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Benefits of Servo-Driven Ultrasonic Welding for Critical Assemblies
Ultrasonic welding is one of the most widely used processes for bonding polymers, valued for its speed, flexibility, and low cost. Recently, there has been a call for more controlled and consistent ultrasonic welding processes, as part designs become more complex and requirements more stringent, especially in the medical field and for complex packaging applications. Additionally, the processes used to meet these increasing demands must be consistent and repeatable over time. Dukane has worked to meet this demand through the development of a new iQ series Servo-Driven Ultrasonic Welder with Melt-Match® technology, which is protected by US and international patents with other US and international patents pending [1, 2, 3, 4]. This study explores the potential benefits of the features solely available with Dukane’s servo-driven welders, such as Melt-Match® (matching welding speed with the melt flow rate of the plastic). A full scale Design of Experiments has been undertaken to identify the relational effects of these speed and distance control features and how they can be used to optimize the welding process. An effort has been made to detail and quantify the improvement to the weld joint based both on previous research, including a joint study with Value Plastics, a large medical device manufacturer, and new experimentation in collaboration with Parker Hannifin.
Aspects of Physical Aging and Thermal Annealing in a New Copolyester
Long-term effects of physical aging and thermal annealing are monitored through dynamic mechanical properties of an amorphous glassy polymer. These phenomena are investigated through dynamic mechanical testing that evaluates in-situ the evolution of the storage modulus with time during annealing and physical aging. Comparisons are made on samples with different thermal histories. The polymer characterized in this contribution is a new commercially available copolyester under the trade name of Tritan™. The results are discussed in context to different aging rates obtained from the various thermal treatments.
Influence of Ultrasonic Treatment in PP/CNT Composites Using Masterbatch Dilution Method
Multiwalled carbon nanotube (CNT) filled polypropylene (PP) composites of various concentrations were prepared by a twin screw extruder using direct compounding (DC) method without and with ultrasonic treatment. In addition, a masterbatch of 20 wt% PP/CNT composites were prepared without and with ultrasonic treatment and diluted to the same concentration as in the DC method without ultrasonic treatment. This is called the masterbatch dilution (MD) method. The rheological and electrical properties were investigated. The increased storage modulus and viscosity as well as the electrical conductivity indicates a better dispersion of CNT in PP matrix prepared by the MD method than by the DC method. The fractal dimension of CNTs, D, and the backbone fractal dimension, x, of the CNT network was determined by fitting the rheological data to the scaling model. The lower fractal dimension of CNT and higher backbone fractal dimension of CNT network in composites prepared by MD method compared with composites obtained by DC method indicates a better dispersion of CNT. Additionally, a lower value of D and a higher value of x as well as a higher storage modulus, viscosity and lower electrical percolation were achieved when the ultrasonic treatment at an amplitude of 13 ?m was applied in the MD method, indicating an advantage in use of the ultrasonic treatment in preparing the PP/CNT masterbatch. The macrodispersion was determined using optical microscopy to correlate the processing, properties and structure. It was shown that the MD method provided better dispersion of CNT in PP matrix than the DC method.
Ultrasonic Decrosslinking of Crosslinked High Density Polyethylene: Effect of Screw Design
In order to evaluate the performance of different screws designs, decrosslinking of the crosslinked high density polyethylene (XHDPE) is performed by means of an ultrasonic twin-screw extruder (TSE) with two screw configurations. Die pressure and ultrasonic power consumption during extrusion of XHDPE is recorded. Swelling test, scanning electron microscopy (SEM) and tensile test are used to investigate the structure and properties of the decrosslinked XHDPE. It is found that the screw configuration without kneading elements (decrosslinking screws) is more effective in decreasing the gel fraction and crosslink density of the decrosslinked XHDPE. The ultrasonic treatment significantly improves the processibilty of the decrosslinked XHDPE. The reason for the superior performance of this screw configuration for decrosslinking of XHDPE is explained by extrusion theory. The numerical calculation describes the effect of the residence time, the gel fraction and crosslink density of the initial polymer on the gel fraction and crosslink density of ultrasonically decrosslinked XHDPE. The mechanical performance of the decrosslinked XHDPE from TSE containing the decrosslinking screws is very close to those of the virgin XHDPE. The effect of the gel fraction and crosslink density on the morphology of the decrosslinked XHDPE is also identified.
Effect of Heater Surface Shape for Heat-Sealed Parts on Oriented Polypropylene/Cast Polypropylene (OPP/CPP) Film
In this study, oriented polypropylene/cast polypropylene (OPP/CPP) laminated films were heat sealed by various stainless mesh sheets in order to evaluating the effect of heat sealing bar shape on heat sealed properties. The heat sealed conditions were set at heat sealed time of 1.0 s with a pressure of 0.3 MPa at various heat sealed temperatures of 100 to 120 °C. The difference of higher order structure of these films was discussed on the basis of results of micro-Raman spectroscopy, DSC and peel test. From the result, it was found that peel strength were affected by the heat sealing bar surface shape. We can analyze the very small area and changes on the basis of the results of heat sealed part by using micro-Raman spectroscopy imaging.
Effects of Carbon Fiber Loading on the Conductive, Mechanical, EMI Shielding Effectiveness Properties of Microcellular Foams of PBT/Carbon Fiber Composites
This study investigated the carbon fiber loading on the mechanical/electrical conductivity/EMI shielding effectiveness properties of Polybutyele Terephthalate(PBT)/carbon fiber composites. The PBT/carbon fiber composites were compounded by twinscrew extruder as a master batch of 13 wt.% . Then composites were diluted into 1, 3, 5, 8, and 13wt% during the injection molding process. The results showed as the carbon fiber loading increased so is the tensile strength. It level off at the carbon fiber loading of 8wt. %. The conductivity test showed that as the carbon fiber loading increased so is the conductivity. And conductivity test were done at 3 different locations (surface, 0.3 mm under surface, and 1.5 mm under surface). For the different positions, the conductivity showed as the position is far from surface the conductivity increased. For the carbon fiber distribution, SEM results showed that there are more fibers on the PBT matrix when the location is far from sample surface. For the electromagnetic interference (EMI) shielding effectiveness(SE), the EMI SE for carbon fiber loading less than 13 wt% is almost zero. So the carbon fiber loading is increased to 20, 25, and 30 wt.% respectively. As the carbon fiber loading is increased from 20 ~ 30 wt%, so is the EMI SE value.
High Strain Rate Testing of Polymers for Impact Simulations
The increased use of polymeric materials in impact and high strain rate applications is motivating the use of impact simulations during design. Simulation of polymer impacts however requires difficult-to-measure stress-strain behavior at high strain rates. Complicating the measurement task further is the need to establish failure criteria associated with high strain rate deformations. Even when appropriate data is collected, appropriate high strain rate constitutive models need to be fit to the data before being incorporated into a simulation code. This article presents a testing and constitutive modeling process to achieve accurate impact simulations using polyether ether ketone (PEEK) as the example material. High and low strain rate data is presented over a large strain rate range. The resulting data and material model is used simulate a drop test which is then compared with an actual drop test data to validate the model.
The Study of Dynamic Behaviors and Optical Quality for Fisheye Lens Using Injection Compression Molding
Injection compression molding (ICM) process can bring a lot of advantages to enhance the product quality. Meanwhile, ICM also introduces more parameters increasing the complexity of molding. In this study, conventional injection molding (CIM) and ICM processes on the fisheye lens development through numerical simulation are compared. Results show that ICM process can provide better geometrical shape accuracy, and better optical properties with lower retardation and fringe order. Furthermore, we also examine various compression gap and compression speed effects on geometrical shape accuracy and optical quality. It shows that different compression gap and compression speed have no significant effect on geometrical shape accuracy control. However, under constant compression speed, if the compression gap is too large, optical property will become worse.
Troubleshooting Gear Pump Assisted Single-Screw Extrusion Processes
Gear pumps are often used in tandem with singlescrew extruders to increase rate, decrease resin consumption, improve process stability, decrease extruder discharge pressure, and decrease the extrudate temperature. When a process is unstable, it is often not obvious if the extruder is unstable and the gear pump is operating well, or the extruder is operating well and the gear pump operation is unstable. This paper will describe a few operations where gear pumps improved a process, how they are used in unstable processes, and approaches to troubleshooting lines using gear pumps.
An Innovative Food Packaging Design for Can Replacement: A Product Development Story at Printpack
This paper demonstrates an innovative approach on how to develop a new package design for food industry. Unlike traditional customer-oriented product development, this approach engaged our final consumers at the first stage, which helped us develop and confirm the ideas of this package design. Then, iterations of prototypes were made, tested, and modified to evolve into a viable solution for large-scale manufacturing. In addition, a comprehensive study on heat penetration during thermal processing was conducted to facilitate its commercialization by providing our customers with certain guidance on how to utilize this package design in an appropriate way.
Comparison of Mesh Partitioning Technique and Level-Set Method for Coextrusion Simulation
Multilayer flow is simulated in five different coextrusion dies using the mesh partitioning technique as well as by the level-set method. These simulations show that depending upon the layer structure in the die, one of the two techniques may be more suitable for the coextrusion simulation. In general, the layer structure predicted by the mesh partitioning technique is found to be more accurate than the corresponding predictions from the level-set method. Level-set method requires that the layers should be arranged in a sequential manner, which is not necessary if the mesh partitioning technique is used. The mesh partitioning technique cannot simulate a multilayer flow if an interface between the polymer layers splits into two interfaces, or if two interfaces, which start separately, merge into a single interface in the die.
Dynamics and Hysteresis in Capillary Rheometry
Several sets of experiments were conducted to investigate the dynamics and hysteresis in capillary rheometry. Experimental data indicate that the imposed flow rate history can vary the apparent viscosity by a factor of 10, a magnitude as significant as a change between the minimum and maximum recommended processing temperatures. Contributing factors that were investigated and found insignificant included the capillary length:diameter ratio, viscous heating of the polymer melt, rheometer transmission, and instrumentation. Other contributing factors to be analyzed further include polymer compressibility and viscoelasticity.
Structure-Property Relationship of Biaxially Oriented Polyethylene (BOPE) Films Made via Double Bubble Film Fabrication Process
Mechanical and optical properties were compared between a double bubble biaxially oriented polyethylene (BOPE) film and a blown film. The double bubble film exhibited higher modulus, higher tensile strength, better optical properties, but lower tear strength. Morphological differences between the double bubble film and the blown film were investigated with differential scanning calorimetry (DSC), wide angle X-ray scattering (WAXS) and small angle X-ray scattering (SAXS). It was found that in the double bubble process the large crystals were broken up into smaller fibrillar crystals with a larger long spacing. C-axis of the fibrillar crystals preferentially lay in the plane of machine direction and cross direction (MD-CD). The lower tear strength for double bubble films has been proposed to be due to the fibrillar crystal morphology. A sample with a larger low temperature melting peak showed a better tear strength with a similar stiffness.
New Effect Pigment Preparations – New Products Are Driving the Efficiency in Masterbatch Production and Enable Plastic Processors to Enter New Markets
Effect Pigments are widely used in plastic materials to achieve gold, silver or pearlescent colours. The main aspect is to achieve a differentiation and to upgrade the value of the end user product. The first part of the presentation describes the production, processing, optical aspects and the special features of aluminium-, gold bronze-, and pearlescentpigments. This will be followed by the introduction of new effect pigments such as the platinum dollar aluminium pigments which enable spray coated like" silver effects in mass coloured plastics. In addition a new generation of pearl pigment on the basis of artificial glass substrates will be highlighted. Today's key success factor for pigment manufacturers is the ability to provide easy to use product forms with high and consistent qualities such as Eckart's Micropellets. These products enable significant cost reductions compared to regular pigment powders or pastes in masterbatch production as they enable higher production speeds and easy dispersion. They also significantly reduce cleaning times in production. Finally a short outline on use of aluminium pigments to improve insulation properties of plastics will be given. Energy saving is Megatrend especially at today's crude oil prices. Aluminium pigments reflect IR light and therefore can be used to improve the insulation and help to keep the heat inside (winter) or outside (summer)."
Thermoforming of Biodegradable Sheets Obtained from a Thermoplastic Starch and Polylactic Acid Blend
This paper describes the blending and the thermoforming performance of a thermoplastic starch (TPS) and polylactic acid (PLA) compound. A twin screw extruder (TSE) was used for corn starch plasticizing and blending with the plasticized PLA. A single screw extruder was used to melt, functionalize and feed the plasticized PLA into the TSE. Extruded pellets were used to make sheets through extrusion calendering, which were ultimately thermoformed in a parallelepiped shape. Thermoformability of the sheets was evaluated by the area ratio, the maximum uniaxial deformation, and the thickness measurement in the machine direction (MD) and transversal direction (TD). The operating window was defined using DMA techniques. The compound showed good thermoformability characteristics.
Experimental Study of Fiber Attrition within a Long Fiber Glass-Reinforced PP under Controlled Conditions
The effect of the process/material conditions over the fiber damage was studied. In this experimental study, a controlled shear flow was generated by using a Couette device. Two Polypropylene (PP) resins with 30 and 40 % glass fiber concentration by weight, respectively, were used. The measurement of the fiber length distribution was done using the STAMAXTAT SABIC® method and it was observed that the melt temperature, rotational speed, residence time and fiber concentration greatly affect the fiber length distribution. Furthermore, comparing the damage occurred during the injection molding and purged with those generated in a Couette device, it was found that an additional reduction in fiber length occurs during injection molding because the fibers are forced to pass through narrow channels.
Pressure-Rise Tests for Detecting Particles in Polymers
A pressure-rise test method was developed and qualified to detect undesired particles in polymers. The feasibility of this method was confirmed by a polymer with a large number of particles, and the key parameters for defining pressure-rise were characterized as the initial pressure, initial slope and pressure-rise per hour. The theoretical simulations of initial pressure and pressure-rise due to screen blockage were demonstrated and validated with experimental data. This test method is useful for resin quality assurance, screen life determination, and new formulation development of polymers for many extrusion processes.
Device for Measuring Microscale Viscosity in a Self-Aligned Microgap
A novel rheometer for measuring shear viscosity in a self-aligned microgap was developed. Drag flow of simple linear motion was created inside two self-aligned parallel plates. A ball-bearing contact between the loading and moving parts was employed to facilitate self-alignment so that gap thickness smaller than those in standard rheometers can be obtained. Analysis based on the lubrication approximation indicated that a self-balancing liquid film can be generated between the two plates during rheological measurement. The new device was successfully used to measure the viscosity of selected fluids.
Crystallization Characteristic and Heat Seal Properties of Biodegradable Films
Biodegradable polymer film was prepared from poly(lactic acid)/thermoplastic starch (PLA/TPS) blend by cast film process at 0, 5 and 10 wt% of TPS. The PLA and PLA/TPS blend films were heat sealed at heat sealed temperature of 90 and 100 °C. The heat seal time was varied from 0.5 to 2.0 s with a pressure of 0.2 MPa. The effect of heat sealed conditions on heat seal properties of PLA and PLA/TPS films was investigated. Heat sealed strength of PLA/TPS blend films decreased when increasing the heat sealed times. PLA/TPS heat sealed films exhibited greater crystallinity than the PLA heat sealed film, which characterized by crystallization kinetic study.
Acoustic Process Analysis of Rubber Compounding
Properties of rubber compounds differ batch-wise. This can lead to waste and, thus, it is desirable to reduce these variations. One reason for quality variations of rubber compounds is the discontinuous way of compounding in internal mixers. Mixing effects make it difficult to adjust the process parameters of internal mixers in order to guarantee constant qualities. Experienced operators of internal mixers observe that characteristic noises during the mixing process can be correlated with the state of mixing. Thus, a project has been started to use these mixing noises for the development of a control system for internal mixers, which is able to characterize the state of the rubber compound. First, a measurement system has been implemented which allows the online visualization and recording of the mixing noise. It is systematically analyzed how the mixing noise is related to the state of mixing and the resulting elastomeric properties. The results show a correlation between filler incorporation and the characteristic sounds.
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