Poly 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. 

Estimate the expansion coefficient of the poly(ethylene terephthalate) melt and its density at the extrusion temperature of 277 °C (=550 K). 

A fraction of poly (methyl acrylate) presents maximum damping at 0.50 Hz at 25°C. Make a rough estimation of the diluent that must be added to shift the maximum damping to 100 Hz at the same temperature. The glass transition temperatures of the diluent and the polymer are —70°C and 10°C, respectively, and their expansion coefficients are 8.5xlO K and 4,2 X respectively. 

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...

The curve for very slow coolings cannot be obtained by direct measurement. To obtain such a curve, one can, for example, define a time G/e for which the distance from the equilibrium curve is 1 je times the initial deviation. For the poly (styrene) data shown in Figure 10-1 To = 89° C), this time is 1 s at 95° C and 5 min at 89° C, but already 1 year at 77° C. The dotted curve in Figure 10-1 was consequently obtained by extrapolation of the values for a poly(styrene) solution in malonic ester. This extrapolation is possible since the cubic expansion coefficient of the polymer in the solvent is a linear function of the concentration up to a poly(styrene) concentration of 90%. 

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). 

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