Relationship between stress relaxation behavior and thermal stability of natural rubber vulcanizates

Abstract It is well-recognized that different sulphur curing systems have greatly influenced to the final properties of the rubber vulcanizates. In this study, the properties of vulcanizates with conventional vulcanization (CV) and efficiency vulcanization (EV) systems were correlated in the aspect of stress relaxation and thermal stability. The stress relaxation behaviour and thermal stability were studied with the temperature scanning stress relaxation (TSSR) and with thermogravimatric analysis (TGA) techniques, respectively. Thermo-oxidative degradation of rubber chains in the CV system was greater than the EV system, leading to easier stress relaxation and poorer aging resistance of the CV system. Also, thermal stability of the rubber crosslinked with CV system was poorer than that with the EV system as corroborated by the activation energy of degradation. TSSR result correlated well with TGA result, and both revealed type of crosslinkages governed the thermo-oxidative degradation and thermal stability of vulcanizates.

摘要 众所周知，不同的硫磺硫化体系对橡胶硫化胶的最终性能具有显著影响。本研究针对采用常规硫化体系（conventional vulcanization, CV）与有效硫化体系（efficiency vulcanization, EV）的硫化胶，从应力松弛与热稳定性维度开展性能关联分析。分别采用温度扫描应力松弛法（temperature scanning stress relaxation, TSSR）与热重分析法（thermogravimetric analysis, TGA）技术，对其应力松弛行为与热稳定性进行表征。研究发现，CV体系中橡胶分子链的热氧降解程度高于EV体系，进而导致CV体系的应力松弛更易发生，且耐老化性能更差。通过降解活化能的分析结果进一步证实，采用CV体系交联的橡胶其热稳定性亦劣于EV体系。TSSR测试结果与TGA分析结果具有良好的相关性，二者均表明：交联结构类型决定了硫化胶的热氧降解行为与热稳定性能。