Rate Of Physical Aging Research Articles

Physical aging studies of semicrystalline poly(ethylene terephthalate)

AbstractPhysical aging of semicrystalline poly(ethylene terephthalate) has been investigated as a function of crystalline content. Stress–strain, stress relaxation, and differential scanning calorimetry experiments were used to monitor the physical aging process. Both the overall extent and the rate of physical aging in this material decrease with increasing crystallinity. Several possible reasons for this behavior are advanced and discussed. It was also found that the drawing behavior of amorphous PET changes significantly as physical aging progresses. Specifically, for samples aged and then elongated, the extent of localized deformation (necking) and associated strain‐induced crystallization was greater for samples aged for longer periods of time.

Physical aging studies of styrene‐butadiene and carbonate‐siloxane block copolymers

AbstractThe physical aging process in styrene‐butadiene and carbonate‐siloxane block copolymers has been studied by monitoring the time dependent changes in mechanical and thermal properties. Specifically, stress‐strain, stress relaxation and differential scanning calorimetry experiments were utilized. For the styrene‐butadiene systems, it was found that the rate of physical aging increases with decreasing glassy content between 50 and 100 percent glass. However, the rate must decrease to zero when the percent glass reaches zero. The occurrence of physical aging was also noted in the carbonatesiloxane block copolymer investigated. The data are discussed in light of the practical ramification of utilizing these block copolymers in material applications.