Nanocomposites based on polyurethane or polyurethane-epoxy hybrid resins prepared avoiding isocyanates
A fast curable non-isocyanate-based polyurethane- and polyurethane-epoxy network nanocomposite polymeric compositions are derived upon crosslinking a mixture comprising of natural or modified nano-clay [ionic phyllosilicate] with platelet thickness in the scale of A (˜1 nm) and aspect ratio (length/thickness) higher than 10 (nm)] preferably natural or modified montmorillonite with either a monomer(s) or oligomer(s) bearing at least one cyclocarbonate group or a mixture of the latter with an epoxy resin, with a hardener, which is a monomer or oligomer or mixtures therefrom, bearing primary and/or secondary amino groups. The use of the nanoclays reduces the gel time and increases the adhesion of the cured polyurethane and polyurethane/epoxy hybrid and also reduces its water absorption.
1. A method of forming a polyurethane-based polymer comprising the steps of:
(a) mixing one or more cyclocarbonate resins with at least one natural or synthetic, modified or unmodified nano-clay having a platelet thickness between 4-8 Å and an aspect ratio higher than 100; and with at least one hardener to form a composition; and
(b) curing the composition to form the polyurethane-based polymer and
wherein the polyurethane-based polymer is a non-isocyanate-based polyurethane polymer.
2. The method of claim 1 wherein the cyclocarbonate resin is a compound of formula I:
wherein R 1 and R 2 are each independently hydrogen, or a linear or branched, or cyclic, saturated or unsaturated group optionally substituted with one or more heteroatoms, oxygen-containing groups or nitrogen-containing groups.
3. The method of claim 1 wherein a compound containing one or more epoxy groups is further mixed with the cyclocarbonate resin, nano-clay, and hardener to form the composition.
4. The method of claim 1 wherein the nano-clay is a natural or modified bentonite, saponite, hectorite, montmorillonite or synthetic mica fluoride.
5. The method of claim 1 , wherein the composition is cured at room temperature.