TWELFTH AMENDMENT TO FOURTH AMENDED AND RESTATED REVOLVING CREDIT AND SECURITY AGREEMENT

EXHIBIT 10.1

TWELFTH AMENDMENT TO FOURTH AMENDED AND RESTATED

REVOLVING CREDIT AND SECURITY AGREEMENT

T HIS T WELFTH A MENDMENT TO F OURTH A MENDED AND R ESTATED R EVOLVING C REDIT AND S ECURITY A GREEMENT (the “Amendment”) is made this 8th day of April, 2005, by and among WinCup Holdings, Inc., Radnor Chemical Corporation, StyroChem U.S., Ltd., Radnor Holdings Corporation (“Radnor”), Radnor Delaware II, Inc., StyroChem Delaware, Inc., WinCup Texas, Ltd., StyroChem GP, L.L.C., StyroChem LP, L.L.C., WinCup GP, L.L.C., and WinCup LP, L.L.C. (each individually a “Borrower” and collectively, “Borrowers”), and PNC Bank, National Association (“PNC”), as Lead Arranger and Administrative Agent (defined below), Fleet Capital Corporation (“Fleet”), as Documentation Agent (defined below) and Lenders (defined below).

BACKGROUND

A. On December 26, 2001, Borrowers, the financial institutions which are now or which hereafter become a party thereto (individually, a “Lender” and collectively, the “Lenders”), and PNC, as agent for Lenders (PNC in such capacity, the “Agent”) entered into a certain Fourth Amended and Restated Revolving Credit and Security Agreement (as amended, modified, renewed, extended, replaced or substituted from time to time, the “Loan Agreement”) to reflect certain financing arrangements between the parties thereto. The Loan Agreement and all other documents executed in connection therewith are collectively referred to as the “Existing Financing Agreements.” All capitalized terms not otherwise defined herein shall have the meaning ascribed thereto in the Loan Agreement. In the case of a direct conflict between the provisions of the Loan Agreement and the provisions of this Amendment, the provisions hereof shall prevail.

B. Borrowers, Agent and Lenders modified certain definitions, terms and conditions contained in the Loan Agreement pursuant to that (i) certain First Amendment to Revolving Credit and Security Agreement dated February 4, 2002 to facilitate the execution of a Commitment Transfer Supplement by and between Lenders and Fleet Capital Corporation, (ii) certain Letter Agreement, dated as of March 21, 2002, among Borrowers, Agent and Lenders, (iii) certain Second Amendment to Revolving Credit, Term Loan and Security Agreement dated March 5, 2003, (iv) certain Third Amendment to Revolving Credit, Term Loan and Security Agreement dated August 1, 2003, (v) certain Fourth Amendment to Revolving Credit, Term Loan and Security Agreement dated September 12, 2003, (vi) certain Fifth Amendment to Revolving Credit, Term Loan and Security Agreement dated October 27, 2003, (vii) certain Sixth Amendment to Revolving Credit, Term Loan and Security Agreement dated November 17, 2003, (viii) certain Seventh Amendment to Revolving Credit, Term Loan and Security Agreement dated March 12, 2004, (ix) certain Eighth Amendment to Revolving Credit, Term Loan and Security Agreement dated April 27, 2004, (x) certain Ninth Amendment to Revolving Credit and Security Agreement dated September 27, 2004, (xi) certain Tenth Amendment to Fourth Amended and Restated Revolving Credit and Security Agreement dated February 15, 2005 and (xii) certain Eleventh Amendment to Fourth Amended and Restated Revolving Credit and Security Agreement dated March 30, 2005.

C. The Borrowers have requested and the Agent has agreed to modify certain definitions, terms and conditions in the Loan Agreement.

D. The parties have agreed, subject to the terms and conditions of this Amendment, to modify and amend the Existing Financing Agreements.

NOW THEREFORE, with the foregoing background hereinafter deemed incorporated by reference herein and made part hereof, the parties hereto, intending to be legally bound, promise and agree as follows:

1. Upon the Effective Date (as defined below), Sections I and VII and of the Loan Agreement shall be amended as follows:

(a)

(i) The definitions of “ Applicable Margin ”, “ Maximum Loan Amount ”, “ Maximum Revolving Advance Amount ” and “ Revolving Interest Rate ” shall be deleted in their entirety and replaced as follows:

“ Applicable Margin ” for any period shall be determined by the Fixed Charge Coverage Ratio of Radnor on a Consolidated Basis calculated for the most recent fiscal quarter with respect to the four fiscal quarters then ended which shall be increased or decreased from time to time, as the case may be, so long as no Default or Event of Default shall have occurred and be continuing, as of the first day of each fiscal quarter following the fiscal quarter reported upon in the financial statements delivered pursuant to Sections 9.7 and 9.8 hereof. The Applicable Margin with respect to Eurodollar Rate Loans shall be the percentage set forth below as corresponds to the applicable ratio set forth below:

In the event of a Default or Event of Default hereunder, the Applicable Margin shall at all times thereafter be 3.50%.

“ Maximum Loan Amount ” shall mean Seventy Eight Million Dollars ($78,000,000); provided that, upon the earlier of (i) May 1, 2005 or (ii) Borrowers’ repayment of

2

the outstanding principal balance of Advances by an amount not less than Twenty Million Dollars ($20,000,000) from the net proceeds of one or more Capital Event(s), Maximum Loan Amount shall mean Seventy Five Million Dollars ($75,000,000).

“ Maximum Revolving Advance Amount ” shall mean Seventy Eight Million Dollars ($78,000,000); provided that, upon the earlier of (i) May 1, 2005 or (ii) Borrowers’ repayment of the outstanding principal balance of Advances by an amount not less than Twenty Million Dollars ($20,000,000) from the net proceeds of one or more Capital Event(s), Maximum Revolving Advance Amount shall mean Seventy Five Million Dollars ($75,000,000).

“ Revolving Interest Rate ” shall mean an interest rate per annum equal to (a) the Alternate Base Rate plus fifty (50) basis points with respect to Domestic Rate Loans or (b) the sum