Synthesis of new superhydrophobic nanosilica and investigation of their performance in reinforcement of polysiloxane

We reported a new facile method to synthesize superhydrophobic nanosilica using glycidoxypropyltrimethoxysilane and dodecylamine as treatment agents. Also, we systemically investigate their performance in reinforcement of poly(dimethylsiloxane) (PDMS) rubber. Fourier transform infrared spectrum, contact angle (CA) and thermogravimetric analysis (TGA) measurements were used to characterize the modified nanosilica. Results show that the inherent hydrophilicity of parent nanosilica surface can be greatly altered through this modification method. The CA of as‐prepared superhydrophobic nanosilica can reach 160.2°. The properties of as‐prepared modified nanosilica‐filled PDMS composites were systemically investigated by dynamic rheological test, scanning electron microscopy, TGA, dynamic mechanical analysis. These as‐prepared superhydrophobic nanosilica exhibit uniform dispersion in the PDMS matrix, and their composites also show good mechanical properties and distinct advantage on thermal stability compared with those of the pure silica‐filled PDMS composites. Also described is the probable mechanism for the reinforcement of as‐prepared superhydrophobic nanosilica‐filled PDMS. POLYM. COMPOS., 31:1628–1636, 2010. © 2009 Society of Plastics Engineers     

Preparation and characterization of novel polydimethylsiloxane composites used POSS as cross‐linker and fumed silica as reinforcing filler

A series of novel polydimethylsiloxane (PDMS) composites were prepared using octa[(trimethoxysilyl)ethyl]‐POSS (OPS) as cross‐linker and fumed silica as reinforcing filler. The cross‐linked networks, morphologies, thermal and mechanical properties of these novel PDMS composites were examined by attenuated total reflection infrared spectroscopy and the extraction/swelling experiment, scanning electron microscope, thermogravimetric analysis, and universal tensile testing machine, respectively. It was found that both the resistance to thermal degradation and mechanical properties of the novel PDMS composites were improved greatly by adding fumed silica. The prominent improvements in resistance to thermal degradation and mechanical properties of novel PDMS composites were likely attributed to the enhanced interaction of PDMS chains and aggregated particles resulted from synergistic effect between POSS and fumed silica. Meanwhile, we also found that the resistance to thermal degradation of the PDMS composites was lowered slightly with the further increment in loading fumed silica, but their mechanical properties were enhanced. The slight decrease in trend of the resistance to thermal degradation of the novel PDMS composites was likely ascribed to the increasing amount of hydroxyl groups resulting from fumed silica. And the improving mechanical properties were mainly attributed to the increasing interaction of PDMS chains and aggregated particles originated from synergistic effect between POSS and fumed silica. POLYM. COMPOS., 34:1041–1050, 2013. © 2013 Society of Plastics Engineers     

Preparation and properties of poly(dimethyl siloxane)–colloidal silica/functionalized colloidal silica nanocomposites

Aqueous spherical colloidal silica (CS) particles with a diameter of 15 ± 5 nm were modified with three different types of monofunctional silane coupling agents to prepare functionalized colloidal silica (FCS) particles. The effects of the surface chemistry of the FCS were studied as a function of the CS/FCS loading in the poly(dimethyl siloxane) (PDMS) polymer. The prepared PDMS–CS/FCS composites were investigated for their physical properties both in the cured and uncured states. The extent of filler–filler and filler–polymer interactions was found to vary with the type of functionalizing agent used to treat the surface of the CS. The filler–filler interaction appeared to be predominant in the PDMS–CS composites, and improved filler–polymer interaction was indicated in the case of the PDMS–FCS composites. The composites containing CS treated with methyltrimethoxysilane exhibited relatively better optical and mechanical properties compared to the other PDMS–FCS composites. This study highlighted the importance of judiciously choosing functionalizing agents to achieve PDMS–FCS composites with predetermined optical and mechanical properties. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Mechanical,dielectric, and thermal properties of polydimethylsiloxane/polysilsesquioxane nanocomposite for sealant application

Polysilsesquioxanes (PS) powder was synthesized from methyltrimethoxysilane and vinyltrimethoxysilane by hydrolytic condensation method in aqueous phase. The prepared PS powder was characterized using Fourier transform infrared spectroscopy, particle size, and polydispersity of the powders was determined using dynamic light scattering technique. Polydimethylsiloxane (PDMS) nanocomposites and the sealant were synthesized using different weight percentage (1–4 wt %) of PS powder and hydrophobic fumed silica. Tensile strength and thermal stability of the nanocomposites showed perceptible enhancement on increasing the filler ratio when compared to pristine PDMS composites. The surface morphology and the extent of filler dispersion were visualized from the scanning electron microscopy images. Dielectric strength of the composites also showed significant improvement on increasing the filler loading. Poly(methyl/vinyl)silsesquioxane (PMVS) (4 wt %) reinforced composites showed a considerable enrichment in properties when compared to other formulations. Adhesive strength of silicone sealant on both the alumina and mild steel substrate was studied by conducting lap shear test. PMVS-loaded nanocomposites exhibited more adhesive strength on both the substrates and hence it can be used as a sealant in electronic assemblies. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47228.     

Preparation,morphology, and mechanical properties of elastomers based on polydimethylsiloxane/ polystyrene blends

Polydimethylsiloxane/polystyrene (PDMS/PS) blends were prepared by radical copolymerization of styrene (St) and divinylbenzene (DVB) in the presence of α,ω‐dihydroxy‐polydimethylsiloxane (PDMS), using benzoyl peroxide as initiator. The PDMS/PS blends obtained by this method are a series of stable, white gums, when the feed ratio of PDMS to St is 60/40 and DVB to St is not more than 2.0 wt %. Elastomers based on PDMS/PS blends were formed by crosslinking PDMS with methyl‐triethoxysilicane (MTES). The MTES dosage was much larger than the amount necessary for end‐linking hydroxy‐terminated chains of PDMS, with the excess being hydrolyzed to crosslinked networks, which were similar to SiO₂ and acted as filler. Mechanical property measurements show that the elastomers thus formed exhibit superior mechanical properties with respect to pure PDMS elastomer and the elastomers based on PDMS/PS system we prepared before. Moreover, investigations were carried out on the elastomers by extraction measurement and scanning electron microscopy (SEM). The extraction data show that the sol‐fraction decreases with increasing the feed ratio of DVB to St. SEM observation demonstrates that the elastomer has a microphase‐separated structure consisting of dispersed PS domains within a continuous PDMS matrix, and the extracted material exhibits a porous structure. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Synthesis and characterization of novel poly(dimethylsiloxane)/polyindole composites

A series of composites of polyindole (PIN) and poly(dimethylsiloxane) (PDMS) were synthesized chemically using FeCl₃ as an oxidant agent in anhydrous media. The composites were characterized by FTIR and UV‐visible spectroscopies, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), X‐ray diffraction (XRD), elemental analysis, inductively coupled plasma‐optic emission spectroscopy (ICP‐OES), magnetic susceptibility, stress–strain experiments, and conductivity measurements. The conductivities of PIN at different temperatures were also measured and it was revealed that their conductivities were slightly increased with increasing temperature. Moreover, the freestanding films of PDMS/PIN composites were prepared by casting on glass Petri dishes to examine their stress–strain properties. From thermogravimetric analysis results it was found that PDMS/PIN composites were thermally more stable than PIN. Thermal stabilities of PDMS/PIN composites increased with increasing PIN content. It was found that the conductivities of PDMS/PIN composites depend on the indole content in the composites. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Effect of natural and organically modified montmorillonite clays on the properties of polydimethylsiloxane rubber

The effects of natural (MT) and organically modified (O‐MT) montmorillonite clays on the properties of polydimethylsiloxane (PDMS) rubber were evaluated. Rubber composites with different clay contents were prepared by a compounding procedure in an open two‐roll mill, which was followed by a compression‐molding step in which the PDMS matrix was peroxide crosslinked. The clay rubber composites were characterized by swelling measurements in toluene, thermogravimetric analyses, X‐ray diffraction, scanning electron microscopy, and tensile tests. The introduction of MT restricted the solvent swelling and increased the crosslinking density of the rubber, which indicated the formation of a covalent filler–matrix interface. The enhanced interaction between MT and PDMS reduced the aggregation size of MT particles in the MT composites and promoted an increase in the separation of the clay layers. When the rubber was filled with O‐MT, a higher solvent amount was incorporated in the material, and this trend increased with the clay content. Moreover, the low interaction between O‐MT and the PDMS chains resulted in larger clay aggregates in the O‐MT composites compared to those with MT. Despite the different interface natures, both clays enhanced thermal stability and acted as reinforcing fillers in relation to Young's modulus and tensile strength. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Multi-contact hybrid thermal conductive filler Al2O3@AgNPs optimized three-dimensional thermal network for flexible thermal interface materials

In this work, a multi-contact Al₂O₃@AgNPs hybrid thermal conductive filler was synthesized by in-situ growth method to fill high thermal conductivity polydimethylsiloxane (PDMS)-based composites to prepare TIMs. And the thermal conductivity, electrical conductivity, and mechanical properties of the composite materials were studied. During the synthesis process of the multi-contact hybrid filler, different concentrations of silver ions were reduced to generate silver nanoparticles and attached to the surface of Al₂O₃. Al₂O₃@AgNPs/PDMS thermally conductive composites were prepared by changing the filler addition. Using SEM, XPS, and XRD is used to characterize the morphology and chemical composition of Al₂O₃@AgNPs hybrid filler. The thermal conductivity of PDMS-based composites with different AgNPs content under 70 wt% filler loading was studied. The results show that the thermal conductivity of PDMS-based composites filled with 7owt%Al₂O₃@3AgNPs/PDMS multi-contact hybrid filler is 0.67 W/m·K, which is 3.72 times that of pure PDMS, and is higher than that of unmodified Al₂O₃ with the same addition amount. /PDMS composite material has a high thermal conductivity of 24%. This work provides a new idea for the design and manufacture of high thermal conductivity hybrid fillers for TIMs.     

Pervaporative studies using polyimide‐filled PDMS membrane

The application of pervaporation (PV) to the removal of volatile organic from aqueous solutions has become very interesting in the last few years. It is caused by the increasing level of compounds, such as petrochemical solvents (benzene, toluene, and xylenes) or chlorinated solvents (trichloroethylene or tetrachloroethylene), which are polluting the natural environment. In this work, effects of polyimide (PI) (prepared by direct polycondensation of dianhydride and diamine followed by thermal cyclization of polyamic acid) filler on PV properties of poly(dimethyl siloxane) (PDMS) have been studied. PDMS membrane filled with PI was used for the separation of benzene (Bz) and toluene (Tol) from the diluted aqueous solution and the results were compared with the neat PDMS membrane of similar thickness. The PDMS‐PI membrane showed normalized flux (J′) upto 1.2 kg μm/m²h for Bz and 1.48 kg μm/m²h for Tol and selectivity of organics varies from 7.3 to 3.2 for Bz and 8.9 to 2.8 for Tol with increasing concentration of organics. Concentration of PI filler in PDMS varied 5–25% w/w. PI filler increases thermal as well as mechanical stability of filled PDMS membranes. PDMS membrane filled with 25% PI was chosen for the pervaporation studies. The membranes were characterized by FTIR, thermogravimetric analyser and scanning electron microscopy. The mechanical strength of PDMS filled with 25% w/w PI (SPI‐25) membrane was found to be 2.7 MPa. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Large strain and toughness enhancement of poly(dimethyl siloxane) composite films filled with electrospun polyacrylonitrile-graft-poly(dimethyl siloxane) fibres and multi-walled carbon nanotubes

Unfilled cross-linked poly(dimethyl siloxane) (PDMS) is a weak material and is generally filled with high levels of particulate fillers such as silica, calcium carbonate and carbon black to improve its mechanical properties. The use of fibrous fillers such as electrospun nanofibres and multi-walled carbon nanotubes as fillers for PDMS has not been widely studied. In this study anew copolymer, polyacrylonitrile-graft-poly(dimethyl siloxane) (PAN-g-PDMS), is used as fibrous filler for PDMS. The graft copolymer is electrospun to produce the fibre filler material. It is shown how the PDMS content of the graft copolymer provides increased compatibility with silicone matrices and excellent dispersion of the fibre fillers throughout a silicone matrix. It is also shown that it is possible to include multi-walled carbon nanotubes in the electrospun fibres which are subsequently dispersed in the PDMS matrix. Fibre mats were used in the non-woven and the aligned forms. The differently prepared fibre composites have significantly different mechanical properties. Conventional composites using fibrous fillers usually show increased strength and stiffness but usually with a resultant loss of strain. In the case of the composites produced in this study there is a dramatic improvement in the extensibility of the non-woven PAN-g-PDMS fibre mat filled silicone films of up to 470%.     

Influence of Polyhedral Oligomeric Silsesquioxanes (POSS) on Thermal and Mechanical Properties of Polydimethylsiloxane (PDMS) Composites Filled with Fumed Silica

A series of novel PDMS composites filled with a given amount of fumed silica were first prepared using divinyl-hexa[(trimethoxysilyl)ethyl]-POSS as cross-linker by hydrolytic condensation in the presence of organotin catalyst. The crosslinking reaction, the morphology, thermal behaviors and mechanical properties of the novel PDMS composites were characterized by attenuated total reflection infrared spectroscopy, scanning electron microscope, thermogravimetric analysis and universal tensile testing machine, respectively. It was found that the resistances to thermal degradation, thermo-oxidative decomposition of the novel PDMS composites were greatly improved by incorporation of POSS cross-linker, compared with that of the reference material (MT-1). Meanwhile, we also found that their thermal properties and mechanical properties were gradually enhanced with the further increment in loading amount of POSS cross-linker. The pronounced enhancements in thermal properties and mechanical properties of novel PDMS composites were likely attributed to the increasing interaction of PDMS chains and aggregated particles from synergistic effect between POSS and fumed silica.     

Studies of the effect of titanate coupling agent on the performance of polypropylene–calcium carbonate composite

Composites of polypropylene—CaCO₃ coated with isopropoxy triisostearoyl titanate have been prepared on Buss Ko-Kneader. These composites have been evaluated for mechanical properties, melt index, dispersion, and adhesion of polymer to filler using the scanning electron microscope. Calcium carbonate being a platelike substance with low aspect ratio results in composites having inferior tensile properties but superior impact characteristics. Uniform dispersion of filler in the composite and long alkyl chains of the coupling agent provide additional advantages such as improved melt index, higher tensile elongation, and better optical properties.     

The effect of blending sequence on the structure and properties of poly(vinyl chloride)/chicken eggshell powder composites

The effect of the blending sequence of poly(vinyl chloride)/chicken eggshell powder (PVC/ESP) composites on the processing, mechanical properties, morphology, and thermal decomposition were investigated. The compounding of composites was done by using a Rheomix mixture internal mixer at 180°C and a rotor speed of 30 rpm for 10 min to allow the mixing torque to reach a steady state. The mechanical and morphological properties of PVC/ESP composites under different blending sequences have been characterized by a lightweight tensile tester and scanning electron microscopy. The thermal stability and thermal analysis of the composites were performed by thermogravimetric and differential scanning calorimetric analysis. Good interfacial adhesion between filler and matrix in composites prepared via blending sequence 2 has improved the tensile strength and thermal stability of the PVC/ESP composite compared with blending sequence 1 as proved from scanning electron microscopy results on the tensile fracture surface of the composites. Thermogravimetric analysis results show that blending sequence 2 exhibited higher thermal stability comparable with blending sequence 1. In addition, the differential scanning calorimetric analysis results illustrate that the composites prepared via blending sequence 2 exhibit higher melting and crystallization temperature values compared with composites prepared via blending sequence 1. J. VINYL ADDIT. TECHNOL., 23:298–304, 2017. © 2015 Society of Plastics Engineers     

Biogenic silica short fibers as alternative reinforcing fillers of silicone rubbers

The performance of biogenic opaline silica short fibers, natural (NF) or modified with vinyltrimethoxysilane (MF), as primary or secondary fillers in an elastomeric matrix of poly(dimethylsiloxane), PDMS, was evaluated in this work. Compounding was carried out on a two‐roll mill, and the PDMS matrix was peroxide crosslinked by compression molding. Characterization of these fibers was performed by BET surface area, X‐ray fluorescence, infrared spectrum, X‐ray diffractometry, field emission scanning electron microscopy, and Bayer's test. The obtained rubbers were characterized by thermogravimetric analysis, field emission scanning electron microscopy, swelling measurements in cyclohexane, dynamic mechanical analysis, and tensile tests. As primary filler, NF and MF increased the thermal stability of the PDMS matrix, and MF also restricted the swelling of this matrix in cyclohexane. For the rubbers containing NF or MF as secondary filler, the swelling restriction was caused by both fibers. Silica short fibers were also efficient as primary filler in PDMS with regard to Young's modulus and tensile strength, and as secondary filler, NF and MF were effective reinforcing fillers in relation to storage and Young's modulus, resulting on an increase in the stiffness of the rubbers. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 290–299, 2006     

Preparation and characterization of lead monoxide filled unsaturated polyester based polymer composites for gamma radiation shielding applications

Particulate polymer composites of Isophthalate based unsaturated polyester resin filled with different concentrations of lead monoxide were prepared. These composites were investigated for physical, thermal, mechanical, and gamma radiation shielding characteristics. The results of density evaluation, microscopic studies, and the radiation shielding properties for gamma rays of energy 0.662 MeV from Cs‐137 point source have been presented in this article. The results show that, the density of the composites was observed to increase with filler loading. The morphological analysis of the composites made using the scanning electron microscope showed that, the lead monoxide particles were observed to disperse uniformly in the polymer matrix with an average inter particle distance of about 10 μm and an average size of about 5.36 μm. The linear attenuation coefficient of the composites was found to increase with increased filler content in the composites. The highest value of 0.206 cm^?1 was found for 50 wt % of lead monoxide. These composites were observed to exhibit excellent % of heaviness and Half value layer in comparison with other conventional materials. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Tensile properties of LDPE + Boehmite composites

Effect of interfacial interactions on mechanical properties of composites of low-density polyethylene reinforced with micrometric Boehmite powders were studied in combination with two silane coupling agents vinyltri(2-methoxyethoxy)-silane (VTMES)-SCA 972 and 3-(trimethoxysilyl)-propylmethacrylate (3MPS)-SCA 989. Samples were prepared via melt mixing followed by compression or injection molding. Morphology and mechanical behavior of the composites were investigated as a function of the filler loading. The modulus of the composites increases with increasing contents of micrometric Boehmite particles. Environmental scanning electron microscopy (ESEM) examination reveals formation of fibrous structures upon addition of the treated micro fillers. We presume the fibrillation of the LDPE phase is related to changes of the matrix viscosity. Improvements in mechanical properties are attributed to homogeneous dispersion and good interfacial adhesion between the filler and the matrix, as evidenced by ESEM. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers     

Effect of ball milling on the mechanical properties and crystallization of graphene nanoplatelets reinforced short chain branched-polyethylene

Short-chain-branched-polyethylene (SCB-PE) is extensively used in domestic hot and cold piping systems. SCB-PE nanocomposites using graphene nanoplatelets (GNPs) as a filler, were prepared in this work. The effect of ball-milling as a premixing technique prior to melt-mixing, on the crystallization and the nanomechanical properties of the composites has been studied. Two sets of SCB-PE/GNPs nanocomposites with various filler loadings were prepared; one with and one without the ball-milling step. The dispersion of the filler was evaluated by optical microscopy while the crystallization process was studied using differential scanning calorimetry. The nonisothermal crystallization's experimental data were analyzed using various methods. The materials' nanomechanical behavior was investigated by conducting nanoindentation tests. A finite element analysis process was developed to extract the composites' stress–strain behavior. The composites prepared with ball-milling presented improved dispersion of GNPs in the SCB-PE matrix, which affected the crystallization, while nanoindentation tests showed significantly enhanced mechanical properties.     

聚乳酸/酯化纤维素/纳米CaCO_3复合材料的制备与表征

采用熔融共混法制备了聚乳酸(PLA)/酯化纤维素/纳米CaCO3复合材料,并通过力学性能测试、差示扫描量热仪、热重分析和扫描电镜等测试手段对复合材料的性能进行了表征。结果表明,当酯化纤维素和纳米CaCO3的总含量小于5%时,能够起到较好的增强作用,复合材料的力学性能明显优于纯PLA;酯化纤维素和纳米CaCO3的加入起到了异相成核作用,但会降低复合材料的热稳定性;酯化纤维素在复合材料中分散充分,无聚集现象;但当填料总含量大于10%时,纳米CaCO3发生明显发生聚集。     

Effect of different fillers on physical,mechanical, and optical properties of styrenic‐based thermoplastic elastomers

The effects of different fillers on physical, mechanical, and optical properties of styrenic‐based thermoplastic elastomers were investigated by experimental study. Poly[styrene‐b‐(ethylene‐co‐butylene)‐b‐styrene] block copolymer (SEBS)‐based thermoplastic elastomer composites were prepared in a co‐rotating intermeshing twin‐screw extruder, using silica and calcite as filler materials with three different particle sizes. The loading ratios in the composites were varied. Hardness, density, tensile strength, tear strength, compression set, wear resistance, transmittance, and haze measurements were performed. Thermal properties and morphological structure were investigated by differential scanning calorimeter (DSC) and scanning electron microscopy (SEM), respectively. The results show that, an interaction between silica and the polymer matrix exists, whereas calcite does not show any interaction with the polymer. Therefore, it is concluded that, calcium carbonate can be used in the composite as filler for cost efficiency, whereas silica can be used as reinforcing material in SEBS‐based thermoplastic elastomer composites, when optical properties are also concerned. POLYM. ENG. SCI., 2010. © 2009 Society of Plastics Engineers     

Synthesis and characterization of poly(dimethylsiloxane)–polythiophene composites

The synthesis was performed by the electropolymerization of thiophene on a poly(dimethylsiloxane) (PDMS)‐coated platinum electrode at 2.2 V with tetrabutylammoniumtetrafloroborate (TBAFB) as a supporting electrolyte and with acetonitrile as a solvent. The characterization of the PDMS–polythiophene (Pth) composites was carried out with cyclic voltammetry, Fourier transform infrared (FTIR), scanning electron microscopy (SEM), differential scanning calorimetry (DSC), thermogravimetric analysis, and conductivity measurements. The observed conductivities of the PDMS composites were 2.2–5.2 S/cm. The conductivity of Pth did not change appreciably with the addition of up to 30% insulating PDMS, but its processability improved. FTIR, SEM, and DSC studies showed the existence of a strong interaction, rather than physical adhesion, between PDMS and Pth. Highly flexible and foldable PDMS–Pth composites were obtained. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 87: 2113–2119, 2003