Glass transition in semicrystalline polycarbonate

Abstract

The intensity of the glass transition in semicrystalline polycarbonate was measured by differential scanning calorimetry and by thermally stimulated discharge of electrets. Solution‐cast and bulk‐crystallized samples possessing widely varying crystallinities and morphologies were investigated. It is shown that the intensity of the glass transition is governed by the extent of primary crystallization and is a linear combination of intensities from the bulk amorphous regions and from noncrystalline polymer within semicrystalline aggregates such as spherulites. The intensity of the glass transition within spherulites is about 0.1–0.3 as great as that in bulk amorphous regions. A three‐phase model incorporating two distinct types of noncrystalline polycarbonate is proposed to account for the properties of this polymer.

The effect of crystallinity and crosslinking on the depression of the glass transition temperature in nylon 6 by water

“…A value for A q k was unobtainable at a degree of crystallinity a, 'v 23%. 20 This phenomenon was attributed to the presence of two types of noncrystalline material in this polymer; bulk amorphous regions, which are responsible for the observed incremental change in heat capacity, and surfacedominated intercrystalline regions within spherulites which do not contribute to this heat capacity change. From this it follows that at a degree of crystallinity of approximately 23% there are no bulk amorphous regions in semicrystalline polycarbonate.…”

Crystallization effects on autoclave foaming of polycarbonate using supercritical carbon dioxide

“…14 This is attributed to the lowering of the glass transition temperature, 15 through plasticization effects, which is expected to increase the crystallization rate accordingly. 16 Nevertheless, no crystallization was reported in experiments carried out at temperatures substantially below the intrinsic T g of polycarbonate, and nucleation of the cells was found to take place even at temperatures as low as 60…”

Blends of polycarbonate and acrylic polymers: Crystallization of polycarbonate

“…37,38,40 In the blends, the acrylic phase, i.e., either PMMA or NRPGI, acts as a diluent, and the final crystal- linity is a linear function of the PC concentration within experimental error (Fig. 7).…”

“…f is the average specific gravity of the fibrils; PCam is the specific gravity of amorphous PC (1.2 g/cm 3 ), 38,45 and PCcryst is the specific gravity of PC crystals (1.3 g/cm 3 ) 38 ; PCam,f ϭ 1 Ϫ clin Х 0.7 is the volume fraction of the interlamellar amorphous PC. 2) i ϭ 1.19 g/cm 3 , the specific gravity of PMMA.…”