RHEOKINETIC AND MORPHOLOGICAL FEATURES OF THE REACTION FORMATION OF A POLYMER COMPOSITE MATERIAL BASED ON IMPACT-RESISTANT POLY(METHYL METHACRYLATE). MODEL AND APPLIED ASPECTS

Abstract

Based on the experimental data on the rheology of dispersions of hydrophobic aerosil (Am) in a low molecular weight hydrocarbon medium, the possibility of using a «micellar» mechanism for the formation of a bulk structure for such dispersions is considered. A model of such a structure before, during and after shear deformation is proposed, which makes it possible to interpret experimental data on the rheology of dispersed systems. The results of the study of rheokinetics are presented in a new visio – from the point of view of self-organization under the influence of the shear field. The PMMA–PU–Am system was considered as a polymer composite (PC), in which the matrix is the poly(methyl methacrylate) (PMMA) being modified, and the dispersed phase is a mixture of polyurethane (PU) with Am. It has been shown that during the reaction formation of this composition, the conditions of shear deformation of the system correspond to those at which self-organization and fixation of the coagulation rheopex structure of the nanofiller in PC is possible at the moment of reaching very high viscosity values (gel-point), when diffusion processes will be practically frozen. Two concentration regions of Am were predicted (before and after the percolation threshold), where an enhancement of the mechanical characteristics of PMMA can be expected. The relationship between the rheokinetics of the formation of a linear PMMA–crosslinked PU mixture in the presence of different amounts of oligomeric azo-initiator containing fragments of the polyurethane chain and groups capable of initiating radical polymerization of methyl methacrylate and the process of phase separation, morphology and mechanical properties of the final products has been established. It was shown that the time of phase separation and gelation are interrelated and there is in a simple dependence on the concentration of the azo-initiator. Such an initiator affects the structural-rheological transitions in the system and leads to the formation of morphology with smaller domains. The most stable system with the best dispersion of polyurethane in polymethyl methacrylate is a mixture containing 0.002 mol/L of azo-initiator, which has improved mechanical properties and increased impact viscosity.