**Abstract**

The tribological and mechanical properties of organomodified montmorillonite (oMMT)-incorporated Epoxy (Epoxy-oMMT), vinyl ester (vinyl ester-oMMT) and titanium dioxide (TiO2)-filled Epoxy (Epoxy-TiO2) nanocomposites are discussed below. Implications of introducing oMMT and TiO2 nanoparticles on mechanical and dry sliding wear properties are presented using micrographs of cast samples and through observations of wear affected surface of nanocomposites. Distribution of nanoparticles and their influence on properties are being emphasized for understanding the wear properties. The data on mechanical and tribological properties determined experimentally are compared with published literature. The main focus is to highlight the importance of nanofillers in the design of wear-resistant thermoset polymer composites. A detailed study of strength and moduli of Epoxy-oMMT, Epoxy-TiO2 and vinyl ester-oMMT nanocomposites was taken up as a part of the investigation. A discussion on density, hardness, tensile, flexural test data, and friction and wear of nanocomposites and analysis of results by comparison with prevalent theoretical models and published results of experiments are presented.

**Keywords:** organomodified montmorillonite, titanium dioxide, tribological properties friction and wear d wear resistant

## **1. Introduction**

The present day scenario is attracting the polymer nanocomposites with greater interest both in industry and academics because of significant improvement in the properties when compared to base matrix or traditional composites [1]. The important structural characteristics which give unique properties to nanocomposites are the nanosize and a huge interfacial surface area of the nanofillers.

Since 1980s, advantageous properties of polymer nanocomposites were realized at the Toyota research laboratories where they studied nylon-6 based composite system with nanoclay as the reinforcement material to improve the toughness and heat resistance of nylon-6 [2]. Since then, a large quantity of research work has been carried out on polymer composites system using nanoclays and nanoparticle fillers of metallic or nonmetallic type and remarkable enhancements and benefits in several properties have been reported. The intriguing fact is that the properties which were observed in nanocomposites were never anticipated.

Although, the broad group of nanocomposite polymer materials have been widely investigated and fairly understood, the development of thermoset polymer based nanocomposites which also belong to this group, still remains a challenge. This is mainly because of the difficulty in uniform dispersion of nanofiller particles in the thermoset polymer matrix.

Many studies shown improvements in the mechanical strength and modulus of nanoclay filled epoxy resin nanocomposites as compared to the Epoxy resin [3]. Wang and co-authors [4] reported another technique called unique "slurry compounding" to fabricated exfoliated nanoclay-Ethacure nanocomposites. This composites shows improvements in the modulus of epoxy resin by about 40% with 5 wt.% of nanoclay, but with decreased tensile strength. They attributed this partial achievement to the feeble surface interface and occurrence of air foam in the nanocomposite samples. Gefu and co-authors [5] studied vinyl ester with 1 wt.% nanoclay. They have compared five types of mixing combinations such as (i) 30 min manual stirring, (ii) 30 min manual stirring and 1 h sonification mixing, (iii) 30 min manual stirring and 1 h sonification mixing followed by three-roll mill shear mixing, (iv) 30 min manual stirring and 1 h sonification mixing followed by three-roll mill shear mixing and 1 h sonification mixing, and (v) 30 min manual stirring and 1 h sonification mixing followed by three-roll mill shear mixing with 1 h sonification mixing and three-roll mill shear mixing while holding other factors constant.

It could be generally concluded that intensive mixing improved exfoliation until a certain point (defined as optimum point) and then its positive effects diminish with further mixing efforts. Considering reduced mixing effort of method iv, it is being recommended. Kotsilkova and co-authors [6] studied the flexural strength and flexural modulus of epoxy-clay nanocomposites fabricated by direct method or without solvent method and indirect method or solvent processing techniques. Different organic modifiers were used to functionalize the clay. It has been observed that the mechanical properties are majorly dependent on nanocomposite structure and the type of solvent used. The fabricated samples by direct processing method or without using solvent technique showed increased flexural modulus. The modulus of the nanocomposites at 5 volume percentage of clay content increased significantly.

In compare, the flexural modulus of fabricated nanocomposites fabricated by adding solvent or solvent processing technique is not affected [7]. The flexural strength of the fabricated nanocomposites has increased when compared to the samples fabricated by the direct processing method or without using solvent. This is due to the strength of the solvent, acting as a plasticizer for the base resin and alters the interfacial adhesions. In earlier studies it is reported that nanoclay appears to have either the intercalated structure or the partially exfoliated structure. The maximum improvement achieved in the modulus was of the order of about 80% with 10 wt.% nanoclay [7].

While the addition of nanoclay to epoxy resin generally increases the tensile modulus, it decreases the tensile strength and fracture strain [8, 9]. This was mainly attributed to the agglomeration of nanoclay and presence of voids. Organically modified nanocly effect on the physical, structural properties of organically modified clay –epoxy nanocomposites samples was examined by Dean and co-authors [10]. They reported that different morphological structures such as intercalation, partial and full exfoliation of nanoclay. The degree of intercalation morphology varies and interlayer expansion was observed. This is related to the mechanical properties of the fabricated nanocomposite samples. With the increase in the clay content, 35% increase in tensile modulus for the 2 wt.% sample, 15% increase in tensile modulus for 4 wt.% sample and 30% increase in the tensile modulus for the sample with 6 wt.% respectively.

**197**

interactions.

*Mechanical and Tribological Properties of Epoxy Nano Composites for High Voltage Applications*

From the above studies, it was found that the mechanical properties such as flexural and tensile strength reduce for the fabricated nanocomposite samples with surface modified and not modified clay when compared to pristine base matrix. This is mainly due to the creation of voids, feeble adhesion points along the fillermatrix surface interface during nanocomposite processing. Velmurugan and Mohan [14] have reported the presence and effect of quaternary ammonium modified montmorillonite clay content on the mechanical properties of clay-epoxy nanocomposites. They reported that the tensile modulus of the fabricated samples increased about three times when compared to base pristine epoxy with the accumulation of 10 wt.% surface modified clay. This is due to the fact that the exfoliation structure of clay layers and surface interfacial adhesion between the nanoclay and the epoxy matrix, whereas, the tensile strength reduced in spite of the content of the clay as

Yasmin and co-authors [15] conducted studies on the mechanical characteristics

Basara and co-authors [16] analyzed the presence and effect of clay substance and morphological structure on mechanical properties of nanocomposites. The organically surface modified (Cloisite 30B) and natural or unmodified (Cloisite Na+) clay with the content varying from 0.5 to 11 wt.% was reinforced into base epoxy matrix and observed that tensile modulus increased with clay content. This is attributed to stiffening effect of montmorillonite clay in two types of clay reinforced nanocomposites. Cloisite 30B and Cloisite Na+ reinforced nanocomposite samples showed utmost tensile strength at 1 and 0.5 wt.% respectively. The reason for the decrease in tensile strength at larger montmorillonite clay content is due to the stress concentration effect of the agglomerated clay particles and lesser surface

of surface modified montmorillonite clay added epoxy nanocomposite samples with variation in concentration of clay from 1 to10 wt.% fabricated by shear mixing technique. Based on their report, the addition of surface modified nanoclay particles there is a significant improvement both in elastic and storage modulus of base epoxy resin. In addition, there is an increase in storage modulus with increasing in clay content. This was ascribed to intercalation or exfoliation structure of surface modified nanocly (Cloisite 30B) in base epoxy matrix. The results reconfirmed that there is a direct relation between the degree of intercalation or exfoliation and the

mechanical properties of the fabricated nanocomposites samples.

Isık and co-authors [11] reported the clay loading effect on the tensile strength of organically modified clay filled epoxy nanocomposites. The tensile strength decreases with increasing content of clay. This is due to the nonuniform dispersion of clay, agglomeration of clay causes stress concentration and decreased polymer clay interactions. They also observed that the tensile modulus of the nanocomposite increases with increasing amount of clay. The mechanical properties of montmorillonite filled epoxy nanocomposites were studied by Akbari and Bagheri [12]. They found a decrease in flexural strength with increasing the content of organically modified clay and this is due to the fact that intercalated structure of clay in the nanocomposites. Kaya and co-authors [13] analyzed the flexural and tensile properties of clay filled epoxy nanocomposite samples. The surface modified and unmodified montmorillonite clay were added to the epoxy matrix with increasing clay contents from 1 to 10 wt.%. The author presented that both tensile and flexural modulus values tend to increase with increasing content of unmodified and modified clay. With the increase in clay loadings, surface modified clay showed a little higher values of elastic modulus when compared to surface unmodified montmorillonite clay. This is due to the fact that the effect of surface modification causes better level of penetration of the epoxy resin into the galleries

*DOI: http://dx.doi.org/10.5772/intechopen.88236*

of montmorillonite clay.

compared to pristine polymer (epoxy).

#### *Mechanical and Tribological Properties of Epoxy Nano Composites for High Voltage Applications DOI: http://dx.doi.org/10.5772/intechopen.88236*

Isık and co-authors [11] reported the clay loading effect on the tensile strength of organically modified clay filled epoxy nanocomposites. The tensile strength decreases with increasing content of clay. This is due to the nonuniform dispersion of clay, agglomeration of clay causes stress concentration and decreased polymer clay interactions. They also observed that the tensile modulus of the nanocomposite increases with increasing amount of clay. The mechanical properties of montmorillonite filled epoxy nanocomposites were studied by Akbari and Bagheri [12]. They found a decrease in flexural strength with increasing the content of organically modified clay and this is due to the fact that intercalated structure of clay in the nanocomposites. Kaya and co-authors [13] analyzed the flexural and tensile properties of clay filled epoxy nanocomposite samples. The surface modified and unmodified montmorillonite clay were added to the epoxy matrix with increasing clay contents from 1 to 10 wt.%. The author presented that both tensile and flexural modulus values tend to increase with increasing content of unmodified and modified clay. With the increase in clay loadings, surface modified clay showed a little higher values of elastic modulus when compared to surface unmodified montmorillonite clay. This is due to the fact that the effect of surface modification causes better level of penetration of the epoxy resin into the galleries of montmorillonite clay.

From the above studies, it was found that the mechanical properties such as flexural and tensile strength reduce for the fabricated nanocomposite samples with surface modified and not modified clay when compared to pristine base matrix. This is mainly due to the creation of voids, feeble adhesion points along the fillermatrix surface interface during nanocomposite processing. Velmurugan and Mohan [14] have reported the presence and effect of quaternary ammonium modified montmorillonite clay content on the mechanical properties of clay-epoxy nanocomposites. They reported that the tensile modulus of the fabricated samples increased about three times when compared to base pristine epoxy with the accumulation of 10 wt.% surface modified clay. This is due to the fact that the exfoliation structure of clay layers and surface interfacial adhesion between the nanoclay and the epoxy matrix, whereas, the tensile strength reduced in spite of the content of the clay as compared to pristine polymer (epoxy).

Yasmin and co-authors [15] conducted studies on the mechanical characteristics of surface modified montmorillonite clay added epoxy nanocomposite samples with variation in concentration of clay from 1 to10 wt.% fabricated by shear mixing technique. Based on their report, the addition of surface modified nanoclay particles there is a significant improvement both in elastic and storage modulus of base epoxy resin. In addition, there is an increase in storage modulus with increasing in clay content. This was ascribed to intercalation or exfoliation structure of surface modified nanocly (Cloisite 30B) in base epoxy matrix. The results reconfirmed that there is a direct relation between the degree of intercalation or exfoliation and the mechanical properties of the fabricated nanocomposites samples.

Basara and co-authors [16] analyzed the presence and effect of clay substance and morphological structure on mechanical properties of nanocomposites. The organically surface modified (Cloisite 30B) and natural or unmodified (Cloisite Na+) clay with the content varying from 0.5 to 11 wt.% was reinforced into base epoxy matrix and observed that tensile modulus increased with clay content. This is attributed to stiffening effect of montmorillonite clay in two types of clay reinforced nanocomposites. Cloisite 30B and Cloisite Na+ reinforced nanocomposite samples showed utmost tensile strength at 1 and 0.5 wt.% respectively. The reason for the decrease in tensile strength at larger montmorillonite clay content is due to the stress concentration effect of the agglomerated clay particles and lesser surface interactions.

*Nanorods and Nanocomposites*

in the thermoset polymer matrix.

Although, the broad group of nanocomposite polymer materials have been widely investigated and fairly understood, the development of thermoset polymer based nanocomposites which also belong to this group, still remains a challenge. This is mainly because of the difficulty in uniform dispersion of nanofiller particles

Many studies shown improvements in the mechanical strength and modulus of nanoclay filled epoxy resin nanocomposites as compared to the Epoxy resin [3]. Wang and co-authors [4] reported another technique called unique "slurry compounding" to fabricated exfoliated nanoclay-Ethacure nanocomposites. This composites shows improvements in the modulus of epoxy resin by about 40% with 5 wt.% of nanoclay, but with decreased tensile strength. They attributed this partial achievement to the feeble surface interface and occurrence of air foam in the nanocomposite samples. Gefu and co-authors [5] studied vinyl ester with 1 wt.% nanoclay. They have compared five types of mixing combinations such as (i) 30 min manual stirring, (ii) 30 min manual stirring and 1 h sonification mixing, (iii) 30 min manual stirring and 1 h sonification mixing followed by three-roll mill shear mixing, (iv) 30 min manual stirring and 1 h sonification mixing followed by three-roll mill shear mixing and 1 h sonification mixing, and (v) 30 min manual stirring and 1 h sonification mixing followed by three-roll mill shear mixing with 1 h sonification mixing and three-roll mill shear mixing while holding other factors constant.

It could be generally concluded that intensive mixing improved exfoliation until a certain point (defined as optimum point) and then its positive effects diminish with further mixing efforts. Considering reduced mixing effort of method iv, it is being recommended. Kotsilkova and co-authors [6] studied the flexural strength and flexural modulus of epoxy-clay nanocomposites fabricated by direct method or without solvent method and indirect method or solvent processing techniques. Different organic modifiers were used to functionalize the clay. It has been observed that the mechanical properties are majorly dependent on nanocomposite structure and the type of solvent used. The fabricated samples by direct processing method or without using solvent technique showed increased flexural modulus. The modulus of the nanocomposites at 5 volume percentage of clay content increased

In compare, the flexural modulus of fabricated nanocomposites fabricated by adding solvent or solvent processing technique is not affected [7]. The flexural strength of the fabricated nanocomposites has increased when compared to the samples fabricated by the direct processing method or without using solvent. This is due to the strength of the solvent, acting as a plasticizer for the base resin and alters the interfacial adhesions. In earlier studies it is reported that nanoclay appears to have either the intercalated structure or the partially exfoliated structure. The maximum improvement achieved in the modulus was of the order of about 80%

While the addition of nanoclay to epoxy resin generally increases the tensile modulus, it decreases the tensile strength and fracture strain [8, 9]. This was mainly attributed to the agglomeration of nanoclay and presence of voids. Organically modified nanocly effect on the physical, structural properties of organically modified clay –epoxy nanocomposites samples was examined by Dean and co-authors [10]. They reported that different morphological structures such as intercalation, partial and full exfoliation of nanoclay. The degree of intercalation morphology varies and interlayer expansion was observed. This is related to the mechanical properties of the fabricated nanocomposite samples. With the increase in the clay content, 35% increase in tensile modulus for the 2 wt.% sample, 15% increase in tensile modulus for 4 wt.% sample and 30% increase in the tensile modulus for the

**196**

significantly.

with 10 wt.% nanoclay [7].

sample with 6 wt.% respectively.

Zhu and co-authors [17] investigated PA6/TiO2 nanocomposites which resulted in improved spinnability and mechanical properties. It was observed that tenacity at break and the initial modulus of PA6 with modified nano-TiO2 composites showed improvement by about 10, 20%, respectively, as compared to the pure PA6.

Mina and co-authors [18] studied TiO2 filled isotactic polypropylene (iPP) composites with TiO2 which was first single-extruded by an extruder and then double-molded by compression molding. Micro-hardness increased rapidly and then leveled off with increasing filler content. Variations with respect to molding conditions were also observed.

According to Dean and co-authors [19] the inter-gallery spacing of surface modified montmorillonite nanoclay increased efficiently. Ha and co-authors [20] have demonstrated that the tensile strength and elastic modulus of surface modified montmorillonite nanoclay Epoxy nanocomposites are elevated than that of unmodified montmorillonite nanoclay-Epoxy composites. Ha and co-authors [21] have stated that surface modification increases the interlayer gallery expansion, in turn improves the dispersion of nanoclay into the base polymer. Wang and co-authors [22] reported that improvement in the modulus and fracture toughness of base polymer such as epoxy was achieved by adding surface modified nanoclay using silane functionalizer. Lam and co-authors [23, 24] reported the effect of bunch of nanoclay and shows there is a best nanosized clay weight percentage in the nanocomposites in order to acquire maximum mechanical properties. The highest hardness is achieved for 4 wt.% of nanoclay. Furthermore, increasing the nanoclay content affected in reducing the hardness of the nanocomposites [23, 24].

Huang and co-authors [25] fabricated the composites of TiO2 and epoxy by direct solution adding method, where directly epoxy and nanosized TiO2 in the liquid form were mixed with the catalystmethyl isobutylketone. Based on the results obtained from XRD, the hydrogen bonds are formed by adding TiO2 nanoparticles in epoxy resin. The Scanning Electron Microscopy result recommended that TiO2 nanoparticles are uniformly distributed within the epoxy nanomaterial. The nanocomposite properties degrade if the nanofillers TiO2 exceeds 3 wt.%. In addition, mechanical properties are enhanced by raising the concentration of catalyst such as methyl isobutylketone.

Elansezhian and co-workers [26] studied the wear and tensile strength behavior of vinyl ester with silica, alumina and zinc oxide nano fillers and reported that the addition of silica to the vinyl ester resin significantly improved wear resistance as compared to other two fillers. The functionalized silica nanoparticles showed an improved dispersion with vinyl ester resin. Functionalization caused particle dispersion more uniformly in the polymer matrix. As-received nanoparticles show lower tensile strength whereas functionalized nanoparticles show improved tensile strength by more than 15% at 5 wt.% loading as compared to unfilled resin.

Haque and co-authors [27] reported that the flexural strength of glass-vinyl ester-clay nanocomposites containing 1 wt.% nanoclay improved by 24% in comparison to conventional composites. The improvement in the mechanical properties of the nanocomposites mostly relies on achieving proper polymer/silicate layer (intercalated) or uniformly dispersed (exfoliated) morphology in the structure. It is observed that incorporation of higher percentage of nanoclay particles (> 2 wt.%) into the resin, may not improve mechanical properties.

Apoorva and co-authors [28] reported that tensile modulus of nanocomposites with nanoclay (cloisite 10A and Vinyl monomer) increases by about 25% with organically modified clay addition. The tensile modulus improved in the nanocomposites with Cloisite in a more effective manner. Whereas, at elevated clay load, cloisite 10A and Vinyl monomer clays emerge to execute uniformly good,

**199**

of nanofillers.

*Mechanical and Tribological Properties of Epoxy Nano Composites for High Voltage Applications*

the mechanical strength appears to be marginally reduces with cloisite 10A nanocomposites. Vinyl monomer clay nanocomposites prove a little diverse trend [28]. The little concentration of Vinyl monomer clayin the nanocomposite system, the tensile strength show to enhance and this enhance is dedicated to the chemical link created connecting Vinyl monomer clay's surface functionalization and Vinyl ester manacles through the process of curing, which is additional useful in transfer pressure to the nanoclay platelets compared to an unreactive clay such as cloisite 10A. The succeeding small fall in tensile strength at 1 wt.% and two and half weight

The attempts have been made to fabricate nanoparticle filled epoxy nanocomposites to progress the tribological properties of the base polymers. Recently, nanosized inorganic fillers such as nanometer sized Silicon Carbide (SiC), Silicon di-oxide (SiO2), Zinc oxide (ZnO), Zirconium di-oxide (ZrO2), Alumina (Al2O3) and Titaniam di-oxide (TiO2) be used as nanofillers in epoxy to attain excellent tribological property [29, 30]. The main benefit of nanosized filler filled composites over micro-sized filler filled composites lie down in its performance development which is attained at comparatively small percentage of the nanofillers. At higher filler loadings, due to higher percentage of particles or atoms present on the surface of the nanofillers, agglomeration takes place very easily because of nonuniform dispersion of nanofillers in the polymer by using conventional mechanical mixing techniques [31]. This results in the poor performance of the nanocomposites at higher percentage of loading than the micro filler based composites system.

Many authors reported that, polymer composites is widely used in wear applications such as cams, brakes, bearings and gears due to their self-lubrication property, low co-efficient of friction and improved resistance to wear. The inborn shortage of polymers is changed profitably by using special micro fillers and nanosized particles. More polymer micro and nanocomposites are in use as sliding devices which were formerly made of metallic materials. On the other hand, extreme improvements are in progress to find out different areas of purpose to modify their proper-

Extensive work has been approved in the development of nanofiller composites through the addition of nanosized particles namely ceramics and carbon in polymer based matrices. For example surface modified nanoclays [34], carbon nanotubes [35], alumina [36] ZnO and SiC nanoparticles [37] are incorporated in to the base polymers. Majority of these cases are on the effect of filler particle in polymer composites descending against metallic surface results in decrease of rate of wear, friction co-efficient and larger mechanical strength which is owing to incorporation

Recent reports on the wear behavior of surface modified nanoclay added polyamide6 (PA6) by Srinath and Gnanmoorthy [38] and Dasari and co-authors [39] has exposed lesser friction and higher rate of wear resistance, this is dedicated

Nanofillers inclined to develop a persistent transmit layer on the opposite face which defends the nanocomposite sample outside surface from straight make contact with the opposite face thus reduces rate of friction and rate of wear. The incorporation of organically modified nanoclay into the base polymer matrix to formulate the nanocomposite is an alternative way to change the properties of composite material [40]. Ng and co-authors [41] directly dispersed TiO2 nanoparticles in to the epoxy. The resultant composites appeared not only to be tougher than the traditional micro-particle filled epoxy but also to possess a higher scratch resistance. Rong and co-authors [42] also carried out wear trial on nanotitanium-epoxy nanocomposites and studied that the tribological characteristics is importantly depends

to the increase of the bond between nanofiller and the polymer matrix.

on the state of dispersion and homogeneity of the filler.

percentage clay content was due to lack of proper distribution of clay.

ties for higher load-carrying and ecological conditions [32, 33].

*DOI: http://dx.doi.org/10.5772/intechopen.88236*

#### *Mechanical and Tribological Properties of Epoxy Nano Composites for High Voltage Applications DOI: http://dx.doi.org/10.5772/intechopen.88236*

the mechanical strength appears to be marginally reduces with cloisite 10A nanocomposites. Vinyl monomer clay nanocomposites prove a little diverse trend [28]. The little concentration of Vinyl monomer clayin the nanocomposite system, the tensile strength show to enhance and this enhance is dedicated to the chemical link created connecting Vinyl monomer clay's surface functionalization and Vinyl ester manacles through the process of curing, which is additional useful in transfer pressure to the nanoclay platelets compared to an unreactive clay such as cloisite 10A. The succeeding small fall in tensile strength at 1 wt.% and two and half weight percentage clay content was due to lack of proper distribution of clay.

The attempts have been made to fabricate nanoparticle filled epoxy nanocomposites to progress the tribological properties of the base polymers. Recently, nanosized inorganic fillers such as nanometer sized Silicon Carbide (SiC), Silicon di-oxide (SiO2), Zinc oxide (ZnO), Zirconium di-oxide (ZrO2), Alumina (Al2O3) and Titaniam di-oxide (TiO2) be used as nanofillers in epoxy to attain excellent tribological property [29, 30]. The main benefit of nanosized filler filled composites over micro-sized filler filled composites lie down in its performance development which is attained at comparatively small percentage of the nanofillers. At higher filler loadings, due to higher percentage of particles or atoms present on the surface of the nanofillers, agglomeration takes place very easily because of nonuniform dispersion of nanofillers in the polymer by using conventional mechanical mixing techniques [31]. This results in the poor performance of the nanocomposites at higher percentage of loading than the micro filler based composites system.

Many authors reported that, polymer composites is widely used in wear applications such as cams, brakes, bearings and gears due to their self-lubrication property, low co-efficient of friction and improved resistance to wear. The inborn shortage of polymers is changed profitably by using special micro fillers and nanosized particles. More polymer micro and nanocomposites are in use as sliding devices which were formerly made of metallic materials. On the other hand, extreme improvements are in progress to find out different areas of purpose to modify their properties for higher load-carrying and ecological conditions [32, 33].

Extensive work has been approved in the development of nanofiller composites through the addition of nanosized particles namely ceramics and carbon in polymer based matrices. For example surface modified nanoclays [34], carbon nanotubes [35], alumina [36] ZnO and SiC nanoparticles [37] are incorporated in to the base polymers. Majority of these cases are on the effect of filler particle in polymer composites descending against metallic surface results in decrease of rate of wear, friction co-efficient and larger mechanical strength which is owing to incorporation of nanofillers.

Recent reports on the wear behavior of surface modified nanoclay added polyamide6 (PA6) by Srinath and Gnanmoorthy [38] and Dasari and co-authors [39] has exposed lesser friction and higher rate of wear resistance, this is dedicated to the increase of the bond between nanofiller and the polymer matrix.

Nanofillers inclined to develop a persistent transmit layer on the opposite face which defends the nanocomposite sample outside surface from straight make contact with the opposite face thus reduces rate of friction and rate of wear. The incorporation of organically modified nanoclay into the base polymer matrix to formulate the nanocomposite is an alternative way to change the properties of composite material [40]. Ng and co-authors [41] directly dispersed TiO2 nanoparticles in to the epoxy. The resultant composites appeared not only to be tougher than the traditional micro-particle filled epoxy but also to possess a higher scratch resistance. Rong and co-authors [42] also carried out wear trial on nanotitanium-epoxy nanocomposites and studied that the tribological characteristics is importantly depends on the state of dispersion and homogeneity of the filler.

*Nanorods and Nanocomposites*

conditions were also observed.

methyl isobutylketone.

the pure PA6.

Zhu and co-authors [17] investigated PA6/TiO2 nanocomposites which resulted in improved spinnability and mechanical properties. It was observed that tenacity at break and the initial modulus of PA6 with modified nano-TiO2 composites showed improvement by about 10, 20%, respectively, as compared to

Mina and co-authors [18] studied TiO2 filled isotactic polypropylene (iPP) composites with TiO2 which was first single-extruded by an extruder and then double-molded by compression molding. Micro-hardness increased rapidly and then leveled off with increasing filler content. Variations with respect to molding

According to Dean and co-authors [19] the inter-gallery spacing of surface modified montmorillonite nanoclay increased efficiently. Ha and co-authors [20] have demonstrated that the tensile strength and elastic modulus of surface modified montmorillonite nanoclay Epoxy nanocomposites are elevated than that of unmodified montmorillonite nanoclay-Epoxy composites. Ha and co-authors [21] have stated that surface modification increases the interlayer gallery expansion, in turn improves the dispersion of nanoclay into the base polymer. Wang and co-authors [22] reported that improvement in the modulus and fracture toughness of base polymer such as epoxy was achieved by adding surface modified nanoclay using silane functionalizer. Lam and co-authors [23, 24] reported the effect of bunch of nanoclay and shows there is a best nanosized clay weight percentage in the nanocomposites in order to acquire maximum mechanical properties. The highest hardness is achieved for 4 wt.% of nanoclay. Furthermore, increasing the nanoclay

content affected in reducing the hardness of the nanocomposites [23, 24].

Huang and co-authors [25] fabricated the composites of TiO2 and epoxy by direct solution adding method, where directly epoxy and nanosized TiO2 in the liquid form were mixed with the catalystmethyl isobutylketone. Based on the results obtained from XRD, the hydrogen bonds are formed by adding TiO2 nanoparticles in epoxy resin. The Scanning Electron Microscopy result recommended that TiO2 nanoparticles are uniformly distributed within the epoxy nanomaterial. The nanocomposite properties degrade if the nanofillers TiO2 exceeds 3 wt.%. In addition, mechanical properties are enhanced by raising the concentration of catalyst such as

Elansezhian and co-workers [26] studied the wear and tensile strength behavior of vinyl ester with silica, alumina and zinc oxide nano fillers and reported that the addition of silica to the vinyl ester resin significantly improved wear resistance as compared to other two fillers. The functionalized silica nanoparticles showed an improved dispersion with vinyl ester resin. Functionalization caused particle dispersion more uniformly in the polymer matrix. As-received nanoparticles show lower tensile strength whereas functionalized nanoparticles show improved tensile

strength by more than 15% at 5 wt.% loading as compared to unfilled resin.

into the resin, may not improve mechanical properties.

Haque and co-authors [27] reported that the flexural strength of glass-vinyl ester-clay nanocomposites containing 1 wt.% nanoclay improved by 24% in comparison to conventional composites. The improvement in the mechanical properties of the nanocomposites mostly relies on achieving proper polymer/silicate layer (intercalated) or uniformly dispersed (exfoliated) morphology in the structure. It is observed that incorporation of higher percentage of nanoclay particles (> 2 wt.%)

Apoorva and co-authors [28] reported that tensile modulus of nanocomposites

with nanoclay (cloisite 10A and Vinyl monomer) increases by about 25% with organically modified clay addition. The tensile modulus improved in the nanocomposites with Cloisite in a more effective manner. Whereas, at elevated clay load, cloisite 10A and Vinyl monomer clays emerge to execute uniformly good,

**198**

Shao Rong and co-authors [43] have proved that the epoxy/SiO2-TiO2 nanocomposites are effective in lowering the frictional coefficient and wear rate. The results of these experiments [43] indicate that the wear mechanism of composites changed from adhesive wear to mild abrasive wear and fatigue wear with the increase of the SiO2-TiO2 content. Chang and co-authors [44] have proved that the addition of nanoTiO2 apparently reduced the frictional coefficient and significantly enhanced the wear resistance of the composites, especially at contact pressures and sliding velocities.

The present study incorporates different evaluation techniques to encompass properties of mechanical and wear characteristics.
