|M.Sc Student||Dana Shamir|
|Subject||Electrically Conductive Filled Polymers for Vibration|
|Department||Department of Materials Science and Engineering||Supervisor||Professor Emeritus Siegmann Arnon (Deceased)|
|Full Thesis text|
Damping of vibrations in metal sheets can be achieved through the construction of metal sheet laminates, containing a core layer of viscoelastic material, exhibiting an energy loss at the desired temperature and frequency ranges. In certain applications the laminates are required to be electrically conductive.
The objectives of the project are to study selected polymers viscoelastic behavior, including energy loss intensity in temperature and frequency range; turning the selected polymers from electrically insulating to conductive materials, by using an electrically conducting filler; studying the structure property relationship of the conductive, vibration damping systems.
Three rubbery polymers including, styrene-ethylene butylene- styrene (SEBS) block copolymers, ethylene-methyl acrylate copolymer (E-MA) and styrene-butyl acrylate copolymer (St-BA) were selected for the study. Various amounts of electrically conductive carbon black (CB) were blended into the polymers.
St-BA copolymers exhibit damping capabilities in a wide temperature range by changing the monomers ratio. Adding CB reduces the peak damping intensity; however, enhances the damping at higher temperatures. Addition of dodecylbenzenesulfonic acid (DBSA) to the St-BA/CB aqueous dispersion improves the CB dispersion in the polymer, reducing the percolation threshold and improving the conductivity, while slightly affecting the mechanical behavior.
The mechanical properties of the SEBS polymers are affected mainly by the presence of CB particles in the rubbery phase. The lower temperature peak damping intensity of SEBS is decreased, though the transition temperature is maintained. The triblock, phase separated morphology improved the conductivity and reduces the percolation threshold due to the "double percolation" phenomenon; percolation of the continuous phase and the conductive filler within it.
The damping intensity of a CB containing, peroxide crosslinked E-MA was studied. CB acts in this system as a physical crosslinker. The damping peak is significantly reduced upon the CB addition.