ratio of 30 50 20 respectively the catalyst tbt was again fixed at 0 5 based on the total weight of the three silanes this represented a tbt content of 0 36 percent based on the molar content of the silanes used after drying a white powder having a softening point of approximately 65 u00b0 c and being soluble in acetone but not toluene was obtained an aluminum panel was flow coated with a 30 solution of the above obtained resin solid in methylethyl ketone mek and cured 30 min 204 u00b0 c the resulting film was clear and was subjected to the following physical testing pencil hardness refers to the hardest pencil which does not cut through the cured film surface per american society for testing materials astm d3363 mandrel bend test flexibility astm d1737 s a film is coated onto a metal panel and the composite is bent 180 degrees around a mandrel of a given radius the smallest radius mandrel which does not result in cracks or other failure of the film is taken as an indication of the film 39 s flexibility t bend test flexibility astm d4145 s a film is coated onto a metal panel and the composite is bent on itself at an angle of 180 degrees to form a 34 ot 34 bend if cracking is observed the panel is again folded on itself as necessary until no cracking occurs solvent resistance s.