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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

Extrudate Surface Tearing in Extrusion of Wood Plastic Composites
Velichko Hristov, Elizabeth Takács, John Vlachopoulos, May 2006

In previous publications from this laboratory it was shown that the phenomenon of wall slip occurs with HDPE filled with rice hulls and HDPE filled with wood flour. In the present work, metallocene polypropylene (mPP) was used as a thermoplastic matrix to investigate the extrudate surface tearing of wood plastic composites (WPC). Maple wood flour, mesh 100, was predried and used as filler at 50 wt.% loading. Maleated syndiotactic metallocene polypropylene and a thermoplastic silicon elastomer (TPSE) were employed as coupling agent and polymer processing aid (PPA) respectively to investigate their influence on the extrudate surface tearing.At loadings of 50 wt.% wood flour in the mPP the extrudates come out of the die with significant tearing and surface roughness. Addition of the coupling agent results in considerable improvement of the extrudates appearance, especially at high output rates. At low throughputs, however, the extrudate surface is still rough. It was found that TPSE at low concentrations (1- 3 wt.%) in the coupled 50% filled mPP composite was able to reduce or even completely eliminate the tearing at all throughputs. Likely, the low viscous PPA forms a lubricating layer on the extrudate surface initiating slip at the wall leading to plug-like flow of the melt flowing through the die. Increasing the screw rotation as well as the concentration of the additive yielded better results.

Isolation of True Runner System Behavior in Simulation Tools for Injection Molding
Martin J. Dropik, May 2006

Obtaining accurate results from simulation tools requires that runners be modeled with mesh details that can identify melt variations in critical, high-gradient regions of the diameter. Modeling runners as beam elements or with inadequate refinement across the diameter may not represent the highly sheared outside laminates as they make their way through the runner system into the molded part. As a result, these simulations fail to identify imbalances in fill which occur in even naturally balanced layouts. In this paper, coarse and refined simulations are compared with runner throughput from an injection mold with a balanced layout to verify the ability to obtain accuracy in simulation, identifying concerns encountered in the process.

Parametric Study to Optimize the Processing Parameters and the Physical Properties of Porous PLGA 85/15 Scaffold
J.K. Perron, H.E. Naguib, J. Daka, A. Chawla, May 2006

This study investigates the effects of the processing parameters on the scaffold physical properties. Porous scaffolds of PLGA 85/15 were prepared using a gas foaming/salt leaching technique. The processing parameters included: gas saturation pressure, gas saturation time and NaCl/polymer mass ratio. The physical properties considered were the density and porosity of the scaffold. The average pore size and pore density inside the scaffold were also studied. The results showed that for the samples made of NaCl/polymer mass ratio of 1, leaching all the NaCl was impracticable, and the percentage of open pores was relatively low. It was also found that for the samples made of NaCl/polymer mass ratio of 10 and 15, both the saturation time and saturation pressure did not affect the physical properties of the scaffold. However by varying the size or amount of the NaCl particles into the sample, the physical properties of the scaffold can be tailored.

Cure Kinetics of an Epoxy-Amine Adhesive System by Means of Differential Scanning Calorimetry
Xiaoping Guo, May 2006

The cure kinetics of a medical grade epoxy-amine adhesive is studied under dynamic conditions by means of differential scanning calorimetry (DSC), and analyzed using a generalized autocatalytic model of chemical reaction. It is established that the model can be used to determine the degree of conversion, rate of conversion, and the exothermic heat of cure during any curing process with the use of the classical fourth-order Runge-Kutta numerical method. Also, the cure experiments under various quasi-isothermal conditions have been performed and the heat flows of cure measured as functions of cure times, which are then compared with the model calculations. The above numerical approach, coupled with convenient calorimetric cure measurements under dynamic conditions, provides a convenient and reliable tool for developing an oven-curing schedule of the adhesive in medical device industry.

Using TGA to Determine Carbon Fiber Content in Novel Polymer Composites
Changhui Zhu, Terryann Hoyes, Tony DeGennaro, May 2006

The objective of this work is to use a TGA (Thermogravimetric Analysis) method to quantify carbon fiber in a novel polymer composite such as PEEK (Polyetheretherketone). Other methods, such as electric muffle furnace, acid digestion, FTIR, and GC-MS are either incapable of detecting carbon fiber content from the composite, time consuming, inaccurate, or very expensive.The role of TGA in plastics industry to identify polymer(s) and filler(s) ratio is not widely used. However its importance has grown. Using TGA to quantify the filler that has similar chemical characteristics as the base polymer is always a challenge. This study applies a modified TGA method to determine the ratio of carbon fiber to polyetheretherketone within +/- 2% accuracy.

Rheological Studies on Radiation Modified Polyethylene Resins
Song Cheng, Ed Phillips, May 2006

Radiation modification of polyethylene resins prior to end product conversion has brought about significant improvement of various properties of the resins and products made from them using extrusion based processes where the products are formed in the melt phase at different shear rates and extensional rates. Rheological characterizations including Rheotens measurements, capillary viscosity and melt flow stability were carried out on radiation modified HDPE and LLDPE resins and their un-irradiated base resins. It is shown that electron beam irradiation of the resins has significantly enhanced the melt strength due to long chain branching. This effect would be very beneficial to the processability of the radiation-modified resins for applications that demand higher melt strength.

Ranking of PE Pipe Grades by Cyclic Crack Growth Tests with Cracked Round Bar Specimens
Markus Haager, Gerald Pinter, Reinhold W. Lang, May 2006

It is well known that resistance against slow crack growth is important for the lifetime of pressurized polyethylene (PE) pipes. As a result several methods have been proposed to evaluate the long-term performance of PE using fracture mechanics. It is generally believed that this leads to results more quickly compared to internal pressure tests. In the presented research work a method was implemented using fatigue loading of cracked round bar (CRB) specimens to characterize crack growth resistance. The method was applied to 6 commercially available PE pipe materials and the results were compared with the full notch creep test (FNCT). With both methods the same ranking was found, but it was obvious that FCG experiments were faster by up to two magnitudes, especially when characterizing modern (bimodal) PE types.

Shear-Induced Crystallization of Natural Fiber-Polypropylene Composites
Y. Ruksakulpiwat, U. Somnuk, J. Kleungsumrong, P. Phinyocheep, N. Suppakarn, W. Sutapun, May 2006

Comparative study of shear-induced crystallization among injection molded polypropylene (PP) composites from vetiver grass, rossells, and sisal were examined. Shear viscosity among PP composites from vetiver grass, rossells, and sisal were investigated. Results indicated that the vetiver grass-PP composite had lower Tc, than those of rosells-PP, and sisal-PP composites. The %crystallinity of vetiver grass-PP was higher than those of rossells-PP and sisal-PP composites. However, the normalized thickness of the skin layer in vetiver grass-PP, rossells-PP, and sisal-PP composites showed insignificantly differences. In addition, the effect of fiber content on the normalized thickness of skin layer was elucidated. It was found that an increase of fiber contents led to a decrease in normalized thickness of skin layer and degree of crystallinity of the composites.

The Evolution of Slender Bubbles in an Extensional Flow: Inertial Effects
Moshe Favelukis, Olga M. Lavrenteva, Avinoam Nir, May 2006

The influence of a small amount of external inertia on the evolution of a slender bubble in an extensional flow has been theoretically studied. The unsteady problem is governed by two parameters: The capillary number and the Reynolds number for the external flow. The unsteady shape of the bubble, described by a single partial differential equation, was transformed into a system of ordinary differential equations which was numerically solved. Contrary to the case where inertia is absent and breakup is not possible, a small amount of external inertia, above some critical level, can cause the bubble to break. We found the breakup mechanism to be that of center pinching.

Gradient Libraries of Surface-Grafted Polymers: Combinatorial Tools for Surface Functionality
Chang Xu, Kathryn L. Beers, May 2006

We have developed new fabrication tools that enable us to study optimal properties of grafted polymers. These methods employ microfluidic technology to deliver well-defined mixtures and sequences of monomers to an initiator-functionalized surface. The resulting grafted polymer libraries exhibit gradual, systematic changes in composition, chain length and architecture. Gradients of grafted block copolymer prepared via these techniques reveal composition regimes that switch" their surface properties in response to solvent exposure. Moreover our unique ability to prepare statistical copolymer composition gradients provides comprehensive maps of complex surface chemistry that were previously impossible."

Toward Hydrophilic Polypropylene-Film Surfaces Using Migratory Additives
Siqiang Zhu, Douglas E. Hirt, May 2006

Linear and branched hydrophilic additives of various molecular weights and functional group densities were added to polypropylene (PP) as surface modifiers to make blend films through solution drop coating and heat pressing from melt-blended mixtures. Water contact angles on the film surfaces were measured over time to investigate the additive migration behavior. In particular, PP-additive blend films made through melt blending exhibited lower water contact angles than those made through solution drop coating. Ciba® IRGASURF HL560, linear polyethylene glycols (PEGs) and multi-arm polyethylene oxides (PEOs) were found to generate favorable wettability on the PP films, and all showed loss of durability when immersed in water.

Use of Semihyperbolic Die to Extrude High-Strength Polypropylene Rods
Veronika Habrová, Martin Obadal, Roman ?ermák, Karel Stoklasa, Mušinský Martin, Wilczynski Ond?ej, May 2006

Present work deals with manufacturing and studying of self-reinforced thick-walled isotactic polypropylene products. Self-reinforcement based on flow-induced crystallization was achieved by continuous extrusion under particular flow and processing conditions - high percentage of elongational flow, high pressure and low temperature. The structure and resulting properties of extrudates were subsequently studied. Fibrous and highly oriented morphology, outstanding storage modulus in wide range of temperatures and reasonable thermal stability were found.

The Plastics Engineer as an Expert Witness
Ernest A. Coleman, May 2006

Business and patent laws of the United States are enforced by the criminal and civil courts at both the state and federal levels. The legal process utilizes technical experts such as qualified plastics engineers serving as expert witnesses to help resolve these disputes.This paper is divided into two parts. The first part notes some of the basic responsibilities and qualifications of expert witnesses and the second covers some case histories including the Gore vs. Bush election trial that took place in 2000 in Florida, where a SPE member was an expert witness.There are over a million references on “google.com” to the words ‘federal expert witness qualifications’. Many of the current laws about expert witnesses are based on a 1993 Supreme Court case1, and subsequent court rulings.

A Solution for Warpage in Polymeric Products by Plug-Assist Thermoforming
Hosseini Hossein, Berdyshev Boris Vasilivich, May 2006

Thermoforming process is one of the most popular techniques in the polymer processing. Wide applications of thermoforming are due to its high performance, simplicity, compactness and relatively low-cost equipment. The fundamental defect inherent to the thermoforming technology is warpage of the products during their application which becomes particularly apparent under high temperatures. The warpage defect is understood as the process of non-uniform (heterogeneous) change of the geometric dimensions of products in time resulting in a change (distortion) of their original form. The results of this work allow us to find out the causes of this warpage and ascertain the conditions that give rise to this defect, thereby making it possible to work out valid recommendations for its partial and, in some cases, complete elimination.

Identification of Composite Beam Delamination Parameters
Srinivas Gopal Krishna, Kumar V. Singh, Su-Seng Pang, Guoqiang Li, May 2006

Identification of the delamination in fiber-reinforced composites, often used as aerospace and civil structures, is critical for structural health monitoring. It is well known that such a delamination affects the spectral characteristics (natural frequencies or mode shapes) of these structures. This study aims at developing numerical detection tools for identifying a single delamination in composite beam from its spectral data. The proposed mathematical models of delaminated composite beams will lead to the solutions of novel inverse transcendental eigenvalue problems (ITEP). Numerical techniques are developed here to solve such ITEP. It is demonstrated here that successful identification of damage parameters can be realized with finite number of spectral data set.

Membrane-Mediated Electropolishing
S. Mazur, G.W. Foggin, C.E. Jackson, May 2006

Conventional electropolishing (EP) of Cu involves anodic oxidation and dissolution in a stirred electrolyte solution. Rate and planarization efficiency are governed by diffusion across the stagnant boundary layer. We developed a membrane-mediated electropolishing process (MMEP) in which the substrate is covered by de-ionized water and separated from electrolyte and cathode by a charge-selective membrane. Ion transport occurs by electro-migration of cations across a thin layer of water which is established at the substrate/membrane interface by lubrication mechanics. MMEP provides high removal rates and much higher planarization efficiencies than EP. In addition it consumes no reagents, generates no waste and leaves the substrate uncontaminated.

Influence of Nanofiller Structure on Gas Permeability and Mechanical Properties of Epoxy/?-Zirconium Phosphate Nanocomposites
W.-J. Boo, L.Y. Sun, J. Liu, A. Clearfield, H.-J. Sue, May 2006

The morphology, gas permeability and physical/ mechanical properties of synthetic ?-zirconium phosphate based epoxy nanocomposites with variations in degree of exfoliation are investigated. The state of exfoliation and dispersion is directly confirmed by transmission electron microscopy (TEM) at different locations of the samples. The fundamental structure-property relationship of ?-ZrP reinforced epoxy nanocomposites as a function of degree of exfoliation of ?-ZrP layer structure is discussed.

Film Properties of Cyclic Olefin Polymer
Jungeun Um, Jonghyun Park, Minhee Lee, May 2006

The properties of cyclic polyolefin films manufactured from several processing parameters were investigated. The cyclic polyolefin resin was newly synthesized by LGC in house, and the film was prepared by a solution casting method because of the high glass transition temperature of the resin. The processing parameters such as the peel-off strength were measured at various solvent concentrations for optimizing the film formation. The films having superb optical properties, excellent chemical resistance, low density, and high refractive index were successfully manufactured, and it was found that the films can be used not only for heat resisting film but also for various optical applications including TFT-LCD and lenses.

Electrical Resistivities and Internal Structures of Multiwall Nanotube-Polypropylene Composites Produced with a Continuous Chaotic Blender
B. Kulshreshtha, V. Chougule, D.A. Zumbrunnen, May 2006

A continuous chaotic blender (CCB) has been used in prior work to produce alternating polymer layers with thicknesses below 100 nm, volumetrically align and localize nanoplatelets in multilayers, and assemble carbon black particles into conducting networks. In consideration of the nanoscale dimensions of these novel structured materials, similar processing methods have been applied in this paper to produce electrically conducting networks from a masterbatch of polypropylene (PP) and multiwall nanotubes (MWNTs). Nanocomposites were extruded as films in a continuous, industrially relevant process. Percolation was obtained at the minimum composition considered of 1 wt%. Structure in the nanocomposite films is related to processing conditions and electrical resistivities.

A 3-D Numerical Study on Injection Molding Filling
Sang-Woo Kim, Lih-Sheng Turng, May 2006

This paper presents the development of a threedimensional (3-D) injection molding filling simulation using different algorithms and finite element types. Two numerical models, the mixed model and the equal-order model, were used to solve the Stokes equations with three different tetrahedral elements (Taylor–Hood, MINI, and equal-order). The control volume scheme with the tetrahedral finite element mesh was used for tracking advancing melt fronts. The numerical simulation was validated for the mold filling of a precision optical lens. The numerical simulation agreed very well with the experimental results. As a new application area, a two-step, macro-micro filling approach was adopted for the filling analysis of a part with a micro-surface feature to handle both macro and micro dimensions while avoiding an excessive number of elements. Comparison between the numerical predictions and experimental data suggests that the flow velocity and heat transfer coefficient on the mold surface plays an important role in determining the flow behavior and penetration length within the micro feature.










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