X0306 4 2016-11-11 0 0001262823 WESTLAKE CHEMICAL CORP WLK 0001298504 Mangieri George J 2801 POST OAK BOULEVARD, SUITE 600 HOUSTON TX 77056 0 1 0 0 VP & Chief Accounting Officer Common Stock 2016-11-11 4 S 0 5696 52.9086 D 12503 D In accordance with the Securities and Exchange Commission's No Action Letter dated June 25, 2008, we have aggregated the sales that occurred on November 11, 2016 for ease of reporting. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions ranging from $52.90 to 52.95, 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 (1) to this Form 4. George J. Mangieri by J. Iglesias POA 2016-11-14