Morphological characterization of injection molded parts in Ren Shape 5166 polyurethane inserts for rapid tooling

The Rapid Tooling techniques have been emerging to produce rapid moulds for injecting plas-tics parts. Among the current solutions, material removal by milling machining of polymeric resin or poly-meric composites is an attractive alternative for manufacturing moulds for injecting short series of products. This work assesses the morphology of parts injected in mould cavities manufactured by a polyurethane resin (PUR) Ren Shape 5166, as an alternative for Rapid Tooling, and the parts injected in cavities manufactured by the ordinary mould steel. Both cavities were used for injecting the parts with polypropylene. The speci-mens were characterized by Optical Microscopy and Differential Scanning Calorimetry, to observe the mor-phology and the resulting degree of crystallization from the moulding process. The results show the differ-ences in the microstructure structure from the parts injected in both cavities. It was observed that the parts injected in the PUR cavities are slightly more crystalline and display morphology different than the parts in-jected in the mould steel.Sociedade Edu-cacional de Santa Catarina (SOCIESC)CAPES - bolsa PROCAD 139/2007Promol-de research groupPROENGEN-HARIAS PE 27/2008 (Brasil

Rationale, study design, and analysis plan of the Alveolar Recruitment for ARDS Trial (ART): Study protocol for a randomized controlled trial

Background: Acute respiratory distress syndrome (ARDS) is associated with high in-hospital mortality. Alveolar recruitment followed by ventilation at optimal titrated PEEP may reduce ventilator-induced lung injury and improve oxygenation in patients with ARDS, but the effects on mortality and other clinical outcomes remain unknown. This article reports the rationale, study design, and analysis plan of the Alveolar Recruitment for ARDS Trial (ART). Methods/Design: ART is a pragmatic, multicenter, randomized (concealed), controlled trial, which aims to determine if maximum stepwise alveolar recruitment associated with PEEP titration is able to increase 28-day survival in patients with ARDS compared to conventional treatment (ARDSNet strategy). We will enroll adult patients with ARDS of less than 72 h duration. The intervention group will receive an alveolar recruitment maneuver, with stepwise increases of PEEP achieving 45 cmH(2)O and peak pressure of 60 cmH2O, followed by ventilation with optimal PEEP titrated according to the static compliance of the respiratory system. In the control group, mechanical ventilation will follow a conventional protocol (ARDSNet). In both groups, we will use controlled volume mode with low tidal volumes (4 to 6 mL/kg of predicted body weight) and targeting plateau pressure <= 30 cmH2O. The primary outcome is 28-day survival, and the secondary outcomes are: length of ICU stay; length of hospital stay; pneumothorax requiring chest tube during first 7 days; barotrauma during first 7 days; mechanical ventilation-free days from days 1 to 28; ICU, in-hospital, and 6-month survival. ART is an event-guided trial planned to last until 520 events (deaths within 28 days) are observed. These events allow detection of a hazard ratio of 0.75, with 90% power and two-tailed type I error of 5%. All analysis will follow the intention-to-treat principle. Discussion: If the ART strategy with maximum recruitment and PEEP titration improves 28-day survival, this will represent a notable advance to the care of ARDS patients. Conversely, if the ART strategy is similar or inferior to the current evidence-based strategy (ARDSNet), this should also change current practice as many institutions routinely employ recruitment maneuvers and set PEEP levels according to some titration method.Hospital do Coracao (HCor) as part of the Program 'Hospitais de Excelencia a Servico do SUS (PROADI-SUS)'Brazilian Ministry of Healt

Characterization of epoxy/steel fibres composites for hybrid injection moulds

Metallic fibres in polymeric matrix are used for mouldings blocks of hybrid injection moulds improving the mechanical and thermal properties. This paper reports on the characterization of epoxy resin/short steel fibres (SSF) composites. The effect of the concentration of 2,4,6-tris (di-methylamino-methyl) phenol as accelerator in the epoxy system was evaluated by viscosity and dynamical mechanical analyses. The composites were characterized by compression and micro-hardness tests. The fibres dispersion into the epoxy matrix was analysed by optical microscopy. It was found that the best accelerator concentration for this type of composite was 5,0 parts by weight.Portuguese Foundation for Science and Technology and the Brazilian Ministry of Education (Covenant FCT-CAPES

Characterization of epoxy/steel fibres composites for hybrid injection moulds

Metallic fibres in polymeric matrix are used for mouldings blocks of hybrid injection moulds improving the mechanical and thermal properties. This paper reports on the characterization of epoxy resin/short steel fibres (SSF) composites. The effect of the concentration of 2,4,6-tris (dimethylamino- methyl) phenol as accelerator in the epoxy system was evaluated by viscosity and dynamical mechanical analyses. The composites were characterized by compression and microhardness tests. The fibres dispersion into the epoxy matrix was analysed by optical microscopy. It was found that the best accelerator concentration for this type of composite was 5,0 parts by weight.Portuguese Foundation for Science and Technology and the Brazilian Ministry of Education (Covenant FCT-CAPES)

Influence of graphite and carbon nanotubes on the mechanical and electrical properties of cast epoxy composites

This study evaluates the influence of graphite and multi-wall carbon nanotubes on the mechanical and electric properties of cast epoxy resin. The epoxy resin based composites were prepared with various graphite and MWNCT content up to 5.0%. Specimens were characterized by DMA, SEM and electric resistivity tests. The observation of fracture surfaces showed a reasonable dispersion of graphite and MWCNT into the epoxy matrix. The graphite and MWCNT have almost the same effect in the electric conductivity of the epoxy composites at low content (0.2 and 0.5 %). The MWCNT composites seem to reach percolation at concentrations near 0.5 % whereas graphite composites reach it at 2%. Higher concentration of graphite and MWCNT have limited effect in the electric conductivity but reduces mechanical properties

A study on fiber sedimentation velocity in epoxy/steel fiber composites used for hybrid injection molds

Composites based on metallic fibers and thermosetting polymers are being increasingly used for molding blocks of hybrid injection molds, thereby improving the mechanical and thermal properties. However, an adequate study on the behavior of steel fibers in a reactive epoxy resin is necessary to understand how to maintain suitable mold properties. In this paper, the sedimentation velocity of short steel fiber suspensions in reactive epoxy resin was estimated using a model emerging from the Stokes equation and considering the resin rheology and correction factors for the fiber shape and concentration. DMP (2,4,6-tris (dimethylamino-methyl) phenol) was the accelerator more suitable for this type of composites because it increases the rate of cure and reduces the gel time more pronouncedly than any of the other common accelerators. Samples were manufactured with epoxy resin, short steel fiber and DMP as accelerator, and using anti-sedimentation equipment. The distribution of the fibers was observed in all composites. The viscosity data were used to predict the time in the anti-sedimentation equipment necessary to reach a minimum sedimentation velocity using the mathematical model. Results showed that this velocity is recommended to be below 3.28 × 10−8 m/s to avoid sedimentation of the steel fibers.Portuguese Foundation for Science and Technology / Brazilian Ministry of Education (Covenant FCT-CAPES)

A study on morphological properties of laser sintered functionally graded blends of amorphous thermoplastics

Parts with functionally graded composition of PMMA/PS blends manufactured by selective laser sintering are assessed in this study. The polymers and their blends were characterised by FTIR, SEM and DMA. The microstructure of PMMA and PS specimens are dependent on particle size and shape, laser absorption and flowability during processing. The FGM microstructures showed characteristics of the single polymers proportionally to their content. The PMMA/PS immiscibility was evidenced by fracture and DMA analysis. The initial material properties, the microstructure of the sintered blends and their mechanical properties are important to the design and optimal processing conditions of PMMA/PS FGM parts.The authors would like to thank FAPESC, CAPES, CNPq and FINEP for the financial support