Formation of silicone elastomer networks films with gradients in modulus

Crowe-Willoughby, Julie A.; Weiger, Katherine L.; Özçam, A. Evren; Genzer, Jan

doi:10.1016/j.polymer.2009.11.070

Cited by 32 publications

(32 citation statements)

References 21 publications

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“…The neat PDMS solution prepared by the mixing polymer base and the hardener has adhesion property, which is reduced by crosslinking in curing step leading to disappearance of sticky characteristic of PDMS upon complete crosslinking. By increasing the curing temperature, PDMS crosslinking rate is facilitated [36]. Our results indicate that the required time for adhesion disappearance at 25, 100, 150, and 200°C were 5, 3, 2, and 1 day, respectively.…”

Section: Resultsmentioning

confidence: 88%

Effect of coating method on gas separation by PDMS/PES membrane

Madaeni

Badieh

Vatanpour

2013

Polymer Engineering & Sci

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In this study, polydimethylsiloxane (PDMS)‐coated polyethersulfone (PES) composite membrane was prepared for gas separation. “Film casting” and “dip‐coating” techniques were used for producing selective PDMS layer on the surface of the PES support. The effects of coating technique and conditions including coating solution concentration and curing temperature on permselectivity of CO2, CH4, and N2 were investigated. The prepared PES support did not provide any selectivity to the gases. When the concentration of PDMS coating solution was increased, initially permeability of CO2 was rapidly dropped and then gradually reached to an almost constant value. The optimum concentration of coating solution was 5 wt%. Curing temperature showed no pronounced effect on the CO2 permeability and selectivity. In “film casting” method, double coating showed superior permeability and selectivity. However, triple “dip‐coating” was promising. The selectivity of composite membrane prepared by “dip‐coating” was higher than “film casting” method. CO2/N2 and CO2/CH4 selectivity of five sequential dip‐coated composite membranes was 45.5 and 9.3, respectively. POLYM. ENG. SCI., 2013. © 2013 Society of Plastics Engineers

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Section: Resultsmentioning

confidence: 88%

Effect of coating method on gas separation by PDMS/PES membrane

Madaeni

Badieh

Vatanpour

2013

Polymer Engineering & Sci

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“…In this contribution, PDMS28 was used to optimize the setup as well as various processing parameters. To establish correlations between gradient composition, position, time, and also optical and mechanical properties, a commercially available PDMS system is of great advantage.…”

Section: Resultsmentioning

confidence: 99%

Cooperative Supramolecular Polymerization: Comparison of Different Models Applied on the Self‐Assembly of Bis(merocyanine) Dyes

Fernández

Stolte

Stepanenko

et al. 2012

Chemistry A European J

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Three new molecular building blocks 1 a-c for supramolecular polymerization are described that feature two dipolar merocyanine dyes tethered by p-xylylene spacers. Concentration- and temperature-dependent UV/Vis spectroscopy in chloroform combined with dynamic light scattering, capillary viscosimetry and atomic force microscopy investigations were applied to elucidate the mechanistic features of the self-assembly of these strongly dipolar dyes. Our detailed studies reveal that the self-assembly is very pronounced for bis(merocyanines) 1 a,b bearing linear alkyl chains, but completely absent for bis(merocyanine) 1 c bearing sterically more bulky ethylhexyl substituents. Both temperature- and concentration-dependent UV/Vis data provide unambiguous evidence for a cooperative self-assembly process for bis(merocyanines) 1 a,b, which was analyzed in detail by the Meijer-Schenning-Van-der-Schoot model (applicable to temperature-dependent data) and by the Goldstein-Stryer model (applicable to concentration-dependent data). By combining both methods all parameters of interest to understand the self-assembly process could be derived, including in particular the nucleus size (8-10 monomeric units), the cooperativity factor (ca. 0.006), and the nucleation and elongation constants of about 10(3) and 10(6) M(-1) in chloroform at room temperature, respectively.

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“…TiO 2 -silicone composites have by far been the most commonly investigated elastomer system due to the availability of nanosized TiO 2 particles with various surface functionalizations. More complex approaches exist such as the covalent grafting of dipoles [11][12][13] and the creation of heterogeneous elastomers with hard and soft domains from controlled network formation [14][15][16][17]. Incorporating rigid fillers, such as titanium dioxide, into the cross-linked PDMS matrix increases the dielectric permittivity of the resulting composite elastomer.…”

Section: Introductionmentioning

confidence: 99%

The influence of static pre-stretching on the mechanical ageing of filled silicone rubbers for dielectric elastomer applications

Zakaria

Kofod³

et al. 2015

Materials Today Communications

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Dielectric elastomer (DE) pre-stretching is a key aspect of attaining better actuation performance, as it helps prevent electromechanical instability (EMI) and usually lowers the Young's modulus, thus leading to easier deformation. The pre-stretched DE is not only susceptible to a high risk of tearing and the formation of mechanical defects, but films with sustained and substantial strain may also experience mechanical degradation. In this study a long-term mechanical reliability study of DE is performed. Young's moduli, dielectric breakdown strengths and dielectric permittivities of commercial silica-reinforced silicone elastomers, with and without an additional 35% (35 phr) of titanium dioxide (TiO 2 ), were investigated after being subjected to pre-stretching for various timespans at pre-stretches to strains of 60 and 120%, respectively. The study shows that mechanical stability when prestretching is difficult to achieve with highly filled elastomers. However, despite the negative outlook for metal oxide-filled silicone elastomers, the study paves the way for reliable dielectric elastomers by indicating that simply post-curing silicone elastomers before use may increase reliability. 1 INTRODUCTIONThe reliability of dielectric elastomer (DE) transducers depends on the types of material used, as well as fabrication techniques and design and transducer operating conditions (such as maximum stretching, applied frequency and amplitude of the applied voltage). The acrylic double-adhesive VHB 4910, produced by 3M, is one of the best-performing elastomers with respect to actuation strain (s) at a given applied field, and it chiefly outperforms silicone-based elastomers over short time scales. Silicone elastomers, however, possess a faster actuation response as well as reliability over time, since performance remains more or less unaltered up to about 10 million cycles when pre-stretching is avoided.[1] Pre-stretching is well-known to be a prerequisite for the actuation of acrylic-based elastomers, since it simultaneously reduces thickness, decreases the Young's modulus and suppresses electro-mechanical instability (EMI). Pre-stretching has also been shown to cause the alignment of elastomer chains in the plane of stretching.[5] This alignment, which is perpendicular to the direction of the electric field, leads to an increase in breakdown strength, because charge carrier movement is impeded.[6] For acrylics, pre-stretching is also favourable due to strain-softening, whereas for silicone elastomers the elastomer usually does not show the same tendency and in many cases strain-hardening behaviour actually sets in. However, pre-stretching remains very favourable for silicone elastomers, as largely improved actuation strains can be obtained through the avoidance of EMI.The most common failure modes of DE transducers are pull-in instability, dielectrical breakdown and material strength failure [7,8]. Electromechanical pull-in instability, also known as electromechanical instability (EMI), was identified by Stark a...

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Formation of silicone elastomer networks films with gradients in modulus

Cited by 32 publications

References 21 publications

Effect of coating method on gas separation by PDMS/PES membrane

Effect of coating method on gas separation by PDMS/PES membrane

Cooperative Supramolecular Polymerization: Comparison of Different Models Applied on the Self‐Assembly of Bis(merocyanine) Dyes

The influence of static pre-stretching on the mechanical ageing of filled silicone rubbers for dielectric elastomer applications

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