Novel epoxy-silica hybrid coatings by using ethoxysilyl-modified hyperbranched poly(ethyleneimine) with improved scratch resistance

- An alkoxysilylated hyperbranched polyethyleneimine was synthesized.
- Hybrid thermosets by sol-gel and DGEBA anionic homopolymerization were obtained.
- The formation of silica cage and branched structures was confirmed by Si-29 NMR.
- Hybrids with a high content of HBP showed an elastic recovery after scratching.
- Inorganic particles were smaller than 10 nm.

A new hyperbranched poly(ethyleneimine) with ethoxysilyl groups at the chain ends has been synthesized and characterized and then used in epoxy formulations to generate new organic/inorganic hybrid materials. Formulations of different proportions of diglycidylether of bisphenol A and the prepared ethoxysilylated hyperbranched poly(ethyleneimine) were maintained in a thermostatized controlled humidity chamber to form the inorganic silica network by a sol-gel process and then the epoxy resin was cured at higher temperature using 1-methylimidazole as anionic initiator.Transparent hybrid materials were prepared and characterized by thermal tests and their fine morphology was observed by transmission electron microscopy. The formation of the silicon structure was confirmed by 29Si NMR studies. Thermal stability was evaluated by thermogravimetry. Improvement of the mechanical coating performance was confirmed by scratch measurements.