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

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.

The Effects of Pulse Cooling on The Molding Cycle and Part Variation

Andrew S. Lamont, Corey J. Linden, May 2000

A design of experiments study was performed that analyzed the effect of pulsed heating and cooling on warpage of an injection molded part. The study involved the following factors: inlet water temperature, melt temperature, mold temperature, and cooling time. The critical dimension was measured by an optical coordinate measuring scope with a repeatable process determined by an R&R study. The gathered data determined that, within the range of the factors study, the inlet water temperature was the only one that did not effect warpage.

Characterizing Scrap Vinyl Flooring to Determine Feasible Reuse Options

Andrew Lawrence, May 2000

The manufacturing waste generated during the production of vinyl floor tiles is typically sent to landfills, rather than recycled, because of a lack of reuse options for this material. This waste is typically PVC loaded with approximately 80% limestone. The goals of this research are to characterize this material to determine the feasibility of reprocessing it and to measure the mechanical properties of the processed material. This study will also attempt to suggest an injection molding or extrusion application for the mixture.

A Method to Characterize the Impact Properties of Hand Tools

John Stanko, John Kennerknecht, May 2000

There does not currently exist a method for the characterization of the impact properties of hand tools, specifically screwdrivers. Without a scientific method of collecting data for various designs, it is difficult for manufacturers to determine the effect of material or design changes on the impact properties of the product. The most demanding application for these hand tools can often be a hammer blow to the handle of the product, and therefore this abuse must be strongly considered in the design criteria.

Rheological Characteristics of Polymer Blends

Roberto Guimarães Pereira, Alexandre Alves Costa Oliveira, May 2000

This work presents an experimental observation of the rheological characteristics of the TPE/SB blend (Thermoplastic Elastomer / Styrene-Butadiene) used in the plastic transformation industry for medical applications. The flow curves (shear viscosity x shear rate) of the blend were investigated at different temperatures and in a wide range of shear rates. During the extrusion, the instability phenomenon (melt fracture) and its relation with the shear rate and temperature parameters was also investigated. All the experiments, the flow curves and melt fracture observation, were performed in a Capillary Rheometer ( a Rosand Rh-2100 capillary rheometer) working with a 1 x 16 mm rod capillary die.

Evaluation of Liquid Gas-Assisted Injection Molding

Doyoung Moon, Seungwook Lee, Donghak Kim, May 2000

Gas-Assisted injection molding has been applied successfully in plastic industry within last 10 years. Liquid gas-assisted injection molding (LGAI) is a good alternative of conventional gas-assisted injection molding process. In LGAI process, a liquid is injected under low pressure into the melt stream. The liquid vaporizes and pushes the melt downstream and creates hollow channels within part. HELGA® patents this process originally. We had evaluated this process with different-type molds and liquid nozzles that we develope. Finally, we compared the LGAI process to the conventional gas-assisted injection molding process.

Surface Enrichment in Polymer Blends Involving Hydrogen Bonding

Yuzhi Duan, Eli M. Pearce, May 2000

Poly(4'-hydroxyl-4-ethylphenylsiloxane)(PHEPS) has been synthesized via hydrosilylation followed by hydrolysis. This polymer, hydrogen bonding donor, was blended with three kinds of hydrogen bonding acceptors that include poly(4-vinylpyridine) (PVPy), poly(acrylonitrile) (PAN) and poly(ethylmethyacylate) (PEMA). The surface enrichment with PHEPS, which has lower surface energy, was characterized by X-ray Photoelectron Spectroscopy (XPS). The effect of the strength of hydrogen bonding interaction on the surface compositions of the blends was studied. The results showed that surface enrichment in miscible polymer blends was responded to the balance between the differential in the surface energy of the constituents and the bulk enthalpic interactions.

The Effect of Chemical Blowing Agent Dosage on the Properties of Extruded Expanded Polypropylene

Dorian Dixon, P.J. Martin, E. Harkin-Jones, May 2000

This paper investigates the influence of CBA (chemical blowing agent) concentration on the properties of extruded EPP (expanded polypropylene) rod samples. A design of experiment methodology was adopted to quantify the effect of CBA (endothermic type) dosage on EPP properties. Foam characteristics measured, were density, cell structure, tensile properties, premature foaming, and extrusion parameters (melt temperature and pressure). The research revealed that an optimal blowing agent concentration of 0.5% exists in terms of obtaining the finest cell morphology and most efficient material savings/density reduction.

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.