Preparation, characterization and application of dispersible and spherical Nano-SiO2@Copolymer nanocomposite in leather tanning

Dispersible and spherical silica nanoparticles (nano-SiO2) were prepared with tetraethyl silicate and different surface-modifiers via a simple method. The silica nanoparticles surface-modified with methacryloxy (propyl) trimethoxysilane (denoted as MPS-SiO2), dimethyl diallyl ammoniumchloride (denoted as DMDAAC-SiO2) and poly (methacrylic acid) (denoted as PMAA-SiO2) which are known as hydrophobic, amphiphilic and hydrophilic modifiers, respectively, exhibited excellent dispersibility in various solvents or polymer matrix. The obtained bare silica nanoparticles, MPS-SiO2, DMDAAC-SiO2 and PMAA-SiO2 were characterized by Fourier transform infrared spectra (FTIR), thermogravimetric analysis (TGA), transmission electron microscope (TEM) and scanning electron microscope (SEM). A series of nanocomposites (denoted as SiO2/P, MPS-SiO2/P, DMDAAC-SiO2/P and PMAA-SiO2/P, respectively) were also prepared with the bare or surface-modified silica nanoparticles and methacrylic acid-co-acrylamide-co-acrylonitrile-co-salicylic acid tetrabasic copolymer (denoted as PMAAS) and applied in leather tanning. Compared with those of the leather tanned with the commercial acrylic resin (CHINATAN OM) and pure tetrabasic copolymer tanning agents, the physical and mechanical properties, rheological properties and thermal stabilities of the leather treated with SiO2/P, MPS-SiO2/P, DMDAAC-SiO2/P or PMAA-SiO2/P founded to be improved in a significant way. Moreover, the highest shrinkage temperature of the wet-white sheepskin tanned with PMAA-SiO2/P reached to 76 °C and the thickness increase reached to 105%.