MECHANODESTRUCTION OF ISOPRENE RUBBER. PART 3. KINETICS OF OXIDATIVE DESTRUCTION

Continuation of studies of changes in molecular parameters, in particular, the molecular weight (MM) during the plasticization (P) of SKI-3 isoprene rubber. The kinetics of oxidative destruction (OD) in the temperature range (T) 30-130 °C and time (t) 30–600 s were studied in detail. Plasticization of rubber, as before, was carried out in a laboratory rubber mixer of the company «NFM», and gel chromatographic studies were carried out on a gel chromatograph of the company «Waters». The speed constant OD K0 decreases in absolute value with a decrease in T and an increase in t. The calculated effective activation energy of OD Eeff decreases from 24,4 to 13 kJ/mol in the studied t range. The influence of the oxygen diffusion process on the kinetic features of the OD of SKI-3 at Р is pointed out.

Influence of Disinfectants on Airport Conveyor Belts

The coronavirus disease has influenced almost all of our everyday activities. Traveling and transportation have been influenced significantly and there is no doubt that air transportation has been restricted and therefore reduced considerably. It is predicted that the change back to pre-pandemic conditions will take several years, and so it is a reasonable assumption that disinfectants will be used more frequently for a long time. The presented article initially deals with the possible impacts of the pandemic on aircraft infrastructure—namely, on the influence of disinfectants on the rubber materials used, for example, in conveyor belts. The proposed methodology is based on the Weibull analysis for conveyor belt lifetime prediction regarding the impact of disinfectants. The Weibull distribution is a continuous probability distribution that can be applied as a theoretical model for statistical data processing. It was named after Weibull, who suggested shape, scale, and location parameters that made the distribution meaningful and useful. Currently, this distribution is applied in many areas, such as biology, economics, and hydrology. In engineering applications, it can be used for reliability and survival analysis. It is used mainly in cases where failure time is dependent on the operating hours, cycles, or age of the component. In the reliability area, it can be used, for example, to predict the lifetime or failure time of a component. To show the consequences of material changes due to the use of disinfectants, this article also presents a CAE (Computer Aided Engineering) analysis that was used for the evaluation of other hyperelastic material characteristics. This research is based on the results of experimental measurements, during which the influence of the types of disinfectant commonly used for the elimination of the coronavirus disease on airport conveyor belt rubber segments was tested. From the performed analysis, it was found that the influence of disinfectants on the material characteristics, including material hardness, elasticity, and static and dynamic loading, could be significant. Therefore, the probability of mechanical damage to the rubber part of the conveyor belt becomes higher, and time intervals for the maintenance or repair of airport conveyor belts should be considered.

Design and Experiment of Inerter-Rubber Vibration Isolator Based on Parallel Inerter-Spring-Damper System

Since an inerter has been widely used in the field of vibration isolation, the combination of the inerter and the rubber part inevitably becomes a trend. In this work, a parallel inerter-spring-damper system (II-ISD) was introduced and analyzed for its performance on vibration isolation. Then, the optimal inertance-mass ratio and the frequency ratio at the minimum transmissibility were obtained. Based on the II-ISD system, an integrated vibration isolator was designed where the rubber part paralleled to the inerter, which was named as the inerter-rubber vibration isolator (IR). Then, its mechanical properties were simulated, and the mathematical model was established by considering the vibration isolation performance and the service life. Afterward, it was optimized by a programmed multi-objective genetic algorithm, and the optimal design parameters of IR were got finally. The experimental prototype of IR was processed, and its performance experiment was performed on the Mechanical Testing System (MTS) test bed. Experimental results show that the theoretical model of IR based on the II-ISD system is accurate; the resonant peak of IR is clearly lower than that of the rubber vibration isolator; the natural frequency decreases obviously. This work provides a design method for the serial product development, which has a practical engineering significance.

Evaluation of the strength characteristics of non-metallic elements of the air suspension of machines under the influence of negative temperatures and aggressive environments

The operating conditions of non-metallic elements of the air suspension of road vehicles are analyzed. The influence of deicing agents and negative temperatures on non-metallic (rubber) elements of the pneumatic spring is studied. The methods of conducting tests to assess the effect of negative temperatures and aggressive environments on non-metallic elements of the air suspension are described. It is shown that the destruction of the microstructure is caused by the action of reagents on the rubber part of the pneumatic cylinder. Keywords: road vehicles, air suspension, rubber elements, negative temperatures, deicing agent

Resistance evaluation of nonmetallic elements of pneumatic suspension of machines to influence of negative temperatures

The operation conditions of nonmetallic elements of the pneumatic suspension of road-making machines have been studied and analyzed. Evaluation of the strength characteristics of the nonmetallic elements of the pneumatic suspension under the influence of negative temperatures was carried out. It was found out by experiments that the influence of negative temperatures resulted in an increase in stiffness of a rubber part of an air cell. It was determined that for increasing resistance of the nonmetallic elements of the pneumatic suspension to the influence of negative temperatures it was necessary to use anaerobic impregnating compounds.

Mechanodestruction of Isoprene Rubber. Part 1. Process Kinetics

A method is proposed that allows us to obtain the values of the rate constants (CR) of the processes of mechanodestruction (mechanical cracking) of kм, oxidative destruction of kо, and recombination of kр macromolecules, as well as the mass fractions of the corresponding fractions of φм, φо, and φр,r involved in the plasticization process (P) of SKI-3 isoprene rubber. The method is based on the selection of the values of these parameters that correspond to the previously obtained experimental data, using the previously obtained recurrent equations and a specially developed program. The dependences of the CR on the time P at 30oC are obtained, which allows us to describe the kinetics of the processes accompanying P at this temperature, and the changes in molecular mass (MM) in this process. It is shown that constant values of CR are established at large times of P. Refined explanations of the nature of the kinetics of the CR change at P are proposed. The MM value of SKI-3 macromolecules that have not undergone destruction is calculated, depending on the time of plasticization.