Study On Blending Modification Of Poly (Lactic Acid)

In this paper Poly (lactic acid) (PLA) is blending, plasticizing, compositing modified with thermoplastic starch (TPS), acetyl tributyl citrate (ATBC), Poly(1,3-butylene adip ate) (PBA) and carbon black (CB) to improve the properties of PLA through melting blending technique respectively.After blending PLA with TPS, not only can decrease the cost of PLA, but also increase the application. Water is realized as an important plasticizer for the plasticization of TPS during research. It is impossible to achieve high plasticized dry starch in the present of glycerol. At the same, PLA can be depolymerized in the presence of water at elevated temperatures, which decreases the molecular of PLA and results in poor mechanical properties. In order to increase the plasticization of dry starch and the dispersion in immiscible PLA/thermoplastic dry starch (DTPS) blend, citric acid (CA) is used as plasticization accelerant and dispersant for DTPS and PLA/DTPS blend respectively. 2wt% CA can dramatically increase the plasticization and the fluidity of DTPS. So the dispersion between PLA and DTPS can be increased in our research.Maleic anhydride (MAH) with initiator Dicumyl peroxide (DCP) is used as reactive compatibilizer to increase the compatibility in PLA/DTPS blend through two step extrusion processing. In the present of MAH and CA, the dispersion and compatibility in PLA/DTPS blend dramatically increased in our research. So a high performance PLA/DTPS blend can be achieved. The tensile strength of PLA/DTPS blend can reach to 40MPa, which is higher than pure PLA. Moreover the compabilizing mechanism of phase dispersion-grafting synergism in PLA/DTPS blends is advanced.ATBC is a kind of environment friendly plasticizer which can plasticize PLA effectively. But the plasticization and application of PLA is dramatically influenced by the migration of ATBC. So in this paper PBA as a novel plasticizer is used to plasticize PLA. Compared with ATBC, PBA is more effective to plasticize PLA when the plasticizer content is higher than 20wt%. The elongation at break of PBA plasticized PLA can excess 600%, and the tensile strength keep 23.7MPa. So PBA has stronger practicability. Moreover hydrophobic plasticizers can also increase melting processing and water vapor permeability properties.CB not only can increase the tensile strength of PLA, but also conductive polymer composites came from renewable source can be achieved. And the electrical conductivity can be controlled by the content of CB and plasticizer. The compatibility between PLA and CB dramatically increases after CB is dipped by ATBC or PBA. So a high dispersion PLA/CB composite can be achieved. In the present of plasticizer the electrical conductivity of PLA/CB composite increase 1 quantity class. Moreover the tensile stress and elongation at break keep at 45MPa and 100% respectively. Finally the migration of plasticizer and water vapor permeability are restrained in the present of CB.