As filed with the Securities and Exchange Commission on April 28, 1998

                                                   Registration No.  333-46281
==============================================================================

                    SECURITIES AND EXCHANGE COMMISSION
                           WASHINGTON, DC 20549

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

                      Post-Effective Amendment No. 1
                                    TO
                                 FORM S-4
                          REGISTRATION STATEMENT
                                   UNDER
                        THE SECURITIES ACT OF 1933

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

                          SEALED AIR CORPORATION
                   (formerly known as W. R. Grace & Co.)
          (Exact name of Registrant as specified in its charter)

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



                                                                                                
            Delaware                                             3081                                           65-0654331
(State or Other Jurisdiction of                      (Primary Standard Industrial                             (IRS Employer
 Incorporation or Organization)                      Classification Code Number)                           Identification No.)
                                                             Park 80 East
                                                    Saddle Brook, New Jersey 07663
                                                            (201) 791-7600
                                   (Address, including Zip Code, & Telephone Number, including Area
                                          Code, of Registrant's Principal Executive Offices)

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

                                                       H. Katherine White, Esq.
                                                   General Counsel and Secretary
                                                        Sealed Air Corporation
                                                             Park 80 East
                                                    Saddle Brook, New Jersey 07663

                                      (Name, Address, Including Zip Code, and Telephone Number,
                                              Including Area Code, of Agent for Service)

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

                                                              copies to:
    Christopher Mayer, Esq.                              Robert B. Lamm, Esq.                           Andrew R. Brownstein, Esq.
     Davis Polk & Wardwell                           Vice President and Secretary                     Wachtell, Lipton, Rosen & Katz
      450 Lexington Avenue                                W. R. Grace & Co.                                51 West 52nd Street
    New York, New York 10017                             One Town Center Road                            New York, New York 10019
         (212) 450-4000                            Boca Raton, Florida 33486-1010                            (212) 403-1000
                                                           (561) 362-2000


      Approximate Date of Commencement of Proposed Sale to Public: As soon as
practicable after the effectiveness of this Registration Statement and the
effective time (the "Effective Time") of the merger (the "Merger") of a wholly
owned subsidiary of the Registrant with and into Sealed Air Corporation (US)
("Old Sealed Air"), as described in the Agreement and Plan of Merger dated as
of August 14, 1997.

      If the securities being registered on this Form are being offered in
connection with the formation of a holding company and there is compliance
with General Instruction G, check the following box.  [ ]

      If this form is filed to register additional securities for an offering
pursuant to Rule 462(b) under the Securities Act of 1933, as amended (the
"Securities Act"), check the following box and list the Securities Act
registration statement number of the earlier effective registration statement
for the same offering.  [ ]

      If this form is a post-effective amendment filed pursuant to Rule 462(d)
under the Securities Act, check the following box and list the Securities Act
registration statement number of the earlier effective registration statement
for the same offering.  [X] Reg No. 333-46281

==============================================================================

                             EXPLANATORY NOTE

               Sealed Air Corporation (formerly known as W. R. Grace & Co.)
(the "Registrant") hereby amends its Registration Statement on Form S-4 (No.
333-46281), declared effective on February 13, 1998 (the "Registration
Statement"), by filing this Post-Effective Amendment No. 1 (this "Amendment").

               At a Special Meeting of Stockholders of the Registrant held on
March 20, 1998, the Registrant's stockholders approved and adopted the
Agreement and Plan of Merger, dated as of August 13, 1997 (the "Merger
Agreement"), by and among the Registrant, Packco Acquisition Corp. and Old
Sealed Air and related transactions.  The Merger and the other transactions
contemplated by the Merger Agreement were consummated on March 31, 1998.

               This Amendment is being filed solely to add Exhibits 8.3, 8.4,
23.5 and 23.6 to the Registration Statement, which Exhibits are the tax
opinions delivered by counsel to Old Sealed Air and the Registrant,
respectively, at the Effective Time, and the consents of such counsel.



                                  PART II

                  INFORMATION NOT REQUIRED IN PROSPECTUS

Item 20. Indemnification of Directors and Officers.

               Section 145 of the General Corporation Law of the State of
Delaware (the "General Corporation Law") provides that: (1) under certain
circumstances a corporation may indemnify a director or officer made party to,
or threatened to be made party to, any civil, criminal, administrative or
investigative action, suit or proceeding (other than an action by or in the
right of the corporation) because such person is or was a director, officer,
employee or agent of the corporation, or because such person is or was so
serving another enterprise at the request of the corporation, against
expenses, judgments, fines and amounts paid in settlement reasonably incurred
by such person in connection with such action, suit or proceeding, if such
person acted in good faith and in a manner such person reasonably believed to
be in or not opposed to the best interests of the corporation, and, with
respect to criminal cases, had no reasonable cause to believe such person's
conduct was unlawful; (2) under certain circumstances a corporation may
indemnify a director or officer made party to, or threatened to be made party
to, any action or suit by or in the right of the corporation for judgment in
favor of the corporation because such person is or was a director, officer,
employee or agent of the corporation, or because such person is or was so
serving another enterprise at the request of the corporation, against expenses
reasonably incurred by such person in connection with the defense or
settlement of such action or suit if such person acted in good faith and in a
manner such person reasonably believed to be in or not opposed to the best
interests of the corporation; and (3) a director or officer shall be
indemnified by the corporation against expenses reasonably incurred by such
person in connection with and to the extent that such person has been
successful on the merits or otherwise in defense of any action, suit or
proceeding referred to in the preceding clauses, or in defense of any claim,
issue or matter therein.

               Under Article ELEVENTH of the Registrant's Amended and Restated
Certificate of Incorporation and Article 8 of the Registrant's By-laws,
indemnification of directors and officers is provided for to the fullest
extent permitted under the General Corporation Law.  Article TWELFTH of the
Registrant's Amended and Restated Certificate of Incorporation eliminates the
liability of directors for monetary damages for breach of fiduciary duty as
directors, except for liability (1) for any breach of the director's duty of
loyalty to the Registrant or its stockholders, (2) for acts or omissions not
in good faith or which involve intentional misconduct or a knowing violation
of law, (3) under Section 174 of the General Corporation Law (which relates to
the payment of unlawful dividends or unlawful stock purchases or redemptions),
or (4) for any transaction from which the director derived an improper
personal benefit.  The General Corporation Law, the Registrant's Amended and
Restated Certificate of Incorporation and the By-laws of the Registrant permit
the purchase by the Registrant of insurance for indemnification of directors
and officers.  The Registrant currently maintains directors and officers
liability insurance.

               The foregoing summary of Section 145 of the General Corporation
Law, Articles ELEVENTH and TWELFTH of the Amended and Restated Certificate of
Incorporation of the Registrant and Article 8 of the By-laws of the Registrant
is qualified in its entirety by reference to the relevant provisions of
Section 145, the relevant provisions of the Registrant's Amended and Restated
Certificate of Incorporation, which are incorporated herein by reference to
Exhibit 3.1 to the Registrant's Current Report on Form 8-K dated March 31,
1998, and the relevant provisions of the Registrant's By-laws, which are
incorporated herein by reference to Exhibit 3.2 to the Registrant's Current
Report on Form 8-K dated March 31, 1998.

Item 21.  Exhibits and Financial Statement Schedules.

              (a) Exhibits.  See Exhibit Index.


              (b) Financial Statement Schedules. Not Applicable.


              (c) Report, Opinion or Appraisal.  See Exhibits 5.1, 8.3 and
                  8.4.

Item 22.  Undertakings.

               The undersigned registrant hereby undertakes:

              (a) That prior to any public reoffering of the securities
registered hereunder through use of a prospectus which is a part of this
registration statement, by any person or party who is deemed to be an
underwriter within the meaning of Rule 145(c), such reoffering prospectus will
contain the information called for by the applicable registration form with
respect to reofferings by persons who may be deemed underwriters, in addition
to the  information called for by the other items of the applicable form.

              (b) That every prospectus (i) that is filed pursuant to
paragraph (b) immediately preceding, or (ii) that purports to meet the
requirements of Section 10(a)(3) of the Securities Act of 1933 and is used in
connection with an offering of securities subject to Rule 415, will be filed
as a part of an amendment to this registration statement and will not be used
until such amendment is effective, and that, for purposes of determining any
liability under the Securities Act of 1933, each such post-effective amendment
shall be deemed to be a new registration statement relating to the securities
offered therein, and the offering of such securities at that time shall be
deemed to be the initial bona fide offering thereof.

              (c) That, for purposes of determining any liability under the
Securities Act of 1933, each filing of the registrant's annual report pursuant
to Section 13(a) or 15(d) of the Securities Exchange Act of 1934 (and, where
applicable, each filing of an employee benefit plan's annual report pursuant
to Section 15(d) of the Securities Exchange Act of 1934) that is incorporated
by reference in this registration statement shall be deemed to be a new
registration statement relating to the securities offered therein, and the
offering of such securities at that time shall be deemed to be the initial bona
fide offering thereof.

              (d) To respond to requests for information that is incorporated
by reference into the Joint Proxy Statement/Prospectus pursuant to Item 4,
10(b), 11 or 13 of this Form, within one business day of receipt of such
request, and to send the incorporated documents by first class mail or other
equally prompt means.  This includes information contained in documents filed
subsequent to the effective date of this registration statement through the
date of responding to the request.

              (e) To supply by means of a post-effective amendment all
information concerning a transaction, and the company being acquired involved
therein, that was not the subject of and included in this registration
statement when it became effective.

              (f) Insofar as indemnification for liabilities arising under the
Securities Act of 1933 may be permitted to directors, officers and controlling
persons of the registrant pursuant to the foregoing provisions, or otherwise,
the registrant has been advised that in the opinion of the Securities and
Exchange Commission such indemnification is against public policy as expressed
in the Act and is, therefore, unenforceable.  In the event that a claim for
indemnification against such liabilities (other than the payment by the
registrant of expenses incurred or paid by a director, officer or controlling
person of the registrant in the successful defense of any action, suit or
proceeding) is asserted by such director, officer or controlling person in
connection with the securities being registered, the registrant will, unless
in the opinion of its counsel the matter has been settled by controlling
precedent, submit to a court of appropriate jurisdiction the question whether
such indemnification by it is against public policy as expressed in the Act
and will be governed by the final adjudication of such issue.


                                SIGNATURES

               Pursuant to the requirements of the Securities Act of 1933, the
Registrant has duly caused this Amendment to be signed on its behalf by the
undersigned, thereunto duly authorized, in the Town of Saddle Brook, State of
New Jersey on April 28, 1998.

                                        SEALED AIR CORPORATION



Date: April 28, 1998                    By: /s/ T. J. Dermot Dunphy
                                            -------------------------------
                                            Name:  T. J. Dermot Dunphy
                                            Title: Chairman of the Board,
                                                   Chief Executive Officer
                                                   and Director


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

               Pursuant to the requirements of the Securities Act of 1933,
this Amendment has been signed below by the following persons on behalf of the
Registrant in the capacities and on the dates indicated.


                                                                             
            Signature                                Title                              Date
            ---------                                -----                              ----

     /s/ T. J. Dermot Dunphy            Chairman of the Board,                     April 28, 1998
   ---------------------------          Chief Executive Officer and Director
       (T.J. Dermot Dunphy)             (Principal Executive Officer)


         /s/ Horst Tebbe                Vice President-Finance and Chief           April 28, 1998
   ---------------------------          Financial Officer
          (Horst Tebbe)                 (Principal Financial Officer)


      /s/ Jeffrey S. Warren             Controller                                 April 28, 1998
   ---------------------------          (Principal Accounting Officer)
       (Jeffrey S. Warren)

                                                  Director
   ---------------------------
           (Hank Brown)

        /s/ John K. Castle                        Director                         April 28, 1998
   ---------------------------
         (John K. Castle)

                                                  Director
   ---------------------------
       (Christopher Cheng)

      /s/ Lawrence R. Codey                       Director                         April 28, 1998
   ---------------------------
       (Lawrence R. Codey)

   /s/ Charles F. Farrell, Jr.                    Director                         April 28, 1998
   ---------------------------
    (Charles F. Farrell, Jr.)

        /s/ David Freeman                         Director                         April 28, 1998
   ---------------------------
         (David Freeman)

                                                  Director
   ---------------------------
       (Virginia A. Kamsky)

        /s/ Alan H. Miller                        Director                         April 28, 1998
   ---------------------------
         (Alan H. Miller)

                                                  Director
   ---------------------------
         (John E. Phipps)

       /s/ R. L. San Soucie                       Director                         April 28, 1998
   ---------------------------
        (R. L. San Soucie)




                               EXHIBIT INDEX




 Exhibit
 Number                            Description                                       Page
 ------                            -----------                                       ----
                                                                               
  *2.1    Agreement and Plan of Merger dated as of August 14, 1997 among the
          Registrant, Sealed Air Corporation and Packco Acquisition Corp.
          (included as Annex A to the Joint Proxy Statement/Prospectus contained
          in this Registration Statement).

  *2.2    Form of Distribution Agreement to be dated as of the Effective Time
          between the Registrant, W. R. Grace & Co.-Conn. and Grace Speciality
          Chemicals, Inc. (included as Annex B to the Joint Proxy
          Statement/Prospectus contained in this Registration Statement).

  *3.1    Amended and Restated Certificate of Incorporation of W. R. Grace & Co.
          (incorporated herein by reference to Exhibit 4.1 to W. R. Grace & Co.'s
          Form 8-K filed on October 10, 1996 (the "October 1996 Form 8-K")).

  *3.2    Amended and Restated By-Laws of W. R. Grace & Co. (incorporated
          herein by reference to Exhibit 4.2 to the October 1996 Form 8-K).

  *4.1    Form of Certificate of Designations, Preferences and Rights of Series A
          Convertible Preferred Stock of New Sealed Air.

  *4.2    Commitment Letters for the New Credit Agreements.

  *5.1    Opinion of Wachtell, Lipton, Rosen & Katz regarding the validity of the
          securities being registered (including consent).

  *8.1    Form of opinion of Davis Polk & Wardwell regarding certain federal
          income tax consequences relating to the Merger (including consent).

  *8.2    Form of opinion of Wachtell, Lipton, Rosen & Katz regarding certain
          federal income tax consequences relating to the Reorganization and Merger
          (including consent).

   8.3    Opinion of Davis Polk & Wardwell regarding certain federal income tax
          consequences relating to the Merger (including consent).

   8.4    Opinion of Wachtell, Lipton, Rosen & Katz regarding certain federal
          income tax consequences relating to the Reorganization and Merger
          (including consent).

 *23.1    Consents of Price Waterhouse LLP.

 *23.2    Consent of KPMG Peat Marwick LLP.

  23.3    Consent of Davis Polk & Wardwell (included in the opinion filed as
          Exhibit 8.3 to this Amendment).

  23.4    Consent of Wachtell, Lipton, Rosen & Katz (included in the opinion filed
          as Exhibit 8.4 to this Amendment).

 *24.1    Form of Power of Attorney.

 *99.1    Form of Sealed Air Corporation Proxy Card.

 *99.2    Form of W. R. Grace & Co. Proxy Card.

 *99.3    Consent of Donaldson, Lufkin & Jenrette Securities Corporation.

 *99.4    Consent of Merrill Lynch & Co.

 *99.5    Consent of Credit Suisse First Boston Corporation.

 *99.6    Consents of persons named as future directors of the Registrant.

- ----------
*Previously filed.