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.

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.

Effects of Processing Conditions on the Failure Mode of an Aliphatic Polyketone Terpolymer

Nicole R. Karttunen, Alan J. Lesser, May 2000

The yield and failure response of an aliphatic polyketone terpolymer subjected to multi-axial stress states has been studied, with a focus on the effects of processing conditions on the failure mode. Testing has been performed on anisotropic hollow cylindrical samples of this semi-crystalline thermoplastic material. Samples were processed under 5 different extrusion conditions. It was found that the cooling rate has some effect on the failure mode, while the rate of extrusion is less significant. Possible processing effects that may account for the differences in behavior include residual stress, amorphous orientation, or crystal morphology.

Toughness Enhancement through Conversion of Cyclic Polybutylene Terephthalate to Linear PBT

Sam Miller, James Donovan, William MacKnight, Roger Kambour, May 2000

The fracture toughness of macrocyclic polybutylene terephthalate (simple ring molecules) and linear PBT is correlated with the size of the plastic zone at the crack tip, which is inversely related to the yield stress. Macrocyclic PBT (c-PBT) molecules have a lower melt viscosity than linear molecules of comparable molecular weight, making them easier to process. However, the cyclic molecules are highly crystalline, with a high yield stress, and consequently a lower toughness. A ten-minute heat treatment in the melt opens the rings, and allows molecular entanglement, causing lower crystallinity of the solid polymer, and increased toughness. Therefore, control of the molecular structure of PBT provides a polymer with low viscosity that can be toughened by an easy heat treatment.

Effects of PP-MMA Alloy and Impact Modification on Weathering Performance of Polypropylene

T.A. Glogovsky, M. Finnegan, May 2000

The weathering performance of polypropylene and a novel polypropylene/acrylic alloy with and without impact modifier was investigated. Accelerated weathering testing was completed using Xenon Arc Weather-ometer. Surface cosmetics (gloss and color change), microscopy, and FTIR were used to characterize the surface and bulk properties after exposure to accelerated weathering. Dramatic improvements in weathering performance were observed through the addition of propylene/acrylic alloys and a proprietary impact modifier to the base polypropylene homopolymer. The individual significance of the propylene/acrylic and the impact modifier on weathering performance were similar. The benefit observed with weathering when combining the propylene/acrylic alloy and proprietary impact modifier was additive with respect to weathering performance.

Prediction of the Weld Lines in Injection Molding Process Using Neural Networks

Faezeh Soltani, Souran Manoochehri, May 2000

A model is developed for the prediction of the weld lines in injection molding process. The position of the weld lines in a multigate cavity system, with holes and/or inserts in the part, are predicted using a neural network-based back propagation algorithm. The neural network was trained with data obtained from simulation and actual molding experimentation. For a number of test cases, the performance of the method is investigated on comparing predicted weld lines with those obtained using a complete mold filling simulation. It was found that the proposed method can predict the position of the weld lines with a good accuracy as compared to the filling simulation. Applying the neural networks reduced the amount of computational time and eliminated the pre/post processing time as compared to simulation methods.

The Effects of Mold Filling on Living Hinge Performance

Patrick J. Brannon, Bart LiPetri, Carol M.F. Barry, May 2000

Filling characteristics of polypropylene living hinges and their performance were compared in order to create a model that will predict the quality of living hinges. In this study, three filling characteristics correlated to hinge quality: melt front advancement, skin orientation, and hinge fill time percentage. First, the melt front advancement; should be parallel to the axis of hinge rotation and free from discontinuities. Then, the skin orientation must be perpendicular to the hinge's axis of rotation. Finally, the most critical parameter was the hinge fill time as a percentage of the fill time for the part.

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."

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."

Applications of Gas-Assisted Injection Molding and Injection/Compression Molding in Thinwall Molding

T. James Wang, Shia-Chung Chen, H.H. Chiang, May 2000

Gas-assisted injection molding (GAIM) and injection/compression molding (ICM) processes are studied and compared with the injection molding (IM) process for thinwall applications (also called thinwall molding). In this paper, analysts for these three processes arc carried out. A cellular phone part will be used as an example. Analysis results will be reported and comparisons of these three processes will be made. Injection pressure, clamp force and deformation will be used to evaluate these processes. Injection pressure and clamp force reduction in the GAIM and ICM processes and their effectiveness in packing will be emphasized.

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.