1,2-Poly butadienes cross-linking

It has been patented as a cross-linking agent for polypropylene and poly butadiene (Ref 4)... 

Maleimides Alkyl and aryl maleimides in small concentrations, e.g., 5-10 wt% significantly enhance yield of cross-link for y-irradiated (in vacuo) NR, cw-l,4-polyisoprene, poly(styrene-co-butadiene) rubber, and polychloroprene rubber. A-phenyhnaleimide and m-phenylene dimaleimide have been found to be most effective. The solubihty of the maleimides in the polymer matrix, reactivity of the double bond and the influence of substituent groups also affect the cross-fink promoting ability of these promoters [82]. The mechanism for the cross-link promotion of maleimides is considered to be the copolymerization of the rubber via its unsaturations with the maleimide molecules initiated by radicals and, in particular, by allyfic radicals produced during the radiolysis of the elastomer. Maleimides have also been found to increase the rate of cross-linking in saturated polymers like PE and poly vinylacetate [33]. 

It is evident that reactions of unsaturated polymers with bisnitrile oxides lead to cross-linking. Such a procedure has been patented for curing poly(butadiene), butadiene-styrene copolymer, as well as some unsaturated polyethers and polyesters (512-514). Bisnitrile oxides are usually generated in the presence of unsaturated polymers by dehydrochlorination of hydroximoyl chlorides. Cross-linking of ethylene-propylene-diene co-polymers with stable bisnitrile oxides has been studied (515, 516). The rate of the process has been shown to reduce in record with the sequence 2-chloroterephthalonitrile oxide > terephthalonitrile oxide > 2,5-dimethylterephthalonitrile oxide > 2,3,5,6-tetramethylterephthalo-nitrile oxide > anthracene-9,10-dicarbonitrile oxide (515). 

The yield of cross-links depends on the microstructure and purity of the polymer as well as whether it was irradiated in air or in vacuo2 The rate of degradation was found to be essentially zero when polybutadiene or poly(butadiene-styrene) was irradiated in vacuo, but increased somewhat when irradiated in air. 

Kramer, O., Carpenter, R. L., Ty, V., Ferry, J. D. Entanglement networks crosslinked in states of strain, paper presented at Society of Rheology Meeting, Montreal, October 1973. Part of this work is described in Entanglement networks of 1,2-poly butadiene crosslinked in states of strain. I. Cross-linking at 0° C. Macromolecules 7,79-84 (1974), by the same authors. 

Figure 9 shows an example for application in the lower density range. The gradient system consists of mixtures of HpO and DpO with methanol. The sample under investigation is a mixture of a normal and an additionally cross-linked poly(butadiene) latex. The particle density is not uniform. The normal poly-(butadiene) has particle densities as expected around 0.89 g cm 3, but for the additionally cross-linked poly(butadiene) density values between 0.9 and 0.92 g cm-3 are obtained. Additional cross-linking yields obviously higher particle densities. In this case the experiment needs 30 min. 

Figure 7.23 Applications of the NMR-MOUSE to elastomer materials (a) T2 values for a curing series of carbon-black filled NR. Comparison of values obtained at high homogeneous field (DMX 300) and with the NMR-MOUSE, (b) cross-link series of unfilled SBR with different sulfur content, (c) T2 versus glass-transition temperature Tg of unfilled SBR by the CPMG and the steady-state CPMG methods, (d) normalized Hahn-echo decay curves for poly(butadiene) latex samples. Different decay rates are obtained for small medium and large cross-link densities...

Modification of macromolecular material properties by hydrogen bond formation has been demonstrated at the example of thermoreversible networks Stadler modified poly(butadiene) elastomers with urazole groups to introduce hydrogen-bonded cross-links into the system. In fact, thermoreversible cross-linking appeared due to the urazol-urazole molecular recognition, causing intermolecular cross-links [408,467]. The group of Meijer expanded the approach by the synthesis of two... 

Sulfur cross-linked chains resulting from vulcanization of poly-1,3-butadiene. 

Chloromethylated cross-linked polystyrene was used to initiate the graft copolymerization of several 2-substituted-2-oxazoline derivatives (130, 131). Allylic chloride from 1-chloro-l,3-butadiene-butadiene copolymer and from poly(vinyl chloride) was used to initiate the graft copolymerization of 2-methyl-2-oxazoline (132. 133). 

Fig. 8a-c. Micrographs of cross-linked poly(butadiene)-fo-poly(ethylene oxide) gels, templated in a cubic b hexagonal c lamellar phases. A dense packing of cylinders can be observed by TEM after cross-linking in the hexagonal phase. (Reproduced with permission from [74])... 

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