Polylactide polymers have gained enormous attention as a replacement for conventional synthetic packaging materials in the last decade. By being truly biodegradable, derived from renewable resources and by providing consumers with extra end-use benefits such as avoiding paying the "green tax" in Germany or meeting environmental regulations in Japan, polylactides (PLAs) are a growing alternative as a packaging material for demanding markets. The aim of this paper is to review the production techniques for PLAs, summarize the main properties of PLA and to delineate the main advantages and disadvantages of PLA as a polymeric packaging material. PLA films have better ultraviolet light barrier properties than low density polyethylene (LDPE), but they are slightly worse than those of cellophane, polystyrene (PS) and poly(ethylene terephthalate) (PET). PLA films have mechanical properties comparable to those of PET and better than those of PS. PLA also has lower melting and glass transition temperatures than PET and PS. The glass transition temperature of PLA changes with time. Humidity between 10 and 95% and storage temperatures of 5 to 40 degrees C do not have an effect on the transition temperature of PLA, which can be explained by its low water sorption values (i.e. <100 ppm at Aw = 1). PLA seals well at temperatures below the melting temperature but an appreciable shrinking of the films has been noted when the material is sealed near its melting temperature. Solubility parameter predictions indicate that PLA will interact with nitrogen compounds, anhydrides and some alcohols and that it will not interact with aromatic hydrocarbons, ketones, esters, sulfur compounds or water. The CO2, O2 and water permeability coefficients of PLA are lower than those of PS and higher than those of PET. Its barrier to ethyl acetate and D-limonene is comparable to PET. The amount of lactic acid and its derivatives that migrate to food simulant solutions from PLA is much lower than any of the current average dietary lactic acid intake values allowed by several governmental agencies. Thus, PLA is safe for use in fabricating articles for contact with food.

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Packaging waste accounted for 78.81 million tons or 31.6% of the total municipal solid waste (MSW) in 2003 in the USA, 56.3 million tons or 25% of the MSW in 2005 in Europe, and 3.3 million tons or 10% of the MSW in 2004 in Australia. Currently, in the USA the dominant method of packaging waste disposal is landfill, followed by recycling, incineration, and composting. Since landfill occupies valuable space and results in the generation of greenhouse gases and contaminants, recovery methods such as reuse, recycling and/or composting are encouraged as a way of reducing packaging waste disposal. Most of the common materials used in packaging (i.e., steel, aluminum, glass, paper, paperboard, plastics, and wood) can be efficiently recovered by recycling; however, if packaging materials are soiled with foods or other biological substances, physical recycling of these materials may be impractical. Therefore, composting some of these packaging materials is a promising way to reduce MSW. As biopolymers are developed and increasingly used in applications such as food, pharmaceutical, and consumer goods packaging, composting could become one of the prevailing methods for disposal of packaging waste provided that industry, governments, and consumers encourage and embrace this alternative. The main objective of this article is to provide an overview of the current situation of packaging compostability, to describe the main mechanisms that make a biopolymer compostable, to delineate the main methods to compost these biomaterials, and to explain the main standards for assessing compostability, and the current status of biopolymer labeling. Biopolymers such as polylactide and poly(hydroxybutyrate) are increasingly becoming available for use in food, medical, and consumer goods packaging applications. The main claims of these new biomaterials are that they are obtained from renewable resources and that they can be biodegraded in biological environments such as soil and compost. Although recycling could be energetically more favorable than composting for these materials, it may not be practical because of excessive sorting and cleaning requirements. Therefore, the main focus is to dispose them by composting. So far, there is no formal agreement between companies, governments and consumers as to how this packaging composting will take place; therefore, the main drivers for their use have been green marketing and pseudo-environmental consciousness related to high fuel prices. Packaging compostability could be an alternative for the disposal of biobased materials as long as society as a whole is willing to formally address the challenge to clearly understand the cradle-to-grave life of a compostable package, and to include these new compostable polymers in food, manure, or yard waste composting facilities.

High molecular mass poly(lactide), (PLA), is an attractive polymer family because in addition to being thermoplastic, biodegradable, compostable, and produced from annually renewable resources, it shows mechanical and barrier behavior comparable to synthetic polymers like polystyrene (PS) and polyethylene terephthalate (PET). Furthermore, technology for large-scale fabrication of PLA has been fully developed. However, there is still a need to better understand the properties of PLA as this polymer is adapted to packaging applications, especially for food packaging. In this work, films from two PLA resins were studied by tensile testing; differential scanning calorimetry (DSC); and permeation of carbon dioxide, oxygen, and water vapor. The data from these two PLA film samples are compared to those of PS and PET.

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