Rheological, mechanical, and adhesive properties have been studied of two‐phase polymer blends containing a liquid crystal copolyester of poly(ethylelene terephthalate) and p‐hydroxybenzoic acid plus isotactic polypropylene (PP) with varying compositions and concentrations of glass fibers. Perfect fibrillation of the disperse LC‐phase into the PP‐matrix in capillary flow was observed at LCP concentrations >20 wt% and temperatures >488 K. This effect leads to a decrease of blend viscosity and a reinforcing of the extrudate's mechanical characteristics. At the same time, more essential reinforcement is achieved by the simultaneous addition of the reinforcing agents both of the LCP and glass fibers. Processing of PP is not impaired. It was found that the adhesive strength increases substantially when the amount of LCP in the blend exceeds a definite level, corresponding to a phase inversion. The results are explained by the formation near the interface of two adhesion layers: the first is composed of pure LCP having a higher surface tension, whereas the second layer represents the blend of various compositions. At small amounts of LCP, the adhesion failure proceeds in the interphase between the LCP and the blend. After the phase inversion, where adhesion strongly increases, the failure of adhesion joints proceeds near the interface between LCP and the glass.

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 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.

The decrease in Young's modulus after mechanically loading particulate-filled composites serves as a measure of the fraction of debonded filler particles.For composites based on plasticized rubber and fine ammonium perchlorate these effects have been studied for various stresses and for both varying amounts and particle sizes of the filler.It was found that debonding filler particles during loading is strongly dependent both on the filler concentration and the particle size. Composites with small particles are characterized by higher stresses at which debonding takes place. The effects observed are supposed to be connected with different conditions of the stress distribution depending on the filler particle size and amount. Another reason is the varying fraction of the interphase zone formed at the filler-matrix boundary. KEY WORDS Filler debonding; particulate filled rubber; interphase zone; mechanical model; adhesion; mechanical properties; filler size and concentration effects; stress distribution. NOMENCLATUREThe tensile strength of the adhesion joint of the filler particle with the matrix The length of the cube rib modelling the filler in the model of filled polymer The thickness of the binder layer in the model The thickness of the binder layers between filler particles Diameter of the filler particle The modulus of elasticity of the binder The modulus of elasticity of the filler polymer The modulus of elasticity of the filled polymer in the presence of some debonded particles The modulus of elasticity of the cell in the model of filled polymer The modulus of elasticity of the j-th layer in the model Modulus of elasticity of the multiparticle model of filled polymer The modulus of elasticity of the multiparticle model in the presence of some debonded particles The number of the vertical row of cells in the multiparticle model The number of the horizontal row * Corresponding author. 317 Downloaded by [Michigan State University] at 01:35 04 February 2015 318