3. Introduction:
The problem of plastic packaging waste
Use of plastic –
a) European countries- 60kg/person/year
b) US - 80kg/person/year
c) India – 2kg/person/year
Basic material used in packaging include:-
a) paper b) paperboard
c) cellophane d) steel
e) glass f) wood
g) textiles h) plastics
5. Important properties - plastics
Strength and stiffness
Barrier to gases, Moisture & grease
Resistance to food components attack &
flexibility
Good processability
Good melt flow behaviour
Good thermal properties
Good optical properties i.e. should be
highly transparent (very imp for consumer)
Good sealability and printing properties
9. INTRODUCTION:
2 main groups of biodegradable plastics:-
a) polylactic acid (PLA)
b) starch based polymers
degradable but full degradability
will occur only when the pdts made from
these polymers are disposed off properly in
a composting site
10. Lactic acid
To replace conventional plastics with plant
derived alternatives by three approaches :-
Converting plant sugar into plastics
Producing plastic inside m.o
Growing plastic in corn & other crops
Sugar lactic acid polymerization polylactic
acid
11. Lactic acid can be produced by following
method:-
a) produced synthetically from hydrogen
cyanide & acetaldehyde
b) naturally from fermentation of sugar, by
Lacobacillus
13. Polylactic acid (PLA)
Behaves quite similarly as polyolefines
Converted to plastic by extrusion &
injection moulding
Drawbacks:-
a) high price of raw material
b) lack of composting
infrastructure
Polymers that are mostly selected for use :-
a) 90% L-lactide
b) 10% racemic D,L-lactide
14. Properties of these PLA:-
a) Readily polymerized
b) Easily meltprocessable
c) Easily oriented
d) Tg – 60oc
e) m.p temp. – 155oc
15. f) Tensile strength – 80-110 Mpa with
elongation at break of up to 30%
g) similar as polystyrene
h) used in direct food contact with aqueous,
acidic & fatty foods under 60oc &
aqueous & acidic drinks served under
90oc
19. Native Starch
Mostly used for industrially extracted starch
Inexpensive
Abundant product available from potato,
maize, wheat and tapioca
Starch means storing energy & found in :-
- granule form in seeds
- roots
- tubers
- stems, leaves & fruits of plant
Biodegradable in nature
20. 2 main components of starch are:-
a) Amylose (linear)
b) Amylopectin (branched) – largest
macromolecule & major component of
starch
23. Thermoplastic starch (TPS)
Also called destructurised starch
Homogeneous thermoplastic substance
Made from
native starch
swelling in a solvent
(plasticizer)
extrusion treatment
(kneading & heating)
Thermoplastic starch
Water & glycerol – used as plasticizers
25. Water resistance of starch based
products
TPS – common thermoplastic polymer
TPS shows – low permeability for oxygen
(TPS 43 cm3/m2/min/bar
LDPE 1880 cm3/m2/min/bar)
this makes it suitable for
packaging applications
High Permeability for water vapor & Quick
ageing - unsuitable
(4708 cm3/m2 compared to 0.7 cm3/m2 of LDPE)
26. Problem can be overcome by :-
a) blending (thermoplastic starch +
hydrophobic synthetic polymers)
b) by the production of more hydrophobic
TPS derivatives
Expensive
Mechanically instability
27. Polyhydroxyalkanoates (PHA)
Plant sugar fermentation polyhydroxyalkanoates
Are thermoplastic, water insoluble biopolymers
of alkanoic acids containing a hydroxyl
group+ a functional group to the carboxyl
group.
Approved as food contact material
Biodegradable in nature
28. Synthetic polyester
Formed by polycondensation of glycols and
dicarboxylic acids
Have tensile & tear strength comparable to
LDPE
Can be processed into blown or extruded
films, foams & injection moulded pdts
Used in refuse & compost bags , cosmetic &
beverage bottles
29. Used in combination with starch due to
their high price
For thermoplastic starch & polyester type
they show a decrease in water sensitivity
In case of thermoforming cannot provide
sufficient stiffness
30. Polycaprolactone
Made from synthetic sources
Limited use
Used in starch blends
because of low tg of -60oc &
melting temp. 60oc
31. polyvinylalcohol
water soluble
Prepared by the hydrolysis of
polyvinylacetate
Used for
- not used as food packaging
- agricultural chemicals
- dye & pigments
- water soluble laundry bags for
hospitals
- Detergent pouches
32. Developing novel biodegradable
materials
Major problem-Water Permeability
& Swelling Behaviour
Thermoplastic Starch
-Packaging Chips
-Packaging for Capsules
-Packaging for food products
Nano Composite Concept
33. Developing novel biodegradable
materials
1) Barrier effect of nano clay particles
in a biopolymer matrix
Incorporation of nano clay sheets into
biopolymers – large + effect on water
sensitivity & stability problems
+ effect make clay particles as barrier
element for oxygen & water
Increased mechanical properties
Increased long time stability
Reduction of ageing effect
34. 2) Extrusion
Starch & modified clay are mixed at a
temp. above the softening pt. of polymer
by polymer melt processing
At this temp. the polymer melt intercalates
Success of polymer intercalation depends
on:-
- Modification of clay
- Degree of increased interlayer distance
- Interaction between the modifier and the
matrix material
35. 3) properties of the starch – clay
nanocomposities
Decrease in hydrophilicity
Stiffness, the strength & the toughness –
improved & can be adjusted by varying the
water content
Clay will decrease the water permeability
Transparent & homogeneous film can be
formed
40. STARCH LOOSEFILL is comprised of various
starches (corn, wheat, and potato)
STARCH LOOSEFILL readily biodegrades in
compost heaps
Since it dissolves in water, you can sprinkle
it on you lawn and the rain will wash it into
the soil
Renewable
Better for the Environment