Pressure-volume-temperature data Amorphous polymers

Tables in this chapter contain published pressure-volume-temperature data for amorphous homopolymers. Measurements below the melting temperatures for semi-crystalline materials are not included because of the potentially large variance among samples with differing degrees of crystallinity. Rogers [1] and Zoller [2] have also compiled equation-of-state data for amorphous polymers.

In this case, the polymer differs from those in the preceding example since polyethylene is semicrystalline and not amorphous. The volumes can be determined by two different techniques. The first is to use available pressure-volume-temperature data (see Figs. 2-1-2-8). Another method is to calculate the volumes from an equation of state and the volume charge conelation of Chapter 2. 

Experimental data from our laboratories will be shown for an extensive series of amorphous polymers with glass transitions between Tg = 200 and 500 K. We discuss the temperature dependence of the hole-size distribution characterized by its mean and width and compare these dependencies with the hole fraction calculated from the equation of state of the Simha-Somcynsky lattice-hole theory from pressure-volume-temperature PVT) experiments [Simha and Somcynsky, 1969 Simha and Wilson, 1973 Robertson, 1992 Utracki and Simha, 2001]. The same is done for the pressure dependence of the hole free-volume. The free-volume recovery in densified, and gas-exposed polymers are discussed briefly. It is shown that the holes detected by the o-Ps probe can be considered as multivacancies of the S-S lattice. This gives us a chance to estimate reasonable values for the o-Ps hole density. Reasons for its... 

Experimentally it is found that AFis positive for relaxations in polymers so equation (37) shows that Qv < Qp if temperature of a material is raised at constant pressure, part of the decrease in is due to the increase in volume accompanying the increase in temperature. The effect of pressure can be very large for the primary (a) relaxation in amorphous polymers with (31n /5P)t lying in the range (1-5) x 10 atom" or can be extremely small, as found for the secondary () ) relaxation in amorphous polymers e.g. for poly(ethylene terephthalate) and poly(vinyl chloride)" ]. Use of data provides a test of theories for relaxation in the glass transition region (a process)." " ... 

The tables in Chapter 6 provide speeifie volumes neither at or below the melting transition of semieiystalline materials nor at or below the glass transition of amorphous samples, since PVT data of solid polymer samples are non-equihbrium data and depend on sample history and experimental procedure (which will not be diseussed here). Therefore, only equilibrium data for the liquid/molten state are tabulated. Their common accuracy (standard deviation) is about 0.001 cm /g in specific volume, 0.1 K in temperature and 0.005 P in pressure (1995ZOL). 

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