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A random distribution of relaxation/retardation rate constants is derived and incorporated into the thermodynamic theory of strength of imperfect (real) polymer fibers, which is used to analyze empirical polyethylene (fiber) strength data. The results, weighted equally with previous results, give for the perfect polyethylene fiber — the only unique reference state — at 25°C: σc(strength)≈7.5GPa,Kc(modulus)≈325GPa,ε...
The thermodynamic fusion theory of strength of perfect polymer fibers of finite molecular weight is extended to include imperfect (i.e. real) fibers of incomplete crystallinity and orientation. Approximate equations for failure strength, strain, and work of failure are derived by extracting from the real visco-elastic fiber an equivalent reversible component suitable for thermodynamic analysis. This...
Ultimate mechanical properties of polyethylene fibers were measured. Results are in close agreement with the stress-induced melting theory of fracture (for finite molecular weight polymers). The perfect fiber work of rupture Wc, modulus Kc, strength σc, and strain εc are found to be Wc=0.084±0.003GPa; σc=7.5GPa; Kc=335±12GPa; εc=0.0225±0.0005. The activation energy of fracture is measured as ≈108kJ/mol—the...
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