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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
Origin of Strain Hardening in Branched Metallocene Polyethylenes
Stéphane Costeux, Enrique Torres, Si-Wan Li, John M. Dealy, May 2016
The occurrence of strain hardening during extensional flow is known to be dependent on the molecular structure, in particular long-chain branching and molecular weight, based on studies on model polymer systems. However, commercial branched metallocene polyethylenes (BMPs) often present little or no strain hardening. The variety of molecular structures and distribution of molecular weight make it difficult to identify which species are needed for strain hardening to be observed in extension. We investigate a series of BMPs made by solution polymerization, in which the branching level vary in a systematic way, and in which only the most highly branched members of the series exhibit mild strain hardening. By use of polymerization and rheological models along with new data on the extensional flow behavior of the most highly-branched members of the set, we conclude that in spite of their very low concentration, tree-like molecules with branch-on-branch structures that provide a large number of deeply buried inner segments are essential for strain hardening in these polymers.
Using Co-Rotating Twin Screw Extruder for Fibre Reinforced Inorganics Extrusion
Karnik Tarverdi, Socrates Ioannou, Jack Silver, May 2016
The extrusion of fibre reinforced inorganic cementitious materials combinations containing different fly ash contents and using a hybrid Polyether ether ketone (PEEK) and steel screws has been studied in this paper. Water flow rate was calibrated to achieve ideal viscosity for extrusion. Specific energy inputs, specific throughput rates, pressures within the die and torque measurements have been obtained during processing at constant screw speed set at 100 rpm. Apparent viscosity profiles of extrudates were measured immediately after extrusion and average wear loss was measured on both screws after the process. It has been shown that the incorporation of higher fly ash contents led to extrudates of lower apparent viscosities, which in turn yielded lower specific energy requirements, higher throughput rates and lower pressures within the die. Average diameter reductions of both PEEK and steel screws after extrusion were comparable, indicating good potential for using screws made out of PEEK when processing materials at low temperatures thus gaining notable energy savings.
Effects of Reactive Polymer as Modifier on Impact Strength and Hydrolytic Stability of PC/ABS Blend
Kohhei Nishino, Yuichi Shindo, Tetsuo Takayama, Hiroshi Ito, May 2016
PC/ABS blends have been widely used for specific applications such as in automotive interior & exterior parts and office automation equipment parts. In this study, effects of a reactive polymer as a modifier on the properties of PC/ABS blends were investigated. The reaction between PC and maleic anhydride group cannot be expected usually because the end hydroxyl group of PC is capped with end-capping agents such as t-butyl phenol to improve the properties of PC. However, we have found that a reactive polymer which has maleic anhydride group reacted with the end hydroxyl group of PC which was hydrolyzed with metal salts. From the results, the impact strength of PC/ABS was improved with the reactive polymer.
Ultrasonic Extrusion Technology for Recycling of Crosslinked Polyolefins
Avraam I. Isayev, Keyuan Huang, May 2016
Among the many environmental problems which mankind faces in the XXI century is the problem of environmental sustainability and management of the tremendous amount of generated polymer waste. Among various polymer wastes, management of crosslinked plastics is a major environmental problem requiring a solution. This study was specifically directed toward the creation of a new, environmentally friendly and science-based technology for the recycling of crosslinked plastics. Uncrosslinked thermoplastics can be easily reprocessed and reused. However, managing crosslinked plastics is a very challenging problem. This is due to the presence of a three-dimensional network, which prevents flow and shaping of crosslinked plastics upon heating and shearing. Our laboratory developed ultrasonic decrosslinking technology for recycling of the crosslinked high density polyethylene (XHDPE) of different levels of crosslink densities and crosslinked LDPE (XLDPE). This is done by using ultrasonically aided single-screw extruder (SSE) operating at a frequency of 20 kHz and twinscrew extruder (TSE) operating at a frequency of 40 kHz at different levels of ultrasonic energy [1]. The experimental studies on the ultrasonic decrosslinking of XHDPE and XLDPE have shown that the ultrasonic extrusion was capable to preferentially break crosslinks rather than main chains in XHDPE. Significant reduction of the extruder torque, die and barrel pressures with the ultrasonic amplitude was observed during decrosslinking of XHDPE and XLDPE. The specific ultrasonic energy decreased with the flow rate and increased with the ultrasonic amplitude, while die pressure increased with the flow rate and decreased with the ultrasonic amplitude [2-5]. Accordingly, application of ultrasonic treatment during extrusion enabled an increase of productivity.
Precision Micro Feature Moulding Using Vacuum Assisted Moulding Technique For Polymeric Microfluidic Chip Applications
G. Chen, Albert Yek, Timothy Bay, Zhenfeng Wang, May 2016
In the precision moulding of polymeric microfluidic chips with designs of complicated channel structure, precision moulding of micro features with sizes down to microns and sub-micrometers are often required. In order to successfully fill these micro features on mould cavity during injection moulding, the management of cavity entrapped air is critical for minimizing the variation in melt pressure distribution during the injection phase and also avoids polymer degradation at the last filling zone. In this paper, an investigation study was conducted to evaluate the effects of vacuum assist moulding on chip flatness and the micro-feature replication accuracy of the polymeric microfluidic chips as compared to conventional injection moulding process. Process optimization with the Design of Experiment (DOE) method is used to optimize the processing conditions which defined a processing window for the vacuum assisted micro-injection moulding process. The replication accuracy of vacuum assisted moulded polymeric chips achieved less than 1% error compared to the actual insert dimension. The overall warpage was controlled within 15um, which is better than that achieved by conventional micro-moulding process.
Contribution to Warpage Analysis Using BlowView Software
Z. Benrabah, H. Mir, J. Lempicki, A. Bardetti, S. Ahmad, S. Siddiqui, M. Usman, May 2016
Geometric tolerances are critical in the extrusion blow molding of plastic fuel tanks (PFTs) for automotive applications and therefore, part deformations due to solidification need to be controlled and optimized according to specific design criteria. Indeed, the shrinkage and warpage have been a focus for PFT manufacturers since dimensional changes can contribute to variation in the assembly of the fuel tank components as well as inconsistency with fuel indication during service. The complex design shapes of tank shells exacerbate these challenges that need to be resolved upfront in the early stages of product and tool design. Therefore, the development of an accurate simulation tool, well suited for industrial applications, able to predict thermoplastic part deformations due to solidification, has become essential for part designers to help achieve an efficient production.
The aim of this work is to show the latest advancements in predicting solidification and warpage of PFTs using NRC’s BlowView1 software. First, the importance of using the ideal geometry and an uniform mesh representing the mold cavity to perform the warpage analysis, rather than the distorted inflated parison mesh, is highlighted. Then, the capability of taking into account the in-plane part shrinkage of the cookie cavity geometry instead of the mold cavity geometry has been investigated and analyzed in depth. Finally, numerical warpage simulation results obtained using BlowView are presented based on an industrial case study. The simulation results, in terms of displacements, are also compared to the actual scanned part using the best fit technique in order to exemplify the accuracy and reliability of the proposed approach.
Automated Generation of Venting System in Plastic Injection Mold
Binkui Hou, Zhigao Huang, Huamin Zhou, Yi Zhang, May 2016
Venting system plays an important role in injection mold, but the venting design process is very tedious especially for mold with complex parting surface. In this research, a systematic approach is adopted to finish the automated generation of venting system. Based on the geometric information of parting line, the main vent centerline is generated by a sequence of steps, including parting line offset and curve optimization. A recognition algorithm is proposed to find out the inlet vent and outlet vent centerline. A hybrid approach of extruding and thickening rather than sweeping is given to generate the vent feature. Finally, the prototype system has been developed and embedded into NX10.0.
Analysis on Mechanical Properties of Poly-lactic Acid Composites with Organic-Montmorillonite by Injection Molding
Chao-Chang A. Chen, His-Chun Lee, Qi-Hong Liao, May 2016
Biodegradable material enacts as an important role on reducing impacts in environment problem. This paper investigated the mechanical properties of Poly-lactic Acid (PLA) and PLA/nanocomposites by variant parameters of injection molding process. Effects on tensile strength between molecular orientation and density have been tested and discussed. The micron clay composites, organic-montmorillonite (OMMT) is used for filler materials in this study, and coupling agent, such as silane has been adopted to enhance polymer branches to catch OMMT and then improved both materials bonding. Effects on mechanical properties by different mixing ratio of pure PLA, PLA/M (PLA with OMMT) and PLA/S/M (PLA with silane and OMMT) clay composites have been prepared and the most significant factor for mechanical properties in tensile and impact strength with injection molding parameters have been obtained. The thermogravimetric analyzer (TGA) and differential scanning calorimetry (DSC) have also been used to measure the thermal properties of such PLA and PLA clay composites. Results show that the tensile properties of PLA/S/M are superior to that of PLA/M and the PLA/S/M4 of 4wt% OMMT has the largest tensile strength as 84.85MPa as increases approximately 8.0% higher than that of pure PLA specimen. However, the impact strength of PLA/M is superior to that of PLA/S/M. The PLA/M4 has the best impact strength as 0.625J/cm2 as increasing 54.3% higher than that of pure PLA specimen. Results of this study can be applied to future applications of in-vivo medical assistive device or fixed scaffold products by injection molding processes.
Scale up of Abrasive Wear in Technical Compounding
Gonzalo Marulanda Paz, Brian Fritz, Alan Malott, May 2016
A test was conducted to determine if a modified linear equation introduced in previous work has the capacity to accurately predict extruder screw wear during scale up. The equation significantly reduced the margin of error when compared to linear equations currently utilized in industry. The proposed equation was successfully utilized to extrapolate wear characteristics of a 30 mm tri-kneader from data collected in a 60 mm tri-kneader. The error obtained was found to be less than 45% for this set of tests.
An accelerated wear test proposed on preliminary work was utilized to conduct the experiment in an acceptable timetable. An item of concern was the repeatability of the test in smaller size extruders. The test proved reliable and repeatable. Further development is still necessary to relate the data from the accelerated wear test to that from industrial extruders.
Control of Rheological Resposes under Elongational Flow for Polyolefin Melts
Masayuki Yamaguchi, Jiraporn Seemork, May 2016
Rheological responses under elongational flow play a crucial role in processability of a molten polymer at various processing operations. Therefore, the elongational viscosity has been evaluated. In industry, instead of elongational viscosity, the drawdown force, defined as the force required to stretch a molten polymer, is often evaluated, which is sometimes called melt tension or melt strength. In general, the drawdown force measurement is performed at non-isothermal condition, as similar to actual processing operations. Therefore, crystallization and/or glassification processes affect the value. Here, we proposed several methods to enhance the drawdown force for polyolefins with linear structure, such as isotactic polypropylene (PP) and high-density polyethylene (HDPE), considering the crystallization behavior. The results indicated that the drawdown force increases with the die length in the wide range of draw ratios and shear rates at die. Furthermore, this phenomenon was pronounced for a melt having long relaxation time at low extrusion temperature. The mechanism of the drawdown force enhancement was found to be attributed to rapid crystallization owing to the reduction in the density of entanglement couplings after passing through a long die. In fact, marked molecular orientation was confirmed by 2D-XRD measurements. Furthermore, the drawdown force of PP was enhanced by the addition of a nucleating agent. Blending with other polymeric materials such as high-density polyethylene (HDPE) and poly(methyl methacrylate) (PMMA) having low viscosity is also effective to enhance the drawdown force.
Process-Integrated Printing Technology for Plastic Parts during Injection Molding
Agnieszka Kalinowska, Michael Gehde, Martin Dehnert, Robert Magerle, May 2016
In-Mold technologies, such as In-Mold Labeling or In-Mold Decoration, have been used for several years for the process integrated decoration of plastic surfaces. The additional handling and transport processes cause consi-derable costs and are a big disadvantage. The new in-mold printing, a process integrated printing technology offers an alternative and enables the decoration of plastic parts during injection molding. Here, the image is pad printed onto the surface of the mold and then transferred to the surface of the plastic part during injection molding. The feasibility of this method is demonstrated on PP and a process related phenomena of the ink transfer and the ink adhesion are identified. The mold temperature is conside-red to be particularly critical. This is due to the fact that the temperature of the ink is affected by the mold tempe-rature and liquid ink is necessary for a transfer of the ink to the polymer surface. In this study the thermal situation at the ink-plastic interface as well as the microscopic structure of the ink-plastic-interface are investigated. The goal of this paper is to show the influence of process para-meters and conditions and their influence on the ink adhe-sion of printed motives.
Environmental Stress Cracking Study of Alternative Welding Processes in Apparatus, Tank and Pipeline Construction
Ronald Dietz, Mirko Albrecht, Eric Brückner, Michael Gehde, May 2016
The infrared (IR) and vibration (VIB) welding processes are joining technologies established in series fabrication. They are characterized by their economically viable and efficient process management. These joining technologies are suitable for utilization in apparatus, tank and pipeline construction. However, they cannot be applied to this field. One reason for this is the lack of knowledge and proof in relation to the Environmental Stress Cracking (ESC). Within the framework of a research project promoted by AiF (Allianz industrieller Forschung), the vibration and infrared welding processes were investigated. Their potential for long-term applications was studied. The results show that minimum tensile creep welding factors of 0.8 are achieved by using the infrared (short-wave radiation emitter) and vibration welding processes. It was possible to obtain values which correspond to those of heated tool butt welding. Furthermore, the knowledge base of the mechanism of failure behavior of welded joints between plastics undergoing ESC was extended.
Effects of Clay Loading and Gascounter-Pressure on the Tensile/Foaming/Surface Roughness Properties of Microcellular Injection Molded PP/Claynano Composites
Shyh-shin Hwang, Jui-Pin Yang, Ching-hsin Hu, Peiming Hsu, May 2016
This study investigated the effects of the clay loading and gas counter-pressure technique (GCP) on the tensile/foaming/surface roughness properties of microcellular injection molded Polypropylene (PP)/clay nanocomposites. In the gas counter-pressure technique, nitrogen fills up the cavity during the injection molding process. This can delay the foaming process and affect the microcellular injection molding process. The results showed that the tensile strength decreases with the counter pressure and increases as holding time is increased, while the flow length decreases as the holding time increases. The cell size decreases as the holding time increases.
Advances in Adhesive Technology for Bonding Liquid Silicone Rubbers to Plastics and Metals
Paul A. Wheeler, Tarek A. Agag, Brian P. Carney, Rebecca S. Cowles, Douglas H. Mowrey, May 2016
LORD Corporation offers new adhesive solutions that effectively bond platinum-cured liquid silicone rubber (LSR) to various substrates directly in an injection or compression molding process. This technology does not require plasma treatment or other complicated and costly surface preparation steps. In this study, three new adhesive systems were tested to bond LSR to various substrates, including polycarbonate, thermoplastic elastomer, polyamide, and stainless steel. Parts were molded and peel tested. This process and product technology offers a number of benefits compared to existing technology, including enhanced design freedom, more robust processing, less surface preparation requirements, and environmental friendliness.
Impact of Processing Method and Loading of Active scavenger (Linoleic Acid) on Properties of Polyethylene Terephthalate
Michael Angelo Miranda, Maria Coleman, Saleh Jabarin, May 2016
The food and packaging industries are interested in approaches to reduce the permeability of oxygen in polyethylene terephthalate (PET) to extend the shelf-life of product. Shelf life of a product can be increased using various approaches, including reduction of oxygen permeation through packaging wall. The food and packaging industries are interested in approaches to reduce the permeability of oxygen in polyethylene terephthalate (PET). This has led to considerable research in barrier improvement including the use of active scavenger that permanently bind oxygen. This paper focus on comparison of two methods in incorporates a renewably sourced active scavenger within PET. Specifically, single screw and twin screw extruders were used to blend linoleic acid with PET to form films and pellets at loading up to 2 %. End group of PET/linoleic acid system produced using single screws extrude shows an increase in carboxylic acid end groups which is consist blends of linoleic acid. The twin screw product shows a reduction in hydroxyl end group which indicates that reactive extrusion has taken place. The presence of linoleic acid within PET was confirmed by NMR. Linoleic acid has a plasticizing effect which results in lowering of glass transition temperatures and crystallization temperature which is more pronounced when single screw extruder was to produce films. This work is geared towards the measuring oxygen permeability of the films produced by both methods.
Development of a Predictive Power Law Relationship for Concentrated Slurries, Part 1: Theory
Gregory A. Campbell, Michael E. Zak, Jayaprakash. S. Radhakrishnan, Mark D. Wetzel, May 2016
All polymer slurries that have a high concentration of filler are shear thinning. This can include the starting materials for sheet molding compound, polymer based inks, many reactive extrusions systems, and polymer concentrates that are let down in extrusion systems as color concentrates or opacifiers. Several sizes of calcium carbonate were initially investigated because of their extensive use in the polymer industry as fillers. The investigation focused on developing an analytical tool that would lead to understanding and the prediction of the flow characteristics of slurries that have a Newtonian continuous phase but have high enough filler concentration to exhibit shear thinning or power law characteristics. This work’s focuses on concentrations where the initial yield behavior is not dominant A new function was found that linearly correlates the power law constant, n, to the concentration of the filler. The behavior of this function suggests that the Newtonian to Power-law behavior may be dominated by percolation processes. We present here a theory that predicts the characteristic of the power law constant, n, as a function of filler concentration and is based on observing and modeling the well-known plug formation in the center of a tube as the material flows down the tube. The plug was experimentally shown to be a non-dissipating volume in the flowing slurry. This percolation based rheological analysis was then extended to a highly filled Polyethylene resin.
The Incumbent Resin Effect for the Single-Screw Extrusion of Polyethylene Resins
Mark A. Spalding, Qian Gou, Xiaofei Sun, Qing Shi, May 2016
Innovative polyethylene (PE) films are constantly being developed by switching the existing or incumbent resin with a new or challenger resin. If the extrusion equipment is designed properly, the film with the challenger resin will be acceptable for further testing and marketing. However, if the extrusion equipment is not designed properly, old degraded material from the incumbent resin will be pushed out of the extruder by the challenger resin, contaminating the test film. In many cases, the challenger resin incorrectly receives the blame for the gels. This paper describes the incumbent effect, presents a case study, and provides technical solutions.
Bioepoxy Foaming Using Polymethylhydrosiloxane
Nathaniel Brown, May 2016
The Corporate Average Fuel Economy (CAFE) standards mandate that cars and light trucks have a fuel economy of at least 54.5 MPG by 2025 in an effort to eliminate 6 billion tons of cumulative CO2 emissions. This directive has spurred the automotive industry to focus on a variety of options. Among these are lightweight structural polymeric foams, which offer tailor-made solutions for significant weight reduction while not compromising on safety. However, most structural foams are petroleumbased, thereby contributing to the depletion of nonrenewable petroleum resources. Biopolymers, such as those from non-food based sources, offer a more environmentally-responsible alternative.
In this study, the effect of polymethylhydrosiloxane (PMHS) as a foaming agent on the properties of pine oilbased epoxy was investigated. The resulting materials were then tested for their compression properties, density, and microstructure. Lightweighting of up to 77 % was obtained and the delayed addition of foaming agent was shown to be more effective at improving specific mechanical properties, relative to immediate addition of foaming agent.
Thermal and Mechanical Properties of Epoxidized Pine Oil and Acrylated Epoxidized Soybean Oil Blends
Mario Krussig, May 2016
Synthetic polymers derived from crude oil are widely used across various industries. However, increased environmental regulations tackling climate change have spurred interest in development of bio-sourced polymers. While promoting the cause of sustainability, biopolymers also possess inferior mechanical properties, limiting their widespread use. A plausible and cost-effective way of enhancing the properties of pure biopolymers is to blend them with other polymers and/or reinforce them with stiff fibers. This study investigates the thermophysical properties of bio-based thermoset blends of epoxidized pine oil (EPO) and acrylated epoxidized soybean oil (AESO). The blends were prepared via casting in five different ratios by volume (EPO/AESO): 100/0, 90/10, 80/20, 70/30, and 0/100. Mechanical properties of blends were studied via tensile testing and scanning electron microscopy, while chemical properties were analyzed using thermo-gravimetric analysis.
Production of Controlled Rheology Polypropylenes from Metallocene and Ziegler-Natta Resins
Shouliang Nie, Costas Tzoganakis, May 2016
Peroxide induced controlled degradation of polypropylene has been well studied for commodity Ziegler-Natta based polypropylene (ZN-PP) resins and it is practiced industrially for producing resins of controlled rheological properties with accompanying narrower molecular weight distribution (MWD). In the present work, this technique was also tested on metallocene-based polypropylenes (mPP), possessing an initial narrow MWD. Kinetic model simulation results indicate that the polydispersity index (PDI) of the mPP remains almost unchanged while reducing molecular weight (MW) with increased peroxide concentration. Based on this observation, experiments were carried out to demonstrate the possibility of producing controlled rheology polypropylenes (CRPP) having targeted weight-average MW but varying PDI from different commodity resins of mPP or ZN-PP type.

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