Poly Thermal expansion coefficient

Figure 15.24 shows the fabrication process of the optical filter on a fluorinated polyimide substrate. First, the low-thermal-expansion-coefficient PMDA/TFDB poly(amic acid) solution was spin-coated onto a Si substrate and baked. Then alternate TiO2 and SiO2 layers were formed on the polyimide film by ion-assisted deposition. The multilayered polyimide film was diced and peeled off from the Si substrate. In this way, thin optical filters on a fluorinated polyimide substrate are easily fabricated. 

As was already stated (see Figure 6), the temperature dependence of the shift factor aT is a function of the elastomer phase content. The strong effect of the rubber content on the temperature dependence of the shift factor aT could be explained by an increase in free volume of the SAN resin induced by the elastomer phase, as was suggested by Prest and Porter (13) for polystyrene-poly (phenylene oxide) blends. In order to verify this hypothesis, log aT experimental data for SAN and relative blends were used to calculate the WLF parameters and, in turn, the free volumes (f0) at the reference temperature (T0) and the thermal expansion coefficients (a) by the equation ... 

Fig. 6.1. The thermal expansion coefficient a of ice as determined for poly-crystalline samples by Jakob Erk (1928), — for single crystals by Hamblin...

FIGURE 10 Glass transition temperature from change of thermal expansion coefficient in isobaric V-T diagram for random copolymer poly(ethylene-co-vinyl alcohol) with 44 mol% of ethylene, data after Funke et al. (2007). 

The first application we will discuss in this section is the influence of the pure component properties (basically the volumetric properties) on the phase behavior in a mixture of two homopolymers. A mixture for which all necessary information is available(7,10) is the mixture of Polystyrene(PS) with the Poly(vinyl methyl ether)(PVME). Scaling constants for PS are obtained from Reference 7 while scaling constants for PVME and binary parameters are obtained from Reference 10. In Figure 1 is shown the influence of the thermal expansion coefficient a of PS on the spinodal curve of the mixture of PS and PVME considered both monodisperse with molecular weight 51000. As shown in the Figure a small increase in the thermal expansion coefficient of PS of the order of 1 % enhances the compatibility of PS with PVME by raising the spinodal curve and the critical temperature by about 30 degrees. 

Starting from some initial equilibrium state I (Vi, Tf), a polymer (e.g., poly (vinyl acetate)) is suddenly cooled down to a lower temperature Tf. We examine in which way the sample relaxes to its equilibrium state F (Vf, Tf). When the sample is suddenly cooled to Tf, the volume of the sample will usually not assume the value of the final state F, rather it will first go through some intermediate state M (V, Tf). Here Vm is normally not the same as Vf and can be determined by V = Vg[l+ag (T-Tg)], where Vg is the volume at the glass-transition temperature T g and a g the thermal expansion coefficient of the glass state. Since the state M is not an equilibrium state, and therefore, it will relax towards its equilibrium state F. Our interest here is to examine the kinetics involved in the relaxation process and investigate how gravity affects the relaxation process. 

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