: A novel hybrid organic/inorganic tri-block copolymer of polystyrene-butadiene-polystyrene (SBS) containing grafted polyhedral oligomeric silsesquioxane (POSS) molecules was synthesized by a hydrosilation method. The POSS molecules were designed to contain a single silane functional group, which was used to graft onto the dangling 1,2 butadienes in the polybutadiene soft block. Unlike typical free radical copolymerizations commonly used for many other POSS incorporations investigated, this synthesis method allows us to make a series of polymers with varying amounts of POSS without any change to the overall degree of polymerization or structure of the main SBS backbone. This gives us a unique opportunity to study the POSS behavior in the matrix and know that all differences are solely due to the POSS grafted to the soft continuous butadiene phase. X-ray diffraction revealed that the grafted POSS are very well dispersed in the matrix of the hybrid polymer, which is compared to the strong phase segregation observed in a POSS physical blend. Small-angle X-ray scattering indicates that although the cylindrical morphology attributed to the styrene component was not altered by the presence of POSS, but attachment of POSS to the continuous phase (polybutadiene block) causes the packing of discrete phase (polystyrene blocks) to lack long-range features. Results of dynamic mechanical analysis showed that the POSS has sterically hindered the motion of the polybutadiene blocks. More interestingly, the presence of POSS in the soft segments also resulted in a tapered tan peak associated with the glass transition of polystyrene and a higher tensile strength when deformed at temperature near Tg of polystyrene without affecting the elongational behavior of SBS at temperatures above Tg of polybutadiene.

Styrene-butadiene-styrene Tri-block Copolymers Modified wit Polyhedral Oligomeric Silsesquioxanes

Research progress on compounding agent and mechanical test method of fluororubber

This article focuses on the methods used to create self-healing silicone composites. It has been shown how incorporation of polyhedral oligomeric silsesquioxanes (POSS) molecules with acid and basic groups into silicone rubber affects the barrier properties, mechanical properties in room temperature or the influences on relaxation rates of the methylvinylsilicone rubber vulcanizates. Moreover, the presence of silsesquioxanes, their content and the way of composites preparation affect the amount of ionic bonds, as indicated by measurements of equilibrium swelling in toluene. The self-healing effect of preparing samples is best visualized by SEM images of samples after destruction and conditioning. Composites presented in this work based on the methylvinylsilicone rubber with fumed silica as the fillers were manufactured and studied. To obtain self-healing effect, various silsesquioxanes were used, such as amic acid-isobutyl POSS (AAIb-POSS), aminopropylisobutyl-POSS (APIb-POSS) and aminoethylaminopropylisobutyl-POSS (AEAPIb-POSS). Every tested sample demonstrated the ability to the self-treatment. The most significant effect was observed for system containing amic acid-isobutyl POSS/aminopropylisobutyl-POSS.

/pdf/poss-as-promoters-of-self-healing-process-in-silicone-3lpa6fz8mq.pdf

POSS as promoters of self-healing process in silicone composites

Liquid‐metal embedded elastomers (LMEEs) have been demonstrated to show a variety of excellent properties, including high toughness, dielectric constant, and thermal conductivity, with applications across soft electronics and robotics. However, within this scope of use cases, operation in extreme environments – such as high‐temperature conditions – may lead to material degradation. While prior works highlight the functionality of LMEEs, there is limited insight on the thermal stability of these soft materials and how the effects of liquid metal (LM) inclusions depend on temperature. Here, the effects on thermal stability, including mechanical and electrical properties, of LMEEs are introduced. Effects are characterized for both fluoroelastomer and other elastomer‐based composites at temperature exposures up to 325 °C, where it is shown that embedding LM can offer improvements in thermo‐mechanical stability. Compared to elastomer like silicone rubber that has been previously used for LMEEs, a fluoroelastomer matrix offers a higher dielectric constant and significant improvement in thermo‐mechanical stability without sacrificing room temperature properties, such as thermal conductivity and modulus. Fluoroelastomer‐LM composites offer a promising soft, multi‐functional material for high‐temperature applications, which is demonstrated here with a printed, soft heat sink and an endoscopic sensor capable of wireless sensing of high temperatures.

Thermo‐Mechanically Stable, Liquid Metal Embedded Soft Materials for High‐Temperature Applications

Cette etude porte sur l'influence des nano-charges conductrices de noir de carbone sur le comportement mecanique de materiaux composites, dans le but d'integrer la fonction du blindage electromagnetique. Ces travaux ont traite, dans un premier temps, du probleme pratique de la realisation d'un tel composite et notamment, de la diffusion de la resine chargee lors de la mise en oeuvre par des procedes classiques par voie liquide (Infusion et RTM-Eco). La Premiere phase du travail est realise sur la resine chargee seule, dans le but de comprendre l'impact des nano-charges conductrices sur le comportement mecanique d'une resine thermodurcissable de type vinylester avant l'injection de cette resine dans la preforme. Finalement une partie est consacree a la caracterisation de composite a resine nanochargee en termes d'efficacite de blindage electromagnetique dans une gamme de frequence allant de 10 MHz a 6 GHz.

Influence des nano-charges de noir de carbone sur le comportement mécanique de matériaux composites : application au blindage électromagnétique

The present study reports on the use of three types of polyhedral oligomeric silsesquioxanes (POSS) nanoparticles with various organic substituents as fillers in a fluoroelastomer (FKM). A series of/POSS elastomer composite thin films is prepared. Microstructural SEM/TEM (scanning electron microscopy/transmission electron microscopy) imaging reveals a dispersion state allowing the presence of micron-sized domains. The influence of POSS content is studied in order to optimize thermal stability and mechanical properties of the composite thin films. Both POSS-A (with an acryloyl functional group and seven isobutyl substituents) and POSS-P (with eight phenyl substituents) lead to higher thermal stability and modulus of the composites, with respect to the unfilled FKM terpolymer matrix. covalent grafting of POSS-A onto the FKM network is found to play a critical role. Enhanced storage modulus in the rubbery plateau region (+210% at 200 °C for 20 phr) suggests that POSS-A is particularly suitable for high temperature applications.

https://www.mdpi.com/1996-1944/11/8/1358/pdf

POSS Nanofiller-Induced Enhancement of the Thermomechanical Properties in a Fluoroelastomer Terpolymer.

Degradation mechanism of FKM during thermo-oxidative aging from mechanical and network structure correlations

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POSS Nanofiller-Induced Enhancement of the Thermomechanical Properties in a Fluoroelastomer Terpolymer.

Degradation mechanism of FKM during thermo-oxidative aging from mechanical and network structure correlations