Environmental Engineering Reference
In-Depth Information
Table 1. Physical properties of PHA homopolymers
Young's
modulus
GPa
Tensile
strength
MPa
Extension
to break
percent
Plastic
Density
g/cm
Crystal
structure
Confor-
mation
Morph-
ology
Tg
°
C
Tm
°
C
poly(3HB),
amorphous
1.18
left-handed
21 helix
4
180
3.5
43
5
poly(3HB),
crystalline
ortho-
rhombic
1.26
lamellar
ultra-high M
w
poly(3HB)
lamellar 1.1
62
58
PP
400
3.2.2. Copolymers
. Random copolymers of (R)-3HB and (R)-3HV have been investigated
extensively with regard to various physical properties. In the case of random copolymers of
(R)-3HB with (R)-3HHX (3-hydroxyhexanoate), the repeat unit contains a propyl side chain
that strongly affects properties. Most notably, in solution-cast films, poly(3HB-co-3HHx)
becomes soft and flexible with increased proportion of (R)-3HHx, as shown by the
diminished Tm, Tg, crystallinity, and tensile strength, and by the increased elongation to
break factor (Table 2). An additional example is provided by poly(3HB-co-4HB), in which
crystallinity, elongation to break, and other physical properties can vary widely by adjusting
proportions of the component monomers (Table 2). These data show that PHA copolymer
properties, like those of other plastics, can be regulated by their composition; in addition, the
range of materials observed, from hard crystalline plastics to elastic rubbers, show that these
plastics hold great promise for a wide variety of applications.
Table 2. Physical properties of PHA copolymers
Plastic
non-BIB mole
fractionpercent
Tensile
strength
MPa
Elongation to
break
percent
Tm
°
C
Tg
°
C
Crystallinity
percent
poly(3HB-co-3HV)
a
various
50-70
poly(3HB-co-3HHx)
b
0
60
177
4
43
6
17
20
850
25
18
52
-4
poly(3HB-co-4HB)
c
0
60
43
5
16
26
444
49
14
64
17
100
104
a[46]
b
[47]
c
[27]
