A Detailed Study of the Effect of Cyclic Loading on the Thermal Expansion Coefficient of Reinforced Styrene Butadiene Rubber as a Function of Different Carbon Black Tyres

Kód výsledku v IS VaVaI

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Výsledek na webu

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DOI - Digital Object Identifier

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Jazyk výsledku

angličtina

Název v původním jazyce

A Detailed Study of the Effect of Cyclic Loading on the Thermal Expansion Coefficient of Reinforced Styrene Butadiene Rubber as a Function of Different Carbon Black Tyres

Popis výsledku v původním jazyce

The fact that heat is generated in viscoelastic materials such as rubber by the gradual dissipation of energy under cyclic loading is well known as self-heating. In addition, rubber components are reinforced with various types of fillers, the most commonly used of which are carbon black (CB), which significantly affect the viscoelastic properties and therefore the heat development. It must also be taken into account, that in real applications the rubber is exposed to different ambient temperature conditions. In addition, fatigue degradation of the rubber matrix occurs under cyclic loading. The temperature effect, whether by ambient or self-heating or a combination of both, causes thermal expansion and directly affects the dimensional stability of the rubber component, which can affect both the accuracy and functionality of the application and, in particular, the life of the rubber product. The coefficient of thermal expansion (CTE) is then a physical parameter used to determine the rate of expansion of the material as a function of temperature and describes the key properties of the rubber in this respect. The CTE then determines whether damage to the rubber can occur due to thermal stress. Therefore, knowledge of the CTE is a prerequisite for selecting the right material for individual applications and thus ensuring its faultless functionality.The determination of CTE is clearly defined by ASTM D696 and ASTM E83, which are based on the principle of measuring CTE under quasi-static loading and do not take into account the actual degradation of the rubber matrix under cyclic loading such as e.g. the Payne or Mullins effect. The Payne effect is the most dominant phenomenon in CB filled rubber causing deformation changes in the microstructure of the material, which are related to the breaking and restoration of weak physical bonds connecting the filler clusters, or filler-filler interactions. The Payne effect occurs at very small deformations in the range of approximately 0.1-20 %. In contrast, the Mullins effect occurs independently of the applied strain and characterises the softening of the rubber that occurs in both filled and unfilled materials. It can be assumed that the disruption of the filler-filler interaction will result in a change in the heat transfer in the rubber matrix, which will result in a change in the dilation due to a change in the stresses generated in the region of the broken bonds, where this will be reflected in a change in the CTE. It can be expected that the CTE values will depend on the Payne effect of the respective CB types, but the absolute value of the change in CTE will be very small. The literature data related to this topic only concerns the effect of CB type and amount on CTE for materials without loading history.Therefore, this work is the first to investigate the effect of different types and amounts of CB in styrene-butadiene rubber (SBR) on CTE as a function of cyclic loading.Considering the necessity of high accuracy of CTE determination to capture the effect of bond breaking in the filler-filler interaction, a completely new unique measurement methodology was developed as well as an experimental device was exclusively designed for the determination of CTE in rubber. Both the methodology and the testing device will be presented for the first time and the principle discussed in detail in the context of this study. As conclusion, the dependence of CTE on the type and amount of CB will first be discussed, with the most significant part of the final discussion being the presentation of the relationship of cyclic loading in the Payne effect region to CTE. The resulting relationships and values thus form a unique set describing the thermal properties of SBR reinforced with different type and quantity of CB in relation to the applied cyclic loading.

Název v anglickém jazyce

A Detailed Study of the Effect of Cyclic Loading on the Thermal Expansion Coefficient of Reinforced Styrene Butadiene Rubber as a Function of Different Carbon Black Tyres

Popis výsledku anglicky

The fact that heat is generated in viscoelastic materials such as rubber by the gradual dissipation of energy under cyclic loading is well known as self-heating. In addition, rubber components are reinforced with various types of fillers, the most commonly used of which are carbon black (CB), which significantly affect the viscoelastic properties and therefore the heat development. It must also be taken into account, that in real applications the rubber is exposed to different ambient temperature conditions. In addition, fatigue degradation of the rubber matrix occurs under cyclic loading. The temperature effect, whether by ambient or self-heating or a combination of both, causes thermal expansion and directly affects the dimensional stability of the rubber component, which can affect both the accuracy and functionality of the application and, in particular, the life of the rubber product. The coefficient of thermal expansion (CTE) is then a physical parameter used to determine the rate of expansion of the material as a function of temperature and describes the key properties of the rubber in this respect. The CTE then determines whether damage to the rubber can occur due to thermal stress. Therefore, knowledge of the CTE is a prerequisite for selecting the right material for individual applications and thus ensuring its faultless functionality.The determination of CTE is clearly defined by ASTM D696 and ASTM E83, which are based on the principle of measuring CTE under quasi-static loading and do not take into account the actual degradation of the rubber matrix under cyclic loading such as e.g. the Payne or Mullins effect. The Payne effect is the most dominant phenomenon in CB filled rubber causing deformation changes in the microstructure of the material, which are related to the breaking and restoration of weak physical bonds connecting the filler clusters, or filler-filler interactions. The Payne effect occurs at very small deformations in the range of approximately 0.1-20 %. In contrast, the Mullins effect occurs independently of the applied strain and characterises the softening of the rubber that occurs in both filled and unfilled materials. It can be assumed that the disruption of the filler-filler interaction will result in a change in the heat transfer in the rubber matrix, which will result in a change in the dilation due to a change in the stresses generated in the region of the broken bonds, where this will be reflected in a change in the CTE. It can be expected that the CTE values will depend on the Payne effect of the respective CB types, but the absolute value of the change in CTE will be very small. The literature data related to this topic only concerns the effect of CB type and amount on CTE for materials without loading history.Therefore, this work is the first to investigate the effect of different types and amounts of CB in styrene-butadiene rubber (SBR) on CTE as a function of cyclic loading.Considering the necessity of high accuracy of CTE determination to capture the effect of bond breaking in the filler-filler interaction, a completely new unique measurement methodology was developed as well as an experimental device was exclusively designed for the determination of CTE in rubber. Both the methodology and the testing device will be presented for the first time and the principle discussed in detail in the context of this study. As conclusion, the dependence of CTE on the type and amount of CB will first be discussed, with the most significant part of the final discussion being the presentation of the relationship of cyclic loading in the Payne effect region to CTE. The resulting relationships and values thus form a unique set describing the thermal properties of SBR reinforced with different type and quantity of CB in relation to the applied cyclic loading.

Druh

O - Ostatní výsledky

CEP obor

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OECD FORD obor

20501 - Materials engineering

Projekt

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Návaznosti

I - Institucionalni podpora na dlouhodoby koncepcni rozvoj vyzkumne organizace

Rok uplatnění

2024

Kód důvěrnosti údajů

S - Úplné a pravdivé údaje o projektu nepodléhají ochraně podle zvláštních právních předpisů