Threshold fracture energy

Such a /Mc dependence has been observed for the threshold fracture energies in rubberlike materials [106,107] in accordance with the model of Lake and Thomas [108]. However, Eq. (7.10) is based on arrest energies and the reason for the use of arrest energies is not clear. 

Threshold fracture energy 125,127 Time-temperature superposition 128 -----transition diagram 72... 

Figure 7 Increase in threshold fracture energy, Go, with length, A pi, and surface density, S of isoprene chains (after Ref. 58). Degree of polymerization (I) 558, (II) 882, (III) 2205.

Mazich et al. utilized the pure shear fracture test to generate master curves of threshold fracture energy for polydimethylsiloxane polymers as a function of crosslink density [40]. Their data compared well with recent data from Gent and Tobias [39]. 

In all cases the threshold fracture energy is still about 10-20 times larger than the theoretical work of adhesion predicted from thermodynamic estimates. This discrepancy has been explained by the theory of Lake and Thomas [41]. The work to break a polymer chain includes the work needed to pull the chain taunt in addition to the work needed to break a the chemical bond between two individual atoms in the chain. Thus, the fracture energy scales with the square root of the molecular weight between crosslinks as defined below ... 

A classic theory by Lake and Thomas [20] has guided many of the analysis of correlating the threshold fracture energy of an elastomer with the length of the... 

---