Synergistic enhancement of PEEK bonding performance and thermal shock resistance through combined surface treatment

Polyetheretherketone (PEEK) is widely employed across various applications due to its exceptional properties; however, its chemical inertness and low surface energy result in poor bonding performance and susceptibility to failure under thermal shock. While single surface treatments prove inadequate for optimal bonding, and although previous studies have confirmed that combined approaches enhance PEEK’s bonding strength, a systematic comparison and mechanistic understanding of different treatment combinations remain lacking. This study investigated the effects on PEEK’s bonding performance and thermal shock resistance using pairwise combinations of sulfonation etching, plasma treatment, and a catechol-based prepolymer coating, all applied with mechanical wiping. Results demonstrated that the combined sulfonation and plasma treatment produced a composite interface with nanoscale pits and polar functional groups, integrating mechanical interlocking and chemical bonding. This yielded a high room-temperature bonding strength of 4.18 MPa—a 736 % increase over untreated-PEEK—yet after 32 thermal shock cycles (−78.5 °C to 120 °C), the strength decreased by 25.36 %. In contrast, the plasma and catechol-based prepolymer coating combination formed an interfacial transition layer. Although its initial strength was 3.74  MPa, it showed no degradation after identical cycling, indicating superior thermal shock resistance. This study confirms, for the first time, the effectiveness of combined treatments in enhancing bonding durability under extreme thermal cycling. It further reveals that a coating-buffered interface maintains durability more effectively than one relying solely on direct adhesive-substrate contact. These insights offer valuable guidance for designing interfaces of difficult-to-bond polymers like PEEK in demanding environments, including aerospace applications.