Polylactic Acid Based Blends, Composites and Nanocomposites
Biopolymers are expected to be an alternative for conventional plastics due to the limited resources and soaring petroleum price which will restrict the use of petroleum based plastics in the near future. PLA has attracted the attention of polymer scienti
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Polylactic Acid Based Blends, Composites and Nanocomposites Azman Hassan, Harintharavimal Balakrishnan and Abozar Akbari
Abstract Biopolymers are expected to be an alternative for conventional plastics due to the limited resources and soaring petroleum price which will restrict the use of petroleum based plastics in the near future. PLA has attracted the attention of polymer scientist recently as a potential biopolymer to substitute the conventional petroleum based plastics. The chapter aims to highlight on the recent developments in preparation and characterization of PLA blends (biodegradable and nonbiodegradable blends), PLA composites (natural fiber and mineral fillers) and PLA nanocomposites (PLA/montmorillonite, PLA/carbon nanotubes and PLA/cellulose nanowhiskers).
11.1 Introduction 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. It is known that agricultural raw materials such as sugarcane or corn can be used as basic materials in PLA production. However, waste biomass such as whey and cellulose waste can also be utilized. These basic materials will be transferred A. Hassan (&) H. Balakrishnan A. Akbari Enhanced Polymer Research Group (EnPRO), Department of Polymer Engineering, Faculty of Chemical Engineering, Universiti Teknologi Malaysia, 81300 Johor Bahru, Johor, Malaysia e-mail: azmanh@[email protected]
S. Thomas et al. (eds.), Advances in Natural Polymers, Advanced Structured Materials 18, DOI: 10.1007/978-3-642-20940-6_11, Springer-Verlag Berlin Heidelberg 2013
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FERMENTATION
BIOMASS
PURIFICATION
LIFE CYCLE OF PLA
LACTIC ACID
COMPOSTING PURIFICATION
DIMERIZATION POLYMERIZATION
POLYLACTIC ACID
Fig. 11.1 Life cycle of PLA
by means of a bacterial fermentation process into lactic acid which is the basic monomer needed for PLA production. Lactic acid can then be altered into lactide, the cyclic dimer of lactic acid through a combined process of oligomerization and cyclization. Preparation of PLA can be conducted by (1) ring-opening polymerization (ROP) of the dehydrated ring-formed dimer or dilactide, (2) polycondensation and manipulation of the equilibrium between lactic acid and polylacide by removal of reaction water using drying agents, or (3) polycondensation and linking of lactic acid monomers. Due to the existence of a chiral carbon in lactic acid, the repeating unit of PLA can have two different configurations (D-(dextro) or L-(levo)) and the relative amount and distribution of these stereo-isomers influences various properties of the resulting PLA. In general, PLA built with L-stereoisomer monomer is referred to as poly(L-lactic acid) (PLLA), whereas, PLA w
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