Specific features of plasticization in statistical copolymers

The Phase State of Calcium Stearate in Bnks Butadiene–Acrylonitrile Rubbers

“…This means that there is a considerable reduction in the free volume of the unordered part of rubbers during annealing, irrespective of the content of AAN units. In a certain way this correlates with results obtained earlier on the change in the structural organisation of rubbers [2][3][4][5][6] and vulcanisates based on them [7][8][9][10][11], which was recorded by a number of methods in the region of 90 and 130°C. Differences in the change in the mesomorphic structure of CSt with temperature in the free state and in rubbers confirm the presence in the latter of ordered formations and their ability to be rearranged with increase in temperature.…”

“…As CSt is present in BNKS rubbers in a mesomorphic state, it can be assumed that CSt mesomorphic phase lies in the unordered part of the rubbers. This assumption is based on the fact that the large CSt molecules cannot penetrate into ordered formations present in amorphous copolymers [2][3][4].…”

The Effect of An Anionic Emulsifier on the Ozone Resistance of Vulcanisates of Butadiene–Acrylonitrile Rubbers

“…With an identical composition of the formulation, vulcanisates of SKN-26, both with and without surfactant, are most crosslinked [9]. This feature of formation of a network of chemical crosslinks by SKN rubbers is consistent with data obtained by the diffusion method [4,5]. According to the latter, the diffusion coefficients and the equilibrium solubility of certain penetrants in SKN-26 are greatest among the SKN rubbers.…”

“…According to data of NMR spectroscopy [1], macromolecules of butadiene-acrylonitrile rubbers comprise microblocks of trans-1,4-butadiene units and sequences of alternating trans-1,4-butadiene units and acrylonitrile units. Macromolecular fragments of the same type, by virtue of the differences in their geometric and chemical structure, are selectively segregated, forming ordered formations of two types, respectively, according to data of X-ray diffraction analysis (XDA) [2,3] and the diffusion method [4,5]. The introduction of anionic surfactant causes changes in the ordered structure of the butadiene-acrylonitrile copolymer (SKN), which depend on their comonomer composition and the prehistory of specimens, according to XDA data.…”

“…This assumption is confirmed, in particular, by the stronger reduction in the flow temperature of SKN-26 with introduction of surfactant, among the SKN rubbers ( Table 1). The volume content of stronger ordered formations of sequences of alternating units, which increases in the process of vulcanisation [5,12], and which do not break down, at least at strains of <60% (Figure 2a, curves 3 and 4), ensures a higher degree of orientation of chain fragments under elongation for vulcanisates of SKN-40, and especially SKN-26, than in the case of vulcanisates of SKN-18.…”