphology on the surface tension of injection molded polypropylene

Publicado em “Proceedings of PPS-29 : The 29th International Conference of the Polymer Processing Society - Conference Papers. ISBN 978-0-7354-1227-9”In this work, we investigate the development of the morphology of an injection molding polypropylene under the local thermomechanical environment imposed during processing, and its effect on the contact angle and, hence, on the surface tension of the moldings. Melt and mold temperatures were varied in two levels. The local thermomechanical environment was characterized by mold filling computational simulations that allow the calculation of thermomechanical variables (e.g., local temperatures, shear stresses) and indices (related to the local morphology development). In order to investigate the structural hierarchy variations of the moldings in the thickness direction, samples from skin to core were used. The molecular orientation and degree of crystallinity were determined as function of the thickness, as well as the contact angle. The variations of the degree of crystallinity were assessed by differential scanning calorimetry. The level of molecular orientation was evaluated by birefringence measurements. The contact angles were measured in deionized water by sessile drop (needle in) method at room temperature, to determine the wettability of the samples. The contact angles were found to vary along the molding thickness in the skin, transition and core layers. These variations are related to the local morphologies developed. Results suggest that water contact angle increases with the level of molecular orientation and for finer microstructures

A study on shrinkage and warpage of rotational moulded polyethylene

Warpage and poor dimensional stability of rotomoulded products are two of the main obstacles to the use of this technique in the production of engineering parts. The knowledge of the effect of the processing conditions on the shrinkage of rotomoulded parts will allow overcoming some of the restrictions of this process. In the present work the influence of the processing conditions on the development of shrinkage and warpage of rotomoulded parts was studied. The moulding of the parts was performed using a rotational moulding machine build at the University of Minho. The shrinkage and the warpage of the moulded parts were assessed using 3D MMC (3D measuring Machine Control) equipment, and understanding the microstructural development

Model to predict shrinkage and ejection forces of injection moulded tubular parts of short glass fiber reinforced thermoplastics

This work presents a model to predict shrinkage and ejection forces for glass fiber reinforced thermoplastics of tubular geometry. This mathematical model was based in Jansen’s Model to predict shrinkage and residual stresses in fiber reinforced injection molded products and Pontes’s Model to predict ejection forces for tubular parts of pure PP. The model used the modified classical laminate theory applied to injection moulding and it uses the fiber orientation state, temperature and pressure field as input and which predicts the shrinkage and ejection forces. The fiber orientation state was determined experimentally and the temperature and pressure fields were obtained by MOLDFLOW simulations. The model to predict ejection forces considers also the fiber orientation state, friction coefficient between steel and polymer, elastic modulus of polymer, both in the ejection temperature and diametrical shrinkage. The model is validated by experimental results

Assessment of the shrinkage and ejection forces of reinforced polypropylene based on nanoclays and short glass fibre

In this study the influence of nanoclay and glass fibre in the shrinkage and ejection forces in polypropylene matrix in tubular parts moulded by injection moulding were analysed. An instrumented mould was used to measure the part surface temperature and ejection forces in tubular parts. The materials used were a polypropylene homopolymer Domolen 1100L nanoclay for polyolefin nanocomposites P-802 Nanomax in percentages of 2%, 6% and 10% and a polypropylene homopolymer with content of 10% of glass fibre Domolen P1-013-V10-N and 30% of glass fibre Domolen P1-102-V30-N with 2% of nanoclay. The shrinkage and ejection forces were analysed. The results show that the incorporation of nanoclays decreases the shrinkage and ejection forces whereas glass fibre decreases the shrinkage and increase ejection forces due to the increase of the elastic modulus. The nanoclays decrease the ejection force when compared with glass fibre and pure PP. The effects of nanoclays are less pronounced than those of glass fibre. The effect of the mould temperatures on the ejection forces in the mouldings produced with the mentioned materials were also analysed. The ejection force decreases with the increase of the temperature of the mould

Design of nozzles for surface mount technologies produced by additive manufacturing

The increasing use and production of electronic systems, equipped with multiple PCBs, leads to constant development in manufacturing technologies. A predominant choice in PCB production is Surface Mount Technology (SMT). The most important phase of the SMT process is the pickup and placement step, where nozzles, specific to the electronic component, are responsible to pick components and place them on the PCB. The interaction between the nozzles and the components imposes issues that lead to losses of process productivity. Currently, the development of a nozzle for an electrical component is time-consuming and, sometimes, the final solution is not tailored enough to take full advantage of the SMT machine efficiency. This research aims to fill this gap, through a new nozzle production method using additive manufacturing (AM), which makes it possible to respond to requirements such as, real-time, customized, and high dimensional accuracy nozzle design and production. Despite these advantages, the materials and manufacturing technologies available need improvements to meet the SMT requirements for nozzles production. Therefore, the research focused on the development of an electrostatic discharge (ESD) solution for AM, and the study of geometries that allow vacuum picking of electronic components with zero or low leakage. To show the viability of this method, electrical characterization tests were performed on the materials used, showing that ESD properties could be achieved. Moreover, a set of experimental tests were also performed to prove that the vacuum values were in the same range as the traditional nozzles. In sum, this research presents an alternative solution that allows for quick and flexible nozzle production.- (undefined

Evaluation of active heat sinks design under forced convection—effect of geometric and boundary parameters

This study shows the performance of heat sinks (HS) with different designs under forced convection, varying geometric and boundary parameters, via computational fluid dynamics simulations. Initially, a complete and detailed analysis of the thermal performance of various conventional HS designs was taken. Afterwards, HS designs were modified following some additive manufacturing approaches. The HS performance was compared by measuring their temperatures and pressure drop after 15 s. Smaller diameters/thicknesses and larger fins/pins spacing provided better results. For fins HS, the use of radial fins, with an inverted trapezoidal shape and with larger holes was advantageous. Regarding pins HS, the best option contemplated circular pins in combination with frontal holes in their structure. Additionally, lattice HS, only possible to be produced by additive manufacturing, was also studied. Lower temperatures were obtained with a hexagon unit cell. Lastly, a comparison between the best HS in each category showed a lower thermal resistance for lattice HS. Despite the increase of at least 38% in pressure drop, a consequence of its frontal area, the temperature was 26% and 56% lower when compared to conventional pins and fins HS, respectively, and 9% and 28% lower when compared to the best pins and best fins of this study.This research was funded by Portuguese Fundação para a Ciência e a Tecnologia (FCT), for financial support under the PhD scholarship SFRH/BD/144590/2019 and by European Structural and Investment Funds in the FEDER component, through the Operational Competitiveness and Internationalization Programme (COMPETE 2020) [Project No. 039334; Funding Reference: POCI-01- 0247-FEDER-039334]

Composite materials with MWCNT processed by Selective Laser Sintering for electrostatic discharge applications

Selective Laser Sintering (SLS) is an additive manufacturing technology that enables the production of polymeric parts for end-use applications. Despite the great potential of conventional materials, carbon-based reinforcements have been widely considered to contradict the electrically insulating nature of polymers, allowing the applicability of SLS in novel applications within electronics industry. However, the laser-sintering processing of such materials still encompasses a number of limitations including agglomeration problems, weak interparticle adhesion, low parts resolution, high processing time and costs. Therefore, this research reports the development of functional composite materials for SLS capable of being considered for the production of components that are in direct contact with electrostatic discharge (ESD) sensitive devices. To do so, composite materials of Polyamide 12 incorporating 0.50 wt%, 1.75 wt% and 3.00 wt% of Multi-Walled Carbon Nanotubes were developed aiming to achieve values of surface resistance between 104 - 109 Ω, according to the delivery instructions of Bosch Car Multimedia S.A. Test specimens produced by SLS were dimensionally, mechanically, electrically, thermally and morphologically characterized. Comparing to the neat matrix, the composite materials revealed narrower SLS processing window, reduced mechanical strength, surface resistance in the ESD range and electrical conductivity until 10−6 S/cm. Fundamentals on the sintering process of these functional materials are also provided.This work was co-funded by the European Regional Development Fund through the Operational Competitiveness and Internationalization Programme (COMPETE 2020) [Project No. 47108, “SIFA”; Funding Reference: POCI-01-0247-FEDER-047108] and by the Foundation for Science and Technology (FCT) through the PhD scholarship 2020.04520.BD