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Mastication, of rubber

Figure 11.16. Efficiency of mastication of rubber at different temperatures. Molecular weights (M) measured after 30-minute mastication of 200 g natural rubber in a size B laboratory Banbury... Figure 11.16. Efficiency of mastication of rubber at different temperatures. Molecular weights (M) measured after 30-minute mastication of 200 g natural rubber in a size B laboratory Banbury...
Bound rubber in an unvulcanised carbon black-rubber mix. It results from the production of free radicals in the mastication of rubber these radicals attach themselves chemically to the particles of carbon black and form a proportion of carbon gel which is insoluble in the usual rubber solvents. [Pg.16]

Mastication of rubber which is carried out at temperatures below 90 °C is termed cold . The masticating effect is at a minimum at temperatures around 105 °C, breakdown... [Pg.18]

An odourless invisible gas (02) comprising approximately one-fifth of the atmosphere it is chemically very active. Oxygen is necessary in the mastication of rubber, but also contributes to the degradation of vulcanised rubber. [Pg.45]

In cold mastication of rubber, a substance which prevents the recombination of the free radicals produced by the mechanical shearing forces. See Cold Mastication, Free Radical and Mechano-Chemical. [Pg.52]

Mechanical synthesis by cold mastication of rubber and monomers depends on the reaction condition (monomer concentration, temperature, solvent concentration, atmosphere, presence of transfer agents, or catalyst) and on the physical and chemical properties of the rubbers, the monomers and the product interpolymers. A critical factor is the shear stress developed in the system rather than instrumentally-defined shear rates. The degree of reaction of polymer and consequently also the concentration of free macroradicals depends on stress. As a consequence, the influence of the above parameters may be connected to their influence on the viscosity of the reaction medium since an increase in viscosity causes an increase in stress at constant shear rate. [Pg.35]

Mastication of rubber. VIII. Preparation of block polymers by... [Pg.210]

A specific attention has been paid to the mechanochemical generation of X in unsaturated elastomers, EPDM, ABS, PVC and polyolefins [243, 252]. This synthetical approach exploits processing operations producing free radicals. In situ chemical reactions can be performed during some important industrial processes like mastication of rubber and extrusion, mixing or reaction injection molding of plastics. [Pg.126]

The mastication of rubber is a good example. The purpose of mastication is chain scission and the reduction of the average MW of the rubber. [Pg.16]

In order to rationalize this result for PE, a simple calculation of the energy required for scission of main-chain bonds (E c c) the frictional dissipation between chains due to mechanical action was performed. The latter was calculated from the activation energy for viscosity of the monomer repeat unit, E, determined from a low-molar-mass analogue of polyethylene. This was then used to determine the number of repeat units, n, necessary to exceed the C-C bond energy of 349 kJ/mol. From the value of 4.22 kJ/mol for E, an estimate for n of 83 was made, which was considered a good approximation to the experimental result of 100 (Sohma, 1989b). However, such a simple approach is not amenable to extension to systems of structural complexity such as chain scission during the mastication of rubber. [Pg.129]

In this century it has been shown that mastication of rubber produces free radicals with high chemical reactivity. Thus, for example, macroradicals from cis-polyisoprene initiate vinyl polymerisation when oxygen is rigorously excluded from a high shear mixer, giving rise to block copolymers, typically containing rubber and methyl methacrylate (Scheme 3.2). In the presence of oxygen this process is inhibited and the... [Pg.49]

Angier, D.J., Ceresa, R.J., Watson, W.F., 1959. Mastication of rubber 8. Preparation of block polymers by mechanical shear of polymer-monomer systems. J. Polym. Sci. 34 (127),... [Pg.101]

Pike M, Watson WE (1952) Mastication of rubber. I. Mechanism of plasticizing by cold mastication. J Polym Sci 9 229-251... [Pg.199]

It is now believed that high temperature mastication of rubber, at one time considered to be simply an oxidation process is influenced by mechanochemical reactions (Kuz minskii, 1966). The mechano-chemical generation of a relatively small number of free radicals provides the initiation step of the autoxidation process. Natural rubber masticated at KXPC oxidized more rapidly (as manifested by the development of carbonyl groups) than rubber oxidized without mechanical working at 150°C. [Pg.286]

Acceptors can have a slight plasticizing action by increasing their amount, the rate and the extent of degradation may decrease (e.g.. Fig. 3.42). In open-mill mastication of rubber, the presence of radical acceptors aids the... [Pg.144]


See other pages where Mastication, of rubber is mentioned: [Pg.865]    [Pg.77]    [Pg.46]    [Pg.8]    [Pg.16]    [Pg.22]    [Pg.210]    [Pg.122]    [Pg.46]    [Pg.865]    [Pg.128]    [Pg.130]    [Pg.156]    [Pg.100]    [Pg.110]    [Pg.307]    [Pg.865]    [Pg.813]    [Pg.817]    [Pg.34]    [Pg.209]    [Pg.265]   
See also in sourсe #XX -- [ Pg.488 ]

See also in sourсe #XX -- [ Pg.817 ]




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