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

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Poster Session, Thursday, June 17
Theme F686 - N1123
The Effect of Nanometer Size Mica Fillers on Mechanical Properties of Polyurethane
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UAysel Ersoy YilmazUP P*, Ayten KuntmanP Pand Bulent AydemirP
1
PDepartment of Electrical-Electronics Eng, Istanbul University, Istanbul 34380, Turkey
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PTubitak UME, National Metrology Institute, Gebze, Kocaeli 41470, Turkey
Abstract-In this study mechanical properties of nanometer size mica added polyurethanes were investigated experimentally. At first mica
particles at 1 nanometer size were prepared, and then polyurethane samples with different nanometer size mica concentrations were prepared.
Except 10 % mica filler concentrations the resulting nano composites compressive strength is increased.
Today in many engineering applications, more than one
class of materials is used together. At this point additives and
fillers gain extra importance due to their significant impact on
electrical, thermal, mechanical and environmental properties
of the resulting composite. Polyurethanes have a wide rage of
applications including coatings, adhesives, fibers, thermal
insulator, electrical insulators, etc. However they have some
disadvantages such as low mechanical strength, low thermal
stability, low electrical properties, etc. During the last decade
several studies has been done to improve these properties
using nano size particles [1-5].
In this study polyurethane nano composite with various mica
concentrations is studied. To investigate the change in
mechanical properties compressive strength tests were done
according to the ASTM D1621-04a standard.
In this study micas were modified with aminolauric acid and
the preparation procedure was briefly given. Biotite
(KMg2.5Fe2+0.5AlSi3O10(OH)1.75F0.25 ) which has a
density of 2,9 g/cm3 is used as mica filler. To a suspension of
aminolauric acid (8.61 g, 40 mmol) in 1,000 ml distilled
water, concentrated HCl (4.17 g, 40 mmol) was added. The
mixture was stirred at 80 C until getting a clear solution
indicating the formation of ammonium salt. To this solution, a
suspension of 20 g of mica in 1,000 ml of distilled water was
added with mechanical stirring at 80 C. The stirring was
continued over night. The resulted white precipitate was
collected by suction filtration. The precipitate was suspended
in hot distilled water with mechanical stirring for 1 h to
remove the adsorbed salts. This process was repeated several
times until no chloride ions were detected in the filtrate when
adding 0.1 M AgNO3. The precipitate was dried in a vented
oven at 60 oC for 3 days and then at 80 oC under 0.01 atm.
vacuum for 24 h.
All the polyurethane nano composite samples were prepared
under the same laboratory conditions. The desired weights of
polyurethane, mica and %0.01 Di butyltin dilaurate catalyst
was mixed for 5 minutes. Then the mixture was heated to 100
oC and 25% polymeric (methylenediphenylene diisocyanate)
MDI was added. The new blend was poured into the mould
and pressed for 10 minutes with the help of clamps. Mould
was placed in a degasser under high vacuum to remove any air
and potentially water vapor from the system. 24 h later the
mould was opened and the samples were cut in the dimensions
of 1mm by 50mm by 50mm. The highest content of mica in
polyurethane samples was limited to 10 % by weight for nano
fillers due to dispersion and processing problems.
The mechanical tests to determine compressive strength were
carried out on samples prepared according to the ASTM
D1621-04a standard. The experiments were carried out with a
Zwick tensile test machine at National Metrology Institute in
TUBITAK. For the compressive strength tests, the samples
were shaped into 12.3 mm diameter, 25.4 mm long cylinders.
The test parameters can be adjusted with TestXpert software.
Tests were performed at a speed of 1.00 mm/min. All tests
were performed at 23 C (room temperature).
Table 1. Compressive strength test results for 1 nm particle size
Material Type Compressive Strength (GPa)
Pure PU 9,056
PU+%1 11,426
PU+%3 11,600
PU+%5 9,541
PU+%10 7,816
The preparation of PU nanocomposite foams were described
in this study. Clay dispersion is affect by chemical process.
With the inclusion of 3% micas, nanocomposite show a
smaller cell size than pure polyurethane samples. Depending
on the chemical structure of polyurethane, as high as 28%
increase in compressive strength were observed in PU-mica
nanocomposite. However increasing the filler content to 10%
mica concentration opposite effect was observed in PU
nanocomposite 13.6% decrease in compressive strength were
observed. Preparation of polyurethane nanocomposite is a
complicated process where many factors could effect bubble
nucleation and bubble growth and in turn the compressive
strength. For applications in electrical insulators, compressive
strength is a very important property to calculate the mass of
cover material upon the bare cable conductor. According to
the results from this study cell size in polyurethane nano
composite is decreased and compressive strength is
remarkably increased at 3% mica addition. However detailed
mechanism on how nano size mica particles affect mechanical
properties of polyurethanes needs further investigation.
*Corresponding author: aersoy@istanbul.edu.tr
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6th Nanoscience and Nanotechnology Conference, zmir, 2010 729