Life-stage Analysis of Solvent Induced Fissures under Static Stress in PET Fibers

Abstract

Abstract The paper discusses the impact of drawing poly(ethylene terephthalate) (PET) fibers in the presence of solvents, which consist of the first five homologues of aliphatic primary alcohols, namely methanol to amyl alcohol. The solvent induced deformation under tensile load leads to surface fissures characterized by four stages: fissure formation (birth), incipient draw (neck formation), partial draw, and full draw. This process results in internal void formation in the presence of a propagating neck. A design of experiment (DOE) was performed to screen out the process parameters critical for understanding surface fissure formation. Four process parameters were investigated: initial material properties (orientation); environment of draw (i.e. type of alcohols used as solvent); rate of extension; and amount of extension. The response of solvent induced deformation were characterized by the natural draw force reduction; number of fissures formed at time of birth, fissure width at time of formation, and neck angle. Of all the four process parameters involved, the analysis indicates that the material properties and amount of extension were the best predictors of solvent induced fissure formation. Organic solvents reduce the tension required for draw and create internal voids, a porous network, with possibly the penetrant being “sucked” into the interior of PET fibers drawn in the presence of alcohols.