Interfacial Structure And Properties Of Aliphatic Polyester Composites With Nylon 6 Fibers

Aliphatic polyesters such as poly(butylene adipate)(PBA),poly(butylene succinate)(PBS)and poly(ε-caprolactone)(PCL)can be used as a raw material for synthetic polyurethane.The interfacial structure has a great effect on the properties of the polymer/fiber composites.By adjusting the crystallization temperature,the content or type of the filler and preparation methods,the interfacial structure as well as the properties of polymer materials can be exactly controlled.In this paper,the polyester/fiber composites were prepared by introduing nylon 6 fibers into PBA,PBS and PCL,respectively.The structure and properties of the composites were measured by differential scanning calorimetry(DSC),polarizing microscope(POM),scanning electron microscopy(SEM)and Raman microscope.The effects of nylon 6 fibers on the interfacial structure and structural growth mechanism in these composites were discussed.(1)The non-isothermal and isothermal crystallization kinetic results showed that the crystal structure of neat PBA was influenced by the crystallization temperature as well as cooling rate.The β-form PBA crystals grew at the temperatures below 27 oC or cooling rate above 15 oC/min,while the α-form crystals were formed at the temperatures above 33 oC or cooling rate below 2 oC/min.The nylon-6 fibers exhibited strong nucleation ability toward PBA as demonstrated by the formation of α-form trancrystalline layers.The effect of nylon-6 on the α-PBA crystallization was confirmed to be limited within a range of ca.1 ?m.Furthermore,it was also found that there exist good lattice matching and strong intermolecular action between the α-form PBA and nylon-6 fiber.(2)In PBS/nylon-6 fiber composites,the nylon-6 fibers showed heterogeneous nucleation to PBS and the nucleation density of PBS on nylon 6 fibers decreased with the crystallization temperature.In addition,the crystallization temperature of PBS increased with the content of nylon-6 short fibers.However,the crystal structure of PBS would not change with the increment of nylon-6 fibers.By analyzing the crossing section of the PBS/nylon-6 fiber composites,it was found that nylon 6 fiber has low interfacial bonding strength with PBS.(3)When PCL was crystallized on the surface of nylon-6 fiber,the high nucleation density led to the growth of PCL lamellae in the direction perpendicular to the fiber axis of nylon-6 fiber.The growth rate of PCL lamellae increased with decreasing the crystallization temperature.Based on the Lauritzen-Hoffman equation,the dynamic growth process of PCL transcrystalline layer as well as nucleation constant Kg was analyzed and calculated.Additionally,the mechanical properties results showed that the nylon-6 fiber reinforced PCL composites have excellent tensile strength.