The Preparation And Spining Application Of PA66/SiO₂ Nanomaterials

Nylon 66 is one of the most widely used polymer materials as the tire cord which has high strength, good adhesion with rubber and other advantages. But now with the requirements of the automotive industry for tire performance becoming higher, the low modulus and thermal dimensional stability limit its application. This work aims to improve the modulus and dimensional stability of nylon 66 by the nano-composite modification technology. Using the in-situ polymerization method to ensure the good dispersion of nano-fillers, and the condensation product were processed by the solid phase polycondensation in order to achieve the spinning molecular weight requirements. The main results are as follows:(1) PA66/Si O2 nanocomposites was prepared by in situ polymerization,the molecular weight is about 13000. Molecular weight of the product was very stable and the dispersion of nanoparticles was good. DSC results showed that nano-Si O2 played a good role in nucleating agent, which significantly improved the crystallinity and crystallization rate. At last, the mechanical properties of PA66 composites improved.(2)The molecular weight of PA66 increased from about 1.30×104 to about 2.10×104 by solid phase polycondensation method which reached the spinning requirements. The reaction conditions were temperature 175 ℃, time 3h, nitrogen flow rate 40 L / h. Increasing solid-phase condensation temperature and reaction time, using high initial molecular weight slice can improve the molecular weight of the solid phase polycondensation product.(3)The non-isothermal crystallization behavior of PA66 and PA66/Si O2 before and after solid phase polycondensation were investigated by Jeziorny analysis, Ozawa analysis and Mo’s analysis, respectively. The results showed that nucleation was heterogeneous nucleation and homogeneous nucleation, existence of two-dimensional and three-dimensional crystal growth pattern growth. The Ozawa analysis seemed not suit when the value of Xc(T) at different cooling rates was large difference, while Mo’s analysis was sueeessfully used.(4) The dynamic mechanical properties of PA66 and PA66/Si O2 nanocomposites was investigated. It was found that Si O2 could improve the dynamic mechanical properties of nanocomposites. While the changes of molecular weight had little impact on dynamic mechanical properties and tensile performance. Found that adding 0.8wt% of Si O2 can make the material thermal expansion coefficient reduced by 24%.(5) The impact of nano-Si O2 and molecular weight on the rheological properties was studied. It was found that the adding of Si O2 could improve the melt viscosity, make the material achieve the requirement of the spinning at low molecular weight. So nano-Si O2 made the material more suitable for the preparation of high modulus and low shrinkage chinlon 66, and it is conducive to saving the cost of production.(6) Spinning and scale-up experiment was investigated. It was found that the hexamethylene diamine adipic acid mixed solution could be used as raw material to obtained higher molecular weight product when the p H was 7.7. The PA66/Si O2 composite fiber had more smooth surface and uniform thickness comparing with the PA66 fiber. This phenomenon proved that PA66/Si O2 nanomaterials prepared by in-situ polymerization was suitable for spinning.