E.V. Lebedev

Electrical and thermal conductivity of polymers filled with metal powders

Abstract The electrical and thermal conductivity of systems based on epoxy resin (ER) and poly(vinyl chloride) (PVC) filled with metal powders have been studied. Copper and nickel powders having different particle shapes were used as fillers. The composite preparation conditions allow the formation of a random distribution of metallic particles in the polymer matrix volume for the systems ER–Cu, ER–Ni, PVC–Cu and to create ordered shell structure in the PVC–Ni system. A model is proposed to describe the shell structure electric conductivity. The percolation theory equation σ ∼( ϕ − ϕ c ) t with t =2.4–3.2 (exceeding the universal t =1.7 value) holds true for the systems with dispersed filler random distribution, but not for the PVC–Ni system. The percolation threshold ϕ c depends on both particle shape and type of spatial distribution (random or ordered). In contrast to the electrical conductivity, the concentration dependence of thermal conductivity shows no jump in the percolation threshold region. For the description of the concentration dependence of the electrical and thermal conductivity, the key parameter is the packing factor F . F takes into account the influence of conductive phase topology and particle shape on the electrical and thermal conductivity.

Relaxation processes in hybrid organic-inorganic polymer nanosystems polymerized in situ

The relaxation processes of hybrid organic-inorganic polymer nanosystems (OIS) synthesized by joint polymerization of organic and inorganic components were studied using methods of differential scanning calorimetry (DSC), dynamic mechanical thermal analysis (DMTA), and broadband dielectric relaxation spectroscopy (DRS). The organic component was a mixture of two products: high-molecular-weight macrodiisocyanate (MDI) with low reactivity and low-molecular-weight isocyanate-containing modifier poly(isocyanate) (PIC) with high reactivity. Sodium silicate (SS) was used as inorganic component. The structures of the OIS obtained were in the form of hybrids with covalently connected building blocks and interpenetrating networks: weakly cross-linked network MDI/SS and highly cross-linked network PIC/SS. Depending on the MDI/PIC ratio, one of the networks was prevailing and created a continuous structure with domains of second network.PACS61.25.hk; 82.35.Lr; 64.70.pj

The anomalous behavior of physical-chemical parameters during polymerization of organic-inorganic polymer systems based on reactive oligomers

Abstract Dependencies of physical-chemical characteristics on structure development during polymerization of organic-inorganic systems (OISs) have been investigated. The non-monotonic behavior of the physical parameters has been found. This effect was explained by complicated structure of OISs, which consists of two interpenetrating hybrid organic-inorganic networks, which are characterized by different rate of the structure formation.

A modern approach in wood waste management: composites based on a novel copolyamide as matrix

In this study, the obtaining of some composite materials using wood chips as filler and a modified polyamidic polymer as thermoplastic matrix is presented. Characterization was carried out on composite samples by analysis of morphology, mechanical properties and thermal behaviour. It was observed that the tensile strength of composites decreased significantly with the increasing wood chips content. Still, even the bending strength is decreasing; it remains 2-8 times higher than that for the composites based on polyolefinic matrices. The thermal stability of the obtained composite materials is higher to that of the initial wood component.