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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Rheology of Polymer Nanocomposites
The rheological behavior of polymer nanocomposites is a field of vital importance to scientists and engineers in the plastic and rubber industry. The rheological behavior of nanocomposites is affected by type of fillers (nanoparticles, graphene, nanofibers and nanotubes) their concentration, filler-filler and polymer-filler interactions. After decades of extensive research, the theoretical description of the linear and nonlinear behavior of nanocomposites is still lacking. This presentation will discuss the rheological behavior of the polymer nanocomposites in small and large amplitude oscillatory flow (SAOS and LAOS), start-up shear flow and step-strain relaxation. Our current understanding of theoretical description of various rheological properties obtained in these flow regimes will be presented. The model parameters will be obtained from SAOS experiments. Then these parameters will be used to describe the nonlinear behavior in various flow regimes.
Investigation On The Viscosity Characterization Of The Glass Mat Thermoplastics (Gmt) In Compression Molding System
Due to its great features of lower tooling cost, better retaining fiber length and concentration, glass fiber mat thermoplastics (GMT) material has been attracting a lot of attention in modern lightweight technology development. However, some defects and unstable quality control problems are still bothering us. To overcome these troubles, people are usually applying CAE technology to assist. However, in this field, CAE is not mature enough yet due to the rheological properties of the GMT material are not measured properly. In this study, we have proposed a method to measure the rheological properties of GMT material through a compression system. Specifically, we have focused on the viscosity of the squeeze flow under the operation of compression processing. The analyzed data is further used for estimation of the rheological parameters and calculation of viscosity at various temperature settings. Moreover, the estimated rheological parameter of the GMT material is integrated into Moldex3D to evaluate the squeeze flow behavior under the compression operation through numerical simulation and experimental study. Results showed that under the higher compression speed, the loading force is increased exponentially as melt flow time is increasing. The numerical simulation prediction is consistent with that of experimental result. However, at slower compression speed, the deviation becomes more serious for simulation approach and experiment. The reason needs to be investigated later. Also, there are various conditions need to consider in the coming future.
Effect Of Molecular Weight On Dynamics Of Linear Isotactic Polypropylene Melt At Very High Shear Rates
In this work, three isotactic linear polypropylenes, with weight average molecular weights between 56 250 - 75 850 g/mol, have been characterized at 230oC over a very wide shear rate range. A low shear rate primary Newtonian plateau, a pseudoplastic region and a well developed secondary Newtonian plateau were identified for all the polypropylene melts. Flow activation energy at low (E0) and high (Einfin) shear rates was found to be 56.590 kJ/mol and 25.204 kJ/mol, respectively. For the first time, it has been discovered that the secondary Newtonian viscosity, EtaInfin, depends linearly on the weight average molecular weight, Mw, in log-log scale as EtaInfin=1.19*10^(-6)*Mw^(1.084). The observed slope close to 1 between Einfin and Mw suggests that polymer chains in the melt are disentangled at the secondary Newtonian plateau region. This conclusion is supported by the experimental observation that the high shear rate flow activation energy Einfin for given PP melts is comparable with the flow activation energy of PP like oligomer (squalane, C30H62; 2,6,10,15,19,23-hexamethyltetracosane).
Visualization Of The Flow Paths In A Tangential Internal Mixer To Optimize The Mixing Behavior
The visualization of the flow paths in a tangential internal mixer gives the opportunity to understand which kind of mixing is pronounced in dependency of process parameters. With this knowledge the mixing processes can be optimized, so that shorter mixing times and more homogenous mixing is possible. The flowing behavior between the rotor and the mixing chamber was already investigated extensively but the complex flow paths between the rotors is not well known yet. With different colored compounds, it is possible to visualize the flow paths in the mixing chamber. Hereby, the mixing process is stopped after different mixing times and the mixing chamber is completely opened to take the compounds out of it. Those compounds are sliced and photographed. The complex flow paths can be analyzed with different methods that are evaluated in this contribution. One possibility is the analysis of objects in the area between the rotors to draw conclusion on the distributive and dispersive mixing.
Rheological Method Development: Polymer Designs For Blow-Molded, Automotive Seatbacks
Extrusion blow-molding of very large parts such as those used in the automotive industry can exceed the melt strength limits of the polymer or polymer blend of choice. This study was undertaken to define new rheological tests capable of defining the maximum parison weight a material can maintain in the blow-molding process at a given die dimension and temperature. In addition, this is balanced with 1) measurements of the extent of shear thinning as it relates to shear heating that reduces melt strength and 2) measurements of strain recovery that add to the parison weight required to achieve a given length. These rheological measurements are combined with the mechanical properties required to meet specific automotive material specifications as responses in a design of experiments approach to polymer development. Compositional factors associated with PC/ABS blends were defined to successfully produce a model predicting both the ability to fabricate a part from a 30 lb. parison as well as have the mechanical properties necessary to meet the requirements of the European Luggage Retention impact standard for a seatback.
Molecular Weight Distribution Prediction Of Rheology Against Gel Permeation Chromatography For Film Grade Polypropylene
General purpose isotactic polypropylene (iPP) grades are not very suitable for processing operations subjected to sever elongation flow field due to their tension thinning behavior and low melt strength of their essentially linear nature. Yet, by some modification in their structure, or even changing the shaping process design, they may be readily be used in processes such as blow molding, fiber spinning, BOPP processing, etc. In this work, suitability and molecular structure requirement of two commercial PP homo-polymer film grades for slit-die extrusion were investigated. Molecular weight distribution (MWD), as the main parameter to describe the molecular structure of a linear polymer, of these resins were evaluated through measurements of GPC and rheology. From their dynamic shear data the relaxation spectra, h(τ), were calculated from which MWD was estimated using molecular viscoelastic theories and then compared with the GPC results. Generally good agreement, but with narrower MWD rheology curves was found. Exception was observed for the grade for which rheological data predicted bimodal distribution curve comprising a small shoulder of high MW, not seen in the corresponding GPC curve. A higher value of the generalized mixing parameter than that of the double reptation model which was found for this bimodal grade was attributed to an increase in the number of entanglements and better network connectivity.
Effect Of Salt Addition On Dynamic Mechanical Properties For Poly(Methyl Methacrylate)
The effect of the addition of a metal salt compound with low molecular weight on the glass transition temperature Tg was investigated using poly(methyl methacrylate) (PMMA). Lithium trifluoromethanesulfonate was found to be miscible with PMMA and thus the blends show excellent transparency. Furthermore, the Tg shift to high temperature as well as the modulus enhancement in the glassy region were detected by the addition of the salt. The electrostatic interaction between PMMA and the salt is responsible for the phenomenon. Furthermore, it was found from the oscillatory shear modulus measurements beyond Tg that rheological terminal region is clearly detected in the blend without a secondary plateau.
Synergistic Absorption Of Microwave Radiation In Pvdf Hybrid Nanocomposites Containing Multiwall Carbon Nanotubes And Ferrite Particles
This study presents absorption driven attenuation of microwave radiation in polyvinylidene fluoride (PVDF) nanocomposites facilitated by conducting multiwall carbon nanotubes (MWNTs) and ferrite particles. Electromagnetic interference (EMI) shielding was achieved via a large dielectric loss arising from electrical conductivity (associated with networks of MWNTs) and magnetic loss stemming from ferrite particles. Two different types of ferrites (i.e., nickel ferrite and cobalt ferrite) were synthesized and employed for absorption of microwave radiation. When ferrite particles along with MWNTs were incorporated in PVDF matrix, cobalt ferrites depicted the highest shielding effectiveness. Moreover, the effect of network formation of fillers in PVDF matrix was analyzed by rheology and the correlation of rheological properties with microwave attenuation was studied. The underlying mechanism of microwave absorption in these nanocomposites was systematically assessed with the help of complex permittivity and permeability in X-band frequency, as the X-band frequency range is essential for major commercial applications.
Modification Of Rheological And Crystallization Properties Of High Performance Polymers For Thermoplastic Composite Applications
Continuous fiber reinforced thermoplastic composites offer many advantages over thermoset composites, including longer shelf lives of raw materials, faster processing times, design freedom, and the ability to recycle. High performance resins offer high use temperature and excellent mechanical properties in composites, however they present the challenges of high processing temperatures and melt viscosities. Polyhedral oligomeric silisesquioxane (POSS) nanostructured chemicals offer the opportunity to enhance melt flow and increase crystallization rates in polymer systems when they can be dispersed at the nano-level. We describe the rheological and crystallization performance of POSS blends with PPS and PEEK resins.
Nonlinear Viscoelastic Fluid Models With Fractal Time Derivative
In this paper, we present a viscoelastic fluid formulation containing fractal time derivative. We demonstrate that the inclusion of fractality allows one to model multiscale effects of typical viscoelastic fluids, overcoming undesired stationary predictions and reducing or even eliminating multiple modes in data fitting. The linear version of the fractal model is scaled up to large deformation by incorporation of objective rotation in the constitutive formulation. The resulting model having five model parameters (one for degree of fractality, two for linear viscoelasticity, one for straining, and the last one for rotation) is able to fit startup shear viscosity of a high molecular weight polystyrene solution in high accuracy, and yet using only a single mode.
The Effects Of Metal Stearates On The Rheological Properties Of Powder Injection Molding Feedstocks And Resulting Molded Green Parts
The effects of adding metal stearates to a powder injection molding (PIM) feedstock prepared with a wax based binder system and silicon powder was investigated. The rheological properties and molding properties of the feedstocks were characterized. Predictive viscosity models were developed for each feedstock. The zero-shear viscosity was constant with the introduction of metal stearates while, the yield stress was seen to decrease. The molded green parts were produced with a traditional injection molding process. The surface quality of the molded green parts did not seem to change. The quality through the thickness changed as vacuum voids started to form with the introduction of the metal stearates.
A Mechanistic Model For Nanocavity Filling
In this paper, we present an analytical study on the influences of different competing factors on the nanocavity filling process. Particularly, various dimensionless groups are defined to gauge into the size effects in nanocavity filling. A mechanistic model for nanochannel flow is formulated on the basis of disentanglement between molecular layers. The focus was placed on determining the major enabling factors for achieving cavity fill in an extremely short imprinting period on the order of 1 second. It is found that a high-energy mold surface is necessary in roll-to-roll imprinting where the contact time is extremely short and a high imprint pressure is difficult to apply. Additionally, in-mold solidification must be incorporated in precision replication, suppressing shape distortion caused by elastic recovery.
How Plastics Helps To Conquer The New Challenges Of Vehicle Electrification
How plastics helps to conquer the new challenges of vehicle electrificationbyMelanie Mennigke; LG Chem - Key Account ManagerWerner Posch; Dräxlmaier Group - Material ManagementThe need for zero emission solutions is steadily increasing and OEMs are currently developing battery electric vehicles with a focus on providing emission-free transportation, combined with lowest total cost of ownership. The main challenges for these vehicles include: range; cost and weight.Electric vehicles are no longer a trend but an established fact. In order to make the correct decision on which technological approach – BEV (battery electric vehicle) or REEV (range extended electric vehicle) - best meets the requirements of the market, the manufacturers specific boundary conditions and economic aspects have to be balanced with a multidisciplinary approach. The development of alternative drive vehicles is driven by both consumer and government demand. Consumers want fuel-efficient, low-emission vehicles, but they do not want to pay a premium to drive a more sustainable car. Governments want improved fuel economy and low emissions, and go as far as using manufacturer tax credits and consumer write-offs to incentivize alternative drive vehicle development. However, for a solution to be truly sustainable, it must be economically feasible, as well as environmentally sound.As the market grows for hybrid-powered and electric vehicle technology, plastics play an ever more important role to help reduce carbon emissions and dependence on petroleum. The challenges of using plastics in electric vehicle technology are: • Use of plastics instead of aluminum and steel for weight reduction• Use high-performance polymers and elastomers to integrate components and functions — this miniaturization reduces space and improves packaging.• Improve battery pack performance with flame-retardant and thermoplastic materials.• Prevent electrical arcs and sparks in connectors with thermoplastic materials that meet 650-volt system requirements.• Provide electromagnetic compatibility (EMC) The presentation includes proved plastics solutions for challenges described above. Examples of developed and already in serial production electric power trains (High-voltage battery systems, power electronics,...) to identify the right plastics for design and serial production which fulfil requirements such flame resistance, EMI shielding, weight reduction,... So that automakers can build hybrid and electric vehicles that meet consumer and environmental needs.
Connecting Rheology Of Polyolefin Elastomers To Dispersion In A Polypropylene Matrix Via Modeling And Experiments With Simple Flow Fields
Controlling the dispersion of polyolefin elastomers in polypropylene is critical for applications requiring low temperature impact toughness, such as for automotive TPO compounds. To better understand the role of polyolefin elastomer design and rheology on dispersion in polypropylene resins, a computational fluid dynamics model was developed to study the effect of viscoelastic behavior on particle breakup in simple flow fields. This model was applied to breakup of polyolefin elastomers with different rheological features in a high flow polypropylene matrix. Experiments were conducted with similar blends under comparable simple flow fields to validate the results of the model. The learnings were then applied to a simple TPO compound produced with typical twin screw extrusion and injection molding, demonstrating the benefits of a particular elastomer rheology on dispersion and impact toughness properties, and validating the utility of the computational fluid dynamics model to help guide polyolefin elastomer resin design.
Recycled And Waste Materials In Selected Automotive Applications
Recycled and Waste Materials in Selected Automotive ApplicationsKarnik Tarverdi, Peter S Allan & Paul J Marsh,Wolfson Centre for Materials Processing, Brunel University London,Institute of Materials and Manufacturing, United KingdomAbstractThe objective of this project was to investigate the potential use of recycled and waste materials in automotive components. Few components were selected for the investigation. All of them had the potential to be manufactured from waste and recycled materials. The trial materials which included recycled polypropylene and an industrial particulate solid waste stream, were processed into prototype components that were evaluated and compared with the respective production counterparts.The overall results indicated a clear potential for the use of the project materials in their respective applications.
Development Of Low Emission Polyolefin Composites For Automotive Interiors
Low Emission products are highly sought after in the automotive industry for interior applications which include measuring Odor and Fog, Volatile Organic Compounds (VOC’s) and Semi-Volatile Organic Compounds (SVOC’s). A. Schulman, Inc has developed glass and mineral filled composites that meet the regulatory requirements for VOC’s and SVOC’s in GMW and VW specs through a careful selection of base polypropylenes, additives and compounding technology which will be presented in this work. The development included a careful selection of resins, targeted additive strategy and an appropriate process to minimize the VOC and SVOC count measure via chromatography on the final compound.
Low Birefringent Cellulose Acetate Propionates For Plastic Display Lens Covers
The fusion of electronics with glass and plastics to create smart surfaces with a harmonious luxury ambiance is creating a flurry of development activity which is changing the driver/passenger experience in the transportation industry. Merging human machine interface (HMI) displays, controls, and knobs with other decorative plastic components is being driven in part by the desire to reduce/eliminate distractions (safety) in addition to bringing a stylish atmosphere which increases consumer satisfaction. For displays, the desire to move away from the typical two dimensional 7- inch rectangular shape towards larger and different shapes (curved and non-rectangular) becomes a challenge in and of itself because glass has a lower design freedom for forming curvature and tempered glass is considered costly. Plastic covered displays are easier to produce 3 dimensional shapes via either injection molding or vacuum lamination of films, and their light transmitting abilities are similar to glass. As is observed with some glass display surfaces, certain plastics are also prone to birefringence caused by molded in stress which contributes to poor distinctness of image and reading legibility. Choice of polymer and glass surfaces for integrated HMI displays in instrument and door panels, or seat backs is the center of attention given the vast number of requirements of the automotive industry. This paper will focus on the characteristics of bio-based, low birefringent cellulose acetate propionate (CAP) as potential HMI-lens covers in comparison to other clear polymers.
Dynamic Water Penetration Prediction For Push-Back Process In Water-Assisted Injection Molding
Water-assisted injection molding (WAIM) process has brought a breakthrough development for the traditional injection molding industry. The water cores out a network of hollow channels throughout the mold cavity to reduce the cost of energy and plastic evidently. In the recent years, the improvements both in the numerical methods and computer hardware have promoted the application of CAE in the modeling of the injection molding process. The major drawbacks of the Hele-Shaw approximation, commonly used today as a means of simplifying the simulation of WAIM process, are the inherent loss of the ability to predict the important physical three-dimensional phenomena for water penetration such as blow-out behavior, corner effect and secondary penetration. This study presents an implicit finite volume approach to simulate the three-dimensional mold filling problems encountered during the water-assisted injection molding. Full shot WAIM processes push-back molding process verify mutually with the experimental results on industrial applications. The results show that our novel three-dimensional numerical model is able to predict the complex water penetration behaviors in the real mold and the predictions are also consistent with the experimental results to further verify the accuracy of our approach.
Effect Of Grain Pattern And Talc Content On Scratch And Mar Behaviors Of Textured Thermoplastic Olefins
An investigation on the effect of talc content and grain pattern on the scratch and mar behavior of textured thermoplastic olefins (TPO) samples is reported. A set of model TPO samples with different grain pattern and talc content were provided by Nissan Motors (USA) Co., Ltd. Scratch and mar tests were carried out on these TPO samples according to the ASTM D7027-13 standard. The visibilities of the scratch and mar damages were evaluated by a contrast-based methodology, and found to correlate well with human assessment. The grain pattern and talc content are found to have significant effect on mar visibility resistance of TPO. Issues related to mar evaluation methodology and material science on improvement of mar resistance are discussed.
Vehicle Lightweighting And Improved Crashworthiness - Plastics And Hybrid Solutions
“Worldwide, efforts are underway to save lives and reduce vehicle repair and other economic and social costs that result from motor vehicle crashes. At the same time, also worldwide, automakers are grappling with increasingly stringent fuel economy requirements. The difficulties involved in reconciling these two objectives – designing vehicles that are lighter to improve fuel-efficiency, but also more crashworthy – can seem daunting. This presentation addresses the conundrum head on with a discussion and overview of different multi-material body-in-white (BIW) weight reduction opportunities. The BIW is an obvious choice for vehicle lightweighting as this structure contributes more than 30 to 35 percent of the total weight of a car. Using engineering thermoplastic and hybrid solutions at appropriate locations on a vehicle’s BIW, automakers can achieve significant weight savings without compromising crash performance. To illustrate, this presentation provides a detailed case study on an award-winning floor rocker reinforcement. Also covered are several other lightweight solutions for applications like A/B pillars and bumper rail extensions.”
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