SynopsisThe temperature dependence of the dynamic viscoelastic behavior of interpenetrating networks (IPN) of polyurethane (PU) prepared from poly(oxypropylenedio1) (POP) and toluylene diisocyanate (TDI), and of polyurethane diacrylate (PUA) prepared from POP and TDI by reacting isocyanate groups of the prepolymer with 2-hydroxyethyl acrylate, was measured in the main transition region. The photoelastic behavior of IPN swollen in dimethylformamide (DMF) and methyl ethyl ketone (MEK) was examined in the rubbery region. The temperature dependences of the dynamic Young modulus E* of IPN in the concentration range of PUA 3 50 vol.% indicate a pronounced two-phase behavior. The effect of the composition of IPN on the temperature dependence of the modulus E* was quantitatively described by Takayanagi's two-phase model with the conclusion that the PU network is the continuous phase of IPN at I 90% PUA. While in the range of high concentrations of PUA ( 3 5%) the contributions of phases to E* are additive within the whole range of temperatures, the thermomechanical behavior at low PUA concentrations (640%) is more complex. T h i s finding is interpreted by the existence of an interfacial layer which leads to the loss of the distinct two-phase character of IPN. The higher number of elastically active network chains (EANC) of the PUA network compared with the PU network corresponds to different molecular weights of POP used in the preparation of both components. The nonadditive dependence both of the concentration of EANC and of the stress-optical coefficient on composition confirms the heterogeneous character of the IPN structure.

The temperature and frequency dependences of the complex shear modulus G* and tan δ of mechanical losses of epoxy compositions with various fillers were studied. The method of Ninomiya‐Ferry applied to the reduced curves of frequency dependence of the effective part of the shear modulus was used to draw up relaxation time spectra for specimens with various concentrations of the filler. Regularities in the change of type and position of the spectral curves with increase in filler concentration were indicated. The findings make it possible to draw conclusions about the effect of the filler on the properties of the polymer matrix in the boundary layer and about changes in the conditions of the deformation of the polymer interlayers between the filler particles as compared with the deformations in bulk specimens.

SynopsisThe temperature dependences of elastic moduli, loss moduli, and mechanical loss angle tangent were investigated for the interpenetrating polymer networks: polyurethane-polyurethane acrylate by the method of dynamic mechanical spectroscopy (DMS). The segregation degree of components due to phase separation have been calculated from the parameters of relaxation maxima. An essential change was found in the segregation degree of components with the curing sequence of individual networks being changed. It was shown that, with the conditions and sequence of IPN formation changed, the phase separation degree can be fixed at a particular stage, i.e., the structures with a different segregation degree of components are obtainable. For the IPNs under investigation the variation of elastic moduli of the composites proved possible by fixing the separation degree of components.

synopsisThe temperature and frequency dependences of complex shear modulus and mechanical losses were studied for epoxy resin composition in the presence of different amounts of quartz and polystyrene fillers. The data obtained were analyzed by the use of the Williams-Landell-Ferry method. It was shown that in the mechanical behavior of filled polymers, except for the well-known temperature-time analogy there exist some lows connected with the presence of filler. The change in filler concentration leads to the same change in the real part of complex modulus as change in frequency (concentration-time analogy), and change in temperature is equivalent to concentration change (temperature-concentration analogy). The existence of these analogies is explained by a change in deformation conditions for polymeric matrix in the presence of different amount of filler, by the existence of surface layers of polymer at the interface with solid filler, and by peculiarities of the mechanical behavior of filler. It is also established that the thickness of surface layer which was determined from experimental data depends on temperature and has an extremum in the temperature region of the a-transition.

SynopsisTemperature dependences of real E' and imaginary E" parts of the complex dynamic modulus for new types of so-called segregated networks were investigated. These networks are formed by three different elastic active network chains which chemically interact one with another, distinct from interpenetrating networks. Networks based on oligourethane acrylate, methyl methacrylate, methacrylic acid, and epoxy resin taken at various ratios were investigated. The viscoelastic characteristics were determined on different stages of the network structure formation. For such networks, a very wide peak E" is typical, which is connected with a high degree of microphase segregation.The mutual influence of the constituent networks on their relaxation maxima was observed.