Third Amendment to the Amended and Restated Revolving Credit Agreement

EXHIBIT 10.5.3

Third Amendment to the

Amended and Restated Revolving Credit Agreement

This Third Amendment to the Amended and Restated Revolving Credit Agreement (this “Amendment”) is made effective as of September 30, 2005 and is entered into between Union Carbide Corporation, as Borrower (“Borrower”), The Dow Chemical Company, as Lender (“Lender”), and Union Carbide Subsidiary C, Inc. and Union Carbide Chemicals & Plastics Technology Corporation as the Subsidiary Guarantors (the “Subsidiary Guarantors”) (together, the “Parties”).

BACKGROUND

The Parties have entered into the Amended and Restated Revolving Credit Agreement dated as of May 28, 2004, as amended by the First Amendment to the Amended and Restated Revolving Credit Agreement dated October 29, 2004 and the Second Amendment to the Amended and Restated Revolving Credit Agreement dated December 30, 2004 (the “Credit Agreement”).

The Parties desire to amend the Credit Agreement according to the terms in this Amendment.  Any capitalized terms used in this Amendment, but not otherwise defined in this Amendment, are as defined in the Credit Agreement.

THE AGREEMENT

1.             Amendment to Section 1.1.  The Parties agree to amend Section 1.1 of the Credit Agreement by replacing the definitions of “LIBOR” and “Scheduled Termination Date” in their entirety with the following definitions:

“‘LIBOR’ means the rate of interest announced publicly by the British Bankers Association as its one (1) month LIBOR rate for U.S. Dollars on the date that is two Business Days prior to the first day of the applicable period for which such interest is payable.

‘Scheduled Termination Date’ means December 30, 2006.”

2.             No Other Amendment or Waiver.  Except as expressly amended by this Amendment, the Credit Agreement and all other Loan Documents remain in full force and effect in accordance with their terms, and the Parties ratify and confirm the Credit Agreement and all other Loan Documents in all respects.

3.             Execution in Counterparts.  This Amendment may be executed in any number of counterparts and by different Parties in separate counterparts, each of which when so executed will be deemed to be an original and all of which taken together will constitute one and the same agreement.  Signature pages may be detached from multiple separate counterparts and attached to a single counterpart so that all signature pages are attached to the same document.

4.             Governing Law.  This Amendment and the rights and obligations of the Parties to this Amendment will be governed by, and construed and interpreted in accordance with, the law of the State of New York.

[Signature pages follow.]

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The Parties agree that this Amendment is effective as of September 30, 2005, and they have caused their authorized representatives to execute this Amendment below.

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