Study On The Preparation And Properties Characaterization Of PLLA/SA Blends

In order to reduce the cost of the polylactic acid (PLLA) material and improve its flexibility to expand the application of PLA-based plastic,we used PLLA and starch acetate (SA) as the main raw material, tetrabutyl titanate (Ti(OBU)4) as compatibilizer, and triethyl citrate (TEC) as plasticizer,to prepare a series of PLLA/ SA blends by melt mixing firstly.It was investigated the effect of the content of SA,the compatibilizer and its content, the plasticizer and its content on the mechanical properties,dynamic mechanical properties,structure and morphologies, heat-resistant performance,melt flow rate and water-resistant performance and other implications of blends. The results of research show that:The compatibility of PLLA and SA of the blends was improved to some extent after adding the compatibilizer.SA content, addition of compatibilizer and its content, addition of plasticizer and its content, all of them affect the mechanical properties greatly.The appropriate content of the compatibilizer can improve the compatibility of PLLA/SA blends effectively, while the flexibility of the blends can be improved by adding the plasticizer.When the content of the SA is 25%, the content of compatibilizer is 8%, and the the content of plasticizer is 10%, the stiffness and the strength of the blends declined, while the flexibility is improved greatly as compared with pure PLLA material,The results of dynamic mechanical analysis showed that the varying trend of the tanδpeak temperature and the storage modulus with increasing temperature is similar under different frequency.It illustrates that the change of the frequency has little influence on the storage modulus and the internal friction.But the content of SA and the content of the compatibilizer have greater impact on the storage modulus.As the content of the compatibilizer increases, the tanδpeak temperature moves to a lower temperature, and the storage modulus of the blends decreases.With increasing the content of SA in the blends, the tanδpeak temperature moved to a higher temperature, and the storage of the blends increases. But, when the content of SA is increased over 25%, Tanδpeak temperature and the storage modulus.keep constant. The storage modulus of the blends decreases greatly after adding the plasticizer, Tanδpeak temperature is enhanced.Thermogravimetric analysis showed that the compatibilizer and the plasticizer also have the effect on the heat-resistant of the blends, and the blend without the compatibilizer has worse heat resistance.When the content of the plasticizer is definite, the material heat resistance is improved with the increase of compatibilizer's content compared to the blends without the compatibilizer. Compared with PLLA raw material, the range of the thermal degradation temperature is wider. The blends degrade almost completely when the temperature rises to 360℃.SA content, the addition of compatibilizer and plasticizer and their contents have a certain effect on MFR of PLLA/SA blends.The MFR of blends compatibilized without plasticizer is higher than the system without compatibilizer, and it increases with SA content inceased. With the fixed content of compatibilizer(2%), the MFR of the blends with plasticizer is higher than the blends without plasticizer;When SA content and plasticizer content are certain, the MFR of the blends increases first and then decreases with the increase of the compatibilizer content. When the compatibilizer content is 8%, the MFR reach the minimum and is 3.62g/10min, but is still higher than that of pure PLLA (MFR 2.04g/10min), which shows that the blends have better mobility than PLA, and are more suitable for the requirements of the plastic molding.SEM analysis shows that the appropriate amount of the compatibilizer could improve the compatibility of the PLLA/SA blends effectivelly, and the system's compatibility gets worse with the content of SA increasing.Through inverstigating the water resistance, we find that the water absorption gradually increases with the SA's content incrasing.The blends'water absorption is' enhanced after the addition of the compatibilizer. When the copatibilizer content is lower(2%),except 25% content of SA the other blends'tensile strengths after water absorption are improved. When the content of SA is fixed(25%), by increasing the content of compatibilizer, the tensile strengths after water absorption decrease, and the extent is not great when the content of compatibilizer is 8%.The addition of SA and the plasticizer improves the biodegradability of PLLA, but no regularity is found between the enhancment and the content of both.