Cross poly

Figure 1. Morphology of sequential IPNs. (a) Crois-poly (ethyl acrylate)-m/er-crojs-polystyrene, showing typical cellular structure and a fine structure within the cell walls, (b) Cross-poly (ethyl acrylate)-/ /cr-cross-polystyrene-s/a/-(methyl methacrylate), showing smaller domain structure. PEA structure stained with OsO. (Reproduced from ref. 5. Copyright 1972 American Chemical Society.)...

The variation of the domain sizes with crosslink density was recognized by Yeo et al. [28], investigating cross-poly(n-butyl acrylate)-inter-cross-polystyrene. Figure A shows the morphology of 50/50 compositions as a function of network I crosslinking level. The cellular structures are gradually transformed to finer, and more obviously cylindrical or worm-like shapes with increasing crosslink density. 

A comparison of the theoretical and experimental results for the IPN system cross-poly(n-butyl acrylate) inter-cross polystrene is given in Table II [18,21]. The agreement between theory and experiment for this system as well as other systems was better than expected, noting the approximations required to obtain a usable result. It must be pointed out that Yeo et al. had to use spherical shapes for their mathematical treatment, even though it was already recognized that most of the domains were cylindrical. 

Yeo, et al. [23,24] went on to make more complete studies of modulus-composition data using cross-poly(n-butyl acrylate)-Inter-cross-polystyrene, PnBA/PS, see Figure 6. Both the Davies and the Budlansky models fit reasonably well over wide ranges of composition, especially the Budlansky model. Other models, which in one form or another assume one continuous and one disperse phase, fit much less well. 

Table II. Experimental and theoretical domain sizes for cross-poly(n-butyl acrylate)-Inter-cross-polystyrene IPN s... 

Figure 6. Modulus-composition behavior of cross-poly(n-butyl acrylate)-/ iter-cross-polystyrene IPNs and semi-I IPNs at 25 C. (Reproduced with permission from ref. 23. Copyright 1981 Polymer Engineering and Science.)...

Figure 7. High magnification scanning electron micrograph of decrosslinked and extracted cross-poly(n-butyl acrylate)-inter-cross-polystyrene IPN (80/20). The poly(n-butyl acrylate) phase was extracted. (Reproduced from Ref. 2 . Copyright 1982 American Chemical Society.)...

Figure 12. Radius of poly(dimethyl slloxane) phase as a function of weight fraction In cross-poly(dimethyl slloxane)-Inter-cross-polystyrene sequential IPN s with three different crosslink densities of network I. Broken lines are theoretical values from...

Figure 17. Logarithmic dependence of the scattered light intensity, I, on time, t, for polystyrene-inter-cross-poly(butyl methacrylate) Semi-II IPN s. Registration anglel 8F) 10 ...

Damping Behavior of Silent Paint . The damping behavior of a typical "Silent Paint" composition, cross-polv(ethyl methacrylate)-inter-cross-poly(n-butyl acrylate) 25/75, constrained with epoxy resin, was then compared with several commercial materials as a function of temperature. Figure 3. The "Silent Paint" composition, curve A, damped effectively over a broad temperature range whereas the commercial materials, curves B and C [poly (vinyl acetate) ], and D, E, and F, of various compositions, damped effectively over narrower temperature ranges. 

Since this paper will be restricted to sequential IPN s based on cross-poly butadiene-inter-cross-polystyrene. PB/PS, it is valuable to examine the range of possible compositions, see Figure 2 ( ). The PB/PS IPN polymer pair models high-impact polystyrene, and in fact, many of the combinations made are actually more impact resistant than the commercial materials. In general, with the addition of crosslinks, especially in network I, the phase domains become smaller. The impact resistance of high-impact polystyrene, upper left, is about 80 J/ra. In the same experiment, the semi-I IPN, middle left is about 160 J/m, and the full IPN, lower left, is about 265 J/m (g). Since the commercial material had perhaps dozens of man-years of development, and the IPN composition was made simply for doctoral research with substantially no optimization, it was obvious that these materials warranted further study. 

Interpenetrating -inter- Cross-poly A-inter-cross-poly B... 

An axial (or crossed poly tope) experimental matrix composed of points symmetrically spread on each axis, at a distance a of the center of the domain, and that we represent by a, 0,. 0], which will give us information on the coefficients (6,) of the first degree terms and the coefficients (i,() of the squared terms-... 

Many important advances have been made in the nomenclature of polymer blends, grafts, blocks and IPN s. These include a nomenclature document recently published by the lUPAC Nomenclature Committee and one now under consideration. Briefly, two advances were made that relate to IPN s. The first was the use of the prefix cross- to indicate a crosslinked polymer. Thus, cross-poly-butadiene is distinguished from the linear product, written polybutadiene. The second advance was the introduction of the symbol -inter-, which means interpenetrating. Thus, cross-poly-(ethyl acrylate)-mtcr-cross-polystyrene (1) represents the IPN based on poly(ethyl acrylate) and polystyrene. The symbol -inter- has exactly the equivalent meaning as -block- and -graft- possess for block and graft copolymers, respectively. 

Most recently, An et found evidence for spinodal decomposition in cross-poly-... 

McGarey and Richards also found some evidence for a shoulder in their SANS studies from cross-poly(dimethylsiloxane)-inrer-cross-polystyrene sequential IPN s corresponding to a wavelength of 2500 A. This may have been the result of the very low vinyl content in their poly(dimethyl-siloxane). By other methods of analysis, they estimated chord lengths of the order of 200-500 A. Examination of the older literature, both by Sperling s group as well as others, suggests that spinodal decomposition plays an important part in domain formation of many IPN systems. 

Figure 10 cross-poly(ethyl acrylate), PEA, and cross-poly(methyl methacrylate) PMMA, IPN s before and after decrosslinking the acrylic acid anhydride, AAA, moiety, plotted in the traditional semi-log way (a,c) and the linear loss modulus portion plotted vs. temperature (b, d). Although the shapes of the curves are changed by decrosslinking and annealing (c, d), the areas under the linear loss modulus-temperature curve remain constant ... 

---