This study investigates the impact of free radicals present in polyetheretherketone (PEEK) on its interfacial adhesion with reinforcing fibers and the resulting crystal formation at the interphase. Microdroplet tests revealed that the interfacial shear strength between PEEK and carbon fiber (CF) was enhanced under increased preparation temperatures or prolonged holding times in the molten state, corresponding to an upsurge in PEEK radicals, elucidated by electron spin resonance and melt rheological behavior analyses. The post-microdroplet testing fracture surface and PEEK crystal structure near the fiber were investigated through micro-Raman spectroscopy under varying reinforcing fiber types and functional group concentrations (e.g., -OH and -COOH) on the CF surface. The results revealed that PEEK crystal formation along the CF axis at the interphase is driven by noncovalent interfacial interactions, such as π interactions and hydrogen bonds. Conversely, covalent interfacial interactions suppress crystal formation.

中文翻译：

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聚醚醚酮自由基对碳纤维界面相互作用及聚醚醚酮界面晶体形成的影响


本研究研究了聚醚醚酮 (PEEK) 中存在的自由基对其与增强纤维的界面粘合力以及由此产生的界面晶体形成的影响。微滴测试表明，在提高制备温度或延长熔融状态下的保持时间的情况下，PEEK 和碳纤维 (CF) 之间的界面剪切强度得到增强，这对应于 PEEK 自由基的激增，这一点通过电子自旋共振和熔体流变行为分析得到了阐明。在不同的增强纤维类型和 CF 表面官能团浓度（例如 -OH 和 -COOH）下，通过显微拉曼光谱研究了微滴测试后断裂表面和纤维附近的 PEEK 晶体结构。结果表明，PEEK 晶体在界面沿 CF 轴形成是由非共价界面相互作用驱动的，例如 π 相互作用和氢键。相反，共价界面相互作用抑制晶体形成。