The effect of holding pressure on the shrinkage and birefringence of injection moulded polypropylene plates

This paper shows the results of shrinkage and birefringence of injection moulded plates. The study was done with two polypropylenes with different MFI. Focus is made on the effect of the holding pressure on the experimental as-moulded shrinkage and birefringence in the flow direction. The mouldings are edge gated flat rectangular plate. The moulding process was continuously monitored with pressure transducers. The results show that the rise of holding pressure determines the decrease of the shrinkage. Also, it was observed that the increase of the pressure applied during the holding phase and the associated flow induce re-orientation of the melt, especially in the case of higher molecular weight PP. Consequently, an increase in the birefringence results.(undefined

Procedimento de operação, manutenção e verificação de centrífuga JOUAN refrigerada.

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Effect of melt viscosity on the ejection force in injection moulds

This paper shows data on the ejection force of injection mouldings. The tubular mouldings are pin gated. Two polypropylenes with different melt viscosities (melt flow indices) were investigated. Experimental focus is put on the effect of the holding pressure, mould temperature and the cooling time on the measured ejection force. Pressure and temperature were continuously monitored with transducers during the filling process. The ejection force was directly measured with load cells. The results show that higher viscosity lends to higher ejection force.(undefined

Experimental validation of morphology simulation in glass fibre reinforced polycarbonate discs

As assessment is made between Moldflow simulations and experimentally determined fibre orientation distributions at three points along the flow path and 12 layers across the thickness. The material used is a 10% weight short glass fibre reinforced polycarbonate. With this material the physical interaction between fibres during flow is minimised. Centre gated circular discs, where both the shear and the extensional flows are present, were produced over a range of moulding conditions to analyse the effect of flow rate and melt temperature upon the fibre orientation. The fibre orientation was measured using image analysis tools in images obtained by reflection microscopy of polished sections, using the method proposed by Bay. The measurements were made in 12 layers across the thickness

Esteatose hepática em crianças e adolescentes obesos

Objective: To assess the frequency of hepatic steatosis and metabolic syndrome among obese children and adolescents.Method: A descriptive case series was conducted with 77 patients, aged 2 to 13 years and 11 months, who were followed up from February to July 2007. Obesity was defined as body mass index >= P-95 adjusted for age and sex. Liver ultrasound was performed to diagnose hepatic steatosis. Metabolic syndrome was defined according to the modified criteria suggested by Cook et al.Results: Hepatic steatosis was diagnosed in 33/77 patients (42.9%), 25/33 (75.8%) with mild steatosis and 8/33 (24.2%) with moderate steatosis. Those aged less than 10 years showed only mild steatosis, and the moderate degree of the disease was restricted to adolescents. Aminotransferase alterations were found in 9.1% (3/33) of patients with hepatic steatosis and in 4.9% (2/41) of those without the disorder. Mean waist circumference was 84.74 +/- 2.84 cm for patients with hepatic steatosis and 78.24 +/- 1.60 cm for those without the disease (p = 0.04). Metabolic syndrome was diagnosed in 27.3% (21/77) of obese patients, 47.6% (10/21) of them having steatosis, 60% had mild steatosis and 40% had a moderate degree of the disorder.Conclusions: the frequency of hepatic steatosis and metabolic syndrome was high. the association of larger waist circumference with hepatic steatosis highlights the importance of taking this parameter into consideration when investigating obese patients.Fundacao de Amparo a Ciencia e Tecnologia do estado de Pernambuco (FACEPE)Univ Fed Pernambuco, Dept Materno Infantil, Ctr Ciencias Saude, Recife, PE, BrazilHosp Barao Lucena, Serv Endocrinol Pediat, Recife, PE, BrazilUniversidade Federal de São Paulo, EPM, São Paulo, BrazilUniversidade Federal de São Paulo, EPM, São Paulo, BrazilWeb of Scienc

Susceptibility of Hypsipyla grandella (Lepidoptera: Pyralidae) to Bacillus thuringiensis strains.

Na publicação: Rose Gomes Monnerat

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