TY - BOOK

T1 - Influence of Different Manufacturing Methods and Conditions on the Fatigue Behavior of Nitrile Butadiene Rubber

AU - Gehling, Tobias

N1 - embargoed until 18-06-2029

PY - 2024

Y1 - 2024

N2 - A critical and increasingly important factor for the sustainability of the elastomer industry is fatigue resistance, which significantly affects the lifespan of rubber components. This resistance can be influenced at various stages throughout a product's development, from the initial compound formulation and processing parameters to the conditions under which the product is used. Therefore, the aim of this research was to explore specific factors and understand their impact on fatigue crack growth. In particular, the study focused on process parameters such as curing time and temperature, molding technology, and the choice of filler. To achieve this, test specimens were created using different parameters with a specially designed mold and then thoroughly characterized. To determine the fatigue properties for this study, fatigue crack growth was measured in pre-notched samples. Characterizations were conducted on sulfur cured nitrile butadiene rubber (NBR) specimens produced at various curing times and temperatures by means of both injection molding and compression molding. Additionally, two materials with different fillers (carbon black and silica) but identical filler content by mass percentage were examined. The findings indicate that curing time and temperature in injection molding notably affect the crack growth resistance of a vulcanizate. Increasing curing time leads to higher crosslink density, a decrease in polysulfidic crosslinks, and consequently, an increase in crack growth rate. The curing temperature exhibits an opposite trend; a rising temperature reduces crosslink density, thus enhancing crack growth resistance. A similar trend was observed for other mechanical properties and the transmitted torque from the Rubber Process Analyzer experiments. Regarding the molding technique, stiffening in the compression molded material and slower crosslinking kinetics were observed, but it did not affect the material's fatigue resistance. Referring to literature, this was associated with an increase in the number of entanglements present in the material. The filler comparison highlighted the impact of filler-polymer interactions on all mechanical properties, including fatigue, showcasing significantly reduced properties in non silanized silica-filled material.

AB - A critical and increasingly important factor for the sustainability of the elastomer industry is fatigue resistance, which significantly affects the lifespan of rubber components. This resistance can be influenced at various stages throughout a product's development, from the initial compound formulation and processing parameters to the conditions under which the product is used. Therefore, the aim of this research was to explore specific factors and understand their impact on fatigue crack growth. In particular, the study focused on process parameters such as curing time and temperature, molding technology, and the choice of filler. To achieve this, test specimens were created using different parameters with a specially designed mold and then thoroughly characterized. To determine the fatigue properties for this study, fatigue crack growth was measured in pre-notched samples. Characterizations were conducted on sulfur cured nitrile butadiene rubber (NBR) specimens produced at various curing times and temperatures by means of both injection molding and compression molding. Additionally, two materials with different fillers (carbon black and silica) but identical filler content by mass percentage were examined. The findings indicate that curing time and temperature in injection molding notably affect the crack growth resistance of a vulcanizate. Increasing curing time leads to higher crosslink density, a decrease in polysulfidic crosslinks, and consequently, an increase in crack growth rate. The curing temperature exhibits an opposite trend; a rising temperature reduces crosslink density, thus enhancing crack growth resistance. A similar trend was observed for other mechanical properties and the transmitted torque from the Rubber Process Analyzer experiments. Regarding the molding technique, stiffening in the compression molded material and slower crosslinking kinetics were observed, but it did not affect the material's fatigue resistance. Referring to literature, this was associated with an increase in the number of entanglements present in the material. The filler comparison highlighted the impact of filler-polymer interactions on all mechanical properties, including fatigue, showcasing significantly reduced properties in non silanized silica-filled material.

KW - fatigue behavior

KW - elastomeres

KW - crosslink-density

KW - crack growth resistance

KW - swelling

KW - molding technology

KW - Ermüdung

KW - Elastomere

KW - Risswachstum Resistenz

KW - Vernetzungsdichte

KW - Mehrstufige Quellung

KW - Herstellungsverfahren

U2 - 10.34901/mul.pub.2024.216

DO - 10.34901/mul.pub.2024.216

M3 - Doctoral Thesis

ER -