Preparation And Properties Research Of PLLA/TPEE Blends And Its Nanocomposites

In this thesis, Maleic anhydride (MAH) grafted thermoplastic polyester elastomer(TPEE) was firstly prepared using dicumyl peroxide(DCP) as initiator in the twin-screw extruder and characterized by Fourier transform infrared spectroscopy (FTIR). The results showed that MAH could be grafted onto TPEE macromolecular chains by using reactive extrusion methods. Moreover, The grafting degree of MAH on TPEE was determined by acid-base titration. The effects of extrusion process conditions, the amount of initiator and MAH on grafting degree and melt flow rate of TPEE-g-MAH were studied. The results showed that the optimal conditions were:DCP0.35%, MAH2%, the extrusion temperature190℃, the rotation speed of twin-screw100r/min.PLLA/TPEE-g-MAH alloy materials were prepared by twin-screw melt techno logy. The thermal properties, crystallization behavior, crystalline morphology, fracture surface and rheological properties were studied by universal testing machine, impact testing machine, thermal gravimetric analysis (TGA), differential scanning calorimeter (DSC), dynamic mechanical analyzer (DMA), polarized light microscopy (POM) and field emission scanning electron microscope (SEM), respectively. The results showed that the strength and modulus of the composite decreased with the increasing content of TPEE-g-MAH. The elongation at break and notched impact strength first increased then decreased with the increasing content of TPEE-g-MAH. The thermal stability, the glass transition temperature, crystallization rate and degree of crystallinity of the alloy materials decreases with addition of TPEE-g-MAH, respectively. POM tests showed that PLLA/TPEE-g-MAH materials still show a typical spherulitic morphology, and the spherulite size of PLLA in blends is larger than pure PLLA. PLLA spherulite growth rate in blends increases with temperature increases. The phase interface became blurred with TPEE-g-MAH content increases from the SEM photos. It has proved that the role of the interface strengthened. PLLA/TPEE-g-MAH alloy displays pseudoplastic fluid properties in reological analysis. With addition of TPEE-g-MAH, the melt viscosity of the alloy reduces, so the processing performance of PLLA/TPEE-g-MAH composites have improved.The isothermal crystallization kinetics of PLLA/TPEE-g-MAH composites were studied by DSC.The results showed that the composite materials were in line with isothermal crystallization kinetics Avrami equation mainly.The crystallization process of PLLA molecular chain and the crystallization rate reduced with the addition of TPEE-g-MAH, and the rate of crystallization increased with the crystallization temperature decreased.PLLA/TPEE-g-MAH/nano-Al2O3ternary composites were prepared by blending nano-Al2O3, PLLA and TPEE-g-MAH. The effects of amount of nano-Al2O3on its mechanical properties, thermal properties and crystallization behavior were studied. The results showed that the addition of nano-Al2O3decreased the thermal stability of PLLA/TPEE-g-MAH/nano-Al2O3composites.The reason was related to the reunion of nanoparticles.The degree of crystallinity of the composite materials improved with a little addition of nano-Al2O3。The strength and modulus of the composite materials decreased with increase of nano-Al2O3content;The elongation reach maximum143.51%when nano-Al2O3content is2%, and the impact strength reach maximum6.27KJ/m2when nano-Al2O3content is4%.Based on the above, the ternary composites have good comprehensive mechanical properties when the nano-Al2O3content is1%.