Abstract
Blends composed of styrene butadiene rubber (SBR) and acrylonitrile-butadiene rubber (NBR) were fabricated by melt blending technique using two-roll mill blend machine. Cis- polybutadiene rubber (CBR) was used as a compatibilizer for enhancing the homogeneity between SBR and NBR phases in blends. Although, no previous reports were found to discuss improving electrical properties of vulcanized SBR/NBR blends using unfilled rubber system (i.e. no fillers incorporated). Raman spectra and SEM images indicate that a significant compatibility within the rubber matrix is observed, due to using CBR compatibilizer. The effect of SBR/NBR blend ratio on curing characteristics, physico-mechanical properties, and physicochemical properties (e.g. network characteristics and thermodynamic parameters) were studied. SBR/NBR blend showed comparatively better mechanical properties, compared to each other individually rubber system. Curing parameters e.g. Mooney viscosity and hardness were increased, while a reduction in cure time and specific gravity was observed with increasing SBR ratio in blends. Results revealed that increasing SBR resulted in an enhancement of the tensile strength, modulus at 300 % and elongation at break up to 40 phr, and then gradually decreased. The TGA results indicated that SBR/NBR blends were thermally decomposed at a temperature range of 340-520°C. The notable decrease of DC conductivity (σdc) of vulcanized blends is owing to the decrease of NBR, which is a polar portion and is responsible for increasing the conductivity of vulcanized blends. This proved that the targeted industrial applications for vulcanized blends are entirely depending upon SBR/NBR blend in elastomers matrix.
Highlights
Rubber is an important class of high polymers mostly organic; composed of long chain molecules consisting of repeating units on a backbone of carbon atoms [1]
These results are consistent with obtained results of Zulkepli and Ismail [22]. They have revealed that MH was slightly increased with NBR content in SBR/NBR blends owing to the contribution of nitrile group in the crosslinking process of blend
Low NBR content causes less extent of engagement of SBR/NBR blends which results in an increase in Mooney viscosity (MV), ML values and a decrease in MH, TS2 and T90 values (Figs. 2a-c), and this behavior is used for accelerating the vulcanization process
Summary
Rubber is an important class of high polymers mostly organic; composed of long chain molecules consisting of repeating units on a backbone of carbon atoms [1]. Many research groups have recently conducted intensive studies on specific physical properties e.g. miscibility and phase behavior of SBR/NBR polymer blends [2]-[4]. Part of these polymers is immiscible; compatibilizers are included to overcome the weak interfacial adhesion resulting in inferior mechanical properties. NBR is synthetic elastomers known as a polar rubber that has adequate mechanical and electrical properties [13]-[16] It has a good anti-solvent property, compared to SBR [16]. We are investigating the improvement of physical and physicochemical properties of vulcanized SBR/NBR blends compatibilized with CBR, owing to alteration of blend ratio of elastomers. DC-electrical conductivity has been discussed to determine the initial electrical properties of the prepared vulcanized SBR/NBR blends, while intensive electrical properties will be discussed in details in an extended work
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