Modification of Polyolefins and selected natural polymers for improved properties in food packaging applications

The proposed work is aimed at the modification of polyolefins and selected
natural polymers for improved properties in food packaging applications. In
polyolefins, low density polyethylene was modified by blending with vanillin,
polypropylene was modified chemically with diisocyantes and PEO with starch.
In natural polymers, chitosan was modified by blending with glycerol, PEO and
by intercalation of nanoparticles. In addition, chitosan was chemically modified
with aldehydes (vanillin and 4-hydroxybenzaldehyde). All the chemically
modified and blended polymers were converted into films by extrusion
methods/solvent casting to characterize their physico-mechanical, optical, barrier,
thermal, morphological, food compatibility, antimicrobial and biodegradable
properties. The characterization was done using modern facilities like FTIR,
NMR, GC/MS, SEM, WAXS and modeling of moisture-sorption isotherms.
Blending of vanillin with LDPE improved its gas barrier properties and grease
resistance substantially. This film had potential for its aroma releasing capacity
for fatty foods. Chemical modified PP films with diisocyanates were better in gas
barrier and mechanical properties. The modified LDPE and PP films were also
ascertained for their compatibility in food packaging applications. Glycerol added
chitosan/PEO films showed improvement in its elongation significantly ensuring
the flexibility along with improvement in transparency of the films. WAXS
studies confirm the changes in the properties. Chitosan /PEO based films with
high WVTR increased their potential for use in fresh produce. Moisture-sorption
isotherm models such as Smith, Caurie, Bradley, and Oswin were found best
fitted in the range of water activity from 0.11-0.86. Chemical modification of
chitosan with aldehydes had improved its water barrier and tensile properties
significantly. The modified films were also found with effective antimicrobial
activity. Chitosan based nano composite films showed improved tensile strength
and water barrier properties along with excellent antifungal properties.
PEO/starch blended films have shown their potential use in the packaging of
fresh produce to control moisture evaporation. Smith model was found to be the
best fitted in the range of water activity from 0.11-0.86 of the films.