Statement of Changes in Beneficial Ownership (Form 4)

FORM 4 Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b). Check this box to indicate that a transaction was made pursuant to a contract, instruction or written plan that is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c). See Instruction 10.

UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP OF SECURITIES Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934 or Section 30(h) of the Investment Company Act of 1940

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(Print or Type Responses)

1. Name and Address of Reporting Person * DEEGAN GLENN E. 2. Issuer Name and Ticker or Trading Symbol ASPEN AEROGELS INC [ASPN] 5. Relationship of Reporting Person(s) to Issuer (Check all applicable) _____ Director _____ 10% Owner __X__ Officer (give title below) _____ Other (specify below) CAO, GC & Corp Secretary (Last) (First) (Middle) C/O ASPEN AEROGELS, INC., 30 FORBES ROAD, BLDG B 3. Date of Earliest Transaction (Month/Day/Year) 09/30/2025 (Street) NORTHBOROUGH, MA 01532 4. If Amendment, Date Original Filed (Month/Day/Year) 6. Individual or Joint/Group Filing (Check Applicable Line) _X_ Form filed by One Reporting Person ___ Form filed by More than One Reporting Person (City) (State) (Zip) Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned

1.Title of Security (Instr. 3) 2. Transaction Date (Month/Day/Year) 2A. Deemed Execution Date, if any (Month/Day/Year) 3. Transaction Code (Instr. 8) 4. Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5) 5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4) 6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4) 7. Nature of Indirect Beneficial Ownership (Instr. 4) Code V Amount (A) or (D) Price Common Stock 09/30/2025 A 11,673(1) A $ 0 11,673(2) D

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Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned
(e.g., puts, calls, warrants, options, convertible securities)

1. Title of Derivative Security (Instr. 3)

2. Conversion or Exercise Price of Derivative Security

3. Transaction Date (Month/Day/Year)

3A. Deemed Execution Date, if any (Month/Day/Year)

4. Transaction Code (Instr. 8)

5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4, and 5)

6. Date Exercisable and Expiration Date (Month/Day/Year)

7. Title and Amount of Underlying Securities (Instr. 3 and 4)

8. Price of Derivative Security (Instr. 5)

9. Number of Derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4)

10. Ownership Form of Derivative Security: Direct (D) or Indirect (I) (Instr. 4)

11. Nature of Indirect Beneficial Ownership (Instr. 4)

Code

V

(A)

(D)

Date Exercisable

Expiration Date

Title

Amount or Number of Shares

Stock Options (Right to Buy)

$6.96

09/30/2025

A

16,416

(3)

09/30/2035

Common Stock

16,416

$ 0

16,416

D

Performance Share Units

(4)

09/30/2025

A

23,347

(4)

(4)

Common Stock

23,347

$ 0

23,347

D

Reporting Owners

Reporting Owner Name / Address	Relationships
	Director	10% Owner	Officer	Other
DEEGAN GLENN E. C/O ASPEN AEROGELS, INC. 30 FORBES ROAD, BLDG B NORTHBOROUGH, MA 01532			CAO, GC & Corp Secretary

Signatures

/s/ Andrew Lauzon, Attorney-in-Fact		10/02/2025
**Signature of Reporting Person		Date

Explanation of Responses:

*	If the form is filed by more than one reporting person, see Instruction 4(b)(v).
**	Intentional misstatements or omissions of facts constitute Federal Criminal Violations. See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
(1)	Each Restricted Stock Unit ("RSU") represents the right to receive one share of Common Stock upon vesting. The RSUs vest as to one-third of the shares on September 30, 2026, an additional one-third of the shares on September 30, 2027 and the remaining one-third of the shares on September 30, 2028.
(2)	Represents 11,673 RSUs.
(3)	The options vest as to one-third of the shares on September 30, 2026, an additional one-third of the shares on September 30, 2027 and the remaining one-third of the shares on September 30, 2028.
(4)	Each performance share unit ("PSU") represents a contingent right to receive one share of Common Stock upon vesting. The PSUs vest on March 5, 2028, following the completion of the performance period, which begins on January 1, 2025 and ends on December 31, 2027. Ranging between 0-200% of the target number of PSUs (as reflected in Table II above), the PSUs vest based on the total shareholder return of Common Stock relative to the total stockholder return of the components of the Russell 2000 Index.

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