Third Day Poster Session, 17 June 2010 - NanoTR-VI

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Poster Session, Thursday, June 17
Preparation and Characterization of Poly (3-Hydroxybutyrate) Homo and Copolymers
Nanocomposite Films
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Onur GökbulutP P, Burcu KayaP P, Okan AknP Pand UFunda TihminliogluUP P*
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PDepartment of Chemical Engineering, zmir Institute of Technology, Urla, 35430, Turkey
Theme F686 - N1123
Abstract- This study aims to prepare and investigate the characteristic properties of Poly (hydroxybutyrate) (PHB) and
polyhydroxybutyrate-co valerate (PHB/HV) copolymers layered silicate nanocomposites. Nanocomposites were prepared via melt
intercalation method by dispersing orgonamodified layered silicate nanoclays. The effects of clay loading and the polymer type on the water
vapour, OR2R COR2R barrier properties were measured. In addition, Differential Scanning Calorimetry (DSC) and mechanical properties of
the films were performed. Mechanical properties of the chitosan composites were enhanced with the addition of clay . The enhancement in
the barrier properties were obtained upto certain clay content in composites.
Among many different materials that mankind is dependent
on plastics are the most important ones considering their
widespread usage in food packaging, textile, communication,
transportation, construction, medical industries. Currently,
plastics and synthetic polymers are mainly produced using
petrochemical materials that cannot be decomposed. In
addition the amount of plastic waste increases every year.
Therefore in the last decades there has been a significant
increase in the development of biodegradable thermoplastic
polyesters due to ongoing concerns about the disposal of
conventional plastics and the increasing difficulty in
managing solid wastes.
Poly (hydroxyalkanoates), PHAs, comprise a family of
biopolymers that has attracted much attention recently due to
similar properties to conventional materials such as
polypropylene, polyethylene, polystyrene, and PET. Bacterial
biopolymers such as Poly (3-hydroxybutyrate) (PHB) and its
copolymers with valerate (PHB/HV) are biodegradable
thermoplastic polyesters and one of the most widely
investigated members of the family of PHAs. PHB and its
copolymers present good mechanical, thermal and barrier
properties. PHB is a partially crystalline thermoplastic and
has a high melting temperature. However PHB suffers from
low melting stability, brittleness and lack of transparency [1].
Thus, recent studies are objected to improve the properties of
PHB and its copolymers by addition of nanoclays. Surface
modified clays have been studied as advanced additives to
improve or balance thermal, mechanical, fire resistance,
surface, or conductivity properties of nanocomposite due to
their high surface to volume ratios and the subsequent
intimate contact that they promote with the matrix at low
filler additions [2]. In essence, three different methods are
used to synthesize polymer-clay nanocomposite; melt
intercalation, solution and situ polymerization.
PHB and PHB-HV /layered silicate nanocomposites in the
present study are prepared via melt extrusion. Natural PHB
and its copolymer PHB-HV (2% and 12%) were purchased
from Goodfellow Inc. and dried under vacuum at 80°C for
two days before use. As clay, organophilic surface modified
montmorillonite called Cloisite® 15A purchased from
Southern Clay Products, Inc. Polymers and nanoclay are
melted extruded by using a Thermofisher twin screw extruder
with varying weight percentages of clay at a temperature of
180 °C and a screw speed of 50 rpm. The extruded
composites are dried under vacuum at 50 °C. The samples of
PHB, PHB-HV and their nanocomposite are finally
transformed into films by compression molding in a hot-plate
o
hydraulic press at 175 P PC and 5 Metric tons of pressure
during 5 min. The polymer sheets are cooed to room
temperature under constant pressure.
The effect of filler concentration on the water vapor, OR2R
and COR2 Rpermeability, mechanical and thermal properties of
the composite films were evaluated. The structure of
nanocomposites and the state of intercalation of the clay were
characterized by Phillips X’Pert Pro MRD with Cu K
radiation (=1.54 nm) under a voltage of 40 kV and a current
of 40 mA. Samples were scanned over the range of
diffraction angle 2 = 0.25-30°. Thermal properties of the
polymer and the nanocomposite films are studied by a DSC
technique with a Shimadzu Calorimeter at a heating rate 10
o
P/min. Morphology of polymers and their nano composites
are analyzed by XRD and TEM. As a result of morphogical
analyses , intercalated structure were obtained . The extent of
intercalation depends on the amount of silicate and the nature
of organic modifier present in the layered silicate .
According to results of permeability measurements; the
nanocomposite films exhibit good barrier properties as
compared to their unfilled polymer films. The water vapor
and gas permeability values of the composite films decreased
significantly depending on the filler concentration and the
type of filler used. The decrease in water vapor and gas
permeability of PHB and PHB-HV- clay nanocomposite
films are believed to be due to the presence of ordered
dispersed clay nanoparticle layers with large aspect ratios in
the polymer matrix. This causes an increase in effective path
length for diffusion of water vapour and gas into polymer
matrix.
*Corresponding author: HTfundatihminlioglu@iyte.edu.trT
[1] M. D. Sanchez-Garcia ; E. Gimenez ; J. M. Lagaron ,
Morphology and Barrier Properties of Nanobiocomposites of
Poly(3-hydroxybutyrate) and Layered Silicates Wiley InterScience
2008 , DOI 10.1002/app.27622
[2] Reguera, J.; Lagaron, J. M.; Alonso, M.; Reboto, V.; Calvo, B.;
Rodriguez-Cabello, J. C. Macromolecules 2003, 36, 8470.
[3] Cabedo L.; Plackett D.;Gimenez E.; Lagaron J.M., Studying the
Degradation of Polyhydroxybutyrate-covalerate during Processing
with Clay-Based Nanofillers Received 31 March 2008; accepted 22
September 2009, DOI 10.1002/app.29945
[4] Pralay Maiti, Carl A. Batt, and Emmanuel P. Giannelis, New
Biodegradable Polyhydroxybutyrate/Layered Silicate
Nanocomposites , Biomacromolecules 2007, 8, 3393-3400
6th Nanoscience and Nanotechnology Conference, zmir, 2010 734