Macromolecular Symposia最新文献

Elastomeric elements are used for vibration reduction and noise control in many industries. New part geometries are constantly designed and tailored to fulfil the specific mechanical requirements of each application, with much of the design performed virtually before any physical prototyping. It is advantageous for manufacturers of technical rubber articles to have the tools to accurately and efficiently calculate the costs of production of different geometries with different rubber compounds. This article discusses, through an example railway rubber bushing, how injection molding simulation software can help the quoting process and quickly respond to market demands, even with limited information. The main advantage of the simulation is the prediction of curing time with complex geometries at an early stage. High temperatures are needed to initiate the cross-linking reaction of the rubber compound, which leads to the final good mechanical properties of the part. This process has a major impact on cost, as it requires a lot of energy and time in the injection press. With the help of software, a good estimation with good accuracy can be calculated by an experienced user in a short time. In this article, a step-by-step description is outlined for obtaining a curing time estimation using SIGMASOFT Virtual Molding simulation software. How to consider the part and mold geometry, process parameters, rubber compound, simulation setup, and results evaluation is discussed. With a curing time of 20 min in the mold, the curing degree reaches over 90% throughout the part, considering residual heat after demolding in ambient conditions. The difference in curing inside and through the cross-section of the part can be visualized and investigated. The software is supplementing traditional curing time estimations with an insider view, especially for complex part geometries.

Silica glass samples co-doped with Pr³⁺:Yb³⁺ as well as Tm³⁺:Yb³⁺ were prepared using sol–gel technique and the energy transfer among the rare earth dopants is studied. Judd–Ofelt (JO) parameters Ω₂, Ω₄, and Ω₆ are calculated from the absorption spectra. Relatively large values of Ω₂ indicates that the rare earth ions occupy low symmetry sites in the glasses. These parameters are used to estimate branching ratio and radiative lifetime. The measured lifetimes are significantly lower than the calculated lifetimes. Photoluminescence was found to be significantly enhanced with aluminum co-doping for both Pr³⁺ and Tm³⁺ emissions. This enhancement is attributed to the reduction in cross-relaxation. Infrared to visible up-conversion is also observed under 980 nm excitation as a result of energy transfer from Yb³⁺ to Tm³⁺ and Pr³⁺ ions.

The effects of barium titanate (BaTiO₃) filler on the rheology, mechanical, and piezoelectric properties of natural rubber (NR) based industrial rubber mixture were investigated. The results revealed lower time to reach 90% curing (tc90) and lower tensile strength and elongation at break values for BaTiO₃-filled rubber composites compared to the pure rubber mixture. The piezoelectric charge constant (d₃₃) and the generated voltage of BaTiO₃-filled rubber composites increased up to 3 pC/N and 120 mV, respectively, for a total filler content of 40 vol.% with the increase of the filler content.

This article reports the successful synthesis of carbon nanotubes in amorphous form (a-CNTs) through a low-temperature solid state reaction. The as-synthesized a-CNTs were functionalized uniformly by flake like MoS₂ nanostructure. XRD study confirms the amorphousness of the pure a-CNTs whereas functionalized sample shows the proper phase formation of MoS₂. Electron microscopic images confirm the tubular morphology of the pure a-CNTs as well as uniform functionalization of the same by MoS₂ flakes. Elemental analysis done with EDX study, denied showing presence of any impurities confirming again the proper phase formation. FTIR study enlightens about the presence of different bonding in the sample. When field emission characteristics of both the samples were taken, it was seen that the functionalized sample shows much better results compared to the pure a-CNT in terms of enhancement factor, turn on field, as well as effective work function. The turn on field showed a decrease from 8.99 V/µm to 4.86 V/µm whereas a three-time increment in the enhancement factor from 930 to 2742 was obtained in case of functionalized sample. The possible reasons behind the enhancement are the concentration of field lines at the sharp edges of MoS₂ flakes, lesser work function of the foreign element, as well greater electron transport through the favorable band bending.

Epichlorohydrin (ECH)-based elastomers represent a significant class of materials, offering dynamic properties similar to natural rubber but with enhanced heat and chemical resistance. They also offer improved low-temperature flexibility due to the presence of pendant chloromethyl groups on the main chains with etheric oxygens. This study investigates the effect of molecular architectures on the damping properties of elastomers derived from ECH terpolymers, specifically poly(epichlorohydrin-co-ethylene oxide-co-allyl glycidyl ether) (GECO) at various temperatures. Cylindrical samples were subjected to cyclic compression tests at three different temperatures. The results demonstrate that the molecular architecture of GECO polymers significantly influences the damping properties of the resulting elastomers, with varying effects observed at different temperatures.

In this paper, comparative performances of the supercapacitor based on different redox additives (vanadyl sulfate [VOSO₄] and potassium iodide [KI]) incorporated gel polymer electrolytes (redox additive gel polymer electrolytes [RGPEs]) are reported. RGPEs were prepared by entrapping liquid electrolyte solution NaClO₄/ethylene carbonate (EC):propylene carbonate (PC) in host polymer PVdF-HFP along with redox additives via conventional solution casting techniques. It is observed that the ionic conductivity of pristine gel polymer electrolyte (GPE) is dependent on the content of redox additives (VOSO₄ and KI) and temperatures. It is improved by adding redox additive 0.1 wt% VOSO₄ (RGPE-1) and 0.3 wt% KI (RGPE-2) with corresponding ionic conductivity values to ∼3.25 × 10⁻³ and ∼4.02 × 10⁻³ S cm⁻¹, respectively. Further, two quasi-solid-state supercapacitor cells are fabricated using the optimized GPEs RGPE-1 and RGPE-2 with honeycomb-based activated carbon (HCAC) electrodes. The comparative performances of the supercapacitor cells are evaluated and analyzed in terms of different electrochemical characterization techniques such as impedance, electrochemical stability window (ESW), cyclic voltammetry (CV), linear sweep voltammetry (LSV), and galvanostatic charge discharge (GCD) characteristics.