Silicone-based Coatings Research Articles

Transparent and mechanically durable silicone/ZrO2 sol hybrid coating with enhanced antifouling properties

Achieving a delicate equilibrium between the mechanical and antifouling attributes of silicone-based coatings remains a formidable task. This research unveiled a novel approach to crafting a hybrid antifouling coating through the amalgamation of an amphiphilic telomer, Zirconia (ZrO2) sol, triethoxyoctylsilane (KH832) and tetraethyl orthosilicate (TEOS) using an uncomplicated sol–gel technique. The amphiphilic telomer, derived from a synthesized antibacterial acrylamide-benzothiazole small molecule, hydrophobic silanes/fluorosilanes, and hydrophilic monomers, was intricately tethered with the ZrO2 sol, synthesized through the hydrolysis of n-propyl zirconate. The resultant coating achieved exceptional transparency (>98 % transmittance), attributed to the covalent linkage between the robust zirconia structure and the pliable, long-chain telomer. This unique bonding imparted the coating with remarkable characteristics, including high hardness (4–6H), flexibility (∼5 mm bending diameter), wear resistance, and strong adhesion (∼2.89 MPa) to the substrate. Furthermore, the self-enrichment property of the non-leaching amphiphilic telomer within the hybrid matrix contributed to the coating’s outstanding self-cleaning capabilities, as well as its remarkable ability to resist fouling, including bacterial adhesion, protein attachment, diatom deposition, and biofilm formation. Overall, our research systematically explored the influence of composition and structure on both mechanical properties and antifouling performance. Ultimately, we sought to advance the development of a high-performance organic–inorganic hybrid antifouling coating poised to address the diverse requirements of applications spanning optical instruments, foldable displays, marine facilities, and various other fields.

Enhanced adhesive and mechanically robust silicone-based coating with excellent marine anti-fouling and anti-corrosion performances.

Poly(dimethylsiloxane) (PDMS) is widely used in marine antifouling coatings due to its low surface energy property. However, certain drawbacks of PDMS coatings such as poor surface adhesion, weak mechanical properties, and inadequate static antifouling performance have hindered its practical applications. Herein, condensation polymerization is utilized to prepare PDMS-based polythiamine ester (PTUBAF) coatings that consist of PDMS, polytetrahydrofuran (PTMG), 2, 3, 5, 6-tetrafluoro-1, 4-benzenedimethanol (TBD) as the main chains and isobornyl acrylate(IBA) as the antifouling group. The surface adhesion to the substrate is enhanced due to the hydrogen bond between the coated carbamate group and the hydroxyl group on the surface of the substrate. Mechanical properties of PTUBAF are significantly improved due to the benzene ring and six-membered ring biphase hard structure. The strong synergistic effect of bactericidal groups and low surface energy surface endows the PTUBAF coating with outstanding antifouling performance. Due to the low surface energy surface, the PTUBAF coatings are also found to possess excellent anti-corrosion. Furthermore, since the PTUBAF coatings exhibit a visible light transmittance of 91 %, they can applied as protective films for smartphones. The proposed method has the potential to boost the production and practical applications of silicone-based coatings.

Reactive Molecular Dynamics Study of the Mechanism and Effect of Various Protective Coatings on the Protection of Polyimide Antierosion from Atomic Oxygen.

Polyimide (PI), due to its exceptional performance, is commonly utilized in spacecraft. However, when such polymers are used in spacecraft navigating low Earth orbit, they are exposed to atomic oxygen (AO) that can cause the polymer to decompose. A protective coating method is a more effective way to safeguard the polymer from erosion caused by AO. This study employs the molecular dynamics simulation based on the reaction force field to investigate the protective effects of various coatings, including polydimethylsiloxane (PDMS), graphene (Gr), polytetrafluoroethylene (PTFE), and the (0 0 1), (0 1 1), and (1 1 1) surfaces of SiO2. The results indicate that the protective performance of the (0 1 1) surface is superior to that of the (0 0 1) and (1 1 1) surfaces. Moreover, protective coatings are classified into three categories based on different protective mechanisms: rebound, absorption, and sacrificial. The protective effectiveness of coatings depends on their anti-AO performance and ability to combine with the substrate. Gr displays exceptional anti-AO properties and can effectively shield the substrate from AO erosion. Silicone-based coatings have a superior ability to adhere to PI substrates, and PDMS is an excellent choice for protective coatings. This paper offers guidance for the protective coating method of PIs against AO erosion.

Silicone Resin Applications for Heat-Resistant Coatings: A Review

Silicone resins, which exhibits excellent heat-resistance, chemical stability and adhesion, are indispensable components in high temperature resistance coatings. Herein, we summarize a comprehensive survey of developments on heat-resistant silicone-based coatings. The influence of heat-resistant of modifying silicone resin chain segment, such as main chain modification and side main modification are discussed. Then, the physical and chemical properties of inorganic fillers combined with silicone resins are summarized for the aim of ceramization and further improving the degree of heat-resistant. Finally, the challenges and future opportunities of heat resistance coatings based on silicone resins are considered.

Dynamic migration mechanism of borneol synergistic polyethylene glycol for the construction of silicon-acrylate antifouling coating

Silicone-based coatings are vulnerable to marine fouling organisms in static environments, which seriously hampers its practical application. Here, an amphiphilic acrylate polymer is designed by hydrophilic polyethylene glycol and antibacterial borneol, which is introduced into polydimethylsiloxane (PDMS) by covalent linking to prepare antifouling coatings. XPS and CA tests prove that amphiphilic acrylate polymer can migrate to coating surface in the marine environment to maximize antifouling properties. Mytilus edulis foot protein adhesion test find it can weaken interface force between Mefp-3 and surface. Laboratory antifouling performance evaluations confirm that the coatings are effective against the adhesion of bacteria (86.72 % reduction for E. coli), diatoms (87.76 % reduction for Nitzschia closterium). The good antifouling properties of coatings are ascribed to the synergistic effect among unique bicyclic monoterpene structure of natural non-toxic borneol and amphiphilic acrylate polymer on surface of coatings. Moreover, the coating is less harmful to the marine ecological balance than traditional coatings containing toxic biocides due to the introduction of natural non-toxic borneol. This work contributes new insights in the exploration of environmentally friendly coating with excellent static antifouling performance.

Capsaicin-based silicone antifouling coating with enhanced interlocking adhesion via SIPN

Silicone-based coatings generally exhibit excellent dynamic fouling release due to their low surface energy and elastic modulus. However, the poor adhesion of these coatings at the interface between the coating and the substrate, as well as deficient static antifouling capabilities, severely deteriorate their antifouling properties over extended periods. Herein, an epoxy-poly(dimethylsiloxane)/capsaicin (EP-PDMS/CAP) coating with highly enhanced interfacial adhesion and remarkable antifouling performances was prepared. The coating adhesion strength of the EP-PDMS/CAP has been improved by more than 5 times compared to a PDMS control coating (from 0.4 MPa to 2.04 MPa) by forming a semi-interpenetrating polymer network (SIPN) structure between the epoxy and PDMS layers. The EP-PDMS/CAP coating achieved the superior antifouling effects in both static and dynamic conditions, the anti-bacterial rate was as high as 96.8 %, and the anti-algal adhesion rate to the green algae Chlorella increased by 95.7 %, due to the synergistic effects of the fouling release performance from the PDMS coating and the fouling prevention of capsaicin. Furthermore, the EP-PDMS/CAP coating was proven to be extremely stable in different treatments such as acid/basic solutions, air oven heating test, and cyclic sand abrasion, showing great potential for anti-biofouling under aggressive conditions. This work provides a promising pathway towards the development of high-performance silicone-based composite coatings for efficient marine anti-biofouling.

Synthesis of Three Novel Silane-Based Carboxylic Acids for Application in Methacrylated Epoxy-Based Oligomers and Their Ability to Improve the Properties of UV Curable Hybrid Coatings

Improvement of thermal stability of silicone-based coatings was the main objective of this study. In this study bromoacetic acid (BAA) was reacted with 3-(mercaptopropyl) trimethoxy silane (MPTS) and trimethoxy silyl propyl thioacetic acid (TSTA) was produced. Also, bromoacetic acid (BAA) was reacted with 3-(triethoxysilyl) propylamine (APTS) and triethoxysilyl propylamino acetic acid (TSPA) was synthesized. Finally, from a reaction between trimellitic anhydride (TMA) and APTS, trimellitylimidopropyl triethoxysilane (TMIS) resulted. Compounds containing carboxylic acids and trimethyl silane were obtained in all of these reactions. Furthermore, hybrid coatings based on methacrylated bisphenol A epoxy (MBAE) and the synthesized carboxylic acids were obtained by photopolymerization. Polycarbonate substrates were utilized for preparation of the transparent hybrid films. Then the solvent resistance, hardness and gel content, as well as the adhesion of the coatings, were measured as physical and mechanical properties. According to the obtained results, these properties of the hybrid coatings were improved with the increase in alkoxysilanes and sol–gel precursor contents. The surface morphology was characterized by scanning electron microscopy (SEM). The results showed that silica particles were not dispersed homogenously at the molecular level in the hybrid system. Also, the thermogravimetric analysis results indicated that alkoxysilanes enhanced the thermal oxidative stability of the hybrid coatings.

Silicone-Based Lubricant-Infused Slippery Coating Covalently Bound to Aluminum Substrates for Underwater Applications.

Wetting of solid surfaces is crucial for biological and industrial processes but is also associated with several harmful phenomena such as biofouling and corrosion that limit the effectiveness of various technologies in aquatic environments. Despite extensive research, these challenges remain critical today. Recently, we have developed a facile UV-grafting technique to covalently attach silicone-based coatings to solid substrates. In this study, the grafting process was evaluated as a function of UV exposure time on aluminum substrates. While short-time exposure to UV light results in the formation of lubricant-infused slippery surfaces (LISS), a flat, nonporous variant of slippery liquid-infused porous surfaces, longer exposure leads to the formation of semi-rigid cross-linked polydimethylsiloxane (PDMS) coatings, both covalently bound to the substrate. These coatings were exposed to aquatic media to evaluate their resistance to corrosion and biofouling. While the UV-grafted cross-linked PDMS coating effectively inhibits aluminum corrosion in aquatic environments and allows organisms to grow on the surface, the LISS coating demonstrates improved corrosion resistance but inhibits biofilm adhesion. The synergy between facile and low-cost fabrication, rapid binding kinetics, eco-friendliness, and nontoxicity of the applied materials to aquatic life combined with excellent wetting-repellent characteristics make this technology applicable for implementation in aquatic environments.

Facile fabrication of self-healing silicone-based poly(urea-thiourea)/tannic acid composite for anti-biofouling

• A novel composite of silicone-based poly(urea-thiourea) and tannic acid is prepared by a facile method. • The composite presents a tough and highly stretchable performance. • The composite exhibits a fast self-healing property at room temperature in both air and artificial sea water. • The coating based on the composite shows a strong adhesion strength to substrates. • The coating exhibits a good antibacterial property and favorable anti-diatom performance. A novel silicone-based poly(urea-thiourea)/tannic acid composite (PDMS-P(Ua-TUa)-TA) with excellent mechanical, self-healing and antifouling properties is developed. The multiple dynamic hydrogen bonds formed by thiourea groups, urea groups, and tannic acid (TA) molecules ensured a tough elastomer (ultimate strength: 2.47 MPa) with high stretchability (∼1000%). TA molecules as partial hydrogen bonding cross-linking sites interacted rapidly with urea and thiourea groups before the migration of polymer chains, resulting in fast and efficient self-healing. Scratches on the film completely disappeared within 12 min, and the repair efficiency of strength was up to 98.4% within 3 h under ambient condition. Self-healing behavior was also evaluated in artificial seawater and the healing efficiency (HE) was 95.1%. Furthermore, TA uniformly dispersed in the polymer matrix provides good antibacterial and anti-diatom properties, as well as strong adhesion to the substrate (∼2.2 MPa). Laboratory bioassays against marine bacteria adhesion (∼96%, ∼95% and ∼93% reduction for P. sp., E. coli , and S. aureus , respectively) and diatom attachment (∼84% reduction) demonstrated an outstanding antifouling property of the PDMS-P(Ua-TUa)-TA. This work provides a promising pathway towards the development of high-performance silicone-based coatings for marine anti-biofouling.

Thermoresponsive Hybrid Colloidal Capsules as an Inorganic Additive for Fire-Resistant Silicone-Based Coatings

Improving the fire-resistant efficiency of silicone-based polymeric coatings is important in the building industry and electrical utilities. In this study, the water-containing hybrid calcium carbonate (CaCO3)–silica (SiO2) colloidal capsule has been developed and optimized as an inorganic flame-retardant additive. This capsule exhibits excellent thermal stability up to 1000 °C with a remaining intact hollow spherical structure. When used as an inorganic filler at 15 wt %, it not only reduces the potential fire hazards by over 44% (i.e., the sumHRC reduced from 112.00 J/g K to 62.00 J/g K) but also improves the heat-barrier efficiency by over 30% (i.e., the temperature at the steady state reduced from 350 to 360 °C to below 250 °C) of the silicone-based polymeric coatings. In addition, the capsule–polymer composite coating exhibits excellent ductility which can withstand heat-induced mechanical stresses and prevent crack propagation under radiative heating conditions. The fire-resistant mechanism of the colloidal capsule is related strongly to the encapsulated water core and the reactions between SiO2 and CaCO3 at elevated temperatures. They not only contribute to a cooling effect on the flammable pyrolysis gases but also induce the insulative effect to the resulted char during combustion. The significant advances in this study will have a high impact in customizing the functional inorganic additives for a better design of the flame-retardant composite coating.

Cu@C core-shell nanoparticles modified polydimethylsiloxane -based coatings with improved static antifouling performance

PDMS-based fouling release coatings have promising applications in the fields of marine fouling control. However, development of silicone-based coatings with good antifouling / fouling-release property under relative static conditions remains challenging. In this work, a new PDMS-based nanocomposite coating consisting of PDMS matrix and nanofiller of copper@carbon core-shell nanoparticles was developed. Uniformly dispersed Cu@C core-shell in the PDMS matrix enhance the antifouling ability. The PDMS with low surface energy endows the composite coatings with hydrophobicity thus fouling release property. The introduction of Cu@C core-shell/PDMS improves both the Young's modulus, tensile strength and the elongation at break. Furthermore, laboratory bioassay against diatom adhesion and field tests indicated that the PDMS-based nanocomposite coatings with Cu@C core-shell exhibited outstanding antifouling / fouling-release property even under static conditions, showing promising application in marine antifouling.

A Multi-Tool Analysis to Assess the Effectiveness of Passive Ice Protection Materials to Assist Rotorcraft Manual De-Icing

Search and rescue missions using rotorcrafts need to be reliable all year long, even in winter conditions. In some cases of deployment prior to take off, the crew may need to manually remove accumulated contaminant from the critical surfaces using tools at their disposal. However, icy contaminant may be hard to remove since the rotorcrafts critical surfaces could be cooler than the environment, thus promoting adhesion. Currently, there exists several passive ice protection materials that could reduce the ice adhesion strength and assist the manual de-icing. The aim of this paper is to propose a detailed comparative procedure to assess the ability of materials to assist the manual de-icing of rotorcrafts. The proposed procedure consists of the characterization of materials using several laboratory tests in order to determine their characteristics pertaining to wettability, their icephobic behavior, and finally their assessment under a multi-tool analysis to evaluate if they can assist. The multi-tool analysis uses different mechanical tools, which are currently used during normal operation, to execute a gradual de-icing procedure, which begins with the softest to the hardest tool using a constant number of passes or strokes, under different types of simulated precipitation. Five different materials were used to evaluate the proposed procedure: Aluminum (used as a reference), two silicone-based coatings (Nusil and SurfEllent), an epoxy-based coating (Wearlon), and finally a commercial ski wax (Swix). All of the tested materials could assist the manual de-icing, within a certain limit, when compared to the bare aluminum. However, SurfEllent was the material that obtained the best overall results. This procedure could be easily adapted to different fields of application and could be used as a development tool for the optimization and the assessment of new materials aimed to reduce ice adhesion.

실리콘 타입 방오 도료의 해양 침지에 의한 방오 성능 평가 및 해수 침식(Erosion)에 의한 신뢰성 평가 연구

실리콘 타입 방오 도료의 해양 침지에 의한 방오 성능 평가 및 해수 침식(Erosion)에 의한 신뢰성 평가 연구

Preliminary Studies on Distribution of Marine Fouling Hydroids <i>Ectopleura</i> and on Laboratory-based Actinula Larval Settlement Assays

Only a few studies have been devoted to the species identification and the distribution of marine hydroids Ectopleura in Japanese coastal waters, despite the scale of fouling problems that they pose. We collected polyps from the coast of the western and northern parts of Japan, and analyzed their morphological characters and mitochondrial COI genes. As a result, while polyps settled on fishing nets along the coast of Hokkaido were Ectopleura radiata, E. crocea were spotted along the Pacific coast of Honshu. Dense polyp colonies on pontoons along the coasts of Seto Inland Sea in mid-to-late winter were also identified for the first time as E. radiata. In addition, phylogenetic analysis has identified Ectopleura sp. JRH-2014 spotted in the China Seas as E. radiata. Regarding actinulae of E. radiata, we devised a new assay composed of hexagonal columnar cell using test slide glasses, and a magnetic stirrer, and examined the settlement inhibitory effects of the silicone-based coatings. The results found that actinulae proved very sensitive to copper pyrithione contained in anti-fouling agents and the age of coatings.

Bio-based coatings with liquid repellency for various applications

In this work, a novel bio-based liquid-repellent coating system was first developed by using 2-mercaptoethanol-modified castor oil (COME) as a coating precursor, polydimethylsiloxane (PDMS) as a liquid-repellent agent, and hexamethoxymethylmelamine (HMMM) as a curing agent. The resultant coatings demonstrate exceptional liquid repellency, and they exhibit striking anti-ink ability and self-cleaning performance. Besides, these bio-based coatings show remarkable repellency against water-borne and oil-borne paints as well as fingerprint liquid, indicating that they can potentially be used for anti-graffiti and anti-fingerprint purposes. Furthermore, due to their remarkable resistance against various corrosive agents, they can be employed to protect substrates against harsh chemical conditions. More strikingly, these coatings can be dyed into various colors without compromising their liquid repellency. Compared with commercial fluorinated amphiphobic coatings, silicone-based coatings, and Never Wet superhydrophobic coatings, these fluoride-free bio-based coatings show incomparable advantages in terms of liquid-repellent performances and application foreground. It is noteworthy that, they are able to maintain liquid repellency even after being subjected to 5000 abrasion cycles, indicative of their remarkable mechanical robustness. Therefore, these newly developed bio-based liquid-repellent coatings are promising for widespread applications.

Effects of PEG-TMS on the stability and antifouling performances of hydrocarbon-modified amphiphilic xerogel coatings

Amphiphilic xerogel films with slight swelling were prepared by the acid-catalysed sol-gel method starting from tetraethoxysilane (TEOS), triethoxyoctylsilane (C8Si), n-octadecyl trimethoxysilane (C18Si) and poly(ethylene glycol) siloxane (PEG-TMS). In these amphiphilic xerogel films, the presence of hydrophobic chains, especially C18Si facilitated the emigration of PEG chain to the coating/air interface during the film formation/curing process, and then the PEG chains enriched at the surface of coatings further slightly emigrated to form hydration layer underwater confirmed by energy dispersive X-ray spectroscopic (EDS) analysis, captive air-bubble contact angle (CA) and CA hysteresis. Furthermore, the amphiphilic xerogel films showed the optimal water absorption ratio lower than 1.0% due to the restraint of higher crosslinked density and little network aperture of the films on PEG chains. The antifouling performances of amphiphilic xerogel films included the protein resistance for FITC-BSA, antibacterial property for Escherichia coli and the resistance for diatom Navicula, were better than those of the elastic silicone-based coatings and xerogel film without hydrophilic PEG chains. In general, the amphiphilic xerogel films containing both PEG and proper levels of C8Si and C18Si possessed excellent fouling release properties and slight swelling due to the synergistic effects.

Hydrocarbon time–temperature curve under airjet perturbation: An in situ method to probe char stability and integrity in reactive fire protection coatings

Intumescent coatings are the present-day state-of-art techniques to protect steel structures and other structural materials from fire hazards. Thermal insulation properties of such protective materials are normally deduced from standard fire tests, however, with least reference to char integrity and strength. This work proposes a simple and resourceful in situ experimental protocol to evaluate char strength of intumescent coatings on steel panels during hydrocarbon time–temperature fire test (at about 1200°C). It is based on in-process monitoring the physical integrity, mechanical stability, and thermal insulation capacity of fully developed char under a stream of air (airjet) before steel plate reaches its critical temperature. A bench-scale furnace designed in our laboratory to reproduce hydrocarbon fire scenario (UL1709) was upgraded to simulate air turbulence to impact the char strength. Silicone- and epoxy-based coatings on steel panels were tested under these conditions. Silicone-based coatings are found to have several interesting advantages over the latter. Furthermore, this protocol was extended to investigate the compositional influence on char strength in a set of silicon-based coatings.

Effect of anti-biofouling potential of multi-walled carbon nanotubes-filled polydimethylsiloxane composites on pioneer microbial colonization

In this paper, two carbon nanotube (CNT) nanofillers, namely the multi-walled carbon nanotubes (MWCNTs) and the carboxyl-modified MWCNTs (cMWCNTs), were introduced into the polydimethylsiloxane (PDMS) matrix respectively, in order to produce the PDMS composites with reinforced anti-biofouling properties. The anti-biofouling capacity of the silicone-based coatings, including the unfilled PDMS (P0), the MWCNTs-filled PDMS (PM) and the cMWCNTs-filled PDMS (PC), was examined via the field assays conducted in Weihai, China. The effect of different silicone-based coatings on the dynamic variations of the pioneer microbial-community diversity was analyzed using the single-strand conformation polymorphism (SSCP) technique. The PM and PC surfaces have exhibited excellent anti-biofouling properties in contrast to that of the PDMS surface, with extremely low attachment of the early colonizers, such as juvenile invertebrates, seaweeds and algae sporelings. The PM and PC surfaces can effectively prevent biofouling for more than 12 weeks. These combined results suggest that the incorporation of MWCNTs or cMWCNTs into the PDMS matrix can dramatically reinforce its anti-biofouling properties. The SSCP analysis reveals that compared with the PDMS surfaces, the PM and PC surfaces have strong modulating effect on the pioneer prokaryotic and eukaryotic communities, particularly on the colonization of pioneer eukaryotic microbes. The significantly reduced pioneer eukaryotic-community diversity may contribute to the weakening of the subsequent colonization of macrofoulers.

Metal-free anti-biofouling coatings: the preparation of silicone-based nanostructured coatings via purely organic catalysis

The successful formulation of two-part condensation-curing silicone materials via purely organic catalysis is here developed and investigated as fouling-release coating. Several non-toxic organic catalysts and their ‘onium’ salts were studied as potential purely organic catalysts on the silicone condensation reaction but also on the properties of the resulting cured resins. The trifluoroacetic acid was pointed suitable for the production of condensation-curing silicone coatings. To assess favorable fouling-release properties, multi-wall carbon nanotubes (0.05–0.2 wt-%) were added to the resin. Interestingly, the catalytic activity of the trifluoroacetic acid proved not affected by the presence of the nanocharge. The properties of the coatings prepared using 0.1 wt-% acid revealed constant degree of crosslinking independently of the carbon nanotubes loading and pronounced surface nanostructuring suitable for fouling release. This final property was tested against Ulva linza sporelings and revealed that the coatings are highly suitable for fouling-release applications.

Resistance to fire of silicone-based coatings: Fire protection of steel against cellulosic fire

The fire performance of curable silicone-based coatings containing expandable graphite, organoclay, and calcium carbonate is evaluated in cellulosic fire scenario (standard ISO834) using a lab-scale furnace test. It is shown that the use of organoclay and calcium carbonate allows achieving same insulative performance when compared with organic commercial intumescent coating. The mode of action of these silicone-based coatings is fully investigated using thermal analyses and spectroscopic analyses including X-ray photoelectron spectroscopy. It is shown that the high fire performance of intumescent silicone-based coatings is due to (1) interactions between calcium carbonate and silicone matrix increasing the thermal stability of the resin and (2) the formation of calcium silicate embedding the top of the char and permitting the formation of an additional protective ceramic layer.