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

COMPOUNDING AND INJECTION MOLDING OF SOLVENT-BASED HEALING COMPOUNDING AND INJECTION MOLDING OF SOLVENT-BASED HEALING

Mohamed Esseghir, Anthony C. Neubauer, May 2010

The solvent-based self-healing approach used in thermosets has been extended to thermoplastic materials in which common organic solvents are used as compartmentalized liquid healing agents. Robust, solvent-filled poly(urea-formaldehyde) microcapsules are compounded into a thermoplastic poly(methyl methacrylate) matrix and then injection molded into compression test specimens. MicroCT (computed tomography) imaging is used to determine capsule survival rate after each processing step. Mechanical testing is performed on the double cleavage drilled compression3 specimens. Upon crack damage, solvent is released from the embedded microcapsules, which leads to polymer chain entanglement across the crack plane to restore the virgin fracture toughness to the material.

MECHANICAL PROPERTY RETENTION OF HIGH HEAT POLYCARBONATES UNDER LONG TERM AGING AT ELEVATED TEMPERATURES

Shyh-Shin Hwang, Peming P. Hsu, C.-W. Chiang, May 2010

Industrial lighting applications require plastics that can be used at elevated temperatures for long periods of time. To understand the suitability of a new class of high heat polycarbonates for such applications, their heat aging performance was investigated at temperatures ranging from 140oC to 180oC for up to 7500 hours. The rate of loss in mechanical properties (tensile strength and impact) has been used to predict the long-term performance of these materials. The new high heat polycarbonates showed better retention of mechanical properties compared to conventional and other high heat polycarbonate materials.

WEATHERING PERFORMANCE OF A SCRATCH RESISTANT WEATHERING PERFORMANCE OF A SCRATCH RESISTANT

T. M. Lewis, A. I. Isayev, J. Keum, May 2010

The weathering performance of a Lexan* copolycarbonate resin was studied against a benchmark PC resin. Known ISO, ASTM and SAE weathering protocols were used and observed differences explained. Lexan* copolycarbonate resin offers a scratch resistant polycarbonate solution that opens up new possibilities in terms of part performance. Key applications range from mobile phones to interior automotive trims and benefit from the elimination of secondary operations due to the increased hardness of the material. This can lead to costout opportunities and environmentally friendlier solutions where conventional protective hard coatings or painted surfaces are considered.

A CURE KINETICS MODEL FOR THE NON-ISOTHERMAL CURING OF POLYIMIDE

T. M. Lewis , A. I. Isayev , J. Keum, May 2010

A cure kinetics model for curing a phenylethynyl terminated imide (PETI-330) was proposed including induction and curing stages. Model parameters for both stages were determined from non-isothermal DSC runs at various heating rates and corrected for the temperature difference between the sample and the furnace. These parameters were used to predict the state of cure measured in compression molded slabs obtained at fixed temperatures for various times and isothermal DSC runs including the curing that occurs during the transient temperature variation before reaching the set temperature.Experimental results are in good agreement with the predicted evolution of cure in the DSC and molded samples.

COMPLEX THERMAL HOT-RUNNER BALANCING – A METHOD TO OPTIMIZE FILLING PATTERN AND PRODUCT QUALITY

Florian Petzold , Marco Thornagel , Kaushik Manek, May 2010

Depending on the material and process parameters geometrically balanced runners can show rheological imbalances. In hot runner systems these imbalances are handled by controlling the nozzle tempering. However this balancing method leads to high polymer temperatures and causes a product quality that differs from part to part. This paper presents and discusses the preferential polymer flow paths inside hot-runner systems and their dependency on the plastic system as simulated and analyzed by SIGMASOFT. It will be shown that a complex thermal hot-runner tempering layout tweaked by simulation reduces the imbalances and improves the product quality at the same time.

COMPLEX THERMAL HOT-RUNNER BALANCING – A METHOD TO OPTIMIZE FILLING PATTERN AND PRODUCT QUALITY

Florian Petzold , Marco Thornagel, May 2010

Depending on the material and process parameters geometrically balanced runners can show rheological imbalances. In hot runner systems these imbalances are handled by controlling the nozzle tempering. However this balancing method leads to high polymer temperatures and causes a product quality that differs from part to part. This paper presents and discusses the preferential polymer flow paths inside hot-runner systems and their dependency on the plastic system, as simulated and analyzed by SIGMASOFT. It will be shown that a complex thermal hot-runner tempering layout tweaked by simulation reduces the imbalances and improves the product quality at the same time.

THE MECHANICAL PROPERTIES OF MEDIUM MOLECULAR WEIGHT HIGH DENSITY POLYETHYLENE FILMS: MAKING THE LINK BETWEEN ORIENTATION AND RHEOLOGY

T. Ishikawa, F. Nagano, T. Kajiwara, May 2010

This paper describes a study of the mechanical properties of films produced from five different medium molecular weight homopolymer high density polyethylene resins. The machine direction (MD) tear strength and dart impact strength of these films track together. This is due to the tendency of these films to fail during dart impact testing by tearing in the machine direction. The ratio of MD and transverse direction (TD) tear properties correlates with low frequency linear viscoelastic measurements. There is a straightforward relationship between melt index measurements and low frequency rheology for the resins in our study, which relates film properties directly to readily available resin properties and film processing conditions.

ANALYSIS AND FABRICATION OF FOAM DIELECTRIC ANTENNA SPACERS

Jonathan S. Colton , Christopher Blandin, May 2010

Dielectric materials are used as spacers in antennas. The design of the dielectric determines the properties of the antenna. The insertion of high dielectric materials in a specific pattern into a low dielectric matrix material is one means to accomplish this. This paper reports on the insertion of metal cylinders (wire or nails) into polymer foams to produce such a material. Depending upon the antenna properties desired the patterns and number of nails vary tremendously. Varying the depths of the nails into the antenna spacers is also important. A penetration model was developed that calculates the forces required to penetrate a nail into foam. Experimental observations are used to verify the model. These equations allow one to predict the forces required for a nail to be inserted into foam to a desired depth thereby facilitating manufacture of these dielectric materials.

ANALYSIS AND FABRICATION OF FOAM DIELECTRIC ANTENNA SPACERS

Jonathan S. Colton , Christopher Blandin, May 2010

Dielectric materials are used as spacers in antennas. The design of the dielectric determines the properties of the antenna. The insertion of high dielectric materials in a specific pattern into a low dielectric matrix material is one means to accomplish this. This paper reports on the insertion of metal cylinders (wire or nails) into polymer foams to produce such a material. Depending upon the antenna properties desired, the patterns and number of nails vary tremendously. Varying the depths of the nails into the antenna spacers is also important. A penetration model was developed that calculates the forces required to penetrate a nail into foam. Experimental observations are used to verify the model. These equations allow one to predict the forces required for a nail to be inserted into foam to a desired depth, thereby facilitating manufacture of these dielectric materials.

A PHENOMENOLOGICAL CONSTITUTIVE MODEL FOR STRAIN SOFTENING PREDICTION IN SEMI-CRYSTALLINE POLYMERS

Mariajosé Pineda Manzano , Joel Bohórquez , Agustín Torres, May 2010

Strain softening in semi-crystalline polymers is one of their most important viscoelastic characteristics. Compared with other materials polymers are very sensitive to temperature and strain rate and there are many elements like molecular structure density amorphous fraction that can affect their mechanical behavior. A new phenomenological model with strain strain rate and temperature dependence on stress was developed based on the G’sell & Jonas model with the addition of a new expression used to predict the strain softening phenomena completing the whole mechanical behavior of semi-crystalline polymers from initial strain till fracture. Three experimental curves of each material converted to their true tensile stress-strain curves that includes variation in strain rate and temperature are needed to estimate the seven material coefficients of the model. Model verification was performed on various materials such as PE PP PET and PA (Nylon). This model was developed to further study the complex deformation patterns that occur in ductile thermoplastic materials subjected to impact loads.

A PHENOMENOLOGICAL CONSTITUTIVE MODEL FOR STRAIN SOFTENING PREDICTION IN SEMI-CRYSTALLINE POLYMERS

Mariajosé Pineda Manzano , Joel Bohórquez , Agustín Torres, May 2010

Strain softening in semi-crystalline polymers, is one of their most important viscoelastic characteristics. Compared with other materials, polymers are very sensitive to temperature and strain rate, and there are many elements, like molecular structure, density, amorphous fraction, that can affect their mechanical behavior. A new phenomenological model with strain, strain rate and temperature dependence on stress was developed based on the G'sell & Jonas model with the addition of a new expression used to predict the strain softening phenomena, completing the whole mechanical behavior of semi-crystalline polymers from initial strain till fracture. Three experimental curves of each material, converted to their true tensile stress-strain curves, that includes variation in strain rate and temperature, are needed to estimate the seven material coefficients of the model. Model verification was performed on various materials such as PE, PP, PET and PA (Nylon). This model was developed to further study the complex deformation patterns that occur in ductile thermoplastic materials subjected to impact loads.

A GPC-Mx Approach Of Improving Rheology-Mwd Prediction For Polypropylene

Wallace W. Yau , Jian Wang , Rongjuan Cong , David Gillespie , Joe Huang, May 2010

A new GPC polydispersity parameter, MxR, was introduced in this study. The MxR value, based on the GPC-Mx concept originally proposed by Yau [1], was found to be more suitable to account for the effect of different parts of the polymer molecular weight distribution (MWD) on rheology measurements at different shear rates than do the traditional polydispersity index based on the ratio of Mz, Mw and Mn values. By using this Mx-approach on a set of polypropylene homopolymers, we show that a much improved correlation indeed exists and can be achieved between GPC measurement with the rheology polydispersity indices of PDI and ModSep. Also presented in the paper is the improved correlation between melt flow rate (MFR) and molecular weight (MW) by using this Mx approach.

AN EXPERIMENTAL INVESTIGATION INTO MELT PUMP PERFORMANCE

Walter S. Smith , Luke A. Miller , Timothy W. Womer, May 2010

Melt pump performance and efficiencies will vary according to the viscosity of the resin being pumped, and the discharge pressure that the melt pump will need to overcome. Resin melt temperature differences and power requirements of the pump, will vary according to the resin, and conditions that the pump will operate under. This paper will explore the processing differences in (3) resins on gear pump performance at (4) different pump speeds, at three different discharge pressures. Discharge pressures on the pump will be varied keeping the suction pressure constant, thus increasing the change in pressure across the pump. Melt temperature, and pump efficiency. melt pump motor amperage, and total output, (kg/hr) will then be measured and recorded.

EFFECT OF ALUMINA NANOPARTICLES ON THE PROPERTIES OF LOW-VISCOSITY CYANATE ESTER ADHESIVES FOR COMPOSITE REPAIR

Wilber Lio , Katherine Lawler , Xia Sheng , Mufit Akinc , Michael R. Kessler, May 2010

Polymer matrix composites (PMCs) are susceptible to microcracks and delaminations from impacts and thermal/mechanical loadings that greatly reduce their mechanical integrity. This is especially a problem for high-temperature PMCs because current repair resins have low glass transition temperatures (Tg's) that stem from the low prepolymer viscosities required of injectable resins. Bisphenol E cyanate ester has both a high cured Tg and low prepolymer viscosity, ideal for the injection repair of high-temperature PMCs. Alumina nanoparticles were incorporated to improve adhesive strength and engineer prepolymer viscosity. Lap shear tests were performed to evaluate the effects of alumina nanoparticles on the adhesive strength of the resin.

TRANSIENT RHEOLOGY OF A POLYPROPYLENE MELT REINFORCED WITH LONG GLASS FIBERS

Hesam Ghasemi , Pierre J. Carreau, Musa R. Kamal, May 2010

The purpose of this research is to understand fiber orientation of long glass fibers (> 1mm) in polymer melts and the associated rheology in well-defined simple shear flow. Specifically, we are interested in associating the rheological behavior of glass fiber reinforced polypropylene with the transient evolution of fiber orientation in simple shear in an effort to ultimately model fiber orientation in complex flow. A sliding plate rheometer was designed to measure stress growth in the startup and cessation of steady shear flow. Results were confirmed by independent measurements on another sliding plate rheometer13. A fiber orientation model that accounts for the flexibility of long fibers, as opposed to rigid rod models commonly used for short fibers, was investigated and results are compared with experimentally measured values of orientation. The accuracy of this model, when used with the stress tensor predictions of Lipscomb, is evaluated by comparing against experimental stress growth data. Samples were prepared with random initial orientation and were sheared at different rates. Results show that fiber flexibility has the effect of retarding transient fiber orientation evolution. Additionally, it is shown that the stress growth measurements provide results that are not fully explained by the chosen models.

CHALLENGING THE PARADIGM OF MICROCELLULAR FOAMS: MECHANICAL PROPERTIES OF LOW-DENSITY CYCLO-OLEFIN COPOLYMER FOAMS

Richard Gendron , Martin Bureau, May 2010

Low-density foams of ethylene-norbornene copolymers were produced and their mechanical properties in compression investigated. Microcellular morphologies were observed with mean cell diameters lower than 20 ?m. Although the cyclo-olefin copolymer (COC) resin shares similar mechanical properties with polystyrene elastic modulus and compressive strength of the microcellular COC foams were much lower than the values for standard PS foam having larger cells (100-200 ?mrange) comparison made at the same density i.e. in the 50- 100 kg/m3 range. This goes against the usually accepted paradigm of enhanced properties with microcellular foams. Mechanisms for such unexpected behavior are proposed.

CHALLENGING THE PARADIGM OF MICROCELLULAR FOAMS: MECHANICAL PROPERTIES OF LOW-DENSITY CYCLO-OLEFIN COPOLYMER FOAMS

Richard Gendron , Martin Bureau, May 2010

Low-density foams of ethylene-norbornene copolymers were produced and their mechanical properties in compression investigated. Microcellular morphologies were observed, with mean cell diameters lower than 20 ?¬m. Although the cyclo-olefin copolymer (COC) resin shares similar mechanical properties with polystyrene, elastic modulus and compressive strength of the microcellular COC foams were much lower than the values for standard PS foam having larger cells (100-200 ?¬m range), comparison made at the same density, i.e. in the 50- 100 kg/m3 range. This goes against the usually accepted paradigm of enhanced properties with microcellular foams. Mechanisms for such unexpected behavior are proposed.

MICROMOLDING FOR QUARTZ GLASS/POLYMER COMPOSITES

Darin VanDerwalker, Stephen Johnston, Dan Hazen, David Kazmer, May 2010

Micromolding with microscale surface features and thin-wall plates of the quartz glass/polymers composites were performed to fabricate a new micro-fluidic plate with glass. Effects of process parameters on processability and surface replication of the molded parts were evaluated. The replication ratio and internal morphology of molded green and sintered microparts were analyzed using SEM and a confocal laser scanning microscope. During sintering processes, the green molded composites shrank with removal of binder polymer. The internal morphology affected shrinkage of green molded composites. The surface replication ratio of molded and sintered parts showed high values. Sintered molded parts were produced with a high aspect ratio of 3.4 and 10 ?¬m micro-line width.

EFFICACY OF SATURATED DESIGN OF EXPERIMENTS IN MULTIVARIATE PROCESS CHARACTERIZATION

Darin VanDerwalker , Stephen Johnston , Dan Hazen , David Kazmer, May 2010

Process characterization provides a model of process responses as a function of process factors, which is useful for process optimization and quality control. In this paper, four Design of Experiments (DOE) are implemented for a thin wall molding process, including two fractional factorial designs, a D-optimal design, and a supersaturated fractional factorial design. The capability of the DOEs are subsequently analyzed with respect to the estimated main effects and defect prediction capabilities. The results indicate that fully saturated designs are satisfactory for process characterization, but all critical process factors should be investigated. Experimental designs having confounded process factors were found preferable to experimental designs of similar size that were not confounded, but investigated fewer factors.

REPLICATION PROPERTIES AND STRUCTURE IN MICROMOLDING WITH HEAT INSULATOR MOLD

Alan D. Jaenecke, May 2010

Micromolding with microscale surface features and thin-wall plates was performed to fabricate zirconia with heat-insulated molds. Effects of process parameters on processability and surface replication of the molded optical parts such as a diffraction grating and anti-reflective plates were evaluated. The replication ratio and higher-order structure of molded parts were analyzed using SEM and a polarizing optical microscope. Using an insulated mold, the flow length and surface replication ratio of molded parts increased. The molecular orientation of molded parts decreased using this mold, as it did in molding conditions of higher mold temperatures and injection temperatures.