Packaging materials as modified by nano materials

1. POLYMER NANO-COMPOSITES
FOR FOOD PACKAGING
Devinder Dhingra
CENTRAL INSTITUTE OF POST HARVEST
ENGINEERING AND TECHNOLOGY (ICAR)
LUDHIANA

2. Composite materials (or composites for
short) are engineered materials made
from two or more constituent materials
with significantly different physical or
chemical properties and which remain
separate and distinct on a macroscopic
level within the finished structure.

3. POLYMER NANO-COMPOSITES
• New class of materials
• Exhibit improved Mechanical, Thermal,
Electrical & Optical Properties
• Polymer Composites – prepared by micro /
macro particles such as talc, glass, carbon
fibres
• Polymer nano-composites – prepared by
dispersing inorganic or organic nano-
particles into polymers
• Nano-particles – Colloidal Silica, Nano-tubes,
Clay Platelets or Clay Minerals
• Higher Surface Area And Aspect Ratio

4. • Clay is a soil composed of hydrous aluminium
phyllosilicate minerals and has a particle size
that is typically defined as less than 2 μm in
diameter. Clay consists of a variety of
phyllosilicate minerals rich in silicon and
aluminium oxides and hydroxides which include
variable amounts of structural water.
• There are three or four main groups of clays:
kaolinite, montmorillonite-smectite, illite, and
chlorite.

5. CLAY MINERALS
• 2:1 TYPE (smectite family) Si Al Si
– MMT (N) layer charge negative
– Hectorite (N)
– Saponite (N)
– Laponite (S)
• 1:1 TYPE (layers made of Al Oct and Si Tetra)
– Kaolinite (N) layer charge neutral
• Layered silicic acid (layered silicon tetrahedron
sheets)
– Kanemite (N/S)
– Magadiite (N/S)

6. Characteristics of clay minerals
• Rich intercalation chemistry
• High strength and stiffness
• High aspect ratio of individual platelets
• Abundance in nature
• Low cost
– Thickness: 1 nm
– Aspect ratio: 100 – 1500
– Surface area: 700 –800 m2
/g

7. Surface modifications
• Hydrophilic clay - hydrophobic polymer
– Treatment – hydrophobic clay
– Organoclays
– Exchange the interlayer inorganic cations Na+
,
Ca2+
with ammonium cations
– Swell the interlayer space (>20 Angstrom)

8. How to make polymer nano-composites
• Produce nano-sized filler particles
• Methods to make nano-sized fillers
– Wet chemical processes: colloidal chemistry,
hydrothermal, sol-gel, precipitation methods
– Mechanical processing: grinding, milling, alloying
– Form-in-place method: lithography, PVD, CVD
– Gas-phase synthesis: flame pyrolysis, electro-
explosion, laser ablation etc.
• Modification of surface
• Dispersion into polymer matrix

9. Processing techniques
• Melt compounding method: polymer
pellets and nano-fillers are pressed
together in extruder / injection moulder
etc. and the molten material is blown into
films
• In-situ polymerisation: filler is added to
liquid monomer. e.g. Nylon 6 etc.
• Solution method: filler is added to polymer
solution using solvents (toluene,
chloroform, acetonitrile)

12. 1. Immiscible composite
– polymer chains are unable to insert
between (intercalate) the clay gallery
– phase separated composite similar to
conventional micro composite
2. Intercalated nanocomposite
– polymer chains are intercalated
between the clay layers
– alternating layers of polymer and
clay sheets
3. Exfoliated nanocomposite
– layered silicate sheets are
completely
and homogeneously dispersed in the
polymer matrix
– believed to achieve the highest
property improvements compared to
the other two

15. Nanocomposite Vs composite

16. Mechanical and thermal properties

17. Polymer type Layered clay Processing method
Thermoplastics
Nylon 6 MMT/Kaolinite In-situ polymerisation
polypropylene MMT In-situ, melt, solution
Polyethylene MMT In-situ, melt
HDPE MMT Solution exfoliation
Thermoset
Polyester MMT In-situ polymerisation
Polyurethane MMT In-situ polymerisation
Some selected polymer nano-composites
using structural polymers

18. Some commercial nano-clays
Product Applications Producer
Closite Enhance flexural and tensile
modulus and barrier properties
thermoplastics
Southern clay
products
Bentone Enhance mechanical and barrier
properties of thermosets and
thermoplastics
Elementis
Specialties
Plano Coatings Transparent packaging materials,
protective coatings, transparent
barrier coatings
TNO

19. Some commercial polymer nano-composites
Product Characteristics Applications Producer
Nylon nano-
composites
Improved
modulus,
strength, heat
distort
temperature,
barrier
properties
Packaging
(food, medical,
cosmetics,
electronics),
barrier films
Bayer,
Honeywell
polymer, RTP
company
M9TM
High barrier
properties
Juice or beer
bottles, multi-
layer films,
containers
Mitsubishi gas
chemical co.
AegisTM
OX Highly reduced
OTR, improved
clarity
High barrier
beer bottles
Honeywell
Polymer

20. Properties of nanocomposite films
• Enhanced mechanical properties
– Tensile strength 40%;
• Improved thermal stability
– (PMMA Nano-composite degraded at about 40-50
o
C higher than PMMA)
• Heat distortion temperature
– (HDT of Nylon 6: from 65 to 165 o
C)
• Better barrier properties against O2,N2 & CO2
• Reduction in WVTR
• Better barrier properties against alcohol,
toluene and chloroform
• Better optical properties
• Light weight

22. •Addition of nano-clays (~ 2-
5%) can provide desired
barrier & thermo-mechanical
properties.
• Can be achieved by orienting
platelets : strongly dependent
on the morphology and
processing.

27. • Replacement of metal layers
• Rigid plastic structures instead of glass
containers
• Recycling – reduction in packaging waste
• Biomedical and bioengineering fields
Nano-composites

28. Challenges and issues
• Modification of clay minerals
• Processing techniques
• Characterization of micro-structure
• Measurement of mechanical, thermal,
thermodynamic, and rheological
properties

29. Thank you