Properties of carboxylated acrylonitrile/butadiene rubber containing „in situ” synthesized silica fillers
Polimery 2002, No 9, 643
From silica precursors we synthesized silica fillers in sol-gel reaction in the carboxylated acrylonitrile/butadiene rubber (XNBR). N-2-aminoethyl-3-aminopropyl-trimethoxysilane (DAMS) and tetraethoxysilane (TEOS) were used as fillers' precursors. It has been found that DAMS is a substance crosslinking XNBR. The network points are silsesquioxanes' domains containing amide as well as ionic bonds. Some part of points (-30%) decompose under ethylenediamine treatment. The bigger DAMS content the bigger crosslinking density of elastomer as well as the stress at suitable elongation and tensile strength (Tables 2 and 4). The dynamic properties measurements show that organosilica compounds do not influence glass transition temperature of elastomer (Table 6) but in the range of 30—40 °C the second maximum appears which is a transition connected to ionic aggregates activity. Addition of a mixture of DAMS + TEOS to the elastomer causes the increase of crosslinking of silsesquioxanes' domains and the filler shows tendency to creation of its own structure (Fig. 2). 29Si NMR results show that mostly trifunctional structures Q3 are obtained for equal ratio of silanes (1:1) but tetrafunctional structures Q4 are also present (Table 1). The increasing of tetrafunctional structure Q4 content, that is a synthesis of a filler with DAMS + TEOS mixture, leads to the increase of stress at suitable elongation, and tensile strength (Table 5).
Keywords: silica filler, „in situ” synthesis, N-2-aminoethyl-3-aminopropyltrimethoxysilane, tetraethoxysilane, carboxylated acrylonitrile-butadiene rubber, crosslinking, vulcanizates properties