properties available within this family are as a result very
broad. In general, PHAs can be divided into two main
groups, these being the short-chain-length PHAs (sclPHAs)
that contain monomer units with 3–5 carbon atoms,
and the medium-chain-length PHAs (mcl-PHAs) that
contain monomer units of 6–18 carbon atoms. The most
common PHAs are poly(3-hydroxybutyrate) (P3HB) and
poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (P(3HBco-3HV)).
These materials have mechanical properties that
are comparable to those of polypropylene and polyethylene,
although they have much lower elongation to break
and are more brittle.
There are a number of reviews of PHA polymers and
their crystallinity [9–26]. However, the effect of microstructure
and composition, and in particular the influence
of compositional distribution/blending, on mechanical
properties has not been a focus. This is addressed in this
review. Special attention is paid to higher HV content
copolymers (>20 mol% 3HV), the properties of which have
been infrequently reported. The fundamentals of PHA biochemistry
and crystallinity are given as a background,
with the scope of the review being summarized in Fig. 1.
It is believed that a clear understanding of the relationships
between PHA crystallinity and polymer composition,
compositional distribution, microstructure and blend composition
will help inform future polymer development
within this field.
properties available within this family are as a result verybroad. In general, PHAs can be divided into two maingroups, these being the short-chain-length PHAs (sclPHAs)that contain monomer units with 3–5 carbon atoms,and the medium-chain-length PHAs (mcl-PHAs) thatcontain monomer units of 6–18 carbon atoms. The mostcommon PHAs are poly(3-hydroxybutyrate) (P3HB) andpoly(3-hydroxybutyrate-co-3-hydroxyvalerate) (P(3HBco-3HV)).These materials have mechanical properties thatare comparable to those of polypropylene and polyethylene,although they have much lower elongation to breakand are more brittle.There are a number of reviews of PHA polymers andtheir crystallinity [9–26]. However, the effect of microstructureand composition, and in particular the influenceof compositional distribution/blending, on mechanicalproperties has not been a focus. This is addressed in thisreview. Special attention is paid to higher HV contentcopolymers (>20 mol% 3HV), the properties of which havebeen infrequently reported. The fundamentals of PHA biochemistryand crystallinity are given as a background,with the scope of the review being summarized in Fig. 1.It is believed that a clear understanding of the relationshipsbetween PHA crystallinity and polymer composition,compositional distribution, microstructure and blend compositionwill help inform future polymer developmentwithin this field.
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