September 1994
Additivesfor Polymers
Microdispersion of carbon black in rubbers
Determining the effectiveness of rubber stabilizers
The microdispersion of carbon black in rubber vulcanizates can readily by analysed by atomic force microscopy (AFM). A clean freshly prepared surface by cutting the sample is the only requirement for the preparation. In conjunction with statistical image analysis the microdispersion can be characterized in a quantative way by the distribution of interaggregate distances or aggregate sizes. It should also be possible to detect finer differences of the carbon black morphology by exposing larger parts of aggregates and agglomerates by plasma etching of the surface. This should allow the characterization of the real size and shape of the aggregates/ agglomerates and also the extent of networking. Erosion techniques which have recently been applied to characterize the branched structure of carbon black aggregates in the dry state may be useful for this purpose. (14 refs).
The electron structure of aromatic amines (the most effective rubber stabilizers) and the molecular index of their reactivity (MIR), ie their capability of entering into nucleophilic (Sd, electrophilic (S3 and radical (SJ reactions, mean that an assessment can be made of the activity of amines in the ageing of elastomers and, in particular, in the chainradical processes of oxidation. When investigating diamines in polymer compositions, a correlation is observed between S, and activity in thermal ageing.
Kautschuk Gummi (June), 409-415
Kunststofle,
1994,
Dispactol polyfunctional processing aids This article presents the results of a study of the effectiveness and prospects for use of the new Russian additives, Dispactol and Dispactol M, in the production of tyres. The basis of Dispactol is a composition of zinc stearate and synthetic fatty acid, and Dispactol M also includes oxyethylated fatty acid. The composition of these additives suggested the polyfunctional nature of their action on rubber blends. According to the data in the literature, fatty acids and their zinc salts are effective carbon black dispersing agents, curing activators and plasticizers and oxyethylated fatty acid also has the properties of a secondary curing accelerator. (15 refs). Int. Polymer Science & Technology, 1994, 21, (4), T/20-23. (Translated from: Kauchuk i Rezina, 1993, (5), 48). O1994 Elsevier Science Ltd
In various forms of ageing, it has been established that the effect of radicals in nitrogen on the MIR in monoamines (isopropylaniline, cyclohexylaniline, diphenylamine) and in p-phenylenediamines (N,N’-isopropylphenyl-p-phenylene-diamine, N,N’-cyclohexylphenyl-p-phenylene-diamine, N,N’-diphenyl-p-phenylene-diamine) differs from the calculated data. This difference is largely brought about not only by the capacity of these compounds to inhibit the breakdown or structuring of polymer chains, but also by a whole series of other factors - their compatibility with the elastomer matrix, the capacity to migrate in it, the effect of temperature, the degree of interaction with other components in polymer compostions, their effect on the technological and physicomechanical indicators of elastomer compositions, volatility and thermal and chemical stability. The above factors largely determine the activity of aromatic amines as antifatigue agents, ozone stability agents, light stability agents and antiradicals, which must be taken into account when selecting new compounds for the synthesis of effective diamines, stabilizers for elastomer compositions, and, therefore, the calculated data for S,, S, and S, are inadequate. Int. Polymer Science & Technology, 1994, 21, (4), T/25. (Translated from: Kauchuk i Rezina, 1993, (5), 53).
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