Exhibit 10.18a

FIRST AMENDMENT TO

EMPLOYMENT AGREEMENT

THIS AMENDMENT (this “Amendment”) is made by and between Constar International
Inc. (the “Company”) and Walter Sobon (“Executive”).

WHEREAS, the Company and Executive are parties to an Executive Employment
Agreement dated December 12, 2005 (the “Agreement”);

WHEREAS, the Agreement, pursuant to its terms, will terminate on December 12,
2008 (the “Termination Date”);

WHEREAS, the Company and the Executive desire to amend the Agreement in order to
continue Executive’s employment with the Company.

NOW THEREFORE, intending to be legally bound hereby, the parties hereby amend
the Agreement, effective as of the date hereof, as follows:

1. Section 1 is hereby amended with the addition of the following new section
1.7 to the end thereof:

“1.7 “Effective Date” means June 4, 2008, notwithstanding anything herein to the
contrary.”

2. Section 3 of the Agreement is deleted in its entirety and replaced with the
following:

“The term of employment under this Agreement shall commence on the Effective
Date and, unless earlier terminated under Section 6 below or extended pursuant
to the next sentence, shall terminate on the third anniversary of the Effective
Date (the “Term of Employment”). The Term of Employment shall automatically be
extended, subject to the same terms, conditions and limitations as provided
herein, for an additional one year period on the first anniversary of the
Effective Date and on each such anniversary date thereafter unless, not later
than 180 days prior to any such anniversary, either party to this Agreement
shall have given notice to the other that the Term of Employment shall not be
extended or further extended beyond its then automatically extended term, if
any.”

3. Section 10.5 of the Agreement, the section regarding identification of the
Company’s counsel, is deleted in its entirety and replaced with the following:

“With a copy to Company’s counsel at:

Jonathan A. Clark, Esq.

--------------------------------------------------------------------------------

Pepper Hamilton, LLP

3000 Two Logan Square

Eighteenth and Arch Streets

Philadelphia, PA 19103-2799”

4. Except as otherwise amended by this Amendment, all provisions of the
Agreement shall remain in full force and effect and shall apply to this
Amendment (unless this Amendment specifically amends a particular provision of
the Agreement) and the Agreement and this Amendment shall be construed together
and considered one and the same agreement.

5. This Amendment may be executed in any number of counterparts and when so
executed, all of such counterparts shall constitute a single instrument binding
upon all parties notwithstanding the fact that all parties are not signatory to
the original or to the same counterpart. Any and all counterparts may be
executed by facsimile.

IN WITNESS WHEREOF, the Company has caused this Amendment to be executed by its
duly authorized representative, and Executive has executed this Agreement, in
each case on the 4th day of June, 2008.

 

CONSTAR INTERNATIONAL INC. By:  

/s/ Michael Hoffman

/s/ Walter Sobon

Walter Sobon