Pressure–volume–temperature of molten and glassy polymers

Abstract

The pressure–volume–temperature (PVT) dependencies of several amorphous polymers (PS, PC, PPE, and PPE/PS 1:1 blend) in the glassy and molten state were studied. The Simha–Somcynsky (S–S) lattice‐hole equation of state (EOS) was used. Fitting the PVT data in the molten state to the EOS yielded the free volume quantity, h = h(T, P), and the characteristic reducing parameters, P*, V*, and T*. The data within the glassy region were interpreted assuming that the latter parameters are valid in the molten and vitreous state, than calculating h = h(T, P) from the experimental values of V = V(T, P). Next, the frozen free volume fraction in the glass was computed as FF = FF(P). The FF values of polystyrene (PS) resins at ambient pressure showed little scattering (FFP=1 = 0.691 ± 0.008), while their P‐dependencies varied, reflecting the thermodynamic history of the glass formation as well as the PVT measurements protocol. The pressure gradient of Tg was compared with the Ehrenfest relation for the second‐order transition; here also agreement depended on the method of vitrification. The experimental values of FF at ambient pressure decreased with increasing values of the characteristic temperature reducing parameter, T*. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 270–285, 2007.

Pressure relaxation of polystyrene and its comparison to the shear response

“…This value is in agreement with values reported in the literature for polystyrene which range from 0.25 to 0.40 K/ MPa. [26][27][28][29][30][31][32] Also shown in Figure 1 are comparisons of our data to those of Oels and Rehage 33 and Quach and Simha. 22 Oels and Rehage used a lower molecular weight polystyrene (M w ¼ 20,400 g/mol, M w /M n ¼ 1.06); hence, their T g values are $ 7 K lower than ours at low pressures.…”

Equations of state for polyamide‐6 and its nanocomposites. 1. Fundamentals and the matrix

“…/ melt ) / cryst as ð100 À X cryst Þ=q melt ) X cryst =q cryst (13) However, because the argument holds equally well for a as for j , the observed different behavior must originate in the different effect of P and T on free volume and macromolecular configuration. For the molten state, this indeed was illustrated in Figures 1 and 2.…”

“…The molecular weight dependence of the characteristic parameters and L-J quantities was reported for PS. 30 It is noteworthy that the larger value of T*f o r1 0 2 2 Bm e a n s that in this polymer the free volume content (at the same P and T) is smaller than that in 1015B 13 ; this could be expected for higher molecular weight.…”

“…12 A number of eos has been proposed for molten polymer, and some have been extended to the vitreous state. 13 By contrast, a rigorous analysis of semicrystalline polymer PVT is difficult and rarely attempted.…”

Free volume dependence of polymer viscosity

“…6 and 7, without any apparent deviation. However, calculation of the compressibility parameter, K, demonstrated a dramatic change of K=K(T) dependence at T/T g =1.22 to 1.23 (Utracki 2006b). …”