Performance Of Polydimethylsiloxane Research Articles

Influence of Surfactants on the Microstructure and Performance of PDMS-E Grafted Gelatin Films

Polydimethylsiloxane grafted gelatin (PGG) polymers were prepared from mono-epoxy terminated polydimethylsiloxane (PDMS-E) macromonomer and gelatin, and surfactants were used to enhance the compatibility of the two polymers phases. The influences of surfactants, including sodium dodecyl sulfate (SDS), sodium dodecyl benzene sulfonate (SDBS), dodecyl trimethylammonium bromide (DTBA), and Tritox-100, on the microstructure and performance of polymers films were researched. XPS and FTIR results confirmed that PDMS-E was successfully grafted to gelatin chains. The results of SEM, DSC, TGA and surface contact angle indicated that microstructure of the PGG/SDS film was mainly controlled by the grafting effect on the gelatin matrix, and a tightly cross-linked network structure formed in PGG/SDBS film. However, few changes were present in the DTAB and Tri-100 systems. Surfactants played a crucial role in deciding the detailed microstructure of the grafted gelatin films, and induced the changes of hydrophobicity, flexibility and thermal properties of the polymer films.

Effect of embedded activated carbon nanoparticles on the performance of polydimethylsiloxane (PDMS) membrane for pervaporation separation of butanol

BACKGROUND The pervaporation separation method is considered to be a promising technique for biobutanol recovery from fermentation broths. In this work, activated carbon nanoparticles were embedded in polydimethylsiloxane (PDMS) membranes to improve the pervaporation performance. RESULTS Adding 6 wt% nano-additives in PDMS membranes increased the flux and separation factor by 42.6% and 51.9%, respectively, compared with neat membranes at 37°C. Enhanced performance is due to: 1 the presence of additional sorption sites within the membrane with a high affinity for butanol; and 2 the porous structure of the nanofillers generate new pathways for facilitated mass transport through the membrane. The effect of the operating temperature and particle concentration on membrane performance was investigated. Membrane performance improved with an increase in the operating temperature. Higher temperature resulted in increased free volume in the PDMS chains leading to higher diffusion of butanol. Mechanical tensile tests showed that nanocomposite membranes have better mechanical stability in comparison with neat PDMS membranes with the best performance observed at 6 wt% of the nano-additives. CONCLUSION The presence of activated carbon nanoparticles in the matrix of PDMS membranes leading to higher flux and separation factor can be beneficial for pervaporation separation of butanol from fermentation broths. © 2017 Society of Chemical Industry

Polyacrylate membranes for tunable liquid-filled microlenses

We present the use of polyacrylate membranes for the fabrication of pneumatically actuated variable lenses. Whereas the most commonly used membrane material for tunable liquid-filled lenses is polydimethylsiloxane (PDMS), polyacrylate membranes have the advantages of high resistance to swelling in silicone oil and enhanced compatibility with a wide range of aqueous optical liquids. These features are quantitatively demonstrated by comparing the material properties and performance of PDMS and polyacrylate membrane lenses. The optical transparency of polyacrylate is more than 92%. The surface roughness is below 3.3 nm rms, and reversible elastic deformation could be demonstrated. Optical measurements show that the cutoff frequency of the modulation transfer function of polyacrylate lenses with different liquid fillings, using a reference contrast of 0.2, is more than 1.5 times larger than that of the same system assembled with PDMS membranes filled with water.

Thermal stability and electrical behavior of polydimethylsiloxane nanocomposites with carbon nanotubes and carbon black fillers

In this work, the performance of polydimethylsiloxane (PDMS) nanocomposites with carbon black (CB) and multi-walled carbon nanotube (MWCNT) fillers was studied. The carbon nanofillers were first introduced in the solvent to promote an adequate dispersion. The silicone rubber was then reinforced with the carbon nanofillers by a mechanical mixing process followed by film casting. It was found that only small amount of MWCNTs is required to reach the percolation threshold that produces high electrical conductivity. Filler size and segregation, as observed by scanning electron microscopy, play important roles in determining the electrical properties of silicone elastomer filled composites. Transmission electron microscopy was also performed to examine the tube–tube interaction of MWCNT in silicone rubber. The MWCNT/PDMS nanocomposites have higher electrical conductivity value compared to the CB/PDMS nanocomposite. The percolation threshold for MWCNT/PDMS nanocomposites was approximately 1.0 vol% of MWCNT loading with a value of –4.06 log σ (S/cm). On the contrary, no obvious percolation threshold of CB/PDMS nanocomposites was observed, as the CB fillers added from 0.5 to 2.0 vol% in the PDMS. The MWCNT/PDMS nanocomposite also showed better thermal stability than the CB/PDMS nanocomposite. The onset temperature for 0.5 vol% of MWCNT/PDMS and CB/PDMS nanocomposites were 528°C and 492°C, respectively.

Surface texture and wetting stability of polydimethylsiloxane coated with aluminum oxide at low temperature by atomic layer deposition

The performance of polydimethylsiloxane (PDMS) elastomer in many of its applications, including surface molding and replication, microcontact lithography, and microfluidic device structures, is strongly influenced by its surface properties. While PDMS polymer is simple to use, the surface hydrophobicity and adsorptive properties of PDMS limit its functionality, for example, in aqueous microfluidic applications. Atomic layer deposition (ALD) is a low temperature vapor phase thin film coating technique that has recently been used to modify and encapsulate a wide range of polymer materials. In this work, the authors investigate reactions that proceed when PDMS polymer films are treated with cyclic gas exposure sequences commonly used to perform aluminum oxide ALD. Film growth is characterized by electron and infrared spectroscopy and by contact angle goniometry for a range of surface treatments and postdeposition air exposure times. The authors find that trimethylaluminum/water ALD can produce a smooth and uniform film coating on PDMS at 25–50 °C and that cracks become visible under optical microscopy for films >100 Å thick. At moderate temperatures, unique buckled surface textures appear in the deposited coating, which are ascribed to substrate thermal expansion effects. Aluminum oxide coatings on native PDMS, as well as on PDMS pretreated with UV ozone or oxygen plasma, show a hydrophilic surface condition immediately after deposition, but the surface becomes more hydrophobic after 24–48 h in ambient air or under inert gas storage, likely due to organic species out-diffusion through defects in the ALD coating. Infrared analysis is also used to identify consistent mechanisms associated with subsurface ALD nucleation on cast PDMS layers. These results provide valuable insight into a means to reliably modify the surface of PDMS using vapor phase precursor/surface reactions.

Effect of membrane pretreatment on performance of solvent resistant nanofiltration membranes in methanol solutions

This paper reports the effect of membrane pretreatment using different organic solvents on the performance of polyamide, polyimide and polydimethylsiloxane (PDMS) membranes in methanol solutions. Membrane pretreatment using acetone, methanol and toluene results in significant changes of membrane flux and rejection for polyamide- and polyimide-based membranes (Desal-DK and STARMEM 228) due to membrane swelling. The Performance of a polydimethylsiloxane (PDMS)-based membrane (MPF-50) in methanol solutions was not significantly affected by membrane pretreatment.

New Advances in Molding and Printing Processes for Organic/Plastic Electronics Using Chemically Modified Stiff, Photocured Poly (dimethylsiloxane) (PDMS) Elastomers Designed for Nano-Resolution Soft Lithography

ABSTRACTThe development of new materials for organic/plastic electronics allows us to fabricate novel devices through unconventional approaches. The ‘soft lithography technique’ has been widely used in replicating and fabricating small features. This technique is a low cost alternative to photolithography by generating structures from masters to substrates, which employ ‘elastomeric materials’, such as highly stretchable silicon elastomer, polydimethylsiloxane (PDMS) to replicate or transfer the original features to a variety of substrates by molding and printing processes. Since the resolution of pattern transfer significantly relies on the performance of polydimethylsiloxane (PDMS) stamp materials, commercial PDMS materials have shown limitations in high fidelity pattern transfer due to their low physical toughness and high thermal expansion coefficients. For those reasons, pattern fabrications using conventional PDMS materials are unable to satisfy our set of diverse demands, especially in the area of nano-scale replication. To achieve high performance in molding and printing, here we introduce a new strategy, design and synthesis of a modified PDMS silicon elastomer that is a stiffer and photocurable element to achieve our specific task of nano-scale resolution soft lithography. We then demonstrated its unique capabilities for the case of nano-features (300 nm wide) with narrow and tall heights (600 nm height) of photoresist, which is one of the most challenging ‘nano-patterning’ tasks in advanced soft lithography, which is often limited in its use at the nano-scale with other commercially available elastomers.

Fast Burning Rocket Propellants Based on Silicone Binders – New Aspects of an Old System

Fast burning rocket propellants based on ammonium perchlorate (AP) and polydimethylsiloxane (PDMS) binders have been formulated and basically characterized in aluminized and non aluminized versions. The thermodynamic performance of PDMS bound propellants is limited by the evaporation point of silicon dioxide (crystobalite at 2863 K), which is formed during the combustion. The maximum specific impulses calculated with an expansion ratio of 70 : 1 are ISP = 2340 N s/kg (238 s) for AP/PDMS and ISP = 2430 N s/kg (247 s) for AP/Al/PDMS formulations. With a tri-modal AP-fraction of 200 μm, 30 μm and 2 μm it was possible to achieve processable propellants with 83% and 84% solid loading. They give burning rates close to 60 mm/s at 10 MPa and pressure exponents between 0.5 and 0.6 in the range of 7–25 MPa. The thermodynamic specific impulse of these systems was calculated to ISP=2319 N s/kg (236 s) for AP/PDMS and ISP=2403 N s/kg (245 s) for AP/Al/PDMS formulations at 70 : 1 expansion ratio. Measurements of the glass transition point by DMA and TMA detected a time dependent partial crystallization of the used PDMS close to TG in the temperature range from −44 °C to −60 °C. Basic tests reveal high thermal and chemical stability with flash points over 300 °C and zero detonation sensitivity at 50 mm diameter. The property profile, so far determined, tends to fulfil the demands for applications as propellants with high burning rates and operating pressures together with a high thermal stability and a low vulnerability.