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
Reactive Extrusion of Polyolefin Blends
Claudia M.C. Bonelli, John M. Pochan, T.H. Mourey, Eloisa B. Mano, Charles L. Beatty, May 2000
The incompatibility of polypropylene (PP) and high density polyethylene (HDPE) is a source of industrial problems for recycling post-consumer polyolefins. Blends of PP and HDPE with peroxide and 3 vector fluid additives have been prepared in a co-rotating reactive twin-screw extruder. Compatibilization has been examined by stress-strain tests, impact tests and scanning electron microscopy (SEM). Molecular weight of the blends has been evaluated by gel permeation chromatography (GPC). An increase in elongation at break and impact resistance of some reactive blends compared to the mechanical blend was observed, with some links between the phases, as revealed by SEM.
Crushed Recycled Glass as a Stiffening Agent for HDPE Compared to Traditional Plastic Lumber Fillers
N.L.H oekstra, B.P. Duffey, S.H. Dillman, May 2000
bstract The objective of this study was to determine the flexural, impact, and tensile properties of a compound of crushed recycled glass, HDPE, and coupling agent using a two-level, three-factor designed experiment. This study determined that glass content, sieve size, and coupling agent all have a significant effect on the mechanical properties. The use of recycled crushed glass was found to increase the flexural modulus, but not as efficiently as calcium carbonate, wood flour, and fiberglass. Additionally, crushed glass improved the impact strength but decreased the tensile strength. It was found that smaller glass particle size performed better and the use of coupling agent decreased all mechanical properties.
Predicting Creep in Bottle Design
Ivan McCracken, May 2000
Experimental creep is data collected to drive an FEA program, ultimately used to predict bottle deformation caused by an internal pressure. The results indicate that it is possible to predict bottle deformation using existing creep data, but it is a highly manual process. The FEA program is beneficial in determining stresses caused by internal pressures, which can then be used to calculate deformations. True deformations can be calculated for segments of a bottle using FEA, but a new approach has been suggested, which will allow the FEA program to calculate the deformations along the entire sidewall of the bottle.
A Study of the Tensile Creep Behavior of Wood Flour Filled HDPE in Aqueous Mediums
John Raybuck, Daniel Heuer, May 2000
Wood flour filled polyethylene can be used as a replacement for conventional lumber in the waterfront structure industry. The effect of large amounts of moisture and submersion in fresh and salt water on the long term mechanical properties of these materials is important to understand. This study will examine the tensile creep behavior of wood flour filled high density polyethylene in air, fresh lake water, and salt water. An apparatus for aqueous tensile creep testing has been designed and built, and will be used to gather data for this study.
Modeling Gate Freeze in Hot Runners Using CAE
James J. Chiamardas, May 2000
When using computer flow simulation software to predict gate freeze time in hot runners it is hard to know how to correctly model the hot drop tip to accurately correlate the gate freeze time. This study will attempt to use computer flow simulation to correlate the gate freeze time of hot runners predicted by the simulation to actual gate freeze times. This will be done by changing a model to make the gate freeze prediction match an actual molded part, and observing how these changes affect the rest of the model.
An in Vitro Study of the Mechanical Property Loss of Poly(L-Lactic Acid), PLLA, Fibers during the Hydrolysis in Tissue Engineering Applications
Stacey L. Russell, Stephen P. McCarthy, Aldo M. Crugnola, May 2000
Tissue Engineering is the use of polymer scaffolds to grow tissue cells in vitro and then implant them. The polymer is designed to degrade as the cells grow into functional tissue in vivo. These scaffolds must be porous, strong, flexible, and ultimately degrade into harmless biomasses. The polymer scaffold is usually a natural or synthetic polymer in a fiber, foam, or fabric form. Synthetic polymers are preferred due to their easily tailored properties. For specialized tissues such as arteries, the scaffold fabric is formed into a tube. While the cells are being developed prior to implantation, nutrients are pumped through the tube. The engineered artery is ready to be implanted when it has acclimated itself to blood-pumping pressures. Other engineered tissues include heart, liver, bone, cartilage, nerves, and skin.
P20 and Beyond: Mold Steel for New Challenges
Nick Cerwin, May 2000
The mold steel designated as P20 has a long history of successful service in the plastics molding industry. The characteristics of this steel that have established it as the grade of choice among molders and moldmakers is reviewed as well as recent variations such as P20 Hi-Hard and P20 Premium (double melted) that offer advantages for some molding applications. Alternate grades of mold steel offering distinctly different characteristics from P20 are increasingly employed in specialized applications. Grades such as Long-Run mold steel, molybdenum modified 420 Stainless Steel, and age-hardening grades RA40 and Mar-X will be reviewed for a clearer understanding of their appropriate roles in plastics molding.
Process and Tooling Factors Affecting Sink Marks for Amorphous and Crystalline Resins
Dan Tursi, S.P. Bistany, May 2000
A plaque tool was built to facilitate changing rib features that include rib-to-wall (R/W) ratio, proximity to the gate, orientation with respect to flow, rib-base radius, and tool steel type. Gate type was also studied along with several process conditions using crystalline and amorphous resins. A Screening study was performed to determine the most influential factors affecting sink and followed by a Response Surface study to better define the relationships. A profilometer was used to measure sink depth. Optical microscopy and DSC were used to observed crystallization and molecular orientation differences between plaques exhibiting high and low degrees of sink. Low molding temperatures, high dwell times and high hold pressures helped reduce sink depth as did positioning ribs closer to the gate and perpendicular to the flow direction. Using a Beryllium Copper mold material also reduced sink while increasing rib-base radius significantly increased sink.
Melting Phenomena and Mechanism in Polymer Processing Equipment
Costas G. Gogos, Myung Ho Kim, May 2000
The research work presented here examines the heating and melting phenomena taking place, when individual polymer particulates or compacted polymer particulate systems are subjected to stresses which force them to deform and flow. The heating/ melting behavior in compression experiments of single polymer cylinders and in co-rotating twin screw extruders was examined. Different polymers and different polymer particulate solid systems were used, over a range of processing conditions. The results of this work shed light on the important roles that solid dissipative deformation and interparticle frictional phenomena play in generating the heat necessary to melt polymer particulate systems. This paper also attempts to deal with the modification of the Thermal Energy Balance Equation, so that it includes the above heat generating dissipative source terms.
Rheological and Mechanical Properties of Recycled Polycarbonate
Ruifeng Liang, Rakesh K. Gupta, May 2000
Polycarbonate (PC) is used in computer and electronic housings, and here it was sought to reuse this polymer after having been separated from electronic shredder residue. The separated stream was not pure PC; there was some cross-contamination. The separated polymer was characterized by rheological, thermal and mechanical methods; the measured properties were only slightly inferior to those of comparable virgin materials. Recovered plastic and virgin polymer were blended using a TSE to determine the minimum virgin content needed to mask the effects of addition of recycled material on the rheological and mechanical properties of the blend. Differences in processing behavior and mechanical performance of the blends as a function of composition are discussed in relation to potential material recycling strategies.
Color Effects of Modified Rubber on Black Colorant in Polypropylene
Eric B. Hunt, May 2000
The primary use of modified rubber is to improve flexural modulus and impact strength. The disadvantage of using modified rubber is the distortion of color when used as an additive to a polymer. This study compared the color shifts of a black colorant with differing loadings of modified rubber.
New Fast Peroxides for PVC
Kenneth W. Dixon, May 2000
Recent economic trends in the PVC market have pushed producers to reduce costs and improve productivity. Areas were sought where peroxide expertise can be utilized to develop new initiators that can help. Consequently a new developmental, fast peroxide for PVC, D-174, is being introduced which is reactive at lower polymerization temperatures, gives a more square heat profile and produces shorter polymerization cycle times for the PVC manufacturer.
Assessment of Metallocene Propylene Polymers for Cast Film Applications
Charlie Y. Lin, Michael C. Chen, Aspy K. Mehta, May 2000
The entry of metallocene-based products into polypropylene cast film is at a stage where potential in various markets is only now being assessed. The current thrust is to bring forward a set of differential properties to complement effectively Ziegler-Natta based poly-propylene cast film products. This study reviews the structure features of metallocene polymers and reports some potential benefits in cast film applications.
High Molecular Weight Flexibilizers in Low Smoke Flame Retardant PVC Compounds
E.R. Griffin, May 2000
Ethylene copolymer resin (ECR) modifiers play an important role in low smoke PVC. As high molecular weight flexibilizers these resins reduce smoke and add strength and low temperature flexibility. This combination allows compounders to increase the flame-retardant additives without compromising strength or flexibility or by adding liquids which increase smoke. This paper is presented to demonstrate these attributes versus liquid plasticizers used in PVC compounds.
Crystalline but Fully Transparent - A New Polyamide with Outstanding Properties
Hans-Peter Hauck, May 2000
Requirements for chemical resistance and transparency are usually mutually exclusive in plastics, especially for polyamides. While aromatic constituents are used to produce most amorphous polyamides, this new transparent polyamide (designated according ISO 1874: PA PACM 12, herein PA means polyamide, PACM = Bis(p-aminocyclohexyl) methane) is based on aliphatic monomers. The monomer building blocks form very small crystallites that do not scatter visible light, so consequently parts made of this polyamide are clear as glass. This so called microcrystalline structure counts for a well-balanced combination of properties, e.g. good UV-stability, high level of impact behavior, low water absorption and isotropic shrinkage. Especially its chemical resistance is superior to other transparent materials such as polycarbonate, polymethacrylate or all amorphous polyamides.
Small-Scale Testing for Brittle-Tough Transitions of Rapid Crack Propagation in PE Pipelines
Paul Davis, Stuart Hillmansen, Patrick Leevers, May 2000
The resistance to Rapid Crack Propagation (RCP) of extruded PE pressure pipe undergoes a well defined brittle-tough transition with increasing temperature. Material developers need to correlate the transition temperature with property data measured using coupon-sized samples. This paper discusses mechanisms underlying transitions in pipe specimens before presenting efforts to correlate transition temperatures of pipe with small-scale test results. A non-mechanical thermal analysis technique appears to correlate the phase transformation behaviour of raw materials with transition temperatures of extruded pipe.
The Effect of Boron Nitride on the Processability of Metallocene Based LLDPE
Sang Myung Lee, Jung Gon Kim, Jae Wook Lee, May 2000
Melt fracture of a various shapes and related processing instabilities continue to limit processing rate in many commercially important polymer processing industries such as fiber spinning, film blowing and extrusion. Therefore, the occurrence of melt fracture needs to be limited in order to produce high quality products, which have the desired physical properties. In an effort to investigate increasing the processing rate and improving the quality of the final product, a commercial LLDPE was modified by the addition of small amount Boron Nitride (BN). BN was added to the virgin LLDPE at 180°C at concentrations of 0.05, 0.1, 0.5, 0.75 and 1.0 wt %. Also, the processability of capillary flow was investigated as functions of temperature, applied shear rate and L/D for the virgin LLDPE and LLDPE containing BN. The equipment used in this study include capillary rheometer, parallel-plate rheometer and universal test machine (UTM). The degree of processability in the capillary flow was found to depend on boron nitride concentration. The relationship between the apparent characteristic relaxation time and the critical shear rate for the onset of melt fracture and slip is also discussed.
The Comparison of Newly Proposed Cavity-Variable-Based Full Factorial Design and Artificial Neural Network in Injection Molding Process
Jung Gon Kim, In Ho Shin, Jae Wook Lee, May 2000
The statistical experimental design has been used to generate useful information for injection molding process, where more precise models based on physical laws and linear relations are not available. Until now, attempts at applying traditional full factorial design have resulted in creation of many problems, due to the selection of experimental variables from the machine rather than the cavity mold. Injection molding process has plenty of variables to be carefully observed concerning parts quality. Among these, cavity pressure and temperature are the ideal candidates for process monitoring and quality control role, thanks to their capability to present the dramatic changes inside the mold.
Comparison of Experimental and Predicted Data for Conventional Single Screw Extruders
Petra Samsonkova, Jiri Vlcek, May 2000
Single screw extrusion is widely used in the processing of thermoplastic materials. Good understanding of the extrusion process can save time and capital investments. Simulation programs capture the solids conveying, melting and pumping behavior to help us study the process and eventually to fit the screw design to a particular thermoplastic material. From such a study, the best processing conditions may be determined. There is still a considerable lack of understanding of the physical process in an extruder particularly with regards to the solids conveying. Our objective is to contribute to the understanding of this process, which should lead us to an improvement of the solids conveying model. In this paper we present a set of experimental data measured on various screw designs, for varying properties of different PE resins. Further more, the comparison of measured and predicted data is presented. This comparison is used to evaluate the physical model used during simulation of the extrusion process.
Study of Polypropylene Degradation in a Co-Rotating Twin Screw Extruder
Eric Tizon, David Bigio, Leo Kasehagen, May 2000
Screw design, injection site and operating conditions are critical parameters which influence peroxide injection efficiency during PP vis-breaking. A visual study in a clear barrel extruder was performed with water and corn-syrup to simulate the mixing of a low viscosity ratio system. Liquid injection of peroxide into PP was then performed in a 30 mm COTSE and compared to the normal pre-mixed peroxide method. Operating conditions were found to greatly influence degradation by shear and injection efficiency.
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