real rubbers, exists in the rubber state, and the mechanism is sensitive to the molar
mass. Such an interaction mechanism is often defined as theentanglement of polymer
chains, which constitutes a 3D dynamic network to trap the polymer chain. In
common amorphous polymer fluids, the microscopic mechanism of entanglement
is mainly a geometric topological constraint, as illustrated in Fig.6.4, rather than the
physical entanglement originated from inter-chain attractions, unless strain-induced
crystallization influences the mechanical response of global elasticity upon a large-
scale deformation.
Fetters et al.examinedMefor a series of non-crystalline polymers (Fetters et al.
1999 ) and found that
Me¼rRT
E 0¼n^2 tNarp^3 (6.1)Fig. 6.3 Illustration of polymer transition temperaturesTm,TgandTfas a function of the molar
massM
Fig. 6.2 Illustration of deformation features of polymers in relation with the molar mass, the
crystallinity and the degree of crosslinking
6.1 Characteristics of Polymer Deformation 95