A master curve for tensile properties of thermoplastics

✍ Scribed by Hans-G. Elias

• Book ID: 102940283
• Publisher: John Wiley and Sons
• Year: 1994
• Tongue: English
• Weight: 734 KB
• Volume: 195
• Category: Article
• ISSN: 1022-1352
• DOI: 10.1002/macp.1994.021950910

✦ Synopsis

Abstract

Ultimate mechanical properties of polymers can be characterized by a dimensionless Hooke number He ≡ σ~b~/(E__ϵ~b~), where σ~b~ is the ultimate tensile strength, E the tensile modulus, and ϵ~b~ the elongation at break. Hooke numbers are found to be a smooth function of ultimate elongations, independent of the chemical and physical structure of common thermoplastics. This master curve for fracture strengths and elongations can be described by He = [1 + (ϵ~b~/ϵ~crit~)^ab^__]^−1/b^ with empirically found parameters ϵ~crit~ = 0,0168, a = 0,918, and b ≈ 4. The decrease of He with increasing ϵ~b~ at ϵ~b~ > ϵ~crit~ reflects the shear flow on deformation. Hooke numbers depend on entanglement densities v~e~ according to He = 1,285·10^36^ (v~e~/cm^−3^)^−1,846^ for v~e~ > 3,65·10^19^ cm^−3^. A correction for additional segment orientation during tensile testing brings the exponent to −1,846/0,918 = −2,01; i. e., a dependence of Hooke numbers on the reciprocal square of entanglement densities.