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Characterization of cis ‐1,4‐polyisoprene polymerized with lanthanide catalyst system (Ln‐PIR)
Author(s) -
Baogong Chien, PaoKung Qian,
Fuseng Yu,
Rongshi Cheng,
Wanjun Ruan Meina Zhang,
Shentian Li,
Yanshou Zhang,
Yuhua Yang
Publication year - 1985
Publication title -
journal of applied polymer science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.575
H-Index - 166
eISSN - 1097-4628
pISSN - 0021-8995
DOI - 10.1002/app.1985.070300133
Subject(s) - yield (engineering) , relaxation (psychology) , quantum entanglement , stress relaxation , polymer , intrinsic viscosity , thermodynamics , viscosity , modulus , materials science , activation energy , chemistry , polymer chemistry , physics , composite material , psychology , social psychology , creep , quantum mechanics , quantum
The PIR raw rubber samples, Ln–PIR and Ti–PIR, were subjected to molecular characterization, which shows that Ln–PIR contains microgel particles, but the least branching in its macromolecular chains; its cis ‐1,4 content is about 96% and molecular weight distribution is rather broad. The value of α in the Mark‐Houwink viscosity equation for molecular weight M η is determined as 0.70. The abnormal stress–relaxation behavior can be normalized by the introduction of an entanglement reduction factor, e.g., M η / M c for maximum relaxation time. This reduction is subsequently verified by evaluating the molecular weight dependence on bulk viscosity with 3.45th power. The starting of a yield process is equivalent to that of a disentanglement process, since both processes have approximately the same activation energy, 8 kJ/mol. For the onset of yield or of entanglement, the critical molecular weight M c as estimated independently by yield strength method or by relaxation spectrum is equal to (5.4 ± 0.2) × 10 4 . It is confirmed by the reduced yield strength method by calculating M e from the equation M e = 3 g N ρ RT / E eN with g N = 1.22 and then by extrapolation, where E eN is the equilibrium modulus due to entanglement.