Importance of Gel Coating in Composite Structures and the Effect of Nanofillers on Their Properties Improvement

Composite structures should be acceptable in terms of their appearance and resistance to environmental factors and chemicals and their desirable physical properties. To achieve these requirements, “gel coat” is used as surface layer in composites. Composite structures are vulnerable when exposed to moisture environment. Mechanical properties of composite structures are strongly affected by water and moisture absorption, especially in composites made of hydrolysable resins such as polyesters. This causes osmotic swelling and loss of mechanical properties. The adsorbed water in presence of liquids caused by chemical reactions, create soft and gel-like surface that reduces the protective effect of “gelcoat”. On the other hand, resin leaching is another disadvantage of composite structures which could cause fiber leaching in the long term and increase corrosion resistance. Therefore, suitable choice of “gel coat” can increase the surface chemical resistance, reduce moisture absorption and increase the lifetime of composite structures. Also, recent progress in the field of nanoscience makes them appropriate choices for improving properties of the composites. In this paper, we investigated the importance of “gel coat” and the effective factors such as thickness and type of resin in the manufacture of composite structures in various industries and finally the effects of nanofillers on mechanical properties and water absorption.