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The mode of preparation of silicones, their use and typical performances are reviewed. Particular attention is given to their use as sealants and structural adhesives in construction and building applications where adherence properties for assembling two substrates are important. An important part of this paper has been previously published ten yea...
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Context 1
... effect of adding non-reactive plasticiser, which is typically 100-1000 mPa s viscosity trimethylsilyl-terminated PDMS, is actually reducing the modulus and hardness of the sealant. Overall, a silicone sealant formulation may contain up to 10 components as described in Table 2. ...Context 2
... all 1-RTV and 2-RTV silicone sealants and/ or adhesives can be divided into three classes: acid, neutral and alkaline, depending on the chemical byproduct that is released during the curing process of the sealant (see Table 2). Of all these cure systems, 1-RTV acetoxy, or acetic acid system is without any doubt the most widely used. ...Context 3
... effect of adding non-reactive plasticiser, which is typically 100-1000 mPa s viscosity trimethylsilyl-terminated PDMS, is actually reducing the modulus and hardness of the sealant. Overall, a silicone sealant formulation may contain up to 10 components as described in Table 2. ...Context 4
... all 1-RTV and 2-RTV silicone sealants and/ or adhesives can be divided into three classes: acid, neutral and alkaline, depending on the chemical byproduct that is released during the curing process of the sealant (see Table 2). Of all these cure systems, 1-RTV acetoxy, or acetic acid system is without any doubt the most widely used. ...Citations
... Polydimethylsiloxane (PDMS) is an inorganic polymer widely used across various industries due to its remarkable properties, including chemical inertness, thermal stability, and flexibility [1][2][3][4][5][6]. These attributes make PDMS a favored material in fields such as aerospace, automotive, and medical devices [7][8][9]. ...
... high molecular weight polydimethylsiloxane (HMW-PDMS) and 30 wt.% dimethyldichlorosilane-treated silica (surface area: 125 m²/g, Gelest, Inc., Morrisville, PA, USA). The boron (B, 140 mesh, 2.3 g/cm 3 ) and hollow glass microballoon (HGM, commercial name 3M™ Glass Bubble S32HS; mean size of 25 µm, 0.32 g/cm 3 ) were purchased from 3M Company, St. Paul, MN, USA. The tungsten-coated hollow glass microballoon (WHGM, mean size of 25 µm, 0.87 g/cm 3 ) was prepared using a DC sputtering system (Model VTC-16-PW, MTI Corporation, Richmond, CA, USA) with in-chamber powered agitation provided by a vibration motor mounted to the powder reservoir. ...
... The boron (B, 140 mesh, 2.3 g/cm 3 ) and hollow glass microballoon (HGM, commercial name 3M™ Glass Bubble S32HS; mean size of 25 µm, 0.32 g/cm 3 ) were purchased from 3M Company, St. Paul, MN, USA. The tungsten-coated hollow glass microballoon (WHGM, mean size of 25 µm, 0.87 g/cm 3 ) was prepared using a DC sputtering system (Model VTC-16-PW, MTI Corporation, Richmond, CA, USA) with in-chamber powered agitation provided by a vibration motor mounted to the powder reservoir. For each powder coating run, 2.6 g of HGM S32HS were loaded into the powder reservoir, and a 2" diameter circular tungsten target was installed in the sputter source. ...
Polydimethylsiloxane (PDMS) is known for its exceptional mechanical properties, chemical stability, and flexibility. Recent advancements have focused on developing functional PDMS composites by integrating various functional fillers, including polymers, ceramics, and metals, for advanced applications such as electronics, medical devices, and aerospace. Consequently, there is a growing need to investigate PDMS composites to achieve higher filler loadings offering enhanced mechanical performance. This study addresses this need by utilizing the high molecular weight (MW) PDMS resin we have developed, offering its high elongation capacity of up to >6500%. We incorporated boron (B), hollow glass microballoons (HGMs), and tungsten-coated hollow glass microballoons (WHGMs) into the developed high MW PDMS. The resulting composites demonstrated excellent elastic properties and significant compression resilience (35–80%) and elastic modulus (1.28–10.15 MPa) at high filler loadings (~60 vol.%). Specifically, B/PDMS composites achieved up to 67.6 vol.% of B, HGM/PDMS composites held up to 68.6 vol.% of HGM, and WHGM/PDMS composites incorporated up to 54.0 vol.% of WHGM. These findings highlight the potential of high MW PDMS for developing high-performance PDMS composites suitable for advanced applications such as aerospace, automotive, and medical devices.
... In addition, thermallyconductive grades can be used to bond microprocessors, LED (light emitting diode) arrays, and other heat generating components to heat sinks, ensuring an efficient path for heat transfer. Flexible silicone elastomeric coatings can be applied in a thicker layer than their epoxy counterparts providing an even higher levels of protection resistant to heat and moisture [4][5][6][7]. ...
This paper investigates the effects of three ageing factors (chemical, humidity, and temperature) and their interactions on the physical properties and degradation of silicone sealant used in microelectronic applications. The thermal degradation of silicone sealants was investigated by exposing samples to temperatures in the range of 150 up to 175 °C. Also, a set of samples were aged at 40 °C in a salt spray set-up with 100 % humidity in a salty atmosphere. Results showed detectable changes in the FTIR spectra of aged specimen as compared with the as-received sample. In all accelerated testing conditions, peak intensities decreased with ageing time, inferring that that the surface characteristics of the sealant is affected by ageing. Shear test results showed that with increasing the ageing time, the maximum shear stress in most cases has decreased in all ageing conditions. Also, it appears that samples with longer ageing times have experienced more elongation before failure. Results also show that salt spraying of specimens is associated with a decrease in the mechanical properties of the sealant, indicating the deleterious implications of ionic contaminations for the mechanical properties of samples.
... This adhesive strength is comparable to commercially available silicone adhesives. 63 Here, dynamic covalent exchange at two interfaces creates a strong adhesive bond. After failure, a cohesive failure mode is observed where the adhering interfaces do not fail, but instead, the siloxane material fails. ...
We show that dynamic covalent exchange at the interface of two thermosetting polymers results in strong bonding between the materials via creation of a new material at the interface. Thus, polymers of significantly different polarities can be bonded without the use of adhesives. We also show that such dynamic covalent exchange is not only limited to the interface but also penetrates into the bulk material (ca. 20 microns), thereby creating a strong bond. The creation of a new material at the interface was confirmed by Energy Dispersive X-ray (EDX) elemental mapping as well as a new glass transition temperature at the interface. Using this phenomenon, we show that hydrophobic, compliant polymers can also be used as adhesives for polar, stiff materials. We also show that such dynamic exchange also takes place in the presence of fillers like nano-silica. Lastly, using this technique, we demonstrate the adhesive-less fabrication of layered materials where each layer has vastly different polarities and mechanical properties, thereby tuning the failures modes of the resulting composite material.
... Consequently, the Si-O bond has a partially ionic character, and the O atom is less basic than in the C-O bond [29,[47][48][49]. Additionally, the Si-O bond demonstrates a higher bond energy (433-460 kJ mol −1 ) compared to the C-O bond (345 kJ mol −1 ) [46,50,51]. The strong Si-O bond contributes to the chemical and thermal stability of siloxanes, while the large Si−O−Si bond angle facilitates conformational interconversion, reducing surface tension compared to organic polymers [51,52]. ...
Molecularly imprinted polymers (MIPs) are defined as artificial receptors due to their selectivity and specificity. Their advantageous properties compared to biological alternatives have sparked interest among scientists, as detailed in numerous review papers. Currently, there is significant attention on adhering to the principles of green chemistry and environmental protection. In this context, MIP research groups have focused on developing eco-friendly procedures. The application of “greener” monomers and reagents, along with the utilization of computational methodologies for design and property analysis, are two activities that align with the green chemistry principles for molecularly imprinted technology. This review discusses the application of computational methodologies in the preparation of MIPs based on eco-friendly non-acrylic/vinylic monomers and precursors, such as alkoxysilanes, ionic liquids, deep eutectic solvents, bio-based molecules—specifically saccharides, and biomolecules like proteins. It provides a brief introduction to MIP materials, the green aspects of MIP production, and the application of computational simulations. Following this, brief descriptions of the studied monomers, molecular simulation studies of green monomer-based MIPs, and computational strategies are presented. Finally, conclusions and an outlook on the future directions of computational analysis in the production of green imprinted materials are pointed out. To the best of my knowledge, this work is the first to combine these two aspects of MIP green chemistry principles.
... In one-part systems, the compounds cure from the surface inward [39]. The most commonly used reaction mixtures consist of hydroxy-endblocked-polydimethylsiloxane and a large excess of methyltriacetoxysilane [47]. The scheme of this process is presented in Fig. 5a. ...
... The by-product of the reaction is acetic acid, which has corrosive properties. To reduce the amount of harmful by-products released or completely eliminate them, other RTV-1 systems have been developed, in which, for example, tetraethylthosilicate (TEOS) [48],tetraalkoxy silane [49], or oximosilane [47] are used as cross-linking agents. ...
... In two-part systems, the compounds cure uniformly. An example of such a mixture is a hydroxyl-end-capped polydimethylsiloxane and an alkoxysilane, such as tetra n-propoxysilane, Si(OnPr) 4 (Fig. 5b) [47]. ...
The increasing range of applications of silicone material requires improvements in their properties to withstand rigorous conditions. Clay minerals are attractive reinforcement nanofillers that are used in polymer matrices. They improve numerous properties of the obtained clay-polymer nanocomposites (CPNs). This work is the first review devoted to CPNs in which the polymer matrix is polysiloxanes. The incorporation of clay minerals into polysiloxanes is considered to be an exciting route for creating new and innovative nanocomposites with improved performance properties that can meet the growing demand for advanced materials used in various industries. This review describes how different clay minerals, both natural and synthetic, have been introduced into polysiloxane systems. The characteristics of the obtained nanocomposites, their properties, and the possibilities of their application are discussed. Basic information on polysiloxanes and their applications, methods of cross-linking polysiloxanes, and classification of clay minerals, as well as basic methods of modifying clay minerals used in polysiloxane matrices, were discussed.
... 8,9 Typical structural adhesives are epoxy, 10−14 acrylic, 15−17 urethane-based adhesives, 18,19 and so on. 20,21 In particular, epoxy adhesives have been the most widely used due to their excellent mechanical strength and durability. 11,12 Recent attention has also been focused on reducing greenhouse gas emissions, such as carbon dioxide, through materials research and development. ...
Structural adhesives are currently applied in the assembly of automobiles, aircraft, and buildings. In particular, epoxy adhesives are widely used due to their excellent mechanical strength and durability. However, cured epoxy resins are typically rigid and inflexible; thus, they have low peel and impact strength. In this study, tough cured epoxy adhesives were developed by mixing a liquid epoxy prepolymer (EP) and polystyrene-b-polyisoprene-b-polystyrene (SIS). SIS is a block polymer-based thermoplastic elastomer (TPE) composed of polystyrene (S) soluble in liquid EP and polyisoprene (I) insoluble in liquid EP, where S and I have a glass transition temperature that is higher and lower than room temperature, respectively. In addition, cured adhesives tougher than the cured adhesives containing SIS were prepared by mixing liquid EP and SIS with hydrogen-bonding groups in the I block (h-SIS). Transmission electron microscopy (TEM) observations revealed mixed S/cured EP domains, with a d-spacing of several tens of nanometers, and cured EP domains, with diameters of one hundred to several hundred nanometers, that were macroscopically dispersed in the I or hydrogen-bonded I matrix of the cured adhesive containing SIS or h-SIS. The lap shear, peel, and impact strength of cured neat EP (EP*) were 23 MPa, 45 N/25 mm, and 0.62 kN/m, respectively. Meanwhile, the cured adhesive containing 16.5 wt % SIS exhibited the slightly lower lap shear strength of 17 MPa compared to that of cured EP*, whereas the peel and impact strength of the cured adhesive with SIS were 61 N/25 mm and 7.1 kN/m, respectively, both higher than those of EP*. Furthermore, the lap shear strength of the cured adhesive containing 15.5 wt % h-SIS was 21 MPa, which was similar to that of cured EP*. The cured adhesive with h-SIS also exhibited an excellent peel strength of 97 N/25 mm and an impact strength of 14 kN/m which was 22 times higher than that of cured EP*. Therefore, mixing liquid EP and SIS improved the cured adhesive properties and flexibility of the cured epoxy adhesives compared to the cured adhesive composed of neat EP, and further enhancement of the adhesive properties was achieved by mixing liquid EP and h-SIS with hydrogen-bonding groups instead of mixing with SIS.
... compounds are employed in membranes and filters to improve the efficiency of separating hydrocarbons from water; it is also used to remove oxygen from water in petroleum processes [6]. In the adhesives and sealants industry, silicon's flexibility and chemical resistance make it ideal for applications that require long-lasting bonds, such as in construction materials [7]. The most common methods to prepare polyarganosiloxanes are condensation polymerization and addition polymerization. ...
The deoxygenation process in water used in well injection operations is an important matter to eliminate corrosion in the petroleum industry. This study used molecular dynamics simulations to understand the behavior of siloxane surfaces by studying the surface properties with two functional groups attached to the end of siloxane and their effect on the deoxygenation process. The simulations were performed using LAMMPS to characterize surface properties. Jmol software version 14 was used to generate siloxane chains with (8, 20, and 35) repeat units. We evaluated properties such as total energy, surface tension, and viscosity. Then, we used siloxane as a membrane to compare the efficiency of deoxygenation for both types of functional groups. The results indicated that longer chain lengths increased the total energy and viscosity while decreasing surface tension. Replacing methyl groups with trifluoromethyl (CF3) groups increased all the above mentioned properties in varying proportions. Trifluoromethyl (CF3) groups showed better removal efficiency than methyl (CH3) groups but allowed more water to pass. Furthermore, the simulations were run using the class II potential developed by Sun, Rigby, and others within an explicit-atom (EA) model. This force field is universally applicable to the atomistic simulation of polymers, inorganic small molecules, and common organic molecules.
... Silicone materials possess an impressive range of advantageous properties, including electrical insulation, chemical stability, weatherability, and tolerance to extreme temperatures, owing in part to the unique chemistry of the characteristic Si-O bond [1][2][3]. These physiologically inert materials have medical and food processing applications due to their low toxicity and are widely used in electrical, construction, aerospace, automotive, and release coatings industries [1][2][3][4]. ...
... Silicone materials possess an impressive range of advantageous properties, including electrical insulation, chemical stability, weatherability, and tolerance to extreme temperatures, owing in part to the unique chemistry of the characteristic Si-O bond [1][2][3]. These physiologically inert materials have medical and food processing applications due to their low toxicity and are widely used in electrical, construction, aerospace, automotive, and release coatings industries [1][2][3][4]. The curing of silicone polymers can be accomplished by a high-temperature reaction involving the addition of a silane across an olefin known as hydrosilation. ...
UV-activated catalytic hydrosilation is a low-temperature crosslinking process that has attracted attention for its high efficiency and lower energy demand relative to thermal curing. In this study, formulations comprising industrially relevant model silanes and Pt photocatalysts trimethyl(methylcyclopentadienyl)platinum(IV) and trimethyl(pentamethylcyclopentadienyl)platinum(IV) (MeCpPtMe3 and Cp*PtMe3, respectively) were prepared with and without a photosensitizer (PS) and assessed for catalytic performance by a novel strategy. Photopolymerizations were initiated using different wavelengths from LEDs and monitored in real-time using an Attenuated Total Reflectance-Fourier Transform Infrared (ATR-FTIR) “well” strategy to track the degree of cure in ultra-thin films by consumption of hydride via the disappearance of the Si-H bending absorption band at 915 cm−1. Irradiation of formulations with 365 nm excitation showed higher conversions relative to 400 nm light and improvements to calculated initial reaction rates by incorporation of a PS suggested increased sensitization to 365 nm irradiation. To the best of our knowledge, this is the first study to report catalytic performance, electronic absorption spectroscopic data, and the crystal structure of Cp*PtMe3.
... 18 Concerning the water penetration, silicone rubber exhibits minimal water absorption (only 1%) even after prolonged exposure without compromis- ing mechanical or electrical properties. 19 Incorporating silanes into epoxy novolac networks enhances hydrophobicity and reduces water penetration. 20 Although water still penetrated the structures, the water fraction within the silane-epoxy network, compared to the neat epoxy novolac, was crucially reduced. ...
In the context of high-pressure, high-temperature (HPHT) conditions resembling those in the oil and gas industry, the performance of epoxy-siloxane hybrid coatings is investigated. Neat amine-cured epoxy novolac (EN) coatings exhibit drawbacks under these conditions, including softening upon exposure to hydrocarbons, leading to underfilm corrosion triggered by CO2 gas and seawater ion diffusion. To address these issues, two hybrid coatings, long-chain epoxy-terminated polydimethylsiloxane-modified EN (EN-EPDMS) and short-chain 3-glycidyloxypropyltrimethoxysilane-modified EN (EN-GPTMS), are assessed in HPHT environments. Both hybrids mitigate drawbacks observed in neat EN, with EN-GPTMS completely eliminating them due to the chemical inertness of inorganic siloxane networks. While EN-EPDMS exhibits a higher glass transition temperature than EN-GPTMS, it is susceptible to rapid gas decompression due to its lengthy and flexible siloxane backbone, resulting in unburst blisters. Conversely, EN-GPTMS demonstrates superior performance in HPHT environments, highlighting its potential for effective corrosion protection in harsh conditions encountered by the oil and gas industry.
... Polydimethylsiloxane (PDMS) based thin films are widely applicable in automotive, marine, spacecraft systems, building & construction, electronic, biomedical, power transmission, and consumer products owing to their transparency in UV range, low surface energy, chemical resistance, and long-term durability under adverse service and environmental conditions [1][2][3][4][5][6][7][8][9]. Specifically, microporous thin film adhesives made of PDMS with defined pore morphology and pore size distribution have huge application potentials in the fields of cell culture & tissue engineering, targeted drug deliveries, stretchable bioelectronics for medical devices, semi-permeable membranes for biogas & CO 2 detection and wound healing bandages [10][11][12][13][14][15][16][17]. ...
We developed novel porous composite Polydimethylsiloxane (PDMS) thin films using aqueous dispersions of cellulose microfibers (CMFs) derived from sugarcane bagasse. The rheological properties, adhesive performance, and reusability of these novel porous composite thin films were subsequently compared with neat PDMS thin films and correlated to the amount of CMF dispersion added and crosslinker concentration used during fabrication. The surface pore density, pore morphology, filler concentration, and crosslinker concentration governed the physicochemical, rheological, and adhesive properties of fabricated composite thin films. Porous composite thin films comprising 5% crosslinker with the least CMF dispersion addition showed superior adhesion strength and reusability among all fabricated porous composite Polydimethylsiloxane (PDMS) thin films.
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