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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The Creep Behavior of Poly(ethylene terephthalate) Bottles
Room temperature viscoelastic behavior of PET beverage containers was studied. Internal pressures result in an increase of the container volume. By assuming a cylindrical geometry, stresses can be computed and linear strains can be estimated from the volumetric changes. A time-dependent creep compliance was determined for 2-L freestanding containers under various internal pressure loads. These values match favorably with uniaxial creep measurements. From isochronous plots, the viscoelastic behavior is shown to be linear over a limited range of pressures. The creep curves show all the characteristics of simple linear viscoelastic models such as instantaneous elastic response, retarded elastic response and permanent deformation.
Measurement of Layer Deformation in Coextrusion Using Unique Feedblock Technology
Multilayer coextrusion is a process in which two or more polymers are extruded and joined together in a feedblock or die to form a single structure with multiple layers. These layers should be uniform in thickness across the structure for best performance. However, layer thickness non-uniformities have been observed in many coextruded products. Previous work has shown these layer thickness variations can occur due to viscosity differences between the polymers in the layers and/or elastic effects that introduce secondary flows. The objective of this work was to experimentally measure the secondary flow velocities in a square channel using a unique coextrusion feedblock that produces annular rings instead of planar layers.
Enhanced Performance via Ester Lubrication of Rigid PVC Formulations Modified with Chlorinated Polyethylene
In traditional calcium stearate/paraffin wax systems, higher levels of wax leads to lower melt temperatures, higher gloss, and higher impact properties of the extruded sheet or profile. Unfortunately, higher levels of wax also leads to longer PVC fusion times, and an increased tendency to develop die plate out. However, recent work with ester lubricant systems, in PVC formulations using chlorinated polyethylene, have shown that lower extrusion temperatures, pressures and torque can be achieved without sacrificing fusion time or increasing the risk of die plate out. All while maintaining or enhancing gloss and impact properties.
A Study on the Poly(ethylene naphthalate)/Poly(ethylene terephthalate)-Poly(ethylene naphthalate) Copolymer Blends
Poly (ethylene naphthalate)/Poly (ethylene naphthalate)-poly (ethylene terephthalate) copolymer [PEN/(PEN-PET)] blends were investigated. It was found that introducing PEN-PET copolymer to PEN/PET blending system instead of using PET caused the lowering of transesterification reaction in melt mixing as compared to PEN/PET blends. As the duration of mixing gets longer, the transesterification difference between PEN/PET blends and PEN/(PEN-PET) blends becomes more evident. The increase of transesterification in PEN/(PEN-PET) blends with increasing mixing time resulted in the decrease of melting temperature, while glass transition temperature increased. In addition, our time resolved light scattering data shows that slower crystallization could be obtained in PEN/(PEN-PET) blends as compared to PEN/PET blends.
Warpage Analysis of Solid Geometry
The requirement to create a shell model on the midplane of the part for warpage analysis is at odds with the trend toward solid modeling. A method is introduced that enables warpage analysis without the midplane model. This ensures that the user interacts only with the solid geometry. In this paper we present results obtained with the new technique and compare them to those obtained on a midplane model.
Assessment of Opportunities to Produce Distributed Multilayer Film Microstructures in Thermoplastic Blends by Chaotic Mixing
Chaotic mixing of binary components has been recently used to produce and distribute fibers, multi-layer films, and fragmented sheets in melts. Formation mechanisms and means to promote one type over the other remain uncertain. In this study, in situ film formation and breakup in PS/LDPE blends was examined for differing extents of mixing. Results demonstrate new opportunities to develop distributed multi-layer films during blending processes.
A Novel Additive for PP Fiber
The purpose of this paper is to present the data on UV stabilization of flame retarded polypropylene fiber. The evaluation was conducted by exposure in the xenon arc weatherometer @ 63°C under dry conditions. Proprietary additives provided unique physical property retention for flame retarded polypropylene fiber.
Thermal Analysis during Epoxy Casting Process for Joint Units of High Voltage Cable
The temperature distribution and the degree of cure in an epoxy system during the casting process, which is used in the connecting unit of high voltage cable, have been simulated using the FE solver of MARC including the programmed routines. The curing kinetics of the epoxy system used in the casting process was determined by DSC test, which was used as material input data of the developed program. To verify the developed simulation program, we have compared the simulated results for the simple model problem with those simulated by C-MOLD. The simulation results of real epoxy system for the connecting unit of the 400 kV cable, which is currently under development, are also presented for various processing conditions.
Development of 0.5 mm Super SO DIMM Connector with Computer Simulation Tools
Super Small Outline Dual Inline Memory Module (SO-DIMM) is widely employed in the design of next generation notebook PC and portable electronic devices. The maximum warpage of the injection-molded connectors are required to be a low as 0.1mm in order to be compatible with the SMT (Surface Mount Technology) process. Design of Experiment method and computer simulation were utilized to investigate the complex interaction among final dimensions, mold design, grade of liquid crystalling polymer and injection molding conditions. By using the L9 orthogonal table, the most critical factor affecting the warpage was identified. The effects of other factors were also discussed.
A Novel Computer Simulation Technology for the Cooling Analysis of Complex Injection Molded Parts
Cooling analysis has been the biggest obstacle in the simulation of the injection molding process, mostly due to the loss of convergence and enormous computation efforts encountered in the conventional boundary element method (BEM) approach. However, cooling analysis is not only essential in designing cooling channel layout, but also in optimizing the overall accuracy of filling, packing and warpage analyses. Fast Finite Element Method (FFEM) has been proved to provide excellent computation efficiency over the conventional BEM. A case study of complex car panel with FFEM is discussed in this paper.
Cooling of Extruded Plastic Profiles
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
Thermoplastic Paint (a.k.a. Film Finish, Paint Film, Dry Paint): A Complementary Technology for Exterior Automotive Plastic
Thermoplastic film technology and a new plastic molding process, under development in a joint effort by ValTek and U Mass Lowell, combine to offer reductions in system cost, total emissions and weight for automotive Class A" exterior panels in the new millennium. The recyclable structural panels are fabricated using Class "A" film finishes in one step and targeted for vertical and horizontal automotive panels."
High Velocity 3 Point Bending Test Using an Impact Tower
The idea of using an impact tower for 3-point bending for polymer testing has been developed before . In this work the experimental method is refined. The vibrations are reduced by removing the ends of the specimen and by using a smaller span. Results are presented for a polypropylene. The modulus and the yield stress increase with strain rate, as predicted by viscoelastic consideration and by the Eyring theory for the yielding of polymers.
Coloration of Polytrimethylene Terephthalate Fibers with Pigments and Polymer Soluble Dyes
Polytrimethylene terephthalate (PTT) is a recently commercialized polymer with both demonstrated and potential for increasing use in fibers for carpets and textiles. It is both dyeable in the conventional sense but also readily colored in the melt phase with pigments and polymer soluble dyes. This paper explores the methods used to mass color (solution dye) PTT, the pigments and dyes that can be employed, and the color and fastness results obtained with eleven selected colorants.
Dynamic Light Scattering Method for Determination of Shelf Stability of Liquid Colloidal PVC Stabilizers
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.
Behaviour of Fibre-Bearing Syntactic Foams in Compression and Flexure
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
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
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
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
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."
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