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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Experiments with Hot Tool Joining of HDPE to Mild Steel
Joining of dissimilar materials like metals to plastics and polymeric composites is needed to make structures lighter for automotive and aerospace applications. In this work, HDPE was joined to mild steel sheets in a lap shear configuration using a heated tool. The steel sheets were sanded with and orbital sander and chemically surface treated prior to joining. The metal substrate was heated for a preset time by pressing it against a hot tool while the HDPE sheet was heated using non-contact heating with a gap of 1 mm from the hot tool. Then the steel sheet, HDPE and the hot tool were retracted, and the heated HDPE sheet was pressed against the hot metal surface for a preset time resulting in flow of thermoplastic into roughened area and joining the parts. The heating time was varied from 10s to 30s with 20s of heating producing the strongest joints. Three surface preparations of the steel sheets were investigated. The sanded steel sheet with a coarser finish prepared with pickling solution had the highest joint strength among all the tests.
Plastics and Composites Joining Laboratory Department of Materials Science and Engineering The Ohio State University
This work presents an analytical heat input model or Friction Riveting joints. Case-study friction-riveted joints were produced with unreinforced polyetherimide (PEI) and aluminum alloy AA2024 to validate the analytical model. Due to physical and phenomenological process similarities, principles from the heat generation in spin welding and metal friction welding were applied to describe heat generation in Friction Riveting. The proposed general formulation for total heat input considered both frictional and normal force contributions. However, experimental validation results indicated that the normal force contributions for the total heat input were very small (0.08% - 0.13%). Therefore they may be neglected for simplification. Furthermore model validation results showed that the viscous dissipation component of the frictional contribution varies from 91.5% to 94.7%. This shows the importance of internal shearing in the molten polymer as a mechanism of heat generation.
Generating Ultrasonically Welded Parts with Improved Strength and Reliability for Critical Applications in Medical Device Manufacturing by Utilizing Advanced Melt Flow Controls of Servo Driven Ultraso
Ultrasonic welding of thermoplastics is widely used by many industries to fuse together two parts in a short time without additional consumables. The development of servo-driven ultrasonic welders introduces unique levels of control. This study pursues previous research and investigates the capabilities of servo-driven welders to produce stronger welds. It focuses on developing a more robust and better controlled joining process for medical devices that increases the strength and reliability of welds without fully collapsing the joint or creating excessive weld flash. Experiments were completed in which the weld velocity was varied, and the resulting strength and appearance of the welds were evaluated against the intense requirements of the medical industry. Analysis of weld cross sections suggests that higher weld strength was associated with a linearly increasing weld velocity profile.
Thermography and Weld Strength Characterization of Thermoplastic 3D Printing
In fused filament fabrication (FFF), a material extrusion additive manufacturing (AM) method, thermoplastic filament is extruded though a rastering nozzle on prior layers building a 3-dimensional object. The resulting strength of the FFF produced part is limited by the strength of the weld between each layer. While numerous factors can affect the weld strength, the temperatures of the extrudate and the previous layer dictate the amount of interdiffusion and thus the weld strength. To investigate the relationship between the FFF processing conditions, extruder temperature and feed rate, and final build strength, infrared cooling profiles and weld fracture strengths are compared.
Feed Mechanism for Improvement in Scale up from Small Laboratory Reciprocating Kneaders
Industrial laboratory extruders need to have a minimum size to guarantee accurate scale up. For reciprocating kneaders the bore of the machine is required to be between 45 mm and 60 mm. The fundamental restriction preventing accurate scale up is the feeding capability of smaller machines where area available for feeding and de-aeration is limited.
An alternative feed section was tested. The new feeding zone allowed for accurate scale up from a 30 mm TriVolution compounder. The solution provided can be easily retrofitted into any kind of reciprocating kneader. Furthermore the new feed zone reduced investment when compared to a standard kneader zone.
Stability of Poly (Etheretherketone) and Poly [2, 2’ (M-Phenylene- Bibenzimidazole] Blend under Harsh Environments
The objective of this work is to investigate the degradation mechanisms and property changes of a blend of poly (etheretherketone) (PEEK) with poly [2, 2’-(m-phenylene-5, 5’-bibenzimidazole] (PBI) upon exposure to water at temperatures up to 288 °C. The molecular scale damping behavior of PEEK/PBI blend was probed using dynamic mechanical analysis (DMA). Atomic Force Microscopy based nanomechanical mapping has been used to assess the moduli profile near the interface of PEEK and PBI with various environmental exposure histories. The results demonstrate that the incorporation of water influences the compatibility behavior of PEEK and PBI through enhanced interfacial adhesion. Fracture toughness of the PEEK/PBI blend is significantly reduced by hot water exposure at 288 ºC.
Properties and Modeling of Partially Compacted, Commingled Polypropylene Glass Fiber Fleece Composites
The aim of this work was to investigate the influence of the formulation and the porosity on the properties of partially compacted composites made of commingled polypropylene and glass fibers. Furthermore, we wanted to develop a model to predict the properties of such composites to aid materials development.
We found, that porosity is indeed a decisive factor influencing this type of composites. The most important parameter affecting the porosity was the number of layers used in the compaction process, reaching an optimum porosity of about 20-30% by stacking 3 to 4 layers of the fleeces. Furthermore, the use of MAH-PP as additive incorporated in the PP fibers improved the mechanical properties of the composites. The modeling of the elastic modulus was found satisfactory; however the influence of glass fiber orientation and length should be evaluated more in detail.
Measurement of Thermoplastic Polyurethane (TPU) Viscosity with Slit Die Rheometer
For plastics product manufacturers it is imperative to know the viscosity profile of polymers melt and to have an insight of their flow behavior so a consistent quality in products can be ensured. In this study, a custom-designed slit die rheometer was attached to a single screw extruder and the viscosity of three thermoplastic polyurethane (TPU) grades is measured for a range of shear rates at several different temperatures. During the viscosity measurement, the pressure was monitored at three different locations along the slit die channel; while the melt temperature was monitored at entrance of the channel. The measured viscosity profiles of the three TPU grades are reported.
The Effects of Nano-Clay on the Rheological Properties of Polylactic Acid
The rheological properties of polylactic acid (PLA) and its nano-composites with 3% and 6% montmorillonite (clay) are investigated using parallel plate rheometry. Frequency sweep experiments are performed at temperatures ranging from 160 to 185 ?. For all of the samples, as expected, both the storage modulus G' and the loss modulus G' decrease with increasing temperature. Master curves of G' and G' are successfully constructed for the neat PLA and its nano-composites, indicating the validity of the time-temperature superposition for these systems. Adding the clay filler increases the G' especially in the long term region as well as the dynamic viscosity, exhibiting reinforcement effects. This is consistent with the discrete relaxation spectra determined based on the dynamic shear data. Long chain modes are present in the composites, presumably coming from the interaction between the clay and the surrounding polymer chains.
Tensile Yield Stress Modeling of PTFE Paste Extrudates: Effect of Processing Conditions
The yield strength of extrudates of a Polytetrafluoroethylene (PTFE), extruded at different temperatures through dies of different reduction ratios, RR?(Db/Dd)2, was studied. The tensile experiments have been performed using the Sentmanat Extensional Rheometer (SER) at different temperatures and Hencky strain rates. The results showed that the yield strength increases with extrusion temperature and die reduction ratio and decreases with tensile temperature. An empirical model has been developed to predict yield stress as a function of processing conditions such as temperature and die reduction ratio, as well as tensile experiment parameters i.e. temperature and Hencky strain rate.
High Performance Inorganic Pigments: Complex Inorganic Colored Pigments
Color is as basic to people as emotions. When we are sad we feel blue, when we’re sick we look green and when we’re mad we are red under the collar. In fact, our use of color predates even modern humans.1 Scientists have discovered that humanities ancestors dispersed pigments with an abalone shell and quartz rock into natural resins to produce paints for body adornment and cave paintingsthe first DIY home improvement projects. Those earliest pigments were natural ochres. In the ongoing centuries we have expanded our palette of pigments to include synthetic pigments and organic chemistry based pigments. A special branch of this pigmentation are the Complex Inorganic Color Pigments (CICP)s.
Complex Inorganic Color Pigments provide highperformance color for the most demanding applications for plastics and polymers. CICPs can stand up to the most challenging and aggressive processing and applications. Recent advances have found that these pigments have properties that give them the ability to address regulatory requirements and give not only color, but also functional properties.
Cellulose Nanocrystals as Reinforcement in Glass Fiber/Epoxy Sheet Molding Compound Composites
Cellulose nanocrystals (CNC) are ideal candidates for reinforcement in polymers and polymer matrix composites due to their high specific modulus, and strength characteristics. In this study CNC are added as a filler in the epoxy resin and a sheet molding compound (SMC) manufacturing line is used to make glass fiber/CNC-epoxy composites. Freeze-dried CNC were first dispersed in the hardener via sonication, then the hardener-CNC suspension was mixed with the monomer to produce the resin for the SMC production. The tensile and flexural properties, the impact strength and the thermo-mechanical properties of the GF/CNCepoxy composites are determined as a function of the CNC content. The content GF content in the composites is determined using thermogravimetric analysis. In conclusion, it is found that there is an optimum CNC content for which there is enhancement of the mechanical properties of the SMC composites.
Mechanism of Cell Nucleation in High-Pressure Foam Injection Molding Followed by Precise Mold-Opening
In the present study, the mechanism of cell nucleation in high-pressure foam injection molding with high expansion was investigated. An in-situ visualization technique was used which enabled the monitoring of the entire process of cellular structure formation from the mold filling to the final nucleation stage. It was observed that the cells which were nucleated during mold filling, the so called gate-nucleated bubbles, remained in the melt/gas mixture after the mold filling stage was completed. These gate-nucleated bubbles led to the presence of large bubbles in the final molded part, which caused a reduction in the foam cell density (number of bubbles per unit volume) and a reduction in the uniformity of the cellular structure. A foam injection molding protocol based on the application of melt packing pressure was then proposed to remove the gate-nucleated bubbles. In this protocol, a high packing pressure is applied on the melt/gas mixture to re-dissolve gate-nucleated bubbles before the mold-opening stage. When the mold opens, new cells nucleate uniformly due to the rapid reduction of pressure. Also, a numerical simulation was performed, and a comparison with the experimental result was made.
Novel Polycarbonate/SEBS-g-MA Blend for FDM-Type 3D Printing
The field of Additive Manufacturing (also known as 3D printing) is growing at an accelerating rate. Currently, 3D printing platforms based on fused deposition modeling (FDM) technology are practically ubiquitous. Relying mainly on mainstream thermoplastics such as acrylonitrile butadiene styrene (ABS), polycarbonate (PC), and polylactic acid (PLA) as feedstock, the applicability of this 3D printing method is limited due to the physical properties of said polymeric materials. The work presented here is an example of the development of a new polymer blend system for FDM –type 3D printing. Here we have created a rubberized PC blend which has physical properties differing from the PC base resin An overview of materials development activities for material extrusion 3D printing based on FDM technology performed at the W.M. Keck Center for 3D Innovation is discussed where we have created several polymer composites and polymer blends with physical properties differing from the state of the art, while maintaining compatibility with commercially available capital equipment.
An Approach to Decomposition of Deformation from a Molding Simulation
In an injection molding simulation of plastic parts, shrinkage and warpage information are of importance. Usually, the total deformation with respect to the baseline design is obtained and shrinkage and warpage are not distinctly defined. In this paper, a methodology is developed to decompose the total deformation obtained from a molding simulation into its shrinkage and warpage components. Mathematical basis for the decomposition is also described. Examples are shown to depict the shrinkage and warpage quantities and verify the methodology. Section analyses are also carried out to quantify the contribution of shrinkage and warpage to the total deformation.
Impact Properties Analysis of Rotationally Molded Polyethylene and Polypropylene for a Wide Range of Temperatures
Rotational molding is an established and growing manufacturing method for large, hollow plastic components. In this work the impact properties of rotationally molded Polyethylene (PE) and Polypropylene (PP) were tested at temperature in the range of -40 ºC to 30 ºC. Dynamic mechanical thermal analysis (DMTA) was performed to analyse the measured impact properties of PP and PE plastics. For PP, a very good relationship was found between peak impact strength and the loss modulus curve obtained in DMTA analysis. A relationship between density, ? peak height and peak impact strength was found for PE which is different from previous findings in the literature. It is concluded that further work should focus on developing an understanding of the PE material’s microstructure in order to more fully understand its impact properties.
Capillary Coextrusion: A New Process for Creating Small-Scale Coextruded Films
Coextrusion is an important method for making barrier and optical products at large scale. In these multilayer polymer films, adhesion is critical for performance, yet is difficult to predict by small scale experiments. Past work has shown vast differences between bilayers produced in coextrusion (continuous process) versus lamination (batch, quiescent process). In this work, a small scale coextruder die is designed and attached to a dual-bore capillary rheometer. Model films are quickly produced for adhesion testing, with adhesion showing a strong dependence on residence time.
Mastering Plasma & Flame Surface Treating Technologies to Improve Adhesion
In-line surface treatment technologies are used in the plastics industry to clean, micro-etch and functionalize surfaces to promote adhesion, improve quality and increase productivity. For some applications surface treatment is a requirement for adhesion success, for others it eliminates the need for expensive & specialty coating formulations, and in all cases it provides a safeguard against materials which may exhibit inconsistent surface energy. Examples are found in the automotive, medical, decorating, marking, assembly, film extruding & converting, folding carton, pipe, cable and other markets where surfaces need assistance in bonding with coatings. This paper will share laboratory trial data on the impact of surface treatment on a variety of materials with results measured in dyne level, polarity and surface free energy. It also addresses adhesion basics, how to select the right technology for your application, and how to implement blown arc air plasma, blown ion air plasma, variable chemistry plasma and high velocity flame plasma treaters for optimum results.
Ionomers as Smart Vapor Barriers for Building Applications
A “smart vapor barrier” is a material whose moisture vapor permeance changes as a function of relative humidity, preferably with the permeance increasing with increasing relative humidity. Sodium ionomers are capable of behaving as smart vapor barriers at suitably high extents of neutralization. This unique property is accentuated even further when the sodium ionomers are modified with fatty acid salts. The smart vapor barrier properties of the ionomers compare favorably to commercially-available polyamide film used for this application (as measured by ASTM E96 Procedure A and B testing). Modified permeance testing at extremely high relative humidities indicates that the permeability advantage of ionomer films over the commercially-available polyamide film is extended even further, which is desired for this application.
Fabrication of Interconnected Porous Poly(Lactic Acid) Scaffolds Based on Dynamic Elongational Flow Procedure, Batch Foaming and Particulate Leaching
This study reports a highly porous interconnected poly(lactic acid) (PLA) scaffold fabrication method, which utilized self-developed vane extruder melt blending followed by supercritical carbon dioxide (Sc-CO2) foaming and particulate leaching. PLA as polymer matrix was blended with polyvinyl alcohol (PVA) and NaCl particles via vane extruder, which generates global dynamic elongational flow. Then, the prepared blends were foamed by Sc-CO2 followed by leaching the porogens. It was found that most NaCl particles could preserve their original size after vane extruder blending and the macropore density and size can be tuned by modifying the salt concentration and particle size. The scaffolds prepared using this approach could achieve a porosity up to 93% with well interconnected porous structure.
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