Thermogravimetric analysis (TGA) and 14C techniques were compared for the determination of the biomass content of end-of-life tires (ELTs). Samples of different types (of ELTs) were prepared, and the biomass fraction of each sample was measured using the two methods (TGA and 14C). Six reference samples were also prepared with known quantities of natural rubber and stearic acid in order to establish the calibration curve necessary for the thermogravimetric analysis and to verify the accuracy of the results of the 14C analysis. The conclusions were that the 14C technique is the more valid, reliable, and precise method for determining the biomass content of end-of-life tires, since the results of the 14C tests of the reference samples coincided perfectly with the actual natural rubber and stearic acid content. On the other hand, the results of the thermogravimetric method differed considerably from the known natural rubber content of the reference samples as well as from the results of the 14C technique. This method is therefore not appropriate for use in determining the biomass content of end-of-life tires.
There are currently many well-established applications for recycled rubber from end-of-life tires (ELT), but it is essential to investigate and seek new approaches to enhance the value of these products. Recent developments in new technologies and innovative recycling and devulcanization processes have opened up new perspectives for ELT crumb rubber. To promote the use of these products in newly added value applications, it is essential to develop and optimize methods that allow the characterization of parameters related to the ultimate properties of potential final applications. In this respect, a novel characterization methodology based on advanced 1H double-quantum (DQ) nuclear magnetic resonance experiments has been applied for the first time to quantify the key parameters that characterize the structure of ELT crumb rubber after diverse recycling processes: from simple mechanical grinding to complex devulcanization methods. This experimental approach enables the quantification of parameters that define the network structure of rubber, such as the nonelastic network defects (sol fraction, dangling chain ends, loops), the cross-link density, and the heterogeneity of the network, directly from rubber granulate and powder (without any additional sample preparation steps), overcoming most of the drawbacks and uncertainties that limit the application of traditional rubber characterization methods (e.g., equilibrium swelling experiments). By applying this experimental approach, it is possible to identify and quantify the actual technical limits for a complete selective devulcanization process of ELT crumb rubber.
Sustainable composite brake pads were processed by employing recycled end-of-life tire (ELT) rubber particles obtained by means of cryogenic grinding and ambient grinding. The effect of the grinding mechanism and concentration of ELT rubber particles was then reported. From the friction result test, better behavior in terms of coefficient of friction (COF) was obtained when 3% of ELT rubber particles were introduced into the composite. It was demonstrated that the size of the particles is not as determinant as the friction mechanism in the wear properties of the sustainable brake pads. Whereas, while increasing the ELT rubber particle size acts as detrimental to the COF either in the ambient or cryogenic grinding, at high friction distances, the better adhesion of the particles because of the rough surface of the particles subjected to ambient grinding enhances the long-life behavior of the composite brake pads.
There is a growing interest in multifunctional composites and in the identification of novel applications for recycled materials. In this work, the design and fabrication of multiple particle-loaded polymer composites, including micronized rubber from end-of-life tires, is studied. The integration of these composites as part of ultrasonic transducers can further expand the functionality of the piezoelectric material in the transducer in terms of sensitivity, bandwidth, ringing and axial resolution and help to facilitate the fabrication and use of phantoms for echography. The adopted approach is a multiphase and multiscale one, based on a polymeric matrix with a load of recycled rubber and tungsten powders. A fabrication procedure, compatible with transducer manufacturing, is proposed and successfully used. We also proposed a modelling approach to calculate the complex elastic modulus, the ultrasonic damping and to evaluate the relative influence of particle scattering. It is concluded that it is possible to obtain materials with acoustic impedance in the range 2.35–15.6 MRayl, ultrasound velocity in the range 790–2570 m/s, attenuation at 3 MHz, from 0.96 up to 27 dB/mm with a variation of the attenuation with the frequency following a power law with exponent in the range 1.2–3.2. These ranges of values permit us to obtain most of the material properties demanded in ultrasonic engineering.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.