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

Effect of Electron Beam Radiation on the Melt Rheology of Polyvinylidene Fluoride and its Copolymers
Nafaa Mekhilef, Ramin Amin-Sanayei, Stephan Moyses, May 2007

The effect of electron beam radiation on the shear and extensional rheology of polyvinylidene fluoride and its copolymers with hexafluoropropylene is investigated. The samples were exposed to low levels of radiation ranging from 0 to 5 Mrads at room temperature. The shear rheology showed an increase in the storage modulus, as the level of radiation increased while the viscosity at high frequency remained unchanged. These results suggest the formation of chain branching and/or the formation of a second population of higher molecular weight. The results were corroborated using size exclusion chromatography combined with light scattering (SEC-MALLS), which confirmed both the presence of chain branching and the formation of a higher molecular weight tail. Extensional rheology showed strain hardening as the level of radiation is increased.

Effect of Process Conditions on the Micro-Domain Structure and Mechanical Behavior in Cylindrical Block Copolymer Systems
Mohit Mamodia, Alan J. Lesser, May 2007

The effect that different process conditions have on the structural characteristics and the mechanical response of cylindrical block copolymers is investigated. It is observed that structural characteristics such as domain size and spacing change due to different process conditions and thermal treatment. Subtle changes in dspacing (from small angle x-ray scattering) are shown to correlate with the material's stiffness. This change is explained by the temperature dependant segregation between the styrene and rubbery phases at a particular process/annealing temperature.

Filling Balance Optimization by Best Gate Location
Ruggero Baesso, Giovanni Lucchetta, May 2007

The quality of an injection molded part is strongly influenced by the filling balance of the mould cavity. This paper presents a method and the relevant software application to determine the best gate location for an injection molded part. The proposed optimization method automatically and iteratively calculates the gate position that maximizes the melt flows balance during the filling phase. The software is based on the Moldflow Plastics Insight®/Microsoft Visual Basic® interface and uses a non-linear optimization algorithm based on the Gauss-Newton and Conjugated Gradient techniques. The effectiveness of the developed method is demonstrated through some significant case studies.

Solubilities of Blowing Agent Blends
G. Li, S.N. Leung, J. Wang, C.B. Park, May 2007

Investigating the solubility of blowing agent blends in polymer and the phase equilibrium of multicomponents mixture system is a challenge due to the following reasons: (1) the composition ratio in the vapor phase is not the same as the composition ratio of blowing agents dissolved in polymer, and (2) one blowing agent has an effect on the solubility of the other blowing agent. This paper describes the general thermodynamic model that simplifies these investigations. The model is established by measuring sorption with a magnetic suspension balance, and not only predicts the overall solubility for the blowing agent blend but also calculates the solubility of each component dissolved in the polymer melt.

Potential Ultrasonic Compaction of Zein and Distiller's Dry Grain (DDGS)
Julius Vogel, Melissa T. Montalbo, Gowrishankar Srinivasan, David Grewell, May 2007

As the demand for ethanol as fuel additive increases, a consequent rise in the production of distiller's dry grain with solubles (DDGS) and commercial zein is expected. Corn dry milling processing produces two major coproducts; ethanol and DDGS. In wet-milling, pure zein is a high value by-product of corn processing. This study evaluates the potential of ultrasonic compaction of zein and DDGS composites to produce biodegradable biorenewable plastics. Various amplitudes, compaction times and compositions were characterized in terms of tensile strength. It was found that samples could be formed within a few seconds with tensile strengths as high 12 MPa.

Study of Orange Peel Phenomena in Rotational Molding
E. Soos Takacs, M. Emami, D. D’Agostin, J. Vlachopoulos, May 2007

The term orange peel" describes a surface defect that is characterized by irregular grooves and pitting—much like the topography of the outer skin of an orange. Although similar phenomena have been reported for high-pressure processes such as injection molding the root causes of orange peel in rotational molding are essentially unknown. The presence of orange peel is undesirable not only for aesthetic reasons but also for its potential negative effects on the functional properties of the final product.A fundamental study was conducted to determine the root causes of the orange peel in rotational molding. The effects of material properties such as density rheological thermal and powder properties and process parameters were investigated. In addition comparisons are made between the dry blended and melt blended samples in terms of orange peel development."

Melt Blending Graphite into Poly(Ethylene-2,6-Naphthalate)
Hyunwoo Kim, Christopher Macosko, May 2007

Graphite can be an attractive reinforcement for polymers due to its high stiffness and low thermal expansion as well as high electric conductivity. Graphite was melt blended into poly(ethylene-2,6-naphthalate) (PEN). After molding extruded composites into films via biaxial squeezing and uniaxial stretching, their stiffness, thermal expansion and gas barrier properties were tested. Even though graphite in PEN matrix appeared to form unintercalated or partially intercalated morphology, noticeable enhancements in composite stiffness and hydrogen barrier properties were observed. Less improvement in dimensional stability was found. We evaluated average aspect ratios of anisotropic graphite sheets embedded in PEN by interpreting experimental data with composite theories. Young's modulus and dimensional stability of composites were dramatically improved by film drawing.

Impact of Approximating the Initial Bubble Pressure on Cell Nucleation in Polymeric Foaming Processes
Siu N. Leung, Hongbo Li, Chul B. Park, May 2007

According to the classical nucleation theory, the free energy barrier for bubble nucleation and thereby the nucleation rate are functions of the bubble pressure, Pbubble. In computer simulations of polymeric foaming processes, almost all previous research has approximated the value of Pbubble by the saturation pressure, Psat. In this paper, the thermodynamic equilibrium condition and the Sanchez- Lacombe (SL) equations of state (EOS) are employed to determine the value of Pbubble. It is shown that the Pbubble approximation using Psat will lead to significant overestimations of the nucleation rate and the final cell density.

Influence of Surface Energy on Dispersion and Flexural Properties of PS/Phosphonium Organoclay Nanocomposites
Jorge Uribe Calderon, Musa R. Kamal, May 2007

Phosphonium-modified montmorillonite (PMM) organoclays were used to produce polystyrene (PS)/clay nanocomposites by melt processing. Two PS resins with different molecular weights were used, along with four different PMM organoclays. The structure of the resulting nanocomposites was characterized using wide angle X-ray and transmission electron microscopy. It was found that the quality of clay dispersion, nanocomposite thermal stability, and flexural mechanical properties depend on the combination of organoclay type and PS molecular weight. The differences are discussed in light of the interfacial tension values measured for the different PS/PMM systems.

Fast Acquisition Melt Pressure Measurements to Detect Flow Instabilities. A New Option for Capillary Rheometers
A. Göttfert, J. Sunder, May 2007

Flow instabilities cause various problems in extrusion blow- or flat film processes. Especially shark skin is affected by the molecular structure. This phenomenon is analyzed in various scientific works using apparatus that are complex or difficult in operation.A new set-up, now available is being presented as an option for new and existing capillary rheometers, consisting of a special designed die and a fast responsive transducers system. The software allows the evaluation of diverse pressure frequency regimes causing flow instabilities. Measurement examples are given for different shear rates and polymers. The measured frequency regimes are related to molecular parameters.

Casting of Zein Protein Polymers
Gowrishankar Srinivasan, Michael Kessler, David Grewell, May 2007

This paper reviews an investigation of the processability and properties of commercially available corn protein polymers for cast film products. Different formulations of protein substrates were cast and characterized for their mechanical properties. In this study it was seen that zein plastic sheets could be cast with tensile strengths as high as 6 MPa with a strain to failure of 6%. In addition, ultrasonic treatment of the solution, prior to casting, reduced the tensile strengths; however, the treatment did enhance the strain to failure to as high as 200%. Lastly, the addition of nanoclays also reduced the tensile strength of the cast films.

Preparation of Gold Nanoparticles Filled Poly Dimethyl Siloxane Membrane for Gas Separations and its Reverse Selective Phenomena
R.Vedaiyan, C.Banerjee, Jag Sankar, J.Lou, May 2007

A novel nanocomposite membrane, poly dimethyl siloxane (PDMS)/Au was prepared for carbon dioxide/methane separation. Synthesis of stabilized nano particles is also reported. The nanoparticles were characterized by UV-visible spectroscopy and transmission electron microscopy (TEM). The hybrid membrane was characterized morphologically by scanning electron microscope (SEM) and the change in inter-segmental distance due to filler loading by wide angle X-ray diffraction patterns (WAXD). The gas transport properties were measured at different pressures and temperatures. The effects of filler loading on permselectivity, diffusivity selectivity and solubility selectivity are reported for CO2/CH4 separation. Reverse selective phenomena of PDMS/Au nanocomposite membrane over the conventional PDMS membrane is explained based on sorption kinetics of CO2.

Viscoelastic Flow in Micro-Injection Molding
Xin Hu, Chuntai Liu, Guojun Xu, L. James Lee, May 2007

Understanding the free surface flow of viscoelastic fluids in micro-channels is important for the design and optimization of micro-injection molding processes. In this paper, flow visualization of a non-Newtonian polyacrylamide (PA) aqueous solution in a transparent polymethylmethacrylate (PMMA) channel with microfeatures was carried out to study the flow dynamics in micro-injection molding. The transient flow near the flow front and vortex formation in microfeatures were observed. Simulations based on the control volume finite element method (CVFEM) and the volume of fluid (VOF) technique were carried out to investigate the velocity field, pressure, and shear stress distributions. The mesoscopic CONNFFESSIT (Calculation of Non-Newtonian Flow: Finite Elements and Stochastic Simulation Technique) method was also used to calculate the normal stress difference, the orientation of the polymer molecules and the vortex formation at steady state.

Novel PET Nanocomposites with Enhanced Barrier Performance of Interest in Food Packaging Applications
M.D. Sanchez-Garcia, E. Gimenez, J.M. Lagaron, May 2007

PET is one of the polymers most widely used in the packaging industry. However, it is highly desirable to enhance its barrier properties for applications such as carbonated drinks and for other rigid and flexible packaging applications. The nanocomposites route offers unique possibilities to enhance the properties of this material, provided that adequate thermally resistant and legislation complying nanofillers are used. This paper presents novel nanocomposites of PET with enhanced barrier properties to oxygen, water and d-limonene based on a new specifically developed food contact complying montmorillonite grade. Morphology and thermal properties are also discussed as a function of filler content.

An Examination of the Relative Impact of Common Potable Water Disinfectants (Chlorine, Chloramines and Chlorine Dioxide) on Plastic Piping System Components
Sarah Chung, Ken Oliphant, Patrick Vibien, Jingguo Zhang, May 2007

The three most common disinfectants in potable water are chlorine, chloramines and chlorine dioxide. While these disinfectants are all oxidants, their unique characteristics can result in a significantly different impact on the performance of plumbing system components. In this paper, the chemistry and characteristics of the oxidants are discussed in the context of oxidative degradation of plastic piping system components. Testing strategies to ensure material performance in potable water applicationsare presented and reviewed.

Evaluation of Alternative Injection Locations with Variability Consideration in an Automotive Part
Thania Gaído, Narayan Bhagavatula, José M. Castro, May 2007

Selecting proper process settings is crucial in injection molding as part quality is greatly influenced by the process conditions. The locations of the injection gate need to be decided before the mold is made. Other processing variables can be adjusted during start up; however changing the gate location at a later stage involves great cost. In this work, we analyze the effect of gate location on process consistency for an automotive part, using a multivariable optimization method called Data Envelopment Analysis (DEA).

Effect of E-Beam Sterilization on the Physical and Optical Properties of Medical Plastics
Gary M. Stack, Ken Breeding, May 2007

Electron beam (E-beam) exposure is becoming increasingly popular as a lower cost alternative for the sterilization of medical devices and rigid medical packaging. The objective of this study was to determine the effect of E-beam sterilization on several plastics typically used in medical devices and packaging including: copolyesters, polycarbonate, acrylic and cellulosic polymers. Exposures of 25 and 50 kGy (2.5 to 5.0 Mrad) were found to induce significant yellowing. However, color measurements performed at various intervals subsequent to the exposures indicated that the yellowing decreased over time, each plastic to a different degree. Effects of these E-beam exposures on physical properties of these plastics were also determined.

Process Optimization of Injection Molding by Integrating Numerical Simulation with Surrogate Modeling Approaches
Jian Zhou, Lih-Sheng Turng, May 2007

An integrated optimization system that can adaptively and intelligently determine the optimal process conditions for injection molding has been developed. Nonlinear statistical regression techniques and design of computer experiments are used to establish adaptive surrogate models that can substitute time-consuming numerical simulation and quickly provide predictions with adequate accuracy for system-level optimization. While the Gaussian process (GP) surrogate model is being refined, a multi-objective genetic algorithm (GA) is employed for the global optimal solutions in a concurrent fashion. The performance and capability of various surrogate modeling approaches—i.e., Gaussian process (GP), artificial neural network (ANN), and support vector regression (SVR)—are also investigated and compared in terms of accuracy, robustness, and efficiency. The examples presented in this paper show that the adaptive optimization procedure helps engineers determine optimal process conditions more efficiently and effectively.

An Examination of Field Failures of Plastic Piping System Components in Potable Water Applications
Sarah Chung, Tony Kosari, Tieqi Li, Ken Oliphant, Patrick Vibien, Jingguo Zhang, May 2007

Disinfectants in potable water, such as chlorine and chlorine dioxide, can impact the performance of plastic piping system components. In this paper, field failures of plastic piping components exposed to potable water are examined. Analysis of the oxidative and mechanical initiation and propagation mechanisms leading to failure is performed. Field and laboratory samples are also compared to assess the test methodologies that are available to evaluate the impact of disinfectants on plastic piping systems.

Mathematical Model and Numerical Analysis of Polymer Melt Flow and Heat Transfer in a Cooling Extruder
Lilac Cuiling Wang, Markus Bussmann, Chul B. Park, May 2007

This paper presents a mathematical model and numerical analysis of momentum transport and heat transfer of polymer melt flow in a standard cooling extruder. The finite element method is used to solve the three-dimensional Navier–Stokes equations based on a moving barrel formulation; a semi-Lagrangian approach based on an operator-splitting technique is used to solve the heat transfer advection–diffusion equation. A periodic boundary condition is applied to model fully developed flow. The effects of polymer properties on melt flow behavior, and the additional effects of considering heat transfer, are presented.

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