Thermal crosslinking of cis‐1,4‐polybutadiene at ultrahigh pressures

Abstract

cis-1,4-Polybutadiene (BR) samples, in the absence of crosslinking agents, were simultaneously compressed by ultrahigh pressures ( ú4.0 GPa) and annealed between 25 and 180ЊC. The BR samples were crosslinked when the annealing temperatures were above 100ЊC. The Vickers microhardness of the treated BR increased and the extent of swelling decreased rapidly as the annealing temperature increased, indicating that the crosslinking density increased. Solid-state carbon-13 nuclear magnetic resonance and Fourier transform infrared spectroscopy results showed that some C|C bonds in the BR were opened to form the crosslinking network structures with C{C linkages and that a partial cis-trans isomerization took place during the treatments. Differential scanning calorimetry studies revealed that the glass transition temperature increased and the crystallinity decreased as the annealing temperature increased. When the annealing temperature exceeded 140ЊC, the treated BR samples lost their rubbery elastic characteristics completely and became brittle materials.

Cross-linking process of cis-polybutadiene rubber with peroxides studied by two-dimensional infrared correlation spectroscopy: a detailed tracking

“…However, in their work, the cis-trans transition was observed only at an ultrahigh pressure (>4.0 GPa). 43 In this study, the phenomenon of trans-1,4-structure concentration increasing during the cross-linking (165-195 C) does not necessarily mean that trans-1,4-structure does not participate in the cross-linking. It is only revealed that the number of trans-1,4-structure converted from cis-1,4 is much higher than that of participating in the cross-linking reaction.…”

Thermal decomposition of cross-linked polybutadiene and its copolymers

“…The infrared spectrum of PBD cross-linked under vacuum confirms that isomerization occurs. PBD contains 98% cis-1,4-, with smaller amounts of the trans-1,4-, and 1,2 -vinyl linkages [17] . Cis-1,4-PBD shows a broad strong C-H out-of-plane bending mode at 740 cm −1 , while in trans-1,4-isomer this band is at 965 cm −1 and is much sharper, and the 1, 2-vinyl isomer shows two bands: vinyl CH at 995 and vinyl CH2 at 912 cm −1 [9], [10] .…”

Effects of cross-links, pressure and temperature on the thermal properties and glass transition behaviour of polybutadiene

“…High pressure cross-linking of PB has been previously studied by ex situ measurements for pressures up to 0.3 GPa at 513 and 523 K, which gave crosslink densities typical of an elastomer, 14 and above 4 GPa in the 373-453 K range, which gave properties ranging from elastic to brittle. 15 By simultaneous high pressure, in situ, measurements it is possible to determine the kinetics of the cross-linking process as well as to observe changes in properties, and to study the effect of both temperature and strong isothermal densification on the polymer properties before and after crosslinking. This is a relatively unexplored method to alter the state of a network polymer and obtain denser forms to augment interactions in pure and filled polymers.…”