Relaxation mechanisms in polymers

Relaxation properties and structures of polymer nanocomposites based on modified organoclays

“…The addition of 10% compline to the nanocomposite results in a shift of the relaxation spectrum along the temperature scale and a significant drop in intensity relative to that of the sample without compline. On the basis of the classifi cation of relaxation transitions [7,9], it may be sug gested that the α process is due to the unfreezing of the segment mobility in the amorphous zones of HDPE. We relate the α' relaxation transition to the occur rence of molecular mobility in the polymer matrix regions at the interface with the nanofiller; this transi tion appears owing to the interaction of the surface of the nanofiller with the polymer matrix and to the lim ited set of polymer chain conformations in the vicinity of the solid surface.…”

“…The organoclay contents are (1) 3, (2) 5, and (3, 4) 7%; (4) the composite with 10% compline; (a) MMT-GA and (b) MMT-GMA.are characteristic of the transition from one physical state to another (from the viscoelastic state to the vis cous flow state) are observed, unlike in the case of macrocomposites during transitions from the glassy state to the rubberlike state and viscous flow state[7,9,10].The presence of several relaxation transitions in nanocomposites suggests that there are several regions characterized by the effective mobility of segments located in these regions. The differences in mass and structure of the segments are responsible for the mul tiplicity of the basic relaxation transition.…”

Structure and properties of particulate-filled polymer nanocomposites

“…It is well known [71,72] that nanofiller particles make up linear spatial structures (chains) in particulate-filled elastomer nanocomposites (rubbers). At the same time, filler particles (or their aggregates) in polymer composites filled with disperse microparticles (microcomposites) form the backbone with fractal properties determining the structure of the polymer matrix (the analog of the fractal lattice in computer simulations) [24].…”

“…It is then possible to calculate the theoretically attainable s y value for the nanocomposites under consideration in the absence of aggregation of initial filler particles: s y will equal 46.3 and 81.9 MPa according to Eqns (72) and (44), respectively. In both cases, it is much higher than in experiment (s y 14X8 MPa).…”

“…In other words, disperse nanoparticles in a polymeric matrix cannot form a spatial backbone (D B 5 2) but give rise to more or less branched chains, i.e., they produce an effect well known for elastomer (rubber)-based particulate-filled nanocomposites [72] (see also Section 2.5). Substituting this j max n value into Eqn (40) yields the limiting value of D B 1X33.…”