Pappas earned a Bachelor of Science degree in civil engineering at Georgia Institute of Technology and a Master of Business Administration from the Wharton School of the University of Pennsylvania.

[4][8] In 2010, Pappas became president and chief executive officer when the Dow Chemical Company spun off a group of its businesses and assets as Styron (later Trinseo).

Pappas served on the Executive Committee of the Society of Chemical Industry America and chaired the organization in 2017.

[16] Since 2015, Pappas has served on the external advisor board of the School of Civil & Environmental Engineering at Georgia Tech.

[17][18] He and his wife Susan, both civil engineers from Georgia Tech, have established the Susan G. and Christopher D. Pappas Professorship in the School of Civil and Environmental Engineering, first held beginning in 2016 by Patricia Mokhtarian.