Abstract
High compatibility and good rubber–filler interactions are required in order to obtain high quality products. Rubber–filler and filler–filler interactions can be influenced by various material factors, such as the presence of processing aids. Although different processing aids, especially the plasticizers, and their effects on compatibility have been investigated in the literature, their influence on rubber–filler interactions in highly active filler reinforced mixtures is not explicit and has not been investigated in depth. For this purpose, the influence of treated distillate aromatic extract (TDAE) oil content and its addition time on interactions between silica and rubber chains were investigated in this study. Rubber–filler and filler–filler interactions of uncured and cured silica-filled SBR/BR blends were characterized by using rubber layer L concept and dynamic mechanical analysis, whereas mechanical properties were studied by tensile test and Shore A hardness. Five parts per hundred rubber (phr) TDAE addition at 0, 1.5, and 3 min of mixing were characterized to investigate the influence of TDAE addition time on rubber–filler interactions. It was observed that addition time of TDAE can influence the development of bounded rubber structure and the interfacial interactions, especially at short time of mixing, less than 5 min. Oil addition with silica at 1.5 min of mixing resulted in fast rubber layer development and a small reduction in storage shear modulus of uncured blends. The influence of oil content on rubber–filler and filler–filler interactions were investigated for the binary blends without oil, with 5 and 20 phr TDAE content. The addition of 5 phr oil resulted in a slight increase in rubber layer and 0.05 MPa reduction in Payne effect of uncured blends. The storage tensile modulus of vulcanizates at small strains decreased from 13.97 to 8.28 MPa after oil addition. Twenty parts per hundred rubber (phr) oil addition to binary blends caused rubber layer L to decrease from 0.45 to 0.42. The storage tensile modulus of the vulcanizates and its reduction with higher amplitudes were incontrovertibly high among the vulcanizates with lower oil content, which were 13.57 and 4.49 MPa, respectively. When any consequential change in mechanical properties of styrene–butadiene rubber (SBR)/butadiene rubber (BR) blends could not be observed at different TDAE addition time, increasing amount of oil in blends enhanced elongation at break, and decreased Shore A hardness and tensile strength.
Highlights
Silica-filled rubber blend technology is of interest to the elastomer industries, especially to the tire manufacturers due to its potential usage for tire tread formulations [1,2].Chemical structure and microstructure of polymers, filler types, and filler characteristics mainly determine the type and strength of polymer–filler and filler–filler interactions [3].Silica is compatible to some degree with polar rubbers due to its highly polar structure, but it is not naturally compatible with non-polar rubbers such as styrene–butadiene rubber (SBR), butadiene rubber (BR), and natural rubber (NR)
Vulcanization characteristics of the silica-filled SBR/BR blends were characterized at 160 ◦ C by using a vulcameter Elastograph (Göttfert Werkstoff Prüfmaschinen GmbH, Buchen, Germany) in accordance with DIN 5329-2 [38] and vulcanization time t90 was determined for each compound
According to the results of treated distillate aromatic extract (TDAE) content influence in silica-filled SBR/BR blends, it can be claimed that high plasticizer contents can require longer mixing time to achieve maximum rubber–filler interactions in the system and result in reduction in bonded rubber layer on fillers
Summary
Silica-filled rubber blend technology is of interest to the elastomer industries, especially to the tire manufacturers due to its potential usage for tire tread formulations [1,2]. Bound rubber is defined as the structure formed by the attachment of polymer chains to the silica surface and this concept is commonly used to investigate polymer–filler interactions in filled rubber systems [13,14,15,16,17]. The compatibility of processing oils in different polymer systems were studied and their influence on dynamic and mechanical properties were the main focus of these studies considering the commercial applications [31,32,33,34]. Polymers 2021, 13, 698 analysis were carried out as supportive methods to study rubber–filler and filler–filler interactions and to estimate a possible correlation with rubber layer of silica-filled blends
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