Preparation of dendritic waterborne polyurethane-urea/Ni–Zn ferrite composite coatings and investigation of their microwave absorption properties

Abstract

This study shows the preparation of microwave absorbing composite material by using Ni–Zn ferrite filler and dendritic waterborne polyurethane-urea (WPU) polymer as a matrix. Initially, waterborne polyurethane prepolymers were synthesized by using PEG1500 (WPU1) and PPG1000 (WPU2) polyols via prepolymer mixing process. Then, chain extended with water in the presence of hexamethylenetetramine (HMTA) as crosslinker. Then, 1/1 (w/w) amount of Ni–Zn ferrite was dispersed in the WPU polymer to be converted into a microwave absorbing composite coating (CWPU1 and CWPU2). Structural, mechanical and morphological properties were investigated. The microwave absorption measurements were performed by using transmission/reflection method via waveguide method in the frequency range of 8.2–12.4GHz. Permittivity and permeability measurements were performed in the frequency range of 8.2–12.4GHz. It has been found that CWPU1 which was prepared by using WPU1 polymer indicated broader microwave absorption between 9.4 and 11.7GHz due to its dendritic structure. Besides, permittivity and permeability results indicated that CWPU1 and CWPU2 have distinctive magnetic properties.