CORRELATION OF BINDER MECHANICAL-PROPERTIES WITH FUNCTIONALITY TYPE AND MOLECULAR-WEIGHT DISTRIBUTION FOR HYDROXY-TERMINATED POLYBUTADIENES- C-13-NMR AND SEC STUDIES
M. Ramarao et al., CORRELATION OF BINDER MECHANICAL-PROPERTIES WITH FUNCTIONALITY TYPE AND MOLECULAR-WEIGHT DISTRIBUTION FOR HYDROXY-TERMINATED POLYBUTADIENES- C-13-NMR AND SEC STUDIES, Journal of applied polymer science, 49(3), 1993, pp. 435-444
Hydroxy-terminated polybutadiene (HTPB) liquid prepolymers (I-IX), wit
h closely similar OH values, M(n)BAR, viscosity, and microstructure, w
ere synthesized by H2O2-initiated free-radical polymerization of butad
iene in an isopropanol-water solvent system. However, binders obtained
by curing HTPB polymers showed wide variations in their sol content,
cross-link density, and mechanical properties. These variations were a
ttributed to the differences in functionality-type distribution (FTD)
and molecular weight distribution (MWD) of the polymers. FTD was inter
preted in terms of H [ HOCH2 - CH = CH - CH2 approximately approximate
ly approximately) , V (HOCH2 - CH (CH = CH2)approximately approximatel
y approximately approximately], and [GRAPHICS] primary hydroxyls. [ V/
G ] showed excellent linear correlation with the elongation at break (
E) of the binders. The polymers exhibited bimodal MWD and this behavio
r was discussed in relation to two different initiation processes occu
rring. The high molecular weight fraction (F(h)) of the various polyme
rs was determined by reverse-phase HPLC and showed good correlation wi
th E. The sol content and cross-link density of the binders also showe
d good correlation with the parameter V/GF(h). The parameters [ V/G ]
and F(h) provide acceptance criteria for blending different batches of
polymers for propellant formulations.