<PAGE>

                                                                     EXHIBIT 4.5



                          HUNTSMAN INTERNATIONAL LLC,
                                   as Issuer


                      EACH OF THE GUARANTORS NAMED HEREIN


                                      and


                             The Bank of New York,
                                  as Trustee


                  ___________________________________________


                         FIRST SUPPLEMENTAL INDENTURE



                         Dated as of August ___, 2001

                  __________________________________________


                                      To

                  The Indenture, dated as of March 13, 2001,
                 among Huntsman International LLC, as Issuer,
                     each of the Guarantors named therein
                     and The Bank of New York, as Trustee,
     relating to the Issuer's 10 1/8% Senior Subordinated Notes due 2009
<PAGE>

                         FIRST SUPPLEMENTAL INDENTURE

     THIS FIRST SUPPLEMENTAL INDENTURE (the "Supplemental Indenture") is made as
of the ____ day of June, 2001, among Huntsman International LLC, a Delaware
limited liability company (the "Issuer"), each of the Guarantors named on the
signature pages hereof (collectively, the "Guarantors"), and The Bank of New
York, a New York banking corporation, as trustee (the "Trustee").

     WHEREAS, the Issuer, the Guarantors and the Trustee heretofore executed and
delivered an Indenture, dated as of March 13, 2001 (the "Indenture"); and

     WHEREAS, pursuant to the Indenture, (a) on March 13, 2001, the Issuer
issued and the Trustee authenticated and delivered (Euro)200 million aggregate
principal amount of the Issuer's 10 1/8% Senior Subordinated Notes due 2009 (the
"March Notes") and (b) on May 1, 2001, the Issuer issued and the Trustee
authenticated and delivered (Euro)50 million aggregate principal amount of the
Issuer's 10 1/8% Senior Subordinated Notes due 2009 (the "May Notes" and,
together with the March Notes, the "Initial Notes"); and

     WHEREAS, pursuant to an exchange offer (the "Exchange Offer") registered
with the Securities and Exchange Commission on a Registration Statement No. 333-
58578 on Form S-4 (the " Registration Statement"), the Issuer offered to, and
did, exchange (Euro)250 million in aggregate principal amount of its 10 1/8%
Senior Subordinated Notes due 2009 that are registered under the Securities Act
of 1933, as amended (the "Exchange Notes" and, together with the Initial Notes,
the "Notes") for (Euro)250 million in aggregate principal amount of the Initial
Notes; and

     WHEREAS, pursuant to a consent solicitation described in the Registration
Statement that was conducted by the Issuer concurrently with the Exchange Offer,
the Issuer solicited consents of the Holders to the amendments to the Indenture
contained in this Supplemental Indenture (collectively, the "Amendments"); and

     WHEREAS, the Holders of the outstanding Notes have duly consented to the
Amendments.

     Capitalized terms used but not defined herein shall have the meanings given
to them in the Indenture.

     NOW, THEREFORE, in consideration of the foregoing and notwithstanding any
provision of the Indenture which, absent this Supplemental Indenture, might
operate to limit such action, the Issuer, the Guarantors and the Trustee agree
as follows for the equal and ratable benefit of the Holders of the Notes:

                                       2
<PAGE>

                                   ARTICLE I
                                  DEFINITIONS

     SECTION 1.01.  General.  For all purposes of the Indenture and this
Supplemental Indenture, except as otherwise expressly provided or unless the
context otherwise requires the words "herein", "hereof" and "hereunder" and
other words of similar import refer to the Indenture and this Supplemental
Indenture as a whole and not to any particular Article, Section or subdivision.

                                  ARTICLE II
                                  AMENDMENTS

     SECTION 2.01.  Amendments.  Subject to Section 3.01 hereof, the Indenture
is hereby amended in the following respects:

     (a)  The definition of "Additional Notes" in Section 1.01 shall be amended
and restated in its entirety to read as follows:

     "Additional Notes" means Notes (other than the Initial Notes and other than
     Exchange Notes issued pursuant to an exchange offer for such Additional
     Notes under this Indenture or issuances under Section 2.07 or 2.16) not to
     exceed EU500 million, in the case of Euro Notes (or $500 million, without
     duplication, in the case of Dollar Notes) issued under this Indenture from
     time to time in accordance with Sections 2.01, 2.02, 2.18 and 4.12 hereof.

     (b)  Section 2.18 of the Indenture shall be shall be amended and restated
in its entirety to read as follows:

          The Company shall be entitled to issue Additional Notes, under this
     Indenture which shall have substantially identical terms as the Initial
     Notes, other than with respect to the date of issuance, issue price,
     currency denomination (in the case of Dollar Notes), amount of interest
     payable on the first payment date applicable thereto or upon a registration
     default as provided under a registration rights agreement related thereto
     and, terms of optional redemption, if any (and, if such Additional Notes
     shall be issued in the form of Exchange Notes, other than with respect to
     transfer restrictions); provided that such issuance is not prohibited by
                             --------
     Section 4.12; provided, further, that the aggregate principal value of
     Notes issued under this Indenture shall not exceed the greater of EU700
     million or $700 million except as provided in Sections 2.07 and 2.08, such
     aggregate principal amount to be calculated by the Company at a rate of
     EU1.00 per US$0.932535. The Initial Notes, any Additional Notes and all
     Exchange Notes issued in exchange therefor shall be treated as a single
     class for all purposes under this Indenture in accordance with Section
     2.02.

          With respect to any Additional Notes, the Company shall set forth in a
     resolution of its Board of Managers (or a duly appointed committee thereof)
     and

                                       3
<PAGE>

     in an Officers' Certificate, a copy of each of which shall be delivered to
     the Trustee, the following information:

          (1)  the aggregate principal amount of such Additional Notes to be
     authenticated and delivered pursuant to this Indenture;

          (2)  the issue price and the issue date of such Additional Notes and
     the amount of interest payable on the first payment date applicable
     thereto; and

          (3)  whether such Additional Notes shall be transfer restricted
     securities and issued in the form of Initial Notes or shall be registered
     securities issued in the form of Exchange Notes, each as set forth in the
     Exhibits hereto.

                                  ARTICLE III

                                 MISCELLANEOUS

     SECTION 3.01.  Effectiveness.  This Supplemental Indenture shall become
effective upon its execution and delivery by the Issuer, the Guarantors and the
Trustee.  Upon the execution and delivery of this Supplemental Indenture by the
Issuer, the Guarantors and the Trustee, the Indenture shall be supplemented in
accordance herewith, and this Supplemental Indenture shall form a part of the
Indenture for all purposes, and every Holder of Notes heretofore or hereafter
authenticated and delivered under the Indenture shall be bound thereby.

     SECTION 3.02.  Indenture Remains in Full Force and Effect.  Except as
supplemented hereby, all provisions in the Indenture shall remain in full force
and effect.

     SECTION 3.03.  Indenture and Supplemental Indenture Construed Together.
This Supplemental Indenture is an indenture supplemental to and in
implementation of the Indenture, and the Indenture and this Supplemental
Indenture shall henceforth be read and construed together.

     SECTION 3.04.  Confirmation and Preservation of Indenture.  The Indenture
as supplemented by this Supplemental Indenture is in all respects confirmed and
preserved.

     SECTION 3.05.  Conflict with Trust Indenture Act.  If any provision of this
Supplemental Indenture limits, qualifies or conflicts with any provision of the
Trust Indenture Act of 1939, as amended (the "Trust Indenture Act"), that is
required under the Trust Indenture Act to be part of and govern any provision of
this Supplemental Indenture, the provision of the Trust Indenture Act shall
control. If any provision of this Supplemental Indenture modifies or excludes
any provision of the Trust Indenture Act that may be so modified or excluded,
the provision of the Trust Indenture Act shall be deemed to apply to the
Indenture as so modified or to be excluded by this Supplemental Indenture, as
the case may be.

                                       4
<PAGE>

     SECTION 3.06.  Severability.  In case any provision in this Supplemental
Indenture shall be invalid, illegal or unenforceable, the validity, legality and
enforceability of the remaining provisions shall not in any way be affected or
impaired thereby.

     SECTION 3.07.  Headings.  The Article and Section headings of this
Supplemental Indenture have been inserted for convenience of reference only, are
not to be considered a part of this Supplemental Indenture and shall in no way
modify or restrict any of the terms or provisions hereof.

     SECTION 3.08.  Benefits of Supplemental Indenture, etc.  Nothing in this
Supplemental Indenture or the Notes, express or implied, shall give to any
Person, other than the parties hereto and thereto and their successors hereunder
and thereunder and the Holders of the Notes, any benefit of any legal or
equitable right, remedy or claim under the Indenture, this Supplemental
Indenture or the Notes.

     SECTION 3.09.  Successors.  All agreements of the Issuer and the Guarantors
in this Supplemental Indenture shall bind their respective successors.  All
agreements of the Trustee in this Supplemental Indenture shall bind its
successors.

     SECTION 3.10.  Trustee Not Responsible for Recitals.  The recitals
contained herein shall be taken as the statements of the Issuer and the
Guarantors, and the Trustee assumes no responsibility for their correctness.
The Trustee shall not be liable or responsible for the validity or sufficiency
of this Supplemental Indenture.

     SECTION 3.11.  Certain Duties and Responsibilities of the Trustee.  In
entering into this Supplemental Indenture, the Trustee shall be entitled to the
benefit of every provision of the Indenture relating to the conduct or affecting
the liability or affording protection to the Trustee, whether or not elsewhere
herein so provided.

     SECTION 3.12.  Governing Law.  The internal law of the State of New York
shall govern and be used to construe this Supplemental Indenture.

     SECTION 3.13.  Counterpart Originals.  The parties may sign any number of
copies of this Supplemental Indenture. Each signed copy shall be an original,
but all of them together represent the same agreement.

                                       5
<PAGE>

     IN WITNESS WHEREOF, the parties hereto have caused this Supplemental
Indenture to be duly executed and attested, all as of the date and year first
above written.


                                        HUNTSMAN INTERNATIONAL LLC

                                        By:
                                           -----------------------------------
                                           Name:
                                           Title:


                                        GUARANTORS:


                                        EUROFUELS LLC


                                        By:
                                           -----------------------------------
                                        Name:
                                        Title:


                                        EUROSTAR INDUSTRIES LLC


                                        By:
                                           -----------------------------------
                                        Name:
                                        Title:



                                        HUNTSMAN EA HOLDINGS LLC

                                        By:
                                           -----------------------------------
                                        Name:
                                        Title:



                                        HUNTSMAN ETYLENEAMINES LTD.,
                                        by its following General Partner:
                                        Huntsman EA Holdings LLC

                                        By:
                                           -----------------------------------
                                        Name:
                                        Title:

                                       6
<PAGE>

                                        HUNTSMAN INTERNATIONAL FINANCIAL LLC

                                        By:
                                           -----------------------------------
                                        Name:
                                        Title:



                                        HUNTSMAN INTERNATIONAL FUELS, L.P.,
                                        by its following General Partner:
                                        Eurofuels LLC

                                        By:
                                           -----------------------------------
                                        Name:
                                        Title:



                                        HUNTSMAN PROPYLENE OXIDE HOLDINGS LLC

                                        By:
                                           -----------------------------------
                                        Name:
                                        Title:



                                        HUNTSMAN PROPYLENE OXIDE LTD.,
                                        by its following General Partner:
                                        Huntsman Propylene Oxide Holdings LLC

                                        By:
                                           -----------------------------------
                                        Name:
                                        Title:



                                        HUNTSMAN TEXAS HOLDINGS LLC

                                        By:
                                           -----------------------------------
                                        Name:
                                        Title:

                                       7
<PAGE>

Executed as a Deed by, for and          TIOXIDE AMERICAS INC.
on behalf of in the presence of

                                        By:
-----------------------------------        -----------------------------------
Witness                                    Name:
                                           Title



                                        TIOXIDE GROUP

                                        By:
                                           -----------------------------------
                                            Name:
                                            Title:

                                       8
<PAGE>

                                        THE BANK OF NEW YORK, as Trustee

                                        By:
                                           -----------------------------------
                                           Name:
                                           Title:

                                       9