Sugar based polymers biodegradation

It should be pointed out that the raw materials for VAM and its related polymers (i.e. ethylene and acetic acid) are produced from fossil resources, mainly crude oil. It is possible to completely substitute the feedstock for these raw materials and switch to ethanol, which can be produced from renewable resources like sugar cane, com, or preferably straw and other non-food parts of plants. Having that in mind, the whole production of PVAc, that nowadays is based on traditional fossil resources, could be switched to a renewable, sustainable and C02-neutral production process based on bioethanol, as shown in Fig. 3. If the vinyl acetate circle can be closed by the important steps of biodegradation or hydrolysis and biodegradation of vinyl ester-based polymers back to carbon dioxide, then a tmly sustainable material circle can be established. 

Currently, biodegradable plastics are considered to be eco-friendly because they can be broken down by the action of microorganisms in the environment. However, from the viewpoints of raw materials and energy sources, bio-based polymers have been produced from plant biomass. Unfortunately, at this point, bio-based polymers produced from edible sources such as com and sugar can generate new social problems. Furthermore, since bio-polyethylene has already been produced from bioethanol, some bio-based materials are not biodegradable plastics. 

Biopolymers are polymers that were produced from renewable natural sources, which are biodegradable, and are not toxic. These can also be produced by biological systems (i.e., microorganisms, plants and animals) or chemically synthesized from biological starting materials (e.g., sugars, starch, natural fats, oils, etc.). These biopolymers are an alternative source to petroleum-based polymers traditional plastics. The biopolyesters have properties similar to traditional polyesters. Starch-based polymers are often... 

The biodegradable polymer available in the market today in largest amounts is PEA. PEA is a melt-processible thermoplastic polymer based completely on renewable resources. The manufacture of PEA includes one fermentation step followed by several chemical transformations. The typical annually renewable raw material source is com starch, which is broken down to unrefined dextrose. This sugar is then subjected to a fermentative transformation to lactic acid (LA). Direct polycondensation of LA is possible, but usually LA is first chemically converted to lactide, a cyclic dimer of LA, via a PLA prepolymer. Finally, after purification, lactide is subjected to a ring-opening polymerization to yield PLA [13-17]. 

Polylactic acid (PLA) is a biodegradable polymer derived from lactic acid. It is a highly versatile material and is made from 100% renewable resources like corn, sugar beet, wheat and other starch-rich products. Polylactic acid exhibits many properties that are equivalent to or better than many petroleum-based plastics, which makes it suitable for a variety of applications. 

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. 

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