Blend composites of caprolactam-modified casein and waterborne polyurethane for film-forming binder: Miscibility, morphology and properties

Biodegradable composites of caprolactam-modified casein and waterborne polyurethane (CA-CPL/WPU) for film-forming binder were prepared in composition of 5:5, 6:4, 7:3, 8:2, 9:1 (w/w) via blending. Influences of WPU amount on miscibility, morphology and properties of the composites were investigated. Flourier transform infrared (FT-IR), transmission electron microscopy (TEM) and dynamic laser scattering (DLS) verified that hydrogen bonding interaction existed at the interfaces of CA-CPL and WPU, which had great influence on particle morphology and miscibility. Film properties were studied by scanning electron microscopy (SEM) and contact angle analysis, confirming the reduced pores but enhanced hydrophobicity of CA-CPL/WPU when compared to those of control system. CA-CPL/WPU was applied as the film-forming binder in leather finishing, performances of leather samples improved with an increase in elongation at break from 72.46% to 99.77% and wet rub resistance fastness from 3 to 4-5.However, air permeability reduced from 223.46 to 117.04 (mL/(cm2∙h)).