Study On The Structure And Properies Of TPU/PA6 Blends And Their Filled Composites

Nylon6 (Polyamide6, PA6) has been widely used in industrial applications owing to its excellent properties. However, its sensitivity to notched impact at low temperature and poor resistance to wear under high pv condition limit its application. Thermoplastic Polyurethane(TPU) possesses excellent toughness, high wear resistance and good ductility with the similar chain structure to PA6. The blends of PA6 and TPU obtained by melt blending overcome the shortcomings of both and the properties of blends have been further improved in terms of composition by reinforcements and fillers so as to extend its application. Meanwhile, the structure, properties, toughening mechanism and wear resistance mechanism were investigated by DSC,WAXD,TGA,SEM, Universal Testing Machine and Abrasion Tester, respectively. The main results are summarized as follows.1. The results of DSC and WAXD showed the orientation of the molecule chain of PA6 was blocked to some extent with the addition of TPU. The amount of crystallinity and melting point of blends decreased, and H-bonds between the molecule chain of PA6 were not propitious to from along c axis corresponding to the decrease in the diffraction peak area ofα2. Glass Fiber(GF) and Sericite had nucleation effect on PA6 crystallization and increased its amount of crystallinity. Different from TPU/PA6, Glass Fiber(GF) and Sericite promote H-bonds between the molecule chain of PA6 fromed along c axis corresponding to the strength in the diffraction peak area ofα2.2. Brittle fracture was observed by SEM for pure PA6 of tensile fracture. The tensile strength for TPU/PA6 blends was 76% of that of pure PA6 when the proportion of TPU amounted to 8%,while the blends presented ductile facture after being stressed. Meanwhile, the notched impact strength of blends at low temperature(-20℃) was 3.75 times higher than that of pure PA6, SEM photos indicated that there was a fine dispersion between the two phases when the content of TPU below 8%, which suggested the two polymers were miscible then. Meanwhile, the toughness were strongly improved. The value of notched impact strength of composition, by adding Glass Fiber(GF) and Sericite to the blends, at low temperature(-20℃) was also 2-3 times larger than that of pure PA6.3. PA6 was worn out easily under high pv condition due to the absence of transfer film. The formation of transfer film for TPU/PA6 decreased the coefficient of friction and improved the wear resistance.The hardness of the composites was improved by adding GF,Sericite to TPU/PA6 blends, which contributed to the enhancement of pv limit.GF/TPU/PA6 composite showed improved mechanical and tribological properties.4. According to the SEM observation, abrasion wear and adhesion wear dominated the wear mechanism under the condition of low high pv. Under the condition of high pv, the main wear mechanisms for TPU/PA6 were adhesion wear, fatigue wear and oxidizing wear, while that for GF/TPU/PA6 composite were abrasion wear and fatigue wear and adhesion wear prevailed in the friction stage for Sericite/TPU/PA6. It can be concluded that the shape of reinforcements and fillers affected the tribological properties and mechanisms of composites.5. WAXD revealedαphase dominated PA6 and its blends, butγphase appeared after dry friction subjected to heat and shear.