Versum Materials (VSM) 8-K Versum Materials Announces Filing and Mailing of Definitive Proxy Statement

Exhibit 99.1

Versum Materials Announces Filing and Mailing of Definitive Proxy Statement

in Connection with Proposed Merger with Entegris

Schedules April 26, 2019 Special Meeting of Stockholders to Vote on Transaction

TEMPE, Ariz.– March 21, 2019 –Versum Materials, Inc. (NYSE: VSM), a leading specialty materials supplier to the semiconductor industry, today announced the filing of its definitive proxy materials with the U.S. Securities and Exchange Commission in connection with the Company’s pending merger with Entegris, Inc. (NASDAQ: ENTG). Versum Materials also announced the commencement of mailing on or about March 22, 2019 of the definitive proxy materials, including a WHITE proxy card, relating to the Special Meeting of Versum Materials stockholders to be held on April 26, 2019 to consider the merger. Stockholders of record as of the close of business on April 2, 2019 will be entitled to vote at the Special Meeting.

Versum Materials and Entegris previously announced the expiration of the waiting period under the Hart-Scott-Rodino Antitrust Improvements Act of 1976, as amended, in connection with the previously-announced merger of equals between the two companies. With respect to Germany, antitrust clearance was received on March 19, 2019. The transaction remains subject to other closing conditions in the Agreement and Plan of Merger, dated as of January 27, 2019, by and among Versum Materials, Inc. and Entegris, Inc.

Versum Materials stockholders with questions about the Special Meeting, or who need assistance in voting their shares using the WHITE proxy card, may contact the Company’s proxy solicitor, Innisfree M&A Incorporated, toll-free at (877)456-3463.

Lazard and Citi are serving as financial advisors to Versum Materials and Simpson Thacher & Bartlett LLP is serving as legal counsel.

About Versum Materials

Versum Materials, Inc. (NYSE:VSM) is a leading global specialty materials company providing high-purity chemicals and gases, delivery systems, services and materials expertise to meet the evolving needs of the global semiconductor and display industries. Derived from the Latin word for “toward,” the name “Versum” communicates the company’s deep commitment to helping customers move toward the future by collaborating, innovating and creating cutting-edge solutions.

A global leader in technology, quality, safety and reliability, Versum Materials is one of the world’s leading suppliers of next-generation CMP slurries, ultra-thin dielectric and metal film precursors, formulated cleans and etching products, and delivery equipment that has revolutionized the semiconductor industry. Versum Materials reported fiscal year 2018 annual sales of about U.S. $1.4 billion, has approximately 2,300 employees and operates 14 major facilities in Asia and the North America. It is headquartered in Tempe, Arizona. Versum Materials had operated for more than three decades as a division of Air Products and Chemicals, Inc. (NYSE:APD).

For additional information, please visit http://www.versummaterials.com.

Forward Looking Statements

This communication contains forward-looking statements within the meaning of the Private Securities Litigation Reform Act of 1995 that are subject to risks and uncertainties and are made pursuant to the safe harbor provisions of Section 27A of the Securities Act of 1993, as amended and Section 21E of the Securities Exchange Act of 1934, as amended. Where a forward-looking statement expresses or implies an expectation or belief as to future events or results, such expectation or belief is expressed in good faith and believed to have a reasonable basis. The words “believe” “continue,” “could,” “expect,” “anticipate,” “intends,” “estimate,” “forecast,” “project,” “should,” “may,” “will,” “would” or the negative thereof and similar expressions are intended to identify such forward-looking statements. These forward-looking statements are only predictions and involve known and unknown risks and uncertainties, many of which are beyond Versum Materials, Inc.’s (“Versum Materials”) and Entegris, Inc.’s (“Entegris”) control. Statements in this communication regarding Versum Materials, Entegris and the combined company that are forward-looking, including projections as to the anticipated benefits of the proposed transaction, the impact of the proposed transaction on Versum Materials’ and Entegris’ business and future financial and operating results, the amount and timing of synergies from the proposed transaction, and the closing date for the proposed transaction, are based on management’s estimates, assumptions and projections, and are subject to significant uncertainties and other factors, many of which are beyond Versum Materials’ and Entegris’ control. These factors and risks include, but are not limited to, (i) weakening of global and/or regional economic conditions, generally or specifically in the semiconductor industry, which could decrease the demand for Versum Materials’ and Entegris’ products and solutions; (ii) the ability to meet rapid demand shifts; (iii) the ability to continue technological innovation and introduce new products to meet customers’ rapidly changing requirements; (iv) the concentrated customer base; (v) the ability to identify, effect and integrate acquisitions, joint ventures or other transactions; (vi) the ability to protect and enforce intellectual property rights; (vii) operational, political and legal risks of Versum Materials’ and Entegris’ international operations; (viii) Versum Materials’ and Entegris’ dependence on sole source and limited source suppliers; (ix) the increasing complexity of certain manufacturing processes; (x) raw material shortages and price increases; (xi) changes in government regulations of the countries in which Versum Materials and Entegris operate; (xii) the fluctuation of currency exchange rates; (xiii) fluctuations in the market price of Entegris’ stock; (xiv) the level of, and obligations associated with, Versum Materials’ and Entegris’ indebtedness; and (xv) other risk factors and additional information. In addition, material risks that could cause actual results to differ from forward-looking statements include: the inherent uncertainty associated with financial or other projections; the prompt and effective integration of Entegris’ businesses and the ability to achieve the anticipated synergies and value-creation contemplated by the proposed transaction; the risk associated with Versum Materials’ and Entegris’ ability to obtain the approval of the proposed transaction by their shareholders required to consummate the proposed transaction and the timing of the closing of the proposed transaction, including the risk that the conditions to the transaction are not satisfied on a timely basis or at all and the failure of the transaction to close for any other reason; the risk that a consent or authorization that may be required for the proposed transaction is not obtained or is obtained subject to conditions that are not anticipated; unanticipated difficulties or expenditures relating to the transaction, the response

of business partners and retention as a result of the announcement and pendency of the transaction; and the diversion of management time on transaction-related issues. For a more detailed discussion of such risks and other factors, see Versum Materials’ and Entegris’ filings with the Securities and Exchange Commission, including under the headings “Cautionary Statement Regarding Forward-Looking Statements” and “Risk Factors” in Entegris’ and Versum Materials’ preliminary joint proxy statement/prospectus that forms part of the registration statement on FormS-4 filed by Entegris, “Risks Factors” in Item 1A of Entegris’ Annual Report on Form10-K for the fiscal year ended December 31, 2018, filed on February 11, 2019, and Versum Materials’ Annual Report on Form10-K for the fiscal year ended September 30, 2018, filed on November 21, 2018 and in other periodic filings, available on the SEC website or www.entegris.com or www.versummaterials.com. Versum Materials and Entegris assume no obligation to update any forward-looking statements or information, which speak as of their respective dates, to reflect events or circumstances after the date of this communication, or to reflect the occurrence of unanticipated events, except as may be required under applicable securities laws. Investors should not assume that any lack of update to a previously issued “forward-looking statement” constitutes a reaffirmation of that statement.

Additional Information and Where to Find It

This communication does not constitute an offer to buy or sell or the solicitation of an offer to buy or sell any securities or a solicitation of any vote or approval. This communication relates to a proposed business combination between Versum Materials and Entegris. In connection with the proposed transaction, Entegris filed with the Securities and Exchange Commission (the “SEC”) a registration statement on FormS-4 on February 28, 2019, as amended on March 18, 2019, that includes a joint proxy statement of Versum Materials and Entegris and that also constitutes a prospectus of Entegris. The registration statement was declared effective by the SEC on March 20, 2019, and Versum Materials and Entegris will commence mailing of the definitive joint proxy statement/prospectus to the stockholders of Versum Materials and Entegris on or about March 22, 2019. Each of Versum Materials and Entegris also plan to file other relevant documents with the SEC regarding the proposed transaction. No offering of securities shall be made, except by means of a prospectus meeting the requirements of Section 10 of the U.S. Securities Act of 1933, as amended. INVESTORS AND SECURITY HOLDERS ARE URGED TO READ THE REGISTRATION STATEMENT, JOINT PROXY STATEMENT/PROSPECTUS AND OTHER DOCUMENTS FILED OR THAT MAY BE FILED WITH THE SEC CAREFULLY AND IN THEIR ENTIRETY IF AND WHEN THEY BECOME AVAILABLE BECAUSE THEY WILL CONTAIN IMPORTANT INFORMATION ABOUT THE PROPOSED TRANSACTION. Investors and security holders will be able to obtain free copies of these documents (if and when available) and other documents containing important information about Versum Materials and Entegris, once such documents are filed with the SEC through the website maintained by the SEC at http://www.sec.gov. Copies of the documents filed with the SEC by Entegris will be available free of charge on Entegris’ website at http://www.entegris.com or by contacting Entegris’ Investor Relations Department by email at irelations@entegris.com or by phone at978-436-6500. Copies of the documents filed with the SEC by Versum Materials will be available free of charge on Versum Materials’ website at http://investors.versummaterials.com or by phone at484-275-5907.

Participants in the Solicitation

Versum Materials, Entegris and certain of their respective directors and executive officers may be deemed to be participants in the solicitation of proxies in respect of the proposed transaction.

Information about the directors and executive officers of Versum Materials are set forth in its proxy statement for its 2019 annual meeting of shareholders, which was filed with the SEC on December 20, 2018, and Versum Materials’ Annual Report on Form10-K for the fiscal year ended September 30, 2018, which was filed with the SEC on November 21, 2018. Information about the directors and executive officers of Entegris are set forth in Entegris’ proxy statement for its 2019 annual meeting of shareholders, which was filed with the SEC on March 20, 2019, and Entegris’ Annual Report on Form10-K for the fiscal year ended December 31, 2018, which was filed with the SEC on February 11, 2019. Other information regarding the participants in the proxy solicitations and a description of their direct and indirect interests, by security holdings or otherwise, will be contained in the joint proxy statement/prospectus and other relevant materials to be filed with the SEC regarding the proposed transaction when such materials become available. Investors should read the joint proxy statement/prospectus carefully when it becomes available before making any voting or investment decisions. You may obtain free copies of these documents from Versum Materials or Entegris using the sources indicated above.

Contacts

Soohwan Kim, CFA

Head of Investor Relations

602-282-0957

Soohwan.Kim@versummaterials.com

Tiffany Elle

Global Communications

480-282-6475

Tiffany.Elle@versummaterials.com

Or

Meghan Gavigan / Emily Claffey / Julie Rudnick

Sard Verbinnen & Co

212-687-8080