Exhibit 99.1

STOCKHOLDER VOTING AGREEMENT

This Stockholder Voting Agreement (this “Agreement”) is made and entered into as of September 27, 2013, by and between Toray Industries, Inc., a Japanese kabushiki kaisha (“Parent”), and the undersigned stockholder (“Stockholder”) of Zoltek Companies, Inc., a Missouri corporation (the “Company”).

RECITALS

A.     Concurrently with the execution and delivery hereof, Parent, TZ Acquisition Corp., a Missouri corporation and a direct wholly-owned subsidiary of Parent (“Merger Sub”), and the Company are entering into an Agreement and Plan of Merger as of the date set forth above (as it may be amended or supplemented from time to time pursuant to the terms thereof, the “Merger Agreement”), which provides for the merger (the “Merger”) of Merger Sub with and into the Company in accordance with its terms.

B.     Stockholder is the beneficial owner (as defined in Rule 13d-3 under the Securities Exchange Act of 1934, as amended) of such number of shares of Common Stock of the Company as is indicated on the signature page of this Agreement.

C.     As a material inducement to the willingness of Parent and Sub to enter into the Merger Agreement, Parent has required that Stockholder enter into this Agreement.

NOW, THEREFORE, intending to be legally bound, the parties hereby agree as follows:

1.     Certain Definitions.

(a)     Capitalized terms used but not otherwise defined herein shall have the meanings ascribed thereto in the Merger Agreement. For all purposes of and under this Agreement, the following terms shall have the following respective meanings:

“Constructive Sale” means with respect to any security, a short sale with respect to such security, entering into or acquiring a derivative contract with respect to such security, entering into or acquiring a futures or forward contract to deliver such security, or entering into any other hedging or other derivative transaction that has the effect of either directly or indirectly materially changing the economic benefits or risks of ownership of such security.

“Shares” means (i) all shares of Company Common Stock owned, beneficially or of record, by Stockholder as of the date hereof, and (ii) all additional shares of Company Common Stock acquired by Stockholder, beneficially or of record, during the period commencing with the execution and delivery of this Agreement and expiring on the Expiration Date.

“Transfer” means, with respect to any security, the direct or indirect assignment, sale, transfer, tender, exchange, pledge, hypothecation, or the grant, creation, or suffrage of a lien, security interest, or encumbrance in or upon, or the gift, grant, or placement in trust, or the Constructive Sale or other disposition of such security (including transfers by testamentary or intestate succession, by domestic relations order or other court order, or otherwise by operation of law) or any right, title, or interest therein (including any right or power to vote to which the holder thereof may be entitled, whether such right or power is granted by proxy or otherwise), or the record or beneficial ownership thereof, the offer to make such a sale, transfer, Constructive Sale, or other disposition, and each agreement, arrangement, or understanding, whether or not in writing, to effect any of the foregoing.

2.     Transfer and Voting Restrictions.

(a)     At all times during the period commencing with the execution and delivery of this Agreement and expiring on the Expiration Date, Stockholder shall not, except in connection with the Merger, Transfer or suffer a Transfer of any of the Shares.

(b)     Except as otherwise permitted by this Agreement or by order of a court of competent jurisdiction, Stockholder will not commit any act that could restrict or affect Stockholder’s legal power, authority, and right to vote all of the Shares then owned of record or beneficially by Stockholder or otherwise prevent or disable Stockholder from performing any of his obligations under this Agreement. Without limiting the generality of the foregoing, except for this Agreement and as otherwise permitted by this Agreement, Stockholder shall not enter into any voting agreement with any person or entity with respect to any of the Shares, grant any person or entity any proxy (revocable or irrevocable) or power of attorney with respect to any of the Shares, deposit any of the Shares in a voting trust, or otherwise enter into any agreement or arrangement with any person or entity limiting or affecting Stockholder’s legal power, authority, or right to vote the Shares in favor of the approval of the Proposed Transaction.

3.     Agreement to Vote Shares.

(a)     Prior to the Expiration Date, at every meeting of the stockholders of the Company called, and at every adjournment or postponement thereof, and on every action or approval by written consent of the stockholders of the Company, Stockholder (in Stockholder’s capacity as such) shall appear at the meeting or otherwise cause the Shares to be present thereat for purposes of establishing a quorum and, to the extent not voted by the persons appointed as proxies pursuant to this Agreement, vote (i) in favor of the adoption of the Merger Agreement and the approval of the other transactions contemplated thereby (collectively, the “Proposed Transaction”), (ii) against the approval or adoption of any proposal made in opposition to, or in competition with, the Proposed Transaction, and (iii) against any of the following (to the extent unrelated to the Proposed Transaction): (A) any merger, consolidation, or business combination involving the Company or any of its Subsidiaries other than the Proposed Transaction; (B) any sale, lease, or transfer of all or substantially all of the assets of the Company or any of its Subsidiaries; (C) any reorganization, recapitalization, dissolution, liquidation, or winding up of the Company or any of its Subsidiaries; or (D) any other action that is intended, or could reasonably be expected, to result in a breach of any covenant, representation, or warranty or any other obligation or agreement of the Company under the Merger Agreement or of Stockholder under this Agreement or otherwise impede, interfere with, delay, postpone, discourage, or adversely affect the consummation of the Proposed Transaction (each of (ii) and (iii), a “Competing Transaction”).

(b)     If Stockholder is the beneficial owner, but not the record holder, of the Shares, Stockholder agrees to take all actions necessary to cause the record holder and any nominees to vote all of the Shares in accordance with Section 3(a).

4.     Grant of Irrevocable Proxy.

(a)     Stockholder hereby irrevocably appoints Parent and each of its executive officers or other designees (the “Proxyholders”), as Stockholder’s proxy and attorney-in-fact (with full power of substitution and resubstitution), and grants to the Proxyholders full authority, for and in the name, place, and stead of Stockholder, to vote the Shares, to instruct nominees or record holders to vote the Shares, or grant a consent or approval in respect of such Shares in accordance with Section 3 hereof and, in the discretion of the Proxyholders, with respect to any proposed adjournments or postponements of any meeting of Stockholders at which any of the matters described in Section 3 hereof are to be considered.

(b)     Stockholder hereby revokes any proxies heretofore given by Stockholder in respect of the Shares.

(c)     Stockholder hereby affirms that the irrevocable proxy set forth in this Section 4 is given in connection with the execution of the Merger Agreement, and that such irrevocable proxy is given to secure the performance of the duties of Stockholder under this Agreement. Stockholder hereby further affirms that the irrevocable proxy is coupled with an interest, is intended to be irrevocable in accordance with the provisions of Section 351.245 of the General and Business Corporation Law of Missouri, and may under no circumstances be revoked. The irrevocable proxy granted by Stockholder herein is a durable power of attorney and shall survive the bankruptcy or incapacity of Stockholder.

(d)     The Proxyholders may not exercise this irrevocable proxy on any matter except as provided above. Stockholder may vote the Shares on all other matters.

(e)     Parent may terminate this proxy at any time by written notice to Stockholder.

(f)     This proxy shall terminate and be of no further force or effect whatsoever immediately upon termination of this Agreement pursuant to the terms of Section 8 hereof.

5.     No Solicitation. Stockholder shall not, directly or indirectly, (i) initiate, solicit or knowingly encourage any inquiries regarding, or the making of, any proposal or offer that constitutes, or would reasonably be expected to lead to, an Acquisition Proposal, (ii) engage or participate in any discussions or negotiations regarding, or provide any non-public information or data to, any Person relating to, or that would reasonably be expected to lead to, any Acquisition Proposal, (iii) otherwise knowingly facilitate (including by providing information) any effort or attempt to make an Acquisition Proposal, (iv) approve, endorse, or recommend any Acquisition Proposal or (v) enter into any letter of intent or similar document or any agreement or arrangement contemplating or otherwise relating to any Acquisition Transaction.

6.     Action in Stockholder Capacity Only. Stockholder is entering into this Agreement solely in Stockholder’s capacity as a record holder and beneficial owner, as applicable, of Shares and not in Stockholder’s capacity as a director or officer of the Company. Nothing herein shall limit or affect Stockholder’s ability to act as an officer or director of the Company.

7.     Representations and Warranties of Stockholder. Stockholder hereby represents and warrants to Parent as follows:

(a)     (i) Stockholder owns the shares of Company Common Stock indicated on the signature page of this Agreement beneficially or of record, free and clear of any and all pledges, liens, security interests, mortgage, claims, charges, restrictions, options, title defects, or encumbrances, other than restrictions under applicable securities laws; and (ii) Stockholder does not beneficially own any securities of the Company other than he shares of Company Common Stock and the Company Options set forth on the signature page of this Agreement.

(b)     As of the date hereof and for so long as this Agreement remains in effect (including as of the date of the Company Shareholders Meeting, which, for purposes of this Agreement, includes any adjournment or postponement thereof), except as otherwise provided in this Agreement, Stockholder has full power and authority to (i) make, enter into, and carry out the terms of this Agreement and to grant the irrevocable proxy as set forth in Section 4; and (ii) vote all of the Shares in the manner set forth in this Agreement without the consent or approval of, or any other action on the part of, any other person or entity (including any Governmental Body). Without limiting the generality of the foregoing, Stockholder has not entered into any voting agreement (other than this Agreement) with any Person with respect to any of the Shares, granted any Person any proxy (revocable or irrevocable) or power of attorney with respect to any of the Shares, deposited any of the Shares in a voting trust, or entered into any arrangement or agreement with any Person limiting or affecting Stockholder’s legal power, authority, or right to vote the Shares on any matter.

(c)     This Agreement has been duly and validly executed and delivered by Stockholder and constitutes a valid and binding agreement of Stockholder enforceable against Stockholder in accordance with its terms, subject to applicable bankruptcy, insolvency, reorganization, moratorium, fraudulent conveyance, or other laws of general application relating to or affecting the enforcement of creditors’ rights generally, and as limited by laws relating to the availability of specific performance, injunctive relief, or other equitable remedies. The execution and delivery of this Agreement and the performance by Stockholder of the agreements and obligations hereunder will not result in any breach or violation of or be in conflict with or constitute a default under any term of any agreement or contract (whether written or oral) to or by which Stockholder is a party or bound, or any Order or Legal Requirement to which Stockholder (or any of Stockholder’s assets) is subject or bound, except for any such breach, violation, conflict, or default which, individually or in the aggregate, would not impair or adversely affect Stockholder’s ability to perform Stockholder’s obligations under this Agreement or render inaccurate any of the representations made herein.

(d)     Except as disclosed pursuant to the Merger Agreement, no investment banker, broker, finder, or other intermediary is entitled to a fee or commission from Parent, Merger Sub, or the Company in respect of this Agreement or the Merger Agreement based upon any arrangement or agreement made by or on behalf of Stockholder.

(e)     Stockholder understands and acknowledges that Parent and Merger Sub are entering into the Merger Agreement in reliance upon Stockholder’s execution and delivery of this Agreement and the representations and warranties of Stockholder contained herein.

8.     Termination. This Agreement shall terminate and be of no further force or effect whatsoever as of the earliest of (a) such date and time as the Merger Agreement shall have been validly terminated pursuant to the terms of Section 8 thereof, (b) a Change of Recommendation or (c) the Effective Time (the “Expiration Date”); provided, however, that (i) Section 10 shall survive the termination of this Agreement and (ii) the termination of this Agreement shall not relieve Stockholder from any liability for any inaccuracy in or breach of any representation, warranty, or covenant contained in this Agreement.

9.     Appraisal Rights. To the extent permitted by applicable law, Stockholder hereby waives any rights of appraisal or rights to dissent from the Merger that it may have under applicable law.

10.   Miscellaneous Provisions.

(a)     Amendments. No amendment of this Agreement shall be effective against any party unless it shall be in writing and signed by Parent and Stockholder.

(b)     Waivers. No action taken pursuant to this Agreement, including any investigation by or on behalf of any party, or any failure or delay on the part of any party in the exercise of any right hereunder, shall be deemed to constitute a waiver by the party taking such action of compliance with any representations, warranties, or covenants contained in this Agreement. The waiver by any party of a breach of any provision hereunder shall not operate or be construed as a waiver of any prior or subsequent breach of the same or any other provision hereunder. Any waiver by a party of any provision of this Agreement shall be valid only if set forth in a written instrument signed on behalf of such party.

(c)     Entire Agreement. This Agreement constitutes the entire agreement between the parties to this Agreement and supersedes all other prior agreements, arrangements, and understandings, both written and oral, between the parties with respect to the subject matter hereof.

(d)     Governing Law. This Agreement and the rights and obligations of the parties hereto shall be governed by and construed and enforced in accordance with the laws of the State of Missouri without regard to the conflicts of law provisions thereof that would cause the laws of any other jurisdiction to apply.

(e)     Consent to Exclusive Jurisdiction; Venue; Service of Process. Each of the parties hereto hereby irrevocably and unconditionally submits, for itself and its property, to the exclusive jurisdiction of the state courts of the State of Missouri located in St. Louis County, Missouri, or the Federal court of the United States of America located in the Eastern District of Missouri, and any appellate court from any thereof, in any action or proceeding arising out of or relating to this Agreement or the transactions contemplated hereby or for recognition or enforcement of any judgment relating thereto, and each of the parties hereby irrevocably and unconditionally (i) agrees not to commence any such action or proceeding except in such courts, (ii) agrees that any claim in respect of any such action or proceeding may be heard and determined in such Missouri state court or, to the extent permitted by Applicable Law, in such Federal court, (iii) waives, to the fullest extent it may legally and effectively do so, any objection that it may now or hereafter have to the laying of venue of any such action or proceeding in any such Missouri state or Federal court, and (iv) waives, to the fullest extent permitted by Applicable Law, the defense of an inconvenient forum to the maintenance of such action or proceeding in any such Missouri state or Federal court. Each of the parties hereto agrees that a final judgment in any such action or proceeding shall be conclusive and may be enforced in other jurisdictions by suit on the judgment or in any other manner provided by Applicable Law. Each party to this Agreement irrevocably consents to service of process in the manner provided for notices in Section 10(n). Nothing in this Agreement will affect the right of any party to this Agreement to serve process in any other manner permitted by Applicable Law.

(f)     WAIVER OF JURY TRIAL. EACH OF THE PARTIES HEREBY IRREVOCABLY WAIVES ALL RIGHT TO TRIAL BY JURY IN ANY ACTION, PROCEEDING OR COUNTERCLAIM (WHETHER BASED ON CONTRACT, TORT OR OTHERWISE) BETWEEN THE PARTIES ARISING OUT OF OR RELATING TO THIS AGREEMENT OR THE TRANSACTIONS CONTEMPLATED BY THIS AGREEMENT.

(g)     Attorneys’ Fees. In any action at law or suit in equity with respect to this Agreement or the rights of any of the parties, the prevailing party in such action or suit shall be entitled to receive its reasonable attorneys’ fees and all other reasonable costs and expenses incurred in such action or suit.

(h)     Assignment and Successors. This Agreement and all of the provisions hereof shall be binding upon and inure to the benefit of the parties and their respective successors and permitted assigns, including Stockholder’s estate and heirs upon the death of Stockholder, provided that except as otherwise specifically provided herein, neither this Agreement nor any of the rights, interests, or obligations of the parties may be assigned or delegated by any of the parties without prior written consent of the other party except that Parent, without obtaining the consent of any other party, shall be entitled to assign this Agreement or all or any of its rights hereunder. Any assignment in violation of the foregoing shall be void and of no effect.

(i)      No Third-Party Rights. Nothing in this Agreement, express or implied, is intended to or shall confer upon any Person (other than the parties) any right, benefit, or remedy of any nature whatsoever under or by reason of this Agreement.

(j)      Further Assurances. Stockholder agrees to cooperate fully with Parent and to execute and deliver such further documents, certificates, agreements, and instruments and to take such other actions as may be reasonably requested by Parent to evidence or reflect the transactions contemplated by this Agreement and to carry out the intent and purpose of this Agreement. Stockholder hereby authorizes Parent and the Company to publish and disclose in the Proxy Statement (including any and all documents and schedules filed with the Securities and Exchange Commission relating thereto) his identity and ownership of the Shares and the nature of his commitments, arrangements and understandings pursuant to this Agreement. Stockholder agrees to notify Parent promptly of any additional shares of Company Common Stock of which Stockholder becomes the record or beneficial owner after the date of this Agreement.

(k)     Severability. If any provision of this Agreement is held invalid or unenforceable by any court of competent jurisdiction, the other provisions of this Agreement will remain in full force and effect. Any provision of this Agreement held invalid or unenforceable only in part or degree will remain in full force and effect to the extent not held invalid or unenforceable.

(l)      Time of Essence. Time is of the essence with regard to all dates and time periods set forth or referred to in this Agreement.

(m)    Specific Performance; Injunctive Relief. The parties acknowledge that Parent shall be irreparably harmed by, and that there shall be no adequate remedy at law for, a violation of any of the covenants or agreements of Stockholder set forth in this Agreement. Therefore, Stockholder hereby agrees that, in addition to any other remedies that may be available to Parent upon any such violation, Parent shall have the right to enforce such covenants and agreements by specific performance, injunctive relief, or by any other means available to such party at law or in equity without posting any bond or other undertaking. Stockholder agrees that Stockholder will not oppose the granting of any injunction, specific performance, or other equitable relief on the basis that Parent has an adequate remedy of law or an injunction, award of specific performance, or other equitable relief is not an appropriate remedy for any reason at law in equity.

(n)     Notices. All notices, consents, requests, claims, and demands under this Agreement shall be in writing and shall be deemed given if (i) delivered to the appropriate address by hand or overnight courier (providing proof of delivery), or (ii) sent by facsimile or e-mail with confirmation of transmission by the transmitting equipment confirmed with a copy delivered as provided in clause (i), in each case to the parties at the following address, facsimile, or e-mail address (or at such other address, facsimile, or e-mail address for a party as shall be specified by like notice): (i) if to Parent, to the address, e-mail address, or facsimile provided in the Merger Agreement, including to the persons designated therein to receive copies; and (ii) if to Stockholder, to Stockholder’s address, e-mail address, or facsimile shown below Stockholder’s signature on the last page hereof.

(o)     Counterparts. This Agreement may be executed in several counterparts, each of which shall be deemed an original and all of which shall constitute one and the same instrument, and shall become effective when counterparts have been signed by each of the parties and delivered to the other parties.

(p)     Headings. The headings contained in this Agreement are for the convenience of reference only, shall not be deemed to be a part of this Agreement, and shall not be referred to in connection with the construction or interpretation of this Agreement.

(q)     Construction. In this Agreement, unless a clear contrary intention appears, (i) “hereunder,” “hereof,” “hereto,” and words of similar import shall be deemed references to this Agreement as a whole and not to any particular Section or other provision; (ii) “including” (and with correlative meaning “include”) means including without limiting the generality of any description preceding such term; (iii) “or” is used in the inclusive sense of “and/or”; and (iv) with respect to the determination of any period of time, “from” means “from and including” and “to” means “to but excluding.”

(r)     Legal Representation; Mutual Drafting. This Agreement was negotiated by the parties with the benefit of legal representation and each party has participated in the drafting of this Agreement. Any rule of construction or interpretation otherwise requiring this Agreement to be construed or interpreted against any party shall not apply to any construction or interpretation hereof.

[Signature page follows]

IN WITNESS WHEREOF, the undersigned have caused this Agreement to be duly executed as of the date first above written.

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