Research On The Preparation And Water Absorption Properties Of Nylon-66Modified By PTT And PF

Polyamide66(PA66) is mainly used in the fields of synthetic fibers and engineering plastics,which has excellent mechanical properties, corrosion resistance, wear resistance, self lubricity and soon. However, PA66also has some disadvantages such as the high water absorption and the poordimensional stability. In this article, three different methods were used to reduce the water absorptionof PA66.Firstly, PA66was blended with PTT to form an alloy to reduce water absorption, andPOE-g-MAH as a compatibilizer was added to PTT/PA66alloys. The results showed that the additionof PTT could decrease the water absorption of PA66. When20%PTT was added, the24h andequilibrium water absorption respectively decreased by44.1%,40.4%compared with pure PA66.POE-g-MAH was an effective compatibilizer of PTT/PA66alloys. The SEM analysis show that whenthe conent of POE-g-MAH was3phr, the particle size of dispersed phase PTT decreased from3.98μmto0.69μm. The composites had a good comprehensive performance when the ratio ofPA66/PTT/POE-g-MAH was80:20:3. In this case, the equilibrium water absorption declined by40.4%compared with pure PA66, the tensile and flexural strength decreased by17.3%,20.4%, but the impactstrength increased by13.3%.Secondly, the water absorption of PA66was decreased by adding PF, and a kind of nano-SiO2wasadded into PF/PA66to enhance its mechanical properties. The results showed that the24h andequilibrium water absorption of PA66were respectively decreased by51.92%,57.74%when10%PFwas added. The IR analysis showed that the surface of nano-SiO2modified with KH560had thecharacteristic group of KH560; the TEM showed that the modified SiO2by KH560was dispersedevenly with a diameter of50nm. With the increase of SiO2content, the tensile and flexural strength ofcomposites showed the tendency of fist increased and then decreased with the addition of nano-SiO2,and the impact strength showed a wave shaped trend. The composites had a good comprehensiveperformance when the ratio of PA66/PF/nano-SiO2was90:10:4. In this case, the24h and equilibriumwater absorption declined by52%,59.8%compared with pure PA66, the tensile and flexural strengthdecreased by8.7%,14.2%, but the impact strength increased only3.3%.Finally, surface treatment methods were used to decrease the water absorption of PA66. SEManalysis showed that the surface of PA66had micro-and nano-scale roughened structure of linesclusters combination evenly distributed by phosphoric acid treatment, and there are plenty of interspaces between the clusters. The surface of PA66formed a hydrophobic film by SiO2coating, andhad the raised structure of single nano level. The surface of PA66by K2Cr2O7/concentrated H2SO4showed lamellar structure of micron and mesh pit structure of nano-level, and a lot of interspacesexsited on the surface of PA66. The roughened surface was modified through hydrophobic modificationwith low surface energy materials. The static contact angle of PA66was124.8,115.8and124respectively after treatment by the three methods. The24h water absorption was0.241%,0.278%and0.25%respectively. The surface of PA66showed the certain hydrophobicity by three kinds of surfacetreatment methods.In the above three methods, the water absorption of PA66could be decreased effectively byadding PF and treatments of phosphoric acid, K2Cr2O7/concentrated H2SO4. Above all, these methodshave little effect on the mechanical properties of PA66.