Poly surface free energy data

Figure 11.63. The effect of treatment time on surface free energy of PVC plasticized with 10 phr of epoxidized soybean oil and 40 phr of di-(2-e1hylhexyl) phthalate and 40 phr of poly(ethylene-co-vinyl ace-tate-eo-carbon monoxide). [Data from Audic J-L Poncin-Epaillard F Reyx D Brosse J-C, J. Appl. Polym. Sci., 79, No.8, 22nd Feb.2001, p.1384-93.]...

Figure 7.30 illustrates the limits from equilibrium to cold crystallization. They are based on a computer calculation for three-dimensional cold crystallization. It is assumed in this case that sequences of less than three A-units do not crystallize, and that at least two out of the four neighboring chains must match the sequence of three repeating units to make the central sequence crystalline. If all four lateral neighbors are crystalline, the repeating unit is in the interior of the crystal, if only three are crystalline, it is on the surface, and if only two are crystalline, it is part of an edge. With this critical sequence length and two surface free energies, experimental data of poly(ethylene terephthalate-co-sebacate) can be discussed, as is shown in Fig. 7.31. The experimental phase diagram of the same copolymer, but after slower cooling, is displayed in Fig. 7.26.

This concept is illustrated in Fig. 8.11 for a poly(ethylene terephthalate) substrate and a mild steel (ferric oxide) substrate with, in both cases, water as the hostile environment. Values of y and yl of the various adhesives may be measured, as described in Chapter 2, or extracted from the literature (see Table 2.3) for example, considering a styrene-butadiene rubbery adhesive the values are 27.8 and 1.3 mJ/m, respectively, and for a typical epoxy adhesive they are 41.2 and 5.0 mJ/m, respectively. Hence, it is evident that these (and most other) adhesives will form an environmentally water-stable interface with the poly(ethylene terephthalate) substrate but an unstable interface with mild steel. Indeed, the data confirm that if only secondary molecular forces are acting across the interface then water will virtually always desorb organic adhesives, which typically have low surface free energies of less than about 60 mJ/m, from a metal oxide surface. Hence, for such interfaces, stronger intrinsic adhesion forces must be forged which are more resistant to rupture by water. 

AG is the free energy of activation for flow, h is Planck s constant, and A is the area per flow unit. This theory was applied to the surface viscosity of a number of proteins, measured as a function of surface pressure (MacRitchie, 1970). Plots of log tjs against II were found to be linear, enabling AG and A to be evaluated. The data, which are summarized in Table VI, show that the flow unit for all the proteins and poly-DL-alanine is a segment of approximately 6-8 amino acid residues and also that the free energy of activation for flow is similar for all... 

The majority of experimental data has been measured for two blend systems PS/PVME, and isotopic blends of PS and poly(perdeutero-styrene). The surface compositions for PS/PVME blends were found to scale directly with the surface energy difference between the constituents (23), showing that the latter factor dominates the surface behavior, a result that might be expected for these nearly athermal blends with large surface energy differences. (The PS/PVME system has an interaction parameter estimated to be —0.0011 and can be considered as effectively athermal.) The square gradient theory with the Flory-Huggins free... 

---