Hardener M is based on HDT technology, trimer of hexamethylene di-isocyanate (HD1), and Hardener D is based on both HDT and IPDT, trimer of isophorone diisocyanate (1PDI) technology.
5 It was also found that the fluorinated acrylic polyol has lower reactivity towards hydrophilic polyisocyanates, especially Hardener D that contains IPDT.
In the polyisocyanate side, two types of hydrophilic polyisocyanates are used: Hardener 1, which is HDT-based polyisocyanate, and Hardener 2, which incorporates bodi HDT and IPDT.
2) Incorporating IPDT in the HDT-based polyiso cyanate (Hardener 2) will improve anti-graffiti performance towards every testing graffiti except the black Sharpie.
The lower crosslinking density of the coatings incorporating IPDT does not give a definite explanation to the DOE analysis as Hardener 2 delivers better anti-graffiti performance.
If we look into the indentation depth of the coatings after seven-day cure at each stage of the indentation test as listed in Table 6, we can find systematically that in corporating IPDT lowers the indentation depth after the coating reaches sufficient crosslinking.
As a result, in corporating IPDT in HDT-based polyisocyanate enhances the barrier properties of these waterborne coatings for anti-graffiti performance.
Based upon the above studies, it is determined that a formulation using 40 wt% Polyol F in Polyol A with Hardener 2 containing IPDT at NCO/OH ratio at 1.