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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Entrance Flow Simulation Using Elongational Properties of Plastics
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
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
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.
Orientation Studies of Microbial Polyesters at the Air-Water Interface
The orientation of organic thin films of natural polymers of microbial origin was studied with the aid of LangmuirBlodgett films and x-ray reflectivity. The polymer system studied included a number of polyhydroxyalkanoates, a family of microbial polyesters which include both thermoplastic and elastomeric materials and which have previously been shown to form stable monolayers at the air-water interface. The spreading behavior of each polymer was studied and the orientation of the polymer following transfer to a substrate was determined using x-ray reflectivity.
The Design of Flat Extrusion Dies and Feedblocks
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
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.
Property/Processing Enhancement via Improved Low-Temperature Fusion for Rigid PVC Construction Products
Impact property development in RPVC construction products is highly dependent on the type of impact modifier used and its contribution to processing. With increasing attention being paid to all aspects of production, particularly machine utilization and cost effectiveness of raw materials, maintaining performance properties remains critical. This study discusses how impact modifier selection can influence processing and the levels of other ingredients, and through these effects, influence the performance properties of articles like siding and window profile.
The Effect of Scale-Up on the Processing Behavior of a Blend Exhibiting Phase Inversion during Compounding
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
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
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
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
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
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
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
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
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.
Morphology and Mechanical Property of Poly(Phenylene Oxide) Modified Polypropylene Blends
Morphology and mechanical behavior of isotactic polypropylene (iPP) and Noryl poly(phenylene oxide) (Noryl PPO) blends were studied. Large PPO particle sizes and wide size distribution were found in the iPP/PPO blends if no compatibilizers were added. The addition of a compatibilizer tremendously improved PPO particle dispersion and particle-matrix interfacial adhesion in PP. This, in turn, greatly improves the fracture toughness of iPP. The results showed that phase morphology has a significant effect on the mechanical performance of these blends.
VT-Drifts Studies of Polymer Thermal Decompositions
Polymer thermal analysis by using variable temperature diffuse reflectance Fourier transform infrared spectroscopy (VT-DRIFTS) is described. Structure-specific information derived from non-isothermal VT-DRIFTS employing ramp and step heating profiles are compared. Techniques for correlating polymer solid-state structure with infrared spectral features and for distinguishing between reversible and irreversible temperature effects are described. Specific examples of using VT-DRIFTS analysis for characterizing the thermal decomposition mechanisms of poly(styrene)and a nitro-aromatic polymer are given.
Consolidation of Commingled Glass and Polypropylene Roving
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.
The Measurement of Thermoset Cure Properties with a Novel Rheometer
The measurement of thermoset cure properties on very hard materials such as epoxies is very difficult especially if they are coated onto a fabric. The application of a new parallel plate rheometer allows the measurement of such cure properties in one simple test. The sample is held firmly in a sealed and pressurized sample chamber. The dies are directly heated resulting in improved repeatability and resolution of gel and cure times. A robust torque transducer allows direct measurement of the final shear modulus in materials. Examples of cure tests are presented for several thermosets.
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