Sorption of water vapour by atactic and isotactic poly (methyl methacrylate)

Sorption of water vapor by poly(vinyl acetate)

“…In a previous paper (1) we found that the abnormality in sorption property of water vapor by atactic and isotactic poly(methyl methacrylate) could not be explained by the magnitude of crystallinity, but that it could be explained by studying the relationship of glass transition temperature (Tg)variation of the polymer with the increase in the quantity of water vapor sorbed by the polymer. There are two cases in the decrease in Tg of a polymer due to the sorption of low-molecular weight vapors by a polymer.…”

“…There are two cases in the decrease in Tg of a polymer due to the sorption of low-molecular weight vapors by a polymer. One (2) is where, as known by the sorption of water vapor by a water-soluble polymer, the decrease in Tg due to the increase in the moisture content becomes rapid at higher concentration, and the other (1) is where the decrease in Tg of a polymer becomes slow as known by the sorption of water vapor by a hydrophobic polymer. This study, using a hydrophobic polymer, poly(vinyl acetate) (PVAc), aimed at establishing the sorption mechanism of water vapor by the polymer near Tg by investigating the relationship of the sorption property of water vapor by the polymer with Tg variation due to the increase in the moisture content.…”

The Entropic Mechanism of Water Solvation of Polymers

“…(2) with coefficients: To = 3 0 T , aoo = O.O24g/g, E = 1755 Jimol, n = 0.7, a = 6.3 x grad-'. Their curvature is a little lower than that of a-PMMA samples from the work [24] (30"C), which possess coefficients aoo = 0.023 gig, E = 1300 J/mol, n = 0.7. Isotactic PMMA films [24] (possessing coefficients aoo = 0.06 g/g, E = 750 Jimol, n = 0.6) differ from a-PMMA by higher expressed S-like form and increased absorption, although it contains 76% of the crystalline phase.…”

“…Their curvature is a little lower than that of a-PMMA samples from the work [24] (30"C), which possess coefficients aoo = 0.023 gig, E = 1300 J/mol, n = 0.7. Isotactic PMMA films [24] (possessing coefficients aoo = 0.06 g/g, E = 750 Jimol, n = 0.6) differ from a-PMMA by higher expressed S-like form and increased absorption, although it contains 76% of the crystalline phase. S-like isotherms are also displayed by more hydrophilic polymers from the sequence of moderately hydrophilic ones: Nylon-6 [5] (coefficients of Eq.…”

The effect of moisture absorption on the thermomechanical properties of particulates

“…This kind of dependence may be caused by many factors, such as interaction between the composite and the penetrant [41][42][43][44][45][46][47][48], voids in the composite [49][50][51][52][53] and clustering of the penetrant in the polymer [39,[54][55][56][57][58]. Microvoids or microcracks developed due to swelling, stresses induced by the sorbed moisture, craze cavitation, formation of water clusters and high surface tensile stresses resulting from temperature and moisture gradients are also factors of predominant importance for anomalous diffusion in epoxy composites [59,60].…”