Accepted Manuscript

Torsional, Tensile and Structural properties of Acrylonitrile-Butadiene-StyreneClay Nanocomposites

Priyanka Singh, Anup K. Ghosh

PII: S0261-3069(13)00888-1DOI: http://dx.doi.org/10.1016/j.matdes.2013.09.036Reference: JMAD 5867

To appear in: Materials and Design

Received Date: 27 April 2013Accepted Date: 14 September 2013

Please cite this article as: Singh, P., Ghosh, A.K., Torsional, Tensile and Structural properties of Acrylonitrile-Butadiene-Styrene Clay Nanocomposites, Materials and Design (2013), doi: http://dx.doi.org/10.1016/j.matdes.2013.09.036

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Torsional, Tensile and Structural properties of Acrylonitrile-Butadiene-Styrene Clay Nanocomposites

Priyanka Singh and Anup K. Ghosh Centre for Polymer Science and Engineering

Indian Institute of Technology Delhi, New Delhi, India Corresponding email: akghosh@polymers.iitd.ac.in

Telephone no.: +91-11-26591424

Abstract

Torsional and tensile behaviour of Acrylonitrile-butadiene-styrene (ABS)-clay nano-

composites have been investigated and correlated with morphological and rheological

characterizations. Nano-composites of ABS are prepared by melt compounding with different

loading levels of nanoclay (Cloisite 30B) in a twin screw extruder and have been

characterized in terms of torsional, axial and impact behaviour for their application in external

orthotic devices. Tensile stress strain curve of nanocomposites are investigated to quantify

resilience, toughness and ductility. Torque values of the nanocomposites are observed under

torsion (10-90°) and compared with that of neat ABS. Performance of ABS under torsional

load improved by addition of nanoclay. Both modulus of elasticity and rigidity are found to

improve in presence of nanoclay. State of dispersion in nano-composites is investigated using

conventional methods such as transmission electron microscopy (TEM), x-ray diffraction

(XRD), as well as by parallel plate rheometry. Addition of clay exhibits shear thinning effect

and results in increase in storage modulus as well as complex viscosity of the

nanocomposites. Zero shear viscosity rises tenfold with 1-2% addition of nanoclay, indicating

the formation of structural network. It is found that state of dispersion of nanoclay governs the

torsional and mechanical properties in ABS-clay nanocomposites.

Keywords: Acrylonitrile-butadiene-styrene; Nanocomposites; Torsion; Ductility; Rigidity

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1. Introduction

Acrylonitrile-butadiene-styrene (ABS) and their nanocomposites need extensive investigation

for development of products which include structural components in automotives, enclosures

of electrical and electronic parts, home appliances as well as orthotic devices in order to prove

the durability and load carrying capacity. Deformation in such parts can be produced by the

forces caused by stretching, compressing, twisting and bending. Among these, twisting or

torsion is an important force which can produce stresses in application such as hinge joint for

orthotic leg. Conventionally torsional behaviour of the structural parts made out of metals and

ceramics are investigated [1-3]. But in current research scenario there is still scanty

information available for response of polymeric material under torsional deformation. Thus, it

is essential to establish torsional response comprehensively to establish performance

properties of polymer and their nanocomposites. Torsional measurement is not as universal as

tensile and flexural measurement. Torsion is introduced into a bar when it is subjected to a

twisting moment and the angle of twist (φ) is calculated using equation 1[4].

TL

JGϕ = (1)

Where T is torque, L is gauge length, J is polar moment of inertia and G is torsional rigidity.

Polymer is limited for engineering applications due to low modulus of resin, poor thermal

resistance and toughness-stiffness balance. Application profile of ABS can be broadened by

reinforcing it with nanoclay as it is known to enhance the property of matrix at very low filler

loading and thus, broadens the window of properties [5, 6]. Nanoclay is mainly layered

silicates, having sheet like platelets of about 1 nm thickness and 30 to several microns in

length and width. These platelets have very high tensile modulus (170 G Pa) relative to that of

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polymers (>1GPa) [7] and these are further modified before being added to organophilic

polymer matrices [8].

Additionally, dispersion states in the nano-composites lead to different responses for the

applied stresses and need to be evaluated. To establish the structure, TEM is a popular method

to understand the state of dispersion of platelets in nano-composites but the size of the sample

used may not represent the total volume, and the sample preparation for TEM requires special

expertise which makes the whole method costly and time consuming [9]. Alternatively,

rheology has evolved as a method to characterize the clay dispersions in polymer nano-

composites as rheological response of nanocomposites depends on the factors such as filler

size, aspect ratio and orientation, filler loading and interaction between polymer and filler

[10]. Wagener et al. have discussed the approach to quantify shear thinning behaviour so as to

compare exfoliation and nanoscale dispersion in nanocomposites [9].

Polymer clay nano-composites have gained interest and popularity as a tool to develop new

materials. ABS clay nanocomposites have also been studied by several researchers. ABS clay

nanocomposites are generally prepared by processes such as melt-mixing, emulsion and in-

situ polymerization by different researchers [11-19]. The preparation of ABS clay nano

composites by melt blending have been reported by Wang et al. [20]. In another study three

different types of clay i.e. Cloisite 30B, Cloisite 25A and Cloisite 10A are used to prepare

ABS clay nanocomposites by solution blending. Cloisite 30B was found thermodynamically

more favourable when compared with Cloisite 20A and Cloisite 15A [14, 21]. Most of the

reports on ABS-clay nanocomposites are focused on thermal stability and flame retardancy [8,

15-17, 21].

Present work thus, aims to critically analyze the effect of clay on the properties of ABS when

it is subjected to torsional, axial, bending and dynamic load. Rheological evaluation has been

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used as a tool to establish the structure and correlate with TEM and XRD observation. In

addition, the effect of clay on the dynamic mechanical behaviour and thermal stability of ABS

has also been studied.

2. Experimental Details

2.1 Materials

Acrylonitrile-Butadiene-Styrene (ABS) resin containing styrene 60-54 %, Butadiene 17-21 %,

Acrylonitrile 23-25 % by weight was procured from Bhansali Engineering Polymers Ltd,

India with the trade name Abstron and grade HI40B. Organically modified clay (Na+-

montmorillonite) was chosen for the study and supplied by Southern Clay Products, USA

under the trade name Cloisite 30B.

2.2. Preparation of ABS clay nano-composites

ABS-clay nanocomposites were prepared by melt mixing using THERMOSCIENTIFIC

(Prism Eurolab 16) twin screw extruder (L/D of 40, barrel diameter of 16mm, maximum

speed of 1000 rpm and maximum torque of 12 Nm). All materials were pre-dried for 4 hours

at 75°C under vacuum. The nanocomposites were prepared maintaining the temperature

profile of 200-230 °C and at the screw speed of 200 rpm, generating 60-70 % torque. The

continuous strands from the extruder were pelletized and vacuum dried before injection

moulding. L&T DEMAG injection moulding machine (Model: PFY40-LNC4P) were used to

prepare test specimens as per ASTM standards for different tests at 200-230 °C. Four

compositions were prepared with different clay loading as given in Table 1.

2.3. Characterization of ABS clay nano-composites

2.3.1. Rheological properties

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The melt rheological measurement was done using Bohlin C-VOR rotational rheometer

(Malvern Instruments Limited, UK) with the parallel plate geometry. Samples (disc shape)

were prepared by compression moulding of dimension 25 mm in diameter and 1mm in

thickness. Samples were initially tested using an amplitude sweep to find out the linear

viscoelastic region (LVR). The frequency sweeps between 0.1 to 100 Hz at 0.1 strain unit

were carried at 170 °C.

2.3.2. Torsional properties

Torsional testing was carried out using MCR302 DMTA equipment from ANTONPAAR.

The DMTA system consisted of a rheometer combined with the convection temperature

devices CTD 450 and solid rectangular fixtures. Schematic of the torsional fixtures is

presented in Figure 1. One of the clamps generates torsional movement between 10-100° All

the experiments were carried out at 70°C using injection molded sample having dimension of

14 mm in length, 9 mm in width and 1.5 mm in thickness. Torque and rigidity modulus were

compared for ABS and its nanocomposites as a function of torsional deflection.

2.3.3. Mechanical testing

Samples were subjected to load in tensile and flexural mode using ZWICK Z010. ASTM:

D638 was followed to perform tensile test at room temperature at a speed of 50 mm/min.

Flexural test was done as per ASTM: D790 method at a speed of 13.5 mm/min. Notched izod

impact strength was measured as per ASTM: D256 on a Ceast impact testing machine.

2.3.4. Thermal analysis

ABS clay nano-composites were investigated by thermo gravimetric analysis (TGA),

performed with a PERKIN ELMER Pyris 6 (TGA) instrument under nitrogen atmosphere at

the rate of 20 °C/min, from 25 to 750 °C. Differential scanning calorimetry (DSC) was

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performed using DSC 7 instrument (Perkin Elmer) at a scan rate of 10 °C/min to determine

the effect of Cloisite 30 B on glass transition temperature.

2.3.5. Morphological Characterization

The state of dispersion of clay platelets in the composites was studied by means of

transmission electron microscopy (TEM). Freshly cut glass knives with cutting edge of 45°

were used to prepare the cryo-sections of 50 nm thickness by using a Leica Ultracut UCT

microtome. JEOL-2100 electron microscope (Tokyo, Japan) having LaB6 filament and

operating at an accelerating voltage of 200 kV was used. Evaluation of dispersibility of clay

in ABS resin matrix was investigated using XRD technique and basal spacing of clay layers

was obtained using Bragg’s rule. X ray diffraction experiments were performed at room

temperature on X-ray diffractometer (PW 3040/60 X’PERT PRO PANALYTICAL,

Netherland), (40 kV, 30 mA) with Cu (λ=1.54 Ǻ)

3. Results and discussion:

3.1. Rheological characterizations

Figure 2 shows the amplitude sweep curves for ABS and its clay nanocomposites. Viscosity

plateau (LVR) is limited up to 10% deformation of amplitude which indicates that alignment

of clay is unperturbed in this range. Dynamic frequency sweep test has been carried out in

LVR range (γ = 0.01) to study the microstructure of nanocomposites. The plots of storage

modulus, complex viscosity and loss tangent versus angular frequency are shown in Fig. 3 a,

b and c respectively. The data at low region of frequency reflect the effect of clay loading and

state of dispersion of clay on visco-elastic properties of ABS clay nanocomposites. Fig. 3a

shows monotonous increase in storage modulus with frequency for ABS and its nano-

composites. The observed enhancement of storage modulus with increase in clay content at

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low frequency is due to confinement effect and inter-particle interaction. At low frequency,

the change of storage modulus is significant which subsequently narrows down with increase

in frequency. The larger time for untangling of chain entanglements results in higher

relaxation and lower value of storage modulus at lower frequency while in case of higher

frequency, chain entanglements do not get enough time to relax resulting in higher modulus.

Storage modulus of all composition changes with frequency but the slope decreases with clay

loading which may be due to the formation of network structure of clay platelets in polymer

matrix (Table 1). It is also indicative of more solid like behaviour. It is observed from Fig. 3b

that complex viscosity decreases with frequency thus, representing shear thinning behaviour

of ABS nanocomposites. The flow curves are fitted to Power law expression to find out shear

thinning component. To determine Power law constant a plot of log (η) and log (ω) was made

and the slope of the curve provides the shear thinning component which gives the semi-

quantitative measurement of nano-dispersion of samples[9]. Shear thinning component of the

samples in low shear rate range has been presented in Table 1. ABS with 2% clay loading

shows maximum shear thinning which is indicative of presence of well dispersed nano-scale

platelets in polymer matrix. There is substantial increase in complex viscosity for all clay

filled nano-composites which can be explained on the basis of resistance of flow of ABS

matrix imposed by intercalated, exfoliated or aggregated clay layers. Table 1 lists the zero

shear viscosity (η0) of ABS and its nanocomposites. It can be observed that there is tenfold

rise in η0 between 1 to 2 percent clay content indicating the formation of structural network.

Fig. 3c represents loss tangent (tan δ) plot versus angular frequency which signifies the ratio

of lost energy to stored energy in cyclic deformation (tan δ=G”/G’). It is reported that

polymer melt shows negative slope in such curves while in case of solids, the slope is

positive. Transition in slope from negative to positive can be identified as gel point i.e. melts

to solid transition point [22]. The tan δ plot of neat ABS shows negative slope over the whole

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frequency range and it is also increases with increasing frequency. After addition of clay, tan

δ value becomes less frequency dependent as shown by decrease in slope. At high frequency

terminal region, samples with 2, 4 and 6 wt % clay content show positive slope and at low

frequency terminal region positive slope can easily be identified in case of sample with 4 wt%

nanoclay followed by some plateau region. The change in slope can be considered as

transition point from melt like behaviour to solid like behaviour which can be either due to

some interaction between exfoliated, intercalated or aggregated clay layers and polymer,

hindering mobility of polymer chain or formation of three dimensional structural networks.

Validity of above observation can be further supported by Han, Cole-Cole plot and van-Gurp

Palmen plots [23, 24]as shown in Fig. 4a, b and c respectively. Fig. 4a represents the Han

plots of G’ and G” for ABS and its nano-composites which is used to investigate

microstructure. ABS with more than 2 % clay loading shows high value of storage and loss

modulus. The ABS clay-nano composites do not superimpose forming master curve which

indicates the presence of heterogeneous structure in clay filled system. The Han plots of

nanocomposites shifted to higher modulus side which can be attributed to the reinforcement

effect of clay due to increase in surface area as clay gets dispersed. Fig. 4b shows Cole-Cole

plots of complex viscosity versus dynamic viscosity for ABS and its nanocomposites. Cole-

Cole plot is generally used to find out structural variation in heterogeneous polymeric

materials. The plots of ABS and its clay nano-composites do not fall on single master curve

that indicates presence of different structures at different nanoclay content. The change in

slope from 1.25 to 1.85 is due to the inter-phase interaction between ABS matrix and clay.

Nature of the Cole-Cole plots is generally affected by restriction in the mobility of ABS due

to confinement effect of clay. The plots are observed to be longer for ABS nanocomposites

due to formation of filler-filler networks. The structure of nano-composites drastically retards

the long range motion of molecule resulting in long relaxation process by increasing elasticity

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to viscosity ratio in the ABS nano-composites. Fig. 4c represents the plots of tan delta versus

complex modulus for ABS and its nano composites at 170 °C to determine percolation

threshold. The plots are known as van Gurp Palmen Plot and are accepted method to

determine rheological percolation of nano composites[24]. Decrease in phase angle with

modulus is very significant at percolation threshold and signifies the increase in elastic

behaviour. At lower complex modulus, the phase angle value reduced significantly by the

incorporation of nanoclay. As seen from the graph, van Gurp Palmen plots of ABS

nanocomposites establishes the onset of percolation between 1to 2 wt % of clay.

3.2. Torsional Properties

In these experiments material is subjected to twisting moment in dynamic mode till failure.

The torque, degree of rotation and modulus of rigidity are measured. Effect of nanoclay on the

torsion behaviour of ABS has been observed and evaluated as torque vs. deflection plot which

is presented in Fig 5. Under torsional load, ABS and its nanocomposites show yielding

behaviour followed by failure of the sample. It can be inferred from the graph that all the

specimens under torsion deform first elastically followed by the plastic deformation. It is

further observed that high value of torsional force is required as the degree of rotation

increases to the yield point. ABS shows yield at around °36 of deflection. At lower degree of

deflection i.e. up to °32 , all the nanocomposites except ABS with 1wt % clay loading show

better resistance to torsion. This may be due to inability to form regular structure which is

critical for filler to impart strength to the matrix. At a concentration (around percolation),

where clay is exfoliated and intercalated, polymer-filler and filler-filler interaction increases,

leading to a network like structure and strengthening of the matrix. Beyond 4 % of clay

content, agglomerated clay inclusions in the structure provide the stress concentration sites

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and weaken the overall matrix. Modulus of rigidity is calculated as the ratio of shear stress to

shear rate at °25 of deflection and is discussed in later section.

3.3. Mechanical properties.

The mechanical properties of ABS-clay nano-composites are shown in Fig. 6. It is observed

from the figure that addition of Cloisite 30B to ABS increases the stiffness (modulus) of

nano-composites without any significant effect on tensile strength. Tensile modulus increased

up to 40 % by the addition of 6 wt % nano clay while the increase in case of flexural modulus

is 23%. This may be due to the possibility of alignment of clay in the direction of flow during

moulding.

Stress-strain curve is integrated to calculate the total energy (toughness) of the specimen.

Ductility is measured in terms of ductility index which is expressed as ratio of deflection or

absorbed energy at failure and yielding. Many researchers have used the concept of ductility

to define the behaviour of reinforced polymers [25, 26]. Ductility Index (DI) is calculated

using the following relationship,

Total energy-Yield energyDI=

Yield energy (2)

Total energy represents the total area under the stress-strain curve and yield energy represents

the area up to yield stress. Ductility index indicates the relative amount of energy used to

propagate deformation after the peak load. Lower value of ductility index shows that total

absorbed energy is being used to initiate plastic deformation which results in ultimate fracture

of the material but in case of ductile material amount of energy absorbed is being used to

initiate and propagate the deformation. As a rule of thumb, a ductility index less than 45%

represents brittle fracture. The properties that are used to define the toughness and the

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ductility behaviour are presented in a radar chart in Fig. 7. Resilience energy of ABS and its

clay nanocomposites remains unchanged while toughness which is calculated by the area

under stress strain curve decreases with addition of nanoclay. The decrease is very prominent

at higher loading because at higher loading filler-filler interactions predominate creating sites

for failure. Ductility index and impact strength of ABS clay nanocomposites follow the same

trend. It is clear from the stress-strain curve that ABS and its nano-composites with 1 and 2 wt

% clay loading show the necking regions after yielding while with 4 and 6 wt % clay loading

the stress value drops drastically till the fracture of samples. Ductile behaviour of nano

composites is observed up to 4 % of clay. At higher loading unreacted stacks of clay is

expected to be present which form critical cracks leading to brittle fracture. On the other hand

dispersed (exfoliated/intercalated) clay layers initiate large no of small and stable voids which

allow further matrix deformation between the particles.

3.4. Thermal Analysis

Thermograms of ABS nano-composites are compared with that of pure ABS to determine the

thermal stability. The onset of degradation temperature is defined as the temperature at which

5 % weight loss occurs. Onset degradation temperature and inflexion point are presented in

table 2. Onset degradation temperature of all nano-composites shifted to higher temperature

by 4-14 °C compared to that of pure ABS, indicating improved thermal stability. Dispersed

clay enhances the thermal stability of ABS as it acts as barrier against heat and diffusion of

atmospheric oxygen into the material which inhibits the oxidative attack into the matrix.

Similar observation has been reported by Kim et al [27] and Patino-Soto et al [21]. Dispersed

clay platelets also restrict the flow by the increase in viscosity of ABS. The ABS nano-

composites with increased viscosity can shield the diffusion of oxygen into the matrix. It is

found that the onset degradation temperature is highest for ABS nanocomposites containing 2

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wt % nanoclay. This observation can be explained by considering the fact that the state of

dispersion in ABS matrix affects the barrier property of the nanocomposites which is further

responsible for thermal stability of the system. Hence improved thermally stability of ABS

with 1 and 2% of nanoclay can be correlated with state of dispersion.It is observed that

inflexion temperature of all nano-composites increase linearly by addition of nano-clay which

may be due to reorientation of clay at higher temperature as viscosity of ABS decreases with

increase in temperature.

From the differential scanning calorimetry, the glass transition temperature of ABS due to

styrene phase is found to be at 104 °C and that due to acrylonitrile phase is observed at 136

°C (Table 2). After the addition of nano-clay, Tg of styrene phase remains almost constant but

Tg of acrylonitrile phase decreased by 6 °C, indicating relatively higher interaction of clay

with acrylonitrile phase.

3.5. Morphological Characterization:

X-ray crystallography is conventionally used to analyze the crystal structure of layered

silicate and interlayer spacing of clay layers in polymer nano-composites. Fig. 8(a) comprises

X-ray diffractrograms of neat ABS and Fig. 8(b) shows the same of ABS clay

nanocomposites. The clay shows peak at an angle of 4.83° which correspond to inter layer

spacing of 18.29 nm (Table 1). ABS is not showing any peak in 2θ range of 2-40° but one

hump can be observed due to its amorphous nature. Characteristic peak of Cloisite 30 B

shifted to lower value of 2θ for the nanocomposites due to increased interlayer spacing of clay

layers in the ABS clay nanocomposites. This shows that polymer chains could make their way

between the clay galleries during melt compounding but clay platelets retained some ordered

structure which signifies the intercalated structure. In XRD, ABS with 1 wt % clay loading

shows a peak shift and ABS with 2 wt % clay loading registers a peak shift with a hump.

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Thus, in case of higher clay loading (4% and 6 wt %) we can observe a shifted peak with

hump and second broad peak which shifted to little higher 2θ value is observed. Thus, ABS

nanocomposites at lower loading consist of the intercalated structure and the hump signifies

the presence of clay stacks of different thickness (mix layering) while a broad peak shows the

presence of mild dispersions in the stack of clay while retaining its original structure.

Generally it is considered that absence of peak is due to exfoliated structure and peak shift

towards lower value of 2θ is due to intercalated structure. It cannot be true for all the cases as

several factors such as clay dilution, peak broadening and preferred orientation are mentioned

to make XRD analysis of polymer nanocomposites susceptible to error[28]. In general,

complete exfoliated structure is a rare phenomenon as polymer nanocomposites show mixed

morphology which includes intercalated and exfoliated structures[28]. As discussed earlier,

ABS clay nano-composites also show the mix morphology but at higher clay loading some

unreacted clay remain which can be comprehended as there is some saturation point beyond

which concentration of unreacted clay increases. The evolved morphologies of ABS clay

nanocomposites have been investigated using TEM and are presented in Fig. 9. The dark lines

in the micrographs correspond to silicate layers of the nano-clay. Mix morphology is further

confirmed by TEM images of ABS nanocomposites. In case of mix morphology, XRD can

only detect intercalated portion of morphology by increase in d spacing, while TEM

micrographs show the coexistence of intercalated multilayer and exfoliated silicate layer.

Typically rubber particles appear as the holes in the SAN matrix. It can be inferred that the

clay layer is not in butadiene phase and resides mostly in SAN phase of ABS nanocomposites.

Presence of stalks of different lengths and thickness has been registered for different

compositions. Aspect ratio of clay tactoids is calculated by taking the measurement of length

and thickness manually using Image J software. Number average aspect ratio for every

composition is shown in table 1.Histograms of aspect ratio of clay stalks are also presented in

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Fig. 9 besides the TEM micrographs. Exfoliated –intercalated morphology predominates at

lower clay loading which is already reported for polymer nanocomposites[29].

3.6. Correlation of torsional, mechanical and rheological properties

Figure 10 depicts effect of clay on torsional, morphological and rheological properties. The

dependency of normalised storage modulus (G’/G’p) as function of nanoclay content is

presented where G’ is storage modulus of nanocomposites at 0.1 Hz frequency and G’p is

storage modulus of ABS at the same frequency. In can be comprehended that the G’/G’p is

found to increase with the addition of nanoclay. The steep increase of about three fold

between 1 to 2 % clay content is due to the presence of network like structure. It is further

observed that torsional rigidity of ABS nanocomposites increased by the addition of clay. For

composites with 2 wt % of clay there is steep change (31%) in rigidity modulus which can be

due to confinement effect of well dispersed clay network. Further increase in clay content

results in decrease in torsional rigidity. ABS with low clay loading shows highest value of

aspect ratio due to dispersion of clay while at higher loading (6%), agglomeration occurs.

This results in low aspect ratio of clay causing decrease in ductility and torsional rigidity of

ABS clay nanocomposites. Based on the observation as above, it is inferred that ABS with 2

wt % of clay loading performs better in terms of its rigidity, stiffness and ductility.

4. Conclusions

The present study is an attempt to evaluate torsional properties of ABS clay nanocomposites

and to correlate with structural properties. The rheological studies depict the percolation

between 1 to 2 % of clay percentage and the formation of network like structure which is

responsible for improved mechanical properties. Addition of clay leads to monotonous

increase in complex viscosity and storage modulus. Zero shear viscosity increases tenfold

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between 1 to 2 % indicating the formation of structural network. Han plots register the

different morphological states for different clay loading while van Gurp Palmen plots support

the existence of percolation threshold between 1 to 2 % of clay content. Property of clay

reinforced ABS nanocomposites has been evaluated by thermal stability, toughness, stiffness,

ductility, impact strength and torsional rigidity. Torsional resistance and rigidity modulus of

ABS are improved by addition of clay. Further, response of ABS clay nanocomposites under

torsional deflection depends on structure of nanocomposites. It is also observed that the

resilience of the matrix is not affected by the addition of clay as polymer is well intercalated

or exfoliated between the clay galleries. At lower loading, clay dispersion does not change the

inherent toughness of the matrix while at higher loading material behaviour changes to brittle

nature indicating that clay acts as stress concentration points. At lower clay loading, mixed

(exfoliated-intercalated) morphology is proposed while at higher loading intercalated-

exfoliated structure exists with some of unperturbed clay. Hence, for structural applications

with torsional resistance, ABS with 2 % of clay loading is proposed to deliver the balance of

rigidity-stiffness-toughness to the product.

Acknowledgement

Author (PS) acknowledges the research fellowship from the Ministry of Human Resource

Development, Govt. of India. We acknowledge the research facility provided by the

AntonPaar, India

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[21] Patiño-Soto AP, Sánchez-Valdes S, Ramos-deValle LF. Morphological and Thermal Properties of ABS/Montmorillonite Nanocomposites Using ABS with Different AN Contents. Macromol Mater Eng. 2007;292:302-9. [22] Joshi M, Butola BS, Simon G, Kukaleva N. Rheological and Viscoelastic Behavior of HDPE/Octamethyl-POSS Nanocomposites. Macromolecules. 2006;39:1839-49. [23] Barick aK, Tripathy DK. Nanostructure morphology and dynamic rheological properties of nanocomposites based on thermoplastic polyurethane and organically modified montmorillonite. Polym Bull. 2010;66:1231-53. [24] Gurp Mv, Palmen J. Time-temperature superposition for polymer blends. Rheol Bull. 1998;67:5-8. [25] Maghsoudi AA, Bengar HA. Moment redistribution and ductility of RHSC continuous beams strengthened with CFRP. Turkish J.Eng. Env. Sci. 2009;33:45-59. [26] Briscoe BJ, Fiori L, Pelillo E. Nano-indentation of polymeric surfaces. Journal of Physics D: Applied Physics. 1998;31:2395-405. [27] Kim H-S, Park BH, Choi JH, Yoon J-S. Preparation and mechanical properties of acrylonitrile-butadiene-styrene copolymer/clay nanocomposites. J Appl Polym Sci. 2008;107:2539-44. [28] Nwabunma D, Kyu T. Polyolefinic composites. John willy and Sons, New Jersy; 2008. [29] Dayma N, Jaggi HS, Satapathy BK. Post-yield crack toughness behavior of polyamide-6/polypropylene grafted maleic anhydride/nanoclay ternary nanocomposites. Mater Des 2013;49:303-10. Figure 1: DMTA system consists of and solid rectangular fixtures and schematic of torsional deflection

Figure 2: Amplitude sweep test of ABS and its nanocomposites

Figure 3: Dynamic frequency sweep test of (a) storage modulus (b) complex viscosity (c) damping factor for ABS and its clay nanocomposites

Figure 4: (a) Han plots of storage modulus (G’) versus loss modulus (G”), (b) Cole cole plots of complex viscosity versus dynamic viscosity, (c) Van Gurp –Palmen plots of phase angle (δ) versus complex viscosity for ABS nanocomposites

Figure 5: Torsional behaviour of ABS clay nanocomposites

Figure 6: (a) Tensile and (b) Flexural properties of ABS clay nanocomposites

Figure 7: Radar representation of different parameters related to ductility of ABS clay nano-composites

Figure 8: XRD of (a) ABS (b) ABS clay nanocomposites

Figure 9: TEM Micrographs of ABS nanocomposites ( a) ABS01NC ( b) ABS02NC (C) ABS 04NC (d) ABS06NC

Figure 10: Correlation of torsional, mechanical, rheological and morphological properties (AR=Aspect Ratio

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Table1: Rheological and morphological properties of ABS-clay nanocomposites.

Sample

Designation

ABS (wt. %)

Nanoclay (wt. %)

Shear

thinning

component

(0.1-1hz)

Zero shear

viscosity

(Pa. s)

2θ value

(°)

d spacing

(Ǻ)

Number Average Aspect

ratio (l/t)n

Cloisite 30B - - - - 4.831 18.29 -

ABS 100 0 0.45 4.98E+05 - - -

ABS01NC 99 1 0.46 9.24E+04 2.491 35.41 38.98

ABS02NC 98 2 0.22 3.30E+06 2.49 35.47 46.21

ABS04NC 96 4 0.26 1.67E+06 2.49 35.47 34.24

5.237 16.86

ABS06NC 94 6 0.35 2.36E+06 2.49 35.51 28.69

5.5 16.05

Table 2: TGA data and glass transition temperatures of ABS and its nanocomposites

Thermo-gravimetric data

Glass transition temperature(Tg) Sample

Designation Temperature at 5% weight

loss(°C)

Inflexion Temperature

(°C)

Styrene phase (°C)

Acrylonitrile phase (°C)

ABS 374 440 104.38 135.66

ABS01NC 383 442 104.45 131.25

ABS02NC 388 446 104.51 132.72

ABS04NC 378 446 105.67 131.30

ABS06NC 378 448 105.56 129.64

Figure1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Graphical Abstract (for review)

Highlights

1. Torsional behaviour of ABS and its nanocomposites is established

2. Rheology is used as a tool to investigate the structure development of ABS nanocomposites.

3. Effect of nanoclay on resilience, toughness and ductility of ABS nanoclay is quantified.

4. ABS clay nanocomposites is correlated with rheological, mechanical and torsional behaviour.