Exhibit 31.1 CERTIFICATION I, Stephen D. Newlin Exhibit 31.2 CERTIFICATION I, Bradley C. Exhibit 32.2 CERTIFICATION PURSUANT TO 18 U.S.C.

Exhibit 31.1 CERTIFICATION I, Robert M. Patterson Exhibit 31.2 CERTIFICATION I, Bradley C. Exhibit 32.2 CERTIFICATION PURSUANT TO 18 U.S.C.

Certificate Avient Corporation S E s Certificate Of Conformance This is to certify that the Quality Management System of: Avient Corporation 33587 Walker Road, Building 428 Avon Lake OH 44012 United States has been assessed by ABS Quality Evaluations, Inc. and found to be in conformance with the requirements set forth by: ISO 9001:2015 The Quality Management System is applicable to: Manufacture of plastic compounds, color and performance additives, engineered thermoplastics, vinyl resins, custom mixed plastic materials, custom and commodity colorants for plastics, polyurethane systems, and plasticizers with design and sampling support at Suwanee, GA, and purchasing, customer service, logistics, quality, design and sampling support at PolyOne Corporate Headquarters at Avon Lake, OH, and distribution of resins Certificate No: 31307 Certification Date: 12 OCT 1995 Effective Date: 11 JUL 2024 Expiration Date 07 OCT 2025 Revision Date: 17 JUL 2024 Dominic Townsend, President Page 1 of 4 S E s ISO 9001:2015 Certificate Of Conformance ANNEX Certificate No.: 31307 Avient Corporation At the below facilities The Manufacture of Pultruded and Filament wound components Pultrusion and CRTM 3943, Valley East Industrial Drive, Buildings 1,2,3,4 Birmingham - AL 35217 United The Manufacture of Pultruded and Filament wound components Pultrusion and Filament Wound Tubing 3968, Valley East Industrial Drive, Building 5 Birmingham - AL 35217 United States The Manufacture of Pultruded and Filament wound components Pultrusion 3950, Valley East Industrial Drive, Building 6 Birmingham - AL 3517 United States Corporation Management of QMS.

Certificate Avient Corporation This is to certify that the Environmental Management System of: Avon Lake Corporate 33587 Walker Road Avon Lake OH 44012 United States (WITH ADDITIONAL FACILITIES LISTED ON ATTACHED ANNEX) has been assessed by ABS Quality Evaluations, Inc. and found to be in conformance with the requirements set forth by: The Environmental Management System is applicable to: Responsible Care Corporate Support Activities in Sr. Leadership, EHS&S-PS, Facility Services, Design & Development, Information Technology, Sourcing, Logistics, Legal, and Human Resources Certification Date: 29 SEP 2023 Effective Date: 27 FEB 2025 Expiration Date: 27 SEP 2026 Revision Date: 05 MAR 2025 Dominic Townsend, President Page 1 of 5 Avon Lake Corporate Responsible Care Corporate Support Activities in Sr.

IATF Certificate Place and date: For the issuing office: Katy, TX, 10 December 2024 Revision 2 DNV - Business Assurance 1400 Ravello Drive, Katy, TX, 77449- 5164, USA Sherif Mekkawy Management Representative Lack of fulfilment of conditions as set out in the Certification Agreement may render this Certificate invalid. ACCREDITED UNIT: DNV Business Assurance USA Inc., 1400 Ravello Drive, Katy, TX, 77449-5164, USA - TEL: +1 281-396-1000. www.dnv.com Page 1 of 2 MANAGEMENT SYSTEM CERTIFICATE Certificate no.: 273138-2018-AQ-RGC-IATF IATF Certificate No: 0558323 Valid: 10 December 2024 – 09 December 2027 This is to certify that the management system of Polyone - Shenzhen Co., Ltd. No. 1, Qihang Industry Park, Haoxiang Road, Shajing Town, Baoan, Shenzhen, Guangdong, China 518104 (USI: C5M65R) and, if applicable, the remote supporting locations as mentioned in the Appendix accompanying this Certificate has been found to conform to the Quality Management System standard: IATF 16949:2016 This certificate is valid for the following scope: DESIGN AND MANUFACTURE OF PLASTIC COMPOUNDING MATERIAL EXCLUSION: NONE http://www.dnv.com Certificate no.: 273138-2018-AQ-RGC-IATF IATF Certificate No: 0558323 Place and date: Katy, TX, 10 December 2024 Lack of fulfilment of conditions as set out in the Certification Agreement may render this Certificate invalid.

Certificate Avient Corporation This is to certify that the Responsible Care Management System of: Avon Lake Corporate 33587 Walker Road Avon Lake OH 44012 United States (WITH ADDITIONAL FACILITIES LISTED ON ATTACHED ANNEX) has been assessed by ABS Quality Evaluations, Inc. and found to be in conformance with the requirements set forth by: The Responsible Care Management System is applicable to: CORPORATE SUPPORT ACTIVITIES, DESIGN, MANUFACTURE AND DISTRIBUTION OF COLOUR AND ADDITIVE CONCENTRATES, THERMOPLASTIC RESINS AND PELLETS, SPECIALTY COMPOUNDS AND COLORANTS. Certification structure: MULTI-SITE Certification Date: 29 SEP 2023 Effective Date: 27 FEB 2025 Expiration Date: 27 SEP 2026 Revision Date: 05 MAR 2025 Dominic Townsend, President Page 1 of 5 Avon Lake Corporate Responsible Care Corporate Support Activities in Sr.

Exhibit 31.1 CERTIFICATION I, Robert M. Patterson Exhibit 31.2 CERTIFICATION I, Bradley C. Exhibit 32.2 CERTIFICATION PURSUANT TO 18 U.S.C.

MSC Certificate Place and date: For the issuing office: Shanghai, 10 October 2024 DNV - Business Assurance Building 9, No. 1591 Hongqiao Road, Changning District, Shanghai, China 200336 Zhu Hai Ming Management Representative Lack of fulfilment of conditions as set out in the Certification Agreement may render this Certificate invalid. ACCREDITED UNIT: DNV Business Assurance B.V., Zwolseweg 1, 2994 LB, Barendrecht, Netherlands - TEL: +31(0)102922689. www.dnv.com/assurance MANAGEMENT SYSTEM CERTIFICATE Certificate no.: 3033-2006-AQ-RGC-RvA Initial certification date: 07 November 2018 Valid: 08 November 2024 – 07 November 2027 This is to certify that the management system of Polyone - Shenzhen Co., Ltd. No. 1, Qihang Industry Park, Haoxiang Road, Shajing Town, Baoan, Shenzhen, Guangdong, China 518104 has been found to conform to the Quality Management System standard: GB/T 19001-2016 / ISO 9001:2015 This certificate is valid for the following scope: Development and Manufacture of Masterbatch, Pigment Concentration, Plastisol; Manufacture of Plastic Compounding Material http://www.dnv.com/assurance 证书制作地点及日期: 证书认可签发机构: 上海, 2024年10月 10日 DNV - Business Assurance 中国上海市长宁区虹桥路1591号9号楼A座 邮编: 200336 电话: +86 21 32799000 朱海明 管理代表 未履行认证协议中规定条款会导致此证书失效，获证组织必须定期接受监督审核并经审核合格此证书方继续有效。

Exhibit 31.1 CERTIFICATION I, Robert M. Patterson Exhibit 31.2 CERTIFICATION I, Bradley C. Exhibit 32.2 CERTIFICATION PURSUANT TO 18 U.S.C.