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

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

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

Characterization of polymer behavior in microchannels

Microinjection moulding can be used to process monitoring and rheological characterization, can help to understand the behavior of polymer melt flows during the filing of micro cavities. The system used allows a study on characterization of polymer behavior in microchannels. This approach is appropriate since rheological phenomena such as wall slip, surface tension, melt pressure drop and polymer flow length can be studied. In this system, the data acquisition has made by incorporation of two sensors inside the mould

Surface property effects of compounding a nanoclay masterbatch in PP injection moulding

Indicado para o prémio de melhor artigo mais inovador.The interest on the use of nanofillers in injection mouldings has been going on for more than a decade but a real breakthrough has not been achieved yet, especially in that mechanical properties are concerned. The nucleating effect of nanoclays in semicrystalline polymers suggests that surface effects may result interesting especially during processing. This paper includes some information on the surface properties of an injection moulding grade of polypropylene mixed with a commercial masterbatch of PP and 50% of organoclay. They were moulded as plates for testing in a prototype device for determining the coefficient of friction in as-moulding conditions. The surface was also characterised by depth sensing indentation tests. The through thickness microstructures of the mouldings were assessed by optical microscopy and differential scanning calorimetry, while surface morphology was assessed by X-ray diffraction. It was observed that independently of MB content, its addition caused a slight increase in elastic modulus and hardness in the skin layer.The friction properties directly associable to the product performance showed a slight improvement in terms of the dynamic friction coefficient. Conversely the static friction coefficient that is relevant in processing was no affected by the presence of the nanoclay

Characterization of polymer behaviour in microchannels

Publicado em “Proceedings of PPS-29 : The 29th International Conference of the Polymer Processing Society - Conference Papers. ISBN 978-0-7354-1227-9”Microinjection moulding can be used to process monitoring and rheological characterization can help to understand the behavior of polymer melt flows during the filing of micro cavities. The system used allows a study on characterization of polymer behavior in microchannels. This approach is appropriate since rheological phenomena such as wall slip, surface tension, melt pressure drop and polymer flow length can be studied. In this system, the data acquisition has made by incorporation of two sensors inside 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