Polylactic Acid (PLA)
01/31/2015 through 10/17/2012
Patent Abstracts (5)
Patent Titles (3)
Polylactic Acid (PLA) Applications
Polylactic Acid (PLA) Copolymers
Polylactic Acid (PLA) Foams
Polylactic Acid (PLA) Materials
Poly(lactic acid) or polylactide (PLA) is a thermoplastic aliphatic polyester derived from renewable resources, such as corn starch (in the United States), tapioca products (roots, chips or starch mostly in Asia) or sugarcanes (in the rest of world). It can biodegrade under certain conditions, such as the presence of oxygen, and is difficult to recycle.
The name "polylactic acid" is to be used with caution, not complying to standard nomenclatures (such as IUPAC) and potentially leading to ambiguity (PLA is not a polyacid (polyelectrolyte), but rather a polyester).
Bacterial fermentation is used to produce lactic acid from corn starch or cane sugar. However, lactic acid cannot be directly polymerized to a useful product, because each polymerization reaction generates one molecule of water, the presence of which degrades the forming polymer chain to the point that only very low molecular weights are observed. Instead, two lactic acid molecules undergo a single esterfication and then catalytically cyclized to make a cyclic lactide ester. Although dimerization also generates water, it can be separated prior to polymerization due to a significant drop in polarity. PLA of high molecular weight is produced from the dilactate ester by ring-opening polymerization using most commonly a stannous octoate catalyst, but for laboratory demonstrations tin(II) chloride is often employed. This mechanism does not generate additional water, and hence, a wide range of molecular weights is accessible.
Due to the chiral nature of lactic acid, several distinct forms of polylactide exist: poly-L-lactide (PLLA) is the product resulting from polymerization of L,L-lactide (also known as L-lactide). PLLA has a crystallinity of around 37%, a glass transition temperature between 60-65 °C, a melting temperature between 173-178 °C and a tensile modulus between 2.7-16 GPa. However, heat resistant PLA can withstand temperatures of 110C (230F).
(Wikipedia, Polylactic Acid, 5/2/2012)
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Roger D. Corneliussen
Maro Polymer Links
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* Date of latest addition; date of first entry is 5/2/2012.