Exploring crosslink density in rubber vulcanisates - a comprehensive analysis using a dynamic mechanical analyser and an insight into mechanical properties

Abstract

A comprehensive analysis of crosslink density is crucial for understanding the functional characteristics of rubber vulcanisates. This study discusses a quantitative methodology for assessing crosslink density through the application of a Dynamic Mechanical Analyser (DMA), in which the storage modulus is evaluated during a temperature sweep on cured vulcanisate samples. To confirm the DMA findings, the Molecular Weight Between Crosslinks (Mw) and crosslink density derived from DMA were compared with results obtained from the solvent method, utilising the Flory-Rehner approach. The solvent method involved refining the swelling and drying periods for natural rubber (NR) matrices. The investigation covered the diverse vulcanisation systems, including conventional, semi-efficient, and efficient systems, and altering the dosage of the Zinc oxide activator. Additionally, the study delved into the influence of crosslink density on mechanical properties such as hardness and stress-strain characteristics. This was accomplished by manipulating the cure time of rubber vulcanisates, systematically adjusting it both below and above the tC90 determined through rheometric studies, covering a broad spectrum of intervals. Significantly, the research established a correlation between crosslink density determined by DMA and the widely accepted solvent approach. This comprehensive study establishes the utilisation of the Dynamic Mechanical Analyser to study the crosslink density and enriches our understanding of rubber vulcanisates, providing valuable insights into the intricate relationship between crosslink density and mechanical properties across various vulcanisation systems.