Controlling coefficients of thermal expansion in thermoplastic materials: effects of zinc cyanide and ionic liquid

Abstract

Tuning the coefficients of thermal expansion (CTE) of materials is necessary to control performance and extend the operational life of precision equipment. Herein, we report the strategy of creating 3-component composite materials from the thermoplastic poly(ethylene), zinc cyanide as a solid with a negative coefficient of thermal expansion (NTE), and ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([EMIM][TFSI]) as an interfacial agent that enhances the polymer/solid interface. Specifically, we produce thermoplastic composites with coefficients of thermal expansion reduced from 290 to 190 × 10⁻⁶ K⁻¹, a significantly larger reduction than the ca. −15 × 10⁻⁶ K⁻¹ reported for composites containing other NTE fillers. Additionally, the composite materials retain a Young's modulus comparable to low density polyethylene (80–110 MPa). Overall, this three-component design strategy shows promise for the development of thermoplastic materials with controlled coefficients of thermal expansion.