Journal of Physical Science and Application 6 (1) (2016) 105-109
doi: 10.17265/2159-5348/2016.01.026
The Effect of Titanium Dioxide and Zinc Oxide Nanoparticles on Some Mechanical Properties of Epoxy Nanocomposites: A Comparative Study
Khalid R. Al-Rawi
Department of Physics, College of Science for Women, University of Baghdad, Baghdad, Iraq
Abstract: A new type of inorganic-polymer materials of epoxy Titanium Dioxide and Zinc Oxide was prepared. In this work, the mechanical properties of polymer composites reinforced with ceramic nanoparticles were investigated. Three points bending tests demonstrated an enhancement in flexural strength and flexural modulus respectively, compared to the pure epoxy. The reinforcement of nanoparticulate materials was Titanium Dioxide and Zinc Oxide with various weight fraction. Experimental tests results indicated that the composite materials have significantly higher modulus of elasticity than the matrix material. It was found that the enhancement in modulus of elasticity was directly proportional to the weight fraction of reinforcement material, and that Zinc Oxide composites have higher
modulus of elasticity than Titanium Dioxide composites with equivalent of weight fraction. The wear results showed that nanoparticles improved the wear resistance of epoxy nanocomposites, the Titanium Dioxide matrix particles could improve the wear resistance of the epoxy more efficiently than Zinc Oxide particles. The fatigue test showed that the fatigue resistance of epoxy Zinc Oxide matrix particles was higher than that of Titanium Dioxide matrix particles.
Keywords: Nanoparticles; epoxy; flexural strength; flexural modulus; Zinc Oxide(ZnO); Titanium Dioxide(TiO2); wear; fatigue; nanocomposites.
1. Introduction
In many studies were used inorganic particles in various polymers to improve tribological performance has been evaluated. It has been reported that smaller particles generally have better performance than larger particles to improve the tribological properties of polymers under sliding wear conditions [1]. In materials researches, the development of polymer nanocomposites is rapidly emerging as    a multidisciplinary research activity whose results could broaden the applications of polymers to the great benefit of many different industries,polymer nanocomposites (PNC) are polymers (thermoplastics, thermosets or elastomers) that have been reinforced with small quantities (less than5% by weight) of nano-sized [2]. High performance polymer composite
Corresponding author: Khalid R. Al-Rawi, Ph.D., research field: material physics. E-mail: ***********************.edu.iq.materials are used increasingly for engineering applications under hard working conditions. The important factors influencing their performance are the molecular architecture, curing conditions, the ratio of the epoxy resin and the curing agents [3]. The use of an additional phase, such as the inorganic fillers, to strengthen the properties of epoxy resins, has become a common practice [4]. Epoxy resin (EP) is a thermoset resin with good thermal and environmental stability, high strength and wear resistance [5]. Epoxy resins are used in a variety of applications since their properties, such as thermal stability, mechanical response, low density and electrical resistance can be varied considerably [4]. Particles smaller than tens of nanometers in primary particle diameter (nanoparticles) compared with their bulk material are of interest for the synthesis of new materials because of their low melting point, special optical properties, high catalytic activity, and unusual mechanical properties. There is a growing
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The Effect of Titanium Dioxide and Zinc Oxide Nanoparticles on Some Mechanical Properties of Epoxy
Nanocomposites: A Comparative Study
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interest in the development of nanocomposites consisting of organic polymers and (TiO2) or (SiO2) nanoparticles[5]. Organic-inorganic hybrid materials, especially polymer matrix composites with inorganic nanoscale building blocks, have drawn the widespread attention of researchers owing to the promise of combining the superior mechanical and thermal properties of inorganic phases with the flexibility and processibility of organic polymers [6]. The comprehensive performances of the composites depend on many factors, such as the intrinsic properties of the polymers, the processing technology of the composites, the dispersion of the nanoparticles in the polymer matrix, and the interfacial compatibility between nanoparticles and the polymer matrix. The recent investigation has shown that the epoxy/nanocomposites demonstrate some advantages in both mechanical and dielectric properties compared with pure resin system and epoxy with micrometer-size fillers at a lower loading concentration (1-10 wt%) [7]. Epoxy resins which are modified with inorganic particles, such as MnO, TiO2, SiO2, Al2O3, clay and so on have shown improved performances [8].
2. Experimental Work
Epoxy resin was a FOSROC Co. product (nitofill EP L-V), Jordon. The density of epoxy resin was 1.04 gm cm3. TiO2and ZnO nanoparticles (40 nm) were provided by NANOSHEL company, USA. Nano-TiO2 and Nano-ZnO were likely to agglomerate easily because of their high surface energy.
2.1 Preparation Procedure of Epoxy-nanocomposites
Epoxy/TiO2nanoparticles and Epoxy/ZnO nanoparticles with concentration (0%, 0. 05%, 0. 1%, 0.15%, 0.20% and 0.25%) were prepared respectively. The clay was dispersed in the epoxy by using a mechanical stirrer, and mixed for 45 min at 65°C and ultrasonic stirrer for 90 min. A mixture of EP/TiO2, EP/ZnO materials was degassed in vacuum at 90 °C for about 30min. The outcome mixture was then cast into a mold at room temperature.
2.2 Bending Test
Three points bending test have been used to investigate the mechanism of crack propagation. Instron 1122 was used and the cross head speed was fixed at (1mm/min). Load-deflection curves were obtained for different samples. The support span (distance between the supports) was depending on the specimen at the middle of support span for rectangular sample under a load in a three-point setup:
F.S = 3Pl/2bd2
E B = ML3/4bd3
F.S: Flexural strength “N/mm2”, E B: Flexural modulus “MPa”.
P: The applied load at the highest point of (load-deflection) curve “N”.
L: The span length “cm”, b: The width of test specimens “cm”.
d: The thickness of test specimens “cm”, M: The line of curve load-deflection
2.3Wearing Test
The sliding wear tests were carried out using an indenter-on-plate configuration as shown in Fig. 1. The diameter of the sliding track was 40 mm. The indenter was made of stainless steel with a diameter of 3.0 mm. The sliding tests were carried out with a load of 9 N, and the sliding speed of the counterpart had a fixed velocity. The testing time was 10 minutes. Mass loss was measured by differentiating the weight of the wear. After each wear test, the specimen’s weight loss, Δm, was weighed, so that the specific wear rate W S, can be calculated from:
L
f
m
Ws
∆
∆
=
.
.ρ
where f is the normal load applied to the specimen during sliding,ρ is the specimen density, and ΔL is the
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The Effect of Titanium Dioxide and Zinc Oxide Nanoparticles on Some Mechanical Properties of Epoxy Nanocomposites: A Comparative Study
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total sliding distance. At least, three specimens of each composition were measured.  2.4 Fatigue Test
The fatigue tests were performed according to ASTM-D3479 specimens using an HI-TECH LIMITED model No.: HSM 19, SER. No. E280 computer controlled loading frame. The applied load was sinusoidal with a frequency of 2 Hz, with 2 mm deflection a maximal load of 7 N and a stress factor of (R) 0. 2. Specimens were tested on room temperature.
Fig. 1  Schematic illustration of the sliding test.
All fatigue specimens were tested using the same machine. The machine cycles the specimens to failure and the number of cycles-to-failure was recorded by computer data acquisition system.
3. Results and Discussion
The FT-IR spectra of EPx, EP/TiO 2 and EP/ZnO nano composites material were illustrated in Fig. 2. From Fig. 2a it that the hydroxyl-stretching band of epoxy resin appears at 3433 cm −1, Fig. 2b (EP/TiO 2) illustrates that the absorption peak at 3494 cm -1 as well as Fig. 2c (EP/ZnO) shows the absorption peak at 3441 cm -1. The characteristic of –OH stretching, which is the unreactive TiOH and ZnOH groups in inorganic networks.
Fig. 2  FT-IR spectra of (a) EP, (b) EP/TiO 2
and (c) EP/ZnO nano composites material.
a
b
c
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The Effect of Titanium Dioxide and Zinc Oxide Nanoparticles on Some Mechanical Properties of Epoxy
Nanocomposites: A Comparative Study
108
This study, analyzed that the changes in terms of flexural strength curves and by adding nano ZnO, and nano TiO2 into the epoxy resin enhanced. The mixture of nano ZnO and nano TiO2enhanced the flexural strain which was used to study the changes induced by addition of nano filler. The flexural strength Fig. 3 and modulus Fig. 4 of composite material were clearly improved compared to the epoxy resin matrix. Flexural strength of EP/nano ZnO and EP/nano TiO2 nanocomposites increases with increasing volume fraction of nanoparticles, maximum increment at 0.5, 0.25wt% for ZnO, and 0.15 for
TiO2 nanocomposites are shown in Fig. 3. While the modulus strength increased the weight concentration of ZnO and TiO2 nano particles as shown in Fig. 4. Moreover, the higher value was at 0.25% of both nano particles, this behavior is due to decreasing in space distance between chains crosslink caused by adding nanoparticles which are polar particles, creating van der-waals bonding between chains and particles leads to an increase in constrained between; particles/polymer chains, and polymer chains itself [9]. Increasing the concentration of nano filler wt%, the nano composites clearly improve the flexural and modulus strength in comparison to pure epoxy. These results indicate that the rigid nano filler particles in epoxy networks directly enhance the stiffness of composites, allowing a uniform stress distribution in the polymer, and leading to increased flexural strength and modules strength. As the rigidity of nano filler particles is greater than that of epoxy resin, it can be expected that nano filler particles would improved the mechanical properties of the composites. Small sand particle with larger surface area achieve better wetting and adhesion which leads to better reinforcing ability and stiffer composite system [10, 11].
Fig. 5 shows the relationship between the wear loss of TiO2 and ZnO content of the epoxy (EP/TiO2 and EP/ZnO) composites. It can be seen that the wear loss decreases with the increasing of the nano filler contents. It is lower by about 90% than that of pure epoxy when TiO2 content is 0.15% and lower
by about 80% when ZnO is 0.2% content. This phenomenon indicates that, the improvement of wear resistance of epoxy on the one hand grafting polymers are able to increase the interfacial interaction between nanoparticle and matrix [12]. Wear resistance of the epoxy nanocomposites was greatly increased with the addition of small volume percents of zinc oxide nanoparticles [13].
The results of the fatigue tests are shown in Fig. 6 (S-N) curve with constant stress and constant deflection amplitude the fatigue life were plotted for nano filler concentration indicates that dependence of fatigue properties on maximum stress. Fatigue life results (number of cycles) versus TiO2and ZnO concentration shows that, fatigue life increases when the TiO2 and ZnO concentration increased respectively for two types nano fillers. However, the ZnO nano filler records more than four times TiO2epoxy nano composite at concentration 0. 25. This result supports the early theories developed to apply fracture mechanics concepts based on energy to fatigue resistance [14]. The improvement of the fatigue properties can be used constructively to increase the service life of components, or EP/TiO2and EP/ZnO components increase the fatigue life.
Fig. 3  The behavior of flexural strength vs. nano filler concentration.
concentration.
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The Effect of Titanium Dioxide and Zinc Oxide Nanoparticles on Some Mechanical Properties of Epoxy
Nanocomposites: A Comparative Study
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Fig. 5 The behavior of wearing weight loss (/gm) vs. nano filler concentration.
Fig. 6  The behavior of fatigue life(number of cycles) vs. nano filler concentration.
4. Conclusions
•By increasing the concentration of nano filler wt%, for nano composites clearly improve the flexural
and modulus strength in comparison to pure
epoxy. Flexural strain of the epoxy
nanocomposites is greatly increased by adding
small volume percents less than 0.25% of zinc
oxide nanoparticles and nanoparticles of TiO2. •Wear resistance of the epoxy nanocomposites is greatly increased with the addition of small
volume percents less than 0.25% of ZnO
nanoparticles and nanoparticles of TiO2. •Fatigue resistance of the epoxy nanocomposites is greatly increased with the addition of small
volume percents of TiO2 nanoparticles and it was
increased with the addition of zinc oxide
nanoparticles. References
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