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PHB is a partially crystalline polymer that has material properties similar to
polypropylene (PP). Some of the essential physical properties of PHB are
summarized in Table 3, along with PP. According to Table 3, the strength parameters
(tensile strength, Young’s modulus) of PHB and PP are similar, and most physical
properties (crystallinity, melting temperature, and glass transition temperature (T g ))
are mostly the same with others fiber. However, there is a difference in toughness
(elongation at break). While the less ductile PHB breaks at 5%, the propylene
exceeds 400%. This property of PHB is improved by making copolymer with higher
PHAs, which reduces crystallinity [20]. Due to high crystallinity of PHB, it
undergoes thermal decomposition at its melting point. This makes its processing
very difficult and limits its commercial use. To improve properties of PHB, the
solution is to make its copolymer with higher PHAs such as PHBV. PHBV is less
brittle and less stiff than homopolymer PHB. The physical properties of PHB can be
modulated by changing the ratio of HB and HV during its synthesis [13, 16, 20].
4.4 Polyhydroxyvalerate (PHBV)
Polyhydroxy-butyrate-co-valerate (abbreviated as PHBV or PHBHV), also known
as ENMAT Y1000 (Helian Polymer), is a linear aliphatic polyester which is obtained
by the insertion of 3-hydroxyvalerate units to the PHB biopolymer [13, 16, 21–23].
PHBV is obtained by bacterial synthesis (R. eutropha) from non-genetically
Fig. 4 Structure of
optically active PHB
or P(3HB)
Fig. 5 Biosynthesis of PHB
M. A. Ali et al.
PHB is a partially crystalline polymer that has material properties similar to
polypropylene (PP). Some of the essential physical properties of PHB are
summarized in Table 3, along with PP. According to Table 3, the strength parameters
(tensile strength, Young’s modulus) of PHB and PP are similar, and most physical
properties (crystallinity, melting temperature, and glass transition temperature (T g ))
are mostly the same with others fiber. However, there is a difference in toughness
(elongation at break). While the less ductile PHB breaks at 5%, the propylene
exceeds 400%. This property of PHB is improved by making copolymer with higher
PHAs, which reduces crystallinity [20]. Due to high crystallinity of PHB, it
undergoes thermal decomposition at its melting point. This makes its processing
very difficult and limits its commercial use. To improve properties of PHB, the
solution is to make its copolymer with higher PHAs such as PHBV. PHBV is less
brittle and less stiff than homopolymer PHB. The physical properties of PHB can be
modulated by changing the ratio of HB and HV during its synthesis [13, 16, 20].
4.4 Polyhydroxyvalerate (PHBV)
Polyhydroxy-butyrate-co-valerate (abbreviated as PHBV or PHBHV), also known
as ENMAT Y1000 (Helian Polymer), is a linear aliphatic polyester which is obtained
by the insertion of 3-hydroxyvalerate units to the PHB biopolymer [13, 16, 21–23].
PHBV is obtained by bacterial synthesis (R. eutropha) from non-genetically
Fig. 4 Structure of
optically active PHB
or P(3HB)
Fig. 5 Biosynthesis of PHB
M. A. Ali et al.