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
Supercritical Carbon Dioxide Assisted Polymer Blending in Twin-Screw Extrusion: Relations between Morphology Evolution and Mechanical Properties
M.D. Elkovitch, L.J. Lee, D.L. Tomasko, May 2000
Supercritical carbon dioxide (scCO2) was added during compounding of polystyrene and poly(methyl methacrylate) (PMMA) and the resulting morphology development was observed. The compounding took place in a twin screw extruder. Viscosity reduction of PMMA and polystyrene were measured using a slit die rheometer attached to the twin screw extruder. Carbon dioxide was added at 0.5, 1.0, 2.0 and 3.0 wt.% based on polymer melt flow rates. A viscosity reduction of up to 80% was seen with PMMA and up to 70% with polystyrene. A sharp decrease in the size of the minor (dispersed) phase was observed near the injection point of CO2. However, further compounding led to coalescence of the dispersed phase. De-mixing of the dispersed phase occurred upon CO2 venting. The resulting morphology was similar to that without the addition of CO2. Adding small amounts of fillers (e.g. carbon black, calcium carbonate, or nano-clay particles) tended to slow down the de-mixing of the polymer blend system when the CO2 was released. The comparison of morphology and mechanical properties for various polymer blends with and without CO2 considerations will be reported.
Effect of Polyolefin Structure on Grafting of Maleic Anhydride
A.V. Machado, J.A. Covas, M. van Duin, May 2000
In this study the effect of polyolefin composition, i.e. ethene/propene ratio, on MA grafting and branching/crosslinking or degradation was investigated both in the melt and solution. The MA grafting content for PE and EPM was similar, but low for polymers with a high propene content. An increase of the ethene content results in a transition from degradation to branching/crosslinking.
Fundamentals of Polymer Process Control
David O. Kazmer, May 2000
Process control has been recognized as an important means of improving the performance and consistency of thermoplastic parts. However, no single control strategy or system design has been universally accepted, and the manufacturing systems continue to produce defective components during production. This paper provides an overview strategies in polymer process control, and discusses some of the difficulties posed by the complex and distributed processes. Objectives for 'intelligent' process control are presented. Finally, the potential benefits of integating product and process design are demonstrated.
An Overview of Optical Brighteners for Copolyester Resin Extrusion Paper Coating Applications
Johnny F. Suthers, May 2000
Several topics will be covered in the Take Home Information" to aid the reader in a better understanding of optical brighteners use in extrusion coating applications. They include: • What is an optical brightener? • What is the mechanism? • How to formulate with optical brighteners in an extrusion coating grade copolyester resin. "
On-Line Monitoring of Free Radical Grafting in a Model Twin Screw Extruder
Kasama Jarukumjorn, Kyonsuku Min, May 2000
The on-line monitoring system of Raman spectroscopy was developed to monitor the grafting identification and level of grafting of glycidyl methacrylate (GMA) onto low density polyethylene (LDPE). The reactive extrusion and melting behavior of GMA and LDPE was monitored by a fiber optic probe through the glass windows mounted on the model non-intermeshing counter rotating twin screw extruder. Monitoring concentration of GMA along the screw extruder was carried out to determine the reaction level.
The Effect of Varying Injection Molding Conditions on Cavity Pressure
Sonja Macfarlane, Rickey Dubay, May 2000
Obtaining high quality parts in injection molding requires the understanding of the many interactions that exist between the molding parameters. Cavity pressure and part mass are good indicators for maintaining high product quality and obtaining good machine control performance. The effect on cavity pressure and part mass was investigated by varying the molding conditions using a two-phase screw-plunger injection molding machine. The molding parameters that were perturbed included the barrel temperature, injection velocity and hold pressure. The results provided a good understanding of the effect of changing the molding conditions on cavity pressure and part mass for a two-phase injection machine.
Surface Analysis of Polymeric Materials: Roughness Exponent
Edgar Reyes, Carlos Guerrero, Moisés Hinojosa, Virgilio González, May 2000
The self-affine behavior of fracture surfaces of polypropylene, PP, and polystyrene, PS, were analyzed applying the variable bandwidth method to the height profiles generated with an atomic force microscope, AFM. The roughness exponent, ?, obtained with this method was 0.788-0.008 for PP samples and V=0.81-0.023 for PS. These results are in very good agreement with the claimed universal value of V=0.8 reported in the literature for other non-polymeric materials. Melted PP was crystallized following two different cooling rates and the crystalline surfaces were also analyzed, obtaining similar roughness exponents. This fact probably means that, for this case, the self-affine behavior could be independent of the crystallization rate.
Morphology and Thermal Loading in Laser Welding of Thermoplastics
Jörg Vetter, Fabienne Duriau-Montagne, Gottfried W. Ehrenstein, Dirk Hänsch, May 2000
Laser welding, an innovative, flexible technology for joining of thermoplastics, now starts to make its way from scientific laboratories into industrial series production. There has been intense research on weld strength de-pending on polymer, butt design, fillers and absorption behavior. Nevertheless, a considerable lack of knowledge concerning the fundamental relationship between the process and its influence on thermal loading of the weld plane and resulting morphology still exists. Actual results of laser transmission welding experiments - including thermal and microscopic analysis of the weld plane - could contribute to a better understanding of the process itself and to success in practical applications.
Temperature Calculation of Plastic Gears
Peter Faatz, Gottfried W. Ehrenstein, May 2000
Plastic cog-wheels may run completely without lubricants. When using plastic cog-wheels a service life dependent on the application is to be guaranteed. Because the service life of the cog-wheel is limited by the wear of the flank of the cog-wheel, the specification of the wear is required for dimensioning plastic gears. Caused by frictional processes at the surface of the cog, heat is produced. Like the mechanical properties of plastics, the wear also strongly depends on temperature. Therefore, it is necessary to determine the temperature of the cog. Plastic gears are tested and the cog temperature is measured by means of a thermal camera. Polyacetal cogwheels with a modulus of 1 mm are examined. It will be shown, that the cog temperature can be calculated on the basis of heat balances with a known coefficient of friction.
On-Line Material Characterization during Extrusion of Recyclates
Thomas Schubert, Gottfried W. Ehrenstein, May 2000
Unknown properties of recycles are the problem in the field of recycling thermoplastics. The off-line determination of selected properties (basicpolymer, colour and mechanical properties) is not sufficient to qualify recyclates. Important for the characterization is an almost complete knowledge of the material properties when producing recyclates that are supposed to be competitive as construction materials. Therefore the implementation of tools for the detection and assurance of material properties on-line during extrusion is a promising conception. This presentation shows and discusses the basic ideas of on-line property determination, the achieved results of material determination, and the resulting process control.
Sorption Properties of PAN/Chitosan Composite Fiber
Byung G. Min, Chang-Whan Kim, Sang-Chul Lee, May 2000
Composite fiber of PAN and chitosan was obtained by hydration-melt spinning process. The fiber showed a fibrillar structure which can be converted easily into pulp-like structure by beating. PAN/chitosan pulp showed much higher amount of acid dye uptake than chitosan powder or activated carbon which is used for the color removal from the waste water of dyeing industry. This better sorption for the composite fiber is considered to result from the relatively large surface area due to its pulp-like shape.
Opportunities for Reinforced Plastics in Automotive Applications
Gilbert B. Chapman II, Donald A. Vesey, May 2000
This paper presents the motivation for using fiber-reinforced plastics in automotive applications and the advantages and limitations concomitant therewith. Applications of fiber-reinforced plastic components in current and future vehicles have been selected for discussion to provide examples of how these materials can be used to support the drive toward the continuous improvements in performance, energy-efficiency, manufacturing cost, and environmental conservation.
Kinetics of Isothermal Crystallization of Syndiotactic Polypropylene: Avrami, Tobin and Malkin Analyses
Pitt Supaphol, May 2000
Various macrokinetic models; namely the Avrami, Tobin, and Malkin macrokinetic models, were applied to describe the kinetics of isothermal crystallization from the melt state of syndiotactic polypropylene (sPP). Data analysis was carried out using a direct data-fitting method, in which the experimental data were directly fitted to each macrokinetic model using a non-linear multi-variable regression program. The results suggested that the experimental data can be best described by the Avrami model, followed by the Malkin and Tobin models, respectively.
Blends of Ethylene-Styrene Interpolymers
H.Y. Chen, W. Cheung, S.P. Chum, A. Hiltner, E. Baer, May 2000
Binary blends of ethylene-styrene interpolymers (ESIs) were studied over a range of styrene concentration. The miscibility composition map was determined primarily from the morphology as imaged with AFM, and when possible confirmed by analysis of the Tg behavior using DMTA and DSC. A difference in styrene content of about 8 wt% marked a transition from miscible to immiscible behavior for amorphous ESIs. The miscibility criterion extended to blends of semicrystalline ESIs. It was also found that molecular weight affects the observed domain morphology.
Evaluation of the Interfacial Tension between a Low Molar Mass Liquid Crystal and Solid Polymers
Renato Norio Shimizu, Nicole Raymonde Demarquette, May 2000
The surface tension of a low molar mass liquid crystal (LMMLC) was measured as a function of temperature (56.0°C to 79.5°C), using the pendant drop method. The surface tension presented a behavior described by two distinct curves for the different phases (isotropic and nematic). Also the contact angles of LMMLC on plates of PS and of a liquid crystal polymer were measured at different temperatures (from 62.4°C to 89.0°C). The angle presented a discontinuity nearby the nematic to isotropic transition temperature when measured on PS, whereas it remained constant on the LCP. The interfacial tension between the LMMLC and the polymers were estimated.
Influence of Process Parameters on the Phenomenon of Stress Cracking during Hot Plate Welding
H. Potente, J. Schnieders, May 2000
Heating experiments were carried out in order to investigate the significance of the different process parameters on susceptibility to stress cracking. With the help of wetting tests, different crack lengths were generated in the heated sheet and subsequently compared with the various process parameters by means of multiple regression analysis. Another focal point is the estimation of the normal stress difference (?x – ?y) at each point of the specimen by means of 2D photoelastic stress analysis. In both cases the marked correlations between the process parameters and the phenomenon of stress cracking are recognisable, and the results can be used to minimise stress cracking.
Structure-Property Relationship in Poly(phenylene sulfide)(PPS)/Polyethylene Blends-Effect of Metallocene Catalyzed Polyethylene
Bo Sun Lee, Byoung Chul Chun, May 2000
In this investigation, blends of poly(phenylene sulfide)(PPS) with two types of polyethylene such as linear low density polyethylene(LLDPE) and metallocene catalyzed polyethylene(MPE) were prepared by melt blending. First, rheological behavior was determined using a capillary rheometer. The melt viscosity of PPS/LLDPE and PPS/MPE blends was low when PE was a dispersed phase. However, when PPS was a dispersed phase, increased melt viscosity was observed. This tendency was similarly observed in mechanical properties such as percent strain at break and notched Izod impact strength. Also, the mechanical behavior of PPS/LLDPE and PPS/MPE blends showed negative deviation from the rule of mixtures relationship when PE was a dispersed phase. But the negative deviation for PPS/MPE blend was less than that for PPS/LLDPE blend. Also, the dispersed phase morphology was analyzed using scanning electron microscope(SEM).
Factors Influencing the Sorting Efficiency of Commingled Post-Consumer Bottles Using an Automated Sorting System
Robert Dvorak, Edward Kosior, Pio Iovenitti, Syed Masood, May 2000
This paper examines the effects of high throughput rates in a spectroscopic bottle sorting system, on the purity of PET and HDPE end-products as well as other key factors such as an increase in material loss, decrease in % material yield and the need for extra manual sorting staff at higher throughput rates. Increasing the throughput rate of a wide belt bottle sorting system from 1,000 kg/hr to 2,000 kg/hr decreased the purity of HDPE by 17% and that of PET by 2%. Material loss had more then doubled for PET from 12% to 32% and for HDPE increased from 8% to 9%. The end-product yields for HDPE and PET had decreased by 3% and 8% respectively. One of the key improvements to the sorting operation was the development of an automated sensor cleaning system, which uses an automated film rotating mechanism.
The Development of Weld Line Strength in Injection-Molded Poly(methyl methacrylate)
Anne K. O’Brien-Soucy, Carol M.F. Barry, Ross G. Stacer, May 2000
An experimental investigation has been conducted to evaluate various approaches to modeling weld line development during the injection molding of amorphous plastics. A series of poly(methyl methacrylates) (PMMA) representing several different molecular weights were molded both with and without weld lines over a range of processing parameters. Results were compared with the predictions of several previously proposed isothermal models. These were found to be insufficient to explain all the phenomena observed. A non-isothermal model is developed to provide an improved predictive capability. This non-isothermal approach combined with fracture mechanics leads to a new physical interpretation of weld line morphology and its contribution to the resultant strength of the welded part.
Effect of Heater Band Orientation on Cavity to Cavity Variations
Adam J. Shuttleworth, Ramsey J. Haylett, May 2000
This paper presents the results of a study that shows that heater band orientation on a machine nozzle can cause an imbalance of over 5% in multi-cavity molds. The amount of imbalance is material dependant. The imbalance is most directly related a material's temperature and viscosity constants.
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