Analysis of Modulus Data

Data lying to the right of the theoretical line provide an indication of physical crosslinks, since the experimental modulus is larger than the theoretical modulus. A vertical stacking of points containing the same network I crosslink density (but different network IPs), suggests the dominance of network I over network II, since the experimental modulus is relatively constant. 

The effects of network I domination and added physical crosslinks are summarized in Table 4.3. Unfortunately, Millar presented no modulus data as his materials were suspension-sized particles. 

Before any discussion of the results, two comments must be made. First, a much greater scatter of the data was encountered for the modulus data, compared to the swelling data. Second, in some cases, the values of the modulus were below those predicted, for single networks and IPNs alike. Because the data were collected over a range of temperatures (all above 100 C), it was more convenient to work in terms of the crosslink levels rather than in terms of the moduli. From equation (4.8), a value of 

If the experimental values of v from E = 3pRT exceeded (theory), this was taken as evidence for new physical crosslinks caused by IPN formation. Likewise, a slower than expected variation within a composition series or near series (via statistical analysis) was taken as evidence for an outsized contribution by network I. 

While Table 4.3 affirms network I domination, there appears to be conflicting evidence for added physical crosslinks. 

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