A. Schulman, a $1.6 billion plastics manufacturer in Akron, Ohio, said its controller, Donald McMillan, will take on the additional title of chief accounting officer. McMillan is also interim principal financial officer, a role he has been performing since Paul DeSantis left the company in February. Chief accounting officer is a new position for the company. McMillan, 51, has served as A. Schulman’s controller since 2006, and has worked in finance throughout his 15 years with the company. Before joining A. Schulman, he worked in public accounting.