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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

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.

INFLUENCE OF INJECTION MOLDING PARAMETERS ON THE ELECTRICAL RESISTIVITY OF POLYCARBONATE FILLED WITH MULTI-WALLED CARBON NANOTUBES

Tobias Villmow , Sven Pegel , Udo Wagenknecht , Petra Pötschke, May 2010

Polycarbonate (PC) composites with 2 wt% multiwalled carbon nanotubes (MWNT) were injection molded using an experimental design to evaluate the influences of holding pressure, injection velocity, mold temperature, and melt temperature on the electrical resistivity. For both composites variations in resistivity of the molded plates up to six orders of magnitude were found. The highest impact was determined for the injection velocity and the melt temperature. Transmission electron microscopy (TEM) images showed a skin layer with highly oriented nanotubes in case of high injection velocity.

SHRINK FORCE MEASUREMENT OF LOW SHRINK FORCE FILMS

Yi Jin , Theresa Hermel-Davidock , Teresa Karjala , Mehmet Demirors , Jian Wang , Edwardo Leyva , Donald Allen, May 2010

Blends of linear low density polyethylene (LLDPE) and high pressure low density polyethylene (LDPE) are often used to produce films with different shrink forces.The differences in these shrink forces can be observed in practical shrink film applications although it has been difficult to quantify these differences in laboratory equipment. In this work we explore the measurement of shrink forces of low shrink force films by various laboratory methods with examples given of the shrink forces measured on LLDPE/LDPE blends which had proven difficult to measure by other existing techniques.

EFFECT OF TRIACETYL CELLULOSE FILM SURFACE HYDRATION ON THE ADHESION STRENGTH TO POLYVINYL ALCOHOL (PVA) FILM

Hyokap Kim , Juhee Shu , Ho-Jong Kang , Hansung Kim , Jinsik Cho , Yongwon Kim, May 2010

Triacetyl cellulose (TAC) film has been used as a protective film for the polyvinyl alcohol (PVA) based polarization film in liquid crystal display (LCD). Adhesion strength between TAC and PVA films by PVA type adhesive must be maintained sufficiently to keep the dimensional stability of polarized PVA film under severe environmental conditions, such as high temperatures and high humidity. In this study, the surface hydration of TAC film and adhesion process between TAC and PVA films were investigated. The surface hydration of TAC enhanced the adhesion strength between TAC and PVA films. Consequently, this provides better dimensional stability of polarized PVA film protected by TAC film. In addition to adhesion strength, appropriate draw ratio and the crosslinking in PVA film were also required for better dimensional stability in polarized PVA film.

LONG GLASS FIBER ORIENTATION IN THERMOPLASTIC COMPOSITES USING A MODEL THAT ACCOUNTS FOR THE FLEXIBILITY OF THE FIBERS

K.C. Ortman , G.M. Vélez , A.P.R. Eberle , D.G. Baird , P. Wapperom, May 2010

Mechanical properties of long glass fiber composites used in various industrial applications are dependant upon the fiber orientation within the part. To date however simulations with the ability to predict fiber orientation as a function of mold design are not available. In this study several options are explored to predict the orientation of long glass fibers in the concentrated regime that take the flexible nature of these fibers into account. Flow through a center gated disk geometry is simulated numerically for high concentrations of long glass fiber in a polypropylene (PP) matrix. For this a flow uncoupled 2D finite element (FEM) analysis was performed using a discontinuous Galerkin method for the orientation equations. Numerical results based on the uncoupled simulations are compared with experiment for verification.

LONG GLASS FIBER ORIENTATION IN THERMOPLASTIC COMPOSITES USING A MODEL THAT ACCOUNTS FOR THE FLEXIBILITY OF THE FIBERS

K.C. Ortman , G.M. Vélez , A.P.R. Eberle , D.G. Baird , P. Wapperom, May 2010

Mechanical properties of long glass fiber composites, used in various industrial applications, are dependant upon the fiber orientation within the part. To date, however, simulations with the ability to predict fiber orientation as a function of mold design are not available. In this study, several options are explored to predict the orientation of long glass fibers in the concentrated regime that take the flexible nature of these fibers into account. Flow through a center gated disk geometry is simulated numerically for high concentrations of long glass fiber in a polypropylene (PP) matrix. For this, a flow uncoupled 2D finite element (FEM) analysis was performed using a discontinuous Galerkin method for the orientation equations. Numerical results, based on the uncoupled simulations, are compared with experiment for verification.

DEVELOPMENT OF GRUBBSƒ?? CATALYZED COMPOSITIONS AS A SINGLE ƒ??COMPONENT AMBIENT CURABLE BINDER

Chen Wana , Jianxin Feng , Ming-Wan Young , Costas G. Gogos, May 2010

One-component ambient curable liquid compositions have been formulated based on the Grubbsƒ?? catalyzed chemistry to produce in-situ concentrated particulate composites without laminar mixing. The modified Grubbsƒ?? catalyzed compositions containing monomeric reactive ingredients are of much lower viscosity in order to facilitate the infusion step into the packed bed of catalyst-coated particulates. Such formulations are free of complex liquid mixing and precise metering steps required for its twopart binder counterpart resulting in simple and neat net shape manufacturing.

EFFECT OF COPPER ALLOY MOLD TOOLING ON CYCLE TIME AND PRODUCT QUALITY

A L Kelly , L Mulvaney-Johnson , P D Coates, May 2010

The performance of copper alloy mold tool materials in injection molding has been compared experimentally to that of tool steel with respect to cycle time, part quality and energy consumption using in-process monitoring techniques. A mold insert was manufactured from tool steel and in an identical geometry from 4 berylium-free copper alloys, with copper content ranging from 85 - 96%.Results showed that copper alloy mold tools exhibited cooling rates up to 29% faster than conventional tool steel and that cooling rate was directly related to copper content of the alloy. Experimental results were compared to those using a commercial simulation package with boundary conditions at the mold surface being modified according to mold tooling material.