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

Cooling of Extruded Plastic Profiles
L. Placek, J. Svabik, J. Vlcek, May 2000

For the proper design of cooling equipment and its dimensions in profile extrusion, it can be very useful to know the temperature fields inside the profile. To be able to understand the cooling process, a physical - mathematical model of heat transfer in the extruded profile must be used and the temperature field solved by an analytical or numerical method. There are only very few problems that can be solve analytically. We can say that some one-dimensional problems (not all) and very few two-dimensional problems can be solved analytically. For example, it is possible to solve a problem of cooling an extruded film or a thin plate. If the profile shape is more complicated, it is necessary to use a numerical method. One peculiar variable in all heat transfer simulations is the heat transfer coefficient. Its setting is important for the absolute results of the simulations. On the other hand, an approximate, but close, value of such a coefficient can cause some errors in the absolute temperatures but will still show the relative temperature distribution across the profile. In the majority of problems, the overall picture of the process is more important than knowing the exact temperature in a certain position. If a designer has a good picture about the cooling process, he/she can easily design the lengths of calibrators, their appropriate placing, the length of the cooling bath and so on. It is also possible to judge where the walls of the profile will probably bend. The designer can also decide what should be the cooling conditions, about the possible placement of infrared heaters, the length of the water bath and so on. In the case of a complicated profile it is almost impossible to imagine the temperature distribution inside the profile. In profile extrusion, any uneven cooling can cause bending, if not collapsing, of the profile. Therefore, knowing the relative temperature distribution may be more important than knowing exactly the temperature values. This presentat

Behaviour of Fibre-Bearing Syntactic Foams in Compression and Flexure
C.S. Karthikeyan, Kishore, May 2000

The comparative performances in three point bending and compression of syntactic foams comprising of epoxy resin and glass microballoons with the inclusion of chopped glass fibres of two different resin compatibility namely, epoxy and phenolic, are reported. The data showed that the compressive strength values differ marginally. As regards the flexural strength it increases for a change from epoxy to phenolic. When the properties of third syntactic foam with polyester compatible fibres was examined, it was found that the value was higher than the epoxy counterpart. This was attributed to the difference in the procedural route adopted for fabricating this latter foam.

Optimizing Injection Molding towards Multiple Quality and Cost Issues
Donggang Yao, Byung Kim, Jaehong Choi, Robert Brown, May 2000

Injection molding part designers are frequently faced with multiple quality and cost issues. These issues are usually in conflict with each other, and thus tradeoff needs to be made to reach a final compromised solution. Since evaluation of part quality and cost via injection molding simulation is very time-consuming, implementation of a conventional multi-criteria optimization procedure to injection molding problems is economically unfavorable. However, many injection molding problems dealing with multiple quality and cost issues can be modeled as constrained problems. By introducing a concept of Penalized Total Cost, such constrained problems are further simplified into bounded single-criterion problems. The bounded single-criterion problems are then optimized using a direct search-based optimization procedure. Strategies of modeling, transformation and optimization for these problems are discussed in this paper. A case study is provided.

Elongational Effects of Die Flows: Pressure Distribution and Shape Prediction
J. Sun, C. Waucquez, Y. Rubin, May 2000

There are many industrial applications in which shear and extensional behaviors of the material both play a role. This is true, for example, for flows in converging channels or flows in abrupt contractions typical of cable coating, fiber spinning or indeed flows in many plastics and rubber extrusion dies. Viscoelastic flow simulation has made it possible to predict these effects, at least qualitatively. Numerical simulations using a 3-mode PTT model reported here show a good quantitative agreement with experimentally measured pressure drops over a range of flow rates for both a short and a long conical capillary die. While this approach is physically meaningful, convergence at high Weissenberg number remains a challenge for the scientific community. This fact can sometimes justify the call for simpler, qualitative engineering approximations. By adding in the flow equations the dependence of the viscosity function on the third invariant of the rate of deformation tensor, it becomes possible to consider some effects of extensional viscosity in axisymmetric and 3D flows. We observe an increase in the pressure drop and the onset of recirculation patterns. We present numerical simulations of flow in a converging cone capillary and compare the results with available experimental data. We include simulation results for 3D die swell which show the influence of this extensional effect.

Toughening and Strengthening an Epoxy by a Liquid Crystalline Epoxy
Prakaipetch Punchaipetch, Witold Brostow, Nandika Anne D’Souza, May 2000

The effect of molecular reinforcement of diglycidyl ether of bisphenol F (DGEBP-F) epoxy by liquid crystalline (LC) diglycidyl ether of 4,4'-dihydroxybiphenol (DGE-DHBP) is investigated. The compositional effect of the LC moiety is related to mechanical properties. Tensile, impact and fracture toughness tests results are evaluated. Dynamic mechanical analysis is conducted to determine the effect of the DGE-DHBP on the glass transition and beta transition temperatures. Scanning electron microscopy of the fracture surface shows changes in failure mechanisms compared to the pure components. The results indicate that the mechanical properties of these blended samples are improved at 10-20% by weight of DGE-DHBP.

Surface Damage Resistance of Automotive Plastics
Rose A. Ryntz, May 2000

Damageability of automotive plastics, inflicted during events such as scratching, chipping, and compressive shearing, results in potentially high warranty costs and customer dissatisfaction. Polymer alloy composition, e.g., polymer-polymer interphase behavior and polymer-filler interactions, plays a major role in resultant damage resistance of a formed plastic part. Polymer processing, e.g., injection molding, also strongly affects the ability of a plastic surface to withstand such damage. This paper attempts to describe the role of polymer alloy composition, specifically filled- and unfilled-poly(olefin) blends, and final part processing behavior on surface damageability caused from scratching, chipping, and compressive shearing (gouging"). The role of interphase management e.g. control of miscibility between alloying agents appears to be the major factor affecting the ability of the plastic part to resist surface damage caused by external forces."

Mechanical Properties of Glass Fiber Composites with an Epoxy Resin Modified by a Liquid Crystalline Epoxy
Prakaipetch Punchaipetch, Witold Brostow, Nandika Anne D’Souza, Magdalena Jaklewwicz, Pablo Montemartini, James T. Smith, Sr., May 2000

The effect of liquid crystalline networks on epoxy - glass fiber composites is investigated. Liquid crystalline epoxy resins (LCEs) have many advantages including outstanding high temperature stability, high lateral strength with high axial compressive strength. The matrix is obtained from in-situ curing of liquid crystalline diglycidyl ether of 4,4'-dihydroxybiphenol (DGE-DHBP) with diglycidyl ether of bisphenol F (DGEBP-F. Impact, tensile, and compressive results are compared between the unmodified and modified systems. Scanning electron microscopy is used to study the fracture surface to understand the mechanism of fracture and interphase formation between the fiber and matrix.

Effects of Moisture Content, CEC, and Processing Conditions on Mechanical Properties and Long-Term Reliability of PBT Fiber-Optic Buffer Tubes
Brian G. Risch, Thierry Auvray, Danny Ammons, May 2000

Poly-butyleneterephthalate (PBT) Fiber optic buffer tubes were manufactured while varying initial material Carboxyl Endgroup Concentration (CEC), initial moisture content, as well as extrusion linespeed and cooling profile. Mechanical tests on aged and unaged tubes were correlated to the state of material degradation through capillary rheometer experiments and Melt Flow Index (MFI) measurements. Incomplete drying and use of PBT with a high initial CEC are shown to lead to more rapid reduction of molecular weight during extrusion as well as poorer long-term hydrolytic stability. By proper selection of material and processing conditions, material lifetimes can be at least doubled.

Characterization of the Near-Surface Crystalline Structure and Morphology of Injection-Molded TPO
Houxiang Tang, David C. Martin, May 2000

Near-surface structure is expected to play an important role in determining the surface mechanical and adhesive properties of injection-molded Thermoplastic Polyolefins (TPOs). In this report we discuss the near-surface structure of injection-molded TPO based on isotactic polypropylene (iPP), with the intention to elucidate the influence of the TPO substrate structure on the adhesion of painted layers. Localized flat-film X-ray diffraction has been used to characterize the crystalline structure of the iPP component, while transmission electron microscopy (TEM) has been used to reveal the high resolution morphology of iPP crystals and secondary particles. The polymorphism and texturing of the near-surface iPP crystals is discussed, based on the generally accepted structures of iPP crystalline phases. There is evidence to support the presence of ?-phase PP crystals in the near surface area. Significant anisotropy in the secondary particle morphology was revealed by TEM imaging.

Mold Filling and Curing Analysis in Scrimp
Huan Yang, L. James Lee, May 2000

In recent years, vacuum-assisted resin transfer molding (e.g. Seemann Composite Resin Infusion Molding Process - SCRIMP) has been widely used for marine, civil infrastructure, transportation and defense applications. Unsaturated polyester and vinylester resins are two major resins used in these processes. Their kinetic and rheological behaviors were investigated experimentally. A model was developed to quantify the effects of different curing agents on the gel time and reaction rate. This model, in conjunction with fluid flow and heat transfer models, was used to determine the effects of resin type and composition, curing temperature, and part geometry on mold filling and curing. SCRIMP experiments were carried out to verify the simulation results.

Improving the Performance of Rotomolding Resins
Alvin Spence, May 2000

Rotational molding is one of the fastest growing processes in the plastics industry today. However, this growth has been somewhat restricted by the number of and types of resins available to the molder. Polyethylene has traditionally been the workhorse for the industry because of its ease of processing. Unfortunately polyethylene lacks stiffness, along with other mechanical properties, compared to the resins used in competitive processes. This paper outlines methods to improve the performance of rotomolding resins using processing techniques, modifying the design of the part and by the inclusion of strengthening additives in the polymer matrix.

High-Performance Poly Metal Composites Replace Lead in Many Applications
Larry Stover, Jeff Frankish, David Douglas, Robert Durkee, May 2000

A new injection moldable thermoplastic composite has been developed to eliminate problems associated with lead. This nontoxic polymer-metal composite can be formulated to meet the density, mass, and radiation-shielding properties of lead, while offering superior strength and design flexibility. The use of this material eliminates lead-toxicity issues encountered in handling, fabrication, and disposal. Target applications include: nontoxic projectile cores and shot, radiation shielding for medical and nuclear power, counterweights, sporting goods, ballast systems, vibration dampening, sound proofing, and many other applications where a nontoxic, high-density, high-strength material is required.

Ballistic Impact Resistance of Thermoplastic Composites
John W. Song, Nainesh Amin, Stephen Petrie, May 2000

The correlation between adhesive strength, stiffness, flexural properties and ballistic impact resistance of Kevlar-KM2 composites with polysulfone (PSU) resin matrix was studied through examination of the failure of the composites on different processing conditions. Processing temperature greatly changed resin molecular conformation. Resin molecular conformation directly influenced composite flexural properties as well as ballistic impact energy absorption. Composites processed at 260°C showed significantly higher ballistic impact resistance than composites processed at 350°C. Significantly different failure mechanisms of these composites that are induced by different processing conditions are considered to be responsible for this result. The former exhibited mainly tension mode of failure whereas the later failed mainly shear cut. Fiber straining accompanied with delamination due to the tension mode of failure is the preferred failure mechanism for better ballistic impact energy absorption.

New Thermally Conductive Thermoplastics Offer Freedom of Design in Heat-Management Applications
René Pastor, May 2000

A new thermally conductive compound available in a variety of crystalline thermoplastic matrices can be used to improve material management in a variety of industrial and consumer applications, including heat sinks, thermostats, heat exchangers, and as radiant heating coils. Replacing heavy metal shrouds and non-recyclable metallized plastics, the new compounds are non-corrosive, can be processed on all conventional thermoplastic equipment, and can even be melt reprocessed for in-plant recycling. A variant on the technology also produces compounds that are simultaneously thermally and electrically conductive.

Parameters Affecting the In-Line Measurement of Gas Solubility in Thermoplastic Melts during Foam Extrusion
Q. Zhang, M. Xanthos, S.K. Dey, May 2000

The knowledge of gas solubility at processing conditions is of paramount importance for the understanding and optimization of extrusion foaming by gas injection. A recently developed in-line optical method is used to generate data of the solubility of atmospheric gases in PS and PET in single or twin screw extruders with gas injection capabilities. Overall, the in-line data compare favorably with off-line data where Henry's law constants were obtained from the slope of solubility/equilibrium gas pressure plots. Results obtained with the twin-screw extruder configured for improved mixing indicate: a) better data consistency, presumably as a result of enhanced homogenization/dissolution and longer residence time, and, b) a higher degree of sensitivity in detecting differences in the solubility of different gases.

Improved Organotin Stabilizers: Continuing Health and Environmental Research
Sandra R. Murphy, C. Bertelo, R. Ringwood, M. Cochran, May 2000

Years of experience and significant research support using organotin mercaptides as PVC stabilizers. Safe use of organotin stabilizers involves following Material Safety Data Sheet instructions and using adequate engineering controls and/or personal protective equipment. Modifications of stabilizers to develop more efficient formulations continue. Product stewardship includes continued development of data to improve our understanding of the effects of materials. An overview of stabilizer trends in the industry, existing data, and planned health/ environmental research is presented.

Preparation of Microporous Films from Immiscible Blends via Melt Processing
C. Chandavasu, M. Xanthos, K.K. Sirkar, C.G. Gogos, May 2000

Microporous films from immiscible blends were produced via melt processing and post-step treatments. Polystyrene (PS)/polypropylene (PP) and poly(ethylene terephthalate) (PET)/polypropylene (PP) blend systems with different viscosity ratios were studied. The blends were first compounded in a corotating twin-screw extruder and subsequently extruded through a sheet die to obtain the precursor films. These were uniaxially or biaxially drawn (100-400%) with respect to the original dimension to induce microporous structure and post treated at elevated temperature to maintain the porous structure which consisted of uniform microcracks in the order of a few hundred nanometers. The fabrication process here is shown to be a promising technique for producing microporous films that can be used for liquid and gas separations, as suggested from permeability measurements.

High Molecular Weight Film Resins with Increased Stiffness
Leonard Cribbs, Dale Vedder, May 2000

High Molecular Weight High Density Polyethylene resins for film markets typically fall into a relatively narrow range of densities to provide the desired product functionality. For example, resins targeted for the tee shirt bag market require tear and puncture properties that require melt indices of around 0.05 and densities around 0.950. Development of these resins and their respective bags has allowed for substitution of HMW-HDPE for paper in many markets. Additional substitution appears available, but require resins with both high strength and higher modulus. Using technology to produce bi-modal molecular weight distributions, film resins meeting these requirements have been produced. The resins and their end-use applications will be discussed.

Properties and Applications of Sandwich Panels Based on PET Foams
M. Xanthos, R. Dhavalikar, V. Tan, S.K. Dey, U. Yilmazer, May 2000

PET foams of variable densities, (1 g/cc to 0.2 g/cc), based on virgin and recycled material were produced by extrusion with physical or chemical blowing agents and evaluated as low density core in sandwich panels having M/F impregnated paper or flame retardant mineral reinforced PET as skin faces. Flexural and shear stiffness of the laminates were determined by variable span three point bending. Panels were also tested for thermal and moisture stability and compared with competitive sandwich constructions based on PVC foam, flake board, particleboard and plywood. Potential applications of the PET based laminates in building and construction are presented.

On the Experimental Investigation of High-Frequency Dielectric Sealing of PVC
Brahim Brahimi, Ulku Yilmazer, May 2000

This feasibility study deals with the investigation of welding Polyvinyl Chloride (PVC) sheets of different formulations, using high dielectric frequency technique. The experimental work consisted of PVC formulation (rigid sheet), mold design (new products), experimental design to quantify the effect of process parameters, mechanical characterization (tensile, peel testing) of the weld area, and process optimization. Rigid PVC formulation was selected based on two primary mechanical properties, tear resistance and shear modulus. The weld was well achieved within the studied range of parameters, while the processing conditions were experimentally optimized. Finally, new office items were successfully produced as a result of the design of new molds combined with new process layout (sheets).

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