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
VARIOTHERMAL HEATING CONCEPTS FOR EXTRUSION EMBOSSING OF MICRO-STRUCTURED FILMS
Extrusion embossing is an economic and fast process for the production of large quantities of structured films. This one-step-process can be used for embossing of macroscopic and microscopic structures as well. The replication accuracy of microstructures can be increased significantly using variothermal heating concepts for the embossing rolls. Two variothermal heating concepts using additional inductive or laser-based heating devices are developed at the IKV. The achievable temperature curve on the roll surface is determined in dependence of the heating device and the time. Furthermore improvements in replication accuracy by variothermal heating are presented.
IN-MOLD SHRINKAGE MONITORING SENSOR FOR INJECTION MOLDING
Dimensional consistency is a critical attribute of molded part quality but is frequently only estimated from cavity pressure or part weight measurements. An in-mold shrinkage sensor having a deflectable diaphragm under melt pressure instrumented with strain gages connected in a full bridge circuit is designed and validated. Molded part shrinkage is then measured as the polymer melt solidifies, shrinks, and retracts from the mold wall. The results of a DOE conducted to validate the performance of the sensor indicate the sensor outperforms both cavity pressure transducers and regression models, and is able to measure the shrinkage to an absolute accuracy of 0.01 mm for a 2.5 mm thick part.
HARD COATED TRANSPARENT COPOLYCARBONATE WINDOWS AND ARTICLES WITH EXCEPTIONAL FR AND LOW OSU HEAT RELEASE VALUES
New OSU compliant, hard coated polycarbonate copolymer articles were formed by extrusion and injection molding processes followed by hard coating. These samples were prepared using a variety of hard coatings and processes to afford scratch resistant, low color, high transmission and low haze articles. These highly transparent, low color articles are the first in their class to be fully compliant to the OEMs and FAA (FAR25.853) aerospace flammability standards. The combination of coating and specific resin is needed to produce the excellent balance of flame resistance, durability and optical properties.
A NEW PROCESS TO RECYLE PET BOTTLE FLAKES FOR FOOD CONTACT APPLICATIONS
In the Bepex process ground and washed post-consumer polyester packaging (rPET) flakes are efficiently decontaminated and polymerized for food contact packaging applications. The hot processed flakes may be directly extruded into the bottles, sheets or films thereby eliminating several energy, capital and labor intensive steps resulting in a cost-effective simplified process. Volatile contaminants in the polymer are removed by diffusion into the gas phase thereby purifying the polymer in the solid state under atmospheric pressure. The presence of small amounts of selected vapors in the gas enhances diffusion of the volatile components providing efficient decontamination without excessive molecular weight build-up.
INFRARED ACTUATION OF CARBON NANOTUBE ƒ??LIQUID CRYSTALLINE ELASTOMER NANOCOMPOSITES
This paper reports the infrared (IR) actuation performance of a new family of single-wall carbon nanotube (SWNT)-nematic liquid crystalline elastomer (LCE) nanocomposites. A strong and instantaneous response (~30% strain) to the IR stimulus was observed in the SWNT-LCE nanocomposites due to the photon absorption of the SWNTs resulting in an increase in the nanocomposite film's temperature and thereby triggering a nematic-isotropic phase transition. The IR strain response of the SWNT-LCE nanocomposites increased with the SWNT loading level and the degree of hot-drawing but decreased with the photo-curing time.
COMPOUNDING AND INJECTION MOLDING OF SOLVENT-BASED HEALING COMPOUNDING AND INJECTION MOLDING OF SOLVENT-BASED HEALING
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
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
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
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
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
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
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
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
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
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
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
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
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
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
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.
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