X0306 4 2018-03-05 0 0001262823 WESTLAKE CHEMICAL CORP WLK 0001298504 Mangieri George J 2801 POST OAK BOULEVARD, SUITE 600 HOUSTON TX 77056 0 1 0 0 SVP & Chief Accounting Officer Common Stock 2018-03-05 4 S 0 2161 113.41 D 2160 D The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions ranging from $113.38 to $113.42, inclusive. The reporting person undertakes to provide to Westlake Chemical Corp., any security holder of Westlake Chemical Corp. or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the ranges set forth in this footnote. George Mangieri by J. Feng POA 2018-03-06