Science and Technology of Ultrasonic Devulcanization of Rubbers

本研究项目的主要目的是为不同类型的增强和非增强硫化弹性体的连续硫化新技术开发基础知识和设计高容量设备。通过在特殊装置中应用一定水平的超声波振幅，可以在一秒甚至更短的时间内击穿三维网络。作为最理想的结果，超声处理的橡胶变得柔软，从而使该材料能够再加工，成型和再硫化。在一定的加工条件下，再硫化橡胶的抗拉强度比原硫化橡胶高得多。本研究概述了一系列的实验：(1)确定硫化橡胶的化学结构对脱硫过程的影响；(2)评价填料种类和用量对脱硫过程的影响；(3)研究了主链键能与交联键和橡胶填充键键的键能之比对三维橡胶网络断裂的影响；(4)建立最优的脱硫和再硫化工艺条件，使再生橡胶具有较好的力学性能；(5)设计硫化弹性体连续脱硫新设备；(6)建立了既考虑空化崩溃过程又考虑稳定脉动空腔附近动态疲劳导致的网络退化的超声脱硫理论。由于动态疲劳过程是特定于聚合物化学结构和橡胶网络拓扑结构的，因此该理论可以预测不同类型交联橡胶的超声波脱硫的最佳条件。这项新技术的开发和应用将对回收技术的进一步扩展产生重大影响，该技术可回收所有工业上重要的橡胶种类，包括轮胎橡胶。超声脱硫化过程的理论模型的发展，使人们能够预测回收的最佳条件，将有助于设计一种方法来控制再生橡胶产品的性能。这项以科学为基础的新技术可以彻底改变橡胶的回收方式。

The main objective of this research project is to develop basic knowledge and to design high capacity equipment for the new technology of continuous devulcanization of different kinds of reinforced and nonreinforced vulcanized elastomers. Through the application of certain levels of ultrasonic amplitudes in special devices, the three-dimensional network can be broken down within a short period of time of the order of a second or even less. As the most desirable consequence, ultrasonically treated rubber becomes soft thereby enabling this material to be reprocessed, shaped, and revulcanized. Under certain processing conditions, the tensile strength of revulcanized rubber is much higher than that of original vulcanizates. This study outlines a series of experiments to (1) identify the effect of the chemical structure of vulcanized rubber on the devulcanization process; (2) evaluate the effect of the type and amount of filler on the devulcanization process; (3) investigate the effect of the ratio of bond energy of the main chain and that of crosslinks and rubber-filler bonds on the break up of the three dimensional rubber network; (4) establish optimal conditions for the devulcanization and revulcanization process enabling one to obtain reclaimed rubbers with better mechanical properties; (5) design new equipment for continuous devulcanization of vulcanized elastomers; and, (6) develop the theory of ultrasonic devulcanization based not only on the process of cavitation collapse but also accounting for the network degradation owing to dynamic fatigue in the vicinity of stable pulsating cavities. Since the dynamic fatigue processes are specific to polymer chemical structure as well as to rubber network topology, the theory may be able to predict optimal conditions of ultrasonic devulcanization for different types of crosslinked rubbers. The development and application of this novel technique for reclaiming all industrially important types of rubber, including tire rubber, will have a signific ant impact on the further expansion of recycling technology. Development of a theoretical model of the process of ultrasonic devulcanization, allowing one to predict optimal conditions of recycling, will help to devise a methodology to control the properties of reclaimed rubber products. The new science-based technology can revolutionize the way rubber is recycled.