Being located in Wilmington, Delaware, and Delaware being a slave state until 1865, it is quite probable that he did use blacks in his labor force. I am not sure if they would have been Dupont's slaves or not. I thought it interesting that of 9 recorded Disasters in Delaware involving explosions up to 1928, at least 6 of those explosions were from the Dupont plant.

Delaware Disasters;

Wilmington, DE., Powder Mill Explosion, Aug 1855
Wilmington, DE., Dupont Powder Mill Exploson, Aug 1857
Rockland, DE., Dupont Powder Mills Explosion, Oct 1890
Clayton, DE., cannery boiler explosion, Sept 1892
Wilmington, DE., Jessup & Moore Paper Co Explosion, Aug 1902
Wilmington, DE., Dupont Powder Company Explosion, Aug 1915
Wilmington, DE., Dupont Powder Company Explosion, Dec 1915
Wilmington, DE., Dupont Powder Plant Explosion, Mar 1917
Washington, DE., Explosion, Jun 1928