The Study On The Preparation,the Structure And The Properties Of Nylon 6/SiO₂ Nanocomposite

The tetraethoxysilane was hydrolyzed first, and then the hydrolysate and e -Caproamide was mixed, the mixture was heated till the gelate was formed, and then the gelate was polymerized. We obtained a good nylon 6/SiO2 nanocomposite by this way. The graph of SEM shows that the inorganic particles were smaller than 100 nm, most of them are 50 nm, the particles were dispersed very well in the nanocomposites and their diameters were very similar, we also study the mechanical propertiesm the compress properties, the dynamic mechanical properties, the nonisothermal crystallization behavior, the rheological properties, the water absorption properties and the antiwear properties. These results show that the properties of nanocomposite are more excellent than that of pure nylon 6.The study of the nonisothermal crystallization shows that there are two kinds of crystal; one is a crystal, the other is ycrystal; With the nano-silica increasing, the crystallization peak of nanocomposite was divided into double peaks. Jeziorney theory, the modified Avrami theory, was used to analyse the data of DSC, The nanocomposites' (1.4% silica) value of n and t1/2 is larger than that of pure nylon 6, The activation energies were evaluated by Kissinger method to be 199.54KJ/mol and 294.56KJ/mol for the nonisothermal crystallization of pure nylon 6 and nanocomposite respectively. The nano-silica increased the adhesion between the molecular chains of nylon 6 and nano-silica, the good adhesion impedes the motion of nylon 6 chains molecular chains, so the activation energy of nanocomposite increased greatly.The results of the dynamic mechanical properties showthat The Tg of pure nylon 6 is smaller than that of the nanocomposites (3.6% silica and 5.3% silica). When the nano-silica content is 9.3%, the Tg of nanocomposites' is similar to that of nylon 6. When the nano-silica content is 3. 6% and 5. 3%, the storage modulus E' are larger than that of nylon 6; when the nano-silica content is 9. 3% the storage modulus E' are similar to that of pure nylon 6; all these are caused by the good adhesion between the molecular chains of nylon 6 and the nano-silica.Result shows that mechanical properties were the highest when nano- silica was 3. 6%. Compared with pure nylon 6, the izod impact strength , tensile modulus, tensile strength, elongation at break increased 13%, 19%, 18%, and 35% respectively. With the nano-silica content increasing, the tensile mechanical properties, the impact properties and the shrinkage of the nanocomposites increased first, and then decreased; the compress strength, compress modulus and compress yield strength increased gradually.The study of the Rheological properties shows that they are false plastic fluid; at the same temperature, with the nano-silica content increasing, the apparent viscosity of the nanocomposites increased first, and then decreased; the non-Newton index of the nanocomposites are larger than that of pure nylon 6; With the nano-silica increasing, the melt activation energy increased first, and then decreased; with the nano-silica increasing, the hydrogen bond and the chemical bond increased, so the melt activation energy increased. When the nano-silica content is larger, the configuration becomes bad, the hydrogen bond and the chemical bond do not increased or increased little, so the melt activation energy decreased.The study of the water absorption properties, the antiwear properties shows, with the nano-silica increasing,the water absorption properties and the antiwear properties increased gradually. Firstly, the good adhesion between the nano-silica and the nylon 6 molecular chains make the water absorption properties and the antiwear properties increased. Secondly, the effect of filling make these properties increased. In my opinion, the latter is the more important factor.