Numerical analysis of slot die coating of nanocellulosic materials

Nanocellulosic coatings as a food packaging material are of commercial interest due to their nontoxic nature, renewability, and excellent barrier properties. Complex shear-thinning rheology poses challenges in designing and sizing equipment to pump, mix, and process the suspension and actual coating process. This study aims to determine the effectiveness of computational fluid dynamics (CFD) in predicting nanocellulosic suspension flow in light of existing rheological data. We employ and compare three distinct rheological models to characterize the rheology and flow of nanocellulose suspensions through a slot die coater, where the model parameters are established from existing slot rheometry measurements. A volume-of-fluid (VoF) based finite volume method is employed to simulate the flow in a slot die operated in an unconventional metering mode. Results with the Casson model predict the presence of unyielded regions in the flow, which was not captured using the power law model. These stagnation regions will incur coatability issues stemming from flow intermittencies and lead to potential defects in the coating layer, including fracture. The results suggest that a rheological model that includes yield stress should be considered while modeling such flows. A need for better rheological data to model nanocellulosic flows, especially at high consistencies and shear rates, is also highlighted.

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Assessment of the Tumbling-Snake Model against Linear and Nonlinear Rheological Data of Bidisperse Polymer Blends

Polymers ◽

10.3390/polym11020376 ◽

2019 ◽

Vol 11 (2) ◽

pp. 376 ◽

Cited By ~ 1

Author(s):

Pavlos Stephanou ◽

Martin Kröger

Keyword(s):

Brownian Dynamics ◽

Stationary Solutions ◽

Model Parameters ◽

Snake Model ◽

Shear Rates ◽

Rheological Data ◽

Wide Range ◽

Dynamics Simulations ◽

Brownian Dynamics Simulations ◽

Entangled Melts

We have recently solved the tumbling-snake model for concentrated polymer solutions and entangled melts in the academic case of a monodisperse sample. Here, we extend these studies and provide the stationary solutions of the tumbling-snake model both analytically, for small shear rates, and via Brownian dynamics simulations, for a bidisperse sample over a wide range of shear rates and model parameters. We further show that the tumbling-snake model bears the necessary capacity to compare well with available linear and non-linear rheological data for bidisperse systems. This capacity is added to the already documented ability of the model to accurately predict the shear rheology of monodisperse systems.

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Effects of composition, temperature and shear rate on chocolate milk rheology: an empirical modeling approach incorporating yield behavior

International Journal of Food Engineering ◽

10.1515/ijfe-2019-0289 ◽

2021 ◽

Vol 0 (0) ◽

Author(s):

Asif A. Qaiser ◽

Rabia Nazar ◽

Mehroz Anjum ◽

Anem Saeed ◽

Muhmmad Zeeshan ◽

...

Keyword(s):

Xanthan Gum ◽

Model Fitting ◽

Empirical Modeling ◽

Rheological Parameters ◽

Model Parameters ◽

Chocolate Milk ◽

Rheological Models ◽

Shear Rates ◽

Milk Processing ◽

Semi Empirical

Abstract This study elucidates the effects of composition and temperature on the rheological behavior of chocolate milk formulation. The fat [0.5, 1 and 1.5 g] and xanthan gum contents [0.05, 0.1 and 0.15 g] varied and shear stress-strain rate data were recorded at varying temperature [21.4, 65 and 80 °C]. All compositions showed predominantly a pseudoplastic behavior [i.e., pseudoplasticity index, n < 1] with a strong influence on composition and temperature. Three semi-empirical rheological models, i.e. Power-law, Herschel–Bulkely, and Casson models were fitted on the data using an in-house developed computer program for the best statistical fit. The pseudoplasticity index [n] varied with the composition that initially decreased with temperature and subsequently increased. The other model parameters such as consistency index [k], Casson and Herschel–Bulkely yield stress, and Casson viscosity [at a specified rate i.e., 34.7 s−1] were computed through model fitting and correlated to the microstructural changes inside the fluid keeping in view the composition and temperature. This study helps in correlating chocolate milk processing and quality control based on complex microstructure to the rheological parameters measured at simulated temperatures and shear rates.

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Low-Density Polyethylene Films Carrying ferula asafoetida Extract for Active Food Packaging: Thermal, Mechanical, Optical, Barrier, and Antifungal Properties

Advances in Polymer Technology ◽

10.1155/2020/4098472 ◽

2020 ◽

Vol 2020 ◽

pp. 1-15

Author(s):

Razieh Niazmand ◽

Bibi Marzieh Razavizadeh ◽

Farzaneh Sabbagh

Keyword(s):

Polymer Matrix ◽

Food Packaging ◽

Barrier Properties ◽

Low Density Polyethylene ◽

Low Density ◽

Optical Barrier ◽

Leaf Extracts ◽

Polyethylene Films ◽

Active Food Packaging ◽

Ferula Asafoetida

The physical, thermal, mechanical, optical, microstructural, and barrier properties of low-density polyethylene films (LDPE) containing ferula asafoetida leaf and gum extracts were investigated. Results showed a reduction in elasticity and tensile strength with increasing extract concentration in the polymer matrix. The melting temperature and enthalpy increased with increasing concentration of extracts. The films containing extracts had lower L∗ and a∗ and higher b∗ indices. The films containing leaf extract had more barrier potential to UV than the gum extracts. The oxygen permeability in films containing 5% of leaf and gum extracts increased by 2.3 and 2.1 times, respectively. The morphology of the active films was similar to bubble swollen islands, which was more pronounced at higher concentrations of gum and leaf extracts. FTIR results confirmed some chemical interactions of ferula extracts with the polymer matrix. At the end of day 14th, the growth rate of Aspergillus niger and Saccharomyces cerevisea in the presence of the PE-Gum-5 reduced more than PE-Leaf-5 (3.7 and 2.4 logarithmic cycles, respectively) compared to the first day. Our findings showed that active LDPE films have desire thermo-mechanical and barrier properties for food packaging.

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Effects of mesh loop modes on performance of unstructured finite volume GPU simulations

Advances in Aerodynamics ◽

10.1186/s42774-021-00073-y ◽

2021 ◽

Vol 3 (1) ◽

Author(s):

Yue Weng ◽

Xi Zhang ◽

Xiaohu Guo ◽

Xianwei Zhang ◽

Yutong Lu ◽

...

Keyword(s):

Finite Volume ◽

Data Access ◽

Data Locality ◽

Data Dependence ◽

Speed Up ◽

Computational Fluid Dynamics Cfd ◽

Overall Performance ◽

Volume Method ◽

Cell Data ◽

Unstructured Finite Volume Method

AbstractIn unstructured finite volume method, loop on different mesh components such as cells, faces, nodes, etc is used widely for the traversal of data. Mesh loop results in direct or indirect data access that affects data locality significantly. By loop on mesh, many threads accessing the same data lead to data dependence. Both data locality and data dependence play an important part in the performance of GPU simulations. For optimizing a GPU-accelerated unstructured finite volume Computational Fluid Dynamics (CFD) program, the performance of hot spots under different loops on cells, faces, and nodes is evaluated on Nvidia Tesla V100 and K80. Numerical tests under different mesh scales show that the effects of mesh loop modes are different on data locality and data dependence. Specifically, face loop makes the best data locality, so long as access to face data exists in kernels. Cell loop brings the smallest overheads due to non-coalescing data access, when both cell and node data are used in computing without face data. Cell loop owns the best performance in the condition that only indirect access of cell data exists in kernels. Atomic operations reduced the performance of kernels largely in K80, which is not obvious on V100. With the suitable mesh loop mode in all kernels, the overall performance of GPU simulations can be increased by 15%-20%. Finally, the program on a single GPU V100 can achieve maximum 21.7 and average 14.1 speed up compared with 28 MPI tasks on two Intel CPUs Xeon Gold 6132.

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Evolution of biobased and nanotechnology packaging – a review

Nordic Pulp & Paper Research Journal ◽

10.1515/npprj-2020-0042 ◽

2020 ◽

Vol 35 (4) ◽

pp. 491-515

Author(s):

Tom Lindström ◽

Folke Österberg

Keyword(s):

Biodegradable Polymers ◽

Food Packaging ◽

Environmental Issues ◽

Barrier Properties ◽

Environmental Problems ◽

Layer By Layer ◽

Polyelectrolyte Complexes ◽

Life Issues ◽

Technological Developments ◽

End Of Life Issues

AbstractThis review deals with the evolution of bio-based packaging and the emergence of various nanotechnologies for primary food packaging. The end-of life issues of packaging is discussed and particularly the environmental problems associated with microplastics in the marine environment, which serve as a vector for the assimilation of persistent organic pollutants in the oceans and are transported into the food chain via marine and wild life. The use of biodegradable polymers has been a primary route to alleviate these environmental problems, but for various reasons the market has not developed at a sufficient pace that would cope with the mentioned environmental issues. Currently, the biodegradable plastics only constitute a small fraction of the fossil-based plastic market. Fossil-based plastics are, however, indispensable for food safety and minimization of food waste, and are not only cheap, but has generally more suitable mechanical and barrier properties compared to biodegradable polymers. More recently, various nanotechnologies such as the use of nanoclays, nanocellulose, layer-by-layer technologies and polyelectrolyte complexes have emerged as viable technologies to make oxygen and water vapor barriers suitable for food packaging. These technological developments are highlighted as well as issues like biodegradation, recycling, legislation issues and safety and toxicity of these nanotechnologies.

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Rheological Properties of Wood–Plastic Composites by 3D Numerical Simulations: Different Components

Forests ◽

10.3390/f12040417 ◽

2021 ◽

Vol 12 (4) ◽

pp. 417

Author(s):

Xingcong Lv ◽

Xiaolong Hao ◽

Rongxian Ou ◽

Tao Liu ◽

Chuigen Guo ◽

...

Keyword(s):

Flow Field ◽

Rheological Properties ◽

Wood Fiber ◽

Velocity Shear ◽

Wood Plastic Composites ◽

Shear Rates ◽

Plastic Composites ◽

Power Law Fluids ◽

Field Information ◽

Computational Fluid Dynamics Cfd

The rheological properties of wood–plastic composites (WPCs) with different wood fiber contents were investigated using a rotational rheometer under low shear rates. The flow field information was analyzed and simulated by Ansys Polyflow software. The results showed that the WPCs with different wood fiber contents behaved as typical power-law fluids. A higher wood fiber content increased the shear thinning ability and pseudoplasticity of the WPCs. The pressure, velocity, shear rate, and viscosity distributions of the WPC during extrusion could be predicted by computational fluid dynamics (CFD) Ansys Polyflow software to explore the effects of different components on the flow field of WPCs.

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Nanocomposites Materials of PLA Reinforced with Nanoclays Using a Masterbatch Technology: A Study of the Mechanical Performance and Its Sustainability

Polymers ◽

10.3390/polym13132133 ◽

2021 ◽

Vol 13 (13) ◽

pp. 2133

Author(s):

Helena Oliver-Ortega ◽

Josep Tresserras ◽

Fernando Julian ◽

Manel Alcalà ◽

Alba Bala ◽

...

Keyword(s):

Food Packaging ◽

Mechanical Performance ◽

Polymeric Materials ◽

Barrier Properties ◽

Food Tray ◽

Environmental Concerns ◽

Poly Lactic Acid ◽

The Matrix ◽

Surface Modified ◽

Being Moved

Packaging consumes around 40% of the total plastic production. One of the most important fields with high requirements is food packaging. Food packaging products have been commonly produced with petrol polymers, but due to environmental concerns, the market is being moved to biopolymers. Poly (lactic acid) (PLA) is the most promising biopolymer, as it is bio-based and biodegradable, and it is well established in the market. Nonetheless, its barrier properties need to be enhanced to be competitive with other polymers such as polyethylene terephthalate (PET). Nanoclays improve the barrier properties of polymeric materials if correct dispersion and exfoliation are obtained. Thus, it marks a milestone to obtain an appropriate dispersion. A predispersed methodology is proposed as a compounding process to improve the dispersion of these composites instead of common melt procedures. Afterwards, the effect of the polarity of the matrix was analyzing using polar and surface modified nanoclays with contents ranging from 2 to 8% w/w. The results showed the suitability of the predispersed and concentrated compound, technically named masterbatch, to obtain intercalated structures and the higher dispersion of polar nanoclays. Finally, the mechanical performance and sustainability of the prepared materials were simulated in a food tray, showing the best assessment of these materials and their lower fingerprint.

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Understanding the Barrier and Mechanical Behavior of Different Nanofillers in Chitosan Films for Food Packaging

Polymers ◽

10.3390/polym13050721 ◽

2021 ◽

Vol 13 (5) ◽

pp. 721 ◽

Cited By ~ 1

Author(s):

João Pires ◽

Camila Damásio de Paula ◽

Victor Gomes Lauriano Souza ◽

Ana Luísa Fernando ◽

Isabel Coelhoso

Keyword(s):

Mechanical Properties ◽

Mechanical Behavior ◽

Food Packaging ◽

Scientific Research ◽

Barrier Properties ◽

Plastic Pollution ◽

Functional Attributes ◽

Chitosan Films ◽

Commercial Applications ◽

Innovative Techniques

The continuous petroleum-based plastics manufacturing generates disposal issues, spreading the problem of plastic pollution and its rise in the environment. Recently, innovative techniques and scientific research promoted biopolymers as the primary alternative for traditional plastics, raising and expanding global bioplastic production. Due to its unmatched biological and functional attributes, chitosan (Ch) has been substantially explored and employed as a biopolymeric matrix. Nevertheless, the hydrophilicity and the weak mechanical properties associated with this biopolymer represent a significant intrinsic restriction to its implementation into some commercial applications, namely, in food packaging industries. Distinct methodologies have been utilized to upgrade the mechanical and barrier properties of Ch, such as using organic or inorganic nanofillers, crosslinkers, or blends with other polymers. This review intends to analyze the most recent works that combine the action of different nanoparticle types with Ch films to reinforce their mechanical and barrier properties.

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Cellulose Nanofibril (CNF) Films and Xylan from Hot Water Extracted Birch Kraft Pulps

Applied Sciences ◽

10.3390/app9163436 ◽

2019 ◽

Vol 9 (16) ◽

pp. 3436 ◽

Cited By ~ 4

Author(s):

Marc Borrega ◽

Hannes Orelma

Keyword(s):

Food Packaging ◽

Kraft Pulp ◽

Barrier Properties ◽

Hot Water ◽

Kraft Pulps ◽

Cellulose Nanofibril ◽

Vapour Permeability ◽

Transparent Films ◽

Cnf Films ◽

Birch Kraft Pulp

The effects of xylan extraction from birch kraft pulp on the manufacture and properties of cellulose nanofibril (CNF) films were here investigated. Hot water extractions of bleached and unbleached kraft pulps were performed in a flow-through system to remove and recover the xylan. After the extraction, the pulps were oxidized with 2,2,6,6-tetramethylpiperidine-1-oxyl radical (TEMPO) and fibrillated in a high-pressure microfluidizer. Compared to CNF from bleached kraft pulp, the CNF dispersions obtained from water-extracted pulps were less viscous and generally contained a higher amount of microfiber fragments, although smaller in size. In all cases, however, smooth and highly transparent films were produced from the CNF dispersions after the addition of sorbitol as plasticizer. The CNF films made from water-extracted pulps showed a lower tensile strength and ductility, probably due to their lower xylan content, but the stiffness was only reduced by the presence of lignin. Interestingly, the CNF films from water-extracted bleached pulps were less hydrophilic, and their water vapour permeability was reduced up to 25%. Therefore, hot water extraction of bleached birch kraft pulp could be used to produce CNF films with improved barrier properties for food packaging, while obtaining a high-purity xylan stream for other high-value applications.

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Analysis of Hydrodynamic Characteristics in the Process of Autonomous Underwater Vehicle Docking

Volume 7: Ocean Engineering ◽

10.1115/omae2015-42323 ◽

2015 ◽

Cited By ~ 1

Author(s):

Xiaoxu Du ◽

Huan Wang

Keyword(s):

Drag Coefficient ◽

Autonomous Underwater Vehicle ◽

Simple Algorithm ◽

Underwater Vehicle ◽

Navier Stokes ◽

Hydrodynamic Characteristics ◽

Successful Operation ◽

Underwater Docking ◽

Computational Fluid Dynamics Cfd ◽

Volume Method

The successful operation of an Autonomous Underwater Vehicle (AUV) requires the capability to return to a dock. A number of underwater docking technologies have been proposed and tested in the past. The docking allows the AUV to recharge its batteries, download data and upload new instructions, which is helpful to improve the working time and efficiency. During the underwater docking process, unsteady hydrodynamic interference occurs between the docking device and an AUV. To ensure a successful docking, it is very important that the underwater docking hydrodynamics of AUV is understood. In this paper, numerical simulations based on the computational fluid dynamics (CFD) solutions were carried out for a 1.85m long AUV with maximum 0.2 m in diameter during the docking process. The two-dimensional AUV model without fin and rudder was used in the simulation. The mathematical model based on the Reynolds-averaged Navier-Stokes (RANS) equations was established. The finite volume method (FVM) and the dynamic structured mesh technique were used. SIMPLE algorithm and the k-ε turbulence model in the Descartes coordinates were also adopted. The hydrodynamics characteristics of different docking states were analyzed, such as the different docking velocity, the docking device including baffle or not. The drag coefficients of AUV in the process of docking were computed for various docking conditions, i.e., the AUV moving into the docking in the speed of 1m/s, 2m/s, 5m/s. The results indicate that the drag coefficient increases slowly in the process of AUV getting close to the docking device. When the AUV moves into the docking device, the drag coefficient increases rapidly. Then the drag coefficient decreases rapidly. The drag coefficient decreases with the increase of velocity when AUV enters the docking device. It was also found that the drag coefficient can be effectively reduced by dislodging the baffle of docking device.

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