Melting deformation

The melting capacity of this geometrical configuration can easily be calculated from Eqs. 5.8-11 and 5.8-1. 

The results are very revealing and instructive. The rate of melting increases with the total force Fn, but only to the one fourth power. The physical explanation for this is that with increasing force, the film thickness is reduced, thus increasing the rate of melting. However, the thinner the film, the larger the pressure drops that are needed to squeeze out the melt. The dependence on the plate temperature is almost linear. The inverse proportionality with R is perhaps the most important result from a design point of view. If viscous dissipation were included, some of these results would have to be modified. 

Stammers and Beek (37) have performed a number of experiments to verify the theoretical model just described, using polyethylene and polyoxymethylene. The linear relationship between vsy/(FN)1 4 and [(7), — Tmf Aj /r1/4], as predicted by Eq. 5.8-11, was clearly established, and the slope calculated from this equation agreed well with the experimental data. 

On the other hand, we discussed and presented in physical terms the very powerful melting mechanisms resulting from repeated, large deformations, forced on compacted particulate assemblies by twin co- or counterrotating devices. These mechanisms, which we refer to in Section 5.1, are frictional energy dissipation (FED), plastic energy dissipation (PED), and dissipative mix-melting (DMM). 

At the time of the writing of the first edition of this text (38), we wrote the following about mechanical energy dissipation in repeatedly deforming active compacted particulates and the evolution of their melting  

---

Fig. 16. Gibbs energy-temperature diagram if FCC and ECC are present in the system. Ai-isotropic (undeformed) melt, A2-deformed melt (nematic phase) points 1 and 4 - melting temperatures of FCC and ECC under unconstrained conditions (transition into isotropic melt) points V and 2 -melting temperatures of FCC and ECC under isometric conditions (transition into nematic phase), point 3 - melting temperature of nematic phase (transition into isotropic melt but not completely randomized)...

Heat, momentum, mass, entropy balances at finite domain structure levels of solids and liquids, during deformation, melting, and solidification ... 

De Gennes (1971) postulated that polymer molecules were constrained to move along a tube formed by neighbouring molecules. In a deformed melt, the ends of the molecules could escape from the tube by a reciprocating motion (reptation), whereas the centre of the molecule was trapped in the tube. When the chain end advanced, it chose from a number of different paths in the melt. This theory predicts that the zero-shear rate viscosity depends on the cube of the molecular weight. However, in the absence of techniques to image the motion of single polymer molecules in a melt, it is hard to confirm the theory. 

Y.M. Boiko, W. Brostow, A.Y. Goldman, A.C. Ramamurthy, Tensile, stress relaxation and dynamic mechanical behaviour of polyethylene crystallized from highly deformed melts. Polymer, 36 (7), 1383-1392,1995. 

Sn3(q) for example — is a different function of q for the isotropic melt, the deformed melt in the perpendicular direction (faster decreasing) and in the parallel direction (even faster). This means that the correlations would be modified at the local scale In the isotropic case it is possible to extract the Rq s from a fit to (14.1) where So(q) will be the form factor of a wormlike chain. Because correlations appear modified... 

Twardowski TE, Gaylord RJ (1989) The localization model of rubber elasticity and the stress-strain behavior of a network formed by cross-linking a deformed melt. Polym Bull 21(4) 393-400... 

---