Processing of Poly lactic acid

Similar to many semicrystalline polymers, PLA exhibits both Tg and 7j . The Tg of PLA can range from 35 to 60°C depending on molecular weight, the presence of plasticizers, physical aging, polymer architecture, and degree of crystallinity [14]. Above Tg PLA is rubbery, while below Tg it becomes a glass, but it is still able to creep until it is cooled to its 3 transition temperature at approximately —45°C, below which it behaves like a brittle polymer [15]. In applications where mechanical properties are important, such as packaging 

Polyilactic acid) Synthesis, Structures, Properties, Processing, and Applications, edited by R. Auras, L.-T. Lim, S. E. M. Selke, and H. Tsuji Copyright 2010 John Wiley Sons, Inc. 

FIGURE 14.1 Comparison of glass transition and melting temperatures of PLA with other thermoplastics [18]. 

TABLE 14.1 Primary Transition Temperatures of Selected PLA Copolymers 

Copolymer Ratio Glass Transition Temperature (°C) Melting Temperature (°C) 

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Carrasco, E., Pages, P., Gamez-Perez, J., Santana, O.O., Maspoch, M.L. Processing of poly (lactic acid) Characterization of chemical structure, thermal stability and mechanical properties. Polym. Degrad. Stab. 95, 116-125 (2010)... 

Poly(amino acids) are insoluble in common solvents, are difficult to fabricate due to high melting point, and absorb a significant amount of water when their acid content reaches over 50 mol%. To solve these problems, polyesters derived from amino acids and lactic acids [e.g., poly (lactic acid-co-lysine) PLAL] are developed. The PLAL system is further modified by reaction with lysine A-carboxyanhydride derivatives. Another modification of poly(amino acids) includes poly(iminocarbon-ates), which are derived from the polymerization of desaminotyrosyl tyrosine alkyl esters. These polymers are easily processable and can be used as support materials for cell growth due to a high tissue compatibility. Mechanical properties of tyrosine-derived poly(carbonates) are in between those of poly(orthoesters) and poly(lactic acid) or poly(gly-colic acid). The rate of degradation of poly(iminocarbonates) is similar to that of poly (lactic acid). 

Verrecchia,T., Huve, P., Bazile, D., Veillard, M., Spenlehauer, G., and Couvreur, P. (1993), Adsorption/desorption of human serum albumin at the surface of poly(lactic acid) nanoparticles prepared by a solvent evaporation process,/. Biomed. Mater. Res., 27(8), 1019-1028. 

Albertsson, A.-C., Varma, I.K., Lochab, B. et al. (2010) Design and synthesis of different types of poly(lactic acid), in Poly(Lactic Acid) Synthesis, Structures, Properties, Processing, and Applications (Wiley Series on Polymer Engineering and Technology) (eds R. Auras, L.-T. Lim, S.E.M. Selke and H. Tsuji), John WUey Sons, Inc., NJ, pp. 43-58. 

Fujimaki T (1998) Processability and properties of aliphatic polyesters, Bionolle , synthesized by polycondensation reaction. Polym Degrad Stab 59 209-214 Garlotta D (2001) A literature review of poly(lactic acid). J Polym Environ 9 63-84 Gatenholm P, Kubat J, Mathiasson A (1992) Biodegradable natural composites. I. Processing and properties. J Appl Polym Sci 45 1667-1677... 

Signori, F., Coltelli, M.-B., Bronco, S. Thermal degradation of poly(lactic acid) (PLA) and poly(butylene adipate-co-terephthalate) (PBAT) and their blends upon melt processing. Polym. Degrad. Stab. 94, 74-82 (2009)... 

The market for high polymers from lactic acid is still in its early stages. A large market growth for the polymer requires additional sources of lactic acid as raw material. Cargill started-up a 4.5 kton/year lactic acid/poly-lactide plant in 1994 and announced a large plant with a capacity as high as 114 kton/year in the next years. Other producers of poly-lactic acid are Mitsui Toatsu Chemical (which has developed a polycondensation process of lactic acid), Shimatsu, Dainippon Ink, and Neste. 

Lee, S. and Lee, J.W. (2005) Characterization and processing of biodegradable polymer blends of poly (lactic acid) with poly(butylene succinate adipate). Kor.-Aust. Rheol. J., 17,... 

Datta R, Glassner DA, Jain MK, Vick Roy JR (1992) Fermentation and purification process for succinic acid. US Patent 5,168,055 Datta R, Tsai S-P, Bonsignore P, Moon S-H, Frank JR (1995) Technological and economic potential of poly (lactic acid) and lactic add derivatives. FEMS... 

Similar to the synthesis of poly(lactic acid), the polycondensation of glycolic add is the simplest process available to prepare PGA but it is not the most efficient one because it yidds low-molecular-wdght products. The procediue is as follows glycolic add is heated at atmospheric pressiue and a temperature of about 175-185 C during a time necessary for removing water. Subsequently, the reaction pressure is reduced... 

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