Molecular Simulation Analysis of Polyurethane Molecular Structure under External Electric Field

Polyurethane (PU) materials are extensively utilized in power equipment. This paper introduces a comprehensive evaluation method that combines electromagnetics and computational chemistry based on the Density Functional Theory (DFT) to elucidate the impact of external electric fields on the molecular structure of PU during electrical contact. The study focuses on the microstructural and molecular energy changes in the hard (HS) and soft (SS) segments of PU under the influence of an electric field of uniform intensity. Findings indicate that the total energy of HS molecules decreases markedly as the electric field intensity increases, accompanied by a significant rise in both the dipole moment and polarizability. Conversely, the total energy and polarizability of the SS molecules decrease, while the dipole moment experiences a slight increase. Under the influence of a strong electric field, HS molecules tend to stretch towards the extremities of the main chain, leading to structural instability and the cleavage of hydroxyl O-H bonds. Meanwhile, the carbon chain of the SS molecules twists towards the center under the electric field, with no chemical bond rupture observed. At an electric field intensity of 8.227 V/nm, the HOMO-LUMO gap of the HS molecule narrows sharply, signifying a rapid decline in the molecular structure stability, corroborated by infrared spectroscopy analysis. These findings offer theoretical insights and guidance for the modification of PU materials in power equipment applications.

Molecular dynamics-based study of the modification mechanism of asphalt by graphene oxide

CONTEXT

Graphene oxide(GO) has been widely used in asphalt modification due to its excellent properties. To reveal the interaction effect between GO and asphalt materials, the microscopic behavior and molecular structure changes of asphalt and GO/asphalt were investigated by molecular dynamics (MD) simulations. Mean square displacement (MSD) results showed that GO significantly inhibited the diffusion of molecules of asphalt components. Radial distribution function (RDF) results that GO destroys the original sol-type structure of asphalt. Simultaneously, GO adsorbed resins at low-temperature, adsorbed asphaltenes at high-temperature, and dispersed as a dispersed phase in the light components. The concentration of the dispersed phase in the asphalt colloidal structure was increased and the mutual attraction was enhanced. This improves the deformation resistance at high temperature, but weakens the ductility at low temperatures.

METHODS

To investigate the mechanism of action of GO-modified asphalt, the asphalt model and the GO/asphalt composite system model were constructed using the Amorphous Cell module in Materials Studio 2020 software. Subsequently, molecular dynamics simulations of the GO/asphalt composite system were performed using the Forcite module, while the interactions between atoms and molecules were described using the COMPASS II force field.

Exploring thermodynamic and structural properties of carbon nanotube/thermoplastic polyurethane nanocomposites from atomistic molecular dynamics simulations

Carbon nanotubes (CNTs) and thermoplastic polyurethane (TPU) nanocomposites have emerged as promising materials for various applications in the field of nanotechnology. An understanding of the thermodynamic and structural properties is of fundamental significance in designing and fabricating CNT/TPU nanocomposites with desired properties. To this end, this work has employed atomistic molecular dynamics (MD) simulations to study the thermal properties and interfacial characteristics of TPU composites filled with pristine or functionalized single-walled carbon nanotubes (SWNTs). Simulations reveal that the introduction of SWNTs suppresses TPU chain dynamics and favors the hydrogen bond formation induced by the wrapping of TPU chains around SWNTs, leading to an increase of glass transition temperature (T_g) and a reduction of volumetric coefficient of thermal expansion (CTE) in the rubbery state. Compared to pristine and hydrogenated SWNTs, SWNTs featuring polar groups, such as carboxyl (-COOH), oxhydryl (-OH) and amine (-NH₂) groups, show improved affinity for TPU molecules, suppressing polymer mobility. Analysis of SWNT/TPU binding energy and solubility parameter suggests that electrostatic interactions are responsible for such a functionalized SWNT/TPU interface enhancement. Furthermore, the amine groups exhibit the highest potential for forming hydrogen bonds with the urethane carbonyl (-C[double bond, length as m-dash]O) of TPU chains, resulting in lowest polymer mobility and highest T_g. In general, this research work could provide some guidance for material design of polymer nanocomposites and future simulations relevant to TPUs.

Preparation Scheme Optimization of Thermosetting Polyurethane Modified Asphalt

To solve the issue of the poor temperature stability of conventional modified asphalt, polyurethane (PU) was used as a modifier with its corresponding curing agent (CA) to prepare thermosetting PU asphalt. First, the modifying effects of the different types of PU modifiers were evaluated, and the optimal PU modifier was then selected. Second, a three-factor and three-level L9 (3³) orthogonal experiment table was designed based on the preparation technology, PU dosage, and CA dosage to prepare the thermosetting PU asphalt and asphalt mixture. Further, the effect of PU dosage, CA dosage, and preparation technology on the 3d, 5d, and 7d splitting tensile strength, freeze-thaw splitting strength, and tensile strength ratio (TSR) of the PU asphalt mixture was analyzed, and a PU-modified asphalt preparation plan was recommended. Finally, a tension test was conducted on the PU-modified asphalt and a split tensile test was performed on the PU asphalt mixture to analyze their mechanical properties. The results show that the content of PU has a significant effect on the splitting tensile strength of PU asphalt mixtures. When the content of the PU modifier is 56.64% and the content of CA is 3.58%, the performance of the PU-modified asphalt and mixture is better when prepared by the prefabricated method. The PU-modified asphalt and mixture have high strength and plastic deformation ability. The modified asphalt mixture has excellent tensile performance, low-temperature performance, and water stability, which meets the requirements of epoxy asphalt and the mixture standards.

Bio-based epoxy functionalized MQ silicone resins: from synthesis to toughened epoxy composites with good mechanical properties, thermal resistance and transparency

A series bio-based eugenol silicone resins are synthesized, and EG-1.2MQ shows its good promise as a new green multifunctional additive to well balance the toughness, mechanical properties, transparency, and other properties.