Effect of Silica Nanoparticles and Modified Silica Nanoparticles on the Mechanical and Swelling Properties of EPDM/SBR Blend Nanocomposites

The influences of nanosilica and modified nanosilica on cure, compression set, mechanical and swelling characteristics are studied in blends of ethylene-propylene-diene monomer (EPDM)/styrene-butadiene rubber (SBR). In EPDM/SBR composites, the nanosilica made from rice husk ash (RHA) was utilised as a reinforcing nanofiller. The interaction between the nanosilica and the EPDM/SBR matrix at the interface is crucial for the production of rubber composites. This study uses bis[3-(triethoxysilyl)propyl] tetrasulfide (TESPT) and polyoxyethylene (20) sorbitan monolaurate (TWEEN-20) as a silica modifier, with the ratio of TESPT to TWEEN-20 maintained at 2:1. The cure and mechanical characteristics, compression set, abrasion and swelling resistance increased with the incorporation of nanosilica and modified nanosilica. By interacting at the interface between silica nanoparticles and the EPDM/SBR rubber matrix, TESPT with the TWEEN-20 modifier exhibits a considerable effect on cure characteristics, mechanical qualities, and swelling resistance.


Introduction
Blending of rubbers has been recognized as a more suitable method to achieve materials representing tailored properties by the desired combination of rubbers advantages rather than developed a new rubber [1,2].EPDM rubber is a non-polar rubber, M-Class rubber and saturated rubber with different types of diene (namely, ethylidene norbomene (ENB), 1,4-hexadiene (HD), and dicyclopentadiene (DCPD)).Among the diene, ENB-EPDM compound is the best overall properties.It is an elastomer whose high weathering, ozone, oxidation, ageing and heat resistance properties and extensively make it suitable for use in the applications of electrical power cables, automotive and construction.To overcome the weak adhesion and high cost it is blended with styrenebutadiene rubber (SBR) [3].EPDM/SBR are widely used in seals, conveying belts, gaskets, tires, electrical insulators, tubes, etc [4].When the ratio of EPDM/SBR blends was 80/20, the rubber compounds produced the highest mechanical characteristics and abrasion resistance [5,6].Therefore, these mixtures are suitable for use as rubber matrix for a variety of purposes.
To obtain the majority of the strength and strength-related qualities (i.e., physical and mechanical capabilities) necessary for practical applications, rubber compounds must typically be reinforced with fillers [7].The two main reinforcing fillers used in the modern tyre business are silica (SiO 2 ) and carbon black (CB) [8].CB is the most popular type of reinforcing filler used in rubber composites, and it significantly boosts their performance [9].On the other hand, the manufacture of CB is profoundly dependent on fossil fuels (natural gas, coal and petroleum), and its use releases a number of pollutants that cause environmental issues, dark colour, and significant resource waste.The demand for and consumption of energy on a global scale has been quickly rising while the availability of fossil fuels has been declining.Even though CB dominates the reinforcement market, SiO 2 particles outperform CB in reducing the saving energy and rolling resistance of tire tread [10,11].SiO 2 is hydrophilic because of the silanol functional groups on its surface, in contrast to CB, which is hydrophobic by nature and used in hydrophobic rubbers.As a result of their hydrogen bonding, the silanol functional groups exhibit stronger filler-filler interactions than CB, which associates with itself through lesser Van Der Waals forces.The dispersion and distribution of silica particles are less uniform in hydrophobic rubber, such as SBR and EPDM rubber, two rubbers used for the development of rubber products, due to higher filler-filler interactions [12][13][14].Previous studies suggested eating silane coupling agents (SCA), which react with both silica and rubber, to improve the poor compatibility between rubber and SiO 2 or change the way that silica is dispersed in rubber [15][16][17][18].SCA was used for this SiO 2 modification because it is an amphipathic surface modifier and an interfacial compatibiliser [19,20].
The SCA has at minimum one alkoxy group, and it can dehydrate condensation with silica particles to create a stable Si-O-Si chemical structure [15,21].SCA/SiO 2 /rubber composite is ideally suited for creating "green tyres" since it has a uniform silica dispersion and optimum dynamic mechanical performance [22][23][24][25].Nowadays, many types of SCAs for instance bis[γ-triethoxysilylpropyl] disulfide (TESPD), bis [3-(triethoxysilyl) propyl] tetrasulfide (TESPT) and mercaptopropyltriethoxysilane (MEPTS), especially TESPT, are commercially developed for the tire industry [26], and are utilised frequently to alter SiO 2 particle size for creating rubber/SiO 2 composites [24].Better SiO 2 particle dispersion in rubber matrix can be achieved by these SCAs' reaction with silanol functional groups [27,28].These days, they can react with rubber molecules' double bonds (unsaturation) thanks to their sulphide group.So, the SCA creates a "coupling bridge" between the molecules of rubber and SiO 2 .On the contrary, SCAs have some disadvantages: a) these SCAs have the potential to emit volatile organic chemicals, which can pollute the environment, be detrimental to human health, and even cause an explosion or fire [29], b) although the mixing temperature and time are carefully regulated, the sulphide-containing SCAs and the reaction between rubber molecules, which can result in "scorchy (i.e., pre-crosslinking)" behaviour, is inevitable during the process [30], and c) it takes five to ten minutes for the SiO 2 particle and SCA to undergo a complex, high-energy chemical reaction that requires a combination to be heated to 140 to 160 C [31].The specific structure of TESPT is presented in Fig. 1.More critically, rubber composites do not have the best SiO 2 particle dispersion.As a result, creating rubber/SiO 2 composites solely employing sulfide-containing SCAs for SiO 2 surface modification is not the best method.
Based on the difficulties of consuming sulphide-containing SCA for SiO 2 particle modification, Yake Xiao et al. [32] hypothesized that TWEEN-20 can promote high dispersion of SiO 2 particles.The TWEEN-20 comprises of four long arms comprised of an 11-carbon fatty chain, three polyether chains, and terminal hydroxyl groups.The specific structure of TWEEN-20 is showed in Fig. 2. The oxygen on the polyether should create a hydrogen bond with the silanol groups on the surface of the SiO 2 particles, as is shown from this image.TWEEN-20 may be able to migrate to the SiO 2 particle's surface as a result of this hydrogen bonding with the silanol groups.Prior until this, there shouldn't have been any volatile organic chemicals present on the surface of the SiO 2 particle for the terminal hydroxyl groups to chemically react with.Additionally, the SiO 2 particles' polarity should be weakened by the lengthy fatty chain to improve compatibility with the rubber matrix.The fatty chain element of TWEEN-20 is well compatible with rubber matrix, but the terminal hydroxyl and polyether parts of TWEEN-20 should be physically and chemically changed for SiO 2 particle.TWEEN-20 should therefore significantly enhance SiO 2 particle dispersion.TWEEN-20, on the other hand, must not create chemical connections with the rubber matrix.In order to enhance the overall characteristics of the polymer composite, a TESPT was utilised to create a chemical interaction between the polymer matrix and the reinforcement filler.As a result, a system made up of TESPT and TWEEN-20 was developed.TESPT created the chemical contact between the SiO 2 particle and rubber matrix, and TWEEN-20 achieved high SiO 2 particle dispersion.The combined effects of TWEEN-20 and TESPT ought to lower volatile organic compounds, enhance "scorch safety", and achieve the best SiO 2 particle dispersion in the rubber matrix.Furthermore, rubber composites perform best both statically and dynamically when the TESPT to TWEEN-20 ratio is 2:1.
In this study, SiO 2 particles were modified by combining TESPT and TWEEN-20 in a constant 2:1 ratio and EPDM/ SBR composites were created by open mill mixer.In this work, the effect of nano-SiO 2 ) and modified nano-SiO 2 on cure and mechanical behaviors, compression set, abrasion resistance, and swelling resistance (in terms of mole percent uptake) of EPDM/SBR composites were examined.In addition, the morphology of the composites also studied to evaluate the dispersion and agglomeration of nano-SiO 2 and modified nano-SiO 2 particles on EPDM/SBR blend.

Preparation of Nanosilica
Equations ( 1) and ( 2), which show the dissolution and precipitation processes used to create SiO 2 nanoparticles in our laboratory, are shown in Fig. 3.The detailed process for making nano-SiO 2 is covered in our earlier study publication [35].

Preparation of Nanocomposites
The compounding formulation of the EPDM/SBR/nano-SiO 2 nanocomposite is provided in Table 1.The EPDM/ SBR nanocomposites were produced by an open-mill mixer equipment.The base rubber compound was contained of 80/20 phr/phr of EPDM/SBR blend and prepared by the following order: EPDM and SBR were combined after being masticated for 4 min.And then different amounts of SiO 2 nanoparticles were added to it.Finally, the prepared compound and other additives were added to the obtained compound.By using an oscillating disc rheometer, the compound's ideal cure time (t C90 ) at 160 °C was determined.The compounded rubber was vulcanized at 160 C under 30 MPa pressure in a semi-automated compression molding press up to its optimum cure time.

Cure Characteristics
Cure characteristics like torque (miminum torque (M l ) and maximum torque (M h )) and t 90 have been determined by the rubber process analyzer.M l (low Mooney) M h (high Mooney), scorch time (t s2 ) and optimum cure time (t C90 ) have been recorded using an Oscillating Disc Rheometer (ODR) whose procedures followed ASTM D-2048 standard.About 10 gm of circular shaped unvulcanized rubber sample has been punched out and then placed between two rotating discs of the ODR.Measurements of above-mentioned torque values and times have been determined at a constant temperature of 160 °C, at an oscillation arc of 0.5° and at 100 cycles per minutes (1.66 Hz) for 15 min.A function of time for the torque has been observed.The t C90 corresponding to the increase of 90% of the M h , i.e., t 90 has been measured from the corresponding rheographs.The cure rate index (CRI) was calculated using the formula below.

Shore A Hardness
In accordance with ASTM D-2240 standard, Shore A hardness tests were performed using a Durometer.The tester's ability to penetrate the material allowed for the measurement of hardness.The results that were published were the averages obtained from five independent measurements.

Tensile Properties
According to the ASTM D-412 standard and type C shaped samples, the tensile characteristics of EPDM/SBR with various nanosilica contents were assessed at 23 °C.To assess the tensile capabilities of the composite, dumbbell specimens with dimensions of 2 mm in thickness, 25 mm in gauge length, and 4 mm in width were punched out of the vulcanised rubber material [36].Dak System Inc.'s series 7200 UTM (model: T-72102), with a cross head displacement rate of 500 mm/min, was used for the tensile tests.The 100% modulus (M100), elongation at break (EAB), and tensile strength were determined (TS).

Tear Strength
The ASTM D-624 specification and type B shaped samples were used in the tear tests of EPDM/SBR, along with an angle test piece with dimensions and a thickness of 2 mm.The UTM (before described model) was used to measure tear strength (TAS) at a condition of tensile test.

Rebound Resilience
The rebound resilience (RR) characteristics were evaluated using a resiliometer in line with the recognised ASTM D-2632 testing technique [37].

Abrasion Resistance
The abrasion resistance (AR) of the EPDM/SBR composites was evaluated in terms of relative volume loss from the abrasion tester using a Zwick DIN Abrader, model 6102, in line with the ASTM D-5963 standard testing technique.This experiment involved the application of a 10 N load to a rolling, sliding cylinder on grade 60 emery paper while it was travelling at a constant speed of 0.32 m/s.The DIN volume loss of the composites was calculated using the formula in the following equation.

Compression Set
With the aid of the compression device, the compression set (CS) was established.CS test was achieved as per ASTM D-395 standards and type: method B. The compression degree for the (4) CS device, which consists of two flat stainless-steel plates, was 25% deflection.The specimen's initial thickness is measured to be 12.5 mm, and its diameter is 29 mm.The specimen is compressed to 25% of its original thickness and within two hours of the compression set assembly, the compression device was kept in an air circulating oven at different conditions such as 23 °C for 24, 48 h and 72 h and, 70 °C and 100 °C for 24 h.The rubber specimen was then taken out of the compression tool and given 30 min to cool.Following the recovery phase, the ultimate thickness was determined, and the compression set was calculated utilising the formula provided in the equation below [38,39].
where, t o = original thickness,t 1 = final specimen thickness and t s = slip gauge thickness.

Crosslinking Density
The crosslinking density ( ) was calculated using the equilibrium swelling immersion method.During three days at 23 C, EPDM/SBR nanocomposites were immersed in toluene, with the penetrant being replaced with fresh toluene each day in order to calculate the .Crosslinking density ( ) was determined by the following equation [40][41][42]: where, = crosslinking density (mol/cm 3 ) and M c = molar mass (or) molecular weight of the polymer between crosslinks.
The molar mass between the crosslinks in the composites was calculated using the Flory-Rehner equation, which is shown in the illustration below [40][41][42][43]: where, ρ p = density of the rubber (g/cm 3 ), V r = volume fraction of rubber in the solvent-swollen filled compound, V s = molar volume of the penetrant, χ = interaction parameter of the rubber (0.3) [44], and The following equation can be used to compute V r (8) [45]: where, Q m = weight swell of the EPDM/SBR composites in penetrant.

Swelling Resistance
According to ASTM D-471, swelling tests were conducted on several penetrants.In this work, we are using different penetrants such as n-heptane, n-pentane, mesitylene, xylene, toluene, benzene, dichloromethane, n-hexane, n-octane, carbon tetrachloride and chloroform.Using a high accuracy electronic balance, curing test pieces of the EPDM/SBR composites with dimensions of 25 × 25 × 2 mm 3 were weighed.The test pieces were reweighed after being submerged in n-octane for 72 h after being cured.Materials are appraised in a manner similar to this after being immersed in various penetrants [46].The equation below was used to obtain the mole percent uptake (MPU), Q t .
where, M t = mass of the sample after time (seventy-two hours) of absorption, M 0 = initial mass of the sample, and.M r = molecular weight of the penetrant.

Morphology
Using a Hitachi S-4160 equipment and a 3 kV voltage, FESEM was used to analyse the surface morphology of the EPDM/SBR composite.Before the characterisation, samples with fractured surfaces were coated with gold.

Cure Properties
The curing properties showing both torques and times of the EPDM/SBR nanocomposites with various contents of nanosilica are presented in comparison with modified nanosilica filled EPDM/SBR composite are publicized in Table 2.
As important vulcanization parameters, (i) minimum rheometric torque (M l ), (ii) maximum rheometric torque (M h ), (iii) rheometric delta torque or rheometric torque difference (ΔM = M h -M l ), (iv) cure rate index (CRI), (v) scorch time (t s2 ), and (v) optimum cure time (t C90 ) was determined from the rheometer.The t s2 , t C90 and CRI are the time corresponding to two Mooney units increase in the torque above the M l , the point in the cure curve where the torque increases by 90% and vulcanization rate, respectively [47][48][49].Calculating the Ml, Mh, and ∆M will give you an idea of the masticated rubber's viscosity, the stock modulus, and the amount of crosslinking, respectively [50][51][52].
The filler content and its surface characteristics have an impact on the composites' curing characteristics [53].For (9) EPDM/SBR-nanosilica composites, it has been observed that as the concentration of nanosilica rises, so do the t 90 , t s2 , and torque values (M H , M L and ∆M).The adsorption of cures by the silica particles is what causes the increase in t90 with nanosilica concentration [54].Nanosilica composites modified with EPDM/SBR have a somewhat lower t90 than the same composite made with silica that has not been changed.The quantity of silanol groups on the surface of the modified silica decreased, which shortened the vulcanization process' cure time.t s2 is the amount of time needed to raise the initial torque by 2 dNm or the amount of time that must pass before vulcanization may begin.When compared to EPDM/SBR gum, nanosilica loaded EPDM/SBR compounds have a higher t s2 value.This is due to the interaction of highly polar nanosilica with ZnO during vulcanization, which results in silica bound ZnO and decreases the activity of ZnO to increase the accelerator during vulcanization [55].
Because the modified nanosilica particles are evenly dispersed, the t s2 of EPDM/SBR-modified nanosilica is higher than that of EPDM/SBR-nanosilica.A higher t s2 suggests that vulcanisates containing modified silica are more processable.As the nanosilica loading increases, both M L and M H rise.As the concentration of nanosilica increases, the ∆M likewise rises.The M L , M H and ∆M of the modified nanosilica filler filled composite are higher than unmodified nanosilica filled one.It indicates that rise in the overall rigidity of the EPDM/SBR composite and the good interaction between rubber and modified nanofiller.When compared to all other EPDM/SBR-nanosilica composites, the ∆M is higher for the EPDM/SBR-modified nanosilica composite.This suggests that the alteration causes a lower silanol group to form on the surface of nanosilica, preventing the adsorption of curatives during the vulcanization step.Moreover, as seen in Fig. 12, this will lead to a larger crosslink density.

Mechanical Properties
Nanosilica's ability to increase the abrasion resistance, strength, fatigue resistance and extensibility of EPDM/SBR compounds has long been known.Only tensile qualities (tensile strength (TS), elongation at break (EAB), and 100% modulus (M100)), tear strength (TAS), hardness, abrasion resistance (AR) and rebound resilience (RR) are taken into consideration in this experiment.Figure 4 depicts a schematic picture of the physical and chemical interaction between TESPT-TWEEN-20 and silica based on my knowledge of the subject.Figs 4, 5, 6, 7, 8, 9 and 10 displays the mechanical characteristics of all compounds, including their tensile qualities, hardness, TAS, RR, and AR.

Tensile Properties
The tensile properties (TS, EAB and M100), RR, TAS, AR and hardness showed that the nanosilica or modified nanosilica content noticeably affects the mechanical properties of EPDM/SBR nanocomposite.The TS, EAB and M100 are given in Figs. 5, 6 and 7, respectively.TS, EAB and M100 was increased with the nanosilica content of 6 phr.Further increase of nanosilica content to 10 phr has noticeably decreased the values of the TS, EAB and M100.The TS and M100 of modified nanosilica filler filled EPDM/SBR composites are obviously improved compared with unmodified nanosilica filler filled composite as shown in Figs. 5 and  7, respectively.The fact that the combination of TESPT and TWEEN-20 can enhance the dispersion of nano-SiO 2 particles and enhance the interfacial contact in the EPDM/SBR nanocomposites helps to explain these kinds of results.Also, the modified nanosilica filler filled EPDM/SBR composites have a lower EAB, indicating an improvement in the dispersion of SiO 2 nanoparticles in the EPDM/SBR rubber matrix.

Tear Strength
The tear strength (TAS) is presented in Fig. 8. TAS increased as the amount of nanosilica increased.As seen in Fig. 8, the hydroxyl groups on the surface of the nano-SiO 2 particles react with TESPT and TWEEN-20, raising the TAS of EPDM/SBR composites in comparison to EPDM/SBR composites filled with unmodified nano-SiO 2 filler.The

Hardness
Hardness is a term used to describe the rubber's resistance to reversible deformation by a hard indentor and is frequently used as a quality assurance metric.Nano-SiO 2 and modified nano-SiO 2 filler filled composites have an impact on the hardness of EPDM/SBR nanocomposites, as shown in Fig. 9.The hardness levels for all compounds range from 59 to 71 Shore A units.One of the crucial mechanical characteristics of the rubber compounds studied in this research is hardness, which changes according to the amount of nanosilica and modified nanosilica in the composite EPDM/SBR.Hardness increased together with the concentration of nanosilica.The hardness of modified nanosilica filler filled EPDM/SBR nanocomposites are clearly increased compared with unmodified nanosilica filler filled composite.The physical crosslinking formed by the mixing of rubber compounds and chemical  crosslinking formed during curing process, resists the deformation of rubber composite.The degree of crosslinking of rubber compound has a great impact on the hardness.To create a hard material, the rubber chains are indefinitely fixed to the surface of the nanosilica.The less active number of hydroxyl groups on the surface of nanosilica in the EPDM/ SBR-modified nanosilica, possibly improved the crosslinks and in turn increased the hardness of the nanofiller-rubber nanocomposites.

Rebound Resilience
As compared to its energy prior to impact, the indentor's energy after impact is given as a percentage, and this ratio is known as rebound resilience.Figure 10 shows the rebound resilience of nano-SiO 2 reinforced EPDM/SBR rubber composites.When the nanosilica content increase, the rebound resilience decrease.Hence, rebound resilience is directly proportional to the elasticity of composites; results evidently show that the nanosilica reduces the elasticity of the composites.This observable fact has caused the decreased rebound resilience for EPDM/SBR composites.The robustness reduced by roughly 13 units in modified nanosilica filled composites when the modified nanosilica was added from 2 to 10 phr.Maybe this is because the value of hardness has increased, which has caused the value of rebound resilience to decrease.Hardness and rebound resilience were discovered to be inversely related by Vishvanathperumal et al. [34].The rebound resilience was reduced when a high hardness was attained because there were more points of slippage between the reinforcement and the elastomeric matrix and because the reinforcing ingredient tended to clump together so that particles touched rather than being completely embedded in the polymer matrix.

Abrasion Resistance
Rubbers are frequently strengthened by adding reinforcing fillers to the polymer matrix to boost their resistance to abrasion.According to the hypothesis, volume is removed when an abrasive slides across a solid surface, and the wear mechanism is dependent on the material's hardness.A composite's effective hardness is increased when hard, inelastic fillers are included, which lessens the amount of material loss.
The abrasion loss of nanosilica reinforced EPDM/SBR rubber nanocomposites is shown in Fig. 11.The relative volume loss has been taken into account when analysing the abrasion resistance (AR) of EPDM/SBR nanocomposites.A stronger AR is indicated by a smaller volume loss value, and vice versa.The EPDM/SBR-nanosilica composite

Compression Set
A rubber material's capacity to regain its original thickness under extended compressive pressures at a specific temperature and deflection is measured by compression set.The composites are compressed by 25% at different temperature (23 °C, 70 °C and 100 °C) for 1 day and at fixed temperature (23 °C) for 1 to 3 days.The compression set for the EPDM/SBR composite is shown in Table 3. Compression set increases with increase of nanosilica content.Modified nanosilica filler filled EPDM/SBR nanocomposites showed a slightly higher compression set than did nanosilica filler filled composites.Because modified nanosilica filler filled EPDM/SBR composites had superior crosslinking density than unmodified nanosilica filler filled EPDM/SBR nanocomposites, the compression set was higher.Unmodified nanosilica filler leads in more hydroxyl groups on the surface of nano-SiO 2 , which may lead to comparably less crosslinks in the polymer network and, as a result, greater compression set in the case of nanofiller filled rubber nanocomposites.While in the case of modified nanosilica filler filled EPDM/SBR composites, resulting in a small number of hydroxyl groups on the surface of nanosilica, which could lead to reduced restriction in polymer chain movers and as a result higher compression set.Because more crosslinks between the reinforcement material and polymer matrix in the elastomeric chains are broken as the allotted time and days grow, the compression set increases.Rubber composites in a permanent set known as compression set.Therefore, incorporation of unmodified nanosilica or modified nanosilica in this study with resultant increased compression set.

Crosslinking Density
Figure 12 displays the crosslinking density of unmodified and modified nanosilica as determined by the immersion method.The crosslinking density of EPDM/SBR nanocomposites, increased as the content of nanosilica increased in the system.The crosslinking density is clearly higher for nanocomposites including modified nanosilica, as seen in  Fig. 12.The crosslinking density dropped when unaltered nanosilica was added to the composites.It demonstrates that the hydroxyl groups on the nanosilica's surface prevented the rubber chains from crosslinking.It continued to be aggregated, which decreased the amount of active hydroxyl groups on the surface of the nanosilica that could cross-link with rubber molecules.

Swelling Resistance
Generally, the swelling characteristic of polymer composites is closely correlated to the interface property between elastomeric matrix and nanofiller material.The volume fractions of polymer in swollen composite influenced by interfacial interaction [56,57].On mole percent uptake (MPU) through composites, the effects of nanosilica concentration and solvent type were examined.When the content of nanosilica is increased, the MPU of the EPDM/SBR nanocomposites declines (Table 4).In the case of rubber compounds (without nanosilica filler concent), the MPU is high, whereas an upsurge in the nanosilica content, the MPU decreases.When a nanosilica or modified nanosilica is incorporated in the EPDM/SBR nanocomposites, the solubility of nanocomposites are controlled up to the uptake stage.These composites behave as more degree of crosslinks involved in the rubber chains.The reduction in solubility or decrease in mole percent uptake is due to the involvement of physically entangled and more crosslinks between rubber matrix and filler, which is found to be less uptake of solvents in toluene.Comparing the MPU of the EPDM/SBR nanocomposites, the modified nanosilica filler filled EPDM/SBR composites undergoes less mole percent uptake than unmodified nanosilica filler filled EPDM/ SBR composites indicating less reactive site on surface of nanosilica and more crosslinking of nanosilica, which has the TWEEN-20 and TESPT is covered the nanosilica.The mole percent uptake of other solvents (n-pentane, n-hexane, n-heptane, n-octane, benzene, xylene, mesitylene, dichloromethane, chloroform and carbon tetrachloride) also follows the similar trend as that of the MPU of toluene.The MPU of modified nanosilica filled composite is lower than that of unmodified nanosilica filled composites.The modified nanosilica filler filled composites exhibits improved swelling resistance.

Morphology
From FESEM analysis it was clear that the nanosilica with a particle size of 30-50 nm in diameter was prepared which was almost in spherical in shape and was shown in Fig. 13.The tensile performance of rubber nanocomposites are significantly influenced by the silica nanoparticle dispersion in the matrix of EPDM/SBR.Figure 14a-b displays the morphology of the rubber nanocomposites on the tensile fracture surface.From the Fig. 14a, with the increase of nanosilica, most of the nanosilica particles were still in a nanodispersed state.In addition, the creation of hydrogen bonds between the silanol groups on the nano-SiO 2 surface causes the unmodified nanosilica particles to be nonuniformly disseminated in the rubber matrix with agglomerates.In contrast, practically all of the silanol groups on the surface of the nanosilica were reacted after being changed, causing the nanosilica particles to compact with the EPDM/ SBR matrix and become evenly distributed in EPDM/SBR nanocomposites, as showed in Fig. 14b.To put it another way, TWEEN-20 may result from the grafting of nanosilica surfaces into the molecular chains of rubber matrix, which enhances the compatibility of the rubber matrix and nanofiller in the composite and subsequently encourages the nanodispersion of nanosilica in the rubber matrix.In comparison to Fig. 14a, Fig. 14b demonstrates a significant improvement in the dispersion of SiO 2 nanoparticles in the EPDM/SBR matrix and a significant reduction in the size of silica nanoparticle agglomerates.One of the key reasons for the improvement in mechanical characteristics is due to this.

Conclusions
Ethylene-propylene-diene monomer/styrene-butadiene rubber nanocomposites was prepared using modified nanosilica and its properties (cure characteristics, abrasion resistance, mechanical behavior, compression set, and swelling resistance) were compared with unmodified nanosilica filler filled composites over a range of content.According to mechanical properties result, nanosilica was improved abrasion resistance, tensile and tear strength, elongation at break, 100% modulus, and hardness.So far, as the amount of nanosilica rose, rebound resilience dropped while swelling resistance increased.The values of torques and CRI increased while times decreased with the increment of nanosilica particles content.Modified nanosilica particles filler filled composites showed higher mechanical properties and swelling resistance compared to unmodified nanosilica filler filled composites.Because of this, TWEEN-20 can improve the dispersion of nanosilica in EPDM/SBR nanocomposites, and TESPT was used to create the chemical interface between nano-SiO 2 and rubber matrix.This results in the best dispersion of nanosilica in the EPDM/ SBR matrix due to the synergistic effects between TESPT and TWEEN-20.

Table 2
Cure behaviours of modified and unmodified nanosilica filler filled EPDM/SBR nanocomposites

Table 3
, resulting in stronger chemical linkages between the two phases.The increased number of crosslinks in polymer chains and improved polymer network are what cause the lower volume loss in the modified nanosilica filler filled EPDM/SBR composites.

Table 4
MPU for different solvents of nanocomposites