07/17/2025
By Danielle Fretwell
Candidate Name: Nathalia Diaz Armas
Degree: Doctoral
Defense Date: Thursday, July 31, 2025
Time: 10 a.m. - Noon
Location: Emerging Technologies and Innovation Center (ETIC), Room 345
Committee:
Advisor: Joey Mead, Ph.D., University Professor, Plastics Engineering Department, UMass Lowell
Committee Members*
1. David Kazmer, Ph.D., Professor, Plastics Engineering Department, UMass Lowell
2. Alireza Amirkhizi, Ph.D., Associate Professor, Mechanical and Industrial Engineering Department, UMass Lowell
3. Jinde Zhang, Ph.D., Assistant Research Professor, Plastics Engineering Department, UMass Lowell
Abstract:
Elastomeric materials have the unique capability to undergo large deformations under stress and return to their original shape once the stress is removed. In particular, thermoset elastomers are especially valuable due to their capacity to create permanent crosslinked networks, which provide superior mechanical stability, chemical resistance, and long-term durability. This dissertation investigates how these materials can be integrated into emerging manufacturing processes and applications, utilizing their distinct properties to enable new functionalities in areas such as additive manufacturing and soft robotics.
This thesis is divided into three chapters. The first Chapter investigates the additive manufacturing of fully compounded thermoset elastomers that contain fillers in combination with rigid thermoplastics using a custom-designed printer. This presents significant challenges due to the contrasting processing conditions required by each material. However, such combinations are crucial for applications involving high temperatures or harsh chemical environments, where thermoplastic elastomers (TPEs) may fall short compared to thermoset elastomers. The chapter presents results on the bond strength between selected thermoset elastomers and thermoplastic combinations, as well as the influence of key process parameters on adhesion.
In Chapter 2, the feasibility of using microwave radiation as an in-situ curing method for the additive manufacturing of fully compounded thermoset elastomers is explored. This approach aims to adapt industrial microwave vulcanization to a localized format suitable for additive manufacturing, eliminating the need for a secondary curing step, while enhancing process control and part quality. The curing behavior of sulfur-cured nitrile rubber (NBR) formulations with varying carbon black content was studied using a custom-designed post-print microwave setup. The effects of microwave power, exposure time, and carbon black content on the degree of cure was explored.
Finally, Chapter Three introduces a novel manufacturing process that uses elastomeric braided composites to create a pneumatic soft robotic actuator designed to provide haptic feedback for teleoperation. Braided structures embedded within a silicone rubber matrix were utilized to customize mechanical performance, while maintaining flexibility, foldability, and air impermeability. By adjusting the braiding angle, multiple actuators were fabricated and tested for their mechanical properties and effectiveness in transmitting tactile feedback to the user’s fingers.
Thermoset rubbers have traditionally been utilized in well-established applications such as tires, seals, footwear, and medical devices; conventional uses that emphasize their durability and performance. This dissertation advances the use of these materials by integrating them into emerging technologies, pushing the boundaries of traditional manufacturing and adapting their capabilities to fulfill modern engineering demands.