Electromechanical instabilities of thermoplastics: Theory and in situ observation

Abstract

Thermoplastics under voltages are used in diverse applications ranging from insulating cables to organic capacitors. Electromechanical instabilities have been proposed as a mechanism that causes electrical breakdown of thermoplastics. However, existing experiments cannot provide direct observations of the instability process, and existing theories for the instabilities generally assume thermoplastics are mechanically unconstrained. Here, we report in situ observations of electromechanical instabilities in various thermoplastics. A theory is formulated for electromechanical instabilities of thermoplastics under different mechanical constraints. We find that the instabilities generally occur in thermoplastics when temperature is above their glass transition temperatures and electric field reaches a critical value. The critical electric field for the instabilities scales with square root of yield stress of the thermoplastic and depends on its Young's modulus and hardening property.

Creasing-wrinkling transition in elastomer films under electric fields

“…The electric-fieldinduced creasing and wrinkling instabilities have been widely implicated in detrimental failures of insulating cables [9,10], organic capacitors [11], and dielectric-elastomer actuators [2,12] and energy harvesters [13]. Conversely, controlling these instabilities with electric fields has led to beneficial applications as diverse as functional surfaces and interfaces [3,4], biomedical devices [14], and on-demand patterning [15].…”

Smoothening creases on surfaces of strain-stiffening materials

“…Creases, however, have been observed routinely on elastic blocks compressed by various means, including mechanical forces Gent and Cho, 1999;Ghatak and Das, 2007;Mora et al, 2011), constrained swelling (Arifuzzaman et al, 2012;Barros et al, 2012;Dervaux and Ben Amar, 2012;Dervaux et al, 2011;Guvendiren et al, 2010;Ortiz et al, 2010;Pandey and Holmes, 2013;Tanaka, 1986;Tanaka et al, 1987;Trujillo et al, 2008;Weiss et al, 2013;Zalachas et al, 2013), temperature change , electric fields (Park et al, 2013;Wang et al, 2012;Wang et al, 2011;Wang and Zhao, 2013a;Xu and Hayward, 2013), and light (Yoon et al, 2012). Creases have been studied in soft tissues (Bayly et al, 2014;Jin et al, 2011;Yang et al, 2007).…”

In-plane electrical bistability of photochromic diarylethene/Cu composite film

“…The origin of the shift of V th based on photoisomerization reaction can be attributed to a change of Tg based on photoisomerization; low-Tg organic materials show low breakdown voltages. The insulation breakdown is originated in hole-generation by accumulation of the free volume by the molecular motion in low-Tg amorphous phase and in their electronic acceleration [24][25] [26]. For the DAE amorphous film, Tg changes from 32°C for the colorless state to 95°C for the colored state [23].…”