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

Dynamic Light Scattering Method for Determination of Shelf Stability of Liquid Colloidal PVC Stabilizers
Michael H. Fisch, Radu Bacaloglu, May 2000

Many liquid mixed metal stabilizers are colloidal microemulsions of water in oil. Their shelf stability is a function of the diameter of microemulsion droplets. Microdroplets with a diameter less than 50-60 nm and low tendency to aggregate are shelf stable. A fast procedure for estimation of shelf stability of liquid stabilizers for PVC based on determination of microdroplet diameters was developed.

Sharksin Melt Fracture in High-Performance Hexene-LLDPEs
Harry Mavridis, Ramesh Shroff, May 2000

Several types of High-Performance Hexene (HPH)-LLDPE have been introduced in recent years for high-strength blown film applications, with substantial enhancement of film properties over conventional Ziegler-Natta LLDPEs. The present work is a study of the comparative behavior of the various types of LLDPEs under processing conditions designed to induce sharkskin melt fracture (SSMF). Both capillary rheology and blown film studies were conducted. The ability of capillary rheology to capture the difference between resins in terms of their relative tendency to sharkskin melt fracture was investigated in parallel with blown film studies at different shear rates and die gaps. Film blowing is more effective in discriminating between resins and identifying melt fracture tendency. The influence of sharkskin melt fracture on the film properties was also quantified, showing the film impact strength to be affected most sensitively, and negatively, by the presence and severity of sharkskin melt fracture (SSMF).

Structure-Property Characteristics of Ethylene/1-Hexene Copolymers with Tailored Short Chain Branching Distributions
Colin Li Pi Shan, Kyung-Jun Chu, João B.P. Soares, Alex Penlidis, May 2000

Recently, we have developed a metallocene catalyst system that can produce polyethylene and ethylene/a-olefin copolymers with tailored molecular weight and short chain branching distributions. Ethylene/?-hexene copolymers produced with this system have narrow molecular weight distributions as expected from metallocene catalysts. However, these copolymers are quite unique in that their short chain branching distributions are broad and sometimes bimodal, similar to Ziegler-Natta LLDPE. To examine the effect of these broad short chain branching distributions on the polymer properties, tensile and viscosity characteristics were measured. It was found that the tensile properties of these broad distributions could be controlled by the relative amounts of each species. In this study, the best tensile properties were achieved with a distribution that contained a large proportion of crystalline material and a small fraction of lower crystalline material. It was also found that the distribution of short chain branches can have an effect on the viscosity behaviour of these copolymers.

Superstructures in Polyamide Elastomers-The Key for Super Performance?
Joerg Lohmar, May 2000

Polyether block amides are known as thermoplastic elastomers with excellent chemical resistance, outstanding physical properties, and easy processing. This is closely related to the type of chosen polyamide blocks and the morphology of crystalline and amorphous phases. In contrast to other multiblock thermoplastic elastomers which are forming only net points of crystallized polyamide blocks polyether block amides exhibit a spherolithic superstructure of crystallized lamellae. As a consequence there is an intrinsically reinforcing effect in the material depending on block composition which is reflected by a unique mechanical behavior which will be discussed in the paper.

HDPE Blending Technology for Enhanced LDPE Film Properties
Rick F. Tate, Gerry Landvatter, James V. Krohn, Matt Dawe, May 2000

Numerous blown film applications involve the blending of high density polyethylene (HDPE) with low density polyethylene (LDPE) to achieve desired physical properties. For example, HDPE blended with LDPE provides greater stiffness and holding power for product retention in shrink films. HDPE/LDPE blends are also used in sanitary paper packaging applications, with the HDPE component providing needed stiffness for high speed machinability. Likewise, a variety of other packaging applications utilize HDPE/LDPE blends for improved machinability, especially as downgauging opportunities are pursued. This paper documents the effect of HDPE resin choice and content on the strength, optical and shrink properties of LDPE/HDPE blown films.

Numerical Simulation of Blown Film Cooling
V. Sidiropoulos, J. Vlachopoulos, May 2000

Commercial blown film production is often limited by the rate of cooling that can be achieved in the production line. The flow of the cooling air around the curved bubble is characterized by rather complex aerodynamics. Even for the same air ring design, different set-ups (adjustable air rings) produce significant differences in the air-flow pattern. Numerical simulation suggests that heat transfer rates are affected by all these parameters. Additionally, numerical simulation in the film phase reveals large temperature gradients across the film thickness in the area where the film is emerging from the die.

Fatigue Behavior of Discontinuous Glass Fiber Reinforced Polypropylene
Mustafa Sezer, Ahmet Aran, May 2000

The fatigue properties and mechanism of 30% wt. short glass fiber reinforced chemically coupled and uncoupled polypropylenes were determined. Depending on the degree of damage, debondings effect the load transfer to the fibers. Final fracture occurs if the number of non-loaded fibers in one cross-section increases up to the critical value. When the fatigue data was presented as S-N curves, both materials have not showed any endurance limits. The microstructural mechanisms were discussed by help of SEM observations.

Numerical Simulation of Bi-Layer Extrusion Flow within a New Conical Extruder
Alp Sarioglu, Daniel Schläfli, André Luciani, Jan-Anders E. Månson, May 2000

In this study, the coextrusion flow in the die section of a new type of multi-layer extruder is determined. The prototype extruder used is based on a conical rotor-stator assembly. The extrusion of a range of individual layers of PEs was investigated. Numerical simulation, based on an axisymmetrical model of the assembly using an inelastic fluid model, was used to analyze the flow behavior.

Freeze-Thaw Durability of Composites for Civil Infrastructure
J. Haramis, K.N.E. Verghese, J.J. Lesko, May 2000

Freeze-thaw durability is a critical area that needs to be investigated prior to implementing composite material use in civil infrastructure. This work will examine the performance of pultruded vinylester/glass and epoxy/glass cross-ply laminates in different aging environments. Tensile test data encompassing strength, stiffness, and strain-to-failure on as-received" and moisture saturated material will be presented as well as saturation moisture uptake data. Discussion of continuing experimental work related to freeze-thaw cycling will also be addressed."

The Hydraulic Permeability of Dual Porosity Fibrous Preforms
B. Markicevic, T.D. Papathanasiou, May 2000

We present a computational analysis of viscous flow through arrays of fiber bundles using the Boundary Element Method (BEM) implemented on a multi-processor computer. Up to 700 individual fibers are included in each simulation. These are simple but not trivial models for fibrous preforms used in composites manufacturing - dual porosity systems characterized by different inter- and intra-tow porosities. The way these porosities affect the hydraulic permeability of a preform is currently unknown and is elucidated through our simulations. Numerical results are compared to analytical models. Through a large number of simulations we construct a master curve for the permeability of arrays of fiber bundles for various packing arrangements.

The Development of a Consumable Container for Built up Roofing Asphalt
Donn R. Vermilion, Jorge A. Marzari, May 2000

An injection molded container has been developed for built up roofing asphalt. The container is consumable in the roofer's kettle unlike the paper carton it supplants. The development of the container consisted of three elements. The first element was the development of a compound that could be injection molded, withstand filling with molten asphalt, and later melt completely in the roofer's kettle. The second element was the design of a container that met processing, cost and customer requirements. The third element was the development of a cost-effective injection molding process.

Minimizing Sandwich-Panel Warpage
James S. Griffing, May 2000

Honeycomb-cored composite sandwich panels are widely used in commercial airplane interiors. Sandwich-panel warpage can cause assembly difficulties and has been a deterrent to implementation of determinant assembly techniques. A series of statistical experiments were used to minimize sandwich-panel warpage on an airplane stowage-bin shell. Warpage was broken down into three components to facilitate analysis. Twist was shown to be influenced by prepreg orientation. Spring-in was affected by the presence of a decorative poly(vinyl fluoride) film; this effect was counteracted primarily by the addition of a ply of style-120 prepreg on the opposite side of the panel. The additional ply of 120 prepreg also helped to minimize bow.

Non-Isothermal, Non-Newtonian Analysis of Three Dimensional RTM/VARTM Processes Using HP-Adaptive Finite Element Method
Ravi Mayavaram, Mahender Reddy, May 2000

A numerical analysis of the RTM/VARTM processes using an hp-adaptive finite element method is presented in this paper. The constitutive behavior of the resin is modeled using the Carreau-Yasuda 5-parameter model with the WLF and the Arrhenius functions for describing the temperature dependence of the viscosity. In addition, the viscosity can also be read in as a tabular function of the effective shear rate and the temperature. The RTM process is modeled as a three-dimensional, two-phase flow of resin and air (weakly compressible fluid) using a modified Darcy's model. Examples demonstrating the role of SUPG smoothing, viscosity variation, vacuum conditions, and dynamic adaptivity are presented in this work.

Mechanochemical Alteration of Ethylene Copolymers via Solid-State Shear Pulverization (S3P)
Manisha Ganglani, Stephen H. Carr, John M. Torkelson, Klementina Khait, May 2000

Solid-State Shear Pulverization (S3P) is a novel process that uses mechanical energy to cause mechanochemical alteration of some of the polymer chains. The process pulverizes polymers and results in fine powders. Fragmentation events involve a limited amount of chain cleavage depending upon the levels of mechanical strain developed and the molecular weight distribution of the materials. Several virgin ethylene homo- and copolymers were used in this study. It is seen that S3P can alter the flow properties but leaves molecular weight distributions and the thermal properties of these polymers unchanged.

Investigation of the Mechanisms by Which Glass Fibers Disperse in a Polystyrene Matrix
Melody M.H. Kuroda, Chris E. Scott, May 2000

Effective dispersion of chopped glass fibers into thermoplastic matrices is critical for achieving optimum properties. In an effort to further understand the mechanisms by which dispersion occurs, model experiments are conducted using 4 mm long chopped glass fiber bundles embedded in polystyrene. The effects of the process variables of temperature and shear rate upon the onset and mechanism of dispersion are investigated with optical microscopy. Two distinct breakup mechanisms can be identified: rupture and erosion. Rupture results in clusters of fibers separating from the bundle. Erosion occurs when single fibers are removed from a bundle's edge. The onset of dispersion in both simple shear and squeezing flow experiments is a stochastic process.

Laser Surface Modification of Polymers to Enhance Adhesion Part II-PEEK, APC-2, LCP and PA
S.M. Tavakoli, S.T. Riches, May 2000

Excimer lasers have been employed to modify the surfaces of a range of polymers to enhance adhesion. Considerable increases in joint strength were achieved as a result of laser treatment. Many lap shear joints, exposed to hot/wet environments, provided high retention of joint strength and durability. Laser-treated PEEK and APC-2 joints exposed at 50°C and 96%RH for several weeks, showed excellent resistance to ageing.

Stereolithography Inserts - Pros" and "Cons" to Use Tin as a Backfilling Material"
Aureo Campos Ferreira, Carlos Henrique Ahrens, Fernando Humel Lafratta, Ricardo Borges Gomide, May 2000

Stereolithography inserts shells for injection molding tools are filled in the backside, aiming to support high pressures and to improve the cooling efficiency on the mold. A common backfilling material used is an alloy of bismuth. However, there are other alternatives, such as tin, which has a higher thermal conductivity. This article discusses the pros" and "cons" to use tin as a backfill and investigates if it provides a better cooling condition improving mold's life."

Enhancement of Natural Fiber-Epoxy Interaction Using Bi-Functional Surface Modifiers
Arun Sampath, George C. Martin, May 2000

Enhancement of fiber-matrix interaction for a jute-epoxy composite system was attempted by surface modification of the fibers. The surface modification of jute fibers was achieved using bi-functional amines, which were capable of bonding with both the fiber and the matrix. The changes in interface bonding were observed by measuring the flexure modulus of the composite samples.

Ethylene/?-Olefin Elastomer Based Compositions for Automotive Interior Applications
Kim L. Walton, Tim Clayfield, May 2000

Ethylene/alpha-olefin copolymer elastomers based on single site constrained geometry catalysts exhibit a number of physical properties that make them extremely useful for automotive interior applications. Due to the low level of unsaturation in these polymers, they exhibit outstanding heat and UV aging resistance. Their molecular structures enable these polymers to exhibit low glass transition temperatures (Tg). Thus, compositions containing these polymers exhibit very good low temperature impact properties. Furthermore, these products impart inherent flexibility and soft touch to compositions and eliminate the need for plasticizers. Ethylene/1-octene copolymers exhibit an optimum combination of ultimate tensile and low temperature properties. Ethylene/1-octene copolymers can be compounded to produce flexible TPO compositions with elevated temperature and desirable softness suitable for automotive interior applications.

Utilisation of Fly Ash as a Filler in Plastics
Maurice Biagini, Alexandre Paris, Jesse McDaniel, Vaclav Kovac, May 2000

Fly ash is a by-product of the ground coal burning process used in power generation plants. Since fly ash primarily consists of inorganic materials, it is a potential filler substitute for conventional fillers in the plastic industry. In this work, the mechanical, physical, and thermal properties of fly ash filled polypropylene were determined and the effect of adding fly ash on the properties of the resin was studied. Driven by the economical potential and environmental aspect of the usage of fly ash, this study enabled us to determine the viability of coal fly ash to be used as a substitute filler in plastic resins.

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