Preparation and Spectroscopic Characterization of Si-Coated Vegetable Oils and their Application in In Situ Curing of Hybrid Coatings.
The modification of natural oils with heteroatoms leads to materials that can be employed in various areas thanks to their specific properties. Here, a solventless chemical modification of epoxidized linseed oil with an aminosilane without a catalyst is developed, and a detailed study of the chemical reactions involved during the process is reported. The mechanism results in two competitive reactions: the ring-opening of epoxides and trans-amidification of triglycerides with the amine functional group of aminosilane. These competitive reactions are shown by infrared spectroscopy (FTIR) and H-1, C-13, and 2D nuclear magnetic resonance (NMR). Even if the epoxy ring-opening remains the major route, the trans-amidification cannot be ignored. These modified oils are very reactive under atmospheric conditions by cross-linking according to a polycondensation of the -Si(OMe)(3) moieties or via a sol-gel process and lead to a rapid hardening. The final material gives hydrophobic and glossy coatings on cellulose and glass.Practical Applications: This paper details the easy route to convert vegetable oils into coatings by crosslinking under mild conditions. These bio-based materials can be applied as oil-based impregnating products for exterior wood protection and in the hydrophobization of paper.