An Approach to the Modeling of Mixing of Elastomers

1981 ◽  
Vol 54 (2) ◽  
pp. 266-276 ◽  
Author(s):  
N. Nakajima
Keyword(s):  
Carbon Black ◽  
Flow Behavior ◽  
Practical Importance ◽  
Scale Up ◽  
Intermediate Stage ◽  
Material Behavior ◽  
Raw Material ◽  
Dynamic Visualization ◽  
Scale Temperature ◽  
Internal Mixer

Abstract In recent years, the process of mixing elastomers with carbon black has been the subject of various studies. In particular, the process involving the use of the internal mixer has been examined systematically, and Palmgren has published a general review on the state of the art. A method was proposed for the control and scale-up which is based on the energy input for mixing; then, properties were evaluated as a function of the mixing energy. This method was used for evaluating the performance of different types of elastomers and carbon blacks in the internal mixer. Although the method represents significant progress in understanding the mixing process and is of practical importance, it still treats the mixer essentially as a “black box”. In order to elucidate the mechanism of mixing, visualization must be performed. One type is static visualization, in which the machine is stopped at an intermediate stage and the contents are taken out for inspection. Another is dynamic visualization through transparent walls of a mixer. These observations enable us to construct a model for the deformation-flow behavior of materials and a model for the mixing mechanism. These models, in turn, guide us to laboratory measurements of the material behavior which are pertinent to the mixing mechanisms. With respect to mill processability, Tokita and White classified raw material behavior into four regions, which are functions of a given material and dependent on the time scale, temperature, and magnitude of strain. This classification is applicable not only to the millability of the raw elastomer but also to the ease of mixing with carbon black. This interpretation may be extended to the processability of the material in the internal mixer.

The Dispersion of Carbon Black in Rubber Part I. Rapid Method for Assessing Quality of Dispersion

1992 ◽  
Vol 65 (5) ◽  
pp. 973-997 ◽  
Author(s):  
A. Y. Coran ◽  
J-B. Donnet
Keyword(s):  
Carbon Black ◽  
Mixing Time ◽  
Poor Performance ◽  
Raw Material ◽  
Rubber Part ◽  
Reproducible Method ◽  
Internal Mixer ◽  
Kinetics Of ◽  
Carbon Black Dispersion

Abstract Carbon black is the most important reinforcing filler for rubbers. The incorporation of carbon black into rubber vulcanizates generally gives improved strength, extensibility, fatigue resistance, abrasion resistance, etc. In order to exert its beneficial influence on the properties of rubber vulcanizates, the carbon black must be sufficiently dispersed therein. Indeed, poor dispersion can, in itself, give rise to detrimental effects (e.g. reduced product life, poor performance in service, poor product appearance, poor processing characteristics, poor product uniformity, raw-material waste, high finished-product rejection rates, and excessive energy usage). These inadequacies are generally the result of the presence of rather large, undispersed agglomerates. The present work was initiated in order to develop an improved understanding of the carbon-black dispersion process including the understanding of factors which affect the kinetics of dispersion. The work described here is focused on methodology for reproducibly mixing carbon black with rubber in the laboratory, and reproducibility, but rapidly and easily estimating the degree of dispersion of the carbon black into the rubber as a function of mixing time. Procedures were developed for introducing rubber, filler, and other ingredients into a small, laboratory internal mixer and for mixing the batches for various periods of time. Also, an improved, simple-to-use, reproducible method for determining the degree of carbon black dispersion in rubber has been adapted. The extent of dispersion was correlated with various measures of tensile strength and with other performance-related properties.

scholarly journals Rheological Characterization of a Concentrated Phosphate Slurry

Fluids ◽  
2021 ◽  
Vol 6 (5) ◽  
pp. 178
Author(s):  
Souhail Maazioui ◽  
Abderrahim Maazouz ◽  
Fayssal Benkhaldoun ◽  
Driss Ouazar ◽  
Khalid Lamnawar
Keyword(s):  
Flow Behavior ◽  
Continuous Phase ◽  
Raw Material ◽  
Rheological Characterization ◽  
Phosphate Ore ◽  
Insoluble Particles ◽  
Experimental Protocols ◽  
Solid Liquid

Phosphate ore slurry is a suspension of insoluble particles of phosphate rock, the primary raw material for fertilizer and phosphoric acid, in a continuous phase of water. This suspension has a non-Newtonian flow behavior and exhibits yield stress as the shear rate tends toward zero. The suspended particles in the present study were assumed to be noncolloidal. Various grades and phosphate ore concentrations were chosen for this rheological investigation. We created some experimental protocols to determine the main characteristics of these complex fluids and established relevant rheological models with a view to simulate the numerical flow in a cylindrical pipeline. Rheograms of these slurries were obtained using a rotational rheometer and were accurately modeled with commonly used yield-pseudoplastic models. The results show that the concentration of solids in a solid–liquid mixture could be increased while maintaining a desired apparent viscosity. Finally, the design equations for the laminar pipe flow of yield pseudoplastics were investigated to highlight the role of rheological studies in this context.

scholarly journals Scaling Up Delivery of Biofortified Staple Food Crops Globally: Paths to Nourishing Millions

2021 ◽  
pp. 037957212098250
Author(s):  
Jennifer K. Foley ◽  
Kristina D. Michaux ◽  
Bho Mudyahoto ◽  
Laira Kyazike ◽  
Binu Cherian ◽  
...  
Keyword(s):  
Pearl Millet ◽  
Large Scale ◽  
Scale Up ◽  
Lessons Learned ◽  
Raw Material ◽  
Micronutrient Deficiencies ◽  
Seed Systems ◽  
Public And Private ◽  
Context Specific ◽  
Public And Private Sector

Background: Micronutrient deficiencies affect over one quarter of the world’s population. Biofortification is an evidence-based nutrition strategy that addresses some of the most common and preventable global micronutrient gaps and can help improve the health of millions of people. Since 2013, HarvestPlus and a consortium of collaborators have made impressive progress in the enrichment of staple crops with essential micronutrients through conventional plant breeding. Objective: To review and highlight lessons learned from multiple large-scale delivery strategies used by HarvestPlus to scale up biofortification across different country and crop contexts. Results: India has strong public and private sector pearl millet breeding programs and a robust commercial seed sector. To scale-up pearl millet, HarvestPlus established partnerships with public and private seed companies, which facilitated the rapid commercialization of products and engagement of farmers in delivery activities. In Nigeria, HarvestPlus stimulated the initial acceptance and popularization of vitamin A cassava using a host of creative approaches, including “crowding in” delivery partners, innovative promotional programs, and development of intermediate raw material for industry and novel food products. In Uganda, orange sweet potato (OSP) is a traditional subsistence crop. Due to this, and the lack of formal seed systems and markets, HarvestPlus established a network of partnerships with community-based nongovernmental organizations and vine multipliers to popularize and scale-up delivery of OSP. Conclusions: Impact of biofortification ultimately depends on the development of sustainable markets for biofortified seeds and products. Results illustrate the need for context-specific, innovative solutions to promote widespread adoption.

Constitutive modeling for the mechanical behavior of rubber with filler particles

2021 ◽  
Author(s):  
Sankalp Gour ◽  
Deepu Kumar Singh ◽  
Deepak Kumar ◽  
Vinod Yadav
Keyword(s):  
Mechanical Properties ◽  
Carbon Black ◽  
Mechanical Behavior ◽  
Experimental Observation ◽  
Continuum Mechanics ◽  
Constitutive Modeling ◽  
Carbon Nanoparticles ◽  
Material Behavior ◽  
Experimental Results ◽  
Filler Particles

Abstract The present study deals with the constitutive modeling for the mechanical behavior of rubber with filler particles. An analytical model is developed to predict the mechanical properties of rubber with added filler particles based on experimental observation. To develop the same, a continuum mechanics-based hyperelasticity theory is utilized. The model is validated with the experimental results of the chloroprene and nitrile butadiene rubbers filled with different volume fractions of carbon black and carbon nanoparticles, respectively. The findings of the model agree well with the experimental results. In general, the developed model will be helpful to the materialist community working in characterizing the material behavior of tires and other rubber-like materials.

scholarly journals WEEE collection and CRM recovery trials: piloting a holistic approach for Scotland

2018 ◽  
Vol 20 (4) ◽  
pp. 712-718
Keyword(s):  
Raw Materials ◽  
Scale Up ◽  
Holistic Approach ◽  
Extraction Methods ◽  
Social Enterprises ◽  
Raw Material ◽  
Household Waste ◽  
Sustainable Supply Chain ◽  
Gold Silver ◽  
Critical Raw Materials

<p>Re-Tek UK and its partners, Enscape Consulting and the University of West of Scotland commenced trials for the collection and recovery of critical raw materials from waste electrical and electronic (WEEE) products in July 2016. Sponsored by the EU LIFE funded project ‘Critical Raw Material Closed Loop Recovery’ coordinated by WRAP with EARN, ERP UK Ltd, KTN Ltd and Wuppertal Institute as beneficiaries. The trials are aimed at boosting the recovery of critical raw materials (CRMs) from household waste electrical and electronic products (WEEE) and Information Communications Technology (ICT) in particular, after functioning equipment is separated out for re-use. The new collection models provided residents with the opportunity to drop-off unwanted electrical and electronic appliances at a time and place that suits them, through a collaborative approach which encourages local authorities, educational establishments, businesses, and Social Enterprises, etc to act as hub sites. Hubs were designed to minimize product damage and encourage drop-off, rather than hoarding. Extraction methods developed after the collection phase of the trial looked at the opportunity to recover cobalt, gold and silver from ICT products, with the potential to inform how a more sustainable supply chain could be developed in Scotland. The elements studied were selected to demonstrate financial opportunity (gold/silver) and a strategic priority material (cobalt) for long term supply. These are based on bioleaching and electrochemical recovery using novel carbon based electrode systems, and chemical processing methods using extraction techniques with an assessment of pilot performance and scale up challenges. Our report is on the state of progress towards practical solutions to WEEE and CRM recovery.</p>

Scale-Up of Short Fiber Composite Mixing

1979 ◽  
Vol 52 (4) ◽  
pp. 764-772 ◽  
Author(s):  
K. S. Shen ◽  
R. K. Rains
Keyword(s):  
Fiber Composite ◽  
Mixing Time ◽  
Scale Up ◽  
Short Fiber ◽  
Probable Number ◽  
Time Required ◽  
Internal Mixer ◽  
Relationship Of ◽  
Short Fiber Composite ◽  
Number Of Passes

Abstract A dimensionless parameter, NRS, based on the probable number of passes through the shear zone for an ingredient to be dispersed, was developed for scale-up of mixing of short fiber composite in an internal mixer. A single curve was obtained for the dispersion-NRS relationship of three widely different compounds in five internal mixers of various sizes. The parameter is an improvement over previously reported scale-up parameters, because the temperature profile does not have to be matched for different size mixers. The dimensionless dispersion number concept can be extended to dispersion of other ingredients, as long as the shear stress generated at the mixing temperature is higher than the interaggregate cohesive force of the particles. Based on this parameter, NRS, the dispersion of short fibers can be predicted from one size of internal mixer to another size mixer. It is also possible to predict the mixing time required for a given dispersion rating.

THERMOREVERSIBLE CROSS-LINKING OF RUBBER COMPOUNDS: FROM PROOF-OF-CONCEPT TOWARD AN INDUSTRIAL PROCESS

2018 ◽  
Vol 91 (2) ◽  
pp. 492-508 ◽  
Author(s):  
L. M. Polgar ◽  
J. Keizer ◽  
R. Blom ◽  
B. Niemeijer ◽  
T. de With ◽  
...  
Keyword(s):  
Carbon Black ◽  
Material Properties ◽  
Industrial Process ◽  
Mineral Oil ◽  
Diels Alder ◽  
Cross Linking ◽  
Proof Of Concept ◽  
Rubber Compounds ◽  
Internal Mixer ◽  
Batch Mixer

ABSTRACT It is demonstrated that the concept of thermoreversible cross-linking of functionalized maleic anhydride grafted ethylene–propylene (EPM-g-MA) rubber using Diels–Alder chemistry is limited neither to laboratory scale using a solvent route nor to gum rubber. The use of an internal mixer is the first step toward an industrial process, since it greatly reduces the processing time and allows for a solventless process for the furan-functionalization and subsequent bismaleimide cross-linking of EPM rubber. Practical rubber compounds were prepared by mixing thermoreversibly cross-linked EPM with carbon black and mineral oil in the same batch mixer. This resulted in reinforcement of the rubber without affecting the thermoreversible character of the cross-linking. The pendant furan groups of the (non)cross-linked EPM-g-furan interact with the carbon black filler. Finally, crystalline EPM rubber compounds were prepared, which show excellent material properties and property retention over multiple reprocessing cycles.

scholarly journals Johnson Cook Material and Failure Model Parameters Estimation of AISI-1045 Medium Carbon Steel for Metal Forming Applications

Materials ◽  
2019 ◽  
Vol 12 (4) ◽  
pp. 609 ◽  
Author(s):  
Mohanraj Murugesan ◽  
Dong Jung
Keyword(s):  
Flow Stress ◽  
Metal Forming ◽  
Flow Behavior ◽  
Medium Carbon Steel ◽  
Material Behavior ◽  
Model Parameters ◽  
Stress Model ◽  
Medium Carbon ◽  
Aisi 1045 ◽  
Flow Stress Model

Consistent and reasonable characterization of the material behavior under the coupled effects of strain, strain rate and temperature on the material flow stress is remarkably crucial in order to design as well as optimize the process parameters in the metal forming industrial practice. The objective of this work was to formulate an appropriate flow stress model to characterize the flow behavior of AISI-1045 medium carbon steel over a practical range of deformation temperatures (650–950 ∘ C) and strain rates (0.05–1.0 s − 1 ). Subsequently, the Johnson-Cook flow stress model was adopted for modeling and predicting the material flow behavior at elevated temperatures. Furthermore, surrogate models were developed based on the constitutive relations, and the model constants were estimated using the experimental results. As a result, the constitutive flow stress model was formed and the constructed model was examined systematically against experimental data by both numerical and graphical validations. In addition, to predict the material damage behavior, the failure model proposed by Johnson and Cook was used, and to determine the model parameters, seven different specimens, including flat, smooth round bars and pre-notched specimens, were tested at room temperature under quasi strain rate conditions. From the results, it can be seen that the developed model over predicts the material behavior at a low temperature for all strain rates. However, overall, the developed model can produce a fairly accurate and precise estimation of flow behavior with good correlation to the experimental data under high temperature conditions. Furthermore, the damage model parameters estimated in this research can be used to model the metal forming simulations, and valuable prediction results for the work material can be achieved.

scholarly journals A Development Methodology for Copper End Termination Paste — Part 1: Origin of Green Defects

2002 ◽  
Vol 25 (2) ◽  
pp. 169-179 ◽  
Author(s):  
Umesh Kumar
Keyword(s):  
Material Selection ◽  
Flow Behavior ◽  
Process Condition ◽  
Viscoelastic Behavior ◽  
Acrylic Resin ◽  
Nitrogen Atmosphere ◽  
Raw Material ◽  
Development Methodology ◽  
Drying Conditions ◽  
Raw Material Selection

Copper (Cu) based pastes have emerged as the termination materials of choice for ceramic capacitors with base metal internal electrodes. To prevent oxidation of nickel (Ni) internal electrode and the copper terminations, it is necessary to fire the terminations in a nitrogen atmosphere. This requirement places significant restrictions on raw material selection for the termination pastes. For example, acrylic-based resins are used as organic binder for their clean burning characteristics over the traditional ethyl cellulose based binder system. As the viscoelastic behavior of acrylic resin systems are different to those of cellulose systems, differences are observed in the flow behavior of the paste. In this paper, the influence of paste rheology on the green cosmetic defects such as mooning, peaking, etc. is discussed. Additionally, the influence of process condition such as dipping parameters, drying conditions etc., on the green cosmetic defects are discussed. Finally, properties of a copper termination, which can be processed between 800–825°C, are discussed.

Sign in / Sign up

Export Citation Format

Share Document