Recovery from Strain and Shrinkage Measurements of Poly(m-methylene Terephthalate) and Poly(ethylene 2,6-Naphthalate) Fibers

Recovery from strain, tensile, and shrinkage are measured for poly(ethylene 2,6-naphthalate) (PEN), dimensionally stable polyester (DSP PET), and high tenacity polyester (HT PET). The results are considered in the contextof an earlier study examining the mechanical properties of poly(ethylene terephthalate) (2GT), poly(trimethylene terephthalate) (3GT), and poly(tetramethylene terephthalate) (4GT). DSP PET and PEN show good recovery from 10% applied strain, at 30% strain DSP PET has the highest recovery overall, and at 60% strain recovery is poor for all types. In the case of HT PET, specimen breakage sometimes occurs before the recovery measurement can be completed. PEN shows the minimum shrinkage in boiling water, and DSP PET is more dimensionally stable than HT PET. However, an interesting observation is that PEN develops a crimped appearance after this treatment, which is not seen in the other two fibers. We associate this with the good recovery behavior of PEN.