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1	A unified model of necking and shear banding in amorphous and semicrystalline polymers Coates, Philip D., Sweeney, John, Caton-Rose, Philip D., Spares, Robert January 2007 (has links) No / In tensile stretching, many polymers undergo strain localization. The geometrical form of the localization can take the form of either a shear band or an approximately symmetric neck. We present a constitutive model of the early stages of deformation that predicts which form the localization will take. The model consists of an Eyring process acting with a Gaussian network that is implemented numerically. A Levy-Mises flow rule associated with the Eyring process has a tendency to produce shear bands. A relatively stiff Gaussian network is used in a model of polycarbonate that ensures that most of the strain is taken up by the Eyring process, resulting in shear banding. In contrast, a relatively soft Gaussian network is used in a model of polyethylene, which takes up the greater part of the strain, resulting in a neck. The predictions are compared with experiments. For polyethylene, a two-Eyring-process model is introduced for better accuracy. Mechanical properties Olefin polymer Numerical simulation Finite element method Gaussian network Eyring model Polyethylene Polycarbonate Semicrystalline polymer Amorphous polymer
2	The effect of screw geometry on melt temperature profile in single screw extrusion. Kelly, Adrian L., Brown, Elaine C., Coates, Philip D. January 2006 (has links) No / Experimental observations of melt temperature profiles and melting performance of extruder screws are reported. A novel temperature sensor consisting of a grid of thermocouple junctions was used to take multiple temperature readings in real time across melt flow in a single screw extruder. Melt pressure in the die and power consumption were also monitored. Three extruder screws at a range of screw speeds were examined for a commercial grade of low density polyethylene. Results showed melt temperature fields at low throughputs to be relatively independent of screw geometry with a flat-shaped temperature profile dominated by conduction. At high throughputs, melting performance and measured temperature fields were highly dependent upon screw geometry. A barrier-flighted screw with Maddock mixer achieved significantly better melting than single flighted screws. Low temperature "shoulder" regions were observed in the temperature profiles of single-flighted screws at high throughput, due to late melting of the solid bed. Stability of the melt flow was also dependent upon screw geometry and the barrier-flighted screw achieving flow with lower variation in melt pressure and temperature. Dimensionless numbers were used to analyze the relative importance of conduction, convection, and viscous shear to the state of the melt at a range of extrusion conditions. Olefin polymer Performance evaluation Pressure control Molten state Temperature control Process control Extrusion Single screw extruder Low density ethylene polymer Processing equipment Thread(screw)
3	Ultrasonic measurement of residual wall thickness during gas assisted injection moulding. Mulvaney-Johnson, Leigh, Brown, Elaine C., Coates, Philip D. January 2007 (has links) No / Ultrasonic technology provides a powerful and noninvasive method of in-process measurement during injection molding and extrusion. Changes in the velocity, attenuation and reflection coefficients of high frequency sound waves can be related to the state and conditions of the materials through which they propagate. The velocity of an ultrasonic wave changes with density and elastic moduli; this allows information on solidification and material properties to be collected during the molding cycle. The time of flight of the wave is a function of velocity and path length. This paper shows that it can be correlated with the residual wall thickness of polymer in the mold during gas assisted injection molding. Olefin polymer Experimental study Non destructive method Temperature effect Thickness measurement Ultrasonic method Wall thickness Property processing relationship High density ethylene polymer Gas injection Injection molding
4	Micromoulding: extreme process monitoring and in-line product assessment. Whiteside, Benjamin R., Howell, Ken B., Martyn, Michael T., Spares, Robert 08 June 2009 (has links) No / Advances in micromoulding technology are now allowing mass production of complex, three-dimensional functional products having sub-milligram masses and carefully tailored surface finishes. In order to create a viable manufacturing process for these components, accurate process monitoring and product evaluation are essential in order to highlight process problems and production of substandard parts. The present study describes work implementing a suite of sensors on a commercial micromoulding machine for detailed process interrogation. Evaluation of demoulded products is performed with a single camera based system combined with custom software to allow for three-dimensional characterisation of products during the process. Monitoring High density ethylene polymer Modeling Olefin polymer Molding Experimental study Image analysis Three dimensional model Defect detection Optimization Temperature control Pressure control Process control Microinjection Processing parameter Injection molding
5	A process recipe for bonding a silicone membrane to a plastic substrate Schönström, Linus, Nordh, Anna, Strignert, Anton, Lemel, Frida, Ekengard, Jakob, Wallin, Sofie, Jabri, Zargham January 2013 (has links) A spin-cast silicone membrane has been successfully bonded between two injection-molded microstructured plastic discs. This sandwich structure creates a useful platform for mass production of microfluidic systems, provided that the bonds are leakproof. The bonds were achieved by a silicon dioxide coating deposited on the plastic discs by evaporation. This investigation is concerned with the process and the result only, no theory is discussed. bonding silicone corona surface treater SiO2 coating thermoplastic substrate PVD temperature PDMS membrane spin-coating thickness measurements microfluidic systems bonding PDMS silicon dioxide coating spin-cast silicone membrane PDMS polydimethylsiloxane poly(dimethylsiloxane) silicon dioxide PVD SiO2 PVD silicon dioxide evaporation SiO2 evaporation thickness of a thin film silicon dioxide deposition SiO2 deposition adhesion testing cycloolefincopolymer cycloolefinpolymer cyclic olefin copolymer cyclic olefin polymer COC COP plasma surface treater surface activator surface oxidizer

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