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
COMPRESSION INDUCED SOLIDIFICATION (CIS) . A NOVEL INJECTION MOLDING STRATEGY FOR HIGH PRECISION PARTS
N. Rudolph , I. Kühnert , G. W. Ehrenstein, May 2010
During polymer processing the solidification is accompanied by local and temporarily varying temperature and pressure distributions. The simultaneous occurrence of the molten and solid state leads to the development of inhomogeneous shrinkage and dimensional instability.With a novel processing approach (CIS), the solidification is achieved by uniform compression over the entire part volume, which leads to an even shrinkage.In this paper, the fundamentals for this process were investigated. It was found that the specific volume is dependent on the pathway of compression. As main impact factors the pressure, temperature and compression speed were detected. Finally, the compression heating of the melt was measured and a relation to the volume change was found.
THREE DIMENSIONAL SIMULATION OF COEXTRUSION IN A COMPLEX PROFILE DIE
N. Rudolph, I. Kühnert, G. W. Ehrenstein, May 2010
Mesh partitioning technique is used to simulate bilayer coextrusion in a complex profile extrusion die. Mesh partitioning technique allows coextrusion simulation without changing the finite element mesh as the interface between the adjacent polymer layers is changed during a coextrusion simulation. Since the finite element mesh in the die remains fixed during the simulation, the mesh partitioning technique allows coextrusion simulation even in highly complicated profile dies. Effect of polymer viscosity on interface shape, velocity, pressure, shear rate, and residence time distribution in a profile coextrusion die is analyzed. It is found that polymer viscosity has significant effect on the interface shape, velocity, pressure, and shear rate, but only a minor effect on the residence time distribution in the die.
A STUDY OF FOAMING MECHANISMS IN ROTATIONAL MOLDING
A. Gava, G. Lucchetta, May 2010
The presented research focuses on the fundamentals of the foaming process in rotational molding and control of final cellular structure. The experimental results of foaming experiments, performed under isothermal and non-isothermal conditions, indicate that the foaming process could be divided into three distinct phases: bubble nucleation, bubble growth and bubble coalescence. It was found that bubble growth and coalescence mechanisms are dynamically competing during the entire foaming process and the degree of uniformity and structure of the final foam are primarily determined by the nucleation stage.
MICRO INJECTION MOLDING OF LCP-MODIFIED PA66
A. Gava , G. Lucchetta, May 2010
Injection molded micro parts require accurate replication of micro-scale features. This replication is governed by complex mechanisms and its quality depend on the plastic material properties the geometry of the features and the process conditions The objective of this paper is to improve the replication of the micro-scale features by decreasing the polymer viscosity. The effects of melt viscosity and molding conditions on replication of microscopic features in injection molded parts were examined for a PA66 blended with a LCP additive. The replication was measured at different contents of LCP and at different process conditions.
MICRO INJECTION MOLDING OF LCP-MODIFIED PA66
A. Gava , G. Lucchetta, May 2010
Injection molded micro parts require accurate replication of micro-scale features. This replication is governed by complex mechanisms and its quality depend on the plastic material properties, the geometry of the features and the process conditions The objective of this paper is to improve the replication of the micro-scale features by decreasing the polymer viscosity. The effects of melt viscosity and molding conditions on replication of microscopic features in injection molded parts were examined for a PA66 blended with a LCP additive. The replication was measured at different contents of LCP and at different process conditions.
SELECTIVE LOCALIZATION AND MIGRATION OF MULTIWALLED CARBON NANOTUBES IN BLENDS OF POLYCARBONATE AND STYRENE-ACRYLONITRILE
Andreas Göldel , Gaurav Kasaliwal , Petra Pötschke, May 2010
The localization of multiwalled carbon nanotubes (MWNT) in immiscible polymer blends was discussed based on the aspect ratio of the filler particles and the wetting coefficient. As a model system, MWNT were introduced into compatible blends of polycarbonate (PC) and poly-styrene-acrylonitrile (SAN) by melt mixing in a microcompounder either by pre-compounding small amounts into PC or SAN or by mixing all three components together. In agreement with the presented theoretical considerations, in all blends, regardless of the way of introducing the nanotubes, the MWNT were exclusively located within the polycarbonate phase, inspite of the almost equal surface energies of the two blend phases.
MORPHOLOGY DEVELOPMENT OF POLYPROPYLENE/POLYAMIDE 6 BLEND MOLDED BY WATER-ASSISTED INJECTION MOLDING
Han-Xiong Huang , Run-Heng Zhou , Wei-Wen Zhou, May 2010
Morphology development of polypropylene /polyamide 6 (PP/PA6) blend in water-assisted injection molded (WAIM) curved pipe was investigated. The blend morphology development was interpreted with the aid of stress and temperature fields within the mold cavity under melt filling and high-pressure water penetration during WAIM process. The results showed that the morphology developed at the position near the water inlet is induced mainly by the melt filling, whereas the morphology at the position near the end of water channel is mainly ascribed to the high-pressure water-assisted filling. Then the water pressure and melt temperature were investigated in terms of their effects on the morphology development of dispersed PA6 phase. It was demonstrated that higher water pressure result in more obvious deformation of the dispersed phase at the position near the end of water channel.
DIE DESIGN OPTIMIZATION FOR MONOLAYER AND COEXTRUSION PROCESSES
Han-Xiong Huang, Run-Heng Zhou, Wei-Wen Zhou, May 2010
Multilayer materials offer benefits in terms of new materials for packaging and barrier applications. The ability to maintain layer stability as the material flows into different die designs is important for fabrication of these materials. This work investigated different die designs for use in fabricating multilayer films. Three dimensional analyses of different types of manifold designs have been applied to optimize the die design of a coat hanger die. For the horizontal multilayer systems, an elongated tear drop manifold design with a relatively sharp angle provided the most uniform flow and layer distribution. With the vertical multilayer system, however, a gradual change in the manifold geometry enabled more uniform flow. The vertical layered systems also consistently exhibited curving of the layer interfaces. The horizontal layers were not affected by the presence of a secondary manifold, but in vertical layered systems, the secondary manifold produced non-uniformities in the layers and instabilities in the flow.
A NOVEL 3-D BLOW MOLDING METHOD AND ITS PART THICKNESS CONTROL STRATEGY
Geng-Qun Huang , Han-Xiong Huang, May 2010
In this study, a novel air traction 3-D blow molding machine was presented. Distinct from conventional blow molding machine, this 3-D blow molding machine utilized compressed air to draw the extruded parison through the closed mold. The results showed that the new 3-D molding machine was low flash waste and high molding quality. To further improve the performance of the 3-D blow molded product, a control strategy based on fuzzy iterative learning control algorithm was designed and implemented to control the wall thickness of blow molded part. The results showed that after five times iterations, the average axial thickness of 3-D bend pipe converged to the object area of thickness.
BIAXIAL CONSTITUTIVE RESPONSE OF PET DURING HOT DRAWING: EXPERIMENTAL STUDY AND NEW IMPLICATIONS FOR CONSTITUTIVE MODELLING
Andy C.-Y. Lew , Paul Buckley, May 2010
A study was made of hot drawing of an amorphous isotropic poly(ethylene terephthalate) (PET) under biaxial stress in the temperature and strain rate regime prevalent in injection stretch blow molding and biaxial film drawing. The constitutive response was mapped out more thoroughly than hitherto as functions of temperature and strain rate for constant width and equi-biaxial drawing. The data suggest multiple Eyring type flow activation volumes at lower drawing temperatures. Also the flow activation volume appears to decrease with increasing strain level possibly attributed to entanglement slippage and intrinsic anisotropy of the flow process. The former observation would have a significant implication for current constitutive modelling approaches based on single shear and pressure activation volumes. The implications for refinement of the model are discussed.
BIAXIAL CONSTITUTIVE RESPONSE OF PET DURING HOT DRAWING: EXPERIMENTAL STUDY AND NEW IMPLICATIONS FOR CONSTITUTIVE MODELLING
Andy C.-Y. Lew , Paul Buckley, May 2010
A study was made of hot drawing of an amorphous isotropic poly(ethylene terephthalate) (PET) under biaxial stress, in the temperature and strain rate regime prevalent in injection stretch blow molding and biaxial film drawing. The constitutive response was mapped out more thoroughly than hitherto, as functions of temperature and strain rate, for constant width and equi-biaxial drawing. The data suggest multiple Eyring type flow activation volumes at lower drawing temperatures. Also the flow activation volume appears to decrease with increasing strain level, possibly attributed to entanglement slippage and intrinsic anisotropy of the flow process. The former observation would have a significant implication for current constitutive modelling approaches based on single shear and pressure activation volumes. The implications for refinement of the model are discussed.
FACTORS CONSIDERED IN DARK COLORED WINDOWS AND SIDING Part I - THE COMPLEX COMBINATION OF REQUIRED VINYL PROPERTIES
Jian Wang, Marc Mangnus, Wallace Yau, Willem deGroot, Teresa Karjala, Mehmet Demirors, May 2010
Successful dark colored windows and siding require pigmentation for long-term durability and for solar reflection to avoid excessive temperatures, a durable polymer, limits on coefficient of linear thermal expansion to minimize buckling stresses, formulations with excellent initial and retained impact resistance, and a polymer base with sufficient glass transition temperature and buckling resistance to maintain shape at maximum solar heating for several decades of time.
STRUCTURE-PROPERTY RELATIONSHIPS OF LDPE
Jian Wang , Marc Mangnus , Wallace Yau , Willem deGroot , Teresa Karjala , Mehmet Demirors, May 2010
The molecular structures of high pressure low density polyethylenes (LDPE) are notoriously difficult to characterize due to their highly long-chain branched (LCB) structure. The level and the distribution of the LCBs in LDPE vary with polymerization processes and reactor conditions and these changes may have significant effects on the rheological properties of these resins. A more refined structure ƒ?? property relationship for LDPE is greatly needed. In this study by combining advanced triple-detector gel permeation chromatography with rheological measurements the structure-property relationships of a broad range of LDPEs were investigated. Despite large variations in the molecular weights molecular weight distributions and the molecular structures of the samples some correlations between the solution and melt properties were observed which are consistent with rheological theories.
FACTORS CONSIDERED IN DARK COLORED WINDOWS AND SIDING - PART II - ACHIEVING SUFFICIENT VINYL STIFFNESS IN THE SUN
Rory A. Wolf, May 2010
Successful dark colored windows and siding require several properties discussed in Part I of a companion paper. Two important factors are low coefficient of linear thermal expansion for low thermal stresses and sufficient glass transition temperature to maintain stiffness at maximum solar heating for several decades of time. This work estimates properties for 25 years with additive formulations containing fillers, polymers, polymer blends, and chlorinated PVC. Two promising materials to provide successful properties are a blend of PVC with poly-?ñ-methylstyrene/acrylonitrile/styrene and chlorinated PVC, both filled with talc.
IMPROVING ADHESION PERFORMANCE BETWEEN LOW SURFACE TENSION COMPOSITE AND DISSIMILAR SUBSTRATES
Rory A. Wolf, May 2010
The growing demand for high performance plastic components for automobile aerospace medical and electronic applications has made the job of formulating paints adhesives and coatings more challenging. Composite plastics having low surface energies but which deliver high-strength low-weight performance are becoming more prevalent. Adhesion to the surfaces of these composites as well as between dissimilar high performance materials is being solved by atmospheric pretreatment technologies. This paper links specific atmospheric surface pretreatment improvements in adhesion to an array of composite and dissimilar materials.
EVALUATION OF GATE GEOMETRY AND PROCESSING VARIABLES EFFECTS ON GATE FREEZING TIME BY CFD METHOD
V. Movahednia , M. Mehranpour , H. Nazockdast, May 2010
The aim of the present work was to study the effects of gate geometry and processing parameter on the gate freezing time and quality of the injection molding by using CFD method. The simulation was performed on two different gate geometries Pin and Fan gate for polyacetal. The gate freezing time was predicted on the basis of solidified fraction as a function of time. In the experimental works the gate freezing time was taken as the time which the weight of moldings remained unchanged. From the predicted results it was found that at equal gate cross-section the freezing time of fan gate was shorter than that of the Pin gate. A good agreement was found between the predicted and experimental results.
NON-ISOTHERMAL FILM BLOWING PROCESS STABILITY ANALYSIS BY USING VARIATIONAL PRINCIPLES
M. Zatloukal , R. Kolarik, May 2010
In this work, film blowing stability analysis has been performed theoretically by using minimum energy approach for non-Newtonian polymer melts considering non-isothermal processing conditions with the aim to understand the complicated link between processing conditions, machinery design and material properties.Specific attention has been paid to the investigation of the complicated links between polymer melt rheology (shear thinning, flow activation energy, Newtonian viscosity, melt strength), processing conditions (heat transfer coefficient, mass flow rate, die exit temperature, cooling air temperature) and film blowing stability. It has been found that the theoretical conclusions are in very good agreement with the experimental reality supporting the validity of the used numerical approach and film blowing model.
PHYSICAL AND MECHANICAL PROPERTIES OF HIGH MOLECULAR WEIGHT POLYSTYRENE NANOPARTICLES
Pradip Paik, Kamal K Kar, May 2010
The high molecular weight (MW) polystyrene (PS) particles were synthesized by benzoyl peroxide, sodium lauryl sulfate and styrene. The particle size varies from micro to nanometer. The microscopy analysis (TEM/AFM) shows the spherical shape of PS particles. The effects of particle size, which varies from micro to nanometer scale glass transition temperature (Tg), and mechanical properties were studied. DSC show that the nanoparticles of PS have higher Tg compared to the microsized PS. The elastic modulus of individual nanospherical PS particles is computed from ƒ??force-distanceƒ?? mapping curves of AFM.
THE MANUFACTURE OF CARBON NANOTUBE COMPOSITE MATERIALS USING SUPERCRITICAL CARBON DIOXIDE
Chen Chen , Donald G. Baird , Michael Bortner, May 2010
In order to obtain the unique mechanical, electrical, and thermal properties potentially provided by carbon nanotubes (CNTs) in thermoplastics, it is necessary to reach a well-dispersed level of CNTs. Using a technique in which the CNTs are exposed to supercritical CO2 (scCO2) and then expanded by rapid pressure release, it is revealed by means of SEM that the CNTs exposed to scCO2 at certain temperatures, pressures and exposure time have a more dispersed but aligned structure in a thermoplastic. The stiffness and CNT dispersion of CNTs/RADEL (polyphenylsulfone) composites prepared with the use of scCO2 are significantly improved relative to those prepared by means of direct melt blending.
GAS CHANNEL DESIGN FOR GAS ASSISTED MICRO INJECTION MOLDING
Tobias Villmow, Sven Pegel, Udo Wagenknecht, Petra Pötschke, May 2010
In previous work, gas assist micro injection molding produced significant improvements in the replication of microscale features and elimination of sink marks, but the gas channels were located beneath the features. Thus, the design, location, and size of the gas channels were investigated in this work. Filling simulations were used to evaluate a range of channel designs. For the most promising design, mold inserts were machined and used to injection mold polymethylmethacrylate parts containing microscale features. Molding trials showed that the 3.2-mm diameter channels could be located adjacent to the region with the microscale features and still enhance replication of the features.
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