Influence of molecular weight on rheological, thermal, and mechanical properties of PEEK

Abstract

This study focuses on the influence of molecular weight on the rheological, thermal, and mechanical behavior of poly(ether‐ether‐ketone) (PEEK), a semicrystalline high‐performance polymer. The results show that the molecular weight of PEEK has significant influence on its rheological, thermal, and mechanical behavior. It was found that PEEK has the unique characteristic of two shear‐thinning regions. The shear viscosity and the stress relaxation time of PEEK increase significantly as molecular weight increases. In general, the Cox‐Merz rule is valid for all grades of PEEK. As molecular weight increases, the melting temperature of PEEK decreases slightly, but its isothermal and nonisothermal crystallization temperatures drop dramatically. As molecular weight increases, the crystallinity, the crystallization rate, and the magnitude of crystallization activation energy decrease. The crystallization kinetics study indicates that PEEK tends to form spherical crystalline structures, regardless of its molecular weight. As molecular weight increases, the tensile strength at yield, the tensile modulus, and the flexural modulus of PEEK decrease slightly, whereas the tensile strength at break, the tensile strain at break, the modulus of toughness, and the impact strength of PEEK increase significantly. POLYM. ENG. SCI., 2011. © 2010 Society of Plastics Engineers

Structural and Thermo-mechanical Evaluation of Two Engineering Thermoplastic Polymers in Contact with Ethanol Fuel from Sugarcane

“…The main chain relaxation of the PEEK, taken at the maximum of tan δ, occurs at 165.5 °C, as shown in Figure 3, similar to values reported in the literature 6,11,16 . This high relaxation temperature for the PEEK polymeric structure is associated with the rigid segments of its backbone, as reported by Yuan et al 16 and White et al 20 .…”

“…This high relaxation temperature for the PEEK polymeric structure is associated with the rigid segments of its backbone, as reported by Yuan et al 16 and White et al 20 . On the other hand, the flexible chains of the PA-11 can explain its T g value of 13.6 °C (Figure 3), similar to values reported by Chaupart and Serpe 23 , and is associated with the long segments between the amide groups and the significant amount of plasticizer present in this particular grade.…”

“…The curves were obtained in a Q 8000 apparatus (Perkin Elmer) under a nitrogen atmosphere. The temperature range was from 25 to 400 °C for PEEK and 25 to 250°C for PA-11, both with a 10 °C min (enthalpy of fusion of 100% crystalline polymer) tabulated as 130 and 226 J g -1 for PEEK 11,16 and PA-11 31 , respectively. The thermal stability of the PEEK and PA-11 was analyzed using TGA (Q500, TA Instruments).…”

“…It has high glass transition (T g ≈ 145 °C) and melting (T m = 340 °C) temperatures and has been discussed in the literature since the 1980s 6,[11][12][13][14][15][16] . It can be subjected to a variety of processing routes, has high chemical resistance to many solvents and is employed in a variety of engineering applications (e.g., aerospace, automotive and chemical industries) [17][18][19][20][21][22] .…”

Flow-Induced Crystallization of PEEK: Isothermal Crystallization Kinetics and Lifetime of Flow-Induced Precursors during Isothermal Annealing

“…That would mean the Rouse time of the longest chains is τ R = 0.17 s and, combined with their reptation time of τ d ≈ 10 s, suggests that those longest chains have M/M e = τ d /6τ R = 10 entanglements. Yuan et al (2011) reported two distinct shear thinning regions in the flow curves of different grades of PEEK at 380°C…”