**EXHIBIT10.5.4**

**Fourth Amendment to theAmended and Restated Revolving Credit Agreement**

This Fourth Amendment to the Amended and Restated Revolving CreditAgreement (this “Amendment”) is made effective as of September 30, 2006 and isentered into between Union Carbide Corporation, as Borrower (“Borrower”),The Dow Chemical Company, as Lender (“Lender”) and Union CarbideSubsidiary C, Inc. and Union Carbide Chemicals & Plastics TechnologyCorporation as the Subsidiary Guarantors (the “Subsidiary Guarantors”) (together,the “Parties”).

BACKGROUND

The Parties have entered into the Amended and Restated Revolving CreditAgreement dated as of May 28, 2004, as amended by the First Amendment to theAmended and Restated Revolving Credit Agreement dated October 29, 2004 theSecond Amendment to the Amended and Restated Revolving Credit Agreement datedDecember 30, 2004 and the Third Amendment to the Amended and Restated RevolvingCredit Agreement dated September 30, 2005 (the “Credit Agreement”).

The Parties desire to amend the Credit Agreement according to the termsin this Amendment.  Any capitalized termsused in this Amendment, but not otherwise defined in this Amendment, are asdefined in the Credit Agreement.

THE AGREEMENT

1.             Amendment to Section 1.1.  The Parties agree to amend Section 1.1 of theCredit Agreement by replacing the definition of “Scheduled Termination Date” with the following definition:

“*‘Scheduled Termination Date’ means December 30, 2007.”*

2.             No OtherAmendment or Waiver.  Except asexpressly amended by this Amendment, the Credit Agreement and all other LoanDocuments remain in full force and effect in accordance with their terms, andthe Parties ratify and confirm the Credit Agreement and all other LoanDocuments in all respects.

3.             Execution in Counterparts.  This amendment may be executed in any numberof counterparts and by different parties in separate counterparts, each ofwhich when so executed will be deemed to be an original and all of which takentogether will constitute one and the same agreement.  Signature pages may be detached from multipleseparate counterparts and attached to a single counterpart so that allsignature pages are attached to the same document.

4.             Governing Law. This Amendment and the rights and obligation of the Parties to thisAmendment will be governed by, and construed and interpreted in accordancewith, the law of the State of New York.

[Signature pagesfollow.]

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The Parties agreethat this Amendment is effective as of September 30, 2006, and they have causedtheir authorized representatives to execute this Amendment below.
| **LENDER:**                   | ** **                              | **SUBSIDIARY GUARANTORS:**           |
|-------------------------------|-----------------------------------------|--------------------------------------|
| ** **                    | ** **                              | ** **                           |
| **THE DOW CHEMICAL COMPANY**  | ** **                              | **UNION CARBIDE SUBSIDIARY C, INC.** |
| ** **                    | ** **                              | ** **                           |
| ** **                    | ** **                              | ** **                           |
| By:                           | /s/ GEOFFERY E. MERSZEI                 |                                 | By: | /s/ JAMES R. FITTERLING |
| Name:                         | Geoffery E. Merszei                     |                                 | Name: | James R. Fitterling |
| Title:                        | Executive Vice President and            |                                 | Title: | President |
|                          | Chief Financial Officer                 |                                 |   |   |
|                          |                                    |                                 |   |   |
|                          |                                    |                                 |   |   |
| **BORROWER:**                 | ** **                              | **UNION CARBIDE CHEMICALS &**    |
| ** **                    | ** **                              | ** **                           | **PLASTICS TECHNOLOGY** |
| **UNION CARBIDE CORPORATION** | ** **                              | **CORPORATION**                      |
| ** **                    | ** **                              | ** **                           |
| ** **                    | ** **                              | ** **                           |
| By:                           | /s/ EDWARD W. RICH                      |                                 | By: | /s/ ALEXANDER J. MAKAI |
| Name:                         | Edward W. Rich                          |                                 | Name: | Alexander J. Makai |
| Title:                        | Chief Financial Officer, Vice President |                                 | Title: | President |
|                          | and Treasurer                           |                                 |   |   |

** **

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