CMC Materials (CCMP) DEFA14A Additional proxy soliciting materials

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

SCHEDULE 14A INFORMATION

PROXY STATEMENT PURSUANT TO SECTION 14(a) OF THE SECURITIES

EXCHANGE ACT OF 1934

Filed by Registrant ☑

Filed by a Party other than the Registrant ☐

Check the appropriate box:

☐	Preliminary Proxy Statement	☐	Confidential, for Use of the Commission Only (as permitted by Rule 14a-6(e)(2)).
☐	Definitive Proxy Statement
☑	Definitive Additional Materials
☐	Soliciting Materials Pursuant to Section 240.14a-11(c) or Section 240.14a-12

CABOT MICROELECTRONICS CORPORATION
(Exact name of Registrant as Specified in Its Charter)
Payment of Filing Fee (Check the appropriate box):
	☑	No fee required.
	☐	Fee computed on table below per Exchange Act Rules 14a-6(i)(1) and 0-11.
	(1)	Title of each class of securities to which transaction applies:
	(2)	Aggregate number of securities to which transaction applies:
	(3)	Per unit price or other underlying value of transaction computed pursuant to Exchange Act Rule 0-11 (set forth the amount on which the filing fee is calculated and state how it was determined):
	(4)	Proposed maximum aggregate value of transaction:
	(5)	Total fee paid:

*** Exercise YourRightto Vote ***

Important Notice Regarding the Availability of Proxy Materials for the

Stockholder Meeting to Be Held on March 06, 2019

			Meeting Information
	CABOTMICROELECTRONICSCORPORATION		Meeting Type:   Annual Meeting
			For holders as of:  January 11, 2019
			Date:  March 06, 2019        Time:  8:00 AM CST
			Location:	JW Marriott Houston Downtown
				806 Main St.
				Houston, TX 77002
	CABOT MICROELECTRONICS CORPORATION	You are receiving this communication because you hold shares in the above named company.
	ATTN: H. CAROL BERNSTEIN 870 N. COMMONS DRIVE AURORA, IL 60504	This is not a ballot. You cannot use this notice to vote these shares. This communication presents only an overview of the more complete proxy materials that are available to you on the Internet. You may view the proxy materials online atwww.proxyvote.com or easily request a paper copy (see reverse side).
		We encourage you to access and review all of the important information contained in the proxy materials before voting.
		See the reverse side of this notice to obtain proxy materials and voting instructions.

—  Before You Vote  —

How to Access the Proxy Materials

Proxy Materials Available to VIEW or RECEIVE:

1. Annual Report         2. Telephone/Internet insert (BR supplied)         3. Notice & Proxy Statement

How to View Online:

Have the information that is printed in the box marked by the arrow   (located on the following page) and visit:www.proxyvote.com.

How to Request and Receive a PAPER orE-MAIL Copy:

If you want to receive a paper ore-mail copy of these documents, you must request one. There is NO charge for requesting a copy. Please choose one of the following methods to make your request:

                               1)BY INTERNET:         www.proxyvote.com

                               2)BY TELEPHONE:     1-800-579-1639

                               3)BY E-MAIL*:             sendmaterial@proxyvote.com

*  If requesting materials bye-mail, please send a blanke-mail with the information that is printed in the box marked by the arrow   (located on the following page) in the subject line.

Requests, instructions and other inquiries sent to thise-mail address will NOT be forwarded to your investment advisor. Please make the request as instructed above on or before February 20, 2019 to facilitate timely delivery.

—  How To Vote  —

Please Choose One of the Following Voting Methods

VoteInPerson:Many stockholder meetings have attendance requirements including, but not limited to, the possession of an attendance ticket issued by the entity holding the meeting. Please check the meeting materials for any special requirements for meeting attendance. At the meeting, you will need to request a ballot to vote these shares. Vote By Internet: To vote now by Internet, go towww.proxyvote.com.Have the information that is printed in the box marked by the arrow    available and follow the instructions. VoteByMail:You can vote by mail by requesting a paper copy of the materials, which will include a proxy card.

	Voting items
	The Board of Directors recommends you vote FOR the following:
	1.	Election of Directors
		Nominees
	01	Richard S. Hill                 02    Susan M. Whitney
	The Board of Directors recommends you vote FOR proposals 2. and 3.
	2.	Non-binding stockholder advisory approval of our named executive officer compensation.
	3.	Ratification of the selection of PricewaterhouseCoopers LLP as the company’s independent auditors for fiscal year 2019.
	NOTE:	Such other business as may properly come before the meeting or any adjournment thereof.