Polybutadiene dicumyl peroxide

Randomly - Crosslinked PB and PI. Polybutadiene (Diene 35 NFA, Firestone Tire and Rubber Co.) and cis-polyisoprene (Natsyn 2200, Goodyear Tire and Rubber Co.) were crosslinked with dicumyl-peroxide, as for PDMS. Mc values were also calculated by means of equation 2. They are given for PI in Table I and are listed for PB in reference 2. 

H 9. —, u. G. Kaiser Zur Kenntnis der Vulkanisation hochelastischer Polymerisate. 44. Mitt. Die Vulkanisation von Polybutadien durch Dicumyl-peroxid. Kautschuk u. Gummi 16, 426 (1963). 

Network structure and reaction mechanisms in high pressure vulcanisation (HPV) and peroxide vulcanisation of BR was studied by 13C solid-state NMR [43]. Different samples of polybutadiene (51% trans, 38% cis, and 11 % vinyl) were peroxide cured with dicumyl peroxide on a silica carrier and by the HPV conditions of 250 °C and 293 MPa. The 13C NMR spectra from peroxide and HPV cures were compared to a control samples heated to 250 °C for 6 minutes under atmospheric pressure. Although no new isolated strong peaks were detected in either the peroxide or HPV vulcanisations, small increases in both spectra were observed at 29.5, 36.0, 46.5, and 48.0 ppm. These peaks compare favourably with calculated shifts from structures that arise from main chain radical addition to the pendent vinyl groups. These assignments are further reinforced by the observation that the vinyl carbon concentration is substantially reduced during vulcanisation in both peroxide and HPV curing. Two peaks at 39.5 and 42.5 ppm appear only in the peroxide spectrum. Cis-trans isomerisation was absent in both cures. 

Figure 8.29 plotted against Gg for three rubbers [polybutadiene (PB), styrene-butadiene copolymer (SBR), and natural rubber (NR)] at different stages of cross-linking by (O) dicumyl peroxide and ( ) sulfur. (From Ref. 44.)... 

Polybutadiene is readily cross-linked by heating with 1% dicumyl peroxide for 10 min at 145°C. If the product is first extracted with C2CI4 to remove any non-cross-linked material and then placed in eontact with WCl6/EtA.lCl2/EtOH in C2CI4 at 45°C, it rapidly goes into solution (Hummel 1970 Kumar 1981). An added acyclic olefin assists this process but is not essential. It is clear that the network can be readily broken down by the occurrence of either intramolecular or intermolecular metathesis reactions. 

In the reaction of 2-chloro-4-methyltoluene with polybutadiene, initiated by dicumyl peroxide, there is evidence for the formation of some disubstituted units by sequence (6) (Demel 1977). 

Figure 9. Superposed spectra of cured cls-polybutadiene with varying amounts of dicumyl peroxide. All spectra were taken under NFT conditions with magic angle sample spinning (MASS). Samples were cured at 149 C for 2 hrs in a hot press. Sample (A) contained 0.5 phr ROOR, sample (B) 1.0 phr ROOR, sample (C)...

Figure 19. Proposed cross-linked structure of cis-polybutadiene vulcanized with dicumyl peroxide.

Figure 26. Superposed spectra of cured els-polybutadiene minus its components. Spectrum A, polybutadiene and the products of the degrading dicumyl peroxide. Spectrum B, cured spectrum minus uncured polybutadiene spectrum C, B minus dicumyl peroxide spectrum D, C minus dicumyl alcohol and spectrum E, D minus acetophenone. The amount of each component determined by least squares analysis.

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. 

Filled elastomers - polybutadiene containing small untreated glass beads 30 - 95 /xm in diameter, 0 - 34% by volume, cross-linked with dicumyl peroxide. We also examine the peeling detachment of polybutadiene bonded to a macroscopic flat glass surface. 

FIG. 14-1. Logarithmic plots of G against radian frequency at 25 C for four cross-linked polymers showing the onset of the transition zone. (NR) natural rubber (PB) 1,4-polybutadiene, about 50% trans (SBR) styrene-butadiene rubber with 23.5% styrene (Butyl) butyl rubber. All cross-linked with sulfur except SBR by dicumyl peroxide. (A) Plotted directly (B) with scales shifted to make C, and to, coincide with the values for natural rubber (indicated by cross). Reproduced by permission, from Science and Technology of Rubber, edited by F. R. Eirich, Academic Press, New York, 1978. 

The polydienes consist of films cured with dicumyl peroxide. These cross-linked samples were swollen with a solution of the probe in cyclohexane and dried by extensive pumping in vacuo. Films with raw polybutadiene were also prepared by casting onto a quartz plate a cyclohexane solution containing the probe. 

Polybutadiene-b/ocfc-nylon-6 copolymers prepared in this way are curable with dicumyl peroxide to hard resins of good flexural strength and impact resistance. ... 

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... 

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