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

Shrinkage and Warpage Analysis of Injection-Molded Parts
T. James Wang, C.K. Yoon, May 2000

Hot polymer melt shrinks when it is injected into the cold mold cavity. In the injection molding process, pressure is high near the polymer entrance and low at the last-fill location. The polymer temperature is low near the mold wall surface and high at the core region. Because of these two types of non-uniformity, the part will shrink differently at different planar and thickness locations. This causes warpage. Different process conditions will result in different non-uniformity. In this study, the effects of packing time, packing pressure, fill time and mold wall temperature will be discussed. Computer-aided engineering (CAE) and design of experiment (DOE) will be carried out first. The process window will be investigated. Experimental results will also be reported.

Quantitative Relationships between the Parameters of Thermal Degradation of Polyvinyl Chloride and the Loss of Mechanical Properties
Susheel Ramesh Deshmukh, Francis Lai, May 2000

Thermal degradation of polyvinyl chloride (PVC) was studied to obtain quantitative relationships between temperature and duration of polymer degradation and the corresponding loss of tensile strength, flexural modulus, and impact strength. Test specimens of rigid PVC containing different concentrations of dibutyltin bis(isooctylthioglycolate) and barium-cadmium stearate were subjected to five different temperatures for five different durations. The selected test properties were determined before and after degradation. Percentage property retention was plotted against logarithm of heating time. Values of log heating time corresponding to acceptable levels of property retention obtained from these plots were then plotted against temperature to obtain Arrhenius-type relationships between the parameters of thermal degradation and the deterioration of properties.

Dielectric Relaxation Spectroscopy of Reactive Network-Forming Polymers
Maja Mihajlovic, Jovan Mijovic, May 2000

Dipole dynamics in network-forming polymers were investigated by broadband dielectric relaxation spectroscopy (DRS). The changes in reorientational dynamics during the advancement of reactions were used to (1) describe the molecular origin of various relaxation processes (?,?), (2) describe the dynamics in terms of the location and intensity of relaxation spectrum, and (3) advance an interpretation of network dynamics in terms of intermolecular cooperativity. The chemical state of network at various stages of cure was identified by simultaneous DRS and remote fiber-optic FTIR.

Injection Molding Process Simulation: A Productivity Tool for the Processor
Torsten Kruse, May 2000

To be productive as an injection molder you have to be innovative in using new technologies. To produce a high quality molded part you need a well designed part and mold, a molding cell which is able to mold the part within it’s specification, a plastic material which is produced to tight specifications and employees who are well trained. Would it be nice to train employees on how to run, optimize and troubleshoot a molding machine in a classroom environment and not on the production floor. On the production floor in order to make money the machines have to run and produce. A process simulator can fill the gap between learning theoretical knowledge and hands-on molding.

Enzymatic Template Synthesis of Processable Polyphenol
Ferdinando F. Bruno, Ramaswamy Nagarajan, Jena S. Sidhartha, Ke Yang, Jayant Kumar, Sukant Tripathy, Lynne Samuelson, May 2000

Phenolic polymers and phenol formaldehyde resins are of great interest for a number of electronic and industrial applications. Unfortunately, the toxic nature of the starting materials (formaldehyde) and extreme reaction conditions required for the synthesis of these polymers have severely limited their use in today's markets. We present here an alternative, biocatalytic approach where the enzyme horseradish peroxidase is used to polymerize phenol in the presence of an ionic template. Here the template serves as a surfactant that can both emulsify the phenol and polyphenol chains during polymerization and maintain water solubility of the final polyphenol/template complex. The reactants and conditions of this approach are mild and results in high molecular weight, electrically and optically active, water-soluble complexes of polyphenol and the template used. Polystyrene sulfonate, lignin sulfonate and dodecyl benzene sulfonate (micelles) were the templates investigated in this study. In each case, soluble polyphenol complexes were formed with molecular weights ranging in the millions. Thermal analysis and UV-Vis spectroscopy shows that these complexes have exceptional thermal stability and a high degree of backbone conjugation. Conductivities on the order of 10-5 S/cm and a?(3) of 10-12 esu are also observed. In the case of the SPS template under certain conditions, a sol gel complex may be formed. This enzymatic approach offers exciting opportunities in the synthesis and functionalization of a new class of processable polyphenolic materials.

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.

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.

Effects on Mechanical Properties of LLDPE after Modification with Organic Peroxides
Luis Mendes, Joao D'Alessandro, Ailton Gomes, Marly Lachtermacher, May 2000

The action of two differents organic peroxides at 290°C on the mechanical properties of linear low density polyethylene (LLDPE) viewing its application as internal pipeline coating was studied. When the amount of crosslinking agent increased on polyolefin it was observed that for both peroxides a decreasing of elastic modulus and stress at yield. The stress at break raised and the drop of elongation at break cocurred from 0,5% of peroxide.

Polyethylene Synthesis Using Zeolites as Support Material for Metallocene Catalysts
Simone C. Moreira, Maria de Fátima V. Marques, May 2000

In the synthesis of polyethylene, sodic mordenite and acid ZSM-5 zeolites were evaluated as support material for bis (cyclopentadienyl) zirconium dichloride catalyst system. The zeolites were calcinated at 300°C before treatment with methylaluminoxane (MAO) and Cp2ZrCl2. The supported catalyst systems were evaluated in terms of polymerization activities by varying the temperature of Cp2ZrCl2 impregnation on the support and the MAO and Cp2ZrCl2 concentrations.

Properties of an Oil Resistant TPV
S. Cook, J. Patel, A.J. Tinker, May 2000

A TPV based on a dynamically vulcanized blend of epoxidized natural rubber and polypropylene is described. Morphological and rheological properties are briefly reviewed. Basic physical properties compare well with those of other TPVs whilst oil resistance is comparable to that of a well-compounded NBR vulcanizate (34% acrylonitrile). Excellent heat resistance with good retention of properties on ageing for extended periods at 100° and 150°C is also demonstrated as is good weathering and ozone resistance.

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.

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