Natural plastic polylactic acid

Bio-based materials are materials that are taken from or made from natural materials in living things. Examples include packing pellets made from corn and soybeans, polylactic acid (a polymer used to make plastic packaging), and various kinds of pharmaceuticals. 

Polylactic acid (PLA) has caught the attention of polymer scientist and proving to be a viable alternative biopolymer to petrochemical based plastics for many applications. PLA is produced from lactic acid, that is derived itself from the fermentation of corn or sugar beet and due to its biodegradation ability, PLA presents the major advantage to enter in the natural cycle implying its return to the biomass. The life-cycle of PLA is shown in Fig. 11.1. 

Natural polymers such as starch and protein are potential alternatives to petroleum-based polymers for a number of applications. Unfortunately, their high solubility in water limit their use for water sensitive applications. To solve this problem thermoplastic starches have been laminated using water-resistant, biodegradable polymers. For example, polylactic acid and P(3HB-co-3HV) were utilised as the outer layers of the stratified polyester/PWS (plasticized wheat starch)/polyester film strucmre in order to improve the mechanical properties and water resistance of PWS which made it useful for food packaging and disposable articles [65]. Moreover, improved physic-chemical interactions between P(3HB-CO-3HV) and wheat straw fibres were achieved with high temperature treatment. It resulted in increased P(3HB-co-3HV) crystallization, increased Young s moduli and lowered values of stress and strain to break than the neat matrix of P(3HB-co-3HV). There was no difference in the biodegradation rate of the polymer [66]. 

Back to Nature is the solution then Looking at a few numbers in Table 4.7 may prevent hasty judgments reading this questioa About 50 million t of plastics are produced in Europe each year from petroleum. The production of natural polymers is about 0.1% percent of this total virtually all of which is poly lactic acid. These numbers are not promising it would be lunacy to expect that polylactic acid (Fig. 4.30) or any other semi-synthetic and biodegradable polymer could replace petroleum-based plastics in any foreseeable future. 

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,... 

Biobased polymers are those made from natural or organic ingredients, such as starch from corn, potato, tapioca, rice, or wheat (Narayan 2006a, 201 lb). Biobased polymers can also be made from oils, such as palm seed, linseed, soy bean, or fermentation products, like polylactic acid (PEA), polyhydroxy alkanoate (PHA), and polyhydroxybutyrate (PHB). BPI World provides a listing of compostable plastic resins, bags, cutlery, and packaging (BPI World 2013). 

Synthetic environment friendly polymers with precnrsors from natural resource such as polylactic acid have shown enormous potential to snbstitute a wide variety of conventional fossil based packaging plastics and have been demonstrated to be even commercially viable. In view of this, a detailed description about various aspects of PLA such as synthesis, properties, and processing have been discussed as below. 

K. Oksman and J. F. Selin. Plastics and composites from polylactic acid. In Natural Fibers, Plastics and Composites, F. T. Wallenberger,... 

Polylactic acid or PLA is a plastic made from com, an annually renewable resource, leading to 100% biodegradability and compostability. Plastic products made from com are in all common household products all around the world. The NatureWorks PLA is derived from naturally occurring plant starch. According to the NatureWorks LLC website, the different steps of the transformation of plant sugar into NatureWorks PLA are the following [14] ... 

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