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
Influence of Temperature, Molecular Weight and Molecular Weight Dispersity on the Surface Tension of Polystyrene (PS): Experiment and Theory
José Carlos Moreira, Nicole Raymonde Demarquette, May 2000
In this work, the influence of temperature, molecular weight (Mn) and molecular weight dispersity (MWD) on the surface tension of polystyrene (PS) was evaluated using the pendant drop method. The discrete interface cell model (DICM) theory was used in conjunction with the Flory, Orwoll, and Vrij (FOV) equation of state theory to predict surface tension (?) with bulk pressure-volume-temperature (PVT) data. It was shown that surface tension of PS decreases with increasing temperature for all PS studied. The surface tension of PS increased when the molecular weight of polystyrene was varied from 3,000 to 40,000. When the molecular weight of PS was further increased the surface tension was shown to level off. The surface tension was shown to decrease with increasing molecular weight distribution. The theoretical predictions of DICM theory corroborated with the experimental results as far as the influence of temperature, molecular weight was concerned.
Ultrasonic Absorption in Rubber Filled Epoxies
K. Gabriel, S. Petrie, May 2000
Mechanisms of sound absorption in rubber toughened epoxies were studied. The general mechanisms of sound absorption in plastics were reviewed. Design of experiment principles were used to develop an experimental regime to investigate the impact of density, glass transition temperature of the rubber phase, and volume percent loading of rubber particulate on sound absorption. It was found that maximum sound absorption occurred in materials with high loadings of low glass transition temperature, rubber particulate whose acoustic impedance was very different from the host matrix.
Effects of Magnesium Hydroxides on the Physical Properties of a Semirigid PVC Used in Wire Coating
Jeffrey A. Torone, Stephen Petrie, May 2000
This is a study of ductility and smoke generation of Polyvinylchloride (PVC) with different smoke suppressants (SS). These smoke suppressants consisted of Magnesium Hydroxide (Mg(OH)2) and Alumina Trihydrate (ATH). It was found that the amount of smoke generated (SG) during the tests, decreased when the outer layer of the test samples were removed. The smoke generation and physical properties were analyzed to determine which smoke suppressant was best. No chemical versus physical correlations were found.
Simulation of CaCO3 Dispersion in a PP Matrix during Twin Screw Extrusion
Pierre G. Lafleur, Françoise Berzin, Miroslav Grmela, Bruno Vergnes, Sebastien R. Tremblay, May 2000
Compounding of highly filled minerals in polymeric matrix has never been an easy task. This work deals with the simulation of CaCO3 (25 and 50 % wt.) dispersion in a PP matrix during twin screw extrusion. Based on a kinetic model of agglomeration/breakup of the filler, we were able to pin point the effect of twin-screw operating conditions on dispersion. Experimental work has been done to validate the model and evaluate kinetics constants.
Analysis of Polypropylene Behavior at Constant Load below the Elastic Limit
Alejandro Hernandez-Luna, Nandika A. D'Souza, May 2000
Polypropylene dog-bone samples have been tested using creep-recovery analysis at different stress values in order to determine the behavior of the material in the elastic region. It has been found non-linear behavior in the sample at values under the elastic modulus at the elastic region. It has been also found, by means of calorimetric analysis, that creep test affected the material, promoting changes in crystallinity in the tested samples. These effects are important in the performance of the material in time.
Computer Aided Design for Rotationally Molded Parts
John Fawcett, May 2000
3D Cad software is improving new product development in many plastic fields including rotational molding. These improvements are leading to better products that are developed faster with fewer down stream changes. Because a 3D Cad electronic file gives a more complete design that can be viewed as a 3-dimensional model or represented as a 2D drawing, everyone involved with the project has a better understanding of the final product. Some features of 3D Cad can improve the development process in ways that are unique to rotationally molded products. The use of 3D Cad is also creating new opportunities for the use of rotationally molded products because tighter tolerances can be achieved when the 3D electronic file is used to create the tooling models and/or molds.
The Role of Phosphites in Stabilization of Non-Polyolefin Polymers
Henry C. Ashton, William Enlow, Tim Nelen, May 2000
The use of organophosphites as stabilizers for polyolefins has been well described and documented(1). This paper deals with the use of phosphites as stabilizers in non-polyolefin applications such as PVC and also in condensation polymers e.g. Polyesters, polyamides, and polycarbonates. A key point in understanding the application of phosphites in such materials is that the process of polyolefin thermooxidative degradation begins with thermomechanical scission of a carbon-hydrogen bond that yields a polymer based macroalkyl carbon-centered free radical. This free radical is highly reactive with molecular oxygen yielding a peroxy radical which can by interaction with the polymer substrate generate other free radical species such as alkoxy radicals and the highly detrimental hydroperoxides (see Figure 1).
Influence of Thermal History and Molecular Weight on the Mechanical Properties of High Density Polyethylene
C. Albano, R. Sciamanna, G. Delgado, D. Kaiser, May 2000
Several variables affect the plastics solidification process, being the thermal history given to the polymer and its molecular weight the more important. Therefore, this paper is mainly aimed at establishing a relationship between thermal history, mechanical properties and molecular weight of HDPE based on mathematical models of the following type: mechanical property =f(molecular weight, crystallinity) through a multivariable non-linear regression method and three-dimensional views of the surfaces generated by the mathematical expressions were obtained to have a better view of the results and models developed, concluding that these models are very useful for the industry.
The Use of Thermomechanical Indices to Establish Straightforward Processing-Mechanical Properties Relationships
J.C. Viana, A.M. Cunha, N. Billon, May 2000
The thermomechanical environment imposed to the melt in injection molding is quantified by two thermomechanical indices estimated from computer simulations of the mould filling. These indices are associated to the onset conditions of the microstructure development, and aim at interpreting its final state. As the microstructure determines the mechanical properties, straightforward relationships between those and the thermomechanical indices can be obtained. In this work, axisymmetric specimens were injection molded with systematic variations on the melt and mold temperatures and the flow rate. The mechanical properties were assessed in tensile tests at cross-head velocities of 2, 10, 500 mm/min and 3 m/s. They were related to the thermomechanical indices. Their variations were interpreted in terms of the expectable microstructure of the moldings.
Rubbing Mechanisms of Polymers on Metal Surface Relevant to Extrusion
Hyun Seog Kim, Chan I. Chung, Thomas I. Butler, May 2000
The processing behavior of a polymer inside an extruder largely depends on the rubbing mechanism of the polymer on the metal surfaces of the barrel and the screw. The rubbing mechanisms of five commercial polymers were investigated from a metal temperature below the thermodynamic melting (or glass transition) range of each polymer to a metal temperature well above the melting range. The rubbing mechanism was found to depend on the polymer properties and the metal temperature. For rigid, amorphous or highly crystalline polymers, the rubbing mechanism is friction" at low metal temperatures below the melting range and "melting" at high metal temperatures above the melting range. For soft crystalline polymers with a broad melting range the rubbing mechanism is complex exhibiting "friction" "tearing" and "melting" as the metal temperature is increased."
Through-Transmission Infrared Welding (TTIR) of Teflon TFE (PTFE)
Robert A. Grimm, May 2000
Through-transmission infrared (TTIR) welding of Teflon®TFE using a Teflon®PFA interlayer was demonstrated to be a well-controlled process that resulted in strong joints. The interlayer was formulated with low levels of carbon black to increase its absorption of the infrared radiation. Designed experiments were used to provide some understanding of important factors.
Methods for Making Nearly Invisible Welded Joints in Clear Polymers
R.A. Grimm, B. Christel, J. Robinson, May 2000
Several ways are described to produce very nearly invisible joints in two transparent polymers. Particles of optically opaque materials can be embedded or deposited on the surfaces of clear acrylic or other polymers through grit blasting, printing processes, use of very lightly colored inter-layers, or spraying/ink deposition. High weld energies such as are found in YAG lasers or xenon heating systems are very capable of producing nearly invisible joints. Light colors other than clear can be welded in this manner as well.
Influence of Mica and Talc Fillers on the Properties of Rotationally Moulded LLDPE
A. Robert, J.F. Orr, R.J. Crawford, May 2000
This paper describes the results from an investigation of the effects of talc and mica on the properties of rotationally moulded Linear Low Density Polyethylene (LLDPE). This work concentrates on the effects of the particle sizes and the types of coupling agent. Results show that introducing finer grades of talc and mica improves the impact strength. It has also been found that a maleic anhydride modified polyethylene can achieve better overall properties than a titanate-coupling agent.
Real-Time Dielectric Measurements during Extrusion of Filled Polymers
Michael McBrearty, Anthony Bur, Stephen Roth, May 2000
Mineral fillers are added to polymers to extend and modify physical properties, and their concentrations should be carefully controlled to obtain the desired end-use properties. To achieve this control, real-time measurements are very useful. Previous work has shown that in-line dielectric sensors can measure the concentrations of fillers in non-polar polymers. This work extends the measurements to polar polymers.
Investigation of Crystalline Structure and Orientation of Polyamide 612 in Double Bubble Tubular Film Blowing Process
Sangkeun Rhee, James L. White, May 2000
Uni- or biaxially oriented polyamide 612 (=PA612) films were produced by a double bubble tubular film blowing process at a high extrusion temperature and with a rapid cooling of the first bubble films. The double bubble films stretched in a rubbery state were characterized using differential scanning calorimetry (DSC), wide angle X-ray diffraction (WAXS), small angle X-ray scattering (SAXS) and infrared (IR) spectroscopy. Biaxial orientation factors were computed with pole figure data and plotted in a White-Spruiell orientation triangle. DSC measurements showed that first bubble films exhibited a spontaneous increase in glass transition temperature (Tg), cold crystallization temperature (Tc) and crystallinity during aging at room condition (22 °C and 32 %RH). Highly biaxially stretched films had a well defined triclinic crystals when they are annealed in a boiling 20% formic acid solution or stretched at a high temperature. Structural parameters of crystals exhibited a big change with stretching conditions.
Structure Development in Biaxial Stretching of Cast Polyamide 11
Sangkeun Rhee, James L. White, May 2000
The development of crystallinity and polymer chain orientation in the biaxial stretching process of cast polyamide 11 (PA11) films was investigated. The characterization of the stretched films was done with birefringence measurements, wide angle X-ray diffraction (WAXS), differential scanning calorimetry (DSC) and small angle X-ray scattering (SAXS). Biaxial orientation factors were represented in a White-Spruiell orientation isosceles triangle. As distinct from polyamide 6 (PA6) and polyamide 612 (PA612), DSC scanning of as-cast PA11 film were crystalline and exhibited a little change in crystallinity by aging at room condition. The glass transition temperature (Tg) increased during aging. PA11 highly biaxially stretched in an elevated temperature had monoclinic and triclinic crystals, respectively. The dimensions of the crystals were changed with the stretching conditions.
Block Copolymers as Templates for Functional Materials
Robert E. Cohen, May 2000
There are applications and devices which require controlled distribution of material functionality (electrical, optical, catalytic, magnetic) in two or three dimensions. At the nanometer length scale, attempts to meet this challenge have included template-mediated materials chemistry (Martin 1994) in which track-etched membranes, porous alumina and zeolites serve as the nanoscale reaction vessels for the synthesis of the functional materials. The ability to control both the length scale and the spatial organization of block copolymer morphologies makes these materials particularly attractive candidates for use as templates in the synthesis of functional nanocomposites. Appropriate choices of the repeat units of the block sequences renders them capable of selectivity sequestering preformed inorganic nanoclusters or selectively solubilizing inorganic reagents for in-situ cluster synthesis. Methods exist to produce nanoscale voids which percolate through the structure, leading to processes which coat or backfill the channels with functional materials. Electroless plating methodologies which have been used to apply surface of metals to polymer films can be adopted to produce metallic structures selectivity within block copolymer domains.
Tensile Properties of Linear Low Density Polyethylene (LLDPE) Blown Films
Rajendra K. Krishnaswamy, Mark J. Lamborn, May 2000
Various LLDPE resins that encompass those polymerized using Ziegler-Natta, metallocene and chromium oxide based catalysts were blown into film and their tensile properties were investigated in relation to molecular orientation. The direction-dependent (MD vs. TD) tensile properties were observed to be significantly different from those of isotropic polyethylene specimens of comparable density. These were explained in terms of orientation and lamellar organization features. Excellent correlation between Elmendorf tear and tensile yield characteristics added credibility to previous hypotheses that specimen stretching and its associated microstructural deformations plays a significant role in Elmendorf tear tests.
Blends of Metallocene Polyethylenes for Recycling of Xerographic Toners
Hui Tang, Charles L. Beatty, May 2000
This paper presents experimental results on the blends of metallocene polyethylenes (mPE) for recycling of xerographic toners by reactive extrusion. The experiments were carried out in a reactive twin screw extruder. The evaluation of the mechanical properties and morphology for different blend consist of black xerographic toners with mPE with and without compatibilization by reactive processing. It is rather surprised that the impact strength property is synergistic behavior. The impact strength and the modulus of elasticity of the blends using compatibilizer can be significantly improved. Morphology studies employed scanning electron microscopy (SEM) show that not only the domain size of the phase of black toner can be reduced but also the interfacial adhesion can be enhanced by proper compatibilizeation. Phase morphology and domain size indicate that efficient dispersion was obtained for the compatibilized system whereas the phase of black toner was agglomerated in the interfaces without compatibilization.
Integrating Thin-Wall Molder's Needs into Polymer Manufacturing: Part II
W.G. Todd, T.J. Schwab, D.L. Wise, May 2000
Polyethylene (PE) injection molded rigid containers are widely used for food packaging and promotional drink cups. Molders of these containers have well-defined processing needs and molded part requirements. Likewise, the polymer manufacturer has well-defined manufacturing and analytical methods for characterizing resin properties. This paper presents a predictive model that was developed from molded part testing versus PE resin physical properties. Utilizing this information, the resin producer and the injection molder can work together to improve molded part performance.


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