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CHAPTER II

Experimental

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Chapter II

Department of Materials Science 49

2.1 INTRODUCTION

The blending of polymers is now a days the most versatile method

for producing unique combination of properties such as mechanical,

thermal, flame retardant, etc. Literature survey reveals that considerable

work has been done on the blends of epoxies and polyurethanes [1-3]. In

most of these cases attempts have been made to improve physical and

mechanical properties of the epoxies but very little work has been done so

far to obtain flame retardant polyurethane/epoxy blend. However,

sufficient literatures are available where researchers have tried to prepare

flame retardant polyurethane and epoxy blends by mixing these polymers

individually with other polymer components rather than combining

polyurethane with epoxies. Discussed here are few recently developed

flame retardant systems.

Organic polyphosphazenes are used [4] in polymer blends and

interpenetrating polymer networks (IPNs) to impart flame retardancy.

Due to the presence of alternating phosphorous, nitrogen moiety in the

backbone, they have good thermo-oxidative stability. Hundreds of

polyphosphazenes [5] are reported with different side groups. But due to

their high cost, use is only limited to military applications.

Pin-Sheng Wang and his group have prepared polyurethane blends

with poly (bis-propoxy phosphazene) [6]. The blends follow two-step

degradation process and also have higher char yield at 550 OC. Their LOI

values are also higher than the neat polyurethanes.

Xelei Chen and his research team have reported UV-curable

blends of polyurethane acrylate modified with a phosphorous monomer

[7]. Combustion and thermal behaviour of the blends have been found

Chapter II


out. Results show that the blends have good flame retardancy and burning

process can be explained on basis of a condensed phase mechanism.

Gouri et al [8] have synthesized hexaglycidyl cyclotriphosphazene

(HGCP) and used as a reactive flame retardant to blend with

commercially available epoxy resin (DGEBA). The blends of HGCP with

DGEBA improve the thermal stability at elevated temperature with

higher char yields compare to neat DGEBA thermoset.

2.2 AIM OF THE PRESENT WORK

At the present work, attempts have been made to develop certain

phosphorous containing flame retardant polymer blends based on

polyurethanes and epoxies. These polyurethanes, epoxies and their

respective monomers have been characterized by various chemical and

instrumental analysis techniques. These polymers have also been used to

prepare polymer nanocomposites. Polymer blends have been used for the

casting of films and coating for different substrates. Thermal, mechanical

and flame retardant properties of the neat as well as blends have been

found out.

This chapter deals with the synthesis and characterization of

monomers and polymers. The entire work has been divided into

following parts:

1. Synthesis and characterization of phosphorous containing

monomers: diols and polyols have been synthesized in the

laboratory

2. Synthesis of phosphorous containing flame retardant polyurethane

resins by reacting the phosphorous containing diols or polyols with

different diisocyanates

Chapter II


3. Synthesis of phosphorous containing epoxy resins by reacting

phosphorous containing triols with epichlorohydrine

4. Characterization of the polyurethanes and epoxy resins using

chemical and instrumental analysis techniques

2.3 METHODS USED FOR THE CHARACTERIZATION OF

MONOMERS AND POLYMERS

The synthesized monomers and polymers are characterized by

various chemical analysis and instrumental analysis techniques which are

described below.

2.3.1 Chemicals analysis methods

(i) Determination of number of hydroxyl groups

Number of hydroxyl groups in monomers was determined using

acetylation method [9]. This method involves replacement of the

hydrogen on a hydroxyl group by acetyl group. The reagent used was

acetic anhydride in pyridine and was used in excess. Following reactions

occur

R(OH) n(CH3CO)

2O R(OCOCH

3) nCH

3COOH (CH

3CO)

2O

(CH3CO)

2O CH

3COOH

+ + + (Excess)nn

(Excess) + H2O 2

Addition of water converts excess of acetic anhydride into acetic

acid. The total free acid was determined by titrating with standard sodium

hydroxide solution.

A blank experiment was performed simultaneously identical as the

above in absence of sample. The difference in the volume of sodium

hydroxide solution required in the two experiments is equivalent to the

difference in the amount of acetic acid formed. By knowing the molecular

Chapter II


weight of the compound, number of hydroxyl group can be calculated

using the following equation

Number of hydroxyl group = 1000 W

weightMolecular N )V-(V 12

Where, 42.02 =

W = Weight of sample in gm.

V2 = Volume of sodium hydroxide used in blank

V1 = Volume of sodium hydroxide used in sample

N = Normality of sodium hydroxide used in estimation

56.1 X 1000

Hydroxy Equivalent Weight = -------------------------

Number of OH group

Where, 56.1 = Equivalent Weight of KOH

(ii) Determination of percentage of isocyanates

The percentage of free isocyanate groups was determined by

reacting the sample containing isocyanate groups with excess of standard

n-butylamine in dioxane reagent [10, 11].

R–N=C=O + C4H9NH2 RNHCONHC4H9 + C4H9NH2

(Excess)

The excess n-butylamine was titrated with standard acid. A blank

experiment has also been performed in absence of sample.

Percentage of isocyanates group was calculated using the following

equation

% NCO = 1000 W

100 42.02 N )V-(V 12

Chapter II


W = Weight of sample in gm

V2 = Volume of acid used in blank

V1 = Volume of acid used in sample

N = Normality of acid used in estimation

(iii) Determination of epoxy equivalent weight (EEW)

The epoxy equivalent weight was determined by reacting the

sample containing epoxy groups with excess of standard HCl in dioxane

reagent [12, 13].

R CH2

CH CH2

O

ClH R CH2

CH CH2

OH

Cl ClH+ + (Excess)

The excess HCl was titrated with standard alcoholic NaOH

solution. A blank experiment has also been carried out in absence of

sample. Epoxy equivalent weight of the sample was calculated using the

following equation.

Epoxy Equivalent Weight (EEW) =1000 W

(V2-V1) N

W = Weight of the sample in gm

V1 = Volume of alc. NaOH used in sample

V2 = Volume of alc. NaOH used in blank

N = Normality of alc. NaOH used in estimation

Chapter II


2.3.2 Instrumental analysis techniques

(i) Measurement of Intrinsic Viscosity (η)

Intrinsic viscosity of the synthesized polymers was determined by

Ubbelohde Suspended Level Viscometer (USLV) in methyl ethyl ketone

(MEK) solvent at the temperature of 30 OC.

(ii) Determination of average molecular weight of polymers

Number average molecular weight of the polyurethanes and

epoxies were determined by Gel Permeation Chromatographic (GPC)

technique using Perkin Elmer USA (Model Series 200).

(iii) Elemental analysis

Elemental analysis of the monomers and polyurethanes was carried

out using PERKIN ELMER USA (Model 2400 SERIES II). Theoretical

and experimental values in terms of percentage have been given in the

Tables.

(iv) Fourier transform infra-red (FTIR) analysis

The fourier transform infra-red spectra of the monomers and

polymers were recorded in KBr pallet on Perkin Elmer USA (Model

SPECTRUM GX, FT-IR spectrophotometer).

(v) Nuclear magnetic resonance (NMR) spectroscopy

1H NMR spectrum of the certain monomers was taken in DMSO

solvent using tetramethylsilane as reference on Bruker, Switzerland

Model AVANCE 400.

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Chapter II


2.4 EXPERIMENTAL

Different polyurethanes and epoxies synthesized in the laboratory

are given below.

2.4.1 Phosphorous based flame retardant polyurethanes

Phosphorous containing polyurethanes synthesized in the

laboratory are divided into groups as follows

(i) Mono phosphorous based polyurethanes

[a] Polyurethanes based on tris (m-hydroxy phenyl) phosphate

[b] Polyurethanes based on tris (bisphenol-A) monophosphate

[c] Polyurethanes based on bis (m-hydroxy phenyl) methyl

phosphine oxide

[d] Polyurethanes based on ester exchange reaction product of castor

oil and tris (m-hydroxy phenyl) phosphate

(ii) Diphosphorous based polyurethanes

[a] Polyurethanes based on resorcinol bis (hydroxy phenyl

phosphonate)

[b] Polyurethanes based on bisphenol-A bis (hydroxy phenyl

phosphonate)

2.4.2 Phosphorous based flame retardant epoxies

Phosphorous containing epoxy resins synthesized in the laboratory

are

[a] Triglycidyl ether of tris (bisphenol-A) monophosphate

(TGETBAMP)

[b] Triglycidyl ether of tris (m-hydroxy phenyl) phosphate

(TGETHPP)

2.4.3 Non-phosphorous based liquid epoxy resin

Diglycidyl ether of bisphenol – A (DGEBA) was procured from

local market and used for the study.

Chapter II


The graphical presentation of the polymers used for the present

study is shown below.

Figure 2.1: Method of synthesis and their characterization

2.4.1 Phosphorous based flame retardant polyurethanes

(i) Synthesis of mono phosphorous based polyurethanes

[a] Polyurethanes based on tris (m-hydroxy phenyl) phosphate

(i) Synthesis of the monomer: Tris (m-hydroxy phenyl) phosphate

(THPP)

In a 250 ml round bottom flask equipped with a condenser,

phosphorous oxychloride (POCl3: 153 gm, 1 mole) and resorcinol (330

gm, 3.0 mole) were heated at 110 OC for 2.0 hours in presence of N, N-

dimethylaniline (PhNMe2) (3.4 ml, 0.027 mole). The reaction mixture

was further heated at 110-115 0C for 1.5 hours to get the title product.

Chapter II


Product was purified by washing and neutralized to pH 7 to obtain solid

product. Crystallization was done in methanol [14].

Characterization:

(i) Melting point: 214-216 OC

(ii) Percentage yield: 75 %

(iii) Number of hydroxyl groups: 2.91

(iv) Elemental analysis (%)

C H

59.17

(57.4)

3.72

(4.01) (Calculated values are listed in parenthesis)

(ii) Infra-red analysis

IR spectrum of the monomer (THPP) shows broad absorption band

at 3388 cm-1

due to hydrogen bonded hydroxyl species, the band at 1261

cm-1

corresponds to Ar-OH symmetric stretching frequency, C=C

stretching of aromatic ring is obtained at 1494 cm-1

, the bands at 1252

cm-1

and 991 cm-1

are due to the P=O and P-O-C stretching frequencies

respectively. The aromatic C-H stretch appears at 3000 cm-1

.

Figure 2.2: FTIR spectrum of tris-(m-hydroxy phenyl)phosphate (THPP)

Chapter II


(ii) Synthesis of polyurethanes

Polyurethanes were synthesized by reacting tris (m-hydroxy

phenyl) phosphate with different diisocyanates as shown in the reaction

scheme-1 [15]. To synthesize the PU-1, tris-(m-hydroxy phenyl)

phosphate (THPP, 1.0 mole) and solvent methyl ethyl ketone (MEK)

were charged into a three necked flask equipped with dropping funnel,

reflux condenser and over head stirrer. Toluene diisocyanate (TDI, 2.4

mole) was added in a dropwise manner into the reaction mixture over a

period of 1 hour with constant stirring at 60 OC. The molar ratio of OH to

NCO was kept as 1:1.6 to produce NCO terminated polyurethane. After

the completion of addition, heating was continued for further 2 hours to

complete the reaction. After vacuum distillation pure NCO terminated

polyurethane (PU-1) was obtained.

Other two polyurethanes PU-2 and PU-3 were also synthesized by

reacting the THPP with another two diisocyanates, isophoron

diisocyanate (IPDI) and hexamethylene diisocyanate (HMDI)

respectively in the same manner. Reaction conditions and other

particulars are given in the Table 2.4.1.

Chapter II


Reaction Scheme 1:

OH

OH

P ClCl

Cl

O

OCN R NCO

O

OH

O

O

OHO

P

OH

O

O CO NH R NH CO NCO

O

O

PO

CH3 CH

3

CH3

CH3

CH3

CH2 (CH

2)6

+110 0C, 2 hrs

N,N-dimethyl aniline

60 0C, 3.0 hrs

ResorcinolPhosphorous oxychloride

Tris (m-hydroxy phenyl) phosphate (THPP)

Diisocyanates

Polyurethane based on tris (m-hydroxy phenyl) phosphate

110-115 0C, 1.5 hrs

n

Where R =

PU-1 PU-2 PU-3

Chapter II


Characterization

Table 2.1

(i) Reaction Conditions and Specification of the Polyurethanes

(ii) Elemental analysis (%)

System C H N

PU-1 60.76

(60.07)

4.23

(4.00)

9.11

(9.34)

PU-2 60.84

(60.96)

6.70

(6.87)

8.46

(8.37)

PU-3 57.69

(57.21)

6.45

(6.13)

9.45


(iii) Infra-red analysis

In IR spectra, the broad bands around 3327-3389 cm-1

attribute to N-

H band, the bands at 1607-1677 cm-1

are for -NHCOO group. The

absorption bands around 2272-2281 cm-1

are due to free NCO groups in

polyurethane which are absent in the monomer. Bands around 1220-1243

cm-1

are observed for P= O group. The bands at 985 -995 cm-1

are due to

the presence of P-O-C frequency. The bands around 3000 – 3100 cm-1

are

due to the stretching frequency of aromatic C-H bond.

System Types of

isocyanate

used

Reaction

conditions

%

NCO

content

Intrinsic

viscosity

η

dl/gm

GPC

Data

Temp. OC

Time

hrs. Mn

Mw

Mn

PU-1 TDI 60 3 1.6 0.61 2304 1.8

PU-2 IPDI 60 3 1.8 0.57 2530 2.2

PU-3 HMDI 60 3 1.8 0.52 2231 1.9

Chapter II


Figure 2.3: FTIR spectra of polyurethanes based on tris-(m-hydroxy

Phenyl) phosphate (THPP) (PU-1 to PU- 3)

Chapter II


[b] Polyurethanes based on Tris-(Bisphenol –A )Monophosphate

(i) Synthesis of monomer: Tris-(bisphenol –A) monophosphate

(TBAMP)

The monomer tris-(bisphenol –A) monophosphate was synthesized

by reacting bisphenol-A (684 gm, 3.0 mole) and phosphorous

oxychloride (93.3 ml, 1.0 mole) at the temperature of 130 OC for 12 hours

in presence of a catalyst N, N, dimethyl aniline (0.0132 moles). Final

product was obtained by dissolving the crude product in acetone and

reprecipitating from cold water. The product was dried and crystallized

from methanol [16].

Characterization

(i) Melting point: 165 – 167 OC

(ii) Percentage yield: 70-75 %

(ii) Number of hydroxyl groups: 3.0

(iii) Elemental analysis (%)

Calculated values are listed in parenthesis)

(iv) IR analysis

The IR Spectrum of the monomer shows a broad absorption band

around 3410 cm-1

due to the presence of H-bonded hydroxyl species, the

band at 1262 cm-1

corresponds to Ar-OH symmetric stretching

frequency, the band at 1235 cm-1

is due to the presence of P=O group and

band at 975 cm-1

is due to the P-O-C stretching frequencies. The

aromatic C-H stretch appears at 3000 cm-1

.

C H

74.17

(73.85)

6.18

(5.27)

Chapter II


Figure 2.4: FTIR spectrum of tris-(bisphenol –A) monophosphate

(TBAMP)


Polyurethanes were synthesized by reacting tris-(bisphenol-A)

monophosphate with different diisocyanates. To synthesize the PU-4, tris-

(bisphenol-A) monophosphate (TBAMP, 1.0 mole) and solvent methyl

ethyl ketone (MEK) were charged into a three necked flask equipped with

dropping funnel, reflux condenser and over head stirrer. Toluene

diisocyanate (TDI, 2.4 mole) was added in a dropwise manner into the

reaction mixture over a period of 1 hour with constant stirring at 60 OC.

The molar ratio of -OH to -NCO was kept 1:1.6 to produce NCO

terminated polyurethane. After the completion of addition, heating was

continued for further 2 hours to complete the reaction. After vacuum

distillation pure NCO terminated polyurethane (PU-4) was obtained

(Scheme 2).

Other diisocyanates such as isophoron diisocyanate (IPDI),

hexamethylene diisocyanate (HMDI) were reacted with TBAMP using

above method to produce PU-5 and PU-6 respectively. Reaction

conditions are given in the Table 2.4.2.

Chapter II


Reaction Scheme 2:

Chapter II


Characterization

Table 2.2

(i) Reaction Conditions and Specification of the Polyurethanes based on

tris-(bisphenol –A) monophosphate


System C H N

PU-4 69.07

(68.96)

5.53

(5.27)

6.57

(6.70)

PU-5 70.11

(69.73)

7.59

(7.10)

5.91

(6.03)

PU-6 67.53

(67.04)

7.02

(6.80)

6.89



The IR spectra of polyurethanes show absorption bands around 1581-

1649 cm-1

for OCONH group frequency. The absorption bands around

2251-2263 cm-1

are due to free NCO groups in polyurethane. The bands

for P=O group appears around 1220-1241 cm-1

. P-O-C stretching

frequency is observed around 967-979 cm-1

. The broad bands around

3301-3347 cm-1

attribute to N-H bands. The bands around 3000 – 3100

cm-1

are due to the C-H stretching frequency.

System Types of

isocyanate

used

Reaction

conditions

%

NCO

content

Intrinsic

viscosity

η

dl/gm

GPC

Data

Temp. OC

Time

hrs. Mn

Mw

Mn

PU-4 TDI 60 3 1.9 0.95 3289 1.6

PU-5 IPDI 60 3 1.8 0.91 3357 1.8

PU-6 HMDI 60 3 1.6 0.85 3171 2.1

Chapter II


Figure 2.5: FTIR spectra of polyurethanes based on tris-(bisphenol –A)

monophosphate (PU- 4 to PU- 6)

Chapter II


[c] Synthesis of polyurethanes based on bis-(m-hydroxy phenyl)

methyl phosphine oxide

(i) Synthesis of monomer: Bis-(m-hydroxy phenyl) methyl phosphine

oxide (BHPMPO)

The monomer was synthesized in four steps.

1. Synthesis of diphenyl methyl phosphine oxide from triphenyl

phosphine.

2. Synthesis of bis-(m-nitro phenyl) methyl phosphine oxide from

diphenyl methyl phosphine oxide.

3. Synthesis of bis-(m-amino phenyl) methyl phosphine oxide from

bis-(m-nitro phenyl) methyl phosphine oxide.

4. Synthesis of bis-(m-hydroxy phenyl) methyl phosphine oxide from

bis-(m-amino phenyl) methyl phosphine oxide.

1. Synthesis of diphenyl methyl phosphine oxide from triphenyl

phosphine (DPMPO)

To synthesize diphenyl methyl phosphine oxide, triphenyl

phosphine was allowed to react with methyl iodide at room temperature

in presence of petroleum ether and chloroform as solvent. The mixture

was stirred overnight. The precipitated white solid was filtered, washed

with petroleum ether and dried under vacuum. The dried solid was

refluxed in a mixture of water and aqueous KOH solution (40%) for 2

hours. Benzene evolved during the reaction was collected using Dean and

Stark apparatus. The content left in the flask was extracted in toluene

using separating funnel. The toluene extracts were collected and kept

overnight as such to get fine crystals of DPMPO [17].

Chapter II


Characterization


(ii) Percentage yield: 87- 90 %


C H N

72.07

(72.22)

6.11

(6.02)

-----

(Calculated values are listed in parenthesis)

(v) Infra-red analysis

IR spectrum of diphenyl methyl phosphine oxide shows the

absorption band at 1494 cm-1

corresponds to C=C stretching of aromatic

ring and the band at 1200 cm-1

is due to the presence of P=O group.

Figure 2.6: FTIR spectrum of diphenyl methyl phosphine oxide

(DPMPO)

Chapter II


2. Synthesis of bis-(m-nitro phenyl) methyl phosphine oxide

Nitration of DPMPO was carried out using the following

method. A mixture of conc. HNO3 and conc. H2SO4 mole ratio of 1:1

was charged [18] into a three necked flask. Diphenyl methyl phosphine

oxide (50 gm, 0.24 mole) was added in pinch by pinch manner at

10-15 OC. After the completion of addition the content was stirred for

further 30 minutes at the same temperature. The resultant mixture was

poured into ice-cold water to get the precipitates. Pure nitro compound

was obtained after washing thoroughly with water and crystallizing from

ethanol.

Characterization

(i) Melting point: 201 OC

(ii) Percentage yield: 80 –82 %


C H N

51.08

(50.98)

3.47

(3.59)

9.11


(iv) Infra-red analysis

The IR spectrum shows the absorption band at 1510 cm-1

due to

NO2 group. The band at 1494 cm-1

corresponds to C=C stretching of

aromatic ring and the band at 1200 cm-1

is due to the presence of P=O

group. The aromatic C-H stretch appears at 3000 cm-1

.

Chapter II


Figure 2.7: FTIR spectrum of bis-(m-nitro phenyl) methyl phosphine

oxide (BNPMPO)

3. Synthesis of bis-(m-amino phenyl) methyl phosphine oxide

Bis-(m-nitro phenyl) methyl phosphine oxide ( 7 gm, 0.022 mole),

alcohol (70 ml), water (15 ml) and conc. HCl (1 ml) were charged into a

250 ml three necked flask and heated in a boiling water bath. Iron powder

(15 gm) was added pinch by pinch during 1 hour with constant stirring

[19]. Stirring was continued under the same reaction conditions for 1.5

hours. The reaction mixture was then made alkaline with ammonia and

filtered hot. The filtrate was allowed to cool in an ice-bath. The solid

separated was filtered and washed with water and crystallized from

alcohol to get brown coloured crystals.

Chapter II


Characterization




C H N

63.33

(63.41)

6.23

(6.10)

11.19



IR spectrum shows the band at 1550 cm-1

due to the presence of -NH2

group, the band at 1500 cm-1

corresponds to C=C stretching of aromatic

ring, the band at 1200 cm-1

is due to the presence of P=O group. The

aromatic C-H stretch appears at 3000 cm-1

.

Figure 2.8: FTIR spectrum of bis-(m-amino phenyl) methyl phosphine

oxide (BAPMPO)

Chapter II


4. Synthesis of bis-(m-hydroxy phenyl) methyl phosphine oxide from

bis-(m-amino phenyl) methyl phosphine oxide

The diazotization of bis-(m-amino phenyl) methyl phosphine oxide

was carried out at 0-5 OC using sodium nitrate solution in presence of

sulphuric acid. The resultant solution was poured into water at 80 OC. On

cooling hydrolyzed product was precipitated out. After filtration and

crystallization from ethanol pure product was obtained [18].

Characterization



(iii) Number of hydroxyl group: 1.94

(iv) Elemental analysis (%)

C H N

62.81

(62.90)

5.19

(5.24)

-----

----- (Calculated values are listed in parenthesis)

(v) Infra-red analysis

The band at 3200 cm-1

is due to the presence of –OH group

frequency. The band at 1260 cm-1

is due to the presence of P=O group.


is for Ar-OH symmetric stretching frequency.

C=C stretching of aromatic ring is obtained at 1470 cm-1

.

Chapter II


Figure 2.9: FTIR spectrum of bis-(m-hydroxy phenyl) methyl phosphine

oxide (BHPMPO)


Bis-(m-hydroxy phenyl) methyl phosphine oxide (BHPMPO, 1.0

mole, monomer) was charged into a three necked flask along with the

solvent methyl ethyl ketone (MEK) attached with a reflux condenser and

mechanical stirrer. Temperature was maintained at 60 OC and toluene

diisocyanate (TDI, 3.2 moles) was added in a dropwise manner over a

period of 1hour with constant stirring. Heating was continued for a period

of 2 hours with constant stirring. The polyurethane (PU-7) thus obtained

was vacuum distilled at 50 OC (Scheme 3) to get pure polymer.

Other polyurethanes (PU-8) and (PU-9) were also prepared in the

similar manner by reacting the monomer (BHPMPO) respectively with

isophoron diisocyanate (IPDI) and hexamethylene diisocyanate (HMDI).

Reaction conditions are given in the Table 2.4.3.

Chapter II


Reaction Scheme 3:

CH3 CH

3

CH3

CH3

CH3

CH2 (CH

2)

P P

CH3

O

P

CH3

ONO

2O2N

P

CH3

ONH

2NH2

P

CH3

OOHOH

P

CH3

OOO CO NH R NH CO

OCN-R-NCO

CH3I

Where R =

PU-7 PU-8 PU-9

Triphenyl phosphine

Diphenyl methyl phosphine oxide

Bis-(m-nitro phenyl) methyl phosphine oxide

Bis-(m-amino phenyl) methyl phosphine oxide

Bis-(m-hydroxy phenyl) methyl phosphine oxide (Monomer)

n

Diisocyanate

60 0C

MEK

Polyurethane resin

(i) in Petroleum ether and CHCl324 hrs at room temp.

(ii) Reflux in mix. of H2O and

aqueous KOH solution (40%)

Conc. HNO3

Conc. H2SO4

15 - 20 oC30 mon.

SnCl2.2H2O 90 - 95 oC1 hr

Conc. H2SO4

NaNO2

0 - 5 oC

6

Chapter II


Characterization

Table 2.3



System C H N

PU-7 62.08

(62.21)

4.47

(4.53)

9.23

(9.36)

PU-8 63.57

(63.25)

8.31

(8.40)

7.86

(7.98)

PU-9 59.47

(59.39)

6.54

(6.67)

9.32



IR-spectra of polyurethanes (PU-7 to PU-9) show the broad bands

around 3287-3388 cm-1

which attribute to >N-H bonds. The bands around

1502-1504 cm-1

and 1600-1679 cm-1

are due to –NHCOO groups. The

absorption bands around 2261-2290 cm-1

are due to free NCO groups in

the polyurethanes. The bands around 1056-1074 cm-1

and 1216-1220 cm-1

are due to P-O-C and P=O stretching frequencies respectively. The bands

around 2850 – 3000 cm-1

are due to the aromatic C-H stretching.

System Types of

isocyanate

used

Reaction

conditions

%

NCO

content

Intrinsic

viscosity

η

dl/gm

GPC

Data

Temp. OC

Time

hrs. Mn

Mw

Mn

PU-7 TDI 60 3 1.8 0.42 1822 1.5

PU-8 IPDI 60 3 1.7 0.39 1947 1.8

PU-9 HMDI 60 3 1.8 0.36 1628 1.6

Chapter II


Figure 2.10: FTIR spectra of polyurethanes based on bis-(m-hydroxy

phenyl) methyl phosphine oxide (PU-7 to PU-9)

Castor oil has been used in making a variety of polyurethane

products, ranging from coatings to foams, and the use of castor oil

derivatives continues to be an area of active development.

Chapter II


[d] Synthesis of polyurethanes based on ester exchange reaction

product (EERP) of castor oil and tris (m-hydroxy phenyl)

phosphate

(i) Synthesis of polyol

The ester exchange reaction product (EERP) was synthesized by

ester exchange reaction [20, 21] of castor oil with tris-(m-hydroxy

phenyl) phosphate (THPP). In this process castor oil and THPP were

mixed in equimolar proportion in a reaction flask equipped with a

thermometer, reflux condenser and overhead stirrer. The mixture was

refluxed for 4 hours at 140-150 OC followed by the heating for 6 hours at

170-180 OC to get the crude product which was vacuum distilled to obtain

high viscous polyol.

Characterization

(i) Percentage yield: 85-88 %

(ii) Number of hydroxyl group: 2.87


C H N

70.77

(71.17)

9.43

(9.14) -----



The IR spectrum of the phosphorous containing polyol shows broad

absorption band at 3417 cm-1

due to OH stretching frequency. The strong

band at 1739 cm-1

clearly indicates C=O stretching frequency of ester

group in polyol. The bands at 1058 cm-1

and 1172 cm-1

are due to P-O-C

and P=O stretching frequency respectively. The bands at 1619 cm-1

and

1463 cm-1

are due to C=C stretching frequency in aliphatic chain and

aromatic ring respectively. The aromatic C-H stretch appears at 3000

cm-1

.

Chapter II


Figure 2.11: FTIR spectrum of polyols based on ester exchange reaction

product of castor oil and tris (m-hydroxy phenyl) phosphate


Polyurethanes were synthesized by reacting this novel polyol

(EERP) with various diisocyanates such as TDI, IPDI, HMDI, and MDI.

To synthesize the polyurethane (PU-10), EERP (1.0 mole) and solvent

MEK were charged in a three necked flask equipped with a dropping

funnel, reflux condenser and mechanical stirrer. TDI (2.0 moles) was

added in a dropwise manner over a period of 1.5 hours with constant

stirring at 60 OC. Heating was continued for further 2 hours to complete

the reaction. In this reaction the ratio of EERP to TDI was kept 1:2 to get

a NCO terminated polyurethane. After vacuum distillation pure product

was obtained which have ricinoleic moiety in the structure (Scheme 4).

Other polyurethanes PU-11, PU-12 and PU-13 were also

synthesized by reacting the EERP with the diisocyanates such as

isophorone diisocyanate, hexamethylene diisocyanate and methylene

diphenyl diisocyanate respectively according to the reaction conditions

mentioned in Table 2.4.4.

Chapter II


Reaction Scheme 4:

Chapter II


Characterization

Table 2.4



System C H N

PU-10 68.11

(68.32)

7.34

(7.59)

4.39

(4.83)

PU-11 69.33

(68.94)

8.61

(8.78)

4.17

(4.47)

PU-12 65.09

(65.73)

8.22

(8.76)

4.89

(5.11)

PU-13 70.17

(70.51)

7.05

(7.31)

4.12



IR-spectra of polyurethanes (PU-10 to PU-13) show the broad

bands around 3315-3421 cm-1

which attribute to >N-H bonds. The bands

around 1541-1576 cm-1

and 1600-1635 cm-1

are due to –NHCOO groups.

The absorption bands around 2266-2275 cm-1

are due to free NCO groups

in polyurethanes. The bands around 1028-1076 cm-1

and 1199-1249 cm-1

are due to P-O-C and P=O stretching frequencies respectively. The bands

around 2900 – 3000 cm-1

are due to the aromatic C-H stretching.

System Types of

isocyanate

used

Reaction

conditions

%

NCO

content

Intrinsic

viscosity

η

dl/gm

GPC

Data

Temp. OC

Time

hrs. Mn

Mw

Mn

PU-10 TDI 60 3.5 1.8 0.92 4571 2.1

PU-11 IPDI 60 4.0 2.2 0.86 4873 2.3

PU-12 HMDI 60 4.5 2.1 0.81 3812 2.2

PU-13 MDI 60 3.5 2.0 0.95 4953 2.4

Chapter II


Figure 2.12: FTIR spectrum of polyurethanes based on ester exchange

reaction product (PU-10 to PU-13)

Chapter II


(ii) Diphosphorous based polyurethanes

[a] Synthesis of polyurethanes based on resorcinol bis-(hydroxyl

phenyl phosphonate)

(i) Synthesis of monomer: Resorcinol Bis-(Hydroxyl Phenyl

Phosphonate) (RBHPP)

The monomer resorcinol bis (hydroxyl phenyl phosphate) was

synthesized [22] by reacting resorcinol (1 mole, 110 gm) with phenyl

phosphonic dichloride (2.0 moles, 390 gm). In this reaction, resorcinol

and phenyl phosphonic dichloride were mixed in a round bottom flask

equipped with a condenser and dropping funnel and heated at 120 OC in

the xylene solvent for 8 hours with constant stirring. Water (2.0 mole, 36

ml) was added to the reaction mixture at room temperature with constant

stirring. Then the mixture was heated at 60 OC with continuous stirring

for 3 hours. The xylene was removed by vacuum distillation. The crude

product was washed with hot water and neutralized by sodium carbonate

solution and vacuum distilled to get final product (scheme-2).

Characterization

(i) Melting point: 153 – 155 OC

(ii) Percentage yield: 80 - 82%

(iii) Number of hydroxyl groups: 1.92

(iv) Solubility: MEK, MeOH, THF, DMF, etc.

(v) Elemental analysis (%)

(Calculated values are listed in parenthesis)

C H

54.98

(55.38)

4.03

(4.10)

Chapter II


(iv) Nuclear Magnetic Resonance (NMR) spectrum

The 1H – NMR signals of the monomer in DMSO give the value at

δ 7.30 – 7.40 ppm and δ 6.55 – 6.75 ppm for the aromatic protons of the

main chain while a broad multiplet around δ 6.75 – 7.30 ppm is

associated with the pendant phenyl rings. The broad band around δ 7.40 –

7.50 ppm is due to the presence of terminal hydroxyl groups.

Figure 2.13: 1H-NMR spectrum of resorcinol bis-(hydroxyl phenyl

phosphonate) (RBHPP)

(v) Infra-red spectrum

The IR spectrum of this diol (RBHPP) shows broad absorption

band at 3262 cm-1

due to OH stretching frequency. The bands at 982 cm-1

and 1133 cm-1

are due to P-O-C and P=O stretching frequencies

respectively. The band at 1479 cm-1

is due to C=C stretching frequency in

aromatic ring. The aromatic C-H stretch appears at 3000 cm-1

.

http://www.google.co.in/url?sa=t&rct=j&q=nmr%20spectroscopy&source=web&cd=1&cad=rja&ved=0CCAQFjAA&url=http%3A%2F%2Fen.wikipedia.org%2Fwiki%2FNuclear_magnetic_resonance_spectroscopy&ei=GhlKUOOwMYn5rQfCzIHIBQ&usg=AFQjCNGFGVMHlmrbJONO7SJhMMwHfNDtFw

Chapter II


Figure 2.14: FTIR spectrum of resorcinol bis-(hydroxyl phenyl

phosphonate) (RBHPP)


Polyurethanes were synthesized by reacting the above diol with

various diisocyanates such as toluene diisocyanate (TDI), isophorone

diisocyanate (IPDI) and hexamethylene diisocyanate (HMDI). To

synthesize the polyurethane (PU-14), diol (RBHPP, 1.0 mole) and solvent

MEK were charged in a three necked flask equipped with dropping

funnel, reflux condenser and stirrer. TDI (3.2 moles) was added in a

dropwise manner over a period of 1 hour with constant stirring at 60 OC.

Heating was continued for further 2 hours to complete the reaction. The

molar ratio of diol to TDI was kept 1 : 1.6 to produce NCO terminated

polyurethane. After vacuum distillation pure product was obtained

(scheme-5).

Chapter II


Other polyurethanes PU-15 and PU-16 were also synthesized by

reacting the diol with the diisocyanates, IPDI and HMDI respectively.


Reaction Scheme 5:

OH

OH

P

O

ClCl

NCO R NCO

n

OOP

O

P

O

O C

O

NH

R NH

C

O

OCR NH

O

C

O

NH

NCO

OOP

O

P

O

OH OH

CH3 CH

3

CH3

CH3

CH3

CH2 (CH

2)6

OOP

O

P

O

Cl Cl

OH2

+

60 0C3.5 hrs

Where R =

Resorcinol Phenyl Phosphonic Dichloride

Resorcinol bis-(chloro phenyl phosphonate)

Resorcinol bis-(hydroxy phenyl phosphonate)

Polyurethane resin based on resorcinol bis-(hydroxy phenyl phosphonate)

PU-14 PU-15 PU-16

Diisocyanate

120 0C, 8 hrs

60 0C, 3 hrs

Chapter II


Characterization

Table 2.5



System C H N

PU-14 58.01

(58.38)

3.97

(4.05)

7.21

(7.57)

PU-15 60.19

(60.43)

6.07

(6.24)

6.43

(6.72)

PU-16 62.59

(62.88)

3.83

(4.05)

6.49


(iii) Infra-red spectra




around 1503-1504 cm-1

and 1597-1600 cm-1

are due to –NHCOO-

groups. The absorption bands around 2263-2273 cm-1

are due to free

NCO groups in polyurethanes. The bands around 982-1068 cm-1

and

1171-1172 cm-1


respectively. The bands around 2900 – 3000 cm-1

are due to the aromatic

C-H bond stretching.

System Type of

isocyanate

used

Reaction

conditions

%

NCO

content

Intrinsic

viscosity

η

dl/gm

GPC

Data

Temp. OC

Time

hrs. Mn

Mw

Mn

PU-14 TDI 60 3 1.4 0.081 2303 1.8

PU-15 IPDI 60 3 1.4 0.079 2659 1.6

PU-16 HMDI 60 3 1.5 0.074 1929 1.7

Chapter II


Figure 2.15: FTIR spectra of polyurethanes based on resorcinol bis-

(hydroxyl phenyl phosphonate) (PU-14 to PU-16)

Chapter II


[b] Synthesis of polyurethanes based on bisphenol-A bis (hydroxyl

phenyl phosphate)

(i) Synthesis of monomer: Bisphenol-A bis (hydroxyl phenyl

phosphate) (BABHPP)

The monomer bisphenol-A bis (hydroxyl phenyl phosphate) was

synthesized by reacting bisphenol-A (1 mole, 222 gm) with phenyl

phosphonic dichloride (2.0 moles, 390 gm). In this reaction, bisphenol-A

and phenyl phosphonic dichloride were mixed in a round bottom flask

equipped with condenser, dropping funnel and heated at 140 OC in the

xylene solvent for 10 hours with constant stirring. Water (2.0 moles, 36

ml) was added to the reaction mixture at room temperature with constant

stirring. Then the mixture was heated at 60 OC with continuous stirring

for 4 hours. The xylene was removed by vacuum distillation. The crude

product was washed with hot water and neutralized by sodium carbonate

solution and vacuum filtered to get final product.

Characterization

(i) Melting point: 137 – 139 O

C

(ii) Percentage yield: 84 - 86%

(iii) Number of hydroxyl group: 1.93

(iv) Solubility: MEK, MeOH, THF, DMF, etc.


C H N

63.56

(63.78)

4.97

(5.12)

----

---- (Calculated values are listed in parenthesis)


The IR spectrum of phosphorous containing polyol shows broad

absorption at 3348 cm-1

due to OH stretching frequency. The bands at

Chapter II


1041 cm-1

and 1132 cm-1

are due to P-O-C and P=O stretching

frequencies respectively. The band at 1438 cm-1

is due to C=C stretching

frequency in aromatic ring. The aromatic C-H stretch appears at 3000

cm-1

.

Figure 2.16: FTIR spectrum of bisphenol-A bis (hydroxyl phenyl

phosphate) (BABHPP)


Polyurethanes were synthesized by reacting the above diol with

various diisocyanates such as toluene diisocyanate (TDI), isophorone

diisocyanate (IPDI) and hexamethylene diisocyanate (HMDI). To

synthesize the polyurethane (PU-17), diol (BABHPP, 1.0 mole) and

solvent MEK were charged in a three necked flask equipped with

dropping funnel, reflux condenser and stirrer. TDI (3.2 moles) was added

in a dropwise manner over a period of 1 hour with constant stirring at

60 OC. Heating was continued for further 2 hours to complete the

reaction. The molar ratio of diol to TDI was kept 1:1.6 to produce NCO

terminated polyurethane. After vacuum distillation pure product was

obtained (scheme-6).

Chapter II


Other polyurethanes PU-18 and PU-19 were also synthesized by

reacting the diol with the diisocyanates, IPDI and HMDI respectively.


Reaction Scheme 6:

P

O

ClCl

NCO R NCO

OP

O

OCC

O

NH

R NH

O

n

O P

O

O C

O

NH

R NH

C

O

C

CH3

CH3

C

CH3

CH3

OHOH

C

CH3

CH3

O P

O

ClOP

O

Cl

C

CH3

CH3

O P

O

OHOP

O

OH

CH3 CH

3

CH3

CH3

CH3

CH2 (CH

2)6

OH2

+

Diisocyanates

60 0C3.5 hrs

Phenyl phosphonic dichloride

Polyurethane resin

Bisphenol-A Bisphenol-A bis(chloro phenyl phosphonate)

Bisphenol-A bis(hydroxy phenyl phosphonate)

Where R =

PU-17 PU-18 PU-19

140 0C

10 hrs

60 0C, 4 hrs

Chapter II


Characterization

Table 2.6

(i) Reaction Conditions and Specification of the polyurethanes


System C H N

PU-17 62.38

(62.94)

4.16

(4.66)

6.03

(6.53)

PU-18 63.99

(64.29)

6.19

(6.51)

5.63

(5.88)

PU-19 66.05

(66.39)

4.27

(4.59)

5.48






around 1503-1504 cm-1

and 1599-1639 cm-1

are due to –NHCOO-

groups. The absorption bands around 2262-2272 cm-1

are due to free

NCO groups in polyurethanes. The bands around 1058-1068 cm-1

and

1172-1199 cm-1


respectively. The bands around 2850 – 3000 cm-1

are due to the aromatic

C-H bond stretching.

System Type of

isocyanate

used

Reaction

conditions

%

NCO

content

Intrinsic

viscosity

η

dl/gm

GPC

Data

Temp. OC

Time

hrs. Mn

Mw

Mn

PU-17 TDI 60 3 1.9 0.084 3557 1.7

PU-18 IPDI 60 3 1.5 0.081 3812 1.9

PU-19 HMDI 60 3 1.7 0.079 2825 1.6

Chapter II


Figure 2.17: FTIR spectra of polyurethanes based on bisphenol-A bis-

(hydroxyl phenyl phosphonate) (PU-17 to PU-19)

Chapter II


2.4.2 Synthesis of phosphorous based flame retardant epoxies

[a] Synthesis of triglycidyl ether of tris-(m-hydroxy phenyl)

phosphate

Triglycidyl ether of tris-(m-hydroxy phenyl) phosphate was

prepared by the reported method [14]. Tris-(m-hydroxy phenyl)

phosphate (50 gm, 0.134 moles), epichlorohydrine (185 gm, 2.0 moles)

and water (1-2 ml) were charged into a three necked flask equipped with

overhead stirrer, reflux condenser and dropping funnel. The reaction

mixture was stirred at 120 OC followed by the addition of 10% NaOH

solution over a period of 1.5 hours. The reaction mixture was further

heated at the same temperature for 3.5 hours. After completion of

reaction vacuum distillation was carried out to remove excess

epichlorohydrine. Toluene was added to extract the epoxy resin followed

by the vacuum distillation to get pure epoxy resin (Scheme 7).

Reaction Scheme 7:

PO O

O

OH

OHOHO

CH2

CH CH2 Cl

O

PO O

O

OO

CH2

CH CH2

O

Tris (m-hydroxy phenyl) phosphate

+

Epichlorohydrine

120 0C, 5 hrs

10% NaOH

3

Triglycidyl ether of tris (m-hydroxy phenyl) phosphate (TGETHPP)

Chapter II


Characterization

(i) Percentage yield: 80- 85 %

(ii) Epoxy equivalent weight (EEW): 202 gm/equiv.

(iii) Solubility: MEK, THF, DMF and Xylene.

(iv) Intrinsic viscosity (η) in MEK solvent: 0.0864 dl/gm

(v) Number average molecular weight ( Mn ): 1626

(vi) Polydispersity index (PDI, MnMw ): 1.6

(vii) Elemental analysis (%)

C H N

58.12

(59.70)

5.36

(4.90)

-----


(viii) Infra-red analysis

IR spectrum of epoxy resin shows absorption bands of terminal

epoxy group at 1259 cm-1

, 905 cm-1

and 842 cm-1

. The bands at 1042 cm-1

and 1169 cm-1


respectively. C=C stretching of aromatic ring is observed at 1496 cm-1

.


is due to the aromatic C-H bond stretching.

Figure 2.18: FTIR spectrum of Triglycidyl Ether of Tris (m-Hydroxy

Phenyl) Phosphate (TGETHPP)

Chapter II


[b] Synthesis of triglycidyl ether of tris-(bisphenol-A) monophosphate

Tris-(bisphenol-A) monophosphate (120 gm, 0.134 mole),

epichlorohydrine (185 gm, 2.0 moles) and water (1-2 ml) were charged

into a three necked flask equipped with overhead stirrer, reflux condenser

and dropping funnel. The reaction mixture was stirred at 120 OC followed

by the addition of 10% NaOH solution over a period of 1.5 hours. The

reaction mixture was further heated at the same temperature for 4 hours.

After completion of the reaction vacuum distillation was carried out to

remove excess epichlorohydrine. Toluene was added to extract the epoxy

resin followed by the vacuum distillation to get pure epoxy resin (Scheme

8).

Reaction Scheme 8:

CH2

CH CH2

Cl

O

PO O

O

C

CH3

CH3

O

O

CH2

CH CH2

O

HO OC

CH3

CH3

OHC

CH3

CH3

OH

CCH3

CH3

P O

O

O

Epichlorohydrine

120 0C, 5.5 hrs

10% NaOH

3

Triglycidyl ether of tris bisphenol-A mono phosphate (TGETBAMP)

+

Tris bisphenol-A monophosphate

Chapter II


Characterization

(i) Percentage yield: 78- 81 %

(ii) Epoxy equivalent weight (EEW): 309 gm/equiv.

(iii) Solubility: MEK, THF, DMF and Xylene.

(iv) Intrinsic viscosity (η) in MEK solvent: 0.0971 dl/gm

(v) Number average molecular weight ( Mn ): 2384

(vi) Polydispersity index (PDI, MnMw ): 1.5

(vii) Elemental analysis (%)

C H N

72.23

(72.32)

6.19

(6.36)

-----


(viii) Infra-red analysis

IR spectrum of epoxy resin shows absorption bands at 1220 cm-1

,

972 cm-1

and 830 cm-1

are due to terminal epoxy groups. The bands at

1011cm-1

and 1191cm-1

are due to P-O-C and P=O stretching

frequencies respectively. C=C stretching of aromatic ring is observed

at 1460 cm-1

. The aromatic C-H stretch appears at 3000 cm-1

.

Figure 2.19: FTIR spectrum of Triglycidyl Ether of Tris Bisphenol – A

Monophosphate (TGETBAMP)

Chapter II


2.4.3 Non-phosphorous containing liquid epoxy resin

Diglycidyl ether of bisphenol – A (DGEBA)

Diglycidyl ether of bisphenol-A (DGEBA) is available

commercially as LAPOX. It is a product of Atul Limited located at

Valsad, Gujarat. The structure of liquid epoxy resin is given below.

Characterization

(i) Epoxy equivalent weight: 190 gm/equiv.

(ii) Solubility: MEK, THF, DMF and Xylene.

(iii) Viscosity: 11500-11600 c.p.

(iv) Intrinsic viscosity (η) in MEK solvent: 0.037 dl/gm.


C H N

75.32

(75.00)

6.94

(7.05)

-----


These polymers have been used for the fabrication of casted films

and coatings which are discussed in the next chapter.

Chapter II


REFERENCES:

[1] Dutta, S. and Karak, N., Pigm. Resin Tech., 36, 74 (2007).

[2] Sung, P. H. and Wu, W. G., Euro. Polym. J., 30, 905 (1994).

[3] Li, Z., Huang, Y., Ren, D. and Zheng, Z., J. Cent. South Univ.

Techno., 15, 305 (2005).

[4] Lu S. Y. and Hamerton I., Prog. Polym. Sci., 27, 1661, 2002.

[5] Honarkar H. and Rahimi A., Chemical Monthly, 138, 923, 2007.

[6] Wang, P. S., Chiu, W. Y., Chen, L. W., Deng, B. L., Den, T. H. and

Chiu, Y. S., Polym. Degrad. Stab., 66, 307, 1999.

[7] Chen, X., Hu, Y., Song, L. and Xing, W., J. Fire Sci., 26, 93, 2008.

[8] Gouri, M. E., Bachiri, A. E., Hegazi, S. E., Rafik, M. and Harfi, A.

E., Polmy. Degrad. Stab., 94, 2101, 2009.

[9] Vogel, A. I., “Elemental Practical Organic Chemistry,Part-

3,Quantitative Organic Analysis, Second Edition, Delhi (CBS

publishers and distributers), 1987.

[10] Hepburn, C., Polyurethane Elastomers, 2nd Ed., Elsevier Science

Publishers Ltd, New York (1992).

[11] Lee, H. T., Hwang, Y. T., Chang, N. S., Huang, C. C. T. and Li, H.

C., Waterborne, High-Solid and Powder Coatings Symposium, New

Orleans, 22-24 February, 224 (1995).

[12] Lee, H. and Neuille, K., Hand Book of Epoxy Resin, McGraw-Hill,

New York (1967).

[13] Hou, S. S., Chung, Y. P., Chan, C. K. and Kuo, P. L., Polymer, 41,

3263-3272 (2000).

[14] Patel, S.R. and Patel, R.G., High Performance Polym., 3, 237

(1974).

[15] Patel, R.H. and Patel H.B., Prajna-J. Pure Appl. Sci. , 15,66-76

(2007).

Chapter II


[16] Thomas, E., Michael, Z., Dieter, W., Torsten, D. and Bernd, K.

(Bayer A-G, Germany).Ger. Offen.DE.19,914,137, C.A. 133,

26,76,11 V (2000).

[17] Jain P., Choudhary V. and Varma I. K., J. Appl. Polym. Sci., 81,

390-395 (2001).

[18] Rhone, P., (by Andre Rio).Fr.1, 288952, C.A. 58, 149a (1963).

[19] Nanjan, M. J., Balasubramaniam, M., Srinivasan, K. S. V. and

Santappa, M., Polymer, 19, 411, 1977.

[20] Kimura, M., Salee G., and Porter R. S., J. Appl. Polym. Sci. 29,

1629–1635, 1984.

[21] Kaushik, A., and Singh P., Int. J. Polym. Anal. Charact. 10, 373–

386, 2005.

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