摘要：

Crack growth resistance of rubber compounds is of vital importance for tire applications such as the safety of vehicle drivers and the life-time of tires. Two parts of related work will be presented to address the key issue. The first is how to monitor the cracking process, and the second is how to improve the crack resistance of tire materials with a simple processing strategy.
　　Under cyclic deformation, it is reported that rubbers of rich cracking morphology dissipate more energy and have low crack growth rate (dc/dn) . In this study, real time morphology monitoring at the crack tips of elastomers is achieved by the use of high-resolution high-speed camera and dynamic mechanical analyzer with crack growth testing function.
　　It is found that natural rubber (NR)’s cracking process has two regimes, and each has distinct dynamic morphology of the cracking tip. Interestingly, the two distinct dynamic morphologies correlated very well with the two distinct slops of the log-log plot of dc/dn and tear energy (T).  This behavior of two regimes with a transition point is so far only exists for NR. The styrene-butadiene rubber(SBR) and polybutadiene(BR) have only one kind of cracking morphology and one slop at the current testing range of the instrumentation. These dynamic “ligament” morphology during crack growth is resulted from the breakup of the ligament-like shape at the cracking tip. Meanwhile, the characteristic dimensions of all the cracking morphologies are proportional to the tear energy. When filled with carbon black, the crack growth rate is significantly reduced, and the transition point between two regimes of NR is shifted to higher tear energy; while the ligament dimensions of SBR and BR become smaller and more uniform. Results may suggest that the characteristic cracking tip morphology of NR is somewhat related to the strain induced crystallization. The effect of carbon black on ligament dimension of SBR and BR rubbers may be related to the alteration of stress-distribution and surface instability as a result of filler dispersion in the polymer bulk.
　　Block copolymer has been extensively used to reduce the domain size of immiscible polymers in order to improve the mechanical properties. To make sure that these polymeric surfactant molecules are actually stays at the interface of the polymer blends, many efforts have been focused on the design of molecular architecture and synthesis of block copolymers. With a very simple mixing strategy, a small amount of low molecular weight liquid diblock copolymer rubber has reduced the domain size of NR/BR, thus improves the cracking resistance, by making each and every diblock molecules stays at the interface of NR and BR. Amazingly, the crack resistance, the other mechanical properties, as well as processing characteristics are all improved.

Keywords: crack propagation, real-time monitoring, blending, compounding, morphology evolution, polydiene, natural rubber, liquid rubber, styrene-butadiene rubber
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 个人简介：

陈忠仁，博士，教授，宁波大学材料科学与化学工程学院院长、国家“千人计划”入选者（全职、创新类）、中国国家特聘专家。1984年浙江大学高分子化工学士，1987年浙大化学工程硕士，1998年美国加州理工学院化学工程和化学博士；1998-2000斯坦福大学和Honeywell博士后；2000-2011普利斯通（Bridgestone）高级科研人员和核心管理团队成员。2011年全职加盟宁波大学。
陈忠仁教授长期从事以高性能橡胶为主的高分子材料领域的研究开发，已在相关领域取得系列重要基础研究与技术开发成果，如以第一作者在《Science》杂志以封面主题发表了相关原创性研究成果，已成为国际软材料领域纳米结构加工的标准方法；发展了软材料开裂磨损理论与仿生原理，成功主持了新一代高性能橡胶材料的工业合成及产业应用。
主要研究方向为：聚合物分子设计与可控聚合、高分子聚集态结构调控与表征、有机微纳米材料多尺度加工、高分子复合材料界面设计与调控、高分子疲劳失效机理与寿命预测。