Urethane-crosslinked polybutadiene

Three urethane-crosslinked polybutadiene elastomers (TB-1, TB-2, and TB-3) of varying crosslinking levels, along with a similarly crosslinked styrene-butadiene copolymer (HTSBR) and two polybutadiene polymers randomly crosslinked with dicumyl peroxide (PB-1 and PB-2), have been investigated to determine their viscoelastic behavior. Elsewhere, TB-1, TB-2, and TB-3 have been designated as HTPB-1, HTPB-2, and HTPB-3, respectively. 

Torsional creep measurements were made on the urethane-crosslinked polybutadiene elastomers at temperatures between —68 C and 25 C. The average molecular weight of a networks chain. Me, is 3400, 5200, and 8300 for TB-1, TB-2, and TB-3, respectively. The reduced shear creep compliance Jpit/ax) curves obtained for the three samples are shown in Figure 5.13. The reference temperatures are chosen to be 7.4°C, 0.0 C, and 17.0°C for TB-1, TB-2, and TB-3, respectively, so that superposition is achieved at shorter times... 

Torsional creep measurements were made on the urethane-crosslinked polybutadiene elastomers at temperatures between -68 and 25°C.The average molecular weight of a networks chain. Me, is 3400, 5200, and 8300 for TB-1, TB-2, and TB-3 respectively. The reduced shear creep compliance Jp(t/ar) curves obtained for the three samples are shown in Fig. 18. The reference temperatures are chosen to be 7.4,0.0, and 17.0°C for TB-1, TB-2, and TB-3 respectively so that superposition is achieved at shorter times in the primary softening dispersion. The most loosely urethane-crosslinked TB-3 has the largest 7e = 2.5 x lO Pa There is a plateau intermediate between the glassy compliance 7g (not reached in these measurements) and /e, and its level is about 2.0 X 10 Pa in all three samples. The network chain density does not affect the form of the time-dependent response up to and including the intermediate plateau in the Jp(t) curves. Only the terminal dispersion, i.e., the approach to /e, is influenced. The shift factors, Uj, that were used to obtain the... 

The logarithm of the reduced shear creep compliance Jp t/aj) of several elastomers are compared at 0°C in Rg. 20 as a function of the logarithm reduced time-scale log(i/flr)- The elastomers include (1) the urethane-crosslinked polybutadiene elastomer, TB-2, described in Subsection B (2)... 

Two types of networks were prepared (i) randomly crosslinked polybutadiene, and (ii) model urethane networks, (a) polybutadiene based, and (b) poly(e-caprolactone) based. The randomly crosslinked networks were prepared from polybutadiene (Duragen 1203 obtained from General Tire and Rubber Co.) crosslinked with di-cumyl peroxide. Specifications of the as obtained polybutadiene are given in Table I. Polybutadiene was purified by dissolving in benzene and precipitating in methanol. Precipitated polybutadiene was redissolved in benzene. Seven different weights of dicumyl... 

Figure 4.1.5. Volume of the increased swelling of crosslinked polybutadiene urethane elastomer, Xh b-85. Labels of points ...

Figure 5.1.2. Dependence of equilibrium swelling of crosslinked elastomer of polyester urethane (1) and polybutadiene nitrile mbber (2) on the volume fraction of acetone in the toluene-acetone mixture. [Adapted, by permission, from V.V. Tereshatov, V.Yu. Senichev,...

The obtained theoretical predictions have been verified in experiments on real elastomers. The elastomers tested in our experiments were amorphous polybutadiene urethanes (PBU) wifli polymer network of different density 0.3 kmol/m (PBU-1), 0.05 kmol/m (PBU-2), 0.2 kmol/m (PBU-3), 0.1 kmol/m (PBU-4). Oligooxypropylene triol - Laprol 373 was used as a crosslinking agent at the curing of prepolymer of oligobutadiene diol. The elastomer specimens were manufactured in the form of disks, 35 mm in diameter and 2 mm thick. The kinetics of specimen swelling was determined in low-molecular liquids toluene, dibutyl sebacate (DBS), dioctyl sebacate (DOS). 

---