可逆的未来

For millennia humankind has liberally used Earth’s natural resources. 正如当今世界的现状, 然而, it faces an enormous challenge to fundamentally change the ways things are done in response to the urgent need for a more sustainable global economy. Across various industries, science is paving a way to a vast array of such changes. 在OU, Marco Gerini-Romagnoli博士.D., 机械工程助理教授(ME), investigates de-bondable and reversible adhesives to facilitate part replacement, 修复, 和报废(EoL)回收.

对于许多制造业来说, the direction of essential changes is to make structural components lighter, 转向更少的组件, 并进行可拆卸设计, which will facilitate EoL and make positive moves towards a circular economy.

“力量, 刚度, and durability improvements as well as design flexibility considerations fuel adhesive bonding’s growing popularity in structural applications. 然而, bonded joints can hinder 修复 or EoL recycling activities for complex multi-material structures, or at least make the process very labor- and time-intensive. Parts can get damaged during disassembly, or it can be problematic to separate materials for EoL. 按需脱粘技术, 从理论上讲, 允许你克服这些限制, 但它们大部分仍处于开发阶段,博士解释道。. Gerini-Romagnoli, whose focus is on the implementation of reversible adhesive technologies for structural composite joints.

One of the ways to induce substrate separation is through additives that can weaken the adhesive layer upon activation. Utilizing the OU’s Fastening and Joining 研究 Institute site (FAJRI), one of the few academic research facilities in the world that is solely dedicated to material joining, 研究人员的合作小组, 还包括赛义德·纳萨尔, Ph.D. (ME)， Roman Dembinski，博士.D. (化学系). Gerini-Romagnoli的学生Khushboo Tedlapu, conducted a number of studies to advance de-bonding technologies.

In the initial experiment, the focus was on joints with at least one metallic substrate. Thermally Expandable Particles (TEPs) were added to a structural adhesive, Betamate 73326/73327M (a two-part epoxy) to achieve the reversibility of Single Lap Joints (SLJ). The team evaluated the impact of environmental aging on the static, 乏力, 以及slj的脱键性能. 具体地说, the parameters used to study the reversibility performance were the joint debonding time and the substrate temperature during debonding.

This study showed that the joint strength and the de-bonding action of the TEP additives were insensitive to environmental aging.

“Bond reversibility was possible for additive concentrations larger than 5% wt., and time and temperature to de-bond decreased with increasing particles content,” says Dr. Gerini-Romagnoli.

The team also worked on improving de-bonding performance with non-metallic joint substrates, 如纤维增强复合材料. Embedding ferromagnetic inserts in the bondline significantly decreased de-bonding time and temperature. 对刀片的设计进行了迭代优化, and the modified joints showed concurrent improvements in lap shear strength (up to 10% from baseline) and TEP activation time (up to two times shorter).

目前, the FAJRI group is in the beginning stages of working with vitrimers - a new class of polymers that can de-crosslink. 在所有传统的热固性结构胶中, long polymeric chains are crosslinked during the curing process, 创建一个强大的三维网络. Cross-linking gives thermoset adhesives their strength and increases their Glass Transition Temperature, 经常把它们从糊状变成固体. 然而, the cross-linking bonds in thermoset polymers are not reversible.

“Epoxy-based vitrimers represent a promising option toward sustainability and circular economy in many structural applications. 它们来源于热固性聚合物, but what sets them apart is their reversible covalent bonds. 实际上, 这意味着基于玻璃体的粘合剂可以被重塑, 改革, de-bonded, 和重用, 为回收和修复开辟了令人兴奋的可能性, 特别是在防御方面, 基础设施, 汽车, 航空航天工业,Khushboo Tedlapu说, 谁在攻读机械工程硕士学位.

“There have been a couple of early studies published this year on using vitrimers as adhesives, 所以我们不是第一个, 但它仍然是一项处于起步阶段的技术. The expectation is that once we will optimize formulation and application, 我们将能够重新粘合脱落的关节,博士补充道。. Gerini-Romagnoli.

博士的另一个方面. Gerini-Romagnoli’s research is Non-Destructive Inspection (NDI) of composite adhesive joints, 与杨连祥一起指挥, Ph.D.他是机械工程特聘教授. Due to the inherent material discontinuities in the matrix of composite materials, 粘合接头的NDI具有挑战性. The scientists are investigating synergistic integration of optical techniques with mechanical modeling to detect void-type defects in the adhesive layer.

Regardless of the joining method, material interfaces are complex and vulnerable regions. Developing a reversible adhesive that can de-bond on-command is an important step in aiding 修复 and recyclability. Dr. 吉莉香的物质加入研究, 其中还包括螺栓连接, is supported by the NSF IUCRC (Industry-University Cooperative 研究 Center) for Composite and Hybrid Materials Interfacing (CHMI), 他在那里担任公开网站管理员. 更多信息，请发送电子邮件 (电子邮件保护).