Effect of Time, Temperature, and Ionic Content on Interfacial Healing in EMAA

Self-healing materials are a new and novel way to deal with damage caused through wear and use of objects. Currently there are a number of different types of self-healing materials being researched throughout the world. Most of these materials are complex composites that consist of tubes or bubbles contained in a polymer matrix. These tubes and bubbles hold a healing agent which is released as the composite is damaged and the tubes and bubbles break. These materials work well but are very expensive and are fairly difficult to produce. Another type of material being researched heals in an unmodified form through its thermoelastic properties. This material, poly(ethylene-co-methacrylic acid) (EMAA), has been in commercial production for many years but research into its healing capabilities is fairly new. EMAA is a copolymer that contains acid groups which can be neutralized to form ionic species and change the copolymer into an ionomer. It has been theorized and observed that the ionic content of these materials affects the healing capabilities and healing quality of the samples but very few studies have been done on them. A more in-depth knowledge of how chemical structure affects healing capabilities will allow for new designs to be created. The most interesting healing ability possessed by EMAA is its ability to heal after suffering ballistic impact. Healing after ballistic impact consists of three parts. The first is the energy transfer from the projectile to the EMAA, the second part is the closing of the hole created by the projectile, and the final part is the sealing of the now closed hole. The second and third parts of the healing rely on the temperature rise from the first part. To date, no reported testing has been done on how ionic content affects the temperature rise due to deformation or how ionic content affects the materials ability to seal the hole after it has closed. This project will look at the second of these aspects of ballistic healing