The Water Treatment division of Westlake Chemical Corporation (NYSE: WLK), manufacturer of the Accu-Tab® chlorination and CleanSlate® dichlorination systems, today published a new case history outlining the key roles its water treatment systems perform within a recently upgraded wastewater processing plant in Southwestern Pennsylvania. Close to $50 million was invested by the borough in new construction and retrofits to the Combined Sewer Overflow (CSO) complex located in Donora, Penn. The processing plant, run by the Mon Valley Sewage Authority, now better protects surrounding rivers and streams throughout the region from storm sewage run-off contamination. The Mon Valley project is one of the first in the country to comply with the United States Clean Water Act mandating the reduction or elimination of sewer overflows. It is the largest CSO of its kind in the nation to use Westlake’s solid forms of chlorine and dichlorination chemicals and delivery technologies, which are marketed

$0.2700 cents per share dividend declared payable on June 9, 2021 The Board of Directors of Westlake Chemical Corporation (NYSE:WLK) declared today a regular dividend distribution of $0.2700 per share for the first quarter of 2021. This dividend will be payable on June 9, 2021, to stockholders of record on May 25, 2021. This is the 67th successive quarterly dividend that Westlake has declared since completing its initial public offering in August 2004. About Westlake Westlake is a global manufacturer and supplier of materials and innovative products that enhance life every day. Headquartered in Houston, we provide the building blocks for vital solutions — from packaging and healthcare products to automotive and consumer goods, to building and construction products. For more information, visit the company's web site at www.westlake.com . View source version on businesswire.com: https://www.businesswire.com/news/home/20210514005510/en/ Media Inquiries:
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• Declared quarterly distribution of $0.4714 per unit; 27th consecutive quarterly distribution • Ethylene sales agreement benefits Westlake Partners, providing predictable cash flows Westlake Chemical Partners LP (NYSE: WLKP) (the "Partnership") today reported net income attributable to the Partnership of $15.1 million, or $0.43 per limited partner unit, for the three months ended March 31, 2021. Ethylene production in the first quarter was impacted by a severe winter storm. As a result of the storm, Westlake Chemical OpCo LP ("OpCo") declared force majeure under OpCo's Ethylene Sales Agreement with Westlake Chemical Corporation ("Westlake Chemical"). Under this agreement, Westlake Chemical is obligated to purchase a defined amount of ethylene from OpCo each calendar year at cost plus a fixed price per pound. As a result of this agreement, net income in the first quarter of 2021 included a $9.7 million benefit related to a 2021 buyer deficiency as well as recovery of certain other

• 154% increase in first quarter 2021 operating income of $346 million vs first quarter 2020 Westlake Chemical Corporation (NYSE: WLK) (the "Company" or "Westlake") today reported net income attributable to Westlake for the three months ended March 31, 2021 of $242 million, or $1.87 per diluted share, on net sales of $2,357 million. Net income in the first quarter of 2021 increased by $97 million from first quarter 2020 net income of $145 million, or $1.13 per share, on net sales of $1,932 million. Income from operations of $346 million for the first quarter of 2021 increased by $210 million from income from operations of $136 million for the first quarter of 2020. The increases in net income and income from operations were primarily driven by higher sales prices and integrated margins for most of our major products including polyethylene and PVC, as well as higher earnings resulting from strong demand in our downstream building products business. These increases in demand were driven

$0.4714 cents per unit distribution declared payable on May 27, 2021 The Board of Directors of Westlake Chemical Partners GP LLC, the general partner of Westlake Chemical Partners LP (the "Partnership") (NYSE:WLKP), has declared a distribution by the Partnership of $0.4714 per unit. This is the 27th consecutive quarterly distribution announced by the Partnership since its initial public offering. The distribution will be payable on May 27, 2021, to unit holders of record on May 13, 2021. This release is intended to be a qualified notice under Treasury Regulation Section 1.1446-4(b). Brokers and nominees should treat one hundred percent (100.0%) of the Partnership’s distributions to non-U.S. investors as being attributable to income that is effectively connected with a United States trade or business. Accordingly, the Partnership’s distributions to non-U.S. investors are subject to federal income tax withholding at the highest applicable effective tax rate. About Westlake Chemical

Westlake Chemical Corporation (NYSE: WLK) will release its first quarter earnings for 2021 prior to the market opening on Tuesday, May 4, 2021. The company will host a conference call at 11:00 a.m. Eastern Time (10:00 a.m. Central Time) on the same day to discuss the earnings release. To access the conference call, dial (855) 760-8160, or (704) 288-0624 for international callers, approximately 10 minutes prior to the scheduled start time and reference passcode 4677649. The conference call will also be available via webcast at https://edge.media-server.com/mmc/p/fmi27wgt and the earnings release can be obtained via the company’s Web page at https://investors.westlake.com/news/default.aspx . A replay of the conference call will be available beginning two hours after its conclusion for seven days. To hear a replay, dial (855) 859-2056 or (404) 537-3406 for international callers. The replay passcode is 4677649. About Westlake: Westlake is a global manufacturer and supplier of materials

Westlake Chemical Partners (NYSE: WLKP) will release its first quarter earnings for 2021 prior to the market opening on Tuesday, May 4, 2021. The company will host a conference call at 1:00 p.m. Eastern Time (12:00 p.m. Central Time) on the same day to discuss the earnings release. To access the conference call, dial (855) 765-5686, or (234) 386-2848 for international callers, approximately 10 minutes prior to the scheduled start time and reference passcode 3327838. The conference call will also be available via webcast at https://edge.media-server.com/mmc/p/usgwdp4o and the earnings release can be obtained via the company's Web page at https://investors.wlkpartners.com/corporate-profile/default.aspx . A replay of the conference call will be available beginning two hours after its conclusion for seven days. To hear a replay, dial (855) 859-2056 or (404) 537-3406 for international callers. The replay passcode is 3327838. About Westlake Chemical Partners: Westlake Chemical Partners is a