Polyhydroxyalkanoates:
Various properties,
Various applications
Filip Jedra; KCPK, Arnhem; May 8th, 2014
PHAs overview
•
Polyhydroxyalkanoates (PHAs) form a large group of linear, aliphatic polyesters
that can be obtained from renewable resources. These substances become more
and more popular as a alternative plastic material due to their biodegradability,
processability and increasing number of present and potential applications.
R=H, -CH3 , -C 2H5 , -C 3H7 ,-C 4H9 , -C 5H11
n=100 - 30000
Fig. 1. general scheme of PHA macromolecule structure
sheet 2
Which polymers belong to PHAs?
•
Several out of numerous substances from PHAs family have been produced to a
relatively high concentration with high productivity. [poly(3-hydroxybutyrate) PHB, poly (3-hydroxybutyrate-co-3-hydroxyvalerate) – PHBV, poly(4hydroxybutyrate) - P(4HB) and its copolymers]
•
First two of these substances have drawn so much attention in terms of their
potential applications in packaging industry. PHB is a homopolymer originally
made of glucose in bacteria cells. But production of PHBV copolymer is possible if
both, glucose and propionic acid are available for microorganisms growth.
sheet 3
Why else do they attract attention of manufacturers?
•
At the end of 20th century, the average cost of a kilogram of PHAs was 15-16 times
greater than a kilogram of PE or PP. In order to reduce the overall cost, it is
important to produce PHAs with high productivity and high yield, taking also the
alternative production pathways under concideration.
•
Currently, the cost of polyolefins clearly exceeds
1€/kg while the cost of a kilogram of PHAs is close to 4€.
Well, the prices of PHAs and polyolefins
are getting closer to each other !
sheet 4
Physical properties
•
The materials properties exhibited by PHAs, ranging from stiff, brittle to semi
rubber-like makes it a close substitute for the synthetic plastic and gives wide
range of final products.
•
PHB has better oxygen barrier properties than both PP and PET, better water
vapor barrier properties than PP, and fat and odor barrier properties that are
sufficient for use in food packaging.
sheet 5
Physical properties
Property
PHB
PP
Melting point. °C
170-175
160-176
Thermal decomposition °C
210-215
> 330
Crystallinity. %
70-80
80
Molecular weight. daltons
5x 105
2x 105
Glass transition temperature. °C
15
-10
Density. glcm3
1,25
0.905
Tensile strength. MPa
40
38
Extension to break. %
8
400
UV resistance
good
poor
Fig. 2. Physical properties of polyhydroxybutyrate (PHB) compared to polypropylene (PP)
sheet 6
Physical properties
HV content. mol %
Property
0
10
20
Melting point. °C
180
140
130
Crystallinity. %
80
60
35
Extension to break, %
8
20
50
Fig. 3. Physical properties of polyhydroxybutyrate-co-valerate (PHBV)
lower brittleness and stiffness,
wider processing window,
greater applicability
sheet 7
Processing
•
PHB and PHBV polymers can be manufactured by means of processing lines used
for production of goods made of commercial, synthetic polymer materials, such
as polyolefins or PET. That creates possibility of obtaing various products by cast
(sheet) extrusion, blown
film extrusion as well
as injection molding
and thermoforming.
sheet 8
Various routes of applications
sheet 9
It all started from….
The first
commercial use of
PHA was a
shampoo bottle. It
was made of PHBV
copolymer sold by
the name of Biopol
It was introduced to
the market by ICI,
but then it passed
through a few
companies to finally
end up in Metabolix
Currently there are
also several other
producers of PHB
and PHBV:
Shenzen Ecomann
Biotechnology,
Biomer, Meredian
And some of the best known brands are…
sheet 10
And why is PHBV relevant for paper/board industry?
flat films:
combined
packaging forms,
one part is paper
based, the other
one is made of
bioplastic - PHBV
coatings: there
are suitable
grades with
approperiate
adhesion to
paper, application
example: hot
drink cups
laminates: glue
lamination,
multilayer
structures with
pre-coated paper
and…
sheet 11
And why is PHBV relevant for paper/board industry?
blends with: poly(lactic acid) - PLA,
poly(butylene succinate) - PBS,
polybutyrate adipate terephthalate - PBAT
or thermoplastic starch – TPS. It provides a
good ability of obtaining various products
with different functional properties.
For instance, blending PHBV with PLA will
lead to improving optical properties
(increasing gloss, decreasing haze). This
blend might find its use in combined
packaging system, where bioplastic-based
element is supposed to be transparent to
provide visibility of the product.
sheet 12
Potential applications in paper-based materials
Novel blends and composite materials:
• PHA as a carrier for active compounds?
PHA’s presence in pulp:
• fibres reinforced with elastic substances are
well known in clothing industry, why not to
reinforce cellulose fibres?
???
Let’s discuss what else might fit in here
sheet 13
Thank you for your
attention!
Filip Jedra, PhD
Bumaga BV – Kennis in Productie
[email protected]