Lactic Acid: Precursor for Polylacticacid

What is Lactic acid:

Lactic acid is the precursor for the synthesis of polylactic acid through the polycondensation route.   L-lactic acid is a natural material that occurs in the metabolism of all animals and microorganisms, and therefore, non toxic to the living beings in smaller concentrations.

L Lactic acid molecular structure

Lactic acid is derived from renewable resource starches including corn starch, tapioca and potatoes.  Process starts with milling the starch to get glucose.   Sugar feed stocks are also can be obtained directly from agricultural resources such as sugar beets or sugar cane.  Then, lactic acid is produced by anaerobic fermentation of dextrose to produce lactic acid.

Chirality of Lactic acid:

Lactic acid is the smallest natural material with a chiral center.  As shown below, it’s stereoisomers  L-lactic acid and D-lactic acid could produce polylactic acid with range of properties.

Polylactide:

Poly(lactic acid) can be synthesized through the polycondensation reaction of lactic acid.  However, in order to drive the reaction forward to obtain high molecular weight polymer, the water produced as a byproduct has to be removed.  The process involves high temperatures and longer reaction times, thus, usually; ring opening polymerization of lactide is the preferred method of producing high molecular weight polylactide (PLA).

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