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

Empirical Equations for Predicting Sink Mark Depth in a Rib-Reinforced Plastic Part
Linhuo Shi, Mahesh Gupta, May 1999

Two empirical equations for predicting sink mark depth on the surface opposite to a reinforcing rib in an injection-molded plastic part are presented. Extra thermal mass and effective packing time near a rib base are used as the two determining parameters for calculating the sink mark depth. A normalized geometric sink mark index is used as a measure of the extra thermal mass near the rib base, whereas, the time from the end of filling to the time required for the pressure to vanish near the rib base is used as the effective packing time.

Three-Dimensional Simulation of Plastic Molding Processes
Ruihua Han, Mahesh Gupta, May 1999

Finite element method is used for a three-dimensional simulation of moving boundaries in an inertia-free, incompressible flow. A control volume scheme with a fixed finite element mesh is employed to predict the fluid front advancement. The predicted fluid front advancement and pressure variation in a flow domain similar to the mold cavity used for microchip encapsulation are compared with the corresponding experimental results. Flow simulation for a more complex mold cavity is also presented.

Entrance Flow Simulation Using Elongational Properties of Plastics
Mahesh Gupta, May 1999

A finite element simulation of the flow in a channel with an abrupt contraction is presented. Effects of shear and elongational viscosities of a polymer on the entrance flow is analyzed. The shear and elongational viscosities are represented by the truncated power-law model. The power-law index for the elongational viscosity is independent of the value of the power-law index for the shear viscosity. It is confirmed that Trouton ratio is important in determining the recirculating vortex and the extra pressure loss in entrance flow.

Effect of Elongational Viscosity on Die Design for Plastic Extrusion
Mahesh Gupta, May 1999

A finite element simulation of the flow in a rectangular die with an abrupt contraction is presented. Effect of shear and elongational viscosities of a polymer on the flow in the die is analyzed. The shear and elongational viscosities are represented by a truncated power-law model. The power-law indices for the planar and axisymmetric elongational viscosities are found to have significant effect on the pres-sure and velocity fields in the die.

Characterizing Co-Continuous Polyethylene/Polystyrene Blends
Jianming Li, Basil D. Favis, May 1999

Co-continuous blends of high density polyethylene/polystyrene (PS/PE) have been studied. The influence of a triblock copolymer, styrene-ethylene-butadiene-styrene (SEBS) was also investigated. The surface area, pore diameter and pore size distribution of the blend system after solvent extraction of one of the phases has been measured using a BET nitrogen adsorption technique and mercury porosimetry. Using this technique, it was also possible to generate an emulsification curve, demonstrating the region of interfacial saturation for this complex system.

The Design of Flat Extrusion Dies and Feedblocks
W.A. Gifford, May 1999

Efficient three-dimensional algorithms are now being used routinely in the design of flat extrusion dies and coextrusion feedblocks. The usual assumptions made in 1-D and 2-D analyses (i.e., lubrication approximation, hydraulic radii, geometry shape factors, etc.) are no longer necessary when full 3-D flow equations are solved everywhere in the die or feedblock. How these algorithms are being used to design flat dies (both with or without deflection) and feedblocks is demonstrated through actual examples.

Optical Sensing of Thermoplastics Solidification in an Injection Molding Machine
E. Ramírez Domínguez, W. Ian Patterson, Musa R. Kamal, May 1999

An optical technique for monitoring the solidification of thermoplastics was implemented and studied. A He-Ne laser illuminated the mold cavity through an optical window and a photomultiplier measured the intensity of reflected light during the molding cycle. The light measured is a complex composite of reflection and refraction from crystallites, the mold wall and as many as six interfaces. Polystyrene, polypropylene and high-density polyethylene were used. Further work is required to use this technique for process control purposes.

The Effect of Scale-Up on the Processing Behavior of a Blend Exhibiting Phase Inversion during Compounding
Ram Ratnagiri, Chi-Kai Shih, Chris E. Scott, May 1999

Phase inversion during compounding of low-viscosity ratio polystyrene/polyethylene blends was studied in two different batch mixers. Using a constant maximum-shear-rate as the scale-up criterion, longer mixing times were required in the large mixer due to its lower specific area. A new triangular element blade design was used to obtain different batch sizes in the same mixer. On scale-up with these blades, a constant specific area was maintained and equal mixing times to phase inversion were observed.

Design and Optimization of Three Dimensional Extrusion Dies Using Adaptive Finite Element Method
Mahender P. Reddy, Edward G. Schaub, Louis G. Reifschneider, Harold L. Thomas, May 1999

A numerical algorithm to automatically design polymer extrusion dies is developed. The method uses an adaptive finite element model and shape optimization methodology to define the transition section and the land lengths of a profile die. The ultimate goal of this work is to develop a simulation tool that could be used by extrusion die designers which functions like the CAD-integrated simulation tools available for injection mold designers today.

Processing Effects on Hinge Life of Injection Molded Styrene-Butadiene Copolymers
Vergil H. Rhodes, May 1999

A Designed Experiment was conducted to determine the effects of injection molding processing parameters on hinge life of a styrene-butadiene copolymer. Resin melt temperature, mold temperature, 1st stage velocity, and 2nd stage pressure were varied and mathematically related to the number of flexes required to cause hinge failure. Best hinge life was observed using high melt temperature, high mold temperature, high 1st stage velocity, and low 2nd stage pressure. Some variation in this trend was observed at low melt and mold temperatures.

A Numerical Approach for Optical Characteristics of Injection-Molded Lens
S.Y. Kim, M.H. Rim, W.S. Lim, W.Y. Kim, May 1999

Birefringence distribution of an injection-molded lens is numerically calculated. A simplified numerical approach is proposed that can be used for studying the effect of key molding parameters and evaluating optical property of the lens. Numerical results showed that the melt temperature and holding pressure have significant effects on the optical property of the lens. It also suggested that the holding pressure should be determined with special care to obtain lenses with satisfactory optical characteristics.

Stress Relaxation in Polycarbonate Parts Subjected to Non-Uniform Tensile Stress
Christian Smialek, Amad Tayebi, May 1999

Short-term stress relaxation of polycarbonate parts, with non-uniform tensile stress, is compared to that under uniform tensile stress. The non-uniformity in stress distribution is induced by drilling small holes in the test specimens. The data obtained provide helpful design considerations in pin-type fastening assemblies.

Crack Development around Drilled Holes in Polycarbonate Parts Subjected to Flexural Deformation
Christian Smialek, Amad Tayebi, May 1999

Injection molded polycarbonate parts, with and without small drilled holes, were subjected to a three-point flexural deformation. A special bending test set-up was designed to maximize the exterior fiber tensile strain in the drilled hole zone. The data show a significant change in behavior of polycarbonate under flexural deformation and brittle-like fracture in the drilled hole zone.

Lattice Boltzmann Simulations as a Tool to Examine Multiphase Flow Problems for Polymer Processing Applications
Alexander J. Wagner, Chris E. Scott, May 1999

In this article we give a brief introduction to lattice Boltzmann methods, show why they are a particularly useful tool for the examination of complex multiphase systems and point out their advantages over traditional CFD methods. We present an overview of the method that allows simulation of viscoelastic two component systems, as well as some application of the method to simple model systems.

A New Generation of Materials for the Calendering Industry
Teresa P. Karjala, Brian W. Walther, Alastair S. Hill, Ronald Wevers, May 1999

While polyvinyl chloride (PVC) has been employed in the calendering industry for many years, other polymers have not been as widely used. Ethylene styrene interpolymers (ESI) demonstrate the requisite rheological properties and thermal stability to be successfully used in the calendering process. Commercial scale validations were performed on ESI based formulations. Examples of the applicability of ESI to calendering are discussed.

Viscoelastic Properties of Rotational Molding Resins
Mark Weber, Rod Gonzales, May 1999

The processability of polyethylene for rotational molding applications is dependent on both viscosity and elasticity. Two samples were compared with equivalent viscosities but differing degrees of elasticity. The resin with decreased elasticity had a shorter cook time and rotomolded parts exhibited better physical properties and fewer air bubbles. Further testing is proposed to quantify more clearly the differences in elasticity.

Consolidation of Commingled Glass and Polypropylene Roving
D.J.Y.S. Pagé, P.J. Bates, V.T. Bui, H.W. Bonin, May 1999

Prior to processing, composite materials must be consolidated to allow the formation of a continuous polymer matrix phase and the removal of voids. The composite material studied in this research consists of continuous commingled glass and polypropylene rovings. The consolidation of this material as well as mats composed of unidirectional and woven glass rovings were studied using a specially designed tool mounted on a compression machine. Fiber volume fractions with and without polymer were measured as a function of compressive stress.

Kinetics of Epoxy Curing in Composites Containing Glass Fibers or Glass Fibers Commingled with Polypropylene
Prakaipetch Punchaipetch, Jonathan Reed, Witold Brostow, Nandika Anne D. Souza, May 1999

Glass fibers used in this study are silane-treated woven glass mats and anhydride-treated polypropylene woven glass mats. The influence of these treatments on the epoxy resin curing kinetics is studied. Isothermal and dynamic kinetic parameters from Differential Scanning Calorimetry (DSC) are determined and compared. Based on enthalpies as a function of time results, the autocatalytic model is chosen for the analysis.

In-Line Investigation of Shear-Induced Morphology Transition in Liquid Crystalline Polymer/PET Blends
Fang Qiao, Kalman Migler, Charles C. Han, May 1999

The morphology of a compatibilized polyethylene terephthlate and thermotropic liquid crystalline copolyester blend is investigated via in-line optical microscopy and light scattering. It was found that the droplet-fiber transition in the liquid crystalline polymer is dependent upon the reactivity, the viscosity ratio and the shear field. The fibers are strongly oriented along the flow direction. The formation, deformation and stability of fiber microstructure under different flow conditions are discussed.

Variation of the Self-Nucleation Domains in ABC Triblock Copolymers with Semicrystalline B and C Blocks
V. Balsamo, A.J. Müller, May 1999

The self-nucleation behavior of the polyethylene (PE) block within polystyrene-block-poly(ethylene-co-butylene)-block-polycaprolactone triblock copolymers was investigated. The extent of self-nucleation was found to be highly dependent on the PE content of the copolymers. The self-nucleation was almost completely suppressed when the PE content was 15% by weight.










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