Polylactide thermoplastics

Huneault MA, Li H. Morphology and properties of compatibilized polylactide/thermoplastic starch blends. Polymer 2007 48 270-80. 

Morphology and Properties of Compatibilized Polylactide/Thermoplastic Starch Blends, Michel A. Huneault, Hongbo Li, Polymer, available on-line, 2006, In press for 2007. 

Since 1989, Cargill, has invested some 750 million to develop and commercialize polylactic acid (tradename NatureWorks). Its Nebraska plant, with an annual capacity of 140,000 metric tons, opened in 2002. Thus, polylactides, combining favorable economics with green sustainability, are poised to compete in large-volume markets that are now the domain of thermoplastic polymers derived from petrochemical sources. 

Much has been written about Cargill Dow LLC s polylactide (PLA) polymer, also known as NatureWorks PLA. PLA is a thermoplastic produced from biomass sugars by fermentation. The fermentation product, lactic acid, is converted into a lactide that is purified and polymerized using a special ring-opening process (18). 

The second concept for the generation of monolithic polymers is based on diblock copolymers which were prepared by Hillmyer and coworkers [27]. These copolymers contain oriented nanoscopic cylinders of the degradable polymer polylactide (PLA) which were embedded in polystyrene. The latter served as an inert thermoplastic matrix, while PLA could be selectively removed under well-defined conditions using sodium hydroxide in aqueous methanol. The resulting mesoporous monolithic polystyrene contains nanochannels with defined pore size. The major drawback of this material free of any cross-linker is associated with reduced mechanical and chemical stability. 

It is an aliphatic polyester derived from renewable resources, such as com starch, tapioca roots, chips or starch, or sugarcane. Polylactic acid or polylactide (PLA) can withstand temperatures up to 110 °C [69]. PLA is soluble in chlorinated solvents, hot benzene, tetrahydrofuran, and dioxane [70]. It can be processed like other thermoplastics into fiber (for example, using conventional melt spinning processes) and film. Due to the chiral nature of lactic acid, several distinct forms of polylactide exist ... 

One of the most studied blends has been the one composed of P(3HB) and polylactide, both commercially available polymers with superior thermal and mechanical properties than other commercial polymers. Polylactide is a chemically synthesized, biodegradable thermoplastic and derived from renewable resources. It has been shown that this blend exhibited greater flexibility and hydrolytic biodegradation than the Polylactide or P(3HB) alone [75]. 

Polylactides (PLA) and copolymers are also of interest in biodegradable applications. This material is a thermoplastic polyester synthesized from the ring opening of lactides. Lactides are cyclic diesters of lactic acid.2 A similar material to polylactide is polyglycolide (PGA). 

P. Sarazin, G. Li, W.J. Orts, B.D. Favis, Binary and ternary blends of polylactide, poly-caprolactone and thermoplastic starch. Polymer 49 (2) (2008) 599-609. 

N. Whiteman, P. DeLassus and J. Gunderson, New Flavor and Aroma Barrier Thermoplastic, Polylactide, Polyolefins 2002, International Conference on Polyolefins, Houston, TX, USA, 2(X)2. 

The production of durable functional products without using petroleum based raw materials is a focus of much academic research today but it is also prioritized by many industries. Many questions still remain concerning the use, production and properties of biobased and/or degradable polymers and whether or not they are more environmentally friendly than oil-based products. Polylactide is a bio-based compostable thermoplastic that is considered as one of the most promising materials for replacement of traditional volume plastics. The properties of polylactide can be tuned to... 

Polylactic acid or polylactide (PLA) is a thermoplastic aliphatic polyester that can be derived from renewable resources, such as corn starch or sugarcanes. Although PLA has been known for more than a century, it has become of great commercial interest in recent years because of its renewability and degradability to natural metabolites. In addition, the properties of PLA can be varied over a wide range which makes it suitable to be used as a substitute to many petroleum based commodity plastics, such as polyolefins,... 

Polylactide has high potential in agricultural applications such as mulch films either in pure form or blended with other polymers such as thermoplastic starch. In addition, polylactide is used in compostable yard bags and dog poop bags. Lactic acid based hot-melt adhesives have also been developed (90). Foamed PLA could be used as structural protective foams, loose-fill packaging and insulation material as an alternative for expanded polystyrene (EPS). While packaging is currently the high volume application... 

Among the most important biodegradable polymers, we can specially mention thermoplastic starch (TPS), polylactide (PLA), polycaprolactone (PCL), and polyhydroxybutyrate and polyhydroxyalkanoate (PHA) due to their promising properties. 

The three most common biobased biodegradable polymers are PLA, PHA, and TPS. PLA, PHA, and TPS can be made into plastic containers, packaging, bags, and bottles. All three biobased polymers can be processed with traditional plastics processing equipment. Polyhydrox-yalkanoates can be made from over 100 monomers based on P3HB, P4HB, PHB, and PHV. PHA is produced in the cells of several types of bacteria. Polylactide, or polylactic acid, is made from starch and bacteria. Thermoplastic starch is a blend of starch and other additives. 

Biodegradable polymers made from cyclic esters have received increasing attention as resorbable biomaterials as well as commodity thermoplastics. Although the CAGR amounts to 20-30%, it is still a niche market accounting for around 1% of the synthetic plastics. Among the monomers, lactic acid, either produced by fermentation or chemical processes, gives access to polylactides (Scheme 21.16)... 

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