lunes, 6 de abril de 2009

Preparation and Properties of Polyester-Based Nanocomposite Gel Coat System

At present, the research attention has been focused on a new class of material called “clay polymer nanocomposites” after the discovery that polymer properties can be significantly improved by the presence of nanosize clay particles [1–3]. Lots of research works have been carried out in different polymer systems [4–8] based on this concept. Smectite group clays are normally used as a basic reinforcing element in nanocomposites, because of the high aspect ratio and platy morphology
The montmorillonite clay belongs to the family of Smectite clays. It is a crystalline material consisting of 1 nm thick sheets. These silicate sheets consist of alumina octahedra
sandwiched by two silica tetrahedra. The length of the individual sheets can range from 30 to 100 nm. Isomorphic substitution of alumina by magnesium results in net negative charge on the surface of the sheets which is balanced by exchangeable cations like Na+ or Ca+. These cations
can be readily exchanged with alkyl-ammonium ions on organomodification. These alkyl ammonium ions lowers the surface energy of the inorganic host and improve the wetting
characteristics with the polymer.
Incorporation of nanosize clay platelets to the polymer matrix increases modulus and strength Nanosize clay platelets decrease permeability, shrinkage
and increase resistance to heat and flammability. The fracture energy of the clay-polyester nanocomposite could be doubled even at low concentration (1.5wt %) of clay. The formation mechanism based on fabrication methods has been reported for unsaturated polyesterlayered
silicate nanocomposites. The method of mixing clay in polyester resin, curing agents, and curing conditions influence the properties of nanocomposites. The effect of nanoclay on the cure kinetics of unsaturated polyester resin in the range of 35 to 65◦C was investigated by Xu and Lee. The clay-polyester nanocomposites produced using reactive organoclay had better dynamic modulus.
Composites with gel coats are an essential part of many aspects of life today; from bathroom units to boats; from cultured marble to airplane structures; from windmills to automotive parts. Gel coat imparts good surface finish and bears better hardness, scratch resistance, and resistance to corrosion and water absorption to the composites.
It is expected that the incorporation of nanoclay in gel coat would lead to an improvement in the properties, which will make the material viable in high-loading environment.
In the present work, nanocomposite gel coat system was prepared using unsaturated polyester resin with aerosil and CaCO3 powders and organoclay. The influence of organoclay addition on mechanical, thermal, and water barrier properties of gel coat system has been studied.

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