PMMA/PEA

However, as seen in Figure 8.9, despite the facts that PEA and PMMA are chemically isomeric and the resultant IPN is optically clear, full thermodynamic compatibility and mutual solubility have not been achieved. The blurring of the remaining phase boundaries suggests that phases of distinct compositions in the classical sense probably do not exist in PEA/ PMMA IPN s. Perhaps all compositions, as illustrated in Figure 8.10, exist side by side (Sperling et al, I910a,b). 

The most incompatible compositions are the 50/50 series examined above. IPN s containing 25/75 PEA/PMMA, the most compatible of the... 

Figure 8.13. Modulus-temperature behavior of PEA/PMMA IPN s. Numerical values indicate wt % PEA. All compositions were found to exhibit only one broad transition region. (Sperling et al, 1970a.)...

The apparent breadth of the glass transition can be examined further with the aid of time-dependent creep experiments. A master curve, composed from data for several creep experiments at different temperatures performed with a 50/50 PEA/PMMA IPN, is shown in Figure 8.14. 

Figure 8.14. Master relaxation curve for a 50/50 PEA/PMMA IPN composition at 30 C. The transition covers 23 or 24 decades of time. Curve 1 represents equation (8.3) as discussed in the text. Curve 2 represents equation (8.2). The original points were taken as shear creep data, and converted to relaxation data for plotting purposes. (Sperling et al, 19706.)...

Figures 8.16 and 8.17 show F and F as a function of temperature for PEA/S and PEA/PMMA IPN s (Huelck et a/., 1972). Figure 8.16 shows results typical of an incompatible system, with two distinct transitions and loss peaks. When PMMA is substituted for PS, a single, very broad transition appears. Since PS and PMMA are very nearly an iso-T pair and hence the copolymer 7 s are essentially invariant with respect to composition, the shifting and broadening of the higher transition may be attributed to mixing with the PEA component. Likewise, changes in the lower temperature...

Surprisingly, the peaks in the more compatible PEA/PMMA IPN s (Figure 8.17) are not shifted inward further rather, the value of " in between... 

In contrast to the PB/PS compositions, the PEA/PS and PEA/PMMA IPN S exhibit only marginal increases in impact resistance values in comparison to the homopolymer PS and PMMA values of impact strength are typically below 1.0 ft-lb/in. of notch. This relatively poor performance may have two explanations (1) the domain sizes may be too small, and (2) the Tg of the PEA (-22°C) may be too high. According to the theory developed in Section 3.2, a 7 of about — 40 C of the rubber phase is required for impact resistance, suggesting that explanation 2 may be correct. 

PEA/PMMA IPNs, see Figure 6.2a, where, as a first approximation, the interfacial tension, y, may be assumed to be zero. Domains of the order of 60-100 A are predicted. This modifies earlier conclusions of semicompatibility for this system, suggesting that fine structure is always to be expected in sequential IPNs. Physically, this might result from the concentration of monomer II in small regions of space (within polymer I) that statistically have lower than average crosslinking levels. 

Figure 6.26. Storage (E) and loss (E ) moduli (a) 48.8/51.2 PEA/PS (b) A1AI52I9 PEA/PMMA IPNs, both at 110...

V. Huelck, D. A. Thomas and L. H. Sperling, Interpenetrating Polymer Networks of Poly(ethyl acrylate) and Poly(styrene-co-methyl methacrylate). II. Physical and Mechanical Behavior, Macromolecules 5(4), 348 (1972). PEA/PS, PEA/PMMA sequential IPNs. Mechanical behavior, Tg. 

L. H. Sperling, V. Huelck, and D. A. Thomas, Morphology and Mechanical Behavior of Interpenetrating Polymer Networks, in Polymer Networks Structure Mechanics and Properties, A. J. Chompff and S. Newman, eds.. Plenum, New York (1971). PEA/PS and PEA/PMMA sequential IPNs. Glass transitions. 

In a second paper, we reported the transition behavior of the isomeric IPN pair PEA-PMMA. For all compositions only one extraordinarily broad transition was found as shown in Figure 2. The unusual breadth of the transition was confirmed via dilatometry. The question of compatibility was raised at that time. Other workers had predicted that while incompatible blends yield two sharp transitions truly compatible blends should yield one sharp transition. (17),... 

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