Ejection force of tubular injection moldings. Part II : a prediction model

The integrated knowledge of the injection molding process and the material changes induced by processing is essential to guarantee the quality of technical parts. In the case of parts with deep cavities, quite often the ejection phase of the molding cycle is critical. Thus, in the mold design stage, the aspects associated with the ejection system will require special consideration. In particular, the prediction of the ejection force will contribute to optimizing the mold design and to guarantee the integrity of the moldings. In this work, a simulation algorithm based on a thermomechanical model is described and their predictions are compared with experimental data obtained from a fully-instrumented mold (pressure, temperature, and force). Three common thermoplastics polymers were used for the tubular moldings: a semicrystalline polypropylene and two amorphous thermoplastics: polystyrene and polycarbonate. The thermomechanical model is based on the assumption of the polymer behavior changing from purely viscous to purely elastic below a transition point. This point corresponds to solidification determined by temperature in the case of amorphous materials and by critical crystallinity for semicrystalline polymers. The model results for the ejection force closely agree with the experimental data for the three materials used

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

Glass fibre content of PP plates and their properties: part II: tensile mechanical properties

Short fibre reinforced polypropylene compounds have been used to produce composites taking advantage of its interesting properties and competitive raw material prices. For the same reason the short glass fibres are the most used reinforcement in injection moulded thermoplastic composites. In injection moulding, varying patterns of fibre orientation are obtained through the thickness direction and along the flow path. Moulding parameters such as injection flow rate or melt-temperature do affect the fibre orientation distributions in mouldings. It has been observed that the type of flow, being dominated by shear stresses (e.g. linear flow) or by extensional stresses (e.g. radial flow) affects the fibre orientation field. Other parameters may have an effect over the fibre orientation such as the fibre length distribution. During processing some degree of fibre breakage in unavoidable. The fibre contents, its length and orientation distributions cause anisotropy on mechanical properties. Efficient reinforcements are obtained in the direction of major orientation of the fibres and when longer fibres are used. In this work the effect of various fibre contents, by volume (0, 10, 20 and 25%) over the anisotropy of mechanical properties of injection moulded rectangular plates is explored. Specimens cut along and across the flow directions are subjected to tensile tests enabling to discuss the anisotropy of tensile mechanical properties.(undefined

Glass fibre contents of PP plates and their properties: part I: Shrinkage and changes in time

In this paper the results from the first part of a study on the glass fibre contents of PP plates and their properties is presented. Focus is made on the effect of the fibre volume fraction and holding pressure on the experimental as-moulded shrinkage in the flow and across flow directions. Data is also presented on the post-moulding shrinkage. For the experimental work, PP with different volume fraction of glass fibre (0, 0.1, 0.2 and 0.25) was used. The mouldings are edge gated flat rectangular plates. The moulding process was continuously monitored with pressure transducers.(undefined

1D mapping of seminal plasma proteins in Anglo-Nubian goats.

The lack of information about seasonal variation of seminal plasma proteins in goats from Northeast Brazil led us to investigate the protein band distribution throughout the year. The experiment lasted one year (from April 2006 to March 2007) in which 230 semen collections from five adult goats (Capra hircus) were carried out, at ages ranging from 18 to 22 months, weighing 42.0 ± 10.0 kg, belonging to Anglo Nubian breed. A pool of seminal plasma samples from all the animals in each month of the year was submitted to 1D electrophoresis SDS-PAGE, 12.5%. The gels were analyzed through Life Science Software from UVP, Inc®. The correlation between air humidity and total seminal plasma proteins was not significant (r = -0.24; P > 0.05), while a moderate and significant correlation was found between temperature and total protein (r = 0.39; P 0.05). The analyzed gels showed a high frequency of molecular mass bands below 50 kDa throughout the year, followed by protein bands from 50 to 100 kDa. The major numbers of bands occurred in October and November, while May was the month that presented a smaller number of protein bands. The molecular bands of 14, 22, 24, 40, 55 and 66 kDa were present in all the months of the year. The band of 16 kDa was found in 41.7% of the months. May was the only month that did not show the 30 kDa. August and September did not present the bands of 34 and 35 kDa, while October showed both bands. The 45 kDa band was found in 75% of the months, being present in January, May, July, September and November. The 46 kDa band was identified in June and August, while the 47 kDa was identified in April. The 70 kDa band was identified from May to November (58.3%), the 72 kDa band was found in January, March and April (25%) and bands of 92 to 97 kDa were found from April to December (75%). These results showed a band distribution variation throughout the year in the Anglo Nubian goat breed in the semi-arid area of Brazil. It is concluded that medium rainfall or water scarcity in the dryer months seems to promote variation in semen volume and concentration and total protein distribution throughout the year. As no month variation was observed in semen motility and vigor, and protein bands probably related to fertility showed an uniform distribution throughout the year, it is suggested that there is no fertility variation during the year in Anglo-Nubian goats the semi-arid region.Meta 2010

Uso de ferramentas biotecnológicas para o manejo do HLB dos citros.

O huanglongbing (HLB ou greening) dos citros é uma doença devastadora, conhecida há cerca de 100 anos em países da Ásia e da África. Relatada no Estado de São Paulo em 2004 (COLETTA-FILHO et al., 2004), a doença tem se disseminado rapidamente para novas áreas das Américas juntamente com seu vetor, o psilídeo Diaphorina citri. O controle do HLB apregoado até o momento baseia-se no tripé: uso de mudas sadias, erradicação de plantas sintomáticas e controle químico do vetor (GOTTWALD, 2010)

Prevalence of Xanthomonas perforans associated with bacterial spot in processing tomato crops in Brazil.

Resumo 1012

Uso do decanoato de nandrolona (Decadurabolin®) como estimulante da proliferação óssea em cães com consolidação retardada

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