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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
Low Density Polyethylene/Thermoplastic Starch Blends: Effect of Glycerol Content and LDPE Concentration on Morphology and Tensile Properties in the Dual Phase Continuity Region
Francisco J. Rodriguez Gonzalez, Bruce A. Ramsay, Basil D. Favis, May 1999
Starch was gelatinized, plasticized and melt blended with LDPE in a one step process with three different glycerol/water ratios. In LDPE/thermoplastic starch (TPS) blends, the percentage by weight of LDPE was varied from 40 to 70 in order to study the region of dual-phase continuity. Extruded sheets were characterized for composition, tensile properties and morphology. Hydrolytic degradation was carried out in order to determine the degree of connectivity of TPS domains. TPS domains presented a fiber-like-structure when glycerol content was higher than 27.5%. Co-continuous morphologies were found close to 45 wt. % of TPS produced by fiber coalescence. Those results were confirmed by the degree of connectivity of TPS domains. Elongation at break of blends having high TPS loading, and compounded with 27.5% glycerol or more, maintain in excess of 80% of the original elongation of LDPE.
Bubble Removal in Rotational Molding
George Gogos, May 1999
Simple closed form solutions have been obtained for bubble dissolution in typical polymer melts encountered in rotational molding. The solutions are in excellent agreement with experimental data available in the literature. Using these closed form solutions it is shown that under typical rotational molding conditions the polymer melts may be almost saturated. As a result, bubble shrinkage occurs over long periods. Depending on the degree of saturation, surface tension may contribute substantially to the concentration gradient that drives bubble shrinkage. A pressure increase imposed on such an almost saturated polymer melt leads to a steep concentration gradient in the vicinity of the bubble/melt interface that can lead to extremely fast bubble shrinkage. The effect of surface tension on the rate of bubble shrinkage is negligible under such undersaturated conditions.
An Application Comparison of Orbital and Linear Vibration Welding of Thermoplastics
David A. Grewell, Avraham Benatar, May 1999
This paper compares the differences in weld quality between orbital vibration and linear vibration welding of thermoplastics. Generally, orbital welding was found to weld parts faster with no loss in tensile or impact strength. For parts with thin unsupported walls, orbital welding was found to produce more uniform welds with higher tensile strength than linear vibration welding. In cases where low vibration amplitudes are required, orbital welding was able to join parts with slightly lower vibration amplitude and slightly lower collapse than linear vibration welding without sacrificing joint quality.
Applications with Infrared Welding of Thermoplastics
David A. Grewell, May 1999
This paper reviews the development of IRAM™ welding (Infrared Assembly Method). In particular one mode of IRAM welding which is based on the concept of passing light (?=800 to 950 nm) through one component being welded and having the second component absorb the light at the interface. This absorption results in heating and melting of the interface and allows the parts to be welded. The major breakthrough in this technology is the ability to illuminate the entire welding surface simultaneously. There are many advantages to this technology compared to heating a single spot and translating the laser spot across the welding zone including: faster (3-10 seconds/weld), no problems with run-on" / "run-off" less residual stresses able to weld to large collapses no moving parts and easily automated."
High Thermal Conductivity Rapid Dies: Backfilled and Coated Dies
Richard Gnegy, Amod Ogale, May 1999
Rapid polymer tooling uses stereolithography to make injection molding dies in a matter of hours. These dies can be used to mold a small number of prototypes for evaluation. However, the poor thermal properties of these dies cause them to deform or fail during molding. Two methods were investigated to improve the thermal properties of such dies. The first technique consisted of creating thin polymer shells, which were backfilled with high thermal conductivity, low-melt alloys. The second technique involved the deposition of a thin layer of nickel onto the working surface of the die. This created a pathway for heat to escape to the sides of the die. The electroless coatings did not cover the entire surface of the die uniformly. Temperature data was obtained from the backfilled, nickel-coated, and solid polymer molds using embedded thermocouples. The temperature data indicated that the backfilled die cooled much faster than the other two types, and displayed enhanced thermal conductivity.
Effect of Temperature Dependent Thermal Properties on the Accuracy of Simulation of Injection Molding Process
L. Sridhar, K.A. Narh, May 1999
The effect of using temperature dependent thermal conductivity and specific heat data on the simulation of injection molding process is examined. Results of the simulation based on temperature dependent thermal conductivity and specific heat data are compared with those based on constant thermal conductivity and specific heat. These results are presented for a representative selection of crystalline and amorphous thermoplastics. The results show that the prediction of cooling time and the frozen layer fraction of the part thickness in injection molding is strongly influenced by the type of temperature dependent thermal data used.
An Experimental Design Approach: Effect of Slip and Antiblocking Agents on the Performance of a LLDPE Polymer
Kasinath Nayak, Norris M. Tollefson, May 1999
Most low density polyethylene (LDPE) and linear low density polyethylene (LLDPE) films (cast or blown) exhibit blocking during processing and end use applications. Antiblocking agents such as amorphous or crystalline silicas reduce blocking, film-to-film adhesion and thus render these films usable. We have undertaken a systematic approach in evaluating both synthetic amorphous and crystalline silicas as antiblocking agents in presence of a slip additive on the performance of an octene based linear low density polyethylene copolymer. A series of formulations were prepared with three different antiblocking agents along with a slip additive. The slip agent erucamide" was added to the formulations at five different concentrations resulting in a total of 35 formulations. The film properties including %haze yellowness index coefficient of friction and blocking force were measured. An experimental design approach was employed to determine the effect of slip and antiblock on the blocking force using selected formulations."
An Experimental Design Approach: Effect of Slip and Antiblocking Agents on the Performance of a LLDPE Polymer
Kasinath Nayak, Norris M. Tollefson, May 1999
Most low density polyethylene (LDPE) and linear low density polyethylene (LLDPE) films (cast or blown) exhibit blocking during processing and end use applications. Antiblocking agents such as amorphous or crystalline silicas reduce blocking, film-to-film adhesion and thus render these films usable. We have undertaken a systematic approach in evaluating both synthetic amorphous and crystalline silicas as antiblocking agents in presence of a slip additive on the performance of an octene based linear low density polyethylene copolymer. A series of formulations were prepared with three different antiblocking agents along with a slip additive. The slip agent erucamide" was added to the formulations at five different concentrations resulting in a total of 35 formulations. The film properties including %haze yellowness index coefficient of friction and blocking force were measured. An experimental design approach was employed to determine the effect of slip and antiblock on the blocking force using selected formulations."
Creation of Plastic Prototypes and Molded Plastic Parts via Selective Laser Sintering
Christian Nelson, May 1999
The SLS® Selective Laser Sintering process is a rapid prototyping (RP) process with the unique advantage of processing a broad range of materials in a single RP platform. Prototype parts for functional testing are produced with polyamide, glass-filled polyamide, or TPE. For small quantities of molded parts, the SLS process is used to produce composite, short run mold inserts for molding several hundred parts with common plastics. For large quantities of molded parts, the SLS process is used to produce metal mold inserts for molding over 100,000 plastic parts with most plastics. This paper will provide background information on the SLS process, describe how the process is used to manufacture metal mold inserts, and provide application examples showing time and cost savings for designers and manufacturers.
Prediction of Stiffness from Orientation Data of Glass Reinforced Injection Moldings
N.M. Neves, A.S. Pouzada, May 1999
The complex thermo-mechanical process developing in injection molding leads to through-thickness and point to point variation of fiber orientation. It is not economically viable to characterize experimentally the variation of fiber orientation. Thus, efforts have been put into modeling the fiber orientation in injection molding. Some commercially available programs already allow the prediction of fiber orientation distribution in moldings. If the fiber orientation field is known it is possible to calculate the major elastic properties, which can be input into finite-element structural analysis codes to predict product performance. That approach was followed in this work to compare the experimental flexure behavior of glass fiber reinforced polycarbonate injection molded discs with predictions obtained from FEM simulations. The data used in the FEM code was calculated from the fiber orientation data predicted using the software C-Mold.
Ultrasonic Monitoring of the Flow in a Co-Extrusion Blow Molding Die
K.T. Nguyen, T.-F. Chen, A. Steele, D. Ramos-França, C.-K. Jen, A. Garcia-Rejon, May 1999
In-line monitoring of the location of the interface inside a co-extrusion die on an accumulator blow moulding machine is performed using ultrasound. Ultrasonic waveguides similar to a pressure transducer are inserted into the wall of the co-extrusion die at different locations along the extrusion direction. One end of each waveguide is flushed with the inner surface of the die and the other end is air cooled to accomodate one ultrasonic transducer (UT). The thickness of each layer is determined by the detection of an interface echo which is enhanced by signal processing techniques. The waveguide has also been modified to measure the temperature and heat flux at the die wall. The results were compared with those obtained from a conventional thermocouple.
Comparison of Different Screw Design for Injection Moulding Machines
Nikolaus Kudlik, May 1999
The demands on injection molded products have constantly increased over the past few years. This relates not only to the quality of the produced parts but also to the economy of production in which plasticizing plays a vital role. Modern plasticizing by injection molding machines must thereby fulfill the individual demands in the processing of divers materials. This universality, which to this point was attained by the insertion of a single standard screw, reaches its limits with many materials. The insertion of special screws provides a remedy in this area. Based on trails with technical thermoplastic material as well as with polyolefins, the advantages and disadvantages of the various screw geometries, such as 3 zone screws, barrier screws, and low compression screws, are compared.
Extrusion Operation Window for Filled Metallocene Polyethylenes
María del Pilar Noriega, Tim A. Osswald, Omar A. Estrada, May 1999
This paper presents experimental results on processing of the novel metallocene polyethylenes. The experiments were performed in a 45 mm- conventional single screw extruder with a barrier screw. The evaluation of the mechanical properties, screw characteristic curves, energy balance, pressure consumption and melt temperature profile experiments were completed for the different blends of metallocene material (mPE), linear low density polyethylene (LLDPE) as the masterbatch (MB) carrier and titanium dioxide as the filler. The results for the metallocene resin show a wider operating window, higher energy dissipation, and higher torque consumption compared to the conventional low density polyethylene. Adding fillers to these materials increased the operating window and the mechanical properties, while the energy dissipation and torque consumption vary according to the filler content and processing conditions.
The Dielectric Properties of Nylon 66/Aramid Fibre Microcomposites in the Presence of Transcrystallinity
Hannah Nuriel, Nick Kozlovich, Yuri Feldman, Gad Marom, May 1999
Dielectric spectroscopy was applied in the present work for the first time to polymeric composite materials containing transcrystallinity, wherein the dielectric properties of pure nylon 66 and of aramid fibre-reinforced nylon 66 microcomposites were examined over wide frequency and temperature ranges. The dielectric response was found to be sensitive to the presence of transcrystallinity in the microcomposites. It was found that the activation energy of the ?, ?, and ? relaxations exhibits typical variations in the presence of reinforcement and transcrystallinity. The specific values of the dielectric loss and dielectric loss tangent at 1MHz as a function of temperature for the transcrystalline layer were retrieved from the composites data using the rule-of-mixtures. A comparison was conducted between the values of the transcrystalline layer and those of the bulk matrix to determine the effect of the transcrystalline layer on the dielectric properties.
The Role of Monomeric and Dimeric Oligomers of Methyl Ethyl Keton Peroxide in the Cure of Unsaturated Resin Formulations
Delphine Nwoko, Ted Pettijohn, May 1999
The most readily synthesized forms of methyl ethyl ketone peroxide (MEKP) are its monomeric (2,2- dihydroperoxybutane) and dimeric (2-hydroperoxy-2-[1- hydroperoxy-1-methylpropylperoxy]butane) oligomers. Methyl ethyl ketone peroxides are used to initiate cures at ambient temperatures, and are popular for processes that include resin transfer molding, filament winding and casting. Analytical methods have been used to quantify the amounts of residual hydrogen peroxide, MEKP monomer, and MEKP dimer in commercial formulations. This paper will discuss the effect of methyl ethyl ketone peroxide monomer and dimer, and hydrogen peroxide in the cure of orthophthalic, isophthalic, and vinyl ester resins. It will show how variations in these MEKP components affect the overall cure performance of resin systems.
Cast Film
Jan Ivey, May 1999
The cast film process, unlike the blown process, is one that quenches the molten extrudate on a chilled steel roller after it exits the die. This paper discusses the process and physical variables and how they affect film properties and quality. Most polyfin films are made by either the cast or blown process. The major differences are the basic resins and the method of cooling the extrudate once it leaves the forming die. The blown film process extrudes the molten poly from a annular die, chills the tube with air, usually chilled, and forms a bubble, with a pair of nip rolls holding the bubble pressure as cooling occurs. In the cast film process, the other popular method of thin film manufacture, the polymer is forced through a slot die and chilled on a chilled roller, solidifying the molten plastic and forming a sheet of film. Fig. 1 shows a diagram of this process. Fig. 2 shows some of the variables. The two different processes requires resins that have properties that support the process and give different properties to the finished film. This paper will discuss the cast film process, how the film is made, properties of the film and how varying the process effects the film properties. The extruder, a major player in cast film has been discussed and the output of the extruder is the feed for the cast film process. Most cast film lines manufactured today are coextrusion lines and as many of seven extruders may feed product to a common die by means of a coextrusion adapter. This adapter aligns the various polymers in a form required for the finished sheet and supplies a “plug” of polymer, correctly proportioned to the entrance of the die. The output of the multiple extruders, the combining adapter and the die determine the layer distribution of the coextruded film. In this discussion we will assume the extrusion line to be coextrusion, however, if the line is mono, the same principles apply except for layer distribution.
Air Layer Control during Winding and Handling Webs
B.A. Feiertag, May 1999
The handling of plastic films in continuous web form both in transport through process equipment and particularly in winding is complicated by the fact that these materials are usually characterized as being nonporous and having very low surface roughness. These properties lead to the significant entrainment of air between the web and roller surfaces, or between the layers in a winding roll, such that a very limited state of traction may exist between the surfaces leading to difficulties with the transport of the web through process equipment or in winding without dishing or telescoping and/or poor wound roll integrity. This tutorial reviews the current state of the art in understanding the factors relevant to air entrainment and techniques to deal with it in film handling and winding.
Blown Film Tutorial
Tom Butler, May 1999
Film fabrication is an important commercial process for plastics. Many of our essential products in our culture use films to package and protect items such as foods and durable goods. The blown film process represents one of the most common commercial technologies used to fabricate polymers into films. The blown film process at first inspection appears to be a relativity simple process which is comparatively easy to operate, but it is in fact a process characterized by it's versatility to produce films suitable for use in widely differing application with specific performance requirements. How are the basic components of the blown film process sized to assure proper operation? What are the critical parameters of the blown film process? How does the selection of process parameters allow similar film properties to be obtained on different blown film lines? What is the interaction of the process and polymer to produce specific performance properties? How do the components of the components of the blown film process work? How are measurements on the process made to assure consistent performance on different lines? What are some troubleshooting guidelines that have been found to be useful for operation of the blown film process? These are some of the questions that this tutorial will address.
Fundamentals of the Tenter Frame Process for Biaxially Oriented Film Manufacturing as Applied to Polypropylene Polyester and High Density Polyethylene
Eldridge M. Mount III, May 1999
Biaxially oriented films of polypropylene (PP), polyester (PET) and high density polyethylene (HDPE) can be made in several different processes. The tenter process will first be shown in overview to describe the function of each of the primary manufacturing steps (coextrusion, casting, machine direction stretching, transverse direction stretching, surface treatment and winding). Next the primary stretching steps and equipment configurations will be defined and characterized in terms of process and material variables and the film properties produced. From a processing focus, the primary process steps may be considered and evaluated as some form of rheometer, either for melt or solid, and these ideas will be introduced and evaluated as a means of understanding the process / film property interactions.
Experimental Study and Model Predictions of Rheological Behavior of Short Fiber Composites
A. Ramazani, A. Ait-Kadi, M. Grmela, May 1999
A set of experimental data is carried out on short fiber suspensions in viscoelastic fluids. Parameters such as fiber volume fraction, fiber length and pre-shearing are studied. Transient tests on pre-sheared samples showed that fiber orientation depends on both the strain and the rate-of-strain tensors. Increasing fiber concentration and aspect ratio increases rheological material functions in the low shear rate region. In the high shear rate region, the effect is less pronounced. The experimental data are compared to a rheological model based on the modified Jeffrey equation. The theoretical results are found to be in good agreement with most experimental data. Further changes to the original model were necessary to be able to predict the rate-of-strain-dependent fiber orientation and the observed behavior of the considered material functions.


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