Physical Aging Of Poly Research Articles

Free volume and physical aging of poly(vinyl acetate) studied by positron annihilation

Etude en fonction de la temperature et de la duree de vieillissement; determination du volume moyen des vides V F a partir de la duree de vie de l'orthopositronium a l'aide de l'equation de Nakanishi. La variation avec la temperature du produit de V F avec l'intensite I 3 de l'orthopositronium est en accord avec la fraction de volume libre h calculee a partir des donnees d'equation d'etat via la theorie de Simha. Variation avec le temps de l'intensite I 3 proportionnellement plus grande que la duree de vie de l'orthopositronium

Physical aging of poly(methyl methacrylate) in the nonlinear range: Torque and normal force measurements

AbstractCylindrical specimens of poly(methyl methacrylate) (PMMA) were quenched from above the glass transition and subsequently tested in torsion. Torque and normal‐force relaxation responses were recorded simultaneously. The experiments were performed at 40, 60, and 80°C, at increasing aging times and at deformations ranging from γ = 0.0027 to γ = 0.074. It was found at 40 and 60°C, that, contrary to the classical picture of aging, the small‐deformation torque‐relaxation curves could not be superposed by any combination of vertical and horizontal shifts. On the other hand, at 80°C, and in the nonlinear deformation range even at lower temperatures, the relaxation curves are superimposable simply by horizontal shifts, but as γ increases they involve decreasing values of the double‐logarithmic shift rate. At the same deformation level, however, the shift rate for the normal force is significantly higher than is that for the torque over most of the γ range investigated.

Physical aging of poly(acrylonitrile‐butadiene‐styrene). I. Dynamic mechanical measurements

AbstractInjection‐ and compression‐molded poly(acrylonitrile–butadiene–styrene) (ABS) samples were aged at 40 to 90°C in a nitrogen atmosphere. Dynamic mechanical measurements show that aging restricts molecular mobility in the glassy poly(styrene–acrylonitrile) matrix of ABS. The α, or glass transition, of the matrix is affected only by aging at higher temperatures such as 90°C. On the other hand, the β transition is suppressed to some extent by aging at all temperatures from 40 to 90°C parallels the loss of tensile elongation previously reported. These results indicate that the effects of aging on the glassy phase are unique for different aging temperatures. Therefore, a simple time temperature superposition may not exist for the effects of physical aging on ABS.