Alternatives to Petro-Based Polymers

Closure Covering Wound cover, local hemostasis 

Scaffold Cellular proliferation Skin reconstruction, blood vessel reconstruction 

Capsulation Controlled drug delivery Sustained drug release 

PLLA plates give rise to voltage, which enhances bone regeneration [181], Meanwhile, self-reinforced (SR)-PLLA and PDLLA are used as stent [426] and screw [427] materials. 

In addition to the conventional uses of PLLA and its copolymers as microspheres or micro-capsules for drug delivery systems, PLLA microspheres or microcapsules have recently been approved by the FDA for the restoration and correction of facial fat loss caused by the human immunodeficiency virus (HIV)/AIDS without acute side effects [41]. Moreover, PLLA microspheres have been applied as embolization materials to control arterial malformation, haemorrhage and tumours without complications [41]. 

---

Over the past several decades, polylactide - i.e. poly(lactic acid) (PLA) - and its copolymers have attracted significant attention in environmental, biomedical, and pharmaceutical applications as well as alternatives to petro-based polymers [1-18], Plant-derived carbohydrates such as glucose, which is derived from corn, are most frequently used as raw materials of PLA. Among their applications as alternatives to petro-based polymers, packaging applications are the primary ones. Poly(lactic acid)s can be synthesized either by direct polycondensation of lactic acid (lUPAC name 2-hydroxypropanoic acid) or by ring-opening polymerization (ROP) of lactide (LA) (lUPAC name 3,6-dimethyl-l,4-dioxane-2,5-dione). Lactic acid is optically active and has two enantiomeric forms, that is, L- and D- (S- and R-). Lactide is a cyclic dimer of lactic acid that has three possible stereoisomers (i) L-lactide (LLA), which is composed of two L-lactic acids, (ii) D-lactide (DLA), which is composed of two D-lactic acids, and (iii) meso-lactide (MLA), which is composed of an L-lactic acid and a D-lactic acid. Due to the two enantiomeric forms of lactic acids, their homopolymers are stereoisomeric and their crystallizability, physical properties, and processability depend on their tacticity, optical purity, and molecular weight the latter two are dominant factors. 

Poly(L-lactic acid) is an effective alternative to petro-based polymers in applications such as packaging material, automotive materials, including floor mats and spare tire covers, and the chassis of electrical appliances such as computers, mobile phones, remote controls, and optical disks [422,423]. Figure 8.26 shows the commodity applications of PLLA. For... 

---