A new synthesis process for hyperbranched polyester polyols based on neopentyl glycol is showing promising results for use in polyurethane coatings with increased chemical and corrosion resistance.

This study focuses on the synthesis and application of a hyperbranched polyester polyol using the so-called A2？+？CB2 method. Neopentyl glycol (A2) and 2,2-bis(hydroxymethyl)propionic acid (CB2) were processed by melt polycondensation to form a branched polyol. The structure of the resulting polyol was analysed using FTIR and NMR spectroscopy. The researchers determined the acid and hydroxyl numbers according to ASTM D974 and D4274, respectively.

The hyperbranched polyol was then reacted with isophorone diisocyanate (IPDI) to form polyurethanes. The researchers varied the OH:NCO ratios (1:1.2 / 1:1.4 / 1:1.6) to control the properties in a targeted manner. The resulting PU coatings were applied to steel plates and glass and thoroughly characterised.

High chemical resistance and good adhesion

The coatings tested showed good gloss levels and strong adhesion in the cross-cut test. The results in immersion tests with HCl, NaCl, NaOH and water were particularly convincing: the PU layers retained their integrity under aggressive chemical conditions. The electrochemical measurements additionally confirmed the corrosion protection potential against acidic and alkaline media.

The samples were examined microscopically using SEM, and their thermal stability was analysed using TGA. The study shows that hyperbranched polyester polyols – especially in combination with IPDI – are a promising option for functional PU coatings that have to be both mechanically and chemically resilient.

Source: Journal of Coatings Technology and Research, Volume 21, Pages 1085–1095, (2024)