Interpretation of Mechanical and Thermal
Properties of Heavy Duty Epoxy Based Floor
Coating Doped by Nanosilica
M.M. Alavi Nikje, M. Khanmohammadi, and A. Bagheri Garmarudi
*
Abstract. Epoxy-nano silica composites were prepared using Bisphenol-A epoxy
resin (Araldite® GY 6010) resin obtained from in situ polymerization or blending
method. SiO2 nanoparticles were pretreated by a silan based coupling agent. Surface treated nano silica was dispersed excellently by mechanical and ultrasonic
homogenizers. A dramatic increase in the interfacial area between fillers and
polymer can significantly improve the properties of the epoxy coating product
such as tensile, elongation, abrasion resistance, etc.
1 Introduction
Some of the main advantages of epoxy based coatings are thermal stability,
mechanical resistance, low density and minimal shrinkage. The main factor
influencing their performance is the molecular architecture [1-3]. Owing to their
densely cross-linked structure, they exhibit a number of superior qualities such as
high glass transition temperature, high modulus and high creep resistance.
Developments in the synthesis of nanoparticles have made it possible to process
nanocomposites [4,5]. Investigations have been reported during the past few years
for the development of the high-performance nanocomposites, which consist the
incorporation of a nanometer-size inorganic component into the organic resin
matrix. Industrial application of polymer–inorganic nanocomposites has attracted
a lot of interests during the last 5 years. The main reason is that nanocomposites
demonstrate combined properties of polymers e.g. flexibility, and also those of
inorganic chemicals e.g., rigidity, thermal stability, hardness, etc [6,7].
Application of epoxy compounds in a variety of products for construction industry
has been emerged since their properties, such as thermal stability, mechanical
response, low density and electrical resistance. Floor coating, humidity resistant
M.M. Alavi Nikje, M. Khanmohammadi, and A. Bagheri Garmarudi
Chemistry Department, Faculty of Science, IKIU, Qazvin, Iran
M.M. Alavi Nikje and A. Bagheri Garmarudi
Department of Chemistry & Polymer Laboratories, Engineering Research Institute,
Tehran, Iran
164
M.M. Alavi Nikje et al.
paints, polymer blended concrete and epoxy grout are some of the main products
applied in constructions. Molecular architecture, curing conditions and the ratio of
the epoxy: hardener are the main factors influencing the performance of these
chemicals.
2 Experimental
2.1 Sample Preparation
Bisphenol-A epoxy resin (Araldite® GY 6010) was from JANA Resin
Manufacturing Co. (epoxy value: 0.5208-0.5498 eq per 100 g; weight per epoxide:
182-192 g per eq; residual epichlorohydrin: below 100 ppm). Cycloaliphatic
polyamine (Aradur 43) from HUNTSMAN® Co. (amine value: 260-280 mg KOH
per g). The resin:hardener stoichiometric ratio was 100:60 pbw. Coupling agent is
γ-aminopropyltriethoxysilane (Amino A-100) manufactured by Silquest®
Chemicals which was added 5 pbw to the epoxy resin. Nano-SiO2 was AEROSIL®
200 with specific surface area of 200 m2g-1 and average particle size of 12 nm,
from Degussa. Water free acetone was from Merck®. One of the main issues in
preparation of nanocomposites is to disperse the nanoparticles in resin media
which has been reported to increase the resin’s viscosity. SiO2 nanoparticles were
pretreated by coupling agent in acetone. Using a “high shear” laboratory-mixing
device for mechanical mixing and an ultrasonic homogenizer, dispersion process
was conducted. Acetone content of the sample was removed by vacuum at 40 °C ,
homogenizing by ultrasonic apparatus. The hardener was added to the
formulation, being mixed and degasse. Cure process was in a chamber with room
temperature. Table 1 shows the content of nano silica in flooring samples
Table 1 Prepared nano SiO2–epoxy flooring samples
Flooring Sample
Nano Silica (%)
EP-0
0.0
EP-1
0.5
EP-2
1.0
EP-3
1.5
EP-4
2.0
EP-5
2.5
EP-6
3.0
2.2 Thermophysical Analysis
The tensile strength of cured flooring samples was determined, using an Instron
testing machine at a crosshead speed of 5 mm min-1 at room temperature,
according to ASTM D638. The thermomechanical properties of samples were
Interpretation of Mechanical and Thermal Properties of Heavy Duty Epoxy
165
investigated by a DuPont Instrument operating in the three-point bending mode
under nitrogen atmosphere. Data were collected in -20 to 200 °C temperature
range at a scanning rate of 5 °C min-1, using 10 Hz frequency. The friction
resistance test was performed by an abrasion machine. Hardness of flooring
samples was determined in Shore D scale. Thermal gravimetric analyzer and
scanning electron microscope were also utilized the characteristics of the nanocomposites.
3 Results and Discussion
It was observed that reinforcement of epoxy flooring by SiO2 nanoparticles would
dramatically improve the tensile properties of these coating. However
improvement from 3.22 MPa (EP-0) to 12.59 MPa (EP-5) is really excellent as
much more interfacial surfaces can be generated between polymer and
nanoparticles, which assists in absorbing the physical stress. Generally,
nanoparticles inherently possess high module and would strengthen the polymeric
matrix when dispersed in the nano scale level. The maximum tensile strength and
elongation was in EP-5 which would drop in EP-6 sample with higher amount of
SiO2 nanoparticles. There are several possible reasons for this decrement in tensile
strength. One would be the weak boundaries between nanoparticles and probable
micronized trapped bubbles. The other responsible reason may be the effect of
high amounts of nanoparticles on homogeneity in crosslinking of the epoxy
network. One of the main problems in floor coating by epoxy based materials is
the existence of expansion joints on concrete surface, which their dimensional
variations would cause the flooring to crack. The improvement in elongation at
break of flooring would result in higher resistance against concrete dimensional
variations. Interestingly the hardness and abrasion resistance of epoxy flooring
would be increased by addition of SiO2 nanoparticles (Table 2).
DMA experiments showed that δtan would decrease with addition of
nanoparticles while glass transition tempreature is vise versa. the Chemical
bonding at the interface of the nanoparticles and polymer matrix could lead to
hindered relaxational mobility in the polymer segments near the interface, which
Table 2 Physical properties of prepared nano silica - epoxy floor coating
Tensile Strength (MPa)
Standard Deviation (%)
Elongation
Abrasion
(%)
(mm3)
EP-0
3.22
1.8
5.94
490
EP-1
3.36
2.1
7.17
426
EP-2
5.08
1.7
6.99
416
EP-3
5.14
2.5
8.47
397
EP-4
8.72
2.8
14.29
368
EP-5
12.59
2.2
31.58
318
EP-6
11.19
2.1
33.04
256
166
M.M. Alavi Nikje et al.
leads to increase of Tg. The loss in the mobility of epoxy chain segments
according to nanoparticle: matrix interaction would result in restricted chain
mobility by improving the homogenized dispersion. Better dispersion would
reduce the distance between nanoparticles providing better interaction with each
other and also with epoxy matrix. In the other hand, dynamic modulus would be
benefited by relative hindering of epoxy structure motion (Figures 1 and 2).
Fig. 1 Variations in δtan of flooring samples
Fig. 2 Effect of nano SiO2 on glass transition temperature of epoxy flooring
Achieving a homogenous dispersion is considered as a difficult goal according
to their strong tendency in agglomeration. According to the SEM images form the
dispersion of silica nano particles in the epoxy flooring matrix, it is concluded that
good dispersion may occur by surface modification of the nanoparticles under an
appropriate processing condition. Of course the homogenizing steps (sonification
and high speed mechanical mixing) would be so effective [8]. Investigating the
breaking surface of nano composites, it was observed that nano silica would affect
the surface and breaking direction. As seen in figure 3, the breaking surface is
more homogenous and edge of separations are in a same direction in comparison
with neat flooring or low nano silica content samples.
Interpretation of Mechanical and Thermal Properties of Heavy Duty Epoxy
167
Fig. 3 SEM image of EP-0 (left) and EP-5 (right)
4 Conclusions
It was concluded that nano silica is industrially applicable in epoxy based coatings
for metal structures, factories, ships, and buildings. Nano silica particles fill up the
weak micro-regions of epoxy resin to boost the interaction forces at the polymer–
filler interfaces.
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