Hybrid Thermoset Resins with In-Situ Produced Silicate Fillers
Final Report Abstract
Polyisocyanates are important precursors to produce both linear and crosslinked polymers with tunable properties. Their reaction with di- and polyols result in polyurethanes, with di- and polyamines yield polyureas. The isocyanate group can be transformed to primary amine via the reaction –NCO + H2O → – NH2 + CO2. This reaction is taking place in presence of aqueous media, including water glass (WG) which is a mixture of salts (usually sodium or potassium) of polysilicic acids. As a consequence, WG is an interesting reactant for compounds containing isocyanate groups. Moreover, WG can be considered as an alternative precursor to organosilane compounds to produce polysilicate (silica) in situ via the sol-gel route. WG when dispersed in polyisocyanates results in a highly reactive water-in-oil type emulsion (W/O). This cures very fast into a polyurea-based thermoset. The fast reaction between the water and the isocyanate is controlled by suitable emulsifiers which are usually organic phosphates. The related resin is referred to 3P coding the parent composition: polyisocyanate, phosphate and polysilicate. “Polysilicate” is formed by “hardening” of the dispersed WG phase. 3P resins are gaining acceptance in repair of pipes (canalization) and strengthening of walls (mining industry, tunnels) exploiting the fact that 3P resins cure also under water. The presence of phosphate is a problematic issue in the 3P systems due to its diffusion in the environment. The European Community Regulation on chemicals and their safe use (REACH—Registration, Evaluation, Authorization and Restriction of Chemical substances – EC 1907/2006) is dedicated to avoid possible contamination of the environment. Accordingly, our strategy was to reduce, or eventually to replace, the phosphate type emulsifiers in polyisocyanate/WG systems and thus to produce a 2P resin. The target emulsifiers should be co-reactive, prolong the pot life of the hybrid systems and improve their properties. As reactive emulsifiers different resins, such as epoxy, vinyl ester, melamine/formaldehyde, phenol/formaldehyde have been tried and many of them fulfilled the target task. The structure-property (mechanical, thermal, flame resistance) relationships of the related hybrid systems have been determined and discussed. Moreover, the complex chemistry of curing of 2P and 3P resins has been clarified. A further aim of this work was to achieve a better bonding between the polyurea matrix and polysilicate particles, formed via a hydrogel-xerogel transition (silicification). The related strategies covered the additional use of nanofillers and water soluble polymers. Promising results were achieved by the combined use of carbon nanotubes and vinyl ester as hybridization agent. The results achieved are of great importance for the praxis as several phosphate-free recipes have been developed. Due to the (co)reactivity of the hybridizing resin components the novel 2P resins are environmental benign as they do not contain any additive which is “released” in the surrounding. The developed hybrids have a great potential for replacement of 3P resins in repair of pipes and strengthening of walls, for heat, sound and fire insulating systems, as well as for use as coatings or matrix materials for fire and blast resistant structural composites.
Publications
- Hybrid resins from polyisocyanate/vinyl ester/water glass systems: structure and properties. Eur. Polymer J. 43(4) (2007) 1245-1257
Grishchuk, S.; Castellà, N.; Karger-Kocsis, J.
- Polyurea resins with in situ produced silicate filler from water glass: Static and dynamic mechanical properties. J. Macromol. Sci. Part B: Phys. 46 (2007) 21-31
Erdélyi, S.; Karger-Kocsis, J.; Nagy, G.
- Thermoset polyurea resins with in situ produced silicate filler from water glass: effects of water dispersible alumina nanoparticles. Plast. Rubber Comp. 36(3) (2007) 122-127
Castellà, N.; Grishchuk, S.; Karger-Kocsis, J.
- Hybrid resins from polyisocyanate, vinyl ester, melamineformaldehyde and water glass: structure and properties. Plast. Rubber Comp. 37(5-6) (2008) 204-209
Karger-Kocsis, J.; Castellà, N.; Grishchuk, S.
- Hybrid resins from polyisocyanate, epoxy resin and water glass: chemistry, structure and properties. J. Mater. Sci. 45 (2010) 1734-1743
Castellà, N.; Grishchuk, S.; Karger-Kocsis, J.; Unik, M.
- Hybrid thermosets from polyisocyanate/water glass/emulsifier systems: effects of melamine-formaldehyde resin. J. Appl. Polymer Sci. 119 (2011) 7-14
Castellà, N.; Grishchuk, S.; Karger-Kocsis, J.; Schehl, M.
