Papers by Author: J. Budinski-Simendić

Abstract: The aim of this contribution was to study the rubber elasticity of dry and swollen networks obtained by cyclotrimerization crosslinking reaction of isocyanate groups located at a linear telechelic network precursor. Telechelic diisocyanates were prepared in the undiluted state from 2,4-tolylene diisocyanate, α,ω,dihydroxypoly(oxypropylenes) and different contents of the monool component 2-(2-metoxyetoxy) ethanol. The network synthesis proceeded in a bulk. Detailed network topology was calculated by the theory of branching processes. The equilibrium swelling degree of prepared samples was related to the parameters, which are experimentally accessible for a network arising from an end-linking process using the Flory-Rehner theory. The experimental data for network modulus were compared with those arising from the "affine" model, "phantom’ model" and the model of constrained junctions.

Abstract: Properties of four materials based on styrene-butadiene rubber (SBR), one without filler and the other three with the same amount but different types of silica fillers, are investigated. The fillers used are Vulkasil S and two new fillers, differing in nano-structures: specific surface area and particle aggregate morphology. All other components in the material formulations are the same as well as the procedures of material preparation. Thermal and thermo-mechanical properties of all four materials are investigated by modulated differential scanning calorimetry (MDSC) and dynamic mechanical analysis (DMA). Morphology of the materials is studied using scanning electron microscopy (SEM). The results for glass transition temperature (Tg ) of gum rubber and three filled rubbers, obtained by MDSC are for all four materials Tg = -50±1 0C, and by DMA loss tangent measurements also for all of them Tg = -29±1 0C. It indicates no significant influence of active silica fillers on the rubber network segment dynamics, in the temperature range close to Tg of SBR. But, at higher temperatures MDSC gives insights into dynamic transitions that are under the influence of filler interactions and sensitive to filler structure. The difference in Tg results obtained for the same material by MDSC and DMA can be understood in terms of different sensitivity of network segment dynamics to conditions provided by those two measuring methods.

Abstract: Here, as part of our experimental investigations dealing with poly(urethane-isocyanurate) networks, we investigate model irregular networks with increasing amount of dangling chains. In our study such an irregular network topology was obtained by partial substitution of a diol for a monohydroxy component during the preparation of isocyanate terminated precursors. Telechelic diisocyanates were synthesized from aromatic diisocyanate (2,4-TDI), α,ω-dihidroxypoly (oxypropylene) (PPG 2000), and diethyleneglycolmonomethylether (an aliphatic low-molecularweight monool component). The networks in undiluted state were prepared by cyclotrimerisation, in the presence of a catalyst. The network properties were estimated by multiple extraction in solvent, differential scanning calorimetry and photoelastical measurements. Independently of mechanical testing, the fraction and concentration of dangling and elastically active network chains were evaluated by the theory of branching processes (cascade theory). The influence of dangling chains on the mechanical properties was analyzed.

Abstract: Silica fillers are used in rubber composites to modify their dynamic-mechanical properties. Three fillers are used: a commercial filler of precipitated silica type Vulkasil- S and two fillers obtained by its treatment in different ways: thermally and hydrothermally. The purpose is not only to obtain higher hysteresis of the composite at low temperatures and lower hysteresis at elevated temperature (which is optimal for good tire performance), but to understand the reasons of such changes in elastomer materials behavior and also possibilities to increase the corresponding trends. Both modified fillers exhibited required trends in comparison with the original commercial one. More detailed analyses of their dynamical behavior indicate interdependence between of filler particle size, morphology of particle aggregates and ratio of elastic to loss moduli, influencing all together the dynamic properties of products.

Abstract: This paper deals with the control of the adhesion strength in metal-elastomer joints by fillers and the use of rubber blends to produce advanced high performance adhesive systems. The curing behavior of rubber compounds and dynamic mechanical properties of crosslinked rubber composites were considered in this technologically applicable study. The effects of two types of reinforcing filler, used to increase the adhesion strength between steel and rubber matrix based on acrylonitrile-butadiene rubber (NBR) and chlorosulfonated polyethylene rubber (CSM) was investigated. Precipitated silica (with the average size of primary particle 15 nm) and diatomaceous earth (with the average size of primary particle 28 µm) were used for both rubber and its blend (NBR/CSM). The filler loading range was from 0 to 35 phr. The determination of curing characteristics was estimated by Monsanto Rheometer. The crosslink density of the rubber composites was determined by swelling measurement. Dynamic mechanical behavior was measured by mechanical spectroscopy (in a single cantilever bending mode).