Research On The Preparation And Properties Of Nanoclay/Waterborne Polyurethane Nanocomposites

Waterborne polyurethane(WPU) has been widly used in coatings, adhesives, and inks, etc for its advantages such as low/zero VOC, non-flammable, good abrasion resistance and adhesion properties. However, WPU still has some defects such as poor water and solvent resistance, low mechanical property and thermal stability for its liner structure, low molecular weight and hydrophilic groups on its molecular chains, which restricts its industrial application. Therefore, WPU needs to be modified to overcome these defects. In this paper, we carried out the following research:First, chitosan was used as a coupling agent to modify the halloysite nanotubes, and then the modified halloysite nanotubes/waterborne polyurethane(CHTs/WPU) nanocomposites were prepared by incorporating chitosan-modified halloysite nanotubes(CHTs) into waterborne polyurethane matrix via in situ polymerization. FTIR, TGA, XRD and elemental analysis were used to analysis the degree of surface modification. And the effect of the content of CHTs loading on the thermal, mechanical and surface properties of CHTs/WPU was characterized by TGA, DSC, DMA and contact angle testing. The experimental results showed that with increasing the content of CHTs, the thermal properties of CHTs/WPU were enhanced, and the micro-phases separation between hard and soft segments was improved. In addition, the surface energy, tensile strength and elongation at break of CHTs/WPU were improved first and then decreased with the increase of CHTs content. The nanocomposites obtained the optimum performance when the CHTs content is 2 wt%.In order to synthesis a kind of WPU material with excellent thermal, mechanical and antibacterial properties, N-(2-aminoethyl)-3-aminopropyltrimethoxysilane and chitosan were used to modify halloysite nanotubes, and silver halloysite composite(Ag-HNT) was prepared by loading silver nanoparticles on the surface of modified halloysite nanotubes by reducing silver ion with NaBH4. Then, the silver-halloysite/waterborne polyurethane(WPU/Ag-HNT) nanocomposites were prepared by incorporating Ag-HNT particles into castor oil-based WPU matrix via in situ polymerization. TEM and XPS were used to verify that the silver nanoparticles were loaded successfully on the surface of HNTs. SEM, TGA, and DMA results showed that Ag-HNT particles were dispersed uniformly in WPU matrix, and strong interfacial interaction and hydrogen bonds were formed between Ag-HNT particles and polymer matrix, which improved the thermal and mechanical properties of WPU nanocomposites. Moreover, the antibacterial activity testing showed that the prepared WPU nanocomposites had excellent antibacterial activity to E.coli and S.aureus.In order to study the effects of morphology and surface structure of nanoclays on the mechanical, thermal and surface properties of WPU/clay nanocomposites, three kinds of γ-aminopropyltriethoxysilane(APTES)-modified nanoclays were incorporated into WPU matrix. FTIR, TGA, and EA were used to determine the degree of surface modification of nanoclays. The results showed that the nanoclay with layered structure and abundant hydroxyl groups on its surface could be modified easier. Furthermore, SEM and AFM were used to characterize the morphology of WPU/clay nanocomposites. And the effects of the nanoclays on the mechanical, thermal and surface properties of nancomposites were characterized by FTIR, TGA, DMA and contact angle tester. The results showed that the modified montmorillonite had best compatibility with polymer matrix, and its layered structure had high efficient on improving the thermal properties of WPU nanocomposites. The one dimensional attapulgite and halloysite also improved the thermal and mechanical properties of WPU nanocomposites, especially enhanced the tensile strength and elongation at break of nanocomposites simultaneously.