<PAGE>
                                                        Exhibit 4.03


          SECOND AMENDMENT OF THE NAPHTHA SUPPLY AGREEMENT ENTERED INTO
            BETWEEN PETROBRAS AND BRASKEM (COPENE'S NEW DESIGNATION -
                         PETROQUIMICA DO NORDESTE S.A.)



Parties:

PETROLEO BRASILEIRO  S.A.--PETROBRAS,  a mixed-capital company with headquarters
in the City of Rio de Janeiro,  State of Rio de Janeiro, at Avenida Republica do
Chile,  65,  enrolled with the Corporate  Taxpayers  Registry of the Ministry of
Finance  under No.  33.000.167/0001-01,  hereinafter  referred to as  PETROBRAS,
represented  by the  Executive-Manager  of Marketing  and  Commercialization  of
Supplies; and

BRASKEM S.A., a stock company,  with  headquarters  at Rua Eteno No. 1561,  Polo
Petroquimico de Camacari-BA,  enrolled with the Corporate  Taxpayers Registry of
the Ministry of Finance  under No.  42.150.391/0001-70,  hereby  represented  by
means of its By-laws, hereinafter referred to as simply BRASKEM;

And as consenting intervenient:

OPP QUIMICA S.A., a Brazilian  joint-stock  company,  with  headquarters  at Rua
Eteno No. 1582, Polo  Petroquimico de Camacari,  Camacari-BA,  enrolled with the
Corporate  Taxpayers  Registry  (CNPJ)  under  No.  16.313.363/0001-17,   hereby
represented by means of its By-laws, hereinafter referred to as simply OPP;

WHEREAS:

(1) BRASKEM is an integrated  petrochemical  company, which main raw material is
petrochemical naphtha;

(2)  PETROBRAS  is  Braskem's  main  supplier  of  naphtha,  and the  commercial
relationship  between them is governed by the Naphtha Supply  Agreement  entered
into between the parties (the "Naphtha Supply Agreement"); and

(3) The parties are willing to amend the Naphtha  Supply  Agreement to negotiate
the establishment of a mortgage collateral in accordance with Article I, below;

The parties  enter into this  amendment  of the Naphtha  Supply  Agreement  (the
"Amendment") that will be governed by the following articles and conditions:

 ARTICLE I - COLLATERAL

1.1 The parties  acknowledge  that BRASKEM has a revolving credit limit up to R$
570,000,000.00  (five hundred and seventy  million  reais) with  PETROBRAS  (the
"Credit  Limit"),  represented  by full intent of PETROBRAS in  connection  with
BRASKEM due to the commercial relationship between both of them.

<PAGE>


1.2 As Credit  Limit  collateral,  and  contrary to the  maintenance  of current
commercial  conditions practiced in the context of the Naphtha Supply Agreement,
to BRASKEM,  through  its full  subsidiary  OPP,  commit to provide in first and
special  mortgage  the real  estates  described  and  listed in the draft of the
Mortgage Indenture (the "Mortgage  Indenture"),  contained in the "Exhibit 1" of
this instrument, with all current and future accretions and improvements.

1.3 For purpose of the provisions of the above-mentioned  Article 2.2, it is now
agreed between the Parties that the Mortgage  Indenture  shall be dully accepted
and with all legal regulations up to seven (7) business days as of the signature
of this Amendment.

1.4 With no consequence to the provisions of the Mortgage Indenture, it shall be
considered  legally due the whole  amount  payable in the context of the Naphtha
Supply Agreement,  in event of default,  by BRASKEM,  in payment of any invoices
not remedied in up to fifteen (15) days as of the default.

1.5 Invoices  paid after the maturity date shall be  monetarily  corrected  "pro
rata  tempore"  based on variance of the General  Price Index to  Market--IGP-M,
published by Fundacao Getulio Vargas--FGV--measured between maturity and payment
dates, plus 1% each month and a 10% fine added to the total debt, in addition to
court costs and fees, now fixed in twenty percent (20%) on the sentence  amount,
in case of judicial collection, which may be effected through executive means.

 ARTICLE II - GENERAL PROVISIONS

2.1 All terms and  conditions of the Naphtha  Supply  Agreement not  exclusively
amended by this amendment remain in effect.

2.2 The jurisdiction  elected to settle any disputes arising from or executed by
the present  instrument  is the Foro  Central da Comarca da Capital do Estado do
Rio de Janeiro (Central  Jurisdiction of the Capital of the Judicial District of
Rio de Janeiro), excluding any other jurisdictions.

In witness whereof, BRASKEM,  PETROBRAS and OPP enter into this Amendment of the
Naphtha Supply  Agreement in three (3)  counterparts  of equal form,  before two
witnesses  undersigned,  irrevocably and  irreversibly,  bound by themselves and
their successors.

Rio de Janeiro, February 24 2003



PETROLEO BRASILEIRO S.A.--PETROBRAS

(Illegible signature)

BRASKEM S.A.

(Illegible signature)

                                      -2-

<PAGE>


OPP QUIMICA S.A.

Witnesses:

(Signature)

Name: Marcelo (Illegible) Rabello Pinna

Bearer of the Identity Card (R.G.) No. 3442117188-27

Enrolled with the Individual Taxpayers Registry No. 552.699.237-34

                                      -3-