Effect Of Polydimethylsiloxane Research Articles

PDMS-PI composite coating toward multi-purpose development: Hydrophobic, low-friction/wear, and heat-resistance

Despite polyimide (PI) has been regarded as heat-resistant aviation material, but its high friction coefficient and insufficient abrasion resistance hinder the wide application. Herein, a versatile PDMS-PI composite coating with double-layer structure was prepared by crosslinking hybrid. The effect of polydimethylsiloxane (PDMS) on the hydrophobic, heat-resistant and tribological properties of PDMS-PI composite coating was explored. As expected, compared with the PI and SiO2-PI, PDMS-PI coating achieved the contact angle of 108.5° and only 5 wt% heat loss temperature at 578 ℃. Additionally, its wear rate obviously decreased by 38.5 %, and the friction coefficient declined from 0.33 to 0.07. The improvement contributes to excellent hydrophobic and heat resistance of dense protective layer and low-friction/wear of the PDMS coating layer.

Fabrication and design of poly(l‐lactic acid) membrane for passive MAP packaging of Brassica chinensis L

PLDx L copolymers were synthesized from physically stable rigid poly(l-lactic acid) (PLLA) and a few different molecular weights of polydimethylsiloxane (PDMS) to increase the O2 and CO2 permeabilities of PLLA films and make them acceptable for packaging highly respirable products. The effect of PDMS on the morphology, mechanical properties, and gas permeability of PLDx L was investigated. Copolymers showed approximately 10 times the fracture strain and 1.7 times the CO2 and O2 permeabilities of neat PLLA. Additionally, PLDx L maintained an increased CO2 /O2 perm-selectivity consistent between 5 and 40°C. Passive modified atmosphere packaging of Brassica chinensis L was developed to assess the membrane's impact on headspace gas inside the package. The results showed that poly(amide)/poly(ethylene) packaging with 48cm2 PLD1.8 L membrane as a breathing window can provide 50g B. chinensis L. with a healthy atmosphere of 3%-8% O2 and 5%-8% CO2 between 6 and 22 days. Vegetables packaged in PLD1.8 L had the lower respiration rate, lower nitrite contents, and less proliferation of microorganisms. Moreover, a suitable atmosphere kept vegetables with higher ascorbic acid and a good appearance after more than 2 weeks of storage at 5°C. PRACTICAL APPLICATION: The permeability of the PLLA-based membrane can be adjusted for the breathable window membrane of sealed fresh products. In the future, several types of film could be developed to match the respiratory and metabolic characteristics of different kinds of products. Such PLLA-based specialized membranes can refine the fresh-keeping function and be more attractive to the customer.

Effects of polydimethylsiloxane (PDMS) on triacetone triperoxide (TATP) volatilization

The effect of the polymer polydimethylsiloxane (PDMS) on triacetone triperoxide (TATP) volatilization was explored. TATP vapor contained in PDMS, known as the TATP polymer odor capture and release training aid (POCR), can be used to train field vapor detection systems, such as canines. Thermogravimetric analysis (TGA) was used to define the vapor pressure and enthalpy of sublimation for TATP and to calculate values for comparison using the TATP POCR. The vapor pressure (at 25 °C) and enthalpy of sublimation for bulk TATP were 0.0474 torr and 84.8 kJ/mol, respectively. The vapor pressure (at 25 °C) of TATP within the POCR was lower, at 0.00897 torr. The enthalpy of volatilization for the TATP POCR was also lower at 25.7 kJ/mol, implying that while it took less energy for TATP to enter the gas phase from the PDMS, the tendency for it to do so was lower. These interactions between TATP and the PDMS can be used to explain the headspace concentrations above TATP and the TATP POCR at equilibrium, despite differences in quantity and surface area. Finally, the vapor pressure (0.0520 torr at 25 °C) and enthalpy of sublimation (84.9 kJ/mol) were determined for deuterated TATP, showing that deuterium does not significantly affect sublimation of TATP.

Effect of tuned elasticity and chemical modification of substrate on fibrotic and healthy lung fibroblasts

Response to substrate elasticity, dependent on mechanical properties of cells, differs for lung fibroblast derived from idiopathic pulmonary fibrosis (IPF) and the healthy ones. These altered interactions might potentially act as a ‘biomarker’ for easy and reliable IPF diagnosis. In this work, systematic studies on the effect of polydimethylsiloxane (PDMS) substrate elasticity, tuned stepwise from 600 kPa to 1.5 MPa on the growth of IPF–derived (LL97A) and healthy (LL24) lung fibroblasts were reported. Additionally, impact of substrate chemistry on both cell lines was studied for fibroblasts cultured on glass substrates modified with three organosilanes – 3-aminopropyltriethoxysilane (APTES), 3-mercaptopropyltriethoxysilane (MPTES) and 3-glycidyloxypropyl trimethoxysilane (GOPS), with different end groups. Finally, the effect of the simultaneous modification of mechanical and chemical properties on the cellular behavior was studied for fibroblast cultured on PDMS substrates covered with silanes. The growth of cells was traced using fluorescence microscopy and analyzed quantitatively by nucleus-cytoplasm ratio, indicating strong, cell-dependent impact of substrate elasticity dominating over effect of chemical modification.

Effect of PDMS on the waterproofing performance and corrosion resistance of cement mortar

The currently used cement hydrophobic additives are either expensive or damageable during use, limiting their large-scale application on concrete. In this study, low-cost and commercially available polydimethylsiloxane (PDMS) is proposed as a cement admixture for the hydrophobic modification of cement mortar. The uniform distribution of PDMS in hardened cement mortar (HCM) attributes integral hydrophobicity to HCM. The PDMS modified HCM (M-HCM) surface exhibits superhydrophobicity, with a contact angle of 157.3° and a sliding angle of 8.7°. The superhydrophobic M-HCM is mechanically robust after being abraded for 110 m distance. In addition, the water absorption of the M-HCM reduced approximately 92.51%, and the corrosion resistance of the M-HCM obviously improved. The compressive strength and flexural strength of the M-HCM reduced by 30.9% and 18.1%, respectively, while the toughness of the M-HCM improved. Furthermore, the durability of the M-HCM against weathering, sulfate attack, and leaching significantly improved in comparison with the U-HCM. This type of mechanically robust superhydrophobic M-HCM material can be used in the waterproof concrete and anti-corrosive concrete.

Surface Microstructure Regulation of Porous Polymer Microspheres by Volume Contraction of Phase Separation Process in Traditional Suspension Polymerization System.

In the present work, the suspension polymerization method is used for the preparation of porous polymer microspheres with different surface morphology, and the preparation mechanism is systematically expounded. The morphology results show that the smooth, convex, and wrinkled microspheres could be controlled by adjusting the ratio of monomer to porogens. The micelles forming the framework support the "Eggshell," and its size and shape directly affect the morphology of "Eggshell." The addition of monomers (GMA), whose polymer has low glass transition temperature (Tg ), is important for the formation of wrinkled morphology. The amount of toluene and polydimethylsiloxane also affects the surface morphology of microspheres. In addition, the effect of polydimethylsiloxane is also more significant. The preparation process of the wrinkled P(GMA-St-EGDA) microspheres with abundant epoxy groups can be amplified. The morphology of the material prepared in the 100 L reactor is well maintained, and the yield in the size range of 80-160 µm is more than 80%. The surface wrinkled porous polymer microspheres have potential applications in the fields of enzyme carrier, separation and purification, and light scattering.

Atomic force microscopy technique for the surface characterization of sol–gel derived multi-component silica nanocomposites

Sol–gel derived multi-component silica nanocomposites are widely accepted as materials in a host of medical applications including bioactive drug carriers. In this paper, both the effect of polydimethylsiloxane (PDMS) (20, 25, and 30wt.%) on nanometre-scale phase separation and the surface properties of sol–gel processed polydimethylsiloxane/calcium phosphate/silica (PDMS-modified CaP/SiO2) are reported. The evaporation-induced self-assembly (EISA) technique was used to prepare the solid films of multicomponent silica nanocomposites. Atomic force microscopy (AFM) in PeakForce quantitative nanomechanical mapping (PF-QNM) mode was used to examine the surface heterogeneity including morphology, surface roughness, adhesion and elasticity of the composites structure on the nanometre-scale. The resulting materials were nanoscopically phase separated, but macroscopically uniform. PF-QNM results revealed the presence of elastic domains of PDMS-rich nanophase and rigid domains belonging to bioactive silica-rich nanophases. The nanophase separation depends on the amount of PDMS. This effect was correlated with an increase in the adhesion force, mean roughness (Ra) and root mean square roughness (Rq) and a decrease in the Young’s modulus in the composites as a function of PDMS content. The statistical analyses of these results showed significant differences between nanocomposites with different amounts of PDMS. The best compatibility and the nanophase dispersion were observed for 20% of PDMS in the nanocomposite’s structure.

An investigation of the effect of silicone oil on polymer intraocular lenses by means of PALS, FT-IR and Raman spectroscopies

The effect of the polydimethylsiloxane (PDMS) based silicone oil, that is widely used in vitreoretinal surgery, on internal structures of the polymer intraocular lenses was investigated. The effect of PDMS was studied on the polymethyl methacrylate (PMMA) rigid lenses and poly(2-hydroxyethyl methacrylate) (PHEMA) flexible lenses. The research was carried out by means of the positron lifetime spectroscopy (PALS) as well as the infrared spectroscopy (FT-IR) and the Raman spectroscopy (RS). The studies involving the use of PALS and FT-IR methods have revealed that the PHEMA based lenses absorbed, whereas the PMMA lenses did not absorb, silicone oil. The results obtained with the use of the RS method were inconclusive, probably due to the too low intensity of the characteristic PDMS bands. The evidence from this study was discussed in terms of physics and related to the clinical use of both silicone oil and intraocular lenses.

Effect of polydimethylsiloxane on the mid-temperature strength of gelcast Al2O3 ceramic parts

An approach using polydimethylsiloxane (PDMS) as mid-temperature strengthening phase in gelcasting for the fabrication of ceramic parts with complex internal cores was firstly proposed and adopted. The bending strength of samples with PDMS at 500°C was greatly improved from almost 0 to 1.037MPa when 4wt.% PDMS was added. The distinct networks formed by PDMS were responsible for the improvement in mid-temperature strength which was confirmed by the result of scanning electron microscopy (SEM). Based on the analysis of X-ray scan, the validity of PDMS was also testified in experiments.

Effect of polydimethylsiloxane (PDMS) coating on TiO2-based MALDI matrix for dimethyl methylphosphonate (DMMP) analysis

TiO2 nanoparticles were used as MALDI matrix for detecting dimethyl methylphosphate (DMMP) and its efficiency, in terms of DMMP signal intensity in the MALDI-MS analysis, was compared with that of polydimethylsiloxane (PDMS)-coated TiO2 matrix. Intensity of the DMMP signal in the MALDI-MS analysis was significantly increased by using PDMS-coated TiO2 matrix instead of bare ones. It was verified using FT-IR that the enhanced DMMP signal upon PDMS coating on TiO2 matrix is a result of weaker interactions between DMMP molecule and the PDMS-covered surface than that of bare TiO2. A weaker DMMP-matrix interaction can facilitate desorption of DMMP from the matrix surface in the MALDI process, yielding a higher sensitivity to DMMP in the MALDI-MS.

Effect of polydimethylsiloxane and ethylcellulose on in vitro permeation of centchroman from its transdermal patches

This research aims at the development of controlled release contraceptive transdermal patches of centchroman using ethylcellulose (EC) as film-forming polymer, polydimethylsiloxane (PDMS) as pressure sensitive adhesive with propylene glycol and Di-n-butyl-phthalate for their penetration enhancer and plasticizing properties, respectively. The physicochemical compatibility of the drug and the polymers was performed by differential scanning calorimetry and Fourier transform infrared (FTIR) spectroscopic technique. Effects of EC and PDMS ratios on moisture uptake, moisture content, tensile strength (TS), Young’s modulus, adhesive strength, water vapor transmission rate (WVTR) and in vitro permeation of centchroman through Sprague–Dawley rats abdominal skin using Franz’s diffusion cell were evaluated. A 32 full factorial design was employed to observe the effect of independent variables; concentration of ethyl cellulose and PDMS on drug permeated after 32 h, which was selected as dependent variable. Compatibility studies suggested that there were no significant interaction between the drug and polymers used. It was found that incorporation of only EC resulted in too hard patches and addition of PDMS produced patches with lower TS, increased percentage elongation, WVTR and Young’s modulus. Statistical analyses suggested that independent variables have a significant effect on the dependent variable. All formulation follows zero-order release kinetics with r2 > 0.990. In conclusion, drug in adhesive transdermal patches can be successfully fabricated for non-steroidal contraceptive centchroman to obtain a zero-order release systems.

Study on the effect of polydimethylsiloxane from the viewpoint of oxygen content in oil.

It has been reported that polydimethylsiloxane (PDMS) inhibits oxygen dissolution into oil by forming a monolayer on the surface of the oil, thereby reducing thermal oxidation. In the present study, the distribution of PDMS was determined by the inductively coupled plasma atomic emission spectroscopy in standing PDMS-containing canola oil. PDMS did not disperse in the oil uniformly, but there was a tendency that the PDMS concentration decreased as the depth of oil increased, and the concentration of the bottom part was the lowest. When canola oil was covered with PDMS by dropping it gently on the surface of the oil and kept at 60°C, the oxygen content and oxidation of the oil were lower than those of the control canola oil. PDMS-containing canola oil and canola oil were heated with stirring from room temperature to 180°C, and then allowed to stand while cooling. Oxygen contents of both oils increased up to 120°C then dropped abruptly. While cooling, oxygen contents sharply increased at 100°C and approached the saturation content, although the increase for PDMS-containing canola oil was a little slow. Likewise, the thermal treatment of PDMS-containing canola oil and canola oil at 180°C for 1 h under stirring was repeated 5 times with standing intervals for 2-3 days at room temperature. Oxidation of the former was less than that of the latter in spite of its high oxygen content. In conclusion, the oxygen content of oil with/without PDMS addition increased, but oxidation of PDMS-containing canola oil was inhibited both during heating and standing with intermittent heating. It was suggested that PDMS exerted its antioxidative effect regardless of whether it covered the oil or was dispersed in it.

Influence of soft segment molecular weight on the mechanical hysteresis and set behavior of silicone-urea copolymers with low hard segment contents

Effect of polydimethylsiloxane (PDMS) soft segment molecular weight (Mn = 3200, 10,800 and 31,500 g/mol) and urea hard segment content (2.0–11.4% by weight) on the hysteresis and permanent set behavior of segmented silicone-urea (TPSU) copolymers were investigated. In spite of very low hard segment contents, all copolymers formed self-supporting films and displayed good mechanical properties. When the mechanical hysteresis and set behavior of the silicone-urea copolymers with similar hard segment contents (around 7.5% by weight) but based on PDMS-3K, PDMS-11K and PDMS-32K were compared, it was very clear that as the PDMS molecular weight increased, hysteresis and instantaneous set values decreased significantly. Copolymers based on the same silicone soft segment (PDMS-11K or PDMS-32K) but with different hard segment contents showed a linear increase in hysteresis and a slight decrease in the instantaneous set as a function of hard segment content. Constant initial stress creep experiments also showed lower creep as the PDMS segment molecular weight increased for copolymers with similar urea contents. Since the critical entanglement molecular weight (Me) of PDMS is stated to be 24,500 g/mol, our results tend to suggest important contribution of chain entanglements on the hysteresis and instantaneous set of these silicone-urea copolymers.

Study on effect of polydimethylsiloxane in intumescent flame retardant polypropylene

The effect of polydimethylsiloxane (PDMS) in intumescent flame retarded polypropylene (PP) containing melamine phosphate (MP) was studied using limiting oxygen index (LOI), UL-94 test, thermogravimetric analysis (TG), real time Fourier transform infrared (FTIR) and pyrolysis/gas chromatogram/mass spectrometry (Py–GC/MS). It was found that the addition of PDMS into the PP/MP composites leads to a decrease in the LOI values of the PP/MP/PDMS composites, and the values increase gradually with the increase of the PDMS content. The UL-94 test results indicate that the PP/MP/PDMS composite with 30% PDMS reaches the V-0 rating compared with no rating of the PP/MP composite at the same MP loading. The water resistance of the PP/MP/PDMS composites was investigated, and the improved water leaching of MP was observed. The TG and RTFTIR results illustrate the thermal stability of the PP/MP composites containing PDMS is improved. Moreover, the pyrolysis of the PP/MP/PDMS composites was studied by the Py–GC/MS method.

Crystallization of polypropylene in the presence of a rigid and flexible additive

The effect of a rigid additive (nano-SiO2 filler) and a flexible additive [poly(dimethylsiloxane) elastomer] on the crystallization of polypropylene was studied under nonisothermal conditions with differential scanning calorimetry. Crystallization parameters were evaluated with standard equations, and the results were interpreted on the basis of the rate of nucleation, crystallization, and activation energy of crystallization. The observed effect of polydimethylsiloxane of increasing the crystallization rate and lowering the activation energy of crystallization was attributed to the effect of polydimethylsiloxane chain mobility at the interface, which facilitated the molecular mobility of polypropylene. Nano-SiO2, on the other hand, acted as a nucleating agent, and the nucleation effect was dependent on the cooling rate. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

Surface microtopography in siloxane–polyurethane thermosets: The influence of siloxane and extent of reaction

The effect of polydimethylsiloxane (PDMS) content, PDMS molecular weight, and the extent of prepolymerization reactions between hydroxyl functional PDMS and polyisocyanate were explored in order to understand the influence of these variables on the formation of surface microtopography in a siloxane–polyurethane thermoset. The system is based on a difunctional hydroxyalkyl terminated PDMS, trifunctional poly(caprolactone) polyol, and a polyisocyanate. The effect of PDMS content was studied with PDMS of MW 1000 and 2000. PDMS of MW 1000 was varied from 5% to 15% and with PDMS of MW 2000 the level was varied from 5% to 12%. Tapping mode AFM images of the surface topography were used to characterize the system. The extent of reaction prior to film formation was studied by FTIR and correlated with microdomain formation in the final polymer film. Two different mixing strategies were explored: one where all of the ingredients were mixed together and a second approach where PDMS and polyisocyanate were mixed first, followed by the addition of the trifunctional polyol. Monte Carlo simulation of the polymerization with 10% PDMS of MW 1000 in the formulation revealed that there was a window of conversion for both PDMS and isocyanate at which the system spontaneously phase separates to form a microtopographical surface.

Effect of polydimethylsiloxane on oxidation of isotactic polypropylene

Addition of liquid polydimethylsiloxane to isotactic polypropylene retards its non-inhibited and inhibited oxidation by molecular oxygen. We propose that the reasons for this retardation are the migration of mobile free radicals and the reversible transition of antioxidant into inclusions of liquid siloxane in the polymer matrix.