SPE Library
The SPE Library contains thousands of papers, presentations, journal briefs and recorded webinars from the best minds in the Plastics Industry. Spanning almost two decades, this collection of published research and development work in polymer science and plastics technology is a wealth of knowledge and information for anyone involved in plastics.
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Conference Proceedings
Heat Transfer in Extruder Screws
Stephen J. Derezinski, May 2000
In the study and modeling of the resin temperature in extruder channels, the screw is commonly assumed adiabatic. However, the resin begins as a cold solid and is melted and heated as it flows, which requires that the screw also be cold at the entrance and hot at the exit. Heat must, therefore, be conducted in the screw metal from the hot end of the screw to the cold end, which requires heat transfer with the melt. Also, the heat capacity, especially of larger extruders, can require significant time to attain steady-state operation. A model of transient heat conduction in the screw coupled to heat transfer with the resin feed, melting, and pumping is used to investigate these two phenomena.
Preventing Sink Marks of Injection Molded Parts Using CAE Analysis
Shijun Ni, May 2000
Sink marks on injection molded parts were caused mainly by part geometric design, mold design, and molding process conditions. This paper describes the dominant factors causing sink marks on injection molded part that can be predicted using CAE injection molding simulation programs. Sink marks on injection molded parts should be prevented for a new part design or solved for an existing one based on simulation results. In this study, a Bearing Bur, Laser printer part was chosen to illustrate how sink mark problems were solved using a commercial available C-MOLD® simulation program. The predicted sink marks of the Bearing Bur were compared to the measurements of an actual production part. Predictions were in good agreement with the actual injection molded part.
Apparent Viscosity Measurements for Determining Injection Molding Dimensional Variations
Gary L. Freiberg, May 2000
Injection molders presently use the Apparent Viscosity Curve" to determine the optimum fill time for a particular mold. Once the fill time has been determined the Viscosity Curve is set aside and the goal of the molder is to maintain the fill time. The motivation for my work is not only to determine fill time but also to quantify the melt viscosity using an injection molding machine/mold combination. The ability to determine the melt viscosity would assist the molder with "root cause" analysis when evaluating small dimensional shifts. The study will focus on determining if the derived viscosity using traditional rheological equations is of value when compared to dimensional or cosmetic changes."
A Transparent Barrel for Study of Reciprocating Screw Injection Molding
Furong Gao, Zhiming Jin, Xi Chen, May 2000
A transparent barrel system has been developed to assist in the understanding of polymer behavior in a reciprocating screw injection molding machine. This system allows the dynamic status of the polymer inside the injection barrel to be conveniently visualized though photography and video recording, and the corresponding material conditions can be measured via a computerized data acquisition system. Effects of different processing conditions on the melting behavior are analyzed. This system can not only assist in the understanding of the process but also can be used to quantitatively verify the modeling and optimization of injection molding system.
An On-Line Measurement Scheme of Melt-Front-Area during Injection Filling via a Soft-Sensor Implementation
Xi Chen, Furong Gao, May 2000
A constant melt-front velocity during the filling of an injection mold cavity is commonly believed to bring about more uniform part quality. To maintain a constant melt-front velocity, injection velocity can be set proportional to the melt-front-area which is, however, not directly measurable. An on-line soft-sensor scheme is developed through neural network to correlate on-line measurable process variables to the melt-front-area. Simulations indicate that the soft-sensor developed for the melt-front-area works reasonably well for some selected molds.
Improvement of the Molded Part Quality-Optimization of the Plastification Unit
S. Boelinger, W. Michaeli, May 2000
The three-zone plastification screws traditionally used in the injection molding process are nowadays limited in their efficiency. Reasons are increasing demands on the quality of the molded part and on the machine technology which is more and more adapted to the different process groups like packaging or optical parts. Therefore different types of screw geometry, e.g. barrier screws or multi-threaded screws, are used to investigate the influence of the dosing parameters and the screw geometry on the melting capacity and the homogeneity of the melt .
Carbon Dioxide Extrusion Foaming of Engineering Thermoplastics
Martin Gale, May 2000
Many engineering thermoplastics require extrusion temperatures which are too high for foaming with chemical blowing agents. Carbon dioxide foaming by direct super critical fluid injection has no such restrictions as well as offering economic benefits. This study describes preliminary work on a laboratory scale extrusion line using retrofitted parts to produce foams from a number of engineering polymers. Results of an evaluation of a very simple low cost method for measuring melt strength (an important polymer property with regard to foaming) is also included.
Effect of Nanosilica on Properties of Segmented Polyurethanes
Zoran S. Petrovi, Young-Jin Cho, Ivan Javni, Wei Zhang, May 2000
Thermoplastic polyurethane elastomers having soft segment concentration (SSC) of 50% and 70% were synthesized in the presence of 12 nm silica nanoparticles. The concentration of nanosilica was varied from 0% to 30% in both series. Nanosilica had not significant effect on glass transition of the soft segment but it increased tensile strength and particularly elongation at break. Tear strength of the series with 70% SSC was not affected by the presence of nanosilica while initial decrease was observed in the series with 50% SSC.
Characterization of Biaxial Orientation in Polyolefin Films
A. Ajj, K.C. Cole, May 2000
Among the most widely used orientation processes are those involving films; they include both film blowing (with a low level of orientation) and biaxial orientation or tentering (with a high level of orientation). Polyolefins (polyethylene, polypropylene, polystyrene, and their copolymers) represent a significant proportion of the polymers commonly used in these processes. The knowledge of the orientation developed in these films is critical for establishing the process conditions and the final properties of the films. In this study, we investigate the biaxial orientation developed in blown and biaxially oriented polyethylene films using Fourier transform infrared (FTIR) spectroscopy and birefringence. Biaxial orientation factors are determined for both crystalline and amorphous phases and discussed in relation with process conditions.
Measuring the Low Frequency Linear Viscoelastic Properties of Polymer Melts: Trials with PDMS Using Sphere-Plane Squeeze Flow and Interferometry
Edwin C. Cua, Montgomery T. Shaw, May 2000
The problem of measuring the linear viscoelastic (LVE) properties of polymers at low frequencies is a long-standing one, especially for polyolefins with broad relaxation times and small time-temperature shift factors. A squeeze flow apparatus utilizing Newton's interference rings has been devised to measure minute strains at very low stresses with a minimum resolution of ¼ wavelength of light. Its simplicity allows several samples to be run simultaneously under vacuum. This arrangment minimizes degradation, manhours and cost, all critical considerations for long experiments. The design and preliminary results for PDMS as measured by a prototype of the instrument will be discussed.
New Polypropylene for Differentiated Blown Films
W.D. Hoenig, C.P. Bosnyak, K. Sehanobish, W. Van Volkenburgh, C. Ruiz, L..M. Tau, May 2000
New polypropylene resins have been developed which allow for the commercialization of novel, air-quenched blown films. The new resins have been developed using molecular design principles and provide significantly enhanced properties. Key performance properties include stiffness, seal strength, and higher service temperature for many applications as well as flexibility and toughness for other applications. This new breadth in product offerings and performance ranges provides significant new opportunities for PP resins in blown films. This paper will highlight properties and processability of the new resins.
Physical Model of Polymer Pellets Melting in Co-Rotating Twin-Screw Extrusion
Zhu Linjie, Geng Xiaozheng, May 2000
The melting of polymer in co-rotating twin-screw extruder depends not only on screw configurations and operational conditions, but on the properties of the polymer as well. The melting progressing is too various to be described by single melting model. Only in the past few years (1-9), some attention has been paid to the research of polymer melting in co-rotating twin-screw extrusion. In present study, based on experimental results, the conception of melting sub-stage was defined to describe the complex polymer melting progressing in co-rotating twin-screw extrusion. Ten melting sub-stages were concluded and defined. It was found that the complicate polymer melting progressing can be modeled by combining some of these ten melting sub-stages. It showed that the definition of melting sub-stages would provide an important way to the research of polymer melting in twin-screw extrusion.
Numerical Analysis on the Melt Conveying Properties of Wave Screw Element in Intermeshing Counter Rotating Twin-Screw Extruder
Zhou Fuping, Geng Xiaozheng, May 2000
In this paper, one new kind screw element, wave screw element in intermeshing counter-rotating twin screw extruder, is designed. Three-dimensional Non-Newtonian model is established to investigate the melt conveying properties of this new screw elements. The model consists of all the gaps between the screws and the barrel such as the side gap, the calender gap, the flight gap, and the tetrahedron gap, which is in accordance with the true extrusion process. With the finite element software ANSYS, velocity, pressure and viscosity field are obtained respectively. Experiments are used to verify the results of simulation. It shows that the calculated results such as output is nearly the same as the experimental results.
Effect of Water Sorption on Mechanical Properties of Fiber Reinforced Dental Resin
A. Prasad, A. Karmaker, May 2000
Composites from different glass fibers reinforced in dimethacrylate based dental resins were prepared for flexural tests in accordance with ISO 10477. Tests were conducted on both dry specimens and on specimens stored in water for 7 days at 37°C. Depending on type and amount of fibers, the strengths were found to decrease from moderate to minor. Loss of strengths correlated with the constituents of fibers.
Wasteless Distribution Medium: A New Development for the Resin Infusion Process
T. Wassenberg, W. Michaeli, May 2000
The typical resin infusion processes like SCRIMP (Seemann Composite Resin Infusion Molding Process) require the use of a distribution medium or system to increase the impregnation speed in large parts. Normally, a substantial amount of surplus resin remains in the distribution medium and has to be disposed with the medium or remains on the part as resin rich domains. A new patented type of resin infusion process is presented, which does not produce any surplus resin waste.
Welding of Polymers Using a Diode Laser
J. Schulz, E. Haberstroh, May 2000
Welding polymers by using a diode laser is a fairly new joining method. The first industrial application is the joining of automotive keys. The process advantages are precisely defined heated zones, minimized melt flow and the realization of three dimensional weld lines. At the IKV a process analysis has been done and the influence of pigments on the weld strength has been investigated. It is possible to weld glass fibre reinforced polyamide, which is transparent for the laser beam, but appears black to the human eye.
Elastomer Matrix Composites for Impact-Resistant Parts
M. Koschmieder, W. Michaeli, May 2000
The impact resistance and energy absorption capacity of most thermoset matrix composites is rather low. Use of elastomer matrix can improve the impact behavior, allowing the design of impact-resistant parts (e.g. crash elements). By using low-viscosity elastomer systems, composite parts can be produced on a commercial filament winding machine. Mechanical tests of filament wound samples show that elastomer matrix composites exhibit superior energy absorption behavior and offer a high optimization potential for impact-loaded composite parts.
Morphology/Property Relationships in Thermoplastic Starch/Poly(hydroxy ester ether) Biodegradable Blends
P.S. Walia, J.W. Lawton, R.L. Shogren, F.C. Felker, May 2000
The effect of moisture level during processing on the mechanical properties of biodegradable blends of thermoplastic starch and poly (hydroxy ester ether) (PHEE) was studied. The morphology of the blends changed with the moisture content of starch. The dispersed phase was significantly deformed under high moisture conditions, leading to fibrillar and laminar types of morphologies at 50-80% starch level. A low moisture level produced a more dispersed morphology. Improved tensile properties were observed for the blends processed at high moisture levels due to the presence of elongated morphologies.
Mechanical Properties of Starch Filled Poly(hydroxy ester ether) Biodegradable Composites
S. St. Lawrence, J.L. Willett, C.J. Carriere, May 2000
The mechanical properties of starch filled biodegradable composites have been investigated. The strength was found to be independent of the filler content below 10 vol% and above approximately 30 vol%. This behavior is due to the failure mechanism operating in these composites. The matrix, poly(hydroxy ester ether) (PHEE), adheres well to starch and as a result the granules do not dewet during deformation. Instead the composites behave as a quasi-homogeneous material with increased brittleness as the filler content increases. The deformation mechanism was investigated by acoustic emission analysis and by a post-mortem examination of the fracture surfaces.
Mold-Making Apprenticeship Program in Georgia
William T. Thielemann, May 2000
This paper will trace the development of the Mold-Making Apprenticeship Program in Georgia's technical institutes, developed to support the plastics industry within the state. It will explain why the program was developed, how it was developed, the content of the program and the results to date. The purpose of the poster presentation is to explain the process and outline the program with the goal of assisting other states with similar programs and ultimately addressing the shortage of trained and available mold-makers. The poster presentation will include three sections: industry growth and potential, team process and program outline.
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