A renewable approach to thermosetting resins

This is a review of recent developments of thermostable resins derived basically from vegetable oils. Natural vegetable oils have been transformed in polymers following three main routes. The first is the direct polymerization through the double bonds of the fatty acid chain. The cationic copolymerization of soybean oil with styrene, divinylbenzene and different amounts of styrenic monomers containing Si, B and P has been used to produce materials with improved flame retardant properties. The second route is the functionalization of the triglyceride double bonds to introduce readily polymerizable groups: The singlet oxygen photoperoxidation of the allylic positions of high oleic sunflower oil has been used to produce hydroperoxide-containing triglycerides that were dehydrated or reduced to produce respectively enone- and hydroxyl-containing triglycerides. The enone containing derivative has been chemically crosslinked with aromatic diamines through aza-Michael reactions leading to quinoline containing thermosets. The hydroxyl-containing triglycerides have been crosslinked radically prior the introduction of acrylate groups to produce conventional and flame retardant acrylate resins. The third route explored consists of using plant oil-derived chemicals like 10-undecenoic and oleic acids to produce tailor made monomers. Acyclic diene metathesis (ADMET) polymerization has been applied to prepare a set of thermosetting polyesters with flame retardant properties. Moreover thiol-ene click coupling has been used to prepare carboxylic monomers that have been explored to produce thermosetting polyanhydrides for fast drug delivery systems. A set of tailored polyols from the products of coordinative polymerization of the methyl epoxyoleate and the cationic ring opening polymerization of fatty acid-derived 2-oxazolines were also prepared. These polyols have been used to produce different thermosetting polyuretanes with a wide range of properties and characteristics. Finally, some recent research in producing benzoxazine thermosetting resins applying this renewable approach is presented. The benzoxazines based on diphenolic acid, a derivative of levulinic acid, are studied. (C) 2012 Elsevier Ltd. All rights reserved.