Structure and topology of space network in vulcanizales and the dynamic properties
The effect of structural and topological factors (concentration of elastically active network chains, concentration of chemical network nodes, concentration of permanent and temporal nodes of chain entanglements determined by the Langley method) on the dynamic properties of the non-filled vulcanizalcs in the range of deformation frequency of 10-50 Hz was discussed. The chemical structure of crosslink junctions and the free chain ends arc not deciding about the values of the storage and dissipative moduli. Not only the permanent chemical and topological nodes but also the temporal nodes of chain entanglements reveal an clastic activity during dynamic deformations. Dissipation of energy during dynamic deformation is due to a forced mechanical interaction (and a corresponding friction) of elastomer chains concentrated in the temporal nodes of entanglements. Their transformation into permanent topological nodes results in a decrease of the dissipative modulus with the progress of the crosslinking process. The storage and dissipative moduli depend on the geometrical parameters of the sample, whereas the loss angle is a structural and topological quantity. The storage modulus can be calculated taking into account the geometrical parameters and knowing the concentrations of the chemical nodes and the nodes of chain entanglements. The reason of differences in dynamic properties of various rubber vulcanizalcs arc among other the differences in the degree of chain entanglements. A highly swollen vulcanizalc does not dissipate energy during dynamic deformations and its storage modulus is equal to its modulus of elasticity. The observed relationships make it possible to rationally select type of rubber and its plasticity, type and amount of curative and geometrical shape of the sample during designing and manufacturing of rubber articles intended for work under dynamic conditions.
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