{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,6,8]],"date-time":"2026-06-08T17:02:07Z","timestamp":1780938127617,"version":"3.54.1"},"reference-count":38,"publisher":"MDPI AG","issue":"12","license":[{"start":{"date-parts":[[2026,6,8]],"date-time":"2026-06-08T00:00:00Z","timestamp":1780876800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Polymers"],"abstract":"<jats:p>The Successive Self-Nucleation and Annealing (SSA) technique is a thermal fractionation method that involves subjecting a polymer sample to sequential self-nucleation and annealing steps at progressively decreasing temperatures, using differential scanning calorimetry (DSC). Since its introduction in the late 1990s, SSA has been widely applied to study the molecular structure of polymers with structural irregularities, including highly branched or crosslinked polyethylenes and random copolymers. However, the use of SSA for medical-grade ultra-high-molecular-weight polyethylene (UHMWPE), a highly linear homopolymer with minimal defects, has not yet been explored. This study aims to evaluate both its applicability to biomedical UHMWPE and its ability to reveal morphological differences among commercially available formulations. Several biomedical UHMWPE formulations, including conventional, highly cross-linked, and \u03b1-tocopherol-stabilized materials, were characterized by micro-FTIR, gel fraction and cross-link density measurements and subsequently subjected to SSA thermal fractionation. The results show that ram extrusion induces entanglements that act as interruptions in the otherwise linear chain structure, thereby enabling thermal fractionation: more than 80% of the crystalline fraction of ram-extruded UHMWPE is composed of three crystal populations melting at approximately 135, 132, and 126 \u00b0C, accompanied by four additional minor fractions at progressively lower melting temperatures. Gamma irradiation followed by thermal treatments significantly modifies the fractionation behavior, leading to the formation of an additional population of high-melting crystallites as evidenced by an increase in the number of melting peaks from 7 to 8. Oxidative degradation of highly crosslinked and annealed UHMWPE increases crystallinity by approximately 11% relative to its unoxidized counterpart but reduces the ability of the material to undergo thermal fractionation, decreasing the number of melting peaks. In contrast, the addition of low concentrations of \u03b1-tocopherol does not significantly influence the fractionation behavior. These findings demonstrate that thermal fractionation of medical-grade UHMWPE is feasible and that SSA is an effective tool for detecting morphological differences among formulations.<\/jats:p>","DOI":"10.3390\/polym18121428","type":"journal-article","created":{"date-parts":[[2026,6,8]],"date-time":"2026-06-08T16:25:16Z","timestamp":1780935916000},"page":"1428","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["Successive Self-Nucleation and Annealing for the Characterization of Biomedical Ultra-High-Molecular-Weight PolyEthylene (UHMWPE) Formulations"],"prefix":"10.3390","volume":"18","author":[{"ORCID":"https:\/\/orcid.org\/0009-0002-6160-2112","authenticated-orcid":false,"given":"Luca","family":"Gianoglio","sequence":"first","affiliation":[{"name":"Department of Chemistry, University of Torino, Via Pietro Giuria 7, 10125 Turin, Italy"},{"name":"SUSPLAS@UniTo, Sustainable Plastic Scientific Hub, University of Torino, Via Pietro Giuria 7, 10125 Turin, Italy"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Matteo","family":"Righetti","sequence":"additional","affiliation":[{"name":"Department of Chemistry, University of Torino, Via Pietro Giuria 7, 10125 Turin, Italy"},{"name":"SUSPLAS@UniTo, Sustainable Plastic Scientific Hub, University of Torino, Via Pietro Giuria 7, 10125 Turin, Italy"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-7074-9859","authenticated-orcid":false,"given":"Marco","family":"Zanetti","sequence":"additional","affiliation":[{"name":"Department of Chemistry, University of Torino, Via Pietro Giuria 7, 10125 Turin, Italy"},{"name":"SUSPLAS@UniTo, Sustainable Plastic Scientific Hub, University of Torino, Via Pietro Giuria 7, 10125 Turin, Italy"},{"name":"NIS Interdepartmental Centre, University of Torino, 10125 Turin, Italy"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-0477-2086","authenticated-orcid":false,"given":"Pierangiola","family":"Bracco","sequence":"additional","affiliation":[{"name":"Department of Chemistry, University of Torino, Via Pietro Giuria 7, 10125 Turin, Italy"},{"name":"SUSPLAS@UniTo, Sustainable Plastic Scientific Hub, University of Torino, Via Pietro Giuria 7, 10125 Turin, Italy"},{"name":"NIS Interdepartmental Centre, University of Torino, 10125 Turin, Italy"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2026,6,8]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","unstructured":"Bracco, P., Bellare, A., Bistolfi, A., and Affatato, S. (2017). Ultra-High Molecular Weight Polyethylene: Influence of the Chemical, Physical and Mechanical Properties on the Wear Behavior. A Review. Materials, 10.","DOI":"10.3390\/ma10070791"},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"98","DOI":"10.1016\/j.jor.2021.04.004","article-title":"Ultra-High Molecular Weight Polyethylene (UHMWPE) for Hip and Knee Arthroplasty: The Present and the Future","volume":"25","author":"Bistolfi","year":"2021","journal-title":"J. Orthop."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"433","DOI":"10.1016\/j.jmbbm.2008.12.006","article-title":"Ultra High Molecular Weight Polyethylene: Mechanics, Morphology, and Clinical Behavior","volume":"2","author":"Sobieraj","year":"2009","journal-title":"J. Mech. Behav. Biomed. Mater."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"1371","DOI":"10.1016\/S0142-9612(98)00013-1","article-title":"In Vivo UHMWPE Biodegradation of Retrieved Prosthesis","volume":"19","author":"Costa","year":"1998","journal-title":"Biomaterials"},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"340","DOI":"10.1302\/0301-620X.80B2.0800340","article-title":"Quantitative Comparison of Wear Debris from UHMWPE That Has and Has Not Been Sterilised by Gamma Irradiation","volume":"80","author":"Besong","year":"1998","journal-title":"J. Bone Jt. Surg. Br."},{"key":"ref_6","doi-asserted-by":"crossref","unstructured":"Kurtz, S.M. (2009). Mechanisms of Crosslinking, Oxidative Degradation and Stabilization of UHMWPE. UHMWPE Biomaterials Handbook, Elsevier.","DOI":"10.1016\/B978-0-12-374721-1.00017-1"},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"157","DOI":"10.1002\/jor.1100170203","article-title":"Development of an Extremely Wear-resistant Ultra High Molecular Weight Polythylene for Total Hip Replacements","volume":"17","author":"McKellop","year":"1999","journal-title":"J. Orthop. Res."},{"key":"ref_8","doi-asserted-by":"crossref","unstructured":"Kurtz, S.M. (2004). The Origins of UHMWPE in Total Hip Arthroplasty. The UHMWPE Handbook, Elsevier.","DOI":"10.1016\/B978-012429851-4\/50005-X"},{"key":"ref_9","first-page":"17","article-title":"Comparison of the Properties of Annealed Crosslinked (Crossfire) and Conventional Polyethylene as Hip Bearing Materials","volume":"61","author":"Kurtz","year":"2002","journal-title":"Bull. Hosp. Jt. Dis."},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"253","DOI":"10.1097\/01.blo.0000093004.90435.d1","article-title":"Effect of Radiation, Heat, and Aging on In Vitro Wear Resistance of Polyethylene","volume":"417","author":"Muratoglu","year":"2003","journal-title":"Clin. Orthop. Relat. Res."},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"1980","DOI":"10.1016\/j.biomaterials.2005.10.002","article-title":"The Effect of Real-Time Aging on the Oxidation and Wear of Highly Cross-Linked UHMWPE Acetabular Liners","volume":"27","author":"Wannomae","year":"2006","journal-title":"Biomaterials"},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"89","DOI":"10.1016\/S0141-3910(00)00094-X","article-title":"Improving Synthetic Hindered Phenol Antioxidants: Learning from Vitamin E","volume":"70","author":"Breese","year":"2000","journal-title":"Polym. Degrad. Stab."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"2155","DOI":"10.1016\/j.polymdegradstab.2007.02.023","article-title":"Stabilisation of Ultra-High Molecular Weight Polyethylene with Vitamin E","volume":"92","author":"Bracco","year":"2007","journal-title":"Polym. Degrad. Stab."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"549","DOI":"10.1002\/jbm.a.32122","article-title":"Trace Concentrations of Vitamin E Protect Radiation Crosslinked UHMWPE from Oxidative Degradation","volume":"90","author":"Kurtz","year":"2009","journal-title":"J. Biomed. Mater. Res. A"},{"key":"ref_15","doi-asserted-by":"crossref","unstructured":"Kurtz, S.M. (2016). Mechanisms of Cross-Linking, Oxidative Degradation, and Stabilization of UHMWPE. UHMWPE Biomaterials Handbook, Elsevier.","DOI":"10.1016\/B978-0-323-35401-1.00003-X"},{"key":"ref_16","doi-asserted-by":"crossref","first-page":"215","DOI":"10.1007\/s00264-010-1161-y","article-title":"Vitamin E Diffused, Highly Crosslinked UHMWPE: A Review","volume":"35","author":"Oral","year":"2011","journal-title":"Int. Orthop."},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"2286","DOI":"10.1007\/s11999-010-1717-6","article-title":"Vitamin E-Stabilized UHMWPE for Total Joint Implants: A Review","volume":"469","author":"Bracco","year":"2011","journal-title":"Clin. Orthop. Relat. Res."},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"1859","DOI":"10.1007\/s00402-020-03358-x","article-title":"Vitamin E-Blended Highly Cross-Linked Polyethylene Liners in Total Hip Arthroplasty: A Randomized, Multicenter Trial Using Virtual CAD-Based Wear Analysis at 5-Year Follow-Up","volume":"140","author":"Busch","year":"2020","journal-title":"Arch. Orthop. Trauma. Surg."},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"465","DOI":"10.1007\/s002890050174","article-title":"Successive Self-Nucleation\/Annealing (SSA): A Novel Technique to Study Molecular Segregation during Crystallization","volume":"39","author":"Arnal","year":"1997","journal-title":"Polym. Bull."},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"559","DOI":"10.1016\/j.progpolymsci.2005.03.001","article-title":"Thermal Fractionation of Polymers","volume":"30","author":"Arnal","year":"2005","journal-title":"Prog. Polym. Sci."},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"2542","DOI":"10.1021\/acsapm.5c04486","article-title":"Novel Applications of Successive Self-Nucleation and Annealing Thermal Fractionation for Polymer Characterization","volume":"8","year":"2026","journal-title":"ACS Appl. Polym. Mater."},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"669","DOI":"10.1007\/s10973-010-1124-y","article-title":"Use of the Successive Self-Nucleation and Annealing Technique to Characterize 60Co Gamma Irradiated HDPEs","volume":"103","author":"Prin","year":"2011","journal-title":"J. Therm. Anal. Calorim."},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"e202401926","DOI":"10.1002\/chem.202401926","article-title":"Improving Environmental Stress Cracking Resistance of High-Density Polyethylene Grades by Comonomer Addition and Nanocomposite Approach","volume":"30","author":"Mansouri","year":"2024","journal-title":"Chem.\u2014A Eur. J."},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"56","DOI":"10.1007\/s10965-019-1715-7","article-title":"Chain Structure Comparison of Two Low Density Polyethylene Resins Fractionated by Temperature Rising Elution Fractionation and Thermal Fractionation","volume":"26","author":"Li","year":"2019","journal-title":"J. Polym. Res."},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"84","DOI":"10.1007\/s10965-022-02888-9","article-title":"Design of Molecular Structure for Commercial Polyethylene 100 Pipe","volume":"29","author":"Wang","year":"2022","journal-title":"J. Polym. Res."},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"1639","DOI":"10.1016\/j.polymdegradstab.2009.07.002","article-title":"The Use of SSA Fractionation to Detect Changes in the Molecular Structure of Model Ethylene\u2013Butene Copolymers Modified by Peroxide Crosslinking","volume":"94","author":"Villarreal","year":"2009","journal-title":"Polym. Degrad. Stab."},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"521","DOI":"10.1007\/s00396-021-04925-3","article-title":"Crystallization Behavior and Structure of Metallocene Polyethylene with Long-Chain Branch","volume":"300","author":"Wang","year":"2022","journal-title":"Colloid. Polym. Sci."},{"key":"ref_28","unstructured":"(2017). Guide for Evaluating the Extent of Oxidation in Polyethylene Fabricated Forms Intended for Surgical Implants (Standard No. ASTM F2102-17)."},{"key":"ref_29","unstructured":"(2016). Test Methods for Determination of Gel Content and Swell Ratio of Crosslinked Ethylene Plastics (Standard No. ASTM D2765-16)."},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"717","DOI":"10.1016\/S0142-9612(01)00176-4","article-title":"Gradient Crosslinking of UHMWPE Using Irradiation in Molten State for Total Joint Arthroplasty","volume":"23","author":"Muratoglu","year":"2002","journal-title":"Biomaterials"},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"132","DOI":"10.1016\/j.eurpolymj.2015.01.015","article-title":"Successive Self-Nucleation and Annealing (SSA): Correct Design of Thermal Protocol and Applications","volume":"65","author":"Michell","year":"2015","journal-title":"Eur. Polym. J."},{"key":"ref_32","doi-asserted-by":"crossref","first-page":"39","DOI":"10.1002\/macp.200500437","article-title":"High Speed SSA Thermal Fractionation and Limitations to the Determination of Lamellar Sizes and Their Distributions","volume":"207","author":"Lorenzo","year":"2006","journal-title":"Macromol. Chem. Phys."},{"key":"ref_33","doi-asserted-by":"crossref","first-page":"5328","DOI":"10.1021\/acs.macromol.5b00618","article-title":"Mechanisms of Chain Reentanglement during the Sintering of UHMWPE Nascent Powder: Effect of Molecular Weight","volume":"48","author":"Deplancke","year":"2015","journal-title":"Macromolecules"},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"129037","DOI":"10.1016\/j.polymer.2025.129037","article-title":"Tuning Chain Entanglement Density in UHMWPE via Sintering: Crystallization Suppression and Cryogenic Toughening Mechanism","volume":"338","author":"Wang","year":"2025","journal-title":"Polymer"},{"key":"ref_35","doi-asserted-by":"crossref","first-page":"441","DOI":"10.1002\/jbm.b.32805","article-title":"In Vivo Oxidation in Retrieved Highly Crosslinked Tibial Inserts","volume":"101","author":"Currier","year":"2013","journal-title":"J. Biomed. Mater. Res. B Appl. Biomater."},{"key":"ref_36","doi-asserted-by":"crossref","first-page":"1741","DOI":"10.1016\/0142-9612(95)00349-5","article-title":"Gamma Sterilization of UHMWPE Articular Implants: An Analysis of the Oxidation Problem","volume":"17","author":"Premnath","year":"1996","journal-title":"Biomaterials"},{"key":"ref_37","doi-asserted-by":"crossref","first-page":"490","DOI":"10.1016\/j.polymdegradstab.2012.12.011","article-title":"Abiotic Degradation of LDPE and LLDPE Formulated with a Pro-Oxidant Additive","volume":"98","author":"Arnal","year":"2013","journal-title":"Polym. Degrad. Stab."},{"key":"ref_38","doi-asserted-by":"crossref","first-page":"3643","DOI":"10.1016\/j.biomaterials.2010.01.076","article-title":"Use of Vitamin E to Protect Cross-Linked UHMWPE from Oxidation","volume":"31","author":"Lerf","year":"2010","journal-title":"Biomaterials"}],"container-title":["Polymers"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/2073-4360\/18\/12\/1428\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2026,6,8]],"date-time":"2026-06-08T16:34:05Z","timestamp":1780936445000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/2073-4360\/18\/12\/1428"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2026,6,8]]},"references-count":38,"journal-issue":{"issue":"12","published-online":{"date-parts":[[2026,6]]}},"alternative-id":["polym18121428"],"URL":"https:\/\/doi.org\/10.3390\/polym18121428","relation":{},"ISSN":["2073-4360"],"issn-type":[{"value":"2073-4360","type":"electronic"}],"subject":[],"published":{"date-parts":[[2026,6,8]]}}}