Exhibit 99.1

PRESS RELEASE

Contact:

Colleen Mumford

Vice President, Communications and Marketing

CMC Materials, Inc.

(630) 499-2600

CMC Materials Wins Favorable ITC Final Determination Finding a Violation By DuPont and Issuing Order Excluding DuPont’s Infringing CMP Slurries from U.S.

Aurora, IL, December 16, 2021 – CMC Materials, Inc. (Nasdaq: CCMP) (“CMC”), a leading global supplier of consumable materials primarily to semiconductor manufacturers, today announced that the company won a resounding legal victory in its United States International Trade Commission (ITC) case against DuPont de Nemours, Inc. and several DuPont subsidiaries (collectively, “DuPont”). The ITC issued a Final Determination that found that DuPont is unlawfully importing, selling, and marketing in the United States certain chemical mechanical planarization (“CMP”) slurries and components thereof that infringe a patent owned by CMC that is fundamental to advanced dielectric CMP slurries.

Based on the Final Determination, the ITC issued an exclusion order and cease and desist orders prohibiting DuPont’s importation, marketing, and sale of infringing products and components thereof in the United States. Following a 60-day Presidential review period, U.S. Customs and Border Protection will stop the importation into the United States of at least DuPont’s infringing Optiplane 2300 and Optiplane 2600 dielectric CMP slurries and components thereof for a period extending to 2035 (the expiration date of CMC’s patent). The ITC ordered DuPont to post a bond of 100 percent of the entered value of the infringing products imported or sold during the 60-day review period. It also required that any party expecting to “transition away” from the infringing products in the short term to provide a “documented need” for the products under penalty of criminal sanction. See Limited Exclusion Order.

"We are extremely pleased the ITC’s final determination found infringement by all of DuPont’s slurry products in this case," said H. Carol Bernstein, Vice President, Secretary and General Counsel. "The CMC breakthrough patent here is just one example of CMC’s continued and ongoing significant investments in R&D and manufacturing in the United States to advance CMP technology and provide cutting edge products to the semiconductor industry. We remain committed to protecting these investments and enforcing our valuable intellectual property, to the benefit of our customers."

ABOUT CMC MATERIALS, INC.

CMC Materials, Inc., headquartered in Aurora, Illinois, is a leading global supplier of consumable materials primarily to semiconductor manufacturers. The company’s products play a critical role in the production of advanced semiconductor devices, helping to enable the manufacture of smaller, faster and more complex devices by its customers. CMC Materials, Inc. is also a leading provider of performance materials to pipeline operators. The company's mission is to create value by delivering high-performing and innovative solutions that solve its customers’ challenges. The company has approximately 2,100 employees globally. For more information about CMC Materials, Inc., visit www.cmcmaterials.com, or contact Colleen Mumford, Vice President, Communications and Marketing, at 630-499-2600.

FORWARD LOOKING STATEMENTS

This press release contains forward-looking statements, which address a variety of subjects including, for example, future sales and operating results; growth or contraction, and trends in the industries and markets in which the company participates such as the semiconductor, and oil and gas, industries; the

acquisition of, investment in, or collaboration with other entities, and the expected benefits and synergies of such transactions; divestment or disposition, or cessation of investment, in certain of the company’s businesses; new product introductions; development of new products, technologies and markets; product performance; the financial conditions of the company's customers; the competitive landscape that relates to the company’s business; the company's supply chain; the targeted benefits of company cost reduction or optimization initiatives; natural disasters; various economic or political factors and international or national events, including related to global public health crises such as the Pandemic, and the enactment of trade sanctions, tariffs, or other similar matters; the generation, protection and acquisition of intellectual property, and litigation related to such intellectual property or third party intellectual property; environmental, health and safety laws and regulations, and related compliance and costs of compliance; the operation of facilities by the company; the company's management; foreign exchange fluctuation; the company's current or future tax rate, including the effects of changes to tax laws in the jurisdictions in which the company operates; cybersecurity threats and vulnerabilities; and, financing facilities and related debt, pay off or payment of principal and interest, and compliance with covenants and other terms, uses and investment of the company's cash balance, including dividends and share repurchases, which may be suspended, terminated or modified at any time for any reason by the company, based on a variety of factors. Statements that are not historical facts, including statements about CMC Materials’ beliefs, plans and expectations, are forward-looking statements. Such statements are based on current expectations of CMC Materials’ management and are subject to a number of factors and uncertainties, which could cause actual results to differ materially from those described in the forward-looking statements. For information about factors that could cause actual results to differ materially from those described in the forward-looking statements, please refer to CMC Materials’ filings with the Securities and Exchange Commission (“SEC”), including the risk factors contained in CMC Materials’ Annual Report on Form 10-K for the fiscal year ended September 30, 2021 filed on November 12, 2021. Except as required by law, CMC Materials undertakes no obligation to update forward-looking statements made by it to reflect new information, subsequent events or circumstances.

Source: CMC Materials