Study On Preparation Of PLA/PBS Blends By Vane Extruder And Their Compatibilization Characteristics

With the growing public awareness about environmental pollution problem, there is an important role of biodegradable materials has attracted much attention to solve the white pollution. But each kind of biodegradable material has its disadvantages. Such as, poly lactic acid(PLA) has a faster degradation rate but low toughness, poly butylene succinate(PBS) has a higher deformation temperature but lack of strength. From the feasibility and effect into consideration, the polymer melt blending modification is an important way to achieve the complementary properties of polymer materials. Traditionally, the polymer melt blending modification processing equipment is screw extruder. Its core is a kind of processing method based on the shear flow field, in the form of high energy consumption, thermal mechanical process long and strong dependence on characteristics of materials, etc. In order to overcome these shortcomings, the vane extruder was invented by the Key Laboratory of Polymer Processing Engineering of Ministry of Education, South China University of Technology. Compared with the traditional screw extruder, based on the volume elongational flow field of the vane extruder machine has save energy consumption, improve the transmission efficiency and has the advantages of materials wider adaptability. Therefore, there are important theoretical and practical significance to compatibilization mechanism of incompatible biodegradable materials researched by vane extruder.In this paper, the PLA/PBS blends through melt blending modified method were prepared by the vane extruder, as the object of study the structure and properties of biodegradable incompatible blends. Firstly, by means of Fourier transform infrared spectra and 13 C NMR spectra proved that the chemical reaction didn’t happen between PLA and PBS. And then through morphology characterization and rheological method studies the incompatible blending system structure and viscoelastic, especially the composition ratio of system influence the formation and evolution of phase morphology, to establish the relationship between the morphology and rheology of incompatible. Then using contact angle test method for determining the interfacial tension of PLA/PBS blends, in order to determine the effect of interfacial tension on the phase morphology.On this basis, we added the nanometer montmorillonite(MMT) to PLA/PBS blends, and examined the compatibilizing system. By scanning electron microscopy and polarizing microscope to observe the dispersion of MMT/PLA/PBS blend phase morphology, we found that the addition of MMT nanoparticles, the particle size of the dispersed phase decreased. Through the wide angle X-ray diffraction and transmission electron microscope observation showed that molecular chain successfully inserted into the layers of MMT, reduce the interfacial tension of blend system, improve the compatibility of the blend system. And then using the thermogravimetric analysis test shows that the addition of MMT can effectively improve the performance of thermal stability of the blends.With the active epoxy group of ethylene butyl acrylate glycidyl methacrylate copolymer(PTW) reactive compatibilization of PLA/PBS blends, through scanning electron microscope test, found that the dispersed phase particle size of PBS decreases obviously, the interface bond is enhanced, the phase morphology was improved and better compatibilization effect. Although there will be some grafting reaction, increase the viscosity of the blends, but will not destroy the macromolecular chain structure of PLA and PBS. In addition, the addition of PTW would strongly affect the thermal behavior of the blends, the glass transition temperature of both PLA and PBS are close to each other, and the crystallization ability of blends increased. From the contact angle experiment showed that, with the increase of PTW content, the contact angle values of the MMT/PLA/PBS blends with the diiodomethane become smaller and smaller, suggesting that the addition of PTW improved the compatibility of PLA/PBS blends.This paper also studied with active-NCO group of six methylene diisocyanate(HDI) reactive compatibilization of PLA/PBS blends. By polarized light microscopy, after adding HDI, the phase interface of PLA and PBS become blurred, thickening of the interface layer, increase the interface bonding, reduces the interfacial tension, and refine the dispersed phase in the blends. Compared with the blends without the compatibilizer, the decrease of the interfacial tension and interfacial layer thickening, leading to the impact strength of the system increased substantially. Though the rheological test, the addition of HDI can effectively improve dynamic storage modulus, dynamic loss modulus and complex viscosity of the blends. This suggests that the chemical reaction for the addition of HDI could limit the movement of molecular chains, especially in low shear frequency area. The mechanical tests of the samples after annealed show that the tensile properties and flexural properties of the blends were all improved, especially the impact properties were improved obviously.The study shows that adding MMT, PTW, HDI as the compatibilizer could successfully extruded to get high performance PLA/PBS blends via the vane extruder with high dispersion mixing efficiency and enforcement capacity.