In recent years, there has been an expansion of biopolymer
research activities in order to overcome the environmental impact
produced by petroleum-based plastic residue. Among the vast
number of biopolymers studied, two of the most promising are
poly(3-hydroxybutyrate) (PHB) and polylactic acid (PLA), both
biodegradable and biocompatible polyesters that can be produced
from renewable resources.
PHB is a natural polymer synthesized by different species of
bacteria as an intracellular storage material with a remarkable
stereo-regularity of the perfectly isotactic chain configuration,
which gives it unusually high crystallinity. It is a crystalline thermoplastic
polyester with similar properties to those of synthetic
polypropylene; it presents a high melting point (173e180 C) and a
glass transition temperature around 5 C. The main drawbacks of
PHB are that it is mechanically fragile and shows a narrow window
for the processing conditions due to the proximity of the melting
and degradation temperatures [1,2]. Different strategies have been
studied with the aim of improving its mechanical and thermal
properties, such as the preparation of nanocomposites with nano-
fillers [3,4] or the addition of another polymer to obtain blends [5].
Polymer blends represent an interesting strategy to adjust certain
properties of the polymers. However, it is generally very difficult to
improve a property without detriment of others. PLA appears as a
good alternative for blending with PHB.
PLA is a semi-crystalline polyester derived from lactic acid, obtained
entirely from renewable resources such as corn, sugar beet
and wheat. The glass transition temperature of PLA is in the range
of 50 Ce80 C while the melt temperature is in the range of
130 Ce180 C. It has greater mechanical strength and easier processability
than PHB. Although PLA is compatible with many current
processing techniques, the fact that it has a high glass
transition temperature leads to brittleness in the final products [6].
From this viewpoint, a good balance of amorphous and crystalline
domains (45e50%) along with low Tg (10 C) is an ideal target to
aim for. Therefore, a lowering of Tg and crystallization temperature
(Tc) as well as an increase in crystallinity are goals for improved in
PLA based materials. Changes in PLA packing structure to shift Tc
have been reported [6]. Conventionally, addition of a nucleating