Polylactide plasticizers

Some of the com-derived glucose goes into various fermentation processes that lead to other chemical products. For example, large-scale production was recently announced for lactic acid and polylactide plastic derived from it. Citric acid and lysine are two other important fermentation products. 

Polylactide plasticized with acetyltributyl citrate has been investigated as a biodegradable barrier for use in guided-tissue regeneration therapy. ... 

The language used to describe these new (or sometimes old ) materials can be confusing, and too often is misused. One particularly problematic term is bioplastics. One common definition for bioplastics is plastics that are either biodegradable or made from renewable sources a clear recipe for confusion. We will not use this term. Rather, we will use the term biobased plastics to refer to plastics made from biological sources (typically plants). The plastics may be made directly by biological organisms (e.g., polyhydroxyalkanoates) or by chemical polymerization of monomers made from such sources (e.g., polylactide). Plastics may also be partially biobased (such as the CocaCola PlantBottle made from PET that is partially biobased). 

It is now January 1993, and the public is perceiving that the United States is burying itself in solid waste materials. ConAgra, Inc., has approached DuPont with a proposal for a joint venture to produce lactic acid for conversion to biodegradable polylactide plastics to be used in packaging and other markets that might help to alleviate the solid waste problem. 

Figure 11.28. Glass transition temperature, Tg, and crystallization temperature, T, of polylactide plasticized with variable amounts of epoxidized polypropylene glycol having molecular weight of 640 daltons. [Data from McCarthy S Song X, Antec 2001.Conference proceedings, Dallas, Texas, 6th-10th May, 2001, paper 363.]...

Figure 11.29. Crystallization enthalpy of polylactide plasticized with variable amounts of polypropylene glycol having molecular weight of 1000. [Data from Paul M-A Alexandre M Degee P Pluta M Gleski A Dubois P, New Nanocomposite Materials Based on Plasticized Poly(l-lactide) and Organo-modified Montmorillonites, Belgian Polymer Group Meeting 2002, Mens, Belgium.]...

Figure 11.30 shows that the tensile strength of a polylactide plasticized with epoxy-modified polypropylene glycol decreases monotonically with increased addition of plasticizer. Figure 11.31 shows that unplasticized polylactide has very small elongation. Addition a small amounts of polypropylene glycol rapidly increases elongation, which remains almost constant when more plasticizer is added. This is dire to the fact that a brittle behavior is replaced by a ductile behavior when some critical amount of plasticizer is present. ... 

There are several promising markets for biodegradable polymers such as polylactide. Plastic bags for household bio waste, barriers for sanitary products and nappies (diapers), planting cups, disposable cups and plates are some typical applications. To date no commercial large-scale production of polylactide exists, but this is likely to change in the near future. 

Jacobsen, S. and Fritz, H.G. 1999. Plasticizing polylactide, the effect of different plasticizers on the mechanical properties. Polymer Engineering and Science 39 1303-1310. 

Polylactide (PLA)-CaS04 composites toughened with low molecular weight and polymeric ester-like plasticizers and related performances. European Polymer Journal 44 3842-3852. 

Solarski, S., Mahjoubi, F., Ferreira, M., Devaux, E., Bachelet, P, Bourbigot, S., Delobel, R., Murariu, M., Da Silva Ferreira, A., Alexandre, M., Degee, P, and Dubois, P. 2007. (Plasticized) Polylactide/ clay nanocomposite textile Thermal, mechanical, shrinkage and fire properties. J. Mater. Sci., 42(13) 5105-5117. 

PLA is known both as poly(lactic acid) and as polylactide. It is currently the most used packaging plastic that is both biodegradable and biobased. PLA is a member of the polyester family, and is chemically synthesized from lactic acid that is derived from starch by fermentation. PLA has the following structure ... 

Pluta, M. Morphology and properties of polylactide modified by thermal treatment, filling with layered silicates and plasticization. Polymer 45, 8239-8251 (2004)... 

Pluta, M., Paul, M.A., Alexandre, M., Dubois, P. Plasticized polylactide/clay nanocomposites. I. the role of filler content and its surface organo-modification on the physico-chemical properties. J. Polym. Sci., Part B Polym. Phys. 44, 299-311 (2006)... 

Ray, S.S. and Okamoto, M. (2003) Biodegradable polylactide and its nanocomposites opening a new dimension for plastics and composites. Macromolecular Rapid Communications, 24, 815-840. 

Mechanical performance of material can also be influenced by the effect of the plasticizer on polymer crystallization. This was reported for plasticization of polylactide by fatty acid ester. This process requires not only the right combination of materials but also specific thermal conditions (in the reported study, crystalhzation was observed after exposing material to 100°C for 24 h). 

Plasticization of polylactide with a plasticizer being semi-solid at room temperature shows that incompatibility and formation of domains by the plasticizer may also lead to... 

Polylactide is a very popular, enviromnentaUy-friendly polymer, which needs plasticizers in its various apphcations. The following plasticizers have been used ... 

Figure 11.33. Tensile strength of oligomeric lactic acid plasticized polylactide. [Adapted, by permission, from Sinclair R Q T. Macromol. Sci. A, A33, No.5, 1996, p.585-97.]...

The flexibility will limit the applications of pure PBS polyester however, the disadvantage can be overcome by blending it with starch or polylactide. Blending with these rigid plastics will improve the modulus of the final products. 

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