The case of biodegradable polyesters

Aliphatic copolyester Poly(butylenesuccinate o-adipate) (PBSA) 

Aromatic copolyester Polyfbutylene adipate-co-terephthalate) (PBAT) 

1) the monomers (enantiomers D and L) are condensed and then de-polymerized and converted into lactides  

Depending on the preparation conditions, PLLA crystalhzes in a variety of forms [AVE 13]. The a form exhibits a clearly defined diffraction diagram. This crystalline structure is more stable than the P form. It has a melting point (Tf) of 185°C, as 

PLA is a rigid polymer at ambient temperature (see Table 9.1). It crystalhzes slowly, like PET. The ciystalhzation kinetics of PLA has been extensively studied. Like PET, PLA can be oriented by thermomechanical treatment. Orienting the chains notably increases its mechanical strength. 

---