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
Understanding Why Adhesion in Extrusion Coating Decreases with Diminishing Coating Thickness, Part I: Penetration of Porous Substrates
Barry A. Morris, May 2005
It is well known that in extrusion coating the adhesion of PE to paperboard and other porous substrates decreases with decreasing thickness. Several hypotheses are proposed for the origin of this decrease, including a reduction in time for oxidation, faster cooling in the air gap and more rapid quenching in the nip. A model of the penetration of the molten polymer into the substrate shows that the greatest effect is cooling in the nip; thinner coatings have less time to flow into the interstices of the substrate once contact with the chill roll is made. The model results agree well with experimental adhesion data from the literature.
Application of the Similarity Theory for Special Injection Molding Processes
Helmut Potente, Elmar Kaiser, Martin Schaefers, May 2005
Quality characteristics on injection molded parts are influenced by a large number of influencing factors and complex correlations. This applies to both standard injection molding processes and special processes, such as gas assisted injection molding (GAIM) and overmolding. In many cases, a closed analytical description of these correlations is not possible.One means of countering this problem is to employ the similarity theory. This creates simple correlations between the target parameter, different molded part geometries and the influencing factors.After discussing the fundamentals of the similarity theory, the characteristic numbers that describe the process are established for the special injection molding processes of GAIM" and "Overmolding". In a second step experimental investigations are presented for the mentioned processes in order to establish correlations between influencing parameters.For gas-assisted injection molding equations are derived on the basis of experiments with laboratory molds which make it possible to predict the gas bubble cross-section for different geometries. In the case of overmolding model laws are derived which can be used to transpose process settings or process conditions from model geometries to other geometries."
Cell Morphology, Surface Roughness, Impact and Odor of Microcellular Injection Molded Wood-PP Composites
Andrzej K. Bledzki, Omar Faruk, May 2005
This paper represents the investigations on the cell morphology, surface roughness, impact properties and odor concentration of microcellular wood fiber reinforced PP composites in injection molding process with different chemical foaming agents. The chemical foaming agent and wood fiber content strongly affect the microcellular structures of wood-PP composites. Microcells morphology (cell size, shape and distribution) were investigated using optical light and scanning electron micrographs. Charpy impact strength, impact resistance and damping index of the composites influenced by different chemical foaming agent type and content. Due to microfoaming, odor concentration and surface roughness significantly improved.
Flame Retardant Polypropylene Containing Functionalized Nano Clays
S.Kenig, O.Shepelev, M.Peled, May 2005
With the development of nano clay technology, new opportunities have emerged for imparting enhanced fire retardancy, mechanical and barrier properties to plastics.Polypropylene resins enjoy a large increase in consumption due to its cost/properties combination. However, one of its main shortcomings originates from its flammability. To remedy the flammability of polypropylene relatively large amounts of flame redardant additives have to be used. This in turn decreases the mechanical properties of the resultant compound.Consequently, the objective of the present investigation is aimed at exploring the effect of functionalized nano clays on the flammability retardation and mechanical properties of polypropylene. Commercial as well as novel functionalized nano clays were included in the study.Experimental results have shown that the burning mechanism of nano clay containing polypropylene compounds was completely changed due to formation of a char layer. Furthermore, 2.5% of bromine functionalized nano clays, reduced the required amount of conventional bromine containing fire retardants by 50% to meet UL 94 V-0 levels. The resulting fire retardant polypropylene compounds possessed higher modulus and strength while preserving the impact resistance compared with neat polypropylene.
History of the Plastics Industry and Future Trends: International Trade Expositions as Perspective
Margaret H. Baumann, May 2005
Tradeshows like the National Plastics Exposition (NPE) and the K Show (held October 2004 in Düsseldorf, Germany) have traditionally been bellwethers of things to come in the plastics industry. This presentation will review the highlights of developments and structural change in the plastics industry through the eyes of the NPE (SPI sponsored event) and the K show (German Machinery Association). Both shows are held every three years and we believe that developments introduced at the shows reflect the trends in the industry. Presenting analysis of the data from past shows, the author will predict what can be expected from the industry in the 21st century. The Plastics Industry is the 4th largest industry in the US and will continue to grow globally while still thriving in North America. If you look at the industry on a global basis it is still experiencing above average growth.
Effect of Reclaimed Rubber Content in NR/Carbon Black Vulcanizates Using Microwave Irradiation System
C. Kumnuantip, N. Sombatsompop, May 2005
This work examined the effect of tire-tread reclaimed rubber content on physical and mechanical properties of natural rubber, vulcanized by microwave (MW) irradiation and thermal cure (CT) systems. The results suggested that the properties of the vulcanizates from CT method was higher than those from MW method except for the swelling level in toluene. The differences in the results between these two curing systems could be explained in terms of the density and the type of crosslinks present in the NR compounds. The microwave cure was more effective as the reclaimed content was increased.
Effect of Filler Surface Treatment on Properties of Fly Ash/NR Blends
S. Thongsang, N. Sombatsompop, May 2005
Silica contents in fly ash particles of 30 and 60phr were introduced as reinforcing filler in NR compound with varying Si69 coupling agent contents. It was found that the scorch and cure times of the NR/FA vulcanizates slightly increased with a decrease in crosslink density when increasing Si69 contents. The decrease in crosslink density was compensated by chemical bonding between the rubber and the fly ash particles as a result of Si69. Concentrations of 2.0 and 4.0 wt% Si69 coupling agent were recommended for the improvement of the tensile modulus and tear strength of the NR/FA composites. The tensile strength did not change with Si69 content.
Effect of Molecular Architecture of PE on Structural Changes of PVC in PVC/PE Melt-Blend
C. Thongpin, O. Santavitee, N. Sombatsompop, May 2005
This paper studied the effect of molecular architecture of PE on structural changes of PVC in PVC/PE blends. The thermal property results indicated that PE in the blend between PVC and PE affected the degradation mechanism of PVC. This was explained in terms of a macro-radical cross-recombination reaction between PVC and PE molecules which was confirmed by considering the chemical shift in Carbon-13 Nuclear Magnetic Resonance. The changes in decomposition and glass-transition temperature of PVC in PVC/PE blends were also affected by types and melt flow indexes of the polyethylene.
Evolution of Properties of a Thermosetting Epoxy/Aromatic Amine System with Increasing Cure (Conversion): Physical Aging
Jong Keun Lee, J.K. Gillham, May 2005
Isothermal physical aging below Tg of a high-Tg thermosetting difunctional epoxy/tetrafunctional aromatic amine system has been investigated at different aging temperatures (Ta) and chemical conversions (monitored by the glass transition temperature, Tg) using the TBA freely oscillating torsion pendulum technique. In the absence of chemical reaction during an isothermal aging process, the rate of isothermal physical aging passes through a minimum with increasing conversion. The minimum is related to the minimum in mechanical loss between the secondary relaxation in the glassy state (T? ) and the glass transition relaxation (Tg) [the temperatures of both of which increase with increasing conversion]. If isothermal aging rates for all conversions (beyond gelation) would have been measured directly from temperatures below T? to above Tg, it is concluded that two maxima in isothermal aging rate would have been observed corresponding to the two relaxation processes. There exists a superposition in isothermal aging rate vs. Tg-Ta [by shifting horizontally (and vertically)], which implies that the aging rate is independent of the details of the changing chemical structure due to cure. Controlling mechanisms during physical aging are segmental mobility associated with the Tg region and more localized motion associated with the glassy-state relaxation, T?.
Nanomechanical Properties of Viscoelastic Polymers
Ho Jong Kang, Jaehyun Kim, Ohyoung Kim, May 2005
The surface mechanical properties of ethylene vinyl acetate (EVA) with various vinyl acetate (VA) contents have been investigated. These nano mechanical properties, obtained from the nanoindentation technique, were compared with bulk results from the conventional tensile test. Agreement in Young's modulus as a function of VA content is found between two data. The discrepancy in modulus value between surface and bulk was also found in EVA with higher VA content. We speculate that this is due to macroscopic structure effect on bulk modulus as well as intrinsic viscoelastic deformation behavior of EVA.
Characterization of Diene Monomers as Self-Heagling Agent for Polymer Composite and its Microcapsules
Jong Keun Lee, Xing Liu, Sung Ho Yoon, May 2005
Two different diene monomers [dicyclopentadiene (DCPD) and 5-ethylidene-2-norbornene (ENB)] as self-healing agent for polymeric composites were microencapsuled by in-situ polymerization of urea and formaldehyde. Storage modulus (G’) and tan ? vs. cure time data were obtained by dynamic mechanical analysis (DMA) to investigate cure behavior of unreacted self-healing agent mixture with catalyst. Glass transition temperature (Tg) and exothermic reaction of samples cured for 5 min and 120 min in the presence of different amounts of catalyst were analyzed by differential scanning calorimetry (DSC). In a comparison with DCPD, ENB may be advantageous as self-healing agent since it proceeds much faster in reaction at much lower amount of catalyst with no melting point and produces resin with higher Tg when cured under same conditions. Microcapsules containing the healing agent were successfully formed for both diene monomers, and characterized by thermogravimetric analysis (TGA). Optical microscope (OM) and particle size analyzer (PSA) were employed to observe morphology and size distribution of microcapsules, respectively. The microcapsules were similar in thermal property as well as particle shape and size.
Viscoelastic Properties of Crosslinked LLDPE Films
A.L. Bobovitch, Y. Unigovski, E.M. Gutman, E. Kolmakov, May 2005
Creep and stress-relaxation of linear lowdensity polyethylene (LLDPE) crosslinked with ?- irradiation was studied as a function of irradiation dose. It was shown that both storage modulus and ?- relaxation are influenced by irradiation. An influence of relatively low gel content on stress relaxation was detected. However, the creep results showed an increase of the creep strain when the polymer is irradiated with a dose below 4 Megarad (MR) in comparison with a nonirradiated film. This increase corresponded to the disorientation in the amorphous phase, which takes place as a result of the film heating during irradiation. This disorientation was demonstrated by differential scanning calorimetry (DSC) and X-ray analysis.
Validation of On-Line Molding Process Simulation
David O. Kazmer, Ranjan Nageri, Bingfeng Fan, Vijay Kudchakar, Stephen Johnston, May 2005
Plastics injection molding has been limited by the lack of observability and controllability, such that it has not been possible to know or control flow rates and pressures at multiple locations in a mold. Using cavity pressure transducers and faster than real time process simulation, the described system provides estimates of the flow rates, part weight, melt temperature, and apparent viscosity before the mold opens and the parts are ejected. Validation results for part weight are provided for a two-cavity family mold with a valve-gated hot runner system.
Concept Design of a Wireless Pressure, Temperature, and Flow Rate Sensor for Injection Molding
David Kazmer, Robert Gao, Yong Cui, Stephen Johnston, Peter Knepper, May 2005
A new concept design for a self-energizing, wireless sensor is presented. The sensor extracts energy from the polymer melt and transmits discrete acoustic signals whose timing indicates a pressure change and whose frequency indicates the melt temperature. A receiving system outside the mold receives the transmitted signals and reconstructs the melt pressures and temperatures. It then utilizes mapping and simulation techniques to estimate the pressure, temperature, and flow rates in the entire mold in real time.
Nanocomposite Formation Mediated by Specialty Controlled Architecture Materials
James M. Nelson, Ryan E. Marx, Myles Brostrom, John W. Longabach, Neil Granlund, Terri A. Shefelbine, Kenneth J. Hanley, Mark E. Napierala, Mary Buckett, May 2005
Controlled architecture materials (CAMs) (ie. Block copolymers) are being explored as specialty additives for the formation of polymer nanocomposites under meltprocessing conditions. These block copolymer-based additives provide interesting exfoliation solutions for clays of differing hydrophobicity in a variety of polyolefin and styrenic resins. This presentation will outline details of the nanocomposite formation process, nanocomposite characterization and highlight composite physical property enhancements.
Ultrasonic Technique and Probes for Monitoring Surface Imperfection of Microfluidic Plastic Devices during Injection Molding
Y. Ono, C.-C. Cheng, C.-K. Jen, J. Tatibouët, J.-F. Hétu, May 2005
Miniature ultrasonic probes were embedded into the mold of an injection molding machine for microfluidic devices. Surface imperfection of the molded parts was monitored using the ultrasonic velocity of the part obtained during molding. It was verified that the lack of sufficient holding pressure caused detachment of the molded part from the mold surface before the part sufficiently solidified, resulting in the increase of the roughness on the part surface. The presented ultrasonic technique and probes enable on-line quality control of the molded part by optimizing the holding pressure and the improvement of process efficiency by reducing the cycle time.
Study on Aerodynamics of Cooling in Film Blowing
Zhijie Zhang, P.G. Lafleur, May 2005
A numerical analysis using a renormalization group (RNG) k-? model and Fluent software was performed on the air ring cooling system of the film blowing process. The calculations were in a good agreement with the experimental results to predict maximum air velocities along the bubble surface at different axial distance from the die. Outside of the air-ring, the simulation results indicated that the heat transfer coefficient function of the form, h = aVmax b, is adequate mostly at low Blow-Up-Ratio (BUR). Different bubble shapes, for the same BUR, produced significant differences in the air flow pattern as well as heat transfer coefficient. In this work we want to study the correlation between thermal inertia and aerodynamics of cooling air under different bubble geometry.
Nanoclay Exfoliation in Thermoset Polyimide
Michael Gintert, Sandi Campbell, Sadhan C. Jana, May 2005
The mechanism of nanoclay exfoliation in a thermoset polyimide nanocomposite system is being investigated. It has been found that full exfoliation is not achieved simply by processing the clay in the polyimide resin. Therefore, the clay is first intercalated with a lower molecular weight resin, then dispersed into a higher molecular weight resin, and the entire system is cured to obtain the final composite material with exfoliated nanoclay particles. The lower molecular weight resin residing inside the clay galleries exerts large elastic forces on clay layers upon crosslinking due to higher crosslink density. Smaller viscous stresses are exerted against clay layer separation by the surrounding polymer matrix due to lower crosslink density. The exfoliated clay structures are characterized by wide angle X-ray diffraction and transmission electron microscopy.
Rheology of Polystyrene/Carbon Nanofiber Composites
Jianhua Xu, Yingru Wang, Kurt W. Koelling, Stephen E. Bechtel, May 2005
Polystyrene/carbon nanofiber (CNF) composites with various CNF concentrations are prepared using melt blending and solvent casting techniques. Size and dispersion of the CNF are characterized using SEM, TEM, and optical microscopy. Linear and non-linear rheological behavior at elevated temperatures was measured to be very sensitive to the CNF aspect ratio, concentration and temperature. Orientation of the CNFs in shear and extensional flow is characterized using TEM micrographs in 2 perpendicular directions. A full 3D thermo-mechanical model is used to couple the rheology and the CNF orientation.
In-Line Monitoring of Polymer Compounding Process in a Twin-Screw Extruder
Dongbiao Wang, Kyonsuku Min, May 2005
Experiments on in-line monitoring of PVC compounding process were performed with an ultrasound probe in a die. The effects of polymer melt pressure on ultrasound wave velocity and attenuation were discussed. A characterization method for polymer compounding was proposed based on the analysis of wave attenuation. The results showed that wave velocity was less dependent on melt pressure for all four PVC systems at constant die temperature, while the wave attenuation for PVC/PBA and PVC/DMP/CaCO3 systems showed slightly more dependence due to the scattering effect from existence of unmelted PVC primary particles or different dispersion levels of filler. Except the scattering effect, comparisons of wave attenuation between the four PVC compounds suggested that higher melt viscosity caused higher wave attenuation.
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