An Overview of Polylactides as Packaging Materials

Abstract

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.

Mechanical study of PLA–PCL fibers during in vitro degradation

“…For these PLA-PCL fibers, no significant differences were observed among the different dimensions tested, either in terms of strength and molecular weight evolutions during degradation (see figure 5). One can conclude that, in the present case, water diffusion can be assumed instantaneous and that hydrolysis takes place homogenously throughout the samples (bulk degradation without autocatalysis) (Auras, R. et al, 2004). where u s is the strength decrease rate of the material.…”

“…When τ H >> τ D, water reaches the core of the material before it reacts, and the degradation starts homogenously. This is the case of PLA-PCL (Saha and Tsuji, 2009;Auras, R. et al, 2004). When τ H << τ D , water reacts totally in the superficial layer and will never reach the core of the material.…”

Optimising Ductility of Poly(Lactic Acid)/Poly(Butylene Adipate-co-Terephthalate) Blends Through Co-continuous Phase Morphology

“…derived from renewable feedstocks, have the added advantage of a reduced carbon footprint. In the growing bio-based economy, poly(lactic acid) (PLA) is one of the most prominent thermoplastics [4]. It is used in packaging and other short-life disposable applications, as well as in biomedical products because of its biocompatibility.…”

Characterization of PLA-limonene blends for food packaging applications

“…In addition, the control of light transmission through packaging is an important parameter to preserve and protect some food products until they reach the consumer. So, additives are require for transparent PLA films to block light transmission [22]. Furthermore, PLA modified with natural origin compounds has been proposed as active packaging [8,23,24].…”