research article evaluation of some conducting polymers as … · 2019. 5. 9. · research article...

Research ArticleEvaluation of Some Conducting Polymers asNovel Antioxidants for Rubber Vulcanizates

M A Abd El-Ghaffar1 K A Shaffei2 and Nourelhoda Abdelwahab1

1 Department of Polymers and Pigments National Research Centre Cairo Egypt2 Chemistry Department Faculty of Science Helwan University Cairo Egypt

Correspondence should be addressed to M A Abd El-Ghaffar mghaffar50yahoocom

Received 2 July 2013 Revised 25 August 2013 Accepted 21 September 2013 Published 9 February 2014

Academic Editor Ali Akbar Entezami

Copyright copy 2014 M A Abd El-Ghaffar et al This is an open access article distributed under the Creative Commons AttributionLicense which permits unrestricted use distribution and reproduction in any medium provided the original work is properlycited

Natural rubber (NR) and styrene-butadiene rubber (SBR) formulations containing polyaromatic and polyheterocyclic aminehomopolymers and copolymers were prepared The studied homopolymers named polythiophene (PT) poly(o-phenylenediamine) (Po-PDA) and copolymers named poly(aniline-co-m-toluidine) (PAn-co-mT) poly(aniline-co-o-phenylene diamine)(PAn-co-o-PDA) poly(aniline-co-thiophene) (PAn-co-T) poly(aniline-co-2-amino pyridine) (PAn-co-2APy) and poly(2-aminopyridine-co-o-phenylene diamine) (P2APy-co-o-PDA) have been prepared and characterized The rheological characteristics andphysicomechanical properties of the compounded rubber mixes and vulcanizates were investigated and determined The effects ofthe prepared polymers on the ageing characteristics of corresponding vulcanizates were evaluated It was found that the preparedpolymers have shown better antioxidant efficiency than the conventional antioxidants phenyl 120573 naphthyl amine (P120573N) and thepolymerized-224-trimethyl-12-dihydroquinoline (TMQ) industrially used in addition to their safety and ecofriendliness to theenvironment

1 Introduction

Natural rubber like any other organic polymer is susceptibleto oxidative degradation which results in loss of physicaland mechanical properties Its oxidation arises from theformation of peroxy-free radicals that can propagate scissionreactions of the rubber molecule [1 2] Antioxidants eithernatural or synthetic are essential additives to retard thisoxidation reaction

Antioxidants can be classified according to the way bywhich they interfere with the oxidation of the polymer asfollows

(a) Chain breaking donors (CB-D) are those which arecapable of competing with the substrate (RH) for the alkylperoxy radicals [1] The hindered phenols and aromaticamines such as substituted p-phenylene diamine [3] arethe most important of these antioxidants Some biologicalantioxidants such as tocopherols (vitamin E) also act byCB-Dmechanism

ROO∙ + AH(antioxidant)

CB-D997888rarr ROOH + A∙

(stable radical)(1)

(b) Chain breaking acceptors (CB-A) are antioxidantswhich can compete with oxygen for the alkyl radicalsQuinones [4] nitro compounds and stable oxyradicals areconsidered as CB-A antioxidants (1)

R +Q CB-A997888rarr RQ (2)

(c) Preventive antioxidants decompose hydroperoxidesby a process which does not give rise to free radicals or thatcan stabilize the hydroperoxide The phosphite esters and awhole family of sulfur-containing compounds are among thisset of compounds [1 5ndash7] (Scheme 1)

Abad et al [3] used natural antioxidants for radiationvulcanization of natural rubber among these were cystinetyrosine asparagines phenyl alanine and alanine

Kuriakose et al [7] used rice bran oil as a novelcompounding ingredient in sulfur vulcanization of naturalrubber

It is known that serious drawbacks of all antioxidantsexisting today are volatility and extractability The decreasein concentration of the antioxidants impairs the resistance

Hindawi Publishing CorporationInternational Journal of Polymer ScienceVolume 2014 Article ID 893542 9 pageshttpdxdoiorg1011552014893542

2 International Journal of Polymer Science

CH2

O

CH2 SHCH3 (CH2)

CH2

O

CH2 SCH3 (CH2)

H

O

CH2

O

CH2 S

O

CH3 (CH2)

H

O

CH2

O

CH2 SCH3 (CH2)

O

H

O

CH3 (CH2) CH2CH

Cn

O Cn

OROOH

2 2

+ ROH [1]

Cn

O

2

ROOH

D

Cn

O Cn

O+

[2]

[3]

+ ROH

+ ROH

[1]

For example SO2 SO3CH2SO4

Scheme 1

to degradation One method to increase the persistence ofthe antioxidant in polymer is to use high molecular weightcompounds which cannot migrate to the rubber surface andhence cannot be lost by volatilization [8]

Polyanilines are compounds which recently find wideapplications Polyanilines prepared by chemical oxidationprocesses for application as conducting polymers [9] andefficient corrosion inhibitors for steel protection [10] inaddition to their synergistic antioxidant efficiency for NR andSBR vulcanizates as reported in our previous studies [11ndash13]

The present study aims to prepare and evaluate thepreviously mentioned homopolymers and copolymers ofpolyaromatic amines polyheterocyclic compounds as antiox-idants for SBR vulcanizates and the role of chemical structureon their efficiencies

2 Experimental

Two homopolymers polythiophene (PT) and poly(o-phenylene diamine) (Po-PDA) and five copolymers poly(aniline-co-m-toluidine) (PAn-co-mT) poly (aniline-co-o-phenylene diamine) (PAn-co-o-PDA) poly(aniline-co-thiophene) (PAn-co-T) poly(aniline-co-2amino pyridine)(PAn-co-2APy) and poly (2-amino pyridine-co-o-phenylenediamine) (P2APy-co-o-PD) were synthesized and character-ized using spectrophotometric measurements (IR-UV-Vis)and thermal analysis The methods of preparation and char-acterization were reported by Abd El-Ghaffar et al in previ-ous publications [8ndash13] and can be summarized as follows

21 Preparation of (PT) and (Po-PDA) Homopolymers01mol of the conducting monomer in 50mL of the suitable

solvent and 001mol of ammonium peroxydisulphateinitiator was dissolved in 50mL distilled water The initiatorsolution was dropwised into themonomer solution with con-tinuous stirring for two hours at temperature range 0ndash5∘C

The precipitated conducting polymer was left for 24hours filtered and washed several times with distilled watermethanol and dried at 50∘C under vacuum The yield ge90was characterized examined for physical properties andevaluated as antioxidants for NR and SBR vulcanizates

22 Preparation of Various Conducting Copolymers 005molof aniline in 50mL methanol and 005mol of m-toluidinein 50mL methanol were mixed To this blend of the twoconducting monomer solutions was added dropwise withcontinuous stirring at 0ndash5∘C (01mol 22819 gm) of ammo-nium peroxydisulphate initiator in 50mL distilled waterwith continuous stirring for 6 hours and left overnight Thecopolymer was filtered off and the precipitate was washedseveral timeswith distilledwatermethanol and ethanol afterthat the precipitate was subjected for drying under vacuumin an electric oven at 50∘CThe precipitate was characterizedexamined for physical properties and evaluated as antioxi-dant for NR and SBR vulcanizates

The previous steps were repeated for all previously men-tioned copolymers

The rubber samples used in this investigation were nat-ural rubber (SMR-20) and styrene-butadiene rubber (SBR-1502)

The accelerator was N-cyclohexyl-2-benzothiazole sul-phenamide (CBS) and the activator used in this study wasstearic acid and zinc oxide

Elemental sulfur was used as curing agent

International Journal of Polymer Science 3

Antioxidant (TMQ) Primary accelerator CBS

224-Trimethyl-12-dihydroquinoline polymer

N

N

H

H

CH3

CH3

CH3

NN

H

SSC CH2

CHCH

2

CH2 CH2CH2

N-Cyclohexyl-2-benzothiazole sulfenamide

Phenyl120573ndashnaphthyl amine (P120573N) commercial antioxidant

n

Scheme 2

Themixes were prepared on a two-roll millThe rheomet-ric properties of the rubber mixes were determined by usingMonsantoOscillatingDisc Rheometer [14]The compoundedrubber was vulcanized in a hydraulic press at 152∘C Thephysicomechanical characteristics were determined accord-ing to standardmethods [15]The vulcanizates were subjectedto thermal oxidative ageing [16] in an oven at 90∘C fordifferent time periods The ageing data were compared withthose of vulcanizates containing the antioxidant phenyl 120573naphthyl amine (P120573N)The equilibrium swelling was carriedout in toluene [17] according to ASTMmethod D471 (2006)

The conducting polymers showing the best antioxidantresults for NR and SBR vulcanizates were tested for ageingand subjected toUV for 72 hr usingUV lamp (120w) in com-parison with the antioxidants (P120573N) and 224-trimethyl-12-dihydroquinoline polymer (TMQ) as commercial stabilizers(Scheme 2)

3 Results and Discussion

31 Effect of the Prepared Homopolymers and Copolymerson the Properties of Natural Rubber Mixes The preparedhomopolymers and copolymers were incorporated in naturalrubbermixes in a suitable dose (1 phr) comparedwith phenyl-120573-naphthyl amine (P120573N) the commercial antioxidant whichis widely used in rubber industry

The mixing process was carried out on a laboratory millaccording to the usual regime The rubber formulations aregiven in Table 1

The rheological characteristics of the mixes were deter-mined using an oscillating disc rheometer at 142 plusmn 1∘C andare given in Table 2

Table 1 Rubber formulations containing the prepared homopoly-mers and copolymers

Formulation no 1 2 3 4 5 6 7 8 9Control (without) mdash mdash mdash mdash mdash mdash mdash mdash mdashP120573N mdash 1 mdash mdash mdash mdash mdash mdash mdashPo-PDA mdash mdash 1 mdash mdash mdash mdash mdash mdashPT mdash mdash mdash 1 mdash mdash mdash mdash mdashP(An-co-mT) mdash mdash mdash mdash 1 mdash mdash mdash mdashP(An-co-T) mdash mdash mdash mdash mdash 1 mdash mdash mdashP(An-co-o-PDA) mdash mdash mdash mdash mdash 1 mdash mdashP(An-co-2APy) mdash mdash mdash mdash mdash mdash 1 mdashP(2APy-co-o-PDA) mdash mdash mdash mdash mdash mdash mdash 1Base recipe (phr) NR 100 stearic acid 2 zinc oxide 5 HAF 30 processingoil 3 CBS 1 S 2

The physicomechanical properties of the vulcanizateswere determined and are also given in Table 2

From these data it is clear that the prepared homopoly-mers and copolymers had an accelerating effect as shownfrom the decrease in the optimum cure time and the increasein cure rate index On the other hand it is obvious fromthe results of mechanical properties given also in Table 2and illustrated in Figures 1 2 and 3 that the preparedhomopolymers and copolymers increased stress at yieldstress at rupture strain at yield and strain at rupture whiledecreasing equilibrium swelling which indicates that thesepolymers can act also as secondary stabilizers

32 Effect of the Prepared Homopolymers and Copolymersas Antioxidants in Natural Rubber Mixes Oxidative ageing


Table 2 Rheometric characteristics and physico-mechanical properties of NR vulcanizates containing the prepared homopolymers andcopolymers

Property Formulation no1 2 3 4 5 6 7 8 9

Rheometric characteristics at 142∘C plusmn 1∘CMinimum torque119872

119871

dNsdotm 15 1 1 1 15 1 1 1 15Maximum torque119872

119867

dNsdotm 64 66 66 70 68 72 68 67 66Optimum cure time 119905

11988890

min 18 15 15 12 12 11 13 14 14Scorch time 119905

1199042

min 8 65 5 5 6 5 65 45 6Cure rate index CRT minminus1 10 1176 10 1429 1667 1667 1538 1176 125

Physicomechanical properties at the optimum cure timeStress at yield 120590

119861

MPa 204 223 22 2536 2323 2811 232 2252 2218Stress at rupture 120590

119877

MPa 193 212 218 2511 2311 274 2205 2233 2183Strain at yield 120576

119861

496 530 525 645 539 650 535 530 530Strain at rupture 120576

119877

503 540 530 647 541 670 540 533 531Equilibrium swelling Q 325 270 259 225 232 219 243 248 252119872119871 minimum torque119872

119867 maximum torque 119905

11988890 cure time to 90 of full torque development

11990511988890

cure time 1199051199042 scorch time to 2 units of torque increase above minimum torque

CRI cure rate index 100(11990511988890minus 1199051199042)

110

105

100

95

90

85

80

75

70

65

60

55

50

Reta

ined

stre

ss at

rupt

ure (

)

0 1 2 3 4 5 6 7 8

Control (without)PBN

P(An-co-mT)

P(An-co-o-PDA)P(An-co-2APy)Po-PDAP(2APy-co-o-PDA)PT

P(An-co-T)

Ageing time (days)

Figure 1 Retained strain at rupture versus ageing time for NR vul-canizates

of elastomers is a very serious problem during the ageingprocess small amounts of oxygen are absorbed by naturalor synthetic rubbers or by their vulcanizates This causes aconsiderable change in their physicomechanical propertiesconsequently it is necessary to protect rubber articles fromoxidative ageing by adding compounds called ldquoantioxidantsrdquoto rubber mixes

The addition of antioxidants to rubber mixes can prolongthe service life of the rubber vulcanizates however theefficiency of an antioxidant depends on different factors suchas the type of rubber the type of ageing and the nature of theother rubber ingredients in the mix

110

105

100

95

90

85

80

75

70

65

600 1 2 3 4 5 6 7 8


P(An-co-mT)


P(An-co-T)

Reta

ined

stra

in at

rupt

ure ()

Ageing time (days)

Figure 2 Retained stress at rupture versus ageing time for NRvulcanizates

The efficiency of the antioxidants also greatly depends ontheir chemical structure

In view of the above the natural rubber mixes shown inTable 1 were vulcanized at 142 plusmn 1∘C for their optimum curetimeThe rubber samples were subjected to thermal oxidativeageing in an oven at 90∘C plusmn 1∘C for different time periods

The physicomechanical properties of the aged sampleswere determined and the retained values of each propertywere calculated and represented in Figures 2 and 3 Fromthese figures it is clear that the retained values of tensilestrength and elongation at break depend on the ageing time

From these results it is obvious that the preparedhomopolymers and copolymers are more efficient to protect


0 1 2 3 4 5 6 7 8


P(An-co-mT)


P(An-co-T)

Reta

ined

equi

libriu

m sw

ellin

g (

)

108

102

96

90

84

78

72

66

60

Ageing time (days)

Figure 3 Retained equilibrium swelling versus ageing time for NRvulcanizates

Sn

Sn

Sn

O

O O

ROOH

ROOH

+ ROH

+ ROH

Scheme 3 Mechanism of polythiophene as an antioxidant (hydrop-eroxide decomposition reactions in presence of polythiophene)

natural rubber vulcanizates against thermal ageing practi-cally to higher levels than the widely used antioxidant PBNand to some extent in case of TMQ

Figure 3 depicts the dependence of the retained values ofequilibrium swelling in toluene as a function of ageing time

From the obtained results the efficiency of the preparedhomopolymers and copolymers can be arranged in thefollowing order

P(An-co-T) gt PT gt P(An-co-mT) gt P(An-co-o-PDA) gtP(An-co-2APy) gt P(o-PDA-co-2APy) gt Po-PDA = P120573N gtcontrol (without antioxidant)

It is quite evident that poly(aniline-co-thiophene) had thehighest efficiency as antioxidant and this is due to a mixedmechanism including the liability of hydrogen in polyanilinemoiety which blocks the peroxide radicals in addition tohydroperoxide decomposition in case of the polythiophenemoiety These results are in accordance with the resultsreported by Drake et al [18] (Scheme 3)

middotmiddotmiddotmiddot


SNH

S

n

mn

P (An-co-T)

P(T)

Scheme 4

Table 3 SBR formulations containing the prepared homopolymersand copolymers

Formulation no 11015840 21015840 31015840 41015840 51015840 61015840 71015840 81015840 91015840

Control (without) mdash mdash mdash mdash mdash mdash mdash mdash mdashP120573N mdash 1 mdash mdash mdash mdash mdash mdash mdashPo-PDA mdash mdash 1 mdash mdash mdash mdash mdash mdashPT mdash mdash mdash 1 mdash mdash mdash mdash mdashP(An-co-mT) mdash mdash mdash mdash 1 mdash mdash mdash mdashP(An-co-T) mdash mdash mdash mdash mdash 1 mdash mdash mdashP(An-co-o-PDA) mdash mdash mdash mdash mdash mdash 1 mdash mdashP(An-co-2APy) mdash mdash mdash mdash mdash mdash mdash 1 mdashP(2APy-co-o-PDA) mdash mdash mdash mdash mdash mdash mdash mdash 1Base recipe (phr) SBR 100 stearic acid 2 zinc oxide 5 HAF 30 processingoil 3 CBS 1 S 2

On the other hand polythiophene also produces goodresults due to high conjugation of thiophene ring whichattracts the lone pair of electrons of sulfur to a great extentwhich causes deficiency of electrons on sulfur atom so thatsulfur atom could capture the growing radicals formed onrubber molecules stopping the oxidation of rubber

The structures of poly(aniline-co-thiophene) P(An-co-T)and polythiophene (PT) are illustrated in Scheme 4

33 Effect of the Prepared Homopolymers and Copolymerson the Properties of Styrene-Butadiene Rubber (SBR) Theprepared homopolymers and copolymers were incorporatedin SBRmixes and compared with the commercial antioxidantP120573N as shown in Table 3

The rheometer characteristics of the rubber mixes weredetermined at 152∘C plusmn 1 using Monsanto Oscillating DiscRheometer 100 The samples were vulcanized at 152 plusmn 1∘Cfor their optimum cure time and their physicomechanicalproperties were determined

Table 4 shows the rheometer characteristics as well as thephysicomechanical properties of the rubber samples

From the data given in Table 4 it is clearly seen thatthe prepared homopolymers and copolymers decreased theoptimum cure time and increased the cure rate index Thisindicates that these compounds had an accelerating effect


Table 4 Rheometric characteristics and physico-mechanical properties of SBR vulcanizates containing the prepared homopolymers andcopolymers


Rheometric characteristics at 152 plusmn 1∘CMinimum torque119872

119871


119867


11988890

min 25 225 24 18 18 17 19 21 23Scorch time 119905

1199042



119861

Pa 1528 172 1758 244 2235 2612 218 195 1886Stress at rupture 120590

119877


119861


119877

338 372 375 460 444 483 420 417 383Equilibrium swelling Q 335 318 283 240 251 234 259 268 275

110

105

100

95

90

85

80

75

70

65

600 1 2 3 4 5 6 7 8


P(An-co-mT)


P(An-co-T)

Reta

ined

stra

in at

rupt

ure ()

Ageing time (days)

Figure 4 Retained strain at rupture versus ageing time for SBRvulcanizates

Also it is clearly noticed that the prepared polymersincreased the stress at yield stress at rupture strain at yieldand strain at rupture while they decreased the equilibriumswelling

From these results the prepared polymers may be used asantioxidants in SBR vulcanizates This is due to the presenceof reactive centers in their chemical structures in addition todouble bonds

Thus the evaluation of the prepared homopolymers andcopolymers as antioxidants for SBR vulcanizates is veryinteresting

34 Effect of the Prepared Homopolymers and Copolymersas Antioxidants in Styrene-Butadiene Rubber (SBR) MixesFrom the previous study it was found that the prepared

110

105

100

95

90

85

80

75

70

65

600 1 2 3 4 5 6 7 8


P(An-co-mT)


P(An-co-T)

Reta

ined

equi

libriu

m sw

ellin

g (

)

Figure 5 Retained stress at rupture versus ageing time for SBRvulcanizates

homopolymers and copolymers proved themselves to becompounds of the highest efficiency as antioxidants in SBRvulcanizates Thus it is of great interest to study the effect ofthese compounds as antioxidants for the synthetic styrene-butadiene rubber

The rubber samples were vulcanized at their optimumcure time The vulcanizates were subjected to thermal ageingat 90∘C in an electric oven as previously described fordifferent periods of time

The physicomechanical properties of the aged sampleswere determined and the retained values of each propertywere calculated

Figures 4 and 5 represent the dependence of both stressand strain at rupture on the ageing time for rubber samplescontaining the investigated homopolymers and copolymers


110

105

100

95

90

85

80

75

70

65

600 1 2 3 4 5 6 7 8


P(An-co-mT)


P(An-co-T)

Reta

ined

equi

libriu

m sw

ellin

g (

)

Figure 6 Retained equilibrium swelling versus ageing time for SBRvulcanizates

Table 5 NR formulations containing the prepared P(An-co-T) andPT

Formulation no 10 11 12 13 14Control (without) mdash mdash mdash mdash mdashP120573N mdash 1 mdash mdash mdashTMQ mdash mdash 1 mdash mdashP(An-co-T) mdash mdash mdash 1 mdashPT mdash mdash mdash mdash 1


119871

dNsdotm 2 1 1 1 1Maximum torque119872

119867

dNsdotm 70 69 695 70 72Optimum cure time 119905

11988890

min 13 12 11 12 11Physicomechanical properties at the optimum cure time

Stress at rupture 120590119877

MPa 1784 1875 198 274 2510Strain at rupture 120576

119877

765 857 705 670 647Base recipe (phr) NR 100 stearic acid 2 zinc oxide 5 HAF 30 processingoil 3 CBS 1 S 2

The obtained results of equilibrium swelling as shown inFigure 6 also ensure the above results

From the previous ageing results of NR and SBR it isclearly seen that poly(aniline-co-thiophene) and polythio-phene can be considered as the most efficient antioxidantsin comparison with other prepared homopolymers andcopolymers These two polymers were examined for theirantioxidant performance andUV stabilization in comparisonwith the commercial antioxidants P120573NandTMQThe formu-lations are given in Tables 5 and 6

The results of retained stress at rupture and retained strainat rupture for aged NR and SBR vulcanizates are illustrated inFigures 7 8 9 and 10 respectively

From these results it is clearly seen that the preparedpolymers of P(An-co-T) and PT have shown outstandingproperties which are more superior than the commercial

Table 6 SBR Formulations containing prepared P(An-co-T) andPT



119871


119867


11988890




119877

624 662 651 670 647Base recipe (phr) SBR 100 stearic acid 2 zinc oxide 5 HAF 30 processingoil 3 CBS 1 S 2

0

20

40

60

80

100

120

0 2 4 6 8

PTPBN

TMOControl

Reta

ined

stre

ss at

rupt

ure (

)

P(An-co-T)

Ageing time (days)


antioxidants P120573N and TMQ These polymers are safe andenvironmentally acceptable [8 10] and characterized withtheir easy method for preparation

35 Effect of UV Exposure [19] on the Properties of RubberVulcanizates Containing P(An-co-T) and PT in Comparisonwith P120573N and TMQ The rubber vulcanizates of control andthose containing 1 phr of the polymers P(An-co-T) PT com-pared with P120573N and TMQ were subjected to UV irradiationfor 72 hrs The mechanical properties of the exposed samples(mainly stress at rupture and strain at rupture)were examinedand evaluated and showed better results than P120573N and TMQThe data are given in Table 7

4 Conclusions

Some conducting polymers include poly(aniline-co-thi-ophene) poly(aniline-co-2-amino pyridine) poly(2-amino


Table 7 Retained stress and strain at rupture for NR and SBR vulcanizates containing the commercial antioxidants P120573N TMQ and preparedpolymers of P(An-co-T) and PT after exposure to UV irradiation for 72 hr

Formulation propertyNR vulcanizates SBR vulcanizates

Control P120573N TMQ P(An-co-T) PT Control P120573N TMQ P(An-co-T) PT10 11 12 13 14 15 16 17 18 19

Ret stress at rupt after 72 hr UV exposure 89 98 100 100 100 90 99 93 100 100Ret strain at rupt after 72 hr UV exposure 90 98 100 100 100 91 99 94 100 100

0

20

40

60

80

100

120

0 2 4 6 8

TMQPBNP(An-co-T)

Control

Reta

ined

stra

in at

rupt

ure (

)

Ageing time (days)

PT

Figure 8 Retained strain at rupture versus ageing time for NRvulcanizates

0

20

40

60

80

100

120

0 2 4 6 8

PBNTMQControl

P(An-co-T)

Reta

ined

stre

ss at

rupt

ure (

)

Ageing time (days)

PT


pyridine-co-o-phenylene diamine) and poly(thiophene)were prepared and characterized The polymers were exam-ined for their antioxidant efficiency and UV protection forNR and SBR vulcanizates compared with the commercialantioxidants P120573N and TMQ The prepared polymers ofP(An-co-T) and PT showed high antioxidant performanceexceeding the commercial antioxidants in addition to

reta

ined

stra

in at

rupt

ure (

)

0

20

40

60

80

100

120

0 2 4 6 8

PBNTMQControl

P(An-co-T)

Ageing time (days)

PT


their safety environmental acceptance and easy way ofpreparation The data indicated also that the polymers canact as secondary accelerators in addition to their antioxidantefficiency

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

References

[1] S Al-Malaika ldquoMechanisms of antioxidant action and stabilisa-tion technologymdashthe Aston experiencerdquo Polymer Degradationand Stability vol 34 no 1ndash3 pp 1ndash36 1991

[2] D Barnard and P M Lewis ldquoOxidative agingrdquo Natural RubberScience amp Technology pp 621ndash675 1988

[3] L V Abad L S Relleve C T Aranilla A K Aliganga CM SanDiego and AM Dela Rosa ldquoNatural antioxidants for radiationvulcanization of natural rubber latexrdquo Polymer Degradation andStability vol 76 no 2 pp 275ndash279 2002

[4] MW Sabaa T M Madkour and A A Yassin ldquoPolymerizationproducts of p-benzoquinone as bound antioxidants for blendsof natural rubberrdquo Polymer Degradation and Stability vol 26no 4 pp 347ndash359 1989

[5] M Giurginca J M Herdan L Cira G Valeanu and G IvanldquoGrafted mercapto-135-triazinic antioxidants for elastomersrdquoPolymer Degradation and Stability vol 36 no 1 pp 53ndash57 1992


[6] HMeier PDubsHKunzi et al ldquoSome aspects of a new class ofsulfur containing phenolic antioxidantsrdquo Polymer Degradationand Stability vol 49 no 1 pp 1ndash9 1995

[7] A P Kuriakose and G Rajendran ldquoRice bran oil as a novelcompounding ingredient in sulphur vulcanization of naturalrubberrdquo European Polymer Journal vol 31 no 6 pp 595ndash6021995

[8] M N Ismail M S Ibrahim and M A Abd El-Ghaffar ldquoPoly-aniline as an antioxidant and antirad in SBR vulcanizatesrdquoPolymer Degradation and Stability vol 62 no 2 pp 337ndash3411998

[9] M A Abd El-Ghaffar N A Mohamed A A Ghoneim and KA Shaffei ldquoCharacterization and electrical properties of somehydrochloric acid-doped aniline and 2-amino-pyridine hom-opolymers and copolymersrdquo Polymer-Plastics Technology andEngineering vol 45 no 12 pp 1327ndash1338 2006

[10] M A Abd El-Ghaffar E A M Youssef W M Darwish and FM Helaly ldquoA novel series of corrosion inhibitive polymers forsteel protectionrdquo Journal of Elastomers and Plastics vol 30 no1 pp 68ndash94 1998

[11] F M Helaly W M Darwich and M A Abd El-Ghaffar ldquoEffectof some polyaromatic amines on the properties of NR and SBRvulcanizatesrdquo Polymer Degradation and Stability vol 64 no 2pp 251ndash257 1999

[12] A A Wazzan M N Ismail and M A Abd El Ghaffar ldquoEval-uation of some polyaromatic amines as antirads and antifatigueagents in SBR vulcanizatesrdquo International Journal of PolymerAnalysis and Characterization vol 10 no 1-2 pp 57ndash69 2005

[13] M N Ismail M A Abd El Ghaffar K A Shaffei and N AMohamed ldquoSome novel polyamines as antioxidants for SBRvulcanizatesrdquo Polymer Degradation and Stability vol 63 no 3pp 377ndash383 1999

[14] ASTM D 2084-76T ldquoFor determination of the rheometercharacteristics using a Monsanto Oscillating Disc Rheometer100rdquo 1972

[15] ASTM D 412-66T ldquoFor determination of Physico-mechanicalproperties using Zwick tensile testing machine (model 1425)rdquo1967

[16] ASTM D 573 ldquoFor carrying out the ageing of samples in anelectric ovenrdquo 1952

[17] ASTM D471 ldquoFor determination of swelling in toluenerdquo 2006[18] W O Drake J R Pauquet J Zingg and H Zweifel ldquoStabili-

zation of polymeric materials state-of-the-art scope and limi-tationsrdquo Polymer Preprints vol 34 no 2 p 174 1993

[19] H Zweifel Stabilization of Polymeric Materials Springer Hei-delberg Germany 1997

Submit your manuscripts athttpwwwhindawicom

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CorrosionInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Polymer ScienceInternational Journal of



CeramicsJournal of


CompositesJournal of

NanoparticlesJournal of



International Journal of

Biomaterials


NanoscienceJournal of

TextilesHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Journal of

NanotechnologyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

CrystallographyJournal of


The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014


CoatingsJournal of

Advances in

Materials Science and EngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Smart Materials Research



MetallurgyJournal of


BioMed Research International

MaterialsJournal of


Nano

materials


Journal ofNanomaterials


CH2

O

CH2 SHCH3 (CH2)

CH2

O

CH2 SCH3 (CH2)

H

O

CH2

O

CH2 S

O

CH3 (CH2)

H

O

CH2

O

CH2 SCH3 (CH2)

O

H

O

CH3 (CH2) CH2CH

Cn

O Cn

OROOH

2 2

+ ROH [1]

Cn

O

2

ROOH

D

Cn

O Cn

O+

[2]

[3]

+ ROH

+ ROH

[1]

For example SO2 SO3CH2SO4

Scheme 1

to degradation One method to increase the persistence ofthe antioxidant in polymer is to use high molecular weightcompounds which cannot migrate to the rubber surface andhence cannot be lost by volatilization [8]

Polyanilines are compounds which recently find wideapplications Polyanilines prepared by chemical oxidationprocesses for application as conducting polymers [9] andefficient corrosion inhibitors for steel protection [10] inaddition to their synergistic antioxidant efficiency for NR andSBR vulcanizates as reported in our previous studies [11ndash13]

The present study aims to prepare and evaluate thepreviously mentioned homopolymers and copolymers ofpolyaromatic amines polyheterocyclic compounds as antiox-idants for SBR vulcanizates and the role of chemical structureon their efficiencies

2 Experimental

Two homopolymers polythiophene (PT) and poly(o-phenylene diamine) (Po-PDA) and five copolymers poly(aniline-co-m-toluidine) (PAn-co-mT) poly (aniline-co-o-phenylene diamine) (PAn-co-o-PDA) poly(aniline-co-thiophene) (PAn-co-T) poly(aniline-co-2amino pyridine)(PAn-co-2APy) and poly (2-amino pyridine-co-o-phenylenediamine) (P2APy-co-o-PD) were synthesized and character-ized using spectrophotometric measurements (IR-UV-Vis)and thermal analysis The methods of preparation and char-acterization were reported by Abd El-Ghaffar et al in previ-ous publications [8ndash13] and can be summarized as follows

21 Preparation of (PT) and (Po-PDA) Homopolymers01mol of the conducting monomer in 50mL of the suitable

solvent and 001mol of ammonium peroxydisulphateinitiator was dissolved in 50mL distilled water The initiatorsolution was dropwised into themonomer solution with con-tinuous stirring for two hours at temperature range 0ndash5∘C

The precipitated conducting polymer was left for 24hours filtered and washed several times with distilled watermethanol and dried at 50∘C under vacuum The yield ge90was characterized examined for physical properties andevaluated as antioxidants for NR and SBR vulcanizates

22 Preparation of Various Conducting Copolymers 005molof aniline in 50mL methanol and 005mol of m-toluidinein 50mL methanol were mixed To this blend of the twoconducting monomer solutions was added dropwise withcontinuous stirring at 0ndash5∘C (01mol 22819 gm) of ammo-nium peroxydisulphate initiator in 50mL distilled waterwith continuous stirring for 6 hours and left overnight Thecopolymer was filtered off and the precipitate was washedseveral timeswith distilledwatermethanol and ethanol afterthat the precipitate was subjected for drying under vacuumin an electric oven at 50∘CThe precipitate was characterizedexamined for physical properties and evaluated as antioxi-dant for NR and SBR vulcanizates

The previous steps were repeated for all previously men-tioned copolymers

The rubber samples used in this investigation were nat-ural rubber (SMR-20) and styrene-butadiene rubber (SBR-1502)

The accelerator was N-cyclohexyl-2-benzothiazole sul-phenamide (CBS) and the activator used in this study wasstearic acid and zinc oxide

Elemental sulfur was used as curing agent




N

N

H

H

CH3

CH3

CH3

NN

H

SSC CH2

CHCH

2

CH2 CH2CH2



n

Scheme 2
















119871


119867


11988890

min 18 15 15 12 12 11 13 14 14Scorch time 119905

1199042



119861


119877


119861


119877




11990511988890



110

105

100

95

90

85

80

75

70

65

60

55

50

Reta

ined

stre

ss at

rupt

ure (

)

0 1 2 3 4 5 6 7 8


P(An-co-mT)


P(An-co-T)

Ageing time (days)




110

105

100

95

90

85

80

75

70

65

600 1 2 3 4 5 6 7 8


P(An-co-mT)


P(An-co-T)

Reta

ined

stra

in at

rupt

ure ()

Ageing time (days)







0 1 2 3 4 5 6 7 8


P(An-co-mT)


P(An-co-T)

Reta

ined

equi

libriu

m sw

ellin

g (

)

108

102

96

90

84

78

72

66

60

Ageing time (days)


Sn

Sn

Sn

O

O O

ROOH

ROOH

+ ROH

+ ROH









SNH

S

n

mn

P (An-co-T)

P(T)

Scheme 4


Formulation no 11015840 21015840 31015840 41015840 51015840 61015840 71015840 81015840 91015840












119871


119867


11988890

min 25 225 24 18 18 17 19 21 23Scorch time 119905

1199042



119861


119877


119861


119877


110

105

100

95

90

85

80

75

70

65

600 1 2 3 4 5 6 7 8


P(An-co-mT)


P(An-co-T)

Reta

ined

stra

in at

rupt

ure ()

Ageing time (days)






110

105

100

95

90

85

80

75

70

65

600 1 2 3 4 5 6 7 8


P(An-co-mT)


P(An-co-T)

Reta

ined

equi

libriu

m sw

ellin

g (

)







110

105

100

95

90

85

80

75

70

65

600 1 2 3 4 5 6 7 8


P(An-co-mT)


P(An-co-T)

Reta

ined

equi

libriu

m sw

ellin

g (

)





119871


119867


11988890




119877









119871


119867


11988890




119877


0

20

40

60

80

100

120

0 2 4 6 8

PTPBN

TMOControl

Reta

ined

stre

ss at

rupt

ure (

)

P(An-co-T)

Ageing time (days)




4 Conclusions







0

20

40

60

80

100

120

0 2 4 6 8

TMQPBNP(An-co-T)

Control

Reta

ined

stra

in at

rupt

ure (

)

Ageing time (days)

PT


0

20

40

60

80

100

120

0 2 4 6 8

PBNTMQControl

P(An-co-T)

Reta

ined

stre

ss at

rupt

ure (

)

Ageing time (days)

PT



reta

ined

stra

in at

rupt

ure (

)

0

20

40

60

80

100

120

0 2 4 6 8

PBNTMQControl

P(An-co-T)

Ageing time (days)

PT





References




























CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials






N

N

H

H

CH3

CH3

CH3

NN

H

SSC CH2

CHCH

2

CH2 CH2CH2



n

Scheme 2
















119871


119867


11988890

min 18 15 15 12 12 11 13 14 14Scorch time 119905

1199042



119861


119877


119861


119877




11990511988890



110

105

100

95

90

85

80

75

70

65

60

55

50

Reta

ined

stre

ss at

rupt

ure (

)

0 1 2 3 4 5 6 7 8


P(An-co-mT)


P(An-co-T)

Ageing time (days)




110

105

100

95

90

85

80

75

70

65

600 1 2 3 4 5 6 7 8


P(An-co-mT)


P(An-co-T)

Reta

ined

stra

in at

rupt

ure ()

Ageing time (days)







0 1 2 3 4 5 6 7 8


P(An-co-mT)


P(An-co-T)

Reta

ined

equi

libriu

m sw

ellin

g (

)

108

102

96

90

84

78

72

66

60

Ageing time (days)


Sn

Sn

Sn

O

O O

ROOH

ROOH

+ ROH

+ ROH









SNH

S

n

mn

P (An-co-T)

P(T)

Scheme 4


Formulation no 11015840 21015840 31015840 41015840 51015840 61015840 71015840 81015840 91015840












119871


119867


11988890

min 25 225 24 18 18 17 19 21 23Scorch time 119905

1199042



119861


119877


119861


119877


110

105

100

95

90

85

80

75

70

65

600 1 2 3 4 5 6 7 8


P(An-co-mT)


P(An-co-T)

Reta

ined

stra

in at

rupt

ure ()

Ageing time (days)






110

105

100

95

90

85

80

75

70

65

600 1 2 3 4 5 6 7 8


P(An-co-mT)


P(An-co-T)

Reta

ined

equi

libriu

m sw

ellin

g (

)







110

105

100

95

90

85

80

75

70

65

600 1 2 3 4 5 6 7 8


P(An-co-mT)


P(An-co-T)

Reta

ined

equi

libriu

m sw

ellin

g (

)





119871


119867


11988890




119877









119871


119867


11988890




119877


0

20

40

60

80

100

120

0 2 4 6 8

PTPBN

TMOControl

Reta

ined

stre

ss at

rupt

ure (

)

P(An-co-T)

Ageing time (days)




4 Conclusions







0

20

40

60

80

100

120

0 2 4 6 8

TMQPBNP(An-co-T)

Control

Reta

ined

stra

in at

rupt

ure (

)

Ageing time (days)

PT


0

20

40

60

80

100

120

0 2 4 6 8

PBNTMQControl

P(An-co-T)

Reta

ined

stre

ss at

rupt

ure (

)

Ageing time (days)

PT



reta

ined

stra

in at

rupt

ure (

)

0

20

40

60

80

100

120

0 2 4 6 8

PBNTMQControl

P(An-co-T)

Ageing time (days)

PT





References




























CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials







119871


119867


11988890

min 18 15 15 12 12 11 13 14 14Scorch time 119905

1199042



119861


119877


119861


119877




11990511988890



110

105

100

95

90

85

80

75

70

65

60

55

50

Reta

ined

stre

ss at

rupt

ure (

)

0 1 2 3 4 5 6 7 8


P(An-co-mT)


P(An-co-T)

Ageing time (days)




110

105

100

95

90

85

80

75

70

65

600 1 2 3 4 5 6 7 8


P(An-co-mT)


P(An-co-T)

Reta

ined

stra

in at

rupt

ure ()

Ageing time (days)







0 1 2 3 4 5 6 7 8


P(An-co-mT)


P(An-co-T)

Reta

ined

equi

libriu

m sw

ellin

g (

)

108

102

96

90

84

78

72

66

60

Ageing time (days)


Sn

Sn

Sn

O

O O

ROOH

ROOH

+ ROH

+ ROH









SNH

S

n

mn

P (An-co-T)

P(T)

Scheme 4


Formulation no 11015840 21015840 31015840 41015840 51015840 61015840 71015840 81015840 91015840












119871


119867


11988890

min 25 225 24 18 18 17 19 21 23Scorch time 119905

1199042



119861


119877


119861


119877


110

105

100

95

90

85

80

75

70

65

600 1 2 3 4 5 6 7 8


P(An-co-mT)


P(An-co-T)

Reta

ined

stra

in at

rupt

ure ()

Ageing time (days)






110

105

100

95

90

85

80

75

70

65

600 1 2 3 4 5 6 7 8


P(An-co-mT)


P(An-co-T)

Reta

ined

equi

libriu

m sw

ellin

g (

)







110

105

100

95

90

85

80

75

70

65

600 1 2 3 4 5 6 7 8


P(An-co-mT)


P(An-co-T)

Reta

ined

equi

libriu

m sw

ellin

g (

)





119871


119867


11988890




119877









119871


119867


11988890




119877


0

20

40

60

80

100

120

0 2 4 6 8

PTPBN

TMOControl

Reta

ined

stre

ss at

rupt

ure (

)

P(An-co-T)

Ageing time (days)




4 Conclusions







0

20

40

60

80

100

120

0 2 4 6 8

TMQPBNP(An-co-T)

Control

Reta

ined

stra

in at

rupt

ure (

)

Ageing time (days)

PT


0

20

40

60

80

100

120

0 2 4 6 8

PBNTMQControl

P(An-co-T)

Reta

ined

stre

ss at

rupt

ure (

)

Ageing time (days)

PT



reta

ined

stra

in at

rupt

ure (

)

0

20

40

60

80

100

120

0 2 4 6 8

PBNTMQControl

P(An-co-T)

Ageing time (days)

PT





References




























CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




0 1 2 3 4 5 6 7 8


P(An-co-mT)


P(An-co-T)

Reta

ined

equi

libriu

m sw

ellin

g (

)

108

102

96

90

84

78

72

66

60

Ageing time (days)


Sn

Sn

Sn

O

O O

ROOH

ROOH

+ ROH

+ ROH









SNH

S

n

mn

P (An-co-T)

P(T)

Scheme 4


Formulation no 11015840 21015840 31015840 41015840 51015840 61015840 71015840 81015840 91015840












119871


119867


11988890

min 25 225 24 18 18 17 19 21 23Scorch time 119905

1199042



119861


119877


119861


119877


110

105

100

95

90

85

80

75

70

65

600 1 2 3 4 5 6 7 8


P(An-co-mT)


P(An-co-T)

Reta

ined

stra

in at

rupt

ure ()

Ageing time (days)






110

105

100

95

90

85

80

75

70

65

600 1 2 3 4 5 6 7 8


P(An-co-mT)


P(An-co-T)

Reta

ined

equi

libriu

m sw

ellin

g (

)







110

105

100

95

90

85

80

75

70

65

600 1 2 3 4 5 6 7 8


P(An-co-mT)


P(An-co-T)

Reta

ined

equi

libriu

m sw

ellin

g (

)





119871


119867


11988890




119877









119871


119867


11988890




119877


0

20

40

60

80

100

120

0 2 4 6 8

PTPBN

TMOControl

Reta

ined

stre

ss at

rupt

ure (

)

P(An-co-T)

Ageing time (days)




4 Conclusions







0

20

40

60

80

100

120

0 2 4 6 8

TMQPBNP(An-co-T)

Control

Reta

ined

stra

in at

rupt

ure (

)

Ageing time (days)

PT


0

20

40

60

80

100

120

0 2 4 6 8

PBNTMQControl

P(An-co-T)

Reta

ined

stre

ss at

rupt

ure (

)

Ageing time (days)

PT



reta

ined

stra

in at

rupt

ure (

)

0

20

40

60

80

100

120

0 2 4 6 8

PBNTMQControl

P(An-co-T)

Ageing time (days)

PT





References




























CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials







119871


119867


11988890

min 25 225 24 18 18 17 19 21 23Scorch time 119905

1199042



119861


119877


119861


119877


110

105

100

95

90

85

80

75

70

65

600 1 2 3 4 5 6 7 8


P(An-co-mT)


P(An-co-T)

Reta

ined

stra

in at

rupt

ure ()

Ageing time (days)






110

105

100

95

90

85

80

75

70

65

600 1 2 3 4 5 6 7 8


P(An-co-mT)


P(An-co-T)

Reta

ined

equi

libriu

m sw

ellin

g (

)







110

105

100

95

90

85

80

75

70

65

600 1 2 3 4 5 6 7 8


P(An-co-mT)


P(An-co-T)

Reta

ined

equi

libriu

m sw

ellin

g (

)





119871


119867


11988890




119877









119871


119867


11988890




119877


0

20

40

60

80

100

120

0 2 4 6 8

PTPBN

TMOControl

Reta

ined

stre

ss at

rupt

ure (

)

P(An-co-T)

Ageing time (days)




4 Conclusions







0

20

40

60

80

100

120

0 2 4 6 8

TMQPBNP(An-co-T)

Control

Reta

ined

stra

in at

rupt

ure (

)

Ageing time (days)

PT


0

20

40

60

80

100

120

0 2 4 6 8

PBNTMQControl

P(An-co-T)

Reta

ined

stre

ss at

rupt

ure (

)

Ageing time (days)

PT



reta

ined

stra

in at

rupt

ure (

)

0

20

40

60

80

100

120

0 2 4 6 8

PBNTMQControl

P(An-co-T)

Ageing time (days)

PT





References




























CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




110

105

100

95

90

85

80

75

70

65

600 1 2 3 4 5 6 7 8


P(An-co-mT)


P(An-co-T)

Reta

ined

equi

libriu

m sw

ellin

g (

)





119871


119867


11988890




119877









119871


119867


11988890




119877


0

20

40

60

80

100

120

0 2 4 6 8

PTPBN

TMOControl

Reta

ined

stre

ss at

rupt

ure (

)

P(An-co-T)

Ageing time (days)




4 Conclusions







0

20

40

60

80

100

120

0 2 4 6 8

TMQPBNP(An-co-T)

Control

Reta

ined

stra

in at

rupt

ure (

)

Ageing time (days)

PT


0

20

40

60

80

100

120

0 2 4 6 8

PBNTMQControl

P(An-co-T)

Reta

ined

stre

ss at

rupt

ure (

)

Ageing time (days)

PT



reta

ined

stra

in at

rupt

ure (

)

0

20

40

60

80

100

120

0 2 4 6 8

PBNTMQControl

P(An-co-T)

Ageing time (days)

PT





References




























CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials








0

20

40

60

80

100

120

0 2 4 6 8

TMQPBNP(An-co-T)

Control

Reta

ined

stra

in at

rupt

ure (

)

Ageing time (days)

PT


0

20

40

60

80

100

120

0 2 4 6 8

PBNTMQControl

P(An-co-T)

Reta

ined

stre

ss at

rupt

ure (

)

Ageing time (days)

PT



reta

ined

stra

in at

rupt

ure (

)

0

20

40

60

80

100

120

0 2 4 6 8

PBNTMQControl

P(An-co-T)

Ageing time (days)

PT





References




























CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials

























CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials



research article evaluation of some conducting polymers as … · 2019. 5. 9. · research article...

Documents