Chapter 2shodhganga.inflibnet.ac.in/bitstream/10603/22422/13/13_chapter2.pdf.pdfGermany provided the commercially available maleic anhydride functionalized polypropylene, ExxelorTM

Chapter 2

Materials and Methods

Abstract

The characteristics of all the materials used in the study and the details of

the experimental techniques employed to get the final conclusion are presented

in this chapter. The methods of preparation of both TPEs and TPVs are

explained. The particulars of the analysis of phase morphology by scanning

electron microscopy and atomic force microscopy are incorporated. The

details of experimental setup and temperature programme for the spherulite

growth of PP in presence of NR and NBR using polarising microscope

coupled with hot-stage; the procedure for the study of bulk, fractionated and

self seeding crystallization; and measuring the Wide–angle X-ray scattering

(WAXS) pattern are included. Experimental setup for the isothermal and non-

isothermal crystallization kinetics has been discussed in detail. Information

about mechanical and dynamic mechanical tests, together with IR-strain

measurements for NBR/PP TPVs and nano-indentation for the NR/PP TPEs

are integrated.

88 Chapter 2

2. Experimental

2.1. Materials

Isotactic polypropylene, PP, (Koylene M3060) having melt flow index

(MFI) of 3g/10 min and density 0.905gm/cm3 at 23°C was kindly supplied by

Indian Petro Chemical Ltd, Vadodara, India. Natural rubber (NR, ISNR-5) and

epoxydised natural rubber (ENR25) were supplied by RRII, Kottayam, India.

Acrylonitrile co-butadiene rubber (Chemaprene N 3309) with acrylonitrile

content 34% was supplied by Synthetic and Chemicals, Bareli UP, India.

Hydroxy terminated natural rubber was synthesized in SCS, MGU. Exxon,

Germany provided the commercially available maleic anhydride

functionalized polypropylene, ExxelorTM PO 1020 with 0.5-1 wt% MA

content. Carboxylated polypropylene and NBR-MAPP graft copolymer

prepared from MA-PP and amine terminated NBR, (Hycar, Bayer, Germany)

were used for the compatibilization.

2.2. Methods: Melt Blending

NR/PP blends were prepared by melt mixing PP with NR in a Rheocord

at 180oC and 60 rpm. For the dynamic vulcanization, sulphur based curatives

were added to the blend in the mixing chamber where the vulcanization is

completed in 10 minutes.

NR/PP blends for the fractionated crystallization analysis, were prepared

by melt mixing PP with masticated NR in a Rheocord at 190°C and 60 rev/min

and to avoid the coalescence phenomena of the dispersed iPP phase, sulphur

based cure system was loaded in the blend using a two-roll mill and

vulcanized at 150°C (static vulcanization).

Materials and Methods 89

For the preparation of NBR/PP blends initially the components were

melt mixed in a Brabender Plasticoder PL 2000 at 65rev. min-1at 190°C for 4

min.

NBR/PP blends for the fractionated crystallization analysis, were

prepared by melt mixing PP with NBR in a Brabender Plasticoder at

65rev/min at 190°C for a mixing time of 6min and NBR phase was vulcanized

using sulphur based cure system. The compatibilizer were prepared at 180°C,

in the same brabender plasticoder, initially the MA-PP was melted and then low

molecular weight liquid NBR (Hycar ATBN X 16) is added and mixing

completed within 6min.

The compatibilizer were prepared at 180°C, in the same Brabender

Plasticoder. Initially the MA-PP had been melted and then low molecular

weight liquid NBR (Hycar ATBN X 16) is added and the mixing completed

within 6min.

For the preparation of dynamic vulcanizates initially the components

were melt mixed in a Brabender Plasticoder PL 2000 at 65rev. min-1 at 190°C.

Compatibilizer, curing agent and other additives were added following the

time-torque curve given in the fig 2.1. with the help of a computer attached to

the brabender. In Fig. 2.1, I, II, III and IV indicate order addition of each

additive and the corresponding time. (I-iPP, II-NBR, III-Compatibilizer, IV-

ZnO and Stearic Acid, V-Curing Agent, VI-Atioxidant) Mixing time was fixed

for 15min.

90 Chapter 2

0 2 4 6 8 10 12 14 160

2

4

6

8

10

12

14

16

18

VI

VIII

II

I

IV

Torq

ue (N

m)

Time (min)

Figure 2.1. Torque development during the dynamic vulcanization as a function of time.

Samples were hot pressed at 190°C under 70-bar pressure in a hydraulic

press. It is clear from the graph that at first the torque is high as we introduce

the iPP, when the temperature of the sample increases torque comes down.

Again it increases with the addition of NBR, and then the torque again comes

down. The compatibilizer is added and mixing continues till the torque levels

off. Then stearic acid and ZnO are added. After sometime torque again levels

off. Addition of curing agent leads to a substantial increase in the torque due

to the cross-linking of the rubber phase and thereby exerting grater resistance

to rotation. Thus the progress of the vulcanization can be conveniently

followed by monitoring torque during the mixing.


2.3. Analytical methods

2.3.1. Morphological characterization

The morphology of the NR/PP and NBR/PP blend was analyzed by

electron microscopy, using a SEM Philips microscope on cryogenically

fractured surfaces of the samples. Before the electron microscopy observation,

the surfaces were coated with Au–Pd alloy with a SEM coating device (SEM

Coating Unit). The SEM samples were prepared as follows: the strips cut from

compression-moulded samples were fractured in liquid nitrogen. NR and NBR

phases were removed by benzene and chloroform respectively. After etching

the phases, samples were dried in a vacuum oven at 70°C for 12 h and were

coated with gold using sputter coater. Then their SEM micrographs were

taken.

For the uncompatibilized and compatibilized blends micrographs were

obtained with average numbers and volume diameters (dn, dw and dv) of the

dispersed domains, using Image analysis software. The dispersity (D) of the

sizes obtained and the average number of particles/cm3 were also calculated

using the following equations.

dn = ∑ ∑ iii ndn / (2.1)

dw = iiii dndn∑ ∑/2 (2.2)

dv = iiii dndn 34 /∑ ∑ (2.3)

where ni is the number of droplets of ‘i’ with diameter di.

The polydispersity was evaluated with the equation D = dv/ dn

92 Chapter 2

The volume fraction of the dispersed phase was calculated from the following

relationship

Xv = (Xp/ρd)/[Xp/ρd+(1-Xp)/ρm] (2.4)

where Xp is the weight fraction of the minor phase and ρd is the dispersed

phase density.

The average particle number per cm3 was determined from

Nn = Xv 1cm3/[π/6(dn)3] (2.5)

The values calculated from the above equations could be used for

explaining the action of compatibilizer.

Atomic force microscopic examinations of the NBR/PP TPVs were

done using cryo-cut specimen with liquid nitrogen cooled diamond cutter.

Measurements were carried out in air at ambient conditions (25°C) with a

Nanoscope III Atomic Force Microscope, made by Digital Instruments Inc.,

USA. The experiments were carried out in tapping mode with constant

amplitude, using micro fabricated cantilevers. The scanning was done using

Olympus – Tapping Mode Etched Silicon Probe with square pyramid in shape.

The characteristics of the probe are: Force constant (K), 42 N/m; Nominal tip

radius of curvature less than 10 nm; cantilever length having a length of 160

µm and a tip height of 10 µm. Cantilever configuration: Rectangular Substrate

fits standard cantilever holder; Reflective coating with Aluminium; Tip half

angle of 17° on each side, 0° on front and 35° back. Images were analysed

using a Nanoscope imaging processing software.


2.3.2. Thermal analysis: fractionated crystallization

A TA DSC-2920 Instrument was used to determine the fractionated

crystallization behavior of PP and NR/PP blends. The following conditions

were applied for the study of the confirmed crystallization behavior of PP/NR

blends.

Stage 1. Heating of the sample in the calorimeter at a rate of 10°C/min from –

20 to 220°C.

Stage 2. Isothermal annealing at 220°C for 5 mins; this was done to remove

any crystalline nuclei if present.

Stage 3. Cooling of the sample in the calorimeter to -20°C at a rate of

10°C/min

Stage 4. Heating the sample in the calorimeter again to 220°C at a rate of

10°C/min.

From the heating and cooling curves the melting and crystallization

parameters were estimated.

Mettlor Toledo DSC 820 system was used to analyze the thermal

behavior of the following NBR/PP blends having compositions 100/00, 98/02,

95/05, 90/10, 85/15 and 80/20 in non-isothermal mode. Procedure adopted

was similar to the case of PP/NR TPEs.

2.3.3. Self-nucleation experiments

Successive self-annealing experiments were performed to initiate self-

nucleation in the NR/PP blend system. These experiments were also

performed using TA DSC (2920) Instrument. A procedure similar to the one

reported elsewhere [1] was adopted in theses experiments. In the beginning of

94 Chapter 2

the self-seeding techniques, the following steps were taken for erasing of

thermal history and creating an initial standard state of the material. Samples

were first heated to 220ºC at a heating rate of 10ºC /min and kept there for 10

minutes isothermally. Subsequently the samples were cooled to -20ºC at a

cooling rate of 10ºC/min. In the next step, the samples were heated to 165ºC

(just above the melting temperature of iPP). Then the samples were annealed

for five minutes to generate few crystals which are temperature resistant at that

temperature. Then the samples were cooled to -20ºC, at a cooling rate of

10ºC/min and kept it isothermally for 5 min. In the final step the samples were

heated to 160ºC and annealed at this temperature for 5 min for creating more

crystals and then cooled to -20ºC and kept for 5 min.

Mettlor Toledo DSC 820 system was used to analyze the thermal

behavior of the PP/NBR TPEs. Procedure adopted was similar to the case of

PP/NR TPEs.

2.3.4. Isothermal crystallization kinetics

A TA Instrument DSC 2920 apparatus was used to follow the

crystallization kinetics of PP and PP/NR blends. Baseline calibration,

calibration for the temperature scale and cell constant were carried out using a

pure indium standard (TºM= 156.6ºC) according to the procedure suggested

by TA Instrument in the instrument manual. To minimise the thermal lag

between polymer sample and DSC furnace, each sample pan was loaded with

a microtome cut piece from compression-moulded sheets of the blend having

the same thickness. Sample mass was kept around 10mg. Also for each

measurement new specimens were used and the specimen compartment was

flushed with dry N2 50ml/min to avoid any kind of oxidative degradation. The


following conditions were applied for the study of the melting and

crystallization behavior of NR/PP blends.

Stage 1. Heating of the sample in the calorimeter at a rate of 20°C/min from

–20 to 220°C

Stage 2. Isothermal holding segment at 220°C for 5 mins; this was done to

remove any crystalline nuclei if present.

Stage 3. Cooling of the sample in the calorimeter to Tc at a rate of

20°C/min and kept there for 60 min.


20°C/min.

From the exothermic curves, parameters of the crystallization kinetics

were estimated.

2.3.4.1. Kinetic model- Avrami

The model proposed by Avrami is based on the concept that

crystallization process is usually treated as a series of two-stage process: the

primary and the secondary crystallization stage. The crystallization process is

labeled by temperature dependence. The heat evolved during isothermal

crystallization (∆Hc) and the crystalline conversion (Xt) at constant

temperature is recorded as a function of time. Crystalline conversion can be

calculated using the eq. 2.6 [3-6]

0

0

( / )

( / )

t

tt

dH dtQXQ

dH dt dt∞

∞

= =∫

∫ (2.6)

In this equation, dH/dt is the rate of heat evolution during crystallization,

96 Chapter 2

Q∞ is the total heat evolution at the end of the crystallization and tQ is

the total quantity of heat evolved up to a time ‘t’. The volume fraction of the

crystalline material could be computed based on the following eq.

( ) 1 exp( )ntX Kt= − − (2.7)

X(t) is the volume fraction of the crystalline material at time ‘t’ and

isothermal crystallization temperature T. ‘n’ is the Avrami exponent related to

the nucleation type and crystal growth geometry. The crystallization rate

coefficient, K is a parameter of crystallization growth rate and is related to the

nucleation type, crystal growth geometry and crystallization temperature.

Based on these parameters, the crystallization half time, t1/2 which is a measure

of crystallization rate can be calculated from the following equation:

1

1/ 2 (ln 2 / ) nt k= (2.8)

2.3.4.2. Tobin’s model

While Avrami model is appropriate for the initial stages of

crystallization, good prediction can be obtained only up to 30% relative

crystallinity, since it does not consider the impingement of spherulites. Tobin

[7-9] proposed a theory of phase transformation kinetics with growth site

impingement to describe the isothermal crystallization process of polymers.

According to this approach, the equation of phase transition is explained on

the basis of Tobin exponent [10].

According to Tobin,

1

t

t

nt

t nt

k tXk t

=+

(2.9)


Strictly speaking, Xt is the relative crystallinity as a function of time, kt

is the Tobin crystallization rate constant, and nt is the Tobin exponent. Based

on this proposition, the Tobin exponent nt does not need to be integral, since it

is controlled directly by different types of nucleation and growth mechanism.

Curve fitting method could be followed to calculate the parameters of Tobin

crystallization kinetics.

2.3.5. Non-isothermal crystallization kinetics

The following conditions were applied for the study of the melting and

crystallization behavior of PP/NR blends.

Stage 1. Heating of the sample in the calorimeter at a rate of 20 K/min from

–20 °C to 220 °C.

Stage 2. Isothermal annealing at 220°C for 5 min; this was done to remove

any crystalline nuclei if present.

Stage 3. Cooling of the sample in the calorimeter to 25ºC at various cooling

rates.


20 K/min.

Each sample was measured at least two times.

From the exothermic curves, parameters of the crystallization kinetics

were estimated.

Mettlor Toledo DSC 820 system was used to analyze the dynamic

crystallization behavior of the PP and PP/NBR TPVs in non-isothermal mode.

To minimize the thermal lag between polymer sample and DSC furnace, each

sample pan was loaded with a cut piece from compression-molded sheets of

98 Chapter 2

the blend having the same thickness. Samples of about 10mg were taken in

aluminium sample pan and the measurements were done in nitrogen

atmosphere. Each sample was measured at least two times. The samples were

initially scanned in the temperature interval from 25 to 220oC, at a heating rate

of 10 K/min then kept for 10min at 220oC to destroy the thermal prehistory of

the samples. The samples were then cooled down at a cooling rate of 12 K/min

to 25ºC. The samples were kept at 25ºC for five minutes and then heated to

220ºC at a heating rate of 10K/min. In the coming cooling stages, various

cooling rates were (10, 8, 6 and 4 K/min) applied. The temperature for melting

(220ºC) was chosen to be much higher than the melting temperature (Tm) of

the neat PP under study. The melting at this maximum temperature leaves only

temperature resistant heterogeneous nuclei of unknown nature. From the

exothermic curves, parameters of the crystallization kinetics were estimated.

From the heating and cooling curves the melting and crystallization

parameters were estimated. These include,

a) Onset of melting (Tmonset)

b) Melting point (Tm)

c) Onset of crystallization (Tconset)

d) Crystallization temparature (Tc)

e) Endset of crystallization (Tcednset)

f) Normalized value of heat of fusion (∆Hf)

g) Normalized value of heat of crystallization (∆Hc)

h) Percentage crystallinity Xc

The percentage crystallinity was calculated using the expression,


% Crystallinity = ∆Hf x 100/∆Hof (2.10)

Here ∆Hf was the heat of fusion of the sample and ∆Hs° is that of 100%

pure crystalline PP, which is taken as 209J/g. [11,12]

2.3.5.1. Ozawa method-Theoretical background

The most common approach used to describe the overall isothermal

crystallization kinetics is the Avrami model [3,13,24] in which the relative

crystallinity as a function of time θ(t) can be expressed as

( ) 1 exp ( ) anat K tθ = − − (2.11)

where Ka and na are the Avrami crystallization rate constant and the

Avrami exponent, respectively. The Avrami rate constant Ka is written in the

form of the composite Avrami rate constant Ka (i.e. Ka = Kan). It should be

noted that both Ka and na are constants, specific to a given crystalline

morphology and type of nucleation for a particular crystallization condition

[15]. Based on the original assumptions of the theory, the value of the Avrami

exponent na should be an integer ranging from 1 to 4.

In the study of non-isothernal crystallization using DSC, the energy

released during the crystallization process appears to be a function of

temperature rather than time as in the case of isothermal crystallization. As a

result, the relative crystallinity as a function of temperature θ(T) can be

formulated as

0

( / )( )

T

cT

c

dH dT dTT

Hθ =

∆

∫ (2.12)

where Tο and T represent the onset and an arbitrary temperatures respectively,

100 Chapter 2

dHC is the enthalpy of crystallization released during an infinitesimal

temperature range dT, and ∆HC is the overall enthalpy of crystallization for a

specific cooling condition.

To use Eq.(12) for the analysis of non-isothermal crystallization data

obtained by DSC, It must be assumed that the sample experience the same

thermal history as designated by the DSC furnace. This may be realized only

when the thermal lag between the sample and the furnace is kept minimal. If

this assumption is valid, the relation between the crystallization time t and the

sample temperature T can be formulated as

0T Ttφ−

= (2.13)

where φ is the cooling rate. According to the equation (13), the horizontal

temperature axis observed in a DSC thermogram for a non-isothermal

crystallization data can readily be transformed into the time scale. Based on

the mathematical derivation of Evans [6], Ozawa [16] extended the Avrami

theory [3-5] to describe the non-isothermal crystallization data.

Mathematically, the relative crystallinity function of temperature θ(T) can be

represented as a function of cooling rate as

0

0( ) 1 exp n

Ktθφ

− = −

(2.14)

where KO is the Ozawa crystallization rate function, and nO is the Ozawa

exponent. It should be noted that the Ozawa kinetic parameters (ie., KO and nO)

hold similar physical meaning that of the Avrami.


2.3.6. WAXD analysis

Wide–angle X-ray diffraction (WAXD) measurements were performed

in the transmission mode with a Krystalloflex K70 (Siemens) instrument. The

CuKα radiation was filtered using Ni filter. The measurements were done in

the 2θ range of 5 to 50o with an interval of 0.05o. Cryotomed samples having

dimensions of 4x2x0.1 mm were used for this study. Thin samples were

isothermally crystallized at 124ºC using the same temperature programme

adopted in DSC measurements. Following blends of PP/NR having

compositions 100/00, 95/10, 90/10, 80/20, 70/30, 50/50 and 50/50 D were

used for the X-ray measurements. The background scattering corresponding to

an empty sample holder was subtracted from the experimental curves.

For the NBR/PP TPEs (minor amount of PP) samples having dimensions

of 40x20x1 mm were used for X-ray diffraction study.

The degree of crystallinity Xc.WAXD = Area of the six distinct crystalline

peaks at 2θ angles 14.05o, 16.85o, 18.45o, 21.6o and 28.65o/ total area under the

normalized WAXD curve including that under the amorphous halo. [17,18]

2.3.7. Hot stage-polarizing optical microscopy

The morphology and the isothermal spherulite growth rate were studied

by using a Zeiss Axioscope polarizing optical microscope, fitted with a

Linkam hot stage. The radial growth rate, G. dr/dt (where r is the radius of the

spherulites and t the time), was calculated by measuring the size of iPP

spherulites during the isothermal crystallization process. The standard

procedure adopted was given below. Thin films having a thickness of 30µm

were trimmed using a Mikrom microtome. Then the thin film was sandwiched

102 Chapter 2

between two microscope slides, heated at 220°C for 10 min, then cooled to Tc

and allowed to crystallize, entire procedure were done in dry nitrogen

atmosphere. The radial growth rate of a spherulite was monitored during

crystallization by taking photomicrographs automatically at appropriate

intervals of time with cross-polarized light. From the plots of r against the

time, G was calculated as the slope of the resulting straight lines.

In the case of NBR/PP TPEs, the optical hot-stage experiments were

conducted with a Leica hot-stage system with programmed temperature

controller and cooling system. The hot stage was mounted on a Leica DMLP

microscopy system equipped with a 20x (magnification 200 times) objective

and Carton CCD camera (http://www.carton-opt.co.jp.). Other experimental

conditions were similar to the case of NR/PP blend.

2.3.8. Tensile testing

Tensile measurements were performed in accordance with ISO R527

[19] at room temperature on an Zwick tensile tester with a crosshead speed of

20 mm/min. All samples were tested to stress at break. The Young’s modulus

(Ey) is determined from the initial slope of the stress–strain curve while the

tensile strength and elongation at break were calculated from the curve.

2.3.9. Dynamic mechanical analysis

The glass transition temperatures of the TPEs and the TPVs from NR/PP

blend were determined by dynamic mechanical analysis (DMA). Experiments

were performed in a TA 820 DMA, in tensile mode, at a frequency of 1 Hz.

Samples were heated from -80 to 80°C at a rate of 2°C/min. The peak

temperatures in the loss modulus were taken to define operational mechanical

glass transition temperatures. Thin sheets of NR/PP blend were prepared using

hot press, they heated up to 180°C at a heating rate of 10°C and compression


moulded at 180°C and cooled to 25°C. Rectangular thin film specimens having

3mm×30mm were cut from the moulded sheet and analyzed under tensile mode

in the DMA at 10Hz. Thermal procedures adopted were given below.

Step 1. Cooling to -80°C using liquid nitrogen.

Step 2. Isothermal for 10min at -80°C.

Step 3. Heating to 600C at a heating rate of 2°C/min.

The dynamic mechanical behavior of NBR/PP blends and dynamic

vulcanizates was studied using a rheometer of model ARES N2 Rheometric

Scientific under torsional mode. The testing temperature ranged from -100°C

to 150°C and the experiment was carried out at 10Hz at 2°C/min.

2.3.10. Nano-indentation

For NR/PP TPEs Instrumented microhardness tests were done using a

Nanoindenter XP, MTS Systems Inc., equipped with a diamond Berkovich

pyramide. The specimens, produced using a microscopic hot stage at a cooling

rate of 10K/min, had a thickness of 100 µm and were glued on metallic sample

holders. The indentation depth was 3 µm, the indentation rate 0.15µm/s. After

a holding time of 30s at maximum load to reduce creep effects, the specimens

were unloaded. The indentation hardness HIT was calculated at the maximum

load Fmax with the aid of the projected contact area Ap.. Accordingly [20,21]:

p

maxIT A

FH = (2.15)

If the deformation of the diamond indenter is neglected, the indentation

modulus EIT can be calculated from the unloading segment according to

[20,21]: the following equation.

104 Chapter 2

)1(A2

SE 2

p

IT ν−⋅π

= (2.16)

where ‘S’ is the contact stiffness dF/dh at maximum load. Because the

exact Poisson's number ν of the materials were unknown, the values of ν were

calculated using a simple rule of mixture. 0.38 and 0.5 are the values of PP

and the NR components respectively. Note, that value of ν is squared and so a

possible difference between the calculated and the real values has a relatively

small influence on the determined indentation modulus.

2.3.10. Infrared Strain Measurements

Films having thickness of 50±3µm were compression moulded at 190oC.

Samples having dimensions 20×10mm were cut for the spectroscopic analysis.

Figure 2.2. Instrumental setup for the infrared strain measurements.

FTIR measurements were carried out on a Perkin-Elmer FTIR

spectrometer S2000 and the experimental setup is shown in fig 2.2. The


spectrum examined covers the range between 585 to 3500cm-1 with a

resolution of 2 cm-1 and 16 spectra were taken during each measurement. The

duration of such a measurement was about 30s. The incident radiation area has

a diameter of 5 mm. The measurements were carried out with and without the

polarizer adjusted alternately parallel and perpendicular to the draw direction.

A stretching machine which allows for uniaxial stretching was placed into the

sample compartment of the spectrometer. In the tensile test the extension was

carried out incrementally in steps of 50% at room temperature. At the applied

strain, the specimen was held for 2 min to relax before IR measurements

started.

106 Chapter 2

2.4. References

1. Fillon B, Wittman JC, Lotz B, Thierry, A, J. Polym. Sci. B, 1993: 31; 1383.

2. Young RJ, Lovell PA, Introduction to Polymers, London: Chapman and

Hall; 1991.

3. Avrami M, J. Chem. Phys. 1939: 7; 1103.



6. Evans UR, Trans Faraday Soc. 1945: 41; 365.

7. Tobin MC, J. Polym. Sci., Polym. Phys. 1974 : 12; 399.

8. Tobin MC, J. Polym. Sci, Polym. Phys. 1976 : 14; 2253.

9. Tobin MC, J. Polym. Sci., Polym. Phys. 1977 : 15 ; 2269.

10. Young RJ and Lovel PA, Introduction to Polymers, Chapman and Hall,

London, 1991.

11. Patric S. Dai, Peggy Cebe, Malcolm Capel, Polym. 2002: 40; 1644.

12. Ana LN, Da Silva, Marisa CG. Rocha, Lea Lopes, Beatriz S. Chagas,

Fernanda MB. Coutinho. 2001: 81; 3530.

13. Avrami M, J. Chem. Phys. 1940 : 8; 212.


15. Wunderlich B, Macromolecular Physics, Academic Press, New York, 1976:

2,5; 139.

16. Ozawa T, Polym. 1971: 12; 150.

17. Rabiej S, Eur. Polym. J. 1991: 27; 947.


18. Young RJ, Lovell PA, Introduction to Polymers, London: Chapman and

Hall; 1991.

19. ISO 2000: 14577.

20. Oliver WC. and Pharr GM, J. Mater. Res. 1992: 7; 1564.

21. ISO 2002: 14577.

Chapter 2shodhganga.inflibnet.ac.in/bitstream/10603/22422/13/13_chapter2.pdf.pdfGermany provided the commercially available maleic anhydride functionalized polypropylene, ExxelorTM

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