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.

Among the various issues pertaining to the use of composite polymeric materials based on nanoparticles, the dispersion of the nanofillers in the matrix and the nature of the fillerpolymer interface are central. In many cases, poor dispersion results in agglomeration or phase separation, leading to a dramatic loss of the materials properties. To overcome this problem, a number of strategies have been developed with various degrees of success. They usually come at a high price, due to the necessity of modifying the surface state of the filler. Here, we report on novel carbon nanotubes-reinforced poly(dimethyl)siloxane nanocomposites and surprisingly, for which the use of "self pure" multiwall carbon nanotubes, i.e., without any surface functionalization or specific surface treatment, turns out to be the most efficient approach to impart new key-properties to the silicone matrix. Viscometric, rheological and theoretical studies have been performed that demonstrate the remarkable potential of dispersing a very tiny amount of "self pure" carbon nanotubes in silicone, paving the way to unexpected applications, e.g., in the field of fire endurance. Very interestingly, only tiny amounts of MWCNTs are required: usually less than 0.5 wt %. Those properties all rely on the nature of the nanotube-silicone interface interactions, which are dominated by additive CH-p interactions between the methyl groups of the polymer and the nanotube surface.Polydimethylsiloxane (PDMS) is the most common silicone elastomer owing to its ease of fabrication and advantageous chemical/physical properties, such as low surface energy, low glass transition temperature and high chain mobility.[1] Currently, to compensate for their poor mechanical properties, silicone materials have to be reinforced by incorporation of particulate materials, silica being the most commonly used filler. To date, the in situ filling process, where silica is generated into the elastomeric matrix, is the most efficient way to fill PDMS materials.[2] However, this reinforcement still requires a relatively high mass fraction of minerals (> 10 wt %).Over the past few years, much attention has been paid to polymer nanocomposites, which represent a rational alternative to conventional filled polymers, especially polymerlayered silicate nanocomposites. [3,4] In spite of their many potential applications, only a few reports have been published on polydimethylsiloxane nanocomposites. [5][6][7][8] The key-point for the improvement of properties as diverse as the mechanical, the thermal, and the barrier performances is the effective/ individual dispersion of the nanofillers in the matrix. To reach this objective, the type of nanofillers, their size and the nature of the interface formed within the matrix all have to be optimized. In this context, carbon nanotubes (CNTs) are of prime interest; however, they have a strong tendency to agglomerate in densely packed bundles, and their dispersion in polymers still remains a major challenge.Here we discuss first the spectacular change in...

The architecture of novel fluorinated copolymers drastically influences their stabilizing properties and their ability to template particle formation.

The present work reports on the influence of the dispersion quality of multiwall carbon nanotubes (MWCNTs) in a silicone matrix on the marine fouling-release performance of the resulting nanocomposite coatings. A first set of coatings filled with different nanofiller contents was prepared by the dilution of a silicone/MWCNTs masterbatch within a hydrosilylation-curing polydimethylsiloxane resin. The fouling-release properties of the nanocomposite coatings were studied through laboratory assays with the marine alga (seaweed) Ulva, a common fouling species. As reported previously (see Ref. [19]), the addition of a small (0.05%) amount of carbon nanotubes substantially improves the fouling-release properties of the silicone matrix. This paper shows that this improvement is dependent on the amount of filler, with a maximum obtained with 0.1 wt% of multiwall carbon nanotubes (MWCNTs). The method of dispersion of carbon nanotubes in the silicone matrix is also shown to significantly (p = 0.05) influence the fouling-release properties of the coatings. Dispersing 0.1% MWCNTs using the masterbatch approach yielded coatings with circa 40% improved fouling-release properties over those where MWCNTs were dispersed directly in the polymeric matrix. This improvement is directly related to the state of nanofiller dispersion within the cross-linked silicone coating.

Flax unidirectional (UD) fabrics and polyamide 11 (PA11) are used to create a 100% biosourced composite. The fabrication process is hot press moulding. Different configurations are studied by varying process parameters and composite constituents. Three temperature values (190 C, 200 C and 210 C) are combined with three pressure levels (35, 65 and 100 bars). In addition, two types of flax fabric (A and B) are tested and two types of PA11 (in the form of powder or film) are used. The two forms of PA11 are characterized using differential scanning calorimetry and rheological methods. Ten different composites are then manufactured. They are compared by means of tensile tests and dynamic mechanical analysis (DMA). Results are correlated with microstructural study: measurements of porosity degree and scanning electron microscopic observations are also performed. Finally, an optimum configuration is determined: the composite flax B/PA11 film manufactured with a temperature value of 210 C and using gradual levels of pressure (25 bars during 2 min, 40 bars during 2 min and 65 bars until the end of cycle). This configuration leads to a Young's modulus value of 36 GPa and a tensile strength of 174 MPa, with the highest storage modulus and the lowest damping factor values measured by DMA.

No abstract

No abstract

No abstract