Thesis-2383-Ginil Mon S-Chemistry - Information and …shodhganga.inflibnet.ac.in/bitstream/10603/27890/8/08...supplied freely by Bhimrajka Impex Ltd., Chennai. H2 C l C H H2C n Chemical

63

CHAPTER III

MATERIALS AND METHODS

Blending of polymers provides deep inroads for advanced applications. In the

present work, a novel blend has been prepared by solvent blending of two immiscible

rubbers EPDM and neoprene in compatible proportions and further reinforced with clay

and graphite fillers. Curing is done by using peroxide curing agents. Clear specification

of the materials used, experimental parts and the mechanism of peroxide curing of EPDM

are discussed along with characterization of the materials.

3.1 Methodology

Polymerization is a process of reacting monomers together to form a polymer

chain or three-dimensional networks. Curing of polymers results in increase in strength of

the polymer so that it can be used in high-end applications.

Curing of polymers is a process which refers to the toughening or hardening of a

polymer material by cross-linking of polymer chains brought about by chemical

additives, ultra-violet radiation, electron beam or heat. In the present work, peroxide

curing is done. The peroxide curing of ethylene–propylene elastomer has been well

studied as a function of its composition (relative proportions of ethylene to propylene and

nature of the diene eventually present) [1-7]. The process proceeds as per the mechanism

in Scheme 1.

It is based on the thermal decomposition of peroxide molecules which results in

the formation of peroxy radicals (1). They can react with the polymer chains by

abstraction of labile hydrogens to produce macroradicals (2). Combination of these

64

macroradicals leads to crosslinking points between the chains (3). However, side

reactions (4),(5) and (6) are believed to compete with reaction (3) in the formation of

crosslinks.

RO OR 2RO

+ P + ROHPRO H-abstraction

2P P P Cross link

no Cross link

Peroxide decomposition

P + OR P OR

Scission

Disproportination

H2C

C

H2C

CH2

CH3

H2C

C

CH2

H2C

CH3

+

H2C

C

H2C

CH2

CH3

2

H2C

HC

H2C

CH2

CH3

H2C

C

HC

CH2

CH3

+

Scheme 1

Hydrogen-abstraction occurs preferentially from the more labile hydrogens in the

order, allylic>tertiary>secondary>primary functions. The reactivities of the radicals

produced are in the reverse order [4, 6]. In EPDM terpolymer, the diene is mainly

65

dicyclopentadiene (DCPD), 1, 4-hexadiene (HD) or ethylidene norbornene (ENB) which

is the monomer in the present study. In the absence of a diene moiety, the H-abstraction

occurs on the ethylene or the propylene sequence. The crosslinking of copolymer EPM is

still possible, but less efficiently. This is mainly due to scission reactions occurring on

tertiary radicals created by H-abstraction of the propylene sequence. Crosslinking and

chain scission are competing reactions whose relative effects depend on the composition

of the copolymer i.e. the relative proportion of ethylene to propylene sequences [6, 8].

HC

C

CH2

HC

HC

CH3

DCPD ENB HD

CH

H3C

The radicals can react with the double bonds either through allylic H-abstraction

or addition to the double bond, the later route being favored when the double bond is

terminal, whereas an internal double bond tends to react more via H-abstraction [6]. The

radicals produced by the addition reaction are quite reactive, so that they can, in the

absence of steric constraints, add to another terminal double bond (propagation) to

produce a crosslink without radical destruction, leading to high crosslinking efficiency

(>1) [9]. The addition of a radical to an internal double bond does not lead to a

propagation reaction because the steric constraints of 1, 2-disubstituted olefins limit their

tendency to polymerize. Such an addition would lead to abstraction of an allylic hydrogen

66

or reaction with another radical to produce a crosslink [6]. The resonance-stabilized

allylic radicals cannot give rise to propagation reactions; hence crosslinking efficiency is

less [9]. The ‘‘polymerizability’’ of the unsaturated moiety is determined by the position

of the double bond (internal or terminal), the number of allylic hydrogens, their

accessibility and the relative stability of the allylic radicals that have been formed [8].

Since ethylidene norbornene holds an internal double bond and five active allylic

hydrogens (the hydrogen on the double bridged carbon atom α to the double bond is

considered to be inert), the radicals should react more via the allylic H-abstraction route.

Indeed,it was shown that only about 25% of the crosslinking bonds arose from H-

abstraction on the methyl group [9] because the radicals cannot be stabilized by

resonance. Dikland [8] has compared the peroxide crosslinking efficiency of different

EPDM bearing diene moieties and showed that 1, 4-hexadiene is less efficient than

ethylidene norbornene though both the monomers bear five active allylic hydrogens and

an internal double bond. Hence, the mechanism of crosslinking via radical addition to the

double bond of ENB is an important route [8]. Moreover, a greater driving force for

addition is provided by a 1, 1, 2-trisubstituted substrate compared to a 1, 2-disubstituted

ethylene structure [6] which confirms the addition mechanism with ENB. The kinetics of

peroxide crosslinking has been studied as a function of peroxide substituent or

environment [2, 10]. From torque measurements, it has been shown that the rate-

determining step of the whole process is the peroxide decomposition step which is slow

compared to recombination or scission reactions. At moderate temperatures or peroxide

concentrations, the decomposition reaction globally follows a first-order reaction [7, 10,

11].

67

One disadvantage of the use of peroxide for crosslinking is the interference with

many antioxidants which act as radical scavengers leading to a reduction of the

crosslinking efficiency [12].

3.2 Materials

The materials used in the present study: two rubbers EPDM and neoprene to

prepare blends, dicumyl peroxide used as the curing agent for the rubber polymers,

toluene as the solvent, kaolinite and graphite as fillers were directly purchased and used

as such. Montmorillonite (MMT) was alkyl modified and then used as filler. Toluene is

the only organic solvent used throughout the work. Analar grade (AR) Toluene (C. No.

T78929) with 99.5% purity was obtained from NICE Chemicals, Cochin.

Tetradecyltrimethylammonium bromide was kindly supplied by Sisco Research

Laboratories, Mumbai, Sodium chloride was provided by Central Drug House, New

Delhi and Silver chloride was purchased from Merck India Ltd., India.

3.2.1 EPDM Rubber

EPDM (ethylene propylene diene monomer) rubber (M-class) a type of synthetic

rubber, is an elastomer classified (ASTM) under D-1418. The “M” class includes all

rubbers having a saturated chain of the polymethylene type. The diene currently used in

this study is ENB (ethylidene norbornene).

The EPDM rubber used for the study was 2Kg sample pack of NORDEL IP

4770R product of DOW Chemical Company supplied freely by Bhimrajka Impex Ltd.,

Chennai. The product which is in the form of pellets has ethylene content 70%, diene

68

4.9%, Mooney viscosity 70ML (at 125oC), typical molecular weight 200,000 (GPC Dow

test method) and density 0.88g/cc.

H2C

H2C

HC

CH3

H2C

CH

H3C

* *

p

q

r

Chemical Structure of EPDM with ENB

69

3.2.2 Neoprene Rubber

Neoprene is a family of synthetic rubbers that are produced by polymerization of

chloroprene. It contains chlorine atom within the chain. The Neoprene rubber used for the

study was 2Kg sample pack of NORDEL IP 4770R product of DOW Chemical Company

supplied freely by Bhimrajka Impex Ltd., Chennai.

CH2

C

Cl

C

H

H2C

n

Chemical Structure of Neoprene

70

3.2.3 Montmorillonite

Montmorillonite, a member of the smectite family, is a 2:1 clay, meaning that it

has two tetrahedral sheets sandwiching a central octahedral sheet. The particles are plate-

shaped with an average diameter of approximately one micrometre. Montmorillonites

expand considerably more than other clays due to water penetrating the interlayer

molecular spaces and concomitant adsorption. The amount of expansion is due largely to

the type of exchangeable cation contained in the sample. The presence of sodium as the

predominant exchangeable cation can result in the clay swelling to several times its

original volume.

The montmorillonite clay used was Montmorillonite K10 manufactured and

supplied by Sigma-Aldrich, Germany. The clay purchased from Sigma-Aldrich was

modified by introducing sodium ions followed by alkyl ammonium groups as per

standard procedures and then used as such as filler in the rubber matrix.

71

3.2.4 Kaolinite

Kaolinite is a layered silicate mineral, with one tetrahedral sheet linked through

oxygen atoms to one octahedral sheet of alumina octahedral. Compared to other clays,

kaolinite has a low shrink-swell capacity and a low cation exchange capacity

Kaolinite powder with 20–50 μm average thickness was obtained as an industrial

product from SanXing High-New Material Company of Zaozhuang in China. Presently it

is one of the finest types of kaolinite present worldwide. The chemical composition of

this kaolinite is SiO2 45.74%, Al2O3 35.61%, Fe2O3 0.88%, TiO2 1.23%, Na2O 0.41%,

K2O 0.32%, MgO 0.11%, CaO 0.12% and MnO less than 0.01%.

72

3.2.5 Graphite

Graphite is a layered compound, in each layer the carbon atoms are arranged in a

hexagonal lattice with separation of 0.142 nm, and the distance between planes is

0.335 nm. Each carbon is sp2 hybridized and is bonded to three other carbon atoms with a

C-C-C bond angle of 120o.

The graphite powder used as filler in the matrices was obtained from Central

Drug House (P) Ltd., New Delhi. The 99.5% pure graphite fine powder has maximum

size less than 50μm.

Graphite

73

3.2.6 Dicumyl Peroxide

Dicumyl peroxide is used as a high temperature catalyst in the rubber and plastics

industries. With a molecular weight of 270, dicumyl peroxide, a white granular solid,

melts at 100°F (38°C) can be used to crosslink a wide variety of polymers.

In the present work, the cross-linking agent used was 98% pure dicumyl peroxide

crystals, purchased from Sigma-Aldrich, manufactured by Aldrich, Japan.

C

CH3

CH3

O

O C

CH3

CH3

Chemical structure of dicumyl peroxide

74

3.3 Experimental

The experimental part includes a detailed procedure of modification of

montmorillonite clay with sodium ions and then further modification by introduction of

alkyl ammonium group. The preparation of the novel rubber blend and their

reinforcement with the various fillers are also explained.

3.3.1 Organo modification of MMT

The MMT clay to be modified was purified initially and then the sodium ions

were introduced followed by the exchange of sodium ions for alkyl ammonium group.

3.3.1.1 Purification of MMT

The purification of MMT was achieved by sedimentation, centrifugation and

drying following standard methods [13]. A portion of the MMT was crushed in an agate

mortar in order to obtain a fine powder. The clay was dispersed in de-ionized water in an

ultrasonic bath for ten minutes, stirred overnight, the sediments rejected and the syrupy

liquid product (size £ 2mm) was subjected to 5000 rpm for 15 min when the product

sedimented rapidly in the centrifugal field. Particles were quickly redispersed in double

distilled water. The concentrated solution obtained was dried at 50oC in a ventilated oven

for 4 days.

3.3.1.2 Preparation of Na-montmorillonite

In order to enhance the swelling properties of MMT, sodium activation was

performed by dispersing 25g of MMT in 5L of 1N sodium chloride solution with stirring.

The stirring was continued for 24h at 70oC. Upon centrifugation of the solution at high

75

speed, an opaque layer accumulated in the bottom of the centrifuge tubes beneath a

translucent gel. The gel was isolated and washed several times with distilled water until

no chloride was detected in the centrifugate by testing with one drop of 0.1N silver nitrate

solution. The purified clay was dried at 70oC and stored in a desiccator.

Tetrahedral sheet

Tetrahedral sheet

Octahedral sheet

2:1 layer

Interlayer Na

Structure of Sodium MMT

3.3.1.3 Intercalation of alkyl ammonium ions

The Na-exchanged MMT (15g) was dispersed in 1200mL of distilled water at

80oC. Then 5.7g of tetradecyltrimethyl ammonium bromide (cetyl ammonium bromide)

in 300mL distilled water was introduced into the above hot solution and stirred

vigorously for one hour at 80oC. The white precipitate was washed repeatedly with hot

water/ethanol (1:1) mixture until no chloride was detected in the filtrate by one drop of

0.1N silver nitrate solution. The cetyl ammonium-exchanged MMT was then dried for 48

hrs at 75oC, ground with agate mortar and then stored in a desiccator [14].

76

Structure of alkyl modified MMT

Arrangements of alkylammonium ions in layered clay silicates with different layer

charges.

77

3.3.2 Preparation of novel EPDM/Neoprene blends

Specified amount of EPDM rubber and Neoprene rubber (Table 3.1) were

dissolved in toluene and the whole mixture was mechanically stirred for 5hrs at 60oC and

finally cured by adding dicumyl peroxide (3 phr), before transferring into a glass mould.

Thin films of the blends were obtained after the solvent was removed.

Table 3.1: Compositions of EPDM/Neoprene blends

Sample Code

Neoprene

(per hundred parts of EPDM)

E 0

E 5N 5

E 10N 10

E 15N 15

E 20N 20

E 25N 25

3.3.3 Preparation of novel EPDM/Neoprene/modified MMT nanocomposites

Specified amount of EPDM rubber and Neoprene rubber (Table 3.2) were

dissolved in toluene using mechanical stirrer. The organo modified MMT clay dispersed

with toluene by ultrasonication was added to the rubber/toluene mixture. The whole

mixture was mechanically stirred for 5hrs at 60oC and finally cured by adding dicumyl

78

peroxide (3 phr), before transferring into a glass mould. Thin films of the rubber

nanocomposite were obtained with the exit of the solvent.

Table 3.2: Compositions of EPDM/Neoprene/modified MMT nanocomposites

Sample Code

Neoprene

(per hundred parts of

EPDM)

Organo-modified MMT


EPDM)

E 1M 0 1

E 3M 0 3

E 5M 0 5

E 20N 1M 20 1

E 20N 3M 20 3

E 20N 5M 20 5

3.3.4 Preparation of novel EPDM/Neoprene/Kaolinite composites

Differing amounts of EPDM rubber and Neoprene rubber (Table 3.3) were

dissolved in toluene using mechanical stirrer. The Kaolinite clay was dispersed with

toluene by ultrasonication and added to the rubber/toluene mixture. The whole mixture

was mechanically stirred for 5hrs at 60oC and finally cured by adding dicumyl peroxide

(3 phr), before transferring into a glass mould. Thin films of the rubber composite were

isolated after the solvent was removed.

79

Table 3.3: Compositions of EPDM/Neoprene/Kaolinite composites

Sample Code

Neoprene


EPDM)

Kaolinite


EPDM)

E 1K 0 1

E 3K 0 3

E 5K 0 5

E 7K 0 7

E 20N 1K 20 1

E 20N 3K 20 3

E 20N 5K 20 5

E 20N 7K 20 7

3.3.5 Preparation of novel EPDM/Neoprene/Graphite nanocomposites

Varying amount of EPDM rubber and Neoprene rubber (Table 3.4) were

dissolved in toluene using mechanical stirrer. A dispersion of graphite powder in toluene

through ultrasonication and the rubber/toluene mixture were mechanically stirred for 5hrs

at 60oC and finally cured by adding dicumyl peroxide (3 phr), before transferring into a

glass mould. Thin films of the rubber composite were obtained after exit of the solvent.

80

Table 3.4: Compositions of EPDM/Neoprene/Graphite composites

Sample Code

Neoprene


EPDM)

Graphite


EPDM)

E 1G 0 1

E 3G 0 3

E 5G 0 5

E 20N 1G 20 1

E 20N 3G 20 3

E 20N 5G 20 5

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Table 3.5: Consolidated List of Blends/Composites

S. No. Sample Code Composition

1 E EPDM

2 E 5N EPDM+5% neoprene





7 E 1M EPDM+1% CA-MMT



10 E 20N 1M EPDM+20% neoprene+1% CA-MMT



13 E 1K EPDM+1% kaolinite




17 E 20N 1K EPDM+20% neoprene+1% kaolinite




21 E 1G EPDM+1% graphite



24 E 20N 1G EPDM+20% neoprene+1% graphite



82

3.4 Characterization

All the prepared blends and composites were subjected to various characterization

techniques such as spectral analysis using FT-IR, morphological studies using scanning

electron microscope and XRD, mechanical characteristics through tensile testing and

thermal analysis using TGA and DSC. All these characterizations were done using best

available standard methods.

3.4.1 Spectral Analysis- Fourier Transform Infra-Red (FT-IR)

Infrared (IR) spectroscopy plays a very important role in the physical

characterization of polymers. IR absorption bands are well known for their marked

specificity to individual chemical functionalities. IR spectroscopy is a very powerful

probing tool for numerous scientific investigations in polymers. The assignment of IR

absorption bands for specific modes of molecular vibrations in polymers gives a good

idea about the ingredients present within the matrices. The FT-IR gives the plots of wave

numbers (cm-1

) versus percentage transmittance or absorbance of the corresponding

stretching, bending, rocking frequencies, etc. of the functional groups.

IR determinations were performed with a Perkin Elmer Spectrum GX1 FT-IR

spectrometer (Monza, Italy) equipped with a Spectra Tech. Total Attenuated Reflectance

(ATR) accessory. Number of scans was 32 at 4 cm-1

. Data were processed with the

Perkin Elmer software package; a Galactic Grams 32 v5.2 software package was used for

the curve fitting procedure.

83

3.4.2 X-ray Diffraction Studies (XRD)

Nanocomposite formation and the degree of nanoclay dispersion was monitored

using Philips X’pert wide-angle X-ray diffraction (XRD) system. The d-spacing of clay

in nanocomposites was calculated from XRD data using Bragg’s Equation [15]:

d = nλ / 2 sinθ

where, d is the spacing between layers of the clay, λ the wave length of X-ray

equal to 0.153 nm, θ the angle at the maximum point of the first peak (lowest θ) in the

spectra and n is a whole number, represents the order of diffraction, taken 1 in our

calculations.

Crystallinity of the samples has also been estimated using the XRD analysis in the

present work. Crystallinity is a measure of perfection and order within the matrix which

may be due to perfect arrangement of the polymer chains, perfect crosslinking or the

ordered layer structures introduced by the reinforced fillers. The crystallinity is calculated

by separating intensities due to amorphous and crystalline phase on diffraction phase.

Computer aided curve resolving technique is used to separate crystalline and amorphous

phases of diffracted graph. After separation, total area of the diffracted pattern is divided

into crystalline (Ic) and amorphous components (Ia). Percentage of crystallinity is

measured as ratio of crystalline area to Total area.

where, Ic is the intensity of crystalline phase and Ia is the intensity of amorphous

phase

84

3.4.3 Thermal Properties

Thermal analysis is a group of techniques in which a property of a sample is

monitored against time or temperature while the temperature of the sample, in a specified

atmosphere, is programmed. These are differential thermal analysis (DTA), differential

scanning calorimetry (DSC), thermogravimetry (TGA), thermomechanical analysis

(TMA), dynamic mechanical analysis (DMA), and dielectric analysis (DEA). The most

popular technique for polymer applications is DSC followed by TGA (along with its

derivative, DTGA). The use of the other methods is not as widespread as DSC and TGA.

3.4.3.1 Thermal Gravimetric Analysis (TGA)

The principal applications of TGA/DTGA in polymers are determination of the

thermal stability of polymers, compositional analysis, and identification of polymers from

their decomposition pattern. Also, TGA curves are used to determine the kinetics of

thermal decomposition of polymers and the kinetics of cure where weight loss

accompanies the cure reaction

Rubber blend and composite samples were heated from 40 to 600oC, at a heating

rate of 10oC min

-1 under a constant Helium (He) flow of 90 ml min

-1, with a thermo-

gravimetric analyzer (TGA) Q500 TA Instruments coupled to a Pfeiffer Vacuum

ThermoStar M Mass Spectrometer. The weight loss was measured as a function of

temperature, and the evolved gas masses were directly monitored. DTA graph was also

obtained from the same.

85

3.4.3.2 Kinetics

Kinetics is done based on the TGA/DTA data. The aim of evaluation of kinetic

parameters from thermal analysis data is to find out the probable kinetic model which

best describes the processes and allows the calculation of reliable values for the kinetic

parameters. From the kinetics of degradation, activation energy can be calculated from an

Arrhenius Correlation, and this parameter is useful for predicting material stability. The

most common technique is the analytical model fitting method. The mathematic models

from Freeman-Carrol, Friedman, Ozawa, Flynn and Wall, ASTM, Agarwal-

Sivasubramanium, Broido, Coats-Redfern and Horowitz-Metger have been widely used

for estimating the kinetic parameters. The three methods viz. Broido, Coats-Redfern (C-

R) and Horowitz-Metzger (H-M) [16-24] which are the most acceptable and commonly

employed are used to obtain kinetic parameters. Regression analysis has been carried out

for selected samples from all combinations prepared in the present investigation. The

kinetic parameters include temperature range of various possible stages of reaction,

activation energy (Ea) and the regression values (R2).The computerized plots are

obtained for all the three methods by using spread sheets in ORIGIN Software for data

entry such as temperature range, initial weight of the sample and the residual weight of

the sample at the temperature ‘t’.

86

The equation employed to evaluate the degradation kinetics in Coats-Redfern

method is given in Eqn. 1.

RT

EERT

E

AR

T

g aa

a 303.2)/21(

log)(log2

--=f

a Eqn. 1

Where,

T Temperature

A Pre-exponential term

R Gas constant

E Energy of activation

ɸ Heating rate

a f

t

WW

WW

-

-

0

0

W0, Wt and Wf are the initial weight, residual weight at temperature t and final

weight of the sample respectively.

According to Nair et al. [25], the energy of activation can be obtained from the

integral kinetic equation (Eqn. 1) which makes use of approximations in evaluating the

temperature integral and leads to a linear relation between log g(a) and reciprocal of

temperature (1/T). This procedure has led to a sample application of regression analysis

between g(a) and reciprocal of temperatures and fixes the kinetic mechanism for the

model that has regression value R2 close to unity. In Coats-Redfern method, the curves

having the highest correlation co-efficient values are considered.

87

3.4.3.3 Differential Scanning Calorimetry (DSC)

DSC is used to determine the Glass Transition Temperature (Tg) of

polymer, blends and composites. The temperature region where the physical transition

from a rubbery to a glassy state takes place is called the “Glass Transition temperature

(Tg). The melting temperature of the samples was measured by a 2920 DSC V2.4F

(Universal Instruments) at a heating rate of 10oC per minute in Nitrogen atmosphere.

3.4.4 Mechanical Properties

Any property of a material that defines its response to a particular mode of stress

or strain is mechanical property, which manifests in elastic moduli, strength, and ultimate

strain in several modes, impact strength, abrasion resistance, creep, ductility, coefficient

of friction, hardness, cyclic fatigue strength, tear strength, and machinability [26].

Mechanical properties of a material include elastic and inelastic reaction when subjected

to force resulting in stress and strain.

The most frequently used mechanical properties are the quasistatic methods which

involve relatively slow loading i.e., tension, compression, and flexure. Specimens for

testing may be produced by processing operations such as injection molding,

compression molding, or machining from sheets. Machined surfaces have to be

smoothened along their longitudinal axis with abrasive paper and any flash on molded

specimens shall be removed; the cross-sectional area has to be uniform along the whole

length subjected to testing. Consequences of any non-uniformity would show up as stress

concentrators.

88

Tensile testing is the most frequently used method to characterize the material

strength. The machine should be of the constant-rate-of-crosshead-movement type,

consisting of one fixed and one movable member, both carrying self-aligning grips. The

movable member shall move with a uniform, controlled velocity with respect to the

stationary one. An extensometer is used to determine the distance between two

designated points within the gage length of the test specimen as this is stretched. Speed of

testing is defined as the relative rate of motion of the grips or test fixtures. It is specified

for different types of specimen, varying typically from 1 to 500 mm/min (0:2---20 in:

min_1). The lowest speed that produces rupture in the time range 0.5–5 min for the

specimen geometry used is to be selected.

There are two essential properties determined each time. The first is the

engineering stress

σ = F/A0

where F is the applied force and A0 is the initial cross-sectional area.

Determination of the true stress based on the actual cross-sectional area A which changes

during the experiment is possible but more difficult. The other key property is the

engineering strain (also known as the nominal tensile strain)

ε = l-l0/l0 = Δl/l0

Here l is the current length of the specimen while l0 is the original length. The

quantities obtained most often from tensile testing are:

Tensile strength: The maximum load divided by A0.

89

Percent elongation: Whenever the specimen gives a yield load larger than the load

at break, the percent elongation at yield is considered. Otherwise the percent elongation

at break is reported [27].

Tensile Testing

The tensile enables to find tensile strength, elongation at break and tensile

modulus. All these tensile tests were performed by using INSTRON 3365, UK, testing

machine as per ASTM-D3039 standards with a cross head speed of 100mm/min. Samples

with a dimension of 100mm×10mm with an average thickness of 0.3mm were used. An

average of five measurements has been recorded.

3.4.5 Morphology-Scanning Electron Microscopy (SEM)

Scanning electron microscope technique is used to produce excellent images of

the phase structure of stained blends and block copolymers. In the SEM a narrow (10 nm)

primary electron beam of the order of 10 keV in energy is scanned across the surface of

the specimen and an image is built up pixel by pixel.

For phase morphology analysis, the samples were cryogenically fractured using

liquid nitrogen. SEM photographs of the fractured surfaces were taken after preferential

extraction of the minor phase using a Philips 505 microscope (Royal Philips Electronic,

Eindhoven, Netherlands).

90

3.5 References

[1] Vallat M, F, F. Ruch, M.O. David, European Polymer Journal, 40: 1575–1586

(2004).

[2] Van Drumpt J. D., Rubber World, 33: 33–41 (1988).

[3] Akiba M, Hashim A.S., Prog Polym Sci, 22: 421–75 (1997).

[4] Ogunniyi DS. Progr Rubber Plast Technol 15(2): 95–112 (1999).

[5] Loan L. D. Rubber Chem Technol 40: 149–76 (1967).

[6] Baldwin F. P., Ver Strate G. Rubber Chem Technol, 45: 709–881 (1972).

[7] Keller RC. Rubber Chem Technol 1988; 61(2):238–54 (1988).

[8] Dikland H. G., Kauts Gum Kunst 49(6): 413–7 (1996).

[9] Baldwin FP, Borzel P,Cohen CA, Makowsk i HS,Van de Castle JF. Rubber Chem

Technol 43(3): 522–48 (1970).

[10] Van Drumpt JD, Oosterwijk H H J. J Polym Sci, Polym Chem Ed, 14: 1495–511

(1976).

[11] Gonzalez L, Rodriguez A, Marcos A, Chamorro C. Rubber Chem Technol 69:

203–14 (1996).

[12] Harpel G. A., Walrod D. H., Rubber Chem Technol 46: 1007–18 (1973).

[13] Kornmann, X., Berglund, L.A., Sterte, J., Giannelis, E.P. Polym. Eng. Sci, 38:

1351 (1998).

[14] Chinnakkannu Karikal Chozhan., Muthukaruppan Alagar., Rajkumar Josephine

Sharmila., Periyannan Gnanasundaram. J. Polym. Res., 14: 319 (2007).

[15] Sperling L. H, Physical Polymer Science, Wiley, US, 2001.

[16] Freeman E. S. and B. Carrol, J. Phys. Chem., 62, 394 (1958).

91

[17] Friedman H. L., J. Polym. Sci, Part C, 6, 183 (1963).

[18] Ozawa T., Chem. Soc. Jpn., 38, 1881 (1965).

[19] Flynn J. H. and L. A. Wall, J. Polym Sci., Part B, 4,323 (1966).

[20] ASTM Committee on standards, ASTM E698, Annual Book of ASTM Standards

(1984).

[21] Agarwal R. K. and M. S. Sivasubramanian, AICHE. J., 33,7 (1987).

[22] Broido A., J. polym. Sci, A-2 (7), 1761 (1969).

[23] Coats A. W. and J. Redfern, Nature, 201, 68 (1964).

[24] Harowitz H. H. and G. Metzger, Anal. Chem., 35, 1464 (1963).

[25] Nair C. G. R and P. M. Madhusudhanan, Thermochimica Acta., 14, 373-382

(1976).

[26] Jan W. Gooch (Ed.) “Encyclopedic Dictionary of Polymers” Springer Science-

Business Media, LLC, (2007).

[27] James E. Mark “Physical Properties of Polymers Handbook” Springer Science-

Business Media, LLC, (2007).

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