Waterborne Polyurethane Adhesive Modified By Nano-SiO₂and Fluorinated Acrylate

Laminated films have got rapid development in the field of flexible package due to theirbetter performance of fresh-keeping, photophobism, beautiful appearance and so on. Howeverthe adhesive used in the laminated films is an important factor that affect the packagingperformance. Currently, most of the laminating adhesives are waterborne polyurethaneadhesive. However the waterborne polyurethane (WPU) has disadvantages such as highsurface tension, poor heat resistance, low adhesive strength and so on which cannot meet therequirements for the soft package. Hence, WPU needs to be modified.In this paper, first, nano-SiO2was modified by3-amino propyltriethoxy silane (KH550).Then, nano-SiO2/waterborne polyurethan（eSiO2/WPU）hybrid dispersions were prepared withthe prepolymer of isophorone diisocyanate (IPDI), polybutylene adipate (PBA) and modifiednano-SiO2. Meanwhile, a series of nano-SiO2/fluorinated waterborne polyurethane(SiO2/FWPU) hybrid emulsions with core-shell particle structure were synthesized bySiO2/WPUL (SiO2/WPU was end-capped by hydroxyethyl methacrylate) emulsion andhexafluorobutyl methacrylate (HFMA) via seed emulsion polymerization process. Effects ofthe nano-SiO2content on the emulsion properties, film properties and phase morphology ofSiO2/WPU were investigated. And the influences of the nano-SiO2and HFBMA on theproperties of emulsion and film of SiO2/FWPU were studied. The wetting properties andadhesion strength of the SiO2/FWPU emulsion to the nonpolar polyolefin films weredescribed by the dynamic wetting model. The properties of SiO2/WPU and SiO2/FWPU werecharacterized by particle size analyzer, X-ray diffraction(XRD), thermogravimetric analysis(TGA), fourier transform infrared spectroscopy (FTIR), contact angle measurement,transmission electron microscopy (TEM), scanning electron microscopy(SEM), differentialscanning calorimetry (DSC), atomic force microscopy (AFM) and tensile test.The experimental results showed the higher content of nano-SiO2, the bigger particle size,lower zeta potential and worse stability of the SiO2/WPU. The incorporation of nano-SiO2improved the water resistance, mechanical properties and thermal stability of the SiO2/WPUfilm, decreased the degree of crystallization and phase separation and enhanced thecompatibility of soft and hard segment. SiO2/FWPU emulsions modified by nano-SiO2and HFMA owned obvious core-shell structure and low surface tension. The hydrophobicity,mechanical properties and thermal stability of the SiO2/FWPU film were increased with theincorporation of nano-SiO2and HFMA. The SiO2/FWPU emulsion exhibits excellentwettability and adhesive strength to the nonpolar films. The effects of wetting the diffusionabilities of adhesive emulsion to nonpolar polyolefin films on adhesive strength wereanalysied by diffusion theory and wetting theory. And the relationship between wetting andadhesive properties was revealed. The adhesion mechanism for adhesive to nonpolarpolyolefin films was analysed theoretically.