Equations of state for polyamide‐6 and its nanocomposites. II. Effects of clay

Abstract

The pressure-volume-temperature (PVT) dependencies of polyamide-6 and its nanocomposites (polymeric nanocomposites) were measured at temperatures T ¼ 300-600 K and pressures P ¼ 0.1-190 MPa, thus spanning the range of molten and ''solid'' phases. The Simha-Somcynsky (S-S) cell-hole equation of state (EOS) was used for describing the molten region. At T g (P)T T m (P), the ''solid'' phase is a mixture of the liquid polyamide-6 with dispersion of crystals. Accordingly, the PVT behavior in this region was described as a combination of the S-S EOS for the liquid phase and the Midha-Nanda-Simha-Jain (MNSJ) EOS for the crystalline one. These two theories based on different models yielded two sets of the characteristic reducing parameters, P * , T * , V * and the segmental molecular weight, M s . Incorporation of 2 and 5 wt % clay increased P * and reduced T * and V * , but the effects were small. Fitting the combination of S-S and MNSJ EOS' to isobaric ''solid'' phase data yielded the total crystallinity, X cryst , and the correcting excess specific volume, DV m,c . Both parameters were sensitive to pressure, P, and the clay content, w-the former increased with P and w, whereas the latter decreased. The raw PVT data were numerically differentiated to obtain the thermal expansion and compressibility coefficients, a and j, respectively. At T \ T m , addition of clay reduced their relative magnitude, whereas at T [ T m , the opposite effect was observed, most likely owing to the excess of intercalant in the polymeric nanocomposites samples. V V C 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: [966][967][968][969][970][971][972][973][974][975][976][977][978][979][980] 2009

Free Volume in Molten and Glassy Polymers and Nanocomposites

“…It is evident that compressibility is a bit affected by clay; it is reduced in solid and increased in the molten state. Characteristically, as predicted by theory, the isobaric values of κ follow nearly the same dependence on both sides of the melting zone [Utracki, 2009].…”

PVT of amorphous and crystalline polymers and their nanocomposites

“…À5 and À10% for PNC-2 and -5, respectively. At high P the k R / 1, i.e., kðPNCÞxkðPA À 6Þ [37]. Thus, it is evident that khðvlnV=vPÞ T depends mainly of the molten polymer content.…”

“…The experimental details and discussions may be found in [8,9,26,36,37]. The PVT data of the melts was fitted to Eqs.…”

“…Since in the studied PA-6 based systems T g z 316 AE 1 K and the dilatometric measurements start at ca. 300 K, the semicrystalline region was (2009) 1-11 7 treated as a mixture of molten organic phase and dispersed in it PA-6 crystals (increasing with P from X cryst ¼ 15-40 wt%) and 0, 2.3 or 4.9 wt% clay [36,37]. The equilibrium crystallinity of PA-6 is X eq:cryst y29 À 31% [56][57][58].…”

“…For PS and its CPNC the effects of T, w and P on a is shown in Table 3 Characteristic parameters of PA-6 computed from the MNSJ theory fitted to the crystalline region I and from the S-S eos fitted to the molten region III [37]. 15.6 ± 0.2 32.0 ± 0.1 Fig.…”