Sandip.S.
Nandre*1, Atul.A.
Patil2, Umesh.B. Gawai,3 Sandip R. Patil 4
1Late
Annasaheb R.D.Deore Arts & Sci.College Mhasadi,Tal.-Sakri,Dist.Dhule
sandip.nandre11@gmail.com
2 SSVPSs
L.K.Dr.P.R.Ghogerey Science College Dhule, atul_patil2007@rediffmail.com
3
Late Annasaheb R.D.Deore Arts & Sci.College Mhasadi,Tal.-Sakri,Dist.Dhule,ubgawai@gmail.com
4
MGSM’s Dadasaheb Dr. S. G. Patil Arts and Sci. College Chopda, Dist. Jalgaon
Abstract:
Sodium Dodecyl Sulphate (DDS) intercalated
magnesium aluminium layered double hydroxide (Mg Al SDS LDHs) were synthesized
and used as additives for the preparation of epoxy nanocomposites. The
properties of the additives and their epoxy nano-composites were characterized
by X-ray diffractometer (XRD), SEM, UTM and TGA. The Mg-Al SDS LDH additions
into the epoxy resin, which was shown by a stable improvement of the thermal
properties of the nanocomposites as to comparison to virgin epoxy resin. Due to
the presence of Mg-Al SDS LDH, the epoxy nano-composites developed a rigid and
dense upper layer, with stable charring, which prevented the escape of the
decomposed flammable volatiles and protected the lower layer of the
nanocomposites from further decomposition. The mechanical strength of these
composites was also assessed. The strength of the composites was found to
increase linearly on increasing the Mg Al SDS LDHs content. An enhancement in
the properties was observed after toughening the epoxy resin.
Key words: Sodium
Dodecyl sulphate, X-ray diffractometer, Thermal and Mechanical Properties
I.
Introduction
Epoxy matrix are one of the most vital
types of thermosetting polymers resin and have extensively use as structural materials, structural
adhesives, and matrix resins for fiber reinforced nanocomposites. They are easily
breakable and have poor resistance to crack propagation. The toughness of bi-functional
epoxy matrix such as DGEBA has been increased by blending with many type
materials [1-4].
The investigated showed that the addition
of nano fillers into the epoxy matrix can significantly progress the mechanical
and thermal properties [5-6]. The reinforcement of epoxy polymer matrix by the
inorganic nanofillers such as Titanium dioxide (TiO2), Zinc Oxide
(ZnO), nano-clay, carbon nano-tubes, Carbon blacks and Calcium Carbonate (CaCO3)
were attracted to many research scholar and scientists. The addition of nano
fillers (particle size less than 100 nm) into the epoxy polymer matrix affects very
much to the properties of nano-composites due to their larger surface area and
the homogeneous dispersion within the macro molecules up to certain extent
[7-8]. However, one of the basic problems
associated with the nanofillers is the tendency to agglomerate during the
mixing with the polymer resin matrix [9]. This shortfall can be bridged by
prolong mechanical mixing and followed by ultra sonication of the nanofiller/resin
mixture [10].
Various literature survey focused on epoxy
nanocomposites such as Ng et al.[11] developed epoxy nano-composites containing
TiO2 and result shows that the toughness of the nanocomposites is
better than that traditional material filled epoxy composites. Wetzel et al.[12]
introduced two nanofiller like CaSiO3 and Al2O3
into epoxy resin matrix. They found nanoparticles can deviate and branch the
crack front or even pin it, forcing a higher energy absorption in the composite
when crack occurred. Chen et al. [13] reported the effect of CaCO3
concentration on the mechanical properties of blocked polyurethane/epoxy
interpenetrating polymer networks and they reported that mechanical properties
like tensile strength, flexural strength, tensile modulus, and flexural modulus
of IPNs improved with CaCO3 concentration to a utmost value at 5,
10, 20, and 25 phr, respectively. Wang et al. [14] developed epoxy
resin/CaCO3 composites by the methods of extruding, solution,
blending, as well as in situ and inclusion polymerization
In this paper study, the nanocomposites
were prepared by mechanical mixing of epoxy resins and Sodium Dodecyl Sulphate.
The effect of nano size of filler on the mechanical properties viz., tensile
strength, elongation-at-break, impact strength and hardness was studied.
II. Experimental
2.1
Materials
Epoxy resin was commercially available and
was used without any further purification (Pliogrip resin and Chemicals Pvt.
Ltd, Dombivali, Mumbai, (India)). Grade
PG-100; equivalent weight 182 eq/g; trade name: Resinova ; Viscosity: 9000-
12000cps. The Mg-Al based Layered Double Hydroxides and Sodium dodecyl
sulfate was obtain from Alderich Chemical Co.; Mumdai (India)
2.2 Preparation
of the Layered Double Hydroxides Sodium Dodecyl Dulfate (LDH-SDS)
LDH was calcined in a muffle furnace
at 440- 4500C for about 6 hr to alter it into metal oxide. The
calcined product (LDH) 38 g was dispersed in a 120 ml of aqueous solution
containing Sodium dodecyl sulfate (LDH-SDS) and the dispersion was
stirred by magnetic stirrer for 24 hr at room temperature at 250C.
The regenerated SDS intercalated LDH (LDH-SDS) was filtered out followed by
drying in oven at 100oC.
2.3 Preparation
of Epoxy Nanocomposites:
For Preparation of the Epoxy Mg-Al LDH-SDS Nanocomposites
system, the stoichiometric amount of Epoxy resin (27 g) was taken in beaker and
then different % of
LDH-SDS (1.0 to 5.0% with respective to epoxy resin) were added
into beaker and mechanically stirred at room temperature for 1.5 hrs at 300 rpm
and mixed thoroughly. Subsequently after through mixing of epoxy resin and LDH- SDS a
stoichiometric amount of the curing agent (9
g) was added in
each system and then again mechanically stirred at
room temperature for 15 min at 300 rpm. After through mixing of epoxy resin-LDH-SDS
and curing agent the viscous mixture was obtained, which were poured into flat
aluminium foil mould and cured at room temperature for 24 hrs. Then
sample plaque of cured product with different % LDH-SDS
content were obtained and will keep as such for further characterization.
Figure
1.Schematic representation for preparation
of epoxy nanocomposites.
Table
No. 1 Preparation of (epoxy/SDS-LDH) nanocomposites.
|
Sample Code |
Epoxy resin (g) |
Curing Reagent(g) |
Mg-Al SDS LDH (g) |
|
SAP-0 |
27 |
9 |
- |
|
SAP-1 |
27 |
9 |
0.27 |
|
SAP-2 |
27 |
9 |
0.54 |
|
SAP-3 |
27 |
9 |
0.83 |
|
SAP-4 |
27 |
9 |
1.08 |
|
SAP-5 |
27 |
9 |
1.35 |
III.
Characterization of Nano Composites
3.1 X-ray diffraction (XRD)
X-ray diffraction (XRD) pattern was
recorded on a Shimadzu SD-D1 diffractometer with Cu target (λ =1.54 Å). The d
spacing of the epoxy nanocomposites was analyzed by using Bragg’s equation (nλ
=2d sin θ).
3.2
Mechanical Properties
Determination of Tensile Strength, Elongation-at-
break and elastic modulus:
The Dumb-bell
shaped samples were prepared and was used for the determination of the tensile
strength, elongation-at-break and elastic modulus. The samples were prepared in
a self designed teflon mould as per ASTM D638 standardization.
3.3
Thermogravimetric Analysis (TGA)
Thermo-gravimetric analysis (TGA) was
carried out using a Shimadzu
Thermogravimetric Analyzer (TGA-50, Japan),
in the temperature range between room temperature and 8000C at a
heating rate of 100C per min in nitrogen atmosphere with a flow rate
of 50 mL/min. TG
traces were obtained by plotting per cent residual weight against temperature.
3.4 Morphological
Properties
The Scanning Electron Microscope (SEM)
images of the fractured surface of samples were obtained by using high
resolution and low vacuum SEM equipment (M/s FEI Company, USA; model: Quanta
200 FEG) to examine the microstructure and fractured surfaces of nano-
composites. The samples were mounted on aluminium stubs using carbon tape. The
samples were coated with a thin layer of platinum to prevent charging before
the observation by SEM.
IV.
Results and Discussions
4.1 X-ray
diffraction (XRD)
XRD
is a powerful technique for detect the exfoliation of SDS-LDH structures. Fig. 2 shows the XRD patterns of the SDS-LDH
/epoxy composites for distinct SDS-LDH content and dispersion agent [15].
Figure
2: X-ray diffraction patterns of various epoxy nanocomposites
Characteristic
maxima of SDS-LDH (2ϑ = 32° and 37°) are present in XRD
spectra of all epoxy/SDS-LDH systems indicating successful incorporation of SDS-LDH
into polymer matrix
(Fig. 2). On the other hand, the
disappearance of maxima at 7°,
11°, 20° and 23°,
which originate from the layered structure of the filler, indicate
intercalation and possibly exfoliation of SDS-LDH to form the epoxy nanocomposites.
4.2
Studies on Mechanical Properties
The results of tensile strength and
elongation-at-break are summarized in the Table
2 it is evidence from the results that the increase in loading of SDS-LDHs
in epoxy matrix increased both the tensile strength and elongation-at-break.
Table 2: Experimental data sheet
for mechanical properties of nano-composites
|
Sr. No |
Sample Code |
Tensile Strength in
Kg/cm2 |
Elongation at break (%) |
|
1 |
SAP-0 |
75.91
|
0.97 |
|
2 |
SAP-1 |
78.52
|
1.27 |
|
3 |
SAP-2 |
84.36
|
1.46 |
|
4 |
SAP-3 |
89.82
|
1.67 |
|
5 |
SAP-4 |
90.94
|
1.99 |
|
6 |
SAP-5 |
95.21 |
2.37 |
Figure 3[a-b]: Variation of tensile strength
and elongation-at-break with percentage loading of SDS-LDHs in epoxy matrix.
The values of tensile strength and
elongation-at-break was found to be greatest in 5 wt% (SAP-5) SDS-LDHs loaded nanocomposite sample. The enhance of
tensile strength and elongation-at-break might be due to the filling of SDS-LDHs
into the amorphous region of matrix via uniform scattering up to 5 wt% (SAP-5)[16,17]. When the amorphous
region of epoxy polymer matrix had been completely filled by the nano
particles, the sample achieved highest tensile strength due to the load
shearing by SDS-LDHs. The nanocomposite samples also showed the toughening
behavior on addition of nano-filler for same composition, which led to enhance
the elongation-at-break values.
4.3.
Thermal stability.
The thermal stabilities of the Epoxy/SDS-LDH
nanocomposites were studied by means of TGA. The TGA thermograms for the virgin
epoxy resin and Epoxy/SDS LDH nanocomposites are shown in Fig 4:
Figure
4: TGA thermograms of
Epoxy/SDS-LDH nanocomposites as a function of SDS- LDH content.
The thermal stability of the
nanocomposites was significantly enhanced by the addition of SDS-LDH. In the
virgin epoxy system, the degradation started at around 290oC. When
SDS-LDH was added to the epoxy matrix, the IDT of the nanocomposites was at
least 20oC higher than that of the virgin epoxy system. The Tmax
of the virgin epoxy system was 370oC, whereas upon addition of
SDS-LDH into the epoxy matrix, the Tmax of the nanocomposites appeared
within the range of 400-410oC. These results can be interpreted with
reference to the addition of SDS-LDH to the epoxy polymeric matrix system[18,19],
which increased the surface contact area between the SDS-LDH particles and the
epoxy matrix, which in turn prevented the heat diffusion during decomposition
of the Epoxy/SDS LDH nanocomposites. The results can be attributed also to the
increased cross-linking density of the nanocomposites. The char content for the
nanocomposites at 800oC also was increased with the addition of
SDS-LDH. A similar observation was reported by Chen et al. using rigid
poly(vinyl chloride)/calcium carbonate nanocomposites.
4. 4
Morphological Studies
Figure
5: SEM image of samples SAP-0, EPC-1, SAP-3, and SAP-5 respectively.
Surface
morphology of epoxy/SDS-LDHs nanocomposites was further studied by the SEM
analysis (Figure 5). With smaller magnification (Figure 3a) it can be seen that
SDS-LDHs is consistently dispersed within the epoxy matrix. Larger
magnification confirms intercalation of epoxy matrix within layered structure
of LDH-B, but no complete exfoliation in any of the nanocomposites[20,21]. Only
nanocomposite with 5 % of nanofiller shows partial exfoliation.
V.
Conclusions
The following conclusions can be drawn:-
1) As
the concentration of Sodium Dodecyl Sulphate double hydroxide (Mg-Al SDS-LDHs)
increased in the nanocomposite samples,
the tensile strength, elongation-at-break, increased and found maximum in SAP-5
sample. The enhancement in the mechanical properties of nanocomposite samples
were because load sharing by nano-particles, when subjected under load.
2) The
high degree of intercalation of nano-particles was observed in SAP-5 sample
than other nanocomposites, which showed the higher roughness and surface area
to divert the crack initiation and propagation.
3) As
the concentration of Sodium Dodecyl Sulphate Layered double hydroxides (Mg-Al
SDS-LDHs) increased into the nanocomposite samples ,the thermal properties also
increase and found maximum in SAP-5 sample. The enhancement in the thermal
properties of nanocomposite samples thus increasing the surface contact area
between the SDS-LDHs particles and the epoxy matrix.
VI
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