Yuhana, Nor Yuliana
(2002)
Barrier Properties and Thermal Stability of Polymer Blend
and Polymer-Silicate Nanocomposite
(High Density Polyethylene & Polyamide).
Masters thesis, Universiti Teknologi Petronas.
Abstract
The present work attempts to obtain better understanding on the barrier properties and
thermal stability of polymer blend and polymer-silicate nanocomposite. Barrier property
to hydrocarbon (Toluene), gases (Oxygen) and water have been done on HDPE, PA 66
and PA 6 polymers, for their blends and nanocomposite (Cloisite 30B and Nanomer 1.30
TC). Also the thermal stability of polymeric nanocomposite, P A 6 and HDPE with
Nanomer 1.30TC have been analysed to see the change in thermal decomposition,
compare to pure polymer.
Blending of two polymers HDPE/P A (80:20 % wt) shows changing in barrier property of
polymer matrix HDPE, while it still has a dominant effect on the property. Addition of
compatibilizer (MPE) to the blend would homogeneously disperse the PA particles in the
matrix, and resulting and improved barrier property to hydrocarbon than that of pure
HDPE, i.e. Toluene permeability in the blend of HDPE/P A 66 in the absence of
compatibilizer is reduced by 2 times, and in the presence of compatibilizer, the
permeability is reduced by 6 times.
Different type of polymer-silicate nanocomposite processing does give influence on the
composite performance i.e. delamination and dispersion of clays in the polymer matrix.
PA 66 nanocomposite (Cloisite 30B) 5%wt is prepared by two different method of
processing: (A) slit-die twin-screw extrusion and (B) slit-die twin screw extrusion,
followed by compression molding. The barrier property of P A 66 nanocomposite
produced by type (B) process shows an improved in barrier property to oxygen than that
of pure P A 66, i.e. Oxygen permeability in the P A 66 nanocomposite is reduced by 2
times for processing type (A) and reduced to about 3 times for processing type (B).
Besides processing type and condition, the choice of clays for polymer are also important
for achieving good delamination and dispersion i.e. barrier property of P A against water
are reduced gradually by increasing the amount of Cloisite 30B in the composite.
However for HDPE, with the Cloisite 30B, the opposite trend was observed.
The thermal stability of polymer silicate-nanocomposite could be influenced by two
factors: thermal stability of onium ion and clay loading. At higher clay loading (10% wt),
it is observed that polymer thermal degradation start at higher temperature compare to
that of pure polymer.
4 permeability models are used to compare the selected experimental results for Toluene
and Oxygen Experiment: Series and Maxwell for blend system, Cussler and Bharadwaj
for polymer-silicate nanocomposite. It could be observed that for HDPE/P A 66 blend, in
the presence of compatibilizer, Series Model give the closer value to the experimental
result. Bharadwaj model tracks very well the experimental result for P A 66
nanocomposite, the model predict the permeability by considering the orientational order
of clays in the polymer.
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