Abstract
The application of wastes as a filler/reinforcement phase in polymers is a new strategy to modify the performance properties and reduce the price of biocomposites. The use of these fillers, coming from agricultural waste (cellulose/lignocellulose-based fillers) and waste rubbers, constitutes a method for the management of post-consumer waste. In this paper, highly-filled biocomposites based on natural rubber (NR) and ground tire rubber (GTR)/brewers’ spent grain (BSG) hybrid reinforcements, were prepared using two different curing systems: (i) sulfur-based and (ii) dicumyl peroxide (DCP). The influence of the amount of fillers (in 100/0, 50/50, and 0/100 ratios in parts per hundred of rubber) and type of curing system on the final properties of biocomposites was evaluated by the oscillating disc rheometer, Fourier-transform infrared spectroscopy, thermogravimetric analysis, scanning electron microscopy, swelling behavior, tensile testing, and impedance tube measurements. The results show, that the scorch time and the optimum curing time values of sulfur cured biocomposites are affected by the change of the hybrid filler ratio while using the DCP curing system, and the obtained values do not show significant variations. The results conclude that the biocomposites cured with sulfur have better physico-mechanical and acoustic absorption, and that the type of curing system does not influence their thermal stability. The overall analysis indicates that the difference in final properties of highly filled biocomposites cured with two different systems is mainly affected by the: (i) cross-linking efficiency, (ii) partial absorption and reactions between fillers and used additives, and (iii) affinity of additives to applied fillers.
Highlights
Growing global consumerism is one of the reasons for the accumulation of a significant amount of post-production, post-consumer, and agricultural waste
The results showed that ground tire rubber (GTR) presents a higher affinity to natural rubber (NR) than brewers’ spent grain (BSG)
Natural rubber-based materials filled with BSG, GTR, and BSG/GTR were prepared cross-linked structure can act avoiding the collapse of the voids and occlusions, this effect would be lower in the case of dicumyl peroxide (DCP)
Summary
Growing global consumerism is one of the reasons for the accumulation of a significant amount of post-production, post-consumer, and agricultural waste. The bio-fillers with these features can be used to partially or completely replace commonly applied fillers in the rubber industry such as carbon black (petrochemical-based product) and silica, which are non-degradable and consume high amounts of energy during production These aspects motivate scientists to study the incorporation of bio-based materials as modifiers of natural rubber and synthetic elastomers, obtaining biocomposites [5,6,7,8]. It is possible that the filler enhances a phenomenon occurring for natural rubber during a tensile test, which is strain-induced crystallization It locally amplifies the stress for macromolecular chains (shifting the crystallization process) resulting in higher stress and faster break of the structure (lower elongation at break). Subsequently were compared with biocomposites cured with dicumyl peroxide (DCP) in terms of processing, morphology, as well as mechanical and thermal properties
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