Physicochemical, Thermomechanical, and Swelling Properties of

Hindawi Publishing CorporationISRN Polymer ScienceVolume 2013 Article ID 621352 8 pageshttpdxdoiorg1011552013621352

Research ArticlePhysicochemical Thermomechanical and SwellingProperties of Radiation Vulcanised Natural RubberLatex Film Effect of Diospyros peregrina Fruit Extracts

Kazi Md Zakir Hossain12 Nashid Sharif2 N C Dafader3

M E Haque3 and A M Sarwaruddin Chowdhury4

1 Division of Materials Mechanics and Structures Faculty of Engineering University of Nottingham Nottingham NG7 2RD UK2 Faculty of Science and Information Technology Daffodil International University Dhaka 1207 Bangladesh3 Nuclear and Radiation Chemistry Division Institute of Nuclear Science amp Technology Bangladesh Atomic Energy CommissionDhaka 1000 Bangladesh

4Department of Applied Chemistry and Chemical Engineering University of Dhaka Dhaka 1000 Bangladesh

Correspondence should be addressed to Kazi Md Zakir Hossain hossain015yahoocom

Received 23 March 2013 Accepted 22 April 2013

Academic Editors T R Chantara W S Chow X Colin A V Raghu and J I Velasco

Copyright copy 2013 Kazi Md Zakir Hossain 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

A range of radiation vulcanised natural rubber latex (RVNRL) films were prepared using various concentrations of aqueousextracts of mature Diospyros peregrina fruit which acted as a cross-linking agent The surface of the RVNRL films exhibited anaggregated morphology of the rubber hydrocarbon with increasing roughness due to increasing fruit extract contents in the latexAn improvement in tensile strength tensile modulus and storage modulus of RVNRL films was observed with the addition offruit extracts compared to the control film due to their cross-linking effect The glass transition (119879

119892) temperature of all the RVNRL

films was found to be at around minus615∘C The films were also observed to be thermally stable up to 325∘C while the maximumdecomposition temperature appeared at around 375∘C The incorporation of fruit extracts further revealed a significant influenceon increasing the crystallinity gel content and physical cross-link density of the RVNRL films

1 Introduction

Virgin natural polymers like rubber latex an elastic macro-molecular polymer (polyisoprene) have inherently lowmechanical and thermal stability properties Natural rubberis highly sensitive to thermal decomposition and autooxida-tion and therefore undergoes thermal aging when exposedto heat air and ozone resulting in poor mechanical thermaland swelling properties In order to improve theirmechanicalproperties the rubber molecules are being processed withdifferent types of antioxidants and particulate fillers suchas silica [1 2] clays [3] carbon black [4] and carbonnanotubes [5 6] to expand their applications in variousfields Radiation vulcanisation is also being employed toimprove the mechanical properties of natural rubber [5 78] Some nonwater soluble amino acids such as cystine

asparagines and alanine were also used as antioxidant inradiation vulcanised natural rubber latex (RVNRL) filmsand showed good antiaging effect on RVNRL films withtensile strength retentions ranging from 70 to 80 afteraccelerated aging at 100∘C for 24 h compared to RVNRL filmcontaining no antioxidant (tensile strength retention sim35)[9] They also reported Keratin from chicken feather as apotential antioxidant (tensile strength retention sim60) forRVNRL film Tris(nonylated phenyl)phosphite (TNP) [10ndash12] polyfuran polythiophene [13] polyamines [3 14] andpyridazine derivatives [15] were also reported to be effectiveantioxidants to prolong the life of natural and syntheticrubber films

Kosıkova et al [16] investigated sulphur free lignin (10ndash30 phr) as a natural filler in natural rubber which signif-icantly improved the tensile properties of the films For

2 ISRN Polymer Science

example tensile strength of sim399MPa was reported forthe rubber film containing 10 parts per hundred rubber(phr) lignins compared to the control rubber film with nolignin content (sim187MPa) In another study carbon blackfilled natural rubber containing lignin was suggested tohave positive stabilising effect after thermooxidative agingof rubber films at 80∘C which was comparable to theconventional synthetic antioxidant (N-phenyl-N-isopropyl-p-phenylenediamine (IPPD)) [17] Rodrigues et al [18] inves-tigated the Cashew Nut Shell Liquid (CNSL) as a naturalantioxidant in cis-14-polyisoprene rubber and showed thataddition of 5CNSLhad the highest antioxidant activity overthe thermal oxidation at 140∘C of polyisoprene rubber

The Diospyros peregrina fruit belongs to the Ebenaceaefamily locally called River ebony Gaub andor Indian per-simmon The extremely slimy pulp comes out of the fruit asgum exudates which mainly contained triterpenes alkenesflavonoids and tannins [19ndash22] and had already showedits antioxidant [23] antidiabetic [24 25] antidiarrhoeaand antidysentery properties [26] The aqueous extracts ofDiospyros peregrina fruit have been used in the radiationvulcanised (from 0 to 20 kGy) natural rubber latex films asa natural antioxidant to evaluate the mechanical propertiesafter thermal aging at 100∘C for 24 h [23] Addition of 10 phrnatural antioxidant at 15 kGy absorbed dose was reportedto be optimum for the significant improvement of tensilestrength and tear resistance properties of RVNRL films

Recently improvement of the materials properties ofnatural rubber has also been reported via grafting andorblending with different types of polymers such as styrene-butadiene rubber [27] acrylamide [28] polypropylene [29]and chitosan [30]The aim of the present study was to investi-gate the influence of gummyDiospyros peregrina fruit extractsas a natural cross-linking agent on the mechanical thermo-mechanical thermal crystallization and swelling propertiesof RVNRL films The morphological surface roughness gelcontent and physical cross-link density properties of therubber films with various fruit extract contents were alsoinvestigated

2 Experimental

21 Processing of RVNRL Films The field latex was collectedfrom the Atomic Energy Research Establishment (AERE)rubber garden Savar Bangladesh and immediately pre-servedwith ammonia solution (BDHUK)A laboratory scalecentrifuge machine (SPL-100 Saito Separator Ltd Japan)was employed to concentrate the latex to 60 total solidscontent (TSC) followed by dilution with ammonia solution(15 vv) to 50TSC After that 10 and 15 phr of fruitextracts having pH value around 57 and viscosity 462mPasdots(matured and green Diospyros peregrina fruits were collectedfrom Gazipur Bangladesh) and a five phr n-butyl acrylate(n-BA) (purchased from Kanto Chem Co Inc Japan) asradiation vulcanisation accelerator were added slowly to theNRL and mixed for an hour using a magnetic stirrer Themixture was irradiated by Co-60 gamma source at a dose rateof 313 Kradsdothminus1 and was cast on raised rimmed glass plate

Table 1 Formulations and sample codes for the RVNRL filmsinvestigated in this study

Sample codes used inthis study

Latex(phr)

Fruit extract(phr)

n-BA(phr)

NR 95 0 5NR-10 85 10 5NR-15 80 15 5

moulds to obtain around 070mm thick films with varyingformulations (see Table 1) The RVNRL films were leachedwith distilled water for 24 h at room temperature and air-dried until transparent films were achieved [31]

22 Morphological Characterisation The surface morphol-ogy of the RVNRL films was characterised using an SEM(Philips XL30 FEI) at an accelerating voltage of 10 kV anda working distance of 10mm A sputtered platinum coatingwas used to avoid any charging effect on the film during thecharacterisation

23 Surface Roughness Analysis The surface roughness ofRVNRL films was conducted on a Surftest (SV-600 Mitu-toyo) using a diamond stylus tip (5120583m tip radius 005120583mresolution and 02mm sminus1 travel speed) Data were collectedfrom 48mm measurement distance and from at least tendifferent positions of each film

24 Tensile Test The tensile test (tensile strength modulusat 500 elongation and elongation at break) of RVNRLfilms was conducted using dumbbell-shaped test specimensaccording to ISO 37-1977(E) method [32] on a universaltensile testing machine (Hounsfield-H50KS UK)

25 Dynamic Mechanical Analysis (DMA) DMA were con-ducted using a Q800 from TA Instruments (USA) in mul-tifrequency strain mode to investigate the tensile storagemodulus (1198641015840) and tan delta of RVNRL films with increasingtemperature The specimens were prepared by cutting stripsfrom films with a width of 5mm and length of 25mm andheated from minus70∘C to 60∘C at rate of 10∘Cminminus1 using 15mmgap distance 01 strain 001N preload force 125 forcetrack and 1Hz frequency

26 Differential Scanning Calorimetry (DSC) Analysis Theglass transition temperature (119879119892) of RVNRL films was inves-tigated using a DSC instrument (Q2000 TA instrumentsUK) The samples (sim7mg) were heated from minus85∘C to 50∘Cat a heating rate of 10∘Cminminus1 under nitrogen gas flow(50mLminminus1)

27 Thermogravimetric Analysis (TGA) TG analysis ofRVNRL films was performed on a TA Q500 from 25∘C to600∘C with a heating rate of 10∘Cminminus1 under 60mLminminus1nitrogen gas flow TA Universal analysis 2000 software was

ISRN Polymer Science 3

Table 2 Tensile properties of RVNRL films prepared from irradiated NR latex with varying proportion of fruit extracts

Samples Tensile strength (MPa)(plusmnstandard deviation)

Modulus at 500 elongation (MPa)(plusmnstandard deviation)

Elongation at break ()(plusmnstandard deviation)

NR 2885 plusmn 058 284 plusmn 009 1036 plusmn 9

NR-10 3156 plusmn 050 320 plusmn 004 1000 plusmn 7


(a) (b)

(c)

50 120583m 50 120583m

50 120583m

Figure 1 SEM images of radiation vulcanised natural rubber latex (RVNRL) films (a) NR (b) NR-10 and (c) NR-15

0

02

04

06

08

1

12

minus2 0 2 4 6 8 10 12 14 16

Ra (120583

m)

Fruit extract content (phr)

Figure 2 Relationship between the average surface roughness (Ra)and fruit extract content in RVNRL films

used to calculate the weight loss () and derivative weightloss with temperature from the TG scan

28 X-Ray Diffraction (XRD) Analysis The crystallinity ofthe RVNRL films was observed using a D500 diffractometer(SIEMENS) using a Cu-K120572 radiation source (120582 = 0154) at30 kV and 15mA and the data obtained from 10∘ to 40∘ 2120579using a scan step time of 2 sec and step size of 004∘

29 Swelling Properties The swelling ratio (SR) of the rub-ber films was measured from the 10mm round shape testspecimens (at least five pieces) according to British standard(BS 1673 Part 4 1953) by measuring the mass of the samplebefore and after immersing in toluene (purchased fromMerck Germany) for 72 h until equilibrium swelling at roomtemperature [32]

SR =119882119904 minus119882119889

119882119889

(1)

where119882119889 and119882119904 are the weight of dry and swollen sample intoluene respectively

The swollen samples were then dried in an oven at50∘C for 48 h and then further vacuum dried at the sametemperature for 24 h to remove the residual solvent The gel


minus80 minus50 minus20 10 40 70

Stor

age m

odul

us (P

a)

Temperature (∘C)

NRNR-10NR-15

1119864+8

1119864+7

1119864+6

1119864+5

log119864998400

(a)

minus80 minus50 minus20 10 40 70Temperature (∘C)

NRNR-10NR-15

Tan

delta

3

25

2

15

1

05

0

minus60∘Cminus57∘C

(b)

Figure 3 (a) Storage modulus and (b) tan delta curves of NR NR-10 and NR-15 films obtained from DMA data

minus90 minus70 minus50 minus30 minus10 10 30 50

minus615∘C

minus618∘C

minus622∘C

Exo

up

Temperature (∘C)

NRNR-10NR-15

119879119892

Hea

t flow

(Wg

)

Figure 4 DSC thermogram of radiation vulcanisedNR NR-10 andNR-15 films

content of the specimens was calculated using the followingequation

Gel content =119882119889 minus119882119889119904

119882119889

(2)

where119882119889 and119882119889119904 are the weight of dry RVNRL films beforeand after being swollen in toluene respectively

210 Cross-Link Density Measurement The physical cross-link density (119881119890) of the RVNRL films was calculated usingthe Flory-Rehner equation using the volume fraction (119881119877) of

the swollen rubber network in the solvent at equilibrium stateaccording to following equation [33]

119881119890 =

[ln (1 minus 119881119877) + 119881119877 + 11990911198812

119877]

1198811 (11988113

119877minus 1198811198772)

119881119877 =119882119889120588119889

119882119889120588119889 +119882sol120588sol

(3)

where 1198811 and 1198831 are the molar volume and interactionparameter of solvent (for toluene 1198811 = 875molsdotcmminus3 and1198831=039) [3]119882119889 and120588119889 are theweight and density of dry rubber(for vulcanised rubber 120588119889 = 09203 gsdotcmminus3) [15] and119882sol and120588sol are the weight and density of solvent (for toluene 120588sol =0865 gsdotcmminus3)

3 Results and Discussion

The use of aqueous extract ofDiospyros peregrina as a naturalantioxidant has already made them promising candidateto improve the mechanical properties of natural rubberafter thermal aging because of their excellent antioxidantand gum-like properties Here we investigated whether thisnatural gummy fruit extract can be used to improve thethermomechanical crystallization and swelling properties ofRVNRL films by increasing their cross-link density

31 Morphological and Surface Roughness Properties Thesurface morphology of RVNRL films with varying fruitextract contents was analysed via SEM and is presentedin Figure 1 Images obtained revealed the dispersion ofrubber particulates within the film (Figure 1(a)) Howeverwith the addition of fruit extracts the rubber particulateswere observed to be aggregated as can be seen in Figures


0

20

40

60

80

100

120

0 100 200 300 400 500 600

Resid

ual w

eigh

t (

)

Temperature (∘C)

NRNR-10NR-15

5060708090

100

250 300 350 400

(a)

0

2

4

6

8

10

12

0 100 200 300 400 500 600

Der

ivat

ive w

eigh

t (

∘C)

Temperature (∘C)

NRNR-10NR-15

365∘C

(b)

Figure 5 (a) TG and (b) DTG curves of radiation vulcanised NRNR-10 and NR-15 films

1(b) and 1(c) This was probably due to the presence ofgum-like Diospyros peregrina fruit extracts which coagulatedthe rubber particulates during the blending and radiationvulcanisation processes

The surface roughness profile of the RVNRL films withvarious fruit extract contents was measured and the rela-tionship between the average surface roughness (Ra) andthe fruit extract contents in the RVNRL films is providedin Figure 2 The Ra value was observed increasing with thefruit extract content steadily from sim07 120583m (NR) to sim09 120583m

0

100

200

300

400

500

600

700

800

900

10 15 20 25 30 35 40

Cou

nt p

er se

cond

2120579

NR

NR-10

NR-15

Figure 6 XRD traces of radiation vulcanisedNRNR-10 andNR-15films

91

92

93

94

95

96

97

98

0

2

4

6

8

10

12

14

16

18

minus5 0 5 10 15 20

Gel

cont

ent (

)

Swel

ling

ratio


SRGel content

Figure 7 Swelling ratio and gel content of RVNRL films withvarious fruit extract contents

(NR-15) which is in well agreement with the SEM images andagain the aggregation of rubber particulates within the filmswas suggested

32 Mechanical Properties Tensile properties (tensilestrength modulus at 500 elongation and elongation atbreak) of the RVNRL films with varying fruit extract contentsare tabulated in Table 2 Tensile strength and modulus at500 elongation were found increasing with the addition offruit extracts in the blend For example NR-15 film showedaround 132 and 165 increase in tensile strength andmodulus properties compared to NR film (tensile strengthsim2885MPa and modulus sim284MPa) This was attributedto the influence of fruit extracts on increasing the cross-linkdensity in RVNRL films during the radiation vulcanization[23] which was evaluated and this is discussed later inthis paper However the elongation at break was observeddecreasing with the addition of fruit extract which was


0

1

2

3

4

5

6

7times10minus5

minus5 0 5 10 15 20Fruit extract content (phr)

Cros

s-lin

k de

nsity

(molmiddotgminus1)

Figure 8 Cross-link density of RVNRL films with various fruitextract contents

probably due to the stiffening effect of fruit extract on theirradiated rubber films

33 Thermomechanical Properties Figure 3(a) revealed thetemperature dependency of storagemodulus of RVNRL filmswith different fruit extract contents The storage modulusof the RVNRL films showed an increasing trend with theaddition of fruit extracts in the RVNRL films in the entiretemperature region investigated in this study and this wasagain suggested to be due to the cross-linking effect of thefruit extract on the rubber hydrocarbon [34]

The variation of tan delta curves of NR NR-10 andNR-15films as a function of temperature is presented in Figure 3(b)It is observed from the tan delta curves that with the additionof fruit extracts the tan delta peaks (119879119892 values) of NR-10 andNR-15 films were seen to shift slightly to the left by 3∘C thatis to the lower temperature regions as compared to the tandelta peak of NR (appeared at minus57∘C) The height of the tandelta peaks was also seen to decrease with the addition offruit extracts in the RVNRL films compared to NR film Thiswas probably due to the presence of lower amount of rubberpolymer in the NR-10 and NR-15 that were taking part in thethermal transition

34Thermal Properties From theDSC analysis it can be seenthat the glass transition temperature (119879119892) of NR appearedat around minus615∘C (see Figure 4) which is in well agreementwith the literature values [4 35] and with the addition offruit extracts in the blend 119879119892 values found to shift to thelower temperature region very slightly and this was in wellagreement with the 119879119892 value measured via DMA using tandelta curvesThough a decrease in119879119892 (119875 gt 005) and increasein mechanical and thermomechanical properties (119875 lt 005)apparently showed a discrepancy when fruit extracts wereadded as a cross-linking agent within the natural rubber latexhowever this was presumably due to the plasticizing effect ofthe natural filler used in this study

Thermogravimetry (TG) curves of the radiation vulcan-ised NR NR-10 and NR-15 films are presented in Figure 5(a)The TG analysis revealed that all the RVNRL films werethermally stable up to 325∘C (90 retention of residualweight) indicating that the processing temperature for theseblends should be kept below 325∘C However at highertemperature (around 400∘C) the residual weight of the filmswas found to be decreased with the addition of fruit extractswhich suggested the thermal instability of the additive usedat the higher temperature

The major thermal decomposition profiles of NR NR-10 and NR-15 films were characterised from their derivativethermogravimetry (DTG) curves (presented in Figure 5(b))which showed the maximum decomposition temperature(119879max) for all the RVNRL films at 365∘C The thermaldegradation of all the major functional groups in the RVNRLfilms occurred in the range 300sim425∘C through solid statetransformations and loss of low molecular mass fragments

35 Crystallisation Properties The XRD traces of RVNRLfilms with varying filler contents are depicted in Figure 6The diffraction patterns of all the RVNRL films revealedthe natural rubberrsquos characteristics peaks at around 19∘ twotheta [30] An increase in the intensity of the XRD traceswas observed with the addition of fruit extract which wasattributed to the induced crystallisation of the fruit extractson the rubber polymer

36 Swelling Properties and Cross-Link Density The effecton the swelling ratio (SR) of radiation vulcanised rubberfilms with varying fruit extract contents obtained at 15 kGyabsorbed dose is showed in Figure 7 Swelling ratio decreasedfrom 149 to 70 with the addition of 15 phr fruit extracts tothe blends However the gel content of the RVNRL films wasseen to increase with the fruit extract contents in the RVNRLblends

Thephysical cross-link density of the rubber hydrocarbonin RVNRL films with the addition of fruit extracts is pre-sented in Figure 8The cross-linking densities were observedincreasing significantly to 52 times 10minus5molsdotgminus1 in case of NR-15 film compared to the control NR film (15 times 10minus5molsdotgminus1)This was attributed to the effect of fruit extracts throughthe aggregation of rubber particulates within the vulcanisedrubber films

The RVNRL films produced in this study showed that theincorporation of Diospyros peregrina fruit extracts providesimprovements in mechanical thermomechanical crystalli-sation swelling and cross-linking density properties of theradiation vulcanised rubber films when compared to thecontrol NR film which could minimise the use of syntheticfiller as well as toxic antioxidant in the natural rubber-basedmaterials

4 Conclusion

Aqueous extracts of Diospyros peregrina as natural cross-linking agent were successfully blended with rubber latex invarious contents (0 10 and 15 phr) before being irradiated


at 15 KGy absorbed dose to obtain the RVNRL films Anaggregated morphology of the rubber particulates was seenwith the incorporation of fruit extracts within the RVNRLfilms which played an influential role in imparting somesurface roughness on the films The addition of fruit extractswithin the rubber latex did not exhibit any significantchange in their glass transition and thermal decompositionproperties However an improvement in tensile strengthtensile modulus and storage modulus properties of therubber films demonstrated the cross-linking effect of theDiospyros peregrina fruit extracts in rubber particulates Thepresence of 15 phr fruit extract had a significant effect onincreasing physical cross-linking density of the rubber filmswhich influenced significantly decrease in swelling ratio andincrease in the gel content and crystallisation properties ofthe RVNRL films

Acknowledgments

The authors would like to thank the Atomic Energy ResearchEstablishment (AERE) Savar Bangladesh for providing thenatural rubber latex for this research work

References

[1] N K On A A Rashid M M M Nazlan and H HamdanldquoThermal and mechanical behavior of natural rubber latex-silica aerogel filmrdquo Journal of Applied Polymer Science vol 124no 4 pp 3108ndash3116 2012

[2] S Ostad-Movahed K A Yasin A Ansarifar M Song and SHameed ldquoComparing effects of silanized silica nanofiller on thecrosslinking and mechanical properties of natural rubber andsynthetic polyisoprenerdquo Journal of Applied Polymer Science vol109 no 2 pp 869ndash871 2008

[3] M N Qureshi and H Qammar ldquoMill processing and prop-erties of rubber-clay nanocompositesrdquo Materials Science andEngineering C vol 30 no 4 pp 590ndash596 2010

[4] S S Choi S H Im and C Nah ldquoInfluence of solvent swell andbound rubber on wax solubility of carbon black-reinforced NRcompositerdquo Journal of Applied Polymer Science vol 125 no S1pp E342ndashE347 2012

[5] M A Atieh N Nazir F Yusof et al ldquoRadiation vulcanization ofnatural rubber latex loaded with carbon nanotubesrdquo FullerenesNanotubes and Carbon Nanostructures vol 18 no 1 pp 56ndash712010

[6] S Bhattacharyya C Sinturel O Bahloul M L Saboungi SThomas and J P Salvetat ldquoImproving reinforcement of naturalrubber by networking of activated carbon nanotubesrdquo Carbonvol 46 no 7 pp 1037ndash1045 2008

[7] M E Haque N C Dafader F Akhtar and M U AhmadldquoRadiation dose required for the vulcanization of natural rubberlatexrdquo Radiation Physics and Chemistry vol 48 no 4 pp 505ndash510 1996

[8] YMinoura andMAsao ldquoStudies on the 120574-irradiation of naturalrubber latexrdquo Journal of Applied Polymer Science vol 5 no 14pp 233ndash239 1961

[9] 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

[10] A Thiangchanya K Makuuchi and F Yoshii ldquoDegradabilitytesting of radiation-vulcanized natural rubber latex filmsrdquoJournal of Applied Polymer Science vol 54 no 5 pp 525ndash5311994

[11] F Yoshii S Kulatunge and K Makuuchi ldquoImprovement ofageing properties of rubber films prepared from radiation-vulcanized natural rubber latexrdquo Die Angewandte Makro-molekulare Chemie vol 205 no 1 pp 107ndash115 1993

[12] K Makuuchi F Yoshii M Kokuzawa S Kulatunge and AThiangchanya ldquoAging properties of radiation vulcanized NRlatex filmrdquo Radiation Physics and Chemistry vol 42 no 1-3 pp237ndash240 1993

[13] N A Abdelwahab D E El-Nashar and M A A El-GhaffarldquoPolyfuran polythiophene and their blend as novel antioxidantsfor styrene- butadiene rubber vulcanizatesrdquo Materials andDesign vol 32 no 1 pp 238ndash245 2011

[14] 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

[15] C C Ho and M C Khew ldquoSurface morphology of prevulcan-ized natural rubber latex films by atomic force microscopy newinsight into the prevulcanization mechanismrdquo Langmuir vol15 no 19 pp 6208ndash6219 1999

[16] B Kosıkova A Gregorova A Osvald and J KrajcovicovaldquoRole of lignin filler in stabilization of natural rubber-basedcompositesrdquo Journal of Applied Polymer Science vol 103 no 2pp 1226ndash1231 2007

[17] A Gregorova B Kosıkova and R Moravcık ldquoStabilizationeffect of lignin in natural rubberrdquo Polymer Degradation andStability vol 91 no 2 pp 229ndash233 2006

[18] F H A Rodrigues J P A Feitosa N M P S Ricardo F C FDe Franca and J O B Carioca ldquoAntioxidant activity of CashewNut Shell Liquid (CNSL) derivatives on the thermal oxidation ofsynthetic cis-14-polyisoprenerdquo Journal of the Brazilian Chemi-cal Society vol 17 no 2 pp 265ndash271 2006

[19] J S Chauhan M Saraswat and G Kumari ldquoStructure of a newflavanone glycoside from Doiospyros peregrina rootsrdquo IndianJournal of Chemistry vol 21 pp 169ndash170 1982

[20] R N Chopra and S L Nayar Glossary of Indian MedicinalPlants vol 3 CSIR New Delhi India 1992

[21] N Jain andRYadava ldquoPeregrinol a lupane type triterpene fromthe fruits of Diospyros peregrinardquo Phytochemistry vol 35 no 4pp 1070ndash1072 1994

[22] P SMisraGMisra S KNigam andC RMitra ldquoConstituentsof diospyros peregrina fruit and seedrdquo Phytochemistry vol 10no 4 pp 904ndash905 1971

[23] K M Z Hossain A M S Chowdhury M E Haque N CDafader and F Akhtar ldquoEffect of natural antioxidant (diospyrosperegrina) on the aging properties of radiation vulcanized (120574-radiation) natural rubber latex filmrdquo Polymer-Plastics Technol-ogy and Engineering vol 49 no 2 pp 136ndash140 2010

[24] S Dewanjee A K Das R Sahu and M GangopadhyayldquoAntidiabetic activity of Diospyros peregrina fruit effect onhyperglycemia hyperlipidemia and augmented oxidative stressin experimental type 2 diabetesrdquo Food and Chemical Toxicologyvol 47 no 10 pp 2679ndash2685 2009

[25] S Dewanjee R Sahu V Mandal A Maiti and S C MandalldquoAntidiabetic and antioxidant activity of the methanol extractof Diospyros peregrina fruit on Type i diabetic ratsrdquo Pharma-ceutical Biology vol 47 no 12 pp 1149ndash1153 2009


[26] Encyclopedia of Chemical Technology vol 21 4th edition[27] C V Chaudhari Y K Bhardwaj N D Patil K A Dubey V

Kumar and S Sabharwal ldquoRadiation-induced vulcanisation ofnatural rubber latex in presence of styrene-butadiene rubberlatexrdquo Radiation Physics and Chemistry vol 72 no 5 pp 613ndash618 2005

[28] A M S Chowdhury M A Haque K M Z Hossain M EHaque N C Dafader and F Akhtar ldquoStudy on the properties ofradiation induced acrylamide grafted natural rubber latex filmrdquoJournal of Macromolecular Science A vol 48 no 1 pp 37ndash412011

[29] S Merabet F Riahi and A Douibi ldquoThe physical modificationof a natural rubber-polypropylene thermoplastic elastomerblend by azobisformamide blowing agentrdquo ISRN Polymer Sci-ence vol 2012 Article ID 168798 6 pages 2012

[30] J Johns and V Rao ldquoThermal stability morphology andX-ray diffraction studies of dynamically vulcanized naturalrubberchitosan blendsrdquo Journal of Materials Science vol 44no 15 pp 4087ndash4094 2009

[31] S S Mahfuza M E Haque N C Dafader F Akhtar and MU Ahmad ldquoImprovement of physical properties of radiationvulcanized natural rubber latex filmrdquo Journal ofMacromolecularScience vol 33 no 4 pp 175ndash185 1996

[32] S W Karunaratne ldquoStandardization of radiation vulcanisednatural rubber latexrdquo in Proceedings of the International Sym-posium on Radiation Vulcanization of Natural Rubber LatexJAERI-M 89-228 pp 225ndash233 1990

[33] P J Flory and J Rehner ldquoStatistical mechanics of cross-linkedpolymer networks II SwellingrdquoThe Journal of Chemical Physicsvol 11 no 11 pp 521ndash526 1943

[34] R A Stratton and J D Ferry ldquoDynamic mechanical propertiesof natural rubber vulcanizates cross-linked by various agentsrdquoThe Journal of Physical Chemistry vol 67 no 12 pp 2781ndash27851963

[35] D R Burfield and K L Lim ldquoDifferential scanning calorimetryanalysis of natural rubber and related polyisoprenes Measure-ment of the glass transition temperaturerdquo Macromolecules vol16 no 7 pp 1170ndash1175 1983

Submit your manuscripts athttpwwwhindawicom

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2013

CorrosionInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2013


Polymer ScienceInternational Journal of

ISRN Corrosion



CompositesJournal of

Advances in

Materials Science and EngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2013

International Journal of

BiomaterialsHindawi Publishing Corporationhttpwwwhindawicom Volume 2013

ISRN Ceramics


Hindawi Publishing Corporationhttpwwwhindawicom

Volume 2013

MaterialsJournal of

NanotechnologyHindawi Publishing Corporationhttpwwwhindawicom Volume 2013

Journal of

ISRN Materials Science


Hindawi Publishing Corporation httpwwwhindawicom Volume 2013Hindawi Publishing Corporation httpwwwhindawicom Volume 2013

The Scientific World Journal

ISRN Nanotechnology


NanoparticlesJournal of


Smart Materials Research



MetallurgyJournal of

BioMed Research International


ISRN Polymer Science


Na

nom

ate

ria

ls


Journal ofNanomaterials


example tensile strength of sim399MPa was reported forthe rubber film containing 10 parts per hundred rubber(phr) lignins compared to the control rubber film with nolignin content (sim187MPa) In another study carbon blackfilled natural rubber containing lignin was suggested tohave positive stabilising effect after thermooxidative agingof rubber films at 80∘C which was comparable to theconventional synthetic antioxidant (N-phenyl-N-isopropyl-p-phenylenediamine (IPPD)) [17] Rodrigues et al [18] inves-tigated the Cashew Nut Shell Liquid (CNSL) as a naturalantioxidant in cis-14-polyisoprene rubber and showed thataddition of 5CNSLhad the highest antioxidant activity overthe thermal oxidation at 140∘C of polyisoprene rubber

The Diospyros peregrina fruit belongs to the Ebenaceaefamily locally called River ebony Gaub andor Indian per-simmon The extremely slimy pulp comes out of the fruit asgum exudates which mainly contained triterpenes alkenesflavonoids and tannins [19ndash22] and had already showedits antioxidant [23] antidiabetic [24 25] antidiarrhoeaand antidysentery properties [26] The aqueous extracts ofDiospyros peregrina fruit have been used in the radiationvulcanised (from 0 to 20 kGy) natural rubber latex films asa natural antioxidant to evaluate the mechanical propertiesafter thermal aging at 100∘C for 24 h [23] Addition of 10 phrnatural antioxidant at 15 kGy absorbed dose was reportedto be optimum for the significant improvement of tensilestrength and tear resistance properties of RVNRL films

Recently improvement of the materials properties ofnatural rubber has also been reported via grafting andorblending with different types of polymers such as styrene-butadiene rubber [27] acrylamide [28] polypropylene [29]and chitosan [30]The aim of the present study was to investi-gate the influence of gummyDiospyros peregrina fruit extractsas a natural cross-linking agent on the mechanical thermo-mechanical thermal crystallization and swelling propertiesof RVNRL films The morphological surface roughness gelcontent and physical cross-link density properties of therubber films with various fruit extract contents were alsoinvestigated

2 Experimental

21 Processing of RVNRL Films The field latex was collectedfrom the Atomic Energy Research Establishment (AERE)rubber garden Savar Bangladesh and immediately pre-servedwith ammonia solution (BDHUK)A laboratory scalecentrifuge machine (SPL-100 Saito Separator Ltd Japan)was employed to concentrate the latex to 60 total solidscontent (TSC) followed by dilution with ammonia solution(15 vv) to 50TSC After that 10 and 15 phr of fruitextracts having pH value around 57 and viscosity 462mPasdots(matured and green Diospyros peregrina fruits were collectedfrom Gazipur Bangladesh) and a five phr n-butyl acrylate(n-BA) (purchased from Kanto Chem Co Inc Japan) asradiation vulcanisation accelerator were added slowly to theNRL and mixed for an hour using a magnetic stirrer Themixture was irradiated by Co-60 gamma source at a dose rateof 313 Kradsdothminus1 and was cast on raised rimmed glass plate

Table 1 Formulations and sample codes for the RVNRL filmsinvestigated in this study

Sample codes used inthis study

Latex(phr)

Fruit extract(phr)

n-BA(phr)

NR 95 0 5NR-10 85 10 5NR-15 80 15 5

moulds to obtain around 070mm thick films with varyingformulations (see Table 1) The RVNRL films were leachedwith distilled water for 24 h at room temperature and air-dried until transparent films were achieved [31]

22 Morphological Characterisation The surface morphol-ogy of the RVNRL films was characterised using an SEM(Philips XL30 FEI) at an accelerating voltage of 10 kV anda working distance of 10mm A sputtered platinum coatingwas used to avoid any charging effect on the film during thecharacterisation

23 Surface Roughness Analysis The surface roughness ofRVNRL films was conducted on a Surftest (SV-600 Mitu-toyo) using a diamond stylus tip (5120583m tip radius 005120583mresolution and 02mm sminus1 travel speed) Data were collectedfrom 48mm measurement distance and from at least tendifferent positions of each film

24 Tensile Test The tensile test (tensile strength modulusat 500 elongation and elongation at break) of RVNRLfilms was conducted using dumbbell-shaped test specimensaccording to ISO 37-1977(E) method [32] on a universaltensile testing machine (Hounsfield-H50KS UK)

25 Dynamic Mechanical Analysis (DMA) DMA were con-ducted using a Q800 from TA Instruments (USA) in mul-tifrequency strain mode to investigate the tensile storagemodulus (1198641015840) and tan delta of RVNRL films with increasingtemperature The specimens were prepared by cutting stripsfrom films with a width of 5mm and length of 25mm andheated from minus70∘C to 60∘C at rate of 10∘Cminminus1 using 15mmgap distance 01 strain 001N preload force 125 forcetrack and 1Hz frequency

26 Differential Scanning Calorimetry (DSC) Analysis Theglass transition temperature (119879119892) of RVNRL films was inves-tigated using a DSC instrument (Q2000 TA instrumentsUK) The samples (sim7mg) were heated from minus85∘C to 50∘Cat a heating rate of 10∘Cminminus1 under nitrogen gas flow(50mLminminus1)

27 Thermogravimetric Analysis (TGA) TG analysis ofRVNRL films was performed on a TA Q500 from 25∘C to600∘C with a heating rate of 10∘Cminminus1 under 60mLminminus1nitrogen gas flow TA Universal analysis 2000 software was









(a) (b)

(c)

50 120583m 50 120583m

50 120583m


0

02

04

06

08

1

12

minus2 0 2 4 6 8 10 12 14 16

Ra (120583

m)






SR =119882119904 minus119882119889

119882119889

(1)





Stor

age m

odul

us (P

a)

Temperature (∘C)

NRNR-10NR-15

1119864+8

1119864+7

1119864+6

1119864+5

log119864998400

(a)


NRNR-10NR-15

Tan

delta

3

25

2

15

1

05

0


(b)



minus615∘C

minus618∘C

minus622∘C

Exo

up

Temperature (∘C)

NRNR-10NR-15

119879119892

Hea

t flow

(Wg

)




119882119889

(2)




119881119890 =

[ln (1 minus 119881119877) + 119881119877 + 11990911198812

119877]

1198811 (11988113

119877minus 1198811198772)

119881119877 =119882119889120588119889

119882119889120588119889 +119882sol120588sol

(3)






0

20

40

60

80

100

120

0 100 200 300 400 500 600

Resid

ual w

eigh

t (

)

Temperature (∘C)

NRNR-10NR-15

5060708090

100

250 300 350 400

(a)

0

2

4

6

8

10

12

0 100 200 300 400 500 600

Der

ivat

ive w

eigh

t (

∘C)

Temperature (∘C)

NRNR-10NR-15

365∘C

(b)




0

100

200

300

400

500

600

700

800

900

10 15 20 25 30 35 40

Cou

nt p

er se

cond

2120579

NR

NR-10

NR-15


91

92

93

94

95

96

97

98

0

2

4

6

8

10

12

14

16

18

minus5 0 5 10 15 20

Gel

cont

ent (

)

Swel

ling

ratio


SRGel content





0

1

2

3

4

5

6

7times10minus5


Cros

s-lin

k de

nsity

(molmiddotgminus1)












4 Conclusion




Acknowledgments


References











































ISRN Corrosion




Advances in




ISRN Ceramics



Volume 2013

MaterialsJournal of


Journal of





ISRN Nanotechnology












Na

nom

ate

ria

ls











(a) (b)

(c)

50 120583m 50 120583m

50 120583m


0

02

04

06

08

1

12

minus2 0 2 4 6 8 10 12 14 16

Ra (120583

m)






SR =119882119904 minus119882119889

119882119889

(1)





Stor

age m

odul

us (P

a)

Temperature (∘C)

NRNR-10NR-15

1119864+8

1119864+7

1119864+6

1119864+5

log119864998400

(a)


NRNR-10NR-15

Tan

delta

3

25

2

15

1

05

0


(b)



minus615∘C

minus618∘C

minus622∘C

Exo

up

Temperature (∘C)

NRNR-10NR-15

119879119892

Hea

t flow

(Wg

)




119882119889

(2)




119881119890 =

[ln (1 minus 119881119877) + 119881119877 + 11990911198812

119877]

1198811 (11988113

119877minus 1198811198772)

119881119877 =119882119889120588119889

119882119889120588119889 +119882sol120588sol

(3)






0

20

40

60

80

100

120

0 100 200 300 400 500 600

Resid

ual w

eigh

t (

)

Temperature (∘C)

NRNR-10NR-15

5060708090

100

250 300 350 400

(a)

0

2

4

6

8

10

12

0 100 200 300 400 500 600

Der

ivat

ive w

eigh

t (

∘C)

Temperature (∘C)

NRNR-10NR-15

365∘C

(b)




0

100

200

300

400

500

600

700

800

900

10 15 20 25 30 35 40

Cou

nt p

er se

cond

2120579

NR

NR-10

NR-15


91

92

93

94

95

96

97

98

0

2

4

6

8

10

12

14

16

18

minus5 0 5 10 15 20

Gel

cont

ent (

)

Swel

ling

ratio


SRGel content





0

1

2

3

4

5

6

7times10minus5


Cros

s-lin

k de

nsity

(molmiddotgminus1)












4 Conclusion




Acknowledgments


References











































ISRN Corrosion




Advances in




ISRN Ceramics



Volume 2013

MaterialsJournal of


Journal of





ISRN Nanotechnology












Na

nom

ate

ria

ls





Stor

age m

odul

us (P

a)

Temperature (∘C)

NRNR-10NR-15

1119864+8

1119864+7

1119864+6

1119864+5

log119864998400

(a)


NRNR-10NR-15

Tan

delta

3

25

2

15

1

05

0


(b)



minus615∘C

minus618∘C

minus622∘C

Exo

up

Temperature (∘C)

NRNR-10NR-15

119879119892

Hea

t flow

(Wg

)




119882119889

(2)




119881119890 =

[ln (1 minus 119881119877) + 119881119877 + 11990911198812

119877]

1198811 (11988113

119877minus 1198811198772)

119881119877 =119882119889120588119889

119882119889120588119889 +119882sol120588sol

(3)






0

20

40

60

80

100

120

0 100 200 300 400 500 600

Resid

ual w

eigh

t (

)

Temperature (∘C)

NRNR-10NR-15

5060708090

100

250 300 350 400

(a)

0

2

4

6

8

10

12

0 100 200 300 400 500 600

Der

ivat

ive w

eigh

t (

∘C)

Temperature (∘C)

NRNR-10NR-15

365∘C

(b)




0

100

200

300

400

500

600

700

800

900

10 15 20 25 30 35 40

Cou

nt p

er se

cond

2120579

NR

NR-10

NR-15


91

92

93

94

95

96

97

98

0

2

4

6

8

10

12

14

16

18

minus5 0 5 10 15 20

Gel

cont

ent (

)

Swel

ling

ratio


SRGel content





0

1

2

3

4

5

6

7times10minus5


Cros

s-lin

k de

nsity

(molmiddotgminus1)












4 Conclusion




Acknowledgments


References











































ISRN Corrosion




Advances in




ISRN Ceramics



Volume 2013

MaterialsJournal of


Journal of





ISRN Nanotechnology












Na

nom

ate

ria

ls




0

20

40

60

80

100

120

0 100 200 300 400 500 600

Resid

ual w

eigh

t (

)

Temperature (∘C)

NRNR-10NR-15

5060708090

100

250 300 350 400

(a)

0

2

4

6

8

10

12

0 100 200 300 400 500 600

Der

ivat

ive w

eigh

t (

∘C)

Temperature (∘C)

NRNR-10NR-15

365∘C

(b)




0

100

200

300

400

500

600

700

800

900

10 15 20 25 30 35 40

Cou

nt p

er se

cond

2120579

NR

NR-10

NR-15


91

92

93

94

95

96

97

98

0

2

4

6

8

10

12

14

16

18

minus5 0 5 10 15 20

Gel

cont

ent (

)

Swel

ling

ratio


SRGel content





0

1

2

3

4

5

6

7times10minus5


Cros

s-lin

k de

nsity

(molmiddotgminus1)












4 Conclusion




Acknowledgments


References











































ISRN Corrosion




Advances in




ISRN Ceramics



Volume 2013

MaterialsJournal of


Journal of





ISRN Nanotechnology












Na

nom

ate

ria

ls




0

1

2

3

4

5

6

7times10minus5


Cros

s-lin

k de

nsity

(molmiddotgminus1)












4 Conclusion




Acknowledgments


References











































ISRN Corrosion




Advances in




ISRN Ceramics



Volume 2013

MaterialsJournal of


Journal of





ISRN Nanotechnology












Na

nom

ate

ria

ls





Acknowledgments


References











































ISRN Corrosion




Advances in




ISRN Ceramics



Volume 2013

MaterialsJournal of


Journal of





ISRN Nanotechnology












Na

nom

ate

ria

ls




















ISRN Corrosion




Advances in




ISRN Ceramics



Volume 2013

MaterialsJournal of


Journal of





ISRN Nanotechnology












Na

nom

ate

ria

ls









ISRN Corrosion




Advances in




ISRN Ceramics



Volume 2013

MaterialsJournal of


Journal of





ISRN Nanotechnology












Na

nom

ate

ria

ls



Documents

Physicochemical, Thermomechanical, and Swelling Properties of