Surface Modification Of Attapulgite And The Application In Nylon 6

Attapulgites are especially attractive candidate for the reinforcement modifier of polymers owing to their characteristics such as a high aspect ratio, nanofibrillar structure and the poor interaction between rod shape crystals. In the dissertation, naturally attapulgite nanofibers were purified and then modified by grafting polymer. The modified particles were used as a new type reinforcement for nylon 6 and the resulted attapulgite/nylon 6 nanocomposites possessed promising mechanical performance. The preparation, structure and properties of attapulgite/nylon 6 nanocomposites were investigated fully. The main contents are as follows:The attapulgite/nylon 6 nanocomposites were prepared by traditional extrusion and injection processes. The results showed that the composites possess better dispersion of the filler and better mechanical properties. The addition of attapulgite into nylon 6 did not change its crystalline form, but increased the crystallization temperature and promoted the heterogeneous nucleation of nylon 6. On the other hand, The crystallization sizes of attapulgite/nylon 6 nanocomposites were reduced, and the crystallization activation energies of composites were increased.Modification was performed by grafting polyurethane prepolymer via condensation polymerization on the surfaces of attapulgite. The results demonstrated that the grafting molecule chains were combined with the hydroxyl groups on attapulgite surfaces via chemical bonds. The grafting polymers were mainly distributed on the surfaces instead of bulk. The diameters of attapulgite were enlarged obviously. The color was dark in the center while it was light around. The grafted particles presented a definite core-shell structure. Attapulgite was coated with polyurethane latex with aluminium potassium sulfate dodecahydrate as demulsifying agent in the form of a core-shell structure. Attapulgite could be coated singly while the weight ratio of polyurethane latex to attapulgite was 3:1. The coating was about 10 nm thick, and the mass content of polyurethane was 9%.Investigation on polyurethane modified attapulgite/nylong 6 composites indicated the surface modification had significant effect on the improvement of the dispersion of filler in the polymer matrices. The interfaces between modified attapulgite and nylon 6 were blurred, which demonstrsted the modified particles had good compatibility with the matrices and there were strong interface effects between the two phases. The mechanical performance and especially impact strength of composites were improved since the modification chains cross-linked and twisted with the nylon 6 chains, and flexible interface layers thus formed. For instance, incorporating 10% polyurethane coated attapulgite into nylony 6 leaded to 34.7% increase in tensile strength and 85.7% increase in impact strength. The tensile fracture surfaces of composites had a distinct character of yielding fracture, and the impact surfaces of composites were much rougher with the increasing of modified attapulgite. The storage modulus and Tg of composites were improved as the addition of polyurethane coated attapulgite. The polyurethane coated attapulgite/nylon 6 composites could be seen as the non-Newtonian fluids, and the non-Newtonianism of composites were reduced with the increasing of polyurethane coated attapulgite.Maleic anhydride-grafted polypropylene(POE-g-MAH) were grafted on the surfaces of attapulgite by two steps method. Modified attapulgite nanoparticles were characterized using Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), transmission electron X-ray diffraction (XRD), and thermogravimetric analysis (TG). The results showed that POE chains were combined with the hydroxyl groups on attapulgite surfaces via chemical bonds, and the mass content of POE was 9.5%. The surface modification of attapulgite was attempted to increase the dispersion of attapulgite and the impact strength of the composites.