We chose n-butylamine to react with any excess acetic anhydride, forming n-butylethanamide.
To test the ability of n-butylamine to fully react with acetic anhydride, cytochrome C (bovine) was added to a vial already containing a 2:1 molar ratio of n-butylamine to acetic anhydride.
In general, protein samples are exposed to acetic anhydride, and then the excess anhydride is reacted with n-butylamine. HCl is added to adjust the pH to be appropriate for the enzyme being used.
Critical stress--[sigma] (MPa) Sample No ESC agent Dibutylamine n-Butylamine VBPET 59.09 [+ or -] 56.16 [+ or -] 41.87 [+ or -] 3.63 (a) 1.81 (a) 4.88 VFPET 80.45 [+ or -] 68.20 [+ or -] 63.07 [+ or -] 2.54 (a) 6.57 6.50 (a) Specimen presented yield point.
It can also be observed that n-bulylamine, which has a lower molar volume when compared with dibutylamine, was much more aggressive than dibutylamine because the values of critical stress in n-butylamine were lower than in dibutylamine.
On the other hand, in n-butylamine the maximum resistance was found only for the crystalline specimens at 60[degrees]C.
Time to failure--[t.sub.f] (h) No ESC agent Dibutylamine Sample 23[degrees]C 60[degrees]C 23[degrees]C 60[degrees]C AmVBPET > 24 > 24 8 < [t.sub.f] < 24 0.27 CrVBPET > 24 > 24 > 24 > 24 AmVFPET > 24 > 24 8 < [t.sub.f] < 24 0.18 CrVFPET > 24 > 24 > 24 > 24 Time to failure--[t.sub.f] (h) n-Butylamine Sample 23[degrees]C 60[degrees]C AmVBPET 0.42 0.08 CrVBPET 8 < [t.sub.f] < 24 > 24 AmVFPET 0.42 0.08 CrVFPET 3.0 > 24
Figure 5 shows the amorphous specimens tested in dibutylamine, which has a higher molar volume in comparison to n-butylamine. The transverse cracks can be seen in the macroscopic pictures and with improved details in the SEM images.
The lower molar volume of n-butylamine compared to dibutylamine favors its absorption by the polymer chains leading to a lower ESC resistance.
6, the amorphous VBPET in n-butylamine presented a bending failure and a shorter time to failure (5 min) at 60[degrees]C, but the specimen was more damaged at 23[degrees]C, as it presented a total break.