Silicone-based Coatings Research Articles

Intumescent silicone-based coatings for the fire protection of carbon fiber reinforced composites

The application of carbon fiber reinforced polymer (CFRP) in aircraft structure has introduced potential fire threats and fire protection must be provided. In this paper, intumescent silicone based-coatings (low and high intumescing coatings) are evaluated on CFRP using a bench developed in the laboratory mimicking a jet fuel fire occurring at high heat flux (200 kW/m2). It is shown the development of large intumescence (high intumescing coating) associated with appropriate thermal properties of the coating (heat conductivity measured as low as 0.3 W/m.K) provides efficient protection for the CFRP at the jet fire test. On the other hand, the formation of cohesive ceramic (low intumescing coating) with low heat conductivity (constant heat conductivity as a function of temperature of 0.35 W/m.K) also provides protection but its efficiency is lower than that of intumescent char. It is evidenced that intumescent silicone-based coatings are materials of choice for protecting CFRP in the case of jet fuel fire.

Modification of the Adhesive Properties of Silicone-Based Coatings by Block Copolymers

The improvement of the (bio)adhesive properties of elastomeric polydimethylsiloxane (PDMS) coatings is reported. This is achieved by a surface modification consisting of the incorporation of block copolymers containing a PDMS block and a poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) block in a PDMS matrix, followed by matrix cross-linking and immersion of the obtained materials in water. Contact angle measurements (CA), X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM) showed the presence of the PDMAEMA block at the surface, drastic morphology changes, and improved adhesion properties after immersion in water. Finally, underwater bioadhesion tests show that mussels adhere only to block copolymer-filled coatings and after immersion in water, i.e., when the PDMAEMA blocks have been brought to the coating surface. These observations highlight the significant role of hydrophilic groups in the surface modification of silicone coatings.

Progress in Ice-Phobic Coating

This paper summarizes the test method of ice-phobic coating adhesion strength and the progress in coating material. Ice adhesion strength of several commercial ice-phobic coatings were tested for Pratt & Whitney, and result indicated that reformative silicone R-2180 show significantly improved reduction in ice adhesion when compared to several different commercially available silicone-based ice-phobic coatings. It would be valuable in future studies to measure the surface energies of the several materials tested to determine any correlation between the ice adhesion and surface energy of the coating.

Silicone-based powder coatings

Silicone-based powder coatings

Determining the viscoelastic parameters of thin elastomer based materials using continuous microindentation

Depth-sensing indentation (DSI) was used to evaluate the viscoelastic properties of three proprietary silicone-based coatings and four butyl-based rubber sheets. The coatings are used as layers in silicone bilayer coatings. The elastic indentation modulus, E ∗, irrecoverable deformation energy and elastic energy were determined in an earlier study using the unloading data of DSI tests and applying a creep correction method proposed by Ngan et al. The model used in this study to characterize the coatings was the standard four parameter Maxwell–Voigt viscoelastic model combined with the elastic indentation load-depth model for a Berkovich indenter as proposed by Fischer-Cripps. This model fits the data quite well. The parameters E 1 ∗, E 2 ∗, η 1, and η 2 were found by curve fitting this model with the indentation depth versus time data while held at a constant maximum load. The parameter E 1 ∗ is equivalent to E ∗; values of E 1 ∗ obtained using the Fischer-Cripps technique were 6.8 ± 0.9 MPa, 109 ± 7 MPa, and 4.2 ± 0.5 MPa for bond coat A, bond coat B, and the top coat, respectively. One purpose of this paper is to demonstrate a technique to determine viscoelastic parameters of silicone-based elastomers. It is hoped that these parameters may then be used in the evaluation and development of more durable silicone-based foul release coatings. Another purpose is to apply this technique to other elastomer-based materials such as butyl-based rubbers.

Preparation and characterisation of silicone-based coatings filled with carbon nanotubes and natural sepiolite and their application as marine fouling-release coatings

This article reports on the preparation and partial characterisation of silicone-based coatings filled with low levels of either synthetic multiwall carbon nanotubes (MWCNTs) or natural sepiolite (NS). The antifouling and fouling-release properties of these coatings were explored through laboratory assays involving representative soft-fouling (Ulva) and hard-fouling (Balanus) organisms. The bulk mechanical properties of the coatings appeared unchanged by the addition of low amounts of filler, in contrast to the surface properties, which were modified on exposure to water. The release of Ulva sporelings (young plants) was improved by the addition of low amounts of both NS and MWCNTs. The most profound effect recorded was the significant reduction of adhesion strength of adult barnacles growing on a silicone elastomer containing a small amount (0.05%) of MWCNTs. All the data indicate that independent of the bulk properties, the surface properties affect settlement, and more particularly, the fouling-release behaviour, of the filled materials.

Hazard assessment of silicone oils (polydimethylsiloxanes, PDMS) used in antifouling-/foul-release-products in the marine environment

Non-eroding silicone-based coatings can effectively reduce fouling of ship hulls and are an alternative to biocidal and heavy metal-based antifoulings. The products, whose formulations and make up are closely guarded proprietary knowledge, consist of a silicone resin matrix and may contain unbound silicone oils (1–10%). If these oils leach out, they can have impacts on marine environments: PDMS are persistent, adsorb to suspended particulate matter and may settle into sediment. If oil films build up on sediments, infiltration may inhibit pore water exchange. PDMS do not bioaccumulate in marine organisms and soluble fractions have low toxicity to aquatic and benthic organisms. At higher exposures, undissolved silicone oil films or droplets can cause physical–mechanic effects with trapping and suffocation of organisms. These ‘new’ effects are not covered by current assessment schemes. PDMS make the case that very low water solubility and bioavailability do not necessarily preclude damage to marine environments.

Biodegradation-based Polymer Surface Erosion and Surface Renewal for Foul-release at Low Ship Speeds

Non-toxic foul-release provides an environmentally friendly and sustainable technical solution to control micro- and/or macrofouling on ships' hulls. Silicone-based coatings have been used for foul-release at high or moderate ship speeds (>15 knots). To remove the fouling from slower ships (<15 knots), the macrofoulers in particular, biodegradable polymers may be used to make the coating surface self-renewable. Synthesized by microorganisms for carbon and energy storage under controlled conditions, polyhydroxyalkanoates (PHAs) are hydrophobic biopolymers that are gradually decomposed into CO 2 and water in the environment. Because of their hydrophobic property and lack of hydrolysis in sterile aqueous solution, PHAs do not dissolve in water, but erode at the polymer surface (2-5 w m in depth) catalyzed exclusively by microbial enzymes (depolymerases) that are attached on the solid surface. The thin-layer surface erosion behaves like a self-renewable surface coating, which approaches a constant renewal rate at a relative hydraulic speed as low as 3 knots. A turbulence eddy model is used to describe the effect of energy consumption per mass of liquid on the turbulent shear stress and the surface renewal rate. Furthermore, the polymer biodegradation or surface renewal rate can be controlled within a broad range by blending the material with polymers such as poly ( l -caprolactone) (PCL). The biodegradation of binary blends of PHA/PCL of different compositions was quantitatively monitored by means of weight loss and Raman spectroscopy.

発電所の汚損生物対策技術の展望

This paper reviews biofouling control procedures in Japanese power station cooling water systems. Antifouling paints and chlorination are widely used to prevent biofouling. Silicone-based coatings and self-polishing paints containing Cu2O are used commonly as antifouling coatings. Silicone-based paints are very effective under high water velocity. There are several kinds of cleaning and inspection robots to remove fouling organisms in intake culverts. Antifouling methods for condensers comprise online sponge ball cleaning, back wash, and self-cleaning debris filters. Electro-conductive paint and electrochemical methods are used in limited areas in cooling water systems. A robot has been developed for cleaning and inspection of condenser tubes.