Adaptive Backstepping Control of Active Magnetic Bearings with Slice Rotor

Viscoelastic materials are commonly utilized in seismic vibration suppression of building structures. Supramolecular modification can extend the effective damping temperature range and improve the damping performance of viscoelastic materials. In present work, the mechanical behaviors of the nitrile rubber viscoelastic material are investigated by dynamic thermomechanical analyzer (DMA) with different strain amplitudes, excitation frequencies and environmental temperatures. The supramolecular interaction and molecular structures modified fractional Kelvin (SMF Kelvin) model taking into account the temperature and frequency impacts is proposed and verified with the DMA test results of the nitrile rubber viscoelastic material. The test results of the viscoelastic damper with different temperatures are employed to further prove the effectiveness of the new proposed SMF Kelvin model.

Section: Introductionmentioning

confidence: 99%

Study on viscoelastic materials at micro scale pondering supramolecular interaction impacts with DMA tests and fractional derivative modeling

Guo

et al. 2023

“…FRC exhibit enhanced thermal, 12,13 mechanical, 14,15 and damping properties 16–20 compared to the polymer matrix alone. These composites offer improved thermal conductivity, thermal expansion, and heat resistance, making them excellent thermal insulators.…”

Section: Introductionmentioning

confidence: 99%

A pre‐mold study of alkaline‐silane treated EFB‐PP composites based on thermal and rheological analysis

Abdullah

Rahman

Hassan

2023

Rheological and thermal properties are important parameters to understand the role of the numerous variables involved in manufacturing and to achieve a high‐quality final product. The composites were prepared by compounding polypropylene (PP) with treated (alkaline and silane) oil‐palm empty fruit bunch (EFB) fiber using a twin screw extruder. Generally, regardless of fiber loading, the thermal stability of EFBPP composites was increased after using alkaline and silane‐treated EFB fibers as reinforcement. DSC analysis shows that there is a change in the melting temperature (Tm) and the degree of crystallinity (Xc) values of the EFB composites. The melt flow rate (MFR) of the composites decreased while viscosity increased with an increase in fiber loading. Rheological analysis reveals the composites to have a viscoelastic solid behavior where storage modulus (G') is greater than loss modulus (G“). The composites exhibit predominantly viscous behaviour (G" > G') at lower frequencies, whereas at higher frequencies the composites exhibit elastic behavior (G' > G”). The decrement of complex viscosity (η*) with an increasing angular frequency (ω) shows the materials exhibit shear thinning behavior. The composites also show the ability for regeneration when analyzed using time‐dependent behavior.

“…Nonpolar rubber, an important material, has attracted considerable attention due to its abundant content. However, the intrinsic low‐glass transition temperature ( T g ) and surface energy still result in relatively weak intermolecular force with polar rubber or fillers, further restricting their application in various fields 9 …”

Section: Introductionmentioning

confidence: 99%

“…Justynska 17 et al have studied the parameters and modular synthesized functional polymers by radical addition of ω‐functional thiols onto 1,2‐PB‐based homo‐polymers and block co‐polymers functional polymer was realized. Yan et 18 grafted 3 MPA to the SBS by thermo‐induced thiol clicking to prepare composites with potentially viable shape memory behaviors, and then constructed networks with ZnO, resulting in significant improvements in the mechanical properties of the SBSgCOOH/ZnO 9 . Therefore, it is feasible to introduce polar groups into nonpolar rubber with a high molecular weight and to achieve excellent damping mechanical and adhesion properties through thiol−ene click reaction 19…”

Section: Introductionmentioning

confidence: 99%

High‐damping ultralow−gel nonpolar elastomeric polymer through thiol−ene photo−click chemistry reaction

Zhang

Gao

Liu

et al. 2023

With the increasing demand for high-performance damping rubber material in various fields, improving the damping performance of existing nonpolar rubber has garnered tremendous scientific and industrial interest. However, it remains a long-standing challenge to improve the damping properties of nonpolar rubber materials due to their low intrinsic glass transition temperature (T g ) and incompatible surface energy with high-damping polar polymers or fillers. To solve this conundrum, ultra-low gel multifunctional carboxyfunctional high vinyl polybutadiene HVBR (HVBR/COOH-x%) was prepared by grafting 3-mercaptopropionic acid (3PMA) onto HVBR via thiolÀene photo-Àclick. The effects of reaction parameters including molecular weight, 1,2-vinyl content, photoinitiators, reaction time, thiol and photoinitiator dosage on gel content and carboxyl grafting ratio were investigated. The HVBR/COOH-x% demonstrate a controllable grafting ratio range from 2% to 73%. Furthermore, the increased T g and intermolecular force resulted in excellent performance, including high-glass transition temperature of 26.3 C, tensile strength of 15.52 MPa, and elongation at break of 396.16%. Particularly with a wide range of effective damping temperatures above 46.6 C. Meanwhile, COOH endowed the HVBR with better self-viscosity, but also equipped it with stronger mutual viscosity. Therefore, this experiment proposes a feasible path to high damping and high adhesion in nonpolar rubber materials.