ADVANCED MATERIALS FOR A MORE EFFICIENT AND SUSTAINABLE TIRE TREAD. SOS-NEUMAT.
Program: Challenges Collaboration 2019
Reference: RTC2019-006975-4
RESOLUTION Date: 10/20/2020
Execution date: 07/01/2020 – 06/30/2020-30/06/2023
The tread is probably the most critical part of the tire, the thickest and the one that most influences its performance. It is the only point of contact of the vehicle with the ground, and therefore it is the part that, in service, suffers the most wear (abrasion) and must provide the vehicle’s grip and traction. In addition, it is the part that contributes most to energy losses in vehicle motion through rolling resistance (amount of energy absorbed by the tire when rolling under the weight of the vehicle). It is estimated that a 10% reduction in rolling resistance means a 1.5-2.0% reduction in a car’s fuel consumption. [International Council on Clean Transportation (ICCT) (2012), “Influence of rolling resistance on CO2,” Series: Worldwide Harmonized Light Vehicles Test Procedure (Wltp), Working Paper 2012-6, ICCT, Washington, DC]
The reinforcing filler, together with the polymer and the vulcanization system, are the main ingredients of the tread of any tire, and the ones that most influence its performance.
According to their chemical nature, there are two main types of reinforcing fillers: black (hydrophobic) and white (hydrophilic). The first group includes carbon black and the second group includes precipitated silica.
Carbon black, a material produced by the incomplete combustion of petroleum products, is the main reinforcing filler used in tires, constituting more than 90 % of the reinforcing filler consumption in 2016 [Paul Ita; “Outlook for Reinforcing Fillers & Rubber Chemicals”; Paper at Tire Technology Expo, 2018].
Precipitated silica is mainly used in passenger car tread, since a Michelin patent [R. Rauline (to Michelin), Ep 0501 227 A1, Feb. 12, 1992; (U.S. 5,227,425, July 13. 1993)] demonstrated that high dispersion precipitated silica reinforced compounds, with proper formulation and mixing cycle [Byers J.T., “Fillers for balancing passenger tire tread properties”, Rubber. Chem. Technol, 75 (2002) 527], provide improvements in rolling resistance, grip and braking distance [European Parliament (2008), “Type approval requirements for the general safety of motor vehicles”, IP/A/IMCO/IC/2008-112, Policy Department of Economic and Scientific Policy, European Parliament, Brussels].
This improvement in properties has not yet been achieved in TBR (“Truck-Bus Radial”) heavy vehicle tread formulations, where the use of natural rubber (NR) is necessary due to its intrinsic properties of: excellent fatigue performance, reduced heat build-up from flexing and increased resistance to tearing when hot.
Obtaining a suitable compound based on natural rubber and precipitated silica could mean the development of a more sustainable and efficient tire because silica-reinforced compounds have higher hysteresis at high frequencies, but lower hysteresis at low frequencies compared to carbon black reinforcement. This results in compounds with lower rolling resistance and better levels of traction and grip [OECD (2014), Nanotechnology and Tyres: Greening Industry and Transport, OECD Publishing]. Moreover, it should not be forgotten that carbon black comes from oil, a non-renewable energy source.
This project aims to evaluate the performance of new experimental IQE silicas (with and without surface treatment) as reinforcing fillers in heavy vehicle treads (mainly based on the use of natural rubber as the main polymer) in order to identify the best candidates for this purpose. Although potentially precipitated silica would provide better characteristics, as evidenced in light tire tread, there are still technological drawbacks that have prevented its use in heavy tire tread. Investigations using commercial precipitated silica have resulted in good rolling resistance estimators, but poor values for other properties such as abrasion resistance. One of the main arguments put forward to justify this low abrasion resistance is the difficulty of silanizing and dispersing the silica in the natural rubber during the mixing process. For this reason, this project also aims to evaluate surface-treated silicas before introducing them into the mixture.
Through this project, different white IQE fillers (treated and untreated) and with different properties will be examined to understand the reinforcement mechanism in NR-based rubber formulations in order to select the rubber formulation that yields the best final performance properties. To this end, a reference formula and mixing cycle with the standard market reinforcing filler (carbon black) and another formula and cycle suitable for the use of white fillers must be defined and implemented. The objective of these references is to identify and quantify the improvement/improvement of the properties induced by each load. In addition, it is considered necessary to increase the capabilities of the project members in the characterization of the compounds, especially with regard to charge dispersion measurements, since this is considered a determining characteristic when it is intended to mix a hydrophobic material (natural rubber) with another hydrophilic material (precipitated silica). Finally, it is known that in order for the reinforcing filler to show its best properties, it will be necessary to optimize the ingredients and the mixing cycle. Therefore, in the last phase of the project, the reinforcing fillers showing the best balance of properties will be selected for further study to explore the consequences of varying the main formulation and mixing factors.
Industrias Químicas del Ebro
Aragon Institute of Technology
TOTAL PROJECT BUDGET: 755,126 €.
TOTAL BUDGET ITAINNOVA: 273,484 €.
TOTAL PROJECT GRANT: 273,484 €.
TOTAL PROJECT LOAN: 457,559.90 €.
TOTAL FINANCING ITANNOVA: 273,484 €.
Funded by: Ministry of Science, Innovation and Universities – State Research Agency/ SOS- NEUMAT Project – RTC2019-006975-4.
