Sonnenfeld: Ellen Kullman's exit bad for DuPont By: CNBC.com News October 06, 2015 at 08:36 AM EDT Despite recent weakness due to soft demand for agricultural products, DuPont has thrived under CEO Ellen Kullman, Jeffrey Sonnenfeld said. Read More >> Related Stocks: Axalta Coating Systems Ltd Berkshire Hathaway DuPont USA The Carlyle Group