Macromolecular Theory and Simulations最新文献

In the investigation of condensed phase reactions, obtaining kinetic parameters is vital for understanding reaction behavior and optimizing conditions. To achieve this, differential methods have been devised, yet due to the instability of calculating instantaneous reaction rates through numerical differentiation, they have been less commonly utilized. In this study, the extraction of smooth reaction rate curves from highly noisy experimental data via the Chebyshev series expansion (CSE) approach is explained. Furthermore, a novel combined kinetic analysis is developed to determine reaction kinetic parameters utilizing the Chebyshev series expansion. By employing the new method, kinetic parameters can be accurately deduced by performing multiple linear regression analysis on kinetic data generated from reactions. The CSE has consistently exhibited exceptional accuracy in approximating the conversion function. The primary advantage of the new method lies in its ability to accurately determine unique values for kinetic parameters, including activation energy, pre-exponential factor, and conversion function, without prior knowledge of the reaction mechanism. The new method has been validated using kinetic data from a simulated reaction and poly(methyl methacrylate) thermal degradation. To facilitate readers in applying the new methods to various kinetic data, the GNU Octave/MATLAB codes have been made publicly available.

A technique for separating molten polymer blends is investigated computationally. The device includes a rotating cylinder, separating the mixture components with different densities by the centrifugal force. Molten LDPE (Low-Density Poly(Ethylene)) and PET (Poly(Ethylene) Terephthalate) mixtures are investigated. The computational modeling is intended to evaluate the feasibility of such a technique at the time and length scales studied. A dispersed mixture model accounts for the immiscibility of the mixture components. The CFD simulations provide the field distributions of the flow field variables and of the mixture component fractions. The outlet composition and separation efficiency in the steady-state process, and the different process parameter influences on the process result, are studied. The polymer system at hand represents blends of postconsumer plastics. The study can therefore contribute to the development of a novel method for plastic waste recycling. With continuous feed and extraction of the polymer streams, the process can be automated.

This study presents a novel quantitative approach for analyzing the phase behavior and miscibility of polycaprolactone (PCL) and polydioxanone (PDO) blends through rheological analysis. A polymer miscibility index (PMI) is introduced, derived from the Cole–Cole plot analysis in a bid to understand the underlying physics of polymer blends. The PMI defined using complex viscosities enables quantitative evaluation of blend miscibility under various temperature and composition conditions. A phase diagram is constructed using the methodology, describing the upper critical solution temperature behavior. PCL/PDO blends exhibit enhanced phase stability with increasing PDO content, suggesting that PDO has a dominant role in determining blend miscibility. This quantitative approach provides valuable insight for optimizing the processing conditions and composition ratios of PCL/PDO blend.

This study examines the limitations of classical analytical approximations of Fick's second law of diffusion and proposes a computational approach to determine the diffusion coefficient (D) using the entire diffusion process data. Traditional approximations rely on short-time diffusion data, potentially leading to misinterpretations. The computational method, validated with experimental data on liquid water diffusion in poly(lactic acid) and oxygen diffusion in poly(ethylene terephthalate), demonstrates higher accuracy and broader applicability. This approach challenges the common assumption that deviations from analytical approximations imply non-Fickian behavior, offering a more reliable method for diffusion analysis.

Coating techniques are broadly used in the production of sticky tapes, plastic films, books, wallpapers and magazines, adhesive tapes as well as the textiles and metals preservation, packaging, materials protection and X-ray films. The modeling of roll-over web coating technique is investigated to report the magneto-hydrodynamic (MHD) viscous hybrid nanofluid impact on the final coating thickness. In the coating industry, the application of nanomaterial over the sheet/substrate has better non-Newtonian like rheological features as opposed to the ordinary fluid. The dimensionless governing equations are reduced using lubrication approximation theory (LAT) and the exact solutions for velocity and pressure gradient are acquired. To find the flow rate, coating thickness and other mechanical quantities, numerical technique is utilized. The graphs and tables briefly study the impacts of hybrid nanomaterial volume fraction and Hartmann number on the flow and engineering quantities in detail. Hybrid nanomaterial volume fraction under MHD results in higher shear stress and pressure profile, which triggers decline in coating thickness, which may help in achieving efficient coating process and protecting the substrate life.

Blade coating is a process in which a fluid is applied to a surface using a fixed blade, offering economic benefits over other coating techniques. It is commonly employed in paper production, information preservation, and the manufacturing of photographic films and magnetic storage devices. This article explores the non-isothermal blade coating process using the Bingham plastic fluid model with non-linear slip effects. The 2D incompressible flow in the blade coating process is modeled with conjunction of the continuity, momentum, and energy equations. The modeled flow equations are converted into the dimensionless using dimensionless variables and parameters. The simplified non-linear differential equations are solved numerically using boundary value problem fourth order collocation (bvp4c) method. This work explores how changes in physical parameters affect flow characteristics and mechanical properties of the blade coating process are investigated with the help of various graphs and tables. It is observed that the pressure and velocity of the molten polymer increase with increasing the values of the Bingham plastic parameter. It is also observed, when the value of the slip parameter is ($��\gamma �=�0.8�)�,�$ the coating thickness increased by 41.6279% (for plane coater) and 53.4030% (for exponential coater), and blade load force decreased by 14.2272% (for plane coater) and 15.0107% (for exponential coater) form the Newtonian values.

This review discusses methods for calculating the equilibrium interfacial tension in strongly immiscible polymer blends compatibilized with copolymers. The discussion is focused on typical polymer blends with fine phase structures; in these polymer blends, the volume of the interfacial layer is generally not negligible with respect to the volume of the bulk phases. The main models and calculation procedures that are predominantly used are compared, and their practicalities are discussed. Neither the expressions derived using the dry brush approximation nor those derived using the wet brush approximation are applicable to blends compatibilized with copolymers that have block lengths comparable to those of the compatibilized homopolymers. The amount of a copolymer in the interfacial layer of a polymer blend is generally not negligible with respect to its amount in the bulk phases. Therefore, approximations that are successfully used for the calculation of the interfacial tension measured by common methods cannot be applied to calculation of the interfacial tension in the polymer blends.

The behavior of (athermal) mobile doubly tethered polymers (ring-like in 3D) is investigated, on a 2D substrate using the bond fluctuation model. The end-monomers can move laterally within a constrained distance range. Conformational properties of loop polymers are analyzed and specifically the ordering of the 2D system of end-monomers. For this, the director is considered between the end-monomers for local ordering. As tethering density increases, a transition from mushroom-like conformations to nearly upright structures is observed, as is the case for linear grafted polymers. The effects of loop repulsion are explored, i.e., entropic repulsion, and tethering density on the order parameter and orientational correlations of the directors in 2D. Despite the lack of a global phase transition, local orientational order emerges in 2D due to loop interactions in 3D.