The fracture toughness and fatigue crack propagation behaviour of annealed PET

The chemistry, manufacture and tensile behaviour of polyester fibers

“…Pecorini and Hertzberg [278] studied the effect of annealing and drying conditions on the fracture and fatigue behavior of PET and correlated their results qualitatively to the changes in the tie-molecule density. Gupta et al [117] monitored the structural changes occurring during elongation up to fracture of uniaxially drawn, heat-set PET film samples by rapid scanning Fourier transform infra-red (FTIR) spectroscopy and identified chain uncoiling (lamellar separation) in the amorphous regions and longitudinal slip in the crystalline regions as the main deformation mechanisms in these materials.…”

“…Any accidental local anisotropy in fibrous structure can lead to shear forces even under purely axial load, thus giving rise to longitudinal crack formation, which as a rule precedes the failure of the strained material. When the tie molecule density is low, the load transmitted through these links will produce brittle fracture [278].…”

Strain-rate dependence of the microstructure and mechanical properties for hot-air-drawn nylon 6 fibers

“…The original fiber showed a broad melting endotherm peaking at 221 °C, and the fibers drawn at 13.9 s −1 or less had almost the same T m as the original fiber. The melting peaks can be attributed to the melting of the FCC existing in the original fiber, to the melting of the crystals recrystallized during the DSC measurements, or both 21, 22. In the HA drawing carried out at the lower ε˙, the transformation of the FCC into the ECC during the drawing was incomplete, and the ECC transformed from the FCC had low levels of crystal perfection.…”

Roll-drawing and die-drawing of toughened poly(ethylene terephthalate). Part 1. Structure and mechanical characterization

“…Newman attempted to cold draw isotropic PET by tensile drawing but with no success [18]. At temperatures below the T g , the molecular chains are 'frozen-in' and thus, any stress applied to draw the polymer will be near the fracture stress of the material, which will result in premature fracture of the material by crazing and voiding [18][19][20][21]. Allison and Ward [22] also observed fracture when PET with crystallinity greater than 50% was cold drawn.…”