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Research ArticleRadiation Crosslinking of PolyurethanesCharacterization by FTIR TGA SEM XRDand Raman Spectroscopy

Mohamed Mohamady Ghobashy1 and Zizi I Abdeen2

1Radiation Research of Polymer Department National Center for Radiation Research and Technology (NCRRT)Atomic Energy Authority PO Box 29 Nasr City Cairo Egypt2Polymers Laboratory Petrochemicals Department Egyptian Petroleum Research Institute (EPRI) PO Box 11727 Cairo Egypt

Correspondence should be addressed to Mohamed Mohamady Ghobashy mohamedghobashyeaeaorgeg

Received 7 June 2016 Revised 17 September 2016 Accepted 5 October 2016

Academic Editor Raghu V Anjanapura

Copyright copy 2016 M M Ghobashy and Z I Abdeen This is an open access article distributed under the Creative CommonsAttribution License which permits unrestricted use distribution and reproduction in any medium provided the original work isproperly cited

Gamma radiation can be used for enhancing the physical properties of polyurethane (PU) Radiation was used to crosslink a pol-yurethane at room temperature four samples of the PU solid film are irradiated at variable four radiation doses 0 50 100 and150 kGy under vacuum conditions Crosslinking radiation is more common than oxidative degradation and crosslinking is believedto be more efficient in the soft segment of PU The structure of the PUs is performed by Fourier transform infrared (FTIR-ATR)Thermogravimetric Analysis (TGA-DTG) and X-ray Diffraction (XRD) which have been used to investigate the effect of gammaradiation on the polyurethane (PU) The results showed that the radiation crosslinking of polyurethanes improved the thermalstability and the crystallinityThemicrostructure modifications of polyurethane samples have also been studied as a function of thedose using the scanning electron microscope (SEM) The effects of gamma irradiation on the color changes of polyurethane wereobserved The irradiated PUs have conjugated structure and are capable of emitting purple fluorescence

1 Introduction

Polyurethanes are produced by reacting an isocyanate(N=C=O)n with a polyol containing on average two or morehydroxyl groups per molecule (OH)n The aromatic iso-cyanates diphenylmethane diisocyanate (MDI) or toluenediisocyanate (TDI) are more reactive than aliphatic isocya-nates such as hexamethylene diisocyanate (HDI) or isopho-rone diisocyanate (IPDI) An important exception to this isdiphenylmethane diisocyanate [1]

Polyurethane elastomers are an important type of pol-ymer material with excellent physical and chemical prop-erties And many applications have been found in differentfields There are further studies about polyurethane elastom-ers with graded structure Raghu and coworkers [2ndash6]reported the synthesis and characterization of novel linearsegmented polyurethanes (PUs) containing Schiff base

chalcone and azo-based diols like 441015840-(ethane-12-diylid-enedinitrilo)diphenol 441015840-(pentane-15-diylidenedinitri-lo)diphenol 221015840-[14-phenylenebis(nitrilomethylylidene)]di-phenol 221015840-[441015840-methylene-di-2-methylphenylene-111015840-bis(nitrilomethylylidene)]diphenol 4-[[(4-hydroxyphen-yl)imino]methyl]phenol 26-bis(4-hydroxybenzylidene)-cyclohexanone 441015840-[14-phenylenedi-diazene-21-diyl]bis(2-carboxyphenol) and 441015840-[henylenedi-diazene-21-diyl]bis(2-chlorophenol) with various diisocyanates [2 3 7ndash9] Andthey successes to introduce a dihydrazide diol moiety inthe main chain like N

1N2-bis[(4-hydroxyphenyl)meth-

ylene]ethanedihydrazide (BHPMED) with 441015840-diphenyl-methane diisocyanate (MDI) tolylene 24-diisocyanate(TDI) isophorone diisocyanate (IPDI) and hexamethylenediisocyanate (HDI) [3] Jeong et al 2003 [4] prepared nano-composite of waterborne polyurethane (WPU) based onpoly(hexamethylene carbonate) diol reinforced by

Hindawi Publishing CorporationJournal of PolymersVolume 2016 Article ID 9802514 9 pageshttpdxdoiorg10115520169802514

2 Journal of Polymers

organophilic clay They observed the water swell wasdecreased and thermal resistance was increased as thecontent of clay was increased Reinforcement of polyurethaneby composite with inorganic materials has attracted con-siderable attention in various literature because they exhibitthe enhanced performance properties compared withconventional composites Choi et al 2012 [5] preparednanocomposites of waterborne polyurethane (WPU) rein-forced with functionalized graphene sheets (FGSs) Reddyand coworkers prepared a series of novel segmented poly-urethanes (PUs) containing imine units by polyadditionreaction of various diisocyanates like 441015840-diphenyl-meth-ane diisocyanate (MDI) toluene 24-diisocyanate (TDI)isophorone diisocyanate (IDI) and hexamethylene diiso-cyanate (HDI) with 441015840-[14-phenylenebis(methylyliden-enitrilo)]diphenol based diol [6] with 441015840-pyridine-26-di-ylbis[nitrilomethylylidene]diphenol-based diol [10]

Radiation crosslinking polymerization is one of theimportant research fields of radiation polymerization [11]radiation crosslinking modification of polyurethanes is oneof most important aspects [12] In the study of the radia-tion crosslinking polyurethane a lot of work was done inpolyurethane synthesis in its molecular backbone to importsome unsaturated bond and application of 120574-irradiation torealize the radiation crosslinking in order to obtain a bettercrosslinking effects improved thermal stability and otherproperties of polyurethane In another study on the influenceof electron-beam irradiation in air on the chemical andthe structural properties of medical-grade polyurethane theresults showhomogeneous oxidative degradation followed bya decrease in molecular mass and an increase in polydisper-sity [13] The chain scission is common by the irradiationUV and gamma irradiation in air of polyurethane [14] Inthis paper we irradiated polyurethane film in isolated ofair under vacuum conditions Segmented (soft and hard)polyurethanes (PUs) are a class of thermoplastic elastomersthat bridge the gap between rubbers and plastics and could beinfluenced by irradiation [15]The superior properties of PUsoriginate in the thermodynamic incompatibility between thehard segments (HSs) and soft segments (SSs) When PUsare exposed to high energy irradiation the structure andmechanical property may be altered It is of importance fromboth basic and applied viewpoints to determine how themicrostructure and stability could be influenced by irradia-tion Generally PUs have shown higher radiation resistancecompared with other common polymers such as poly-olefins and vinyl polymers [16] However the effects ofirradiation on the microstructure are complex and closelyrelated to the chemical composition irradiation environ-ment and absorbed dose [17]

In this paper radiation was used in crosslinking ofpolyurethane at room temperature under vacuum of air Theradiation crosslinking affects the characterization of polyure-thane like morphology of microstructure as detected by SEMand thermal stability enhancing with irradiation dose besidethe crystanility as observed from TGA and XRD data Theirradiated PU emits purple fluorescence light when exposedto UV lamp (362 nm)

2 Materials and Method

A commercial 441015840-diphenylmethane diisocyanate (MDI)from the market and polyether were obtained from commer-cial suppliers The MDI and polyether were used as receivedToluene was obtained from Sigma-Aldrich Chemical Co

21 Preparation of Polyurethane Thesynthesis procedurewascarried out on the basis of prepolymer method A weighedquantity of dried 1029 g of polyether polyol was mixed wellwith 150mL toluene and charged into a four-necked flaskand equippedwith stirrer thermometer dropping funnel gasinlet and air condenser with a drying tube During flushingwith a slow stream of nitrogen the mixture was heated attemperature of 55 plusmn 5∘C and stirred Then 40mL of 44-diphenylmethane diisocyanate (MDI) was dropped into themixture gradually over a period of 30min With continuousstirring at the end of the reaction (after 6ndash8 h) the finalproduct was a clear yellowish viscous liquid Isocyanate ter-minated polyurethane prepolymer was formed after castingstep

22 Polyurethane Film Preparation For the preparation ofthe polyurethane film the liquid purified prepolymer wascast onto the surface of a glass plate and then left to becured under ambient conditions A combination of abovereactions occurred due to the simultaneous presence of polyolin the reaction system Finally prepolymer chains completelyreact with an equivalent amount of water leading to theformation of crosslinked polyurethaneThen filmswere driedat variable temperatures ranging from 30∘C to 40∘C for 24 hto ensure slow drying in order to completely remove thesolvent Subsequently the films were removed from the moldand stored in a desiccator at room temperature for furthercharacterization

23 Irradiation Conditions Irradiate the samples at doses of0 50 100 and 150 kGy with the 60 Co Indian irradiationfacility gamma rays at a dose rate 205 KGyh All sampleswere irradiated at room temperature in the absent of air Theirradiation facility was constructed by the National Centerfor Radiation Research and Technology (NCRRT) AtomicEnergy Authority of Egypt (AEAE) Cairo

3 Characterizations of the Samples

31 (ATRFTIR)Raman Spectroscopy The probability ofprepolymerization method with isocyanatepolyol group([N=C=OsimOndashH]) was measured using attenuated totalreflectance-Fourier transform infrared ATR-FTIR spec-troscopy Vertex 70 FTIR spectrometer equipped with HYPE-RION series microscope Bruker Optik GmbH EttlingenGermany over the 4000ndash400 cmminus1 range at a resolution of4 cmminus1 Software OPUS 60 (BRUKER) was used for dataprocessing which was baseline corrected by the rubber bandmethod with CO

2bands excludedThe Ramanmeasurement

was carried out with dispersive Raman spectroscopy at laser785 nm and laser power 010MW Senterra Bruker OpticsGermany

Journal of Polymers 3

32 XRD The effects of gamma radiation at the crystallinityof polyurethane samples were measured using X-ray diffrac-tion patterns which were obtained using XRD-6000 seriesPolymer blend samples were analysed via overlaid X-raydiffraction patterns by Shimadzu apparatus using nickel-filter Cu-K target voltage = 40 (kV) current = 30 (mA) andscan speed = 8 (degmin) (Shimadzu Scientific Instruments(SSI) Kyoto Japan)

33 SEM The surface morphology and the formation ofcrystalline regions of irradiated polyurethane films were per-formed using scanning electron microscopy (SEM) withthe working operation at 20 kV (JEOL JSM-5400 Jeol LtdTokyo Japan) All samples coated with a thin layer of goldImages of these samples were taken using optical microscopewith 200x magnifications

34 TGADTG Thermal analysis was performed using TGAfrom (TA Instruments New Castle DE USA) The TGAfeatures a top-loading balance Furnaces provide the highestavailable cooling speed and conversely they are heated up to500∘C with heating rate 10∘Cmin

4 Results and Discussion

41 FTIR and Raman Spectroscopy of Irradiated PolyurethaneThe polyurethane (PU) was synthesized by prepolymeriza-tion method with isocyanatepolyol group ([NCOOH]) inambient temperature and exposed the obtained solid film togamma irradiation at various doses from 0 up to 150 kGyThepresence of the urethane bond was observed in all the FTIRspectra (Figure 1(a)ndash(d)) of the irradiated and unirradiatedPUThe carbonyl peakwas identified at 1718 cmminus1 in all curves(a) to (d) while the disappearance of isocyanate peak (ndashNCO)was observed around 2270 cmminus1 and hydroxyl (no peak at3456 cmminus1) indicating a complete usage of all isocyanatespresent in the prepolymer reactants [18 19] and the excessof OH favors crosslinking yielding of the rigid PU [20] TheFTIR spectroscopy analysis justified that the diisocyanate wasthe main contributor in the formation of the hard segment ofthe PUThe two bands observed between 2930 and 2840 cmminus1were attributed to symmetric andnonsymmetric stretching ofthe CndashH bond [21] When the gamma irradiation increasedthe formation of hard segment of PU will be affected andshow nonhydrogen bonding in structures of unirradiatedand irradiated PU due to disappearing peaks between 1643and 1675 cmminus1 because of the presence of hydrogen bondedC=O group [22 23]The imine bands (CH=N) have appearedat 1601 cmminus1 [24] Hence irradiated PU may have strongerbonds due to gamma doses than bonds of unirradiated PUsample

Raman spectroscopy which is a complementary tech-nique to infrared spectroscopy also measures the vibrationalenergy levels In Figures 2(a)ndash2(d) are the asymmetric andsymmetric stretching vibrations of irradiated and unirradi-ated PU Both the isocyanate asymmetric stretch at 2275 cmminus1and symmetric stretch at 1445 cmminus1 disappeared with poly-merization process taking place The ether link (CndashOndashC)was found at 1182 cmminus1 which is composed of a large set

1601(CH=N)

3590(N-H)

1718(C=O)

Tran

smitt

ance

()

3500 3000 2500 2000 1500 1000 5004000Wave number (cmminus1)

(a)

(c)

(d)

(b)

Figure 1 FTIR-ATR chart for irradiated PU with (a) 0 kGy (b)50 kGy (c) 100 kGy and (d) 150 kGy

of polyol within the isocyanate The aromatic ring showedchemical bands characteristic of the molecular structure ofpolyurethanes such as the Raman bands corresponding tothe urethane (NndashH) amid II group (1532 cmminus1) and to phenolgroup (1613 cmminus1) These bands were the result of aromaticring breathingstretching vibrational modes present in thephenylene groups of MDI [25] Additionally peaks at 678746 and 880 cmminus1 characteristic of CndashC bonds were foundin an aromatic conformation [26]

42 Effect of Irradiation Doses on the Crystallinity of Cross-linked Polyurethane We are using X-ray diffraction to inves-tigate the effect of gamma irradiations on the structure ofpolyurethane elastomers [27] concentrating on the hardsegments in diphenylmethane diisocyanate (MDI) and softsegment as polyether Polyurethane block copolymers derivetheir elastomeric properties from phase separation into hard(polyurethane) and soft (polyether) domains

X-ray diffracts for irradiated samples and the originalunirradiated (PU) were shown in Figure 3 The curves forirradiated samples were translated for higher intensity valuesThe increase of crystallinity of the PU samples is evidencedmainly by the appearance of the two characteristic peakslocated at 2120579 = 19∘ and 23∘

The intensity of this peak increased with radiation dosesbeing increased Also X-ray diffraction curves indicate adecrease in d-spacing (A) corresponding to a lower distancebetween aromatic rings from MDI [14] where for PU(0 kGy) the 2120579 = 1905∘ (4653 A) and 2328∘ (3817 A) forPU (50 kGy) 2120579 = 1925∘ (4606 A) and 2328∘ (3790 A) forPU (100 kGy) 2120579 = 1927∘ (4600 A) and 2328∘ (3793 A) andfor PU (150 kGy) 2120579 = 1942∘ (4565 A) and 2358∘ (3769 A)According to Trovati et al [28] and Yang [29] the peak at 19∘corresponds to regular interplanar spacing corresponding toaromatic rings from hard segment of MDI A right shift inthe position of the peak at 19∘ indicates a decrease in the chainspacingThese effects indicate an increase in the crosslink thatpromotes decrease in d-spacing (A) and right shift of the peakat 19∘ These results showed that the degree of crystallinity


0200400600800

1000120014001600

2886

77

1718

31

1613

56

1532

1182

53

880

50 746

3267

812

Ram

an in

tens

ity

5002500 2000 1500 100030003500Wave number (cmminus1)

(a)

2886

66

1718

32

1613

42

1532

11

1182

42

880

1574

632

678

33

3000 2500 2000 1500 1000 5003500Wave number (cmminus1)

0

500

1000

1500

2000

2500

Ram

an in

tens

ity

(b)

2886

45

1718

25

1613

07

1532

01 11

825

7

880

1274

612

678

04

0

500

1000

1500

2000

Ram

an in

tens

ity


(c)

2887

69

1613

46

1532

25 11

820

1

880

12 746

2167

822


0

500

1000

1500

2000

2500

Ram

an in

tens

ity

(d)

Figure 2 Raman spectroscopy for irradiated PU with (a) 0 kGy (b) 50 kGy (c) 100 kGy and (d) 150 kGy

10 20 30 40 50 60 70 80

2120579

150KGy100KGy

50KGy0KGy

Figure 3 X-ray diffraction of irradiated polyurethane

is controlled by the gamma irradiation doses The change ofcrystallinity can be explained by the degree of crosslinking ofthe PU samples

(a)(b)

(c)(d)

11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29102120579

Figure 4 X-ray diffraction of irradiated polyurethane (a) 0 kGy (b)50 kGy (c) 100 kGy and (d) 150 kGy

As mentioned highly ordered crystalline structuredepends on the absorbed gamma radiation by the poly-urethane backbone The X-ray diffraction in Figures 4(a)ndash4(d) showed that the increase in gamma irradiation dosesresults in increase in the intensity of the peak attributed tosoft segment localized at 2120579 = 2135∘ and this confirms thatsoft segment tends to crystallize generating better definedpeak not observed for unirradiated PU [30 31]This indicatesthat the crystallinity of PU elastomers is provided by thesoft segments As shown in Figure 4 the intensity of peak at2120579 = 2135∘ increased with irradiation doses being increasedwhich relates to a certain degree of structural ordering uponirradiationTherefore the XRD results imply that the orderedof soft segment is increased induced by crosslinking [17]And the part of the PUs structure due to the hard segmentswould be less crystalline than the soft segments which areable to crosslink by gamma radiation and give a structure as


crystalline as possible These results confirm the hypothesisthat the radiation crosslink of polyurethane increases in thesoft segment rather than hard segment This increase in theorientation degree and higher intensity of crystallinity inthe irradiated PU is due to radiation crosslinked processHence crosslinking like hydrogen bonding still influenced thecrystallization process of the PU samples [32]

Corresponding to Figures 4(b)ndash4(d) there are sevendiffraction peaks within 2120579 = 137∘ 148∘ 1529∘ 224∘ 263∘271∘ and 281∘ which are observed for all the irradiatedPU samples The only observed five diffraction peaks in theunirradiated PU samples as shown in Figure 4(a) localizedwith low intensity at 2120579 = 148∘ 224∘ 263∘ 271∘ and 281∘This indicates that the crosslinked bonds induced by gammairradiations did not lie in one plane

43 Effect of Irradiation Doses on the Morphological Micro-structure of Crosslinked Polyurethane The morphologicalmicrostructure of the irradiated and unirradiated PU ischaracterized with SEM image The level of crosslinking andcrystallinity of unirradiated and irradiated PU surfaces areshown in Figures 5(a)ndash5(d) SEM image shows crystallineinclusions obtained after gamma irradiation at doses 50 100and 150 kGy All the irradiated samples show crystallinityregions rather than amorphous regions by lines formationin the union direction The surface shows some roughnessregion as shown in Figure 5(a) while it involves the effect ofgamma radiationThe crystalline region becomes predomainas shown in Figures 5(b)ndash5(d) The cross-section SEM imagein Figures 5(a1015840)ndash5(d1015840) shows the increase of radiation doseleading to an increase in the crosslinking induced by gammaradiation

Solid PU films under irradiation with a general visibleand UV lamp (120582 = 365 nm) of the polyurethane before andafter (Figure 6 curve I(a)ndash(d)) gamma irradiation treatmentindicate that the polyurethane acquires color change undergamma irradiation The polyurethane was only turned toyellow after being irradiated in absence of oxygen undervacuum conditions while those exposed to UV radiation(365 nm) exhibited strong UV absorption and gave purplecolor that increased with gamma radiation doses increasedfrom 0 up to 150 kGy (Figure 6 curve II(a1015840)ndash(d1015840)) illustratingthe purple color of solid PU films It can be explained bythe 120587-120587lowast transitions resulting from charge transfer betweennitrogen atoms from PU units and the bisphenol rings withthe electron-donating of methyl (ndashCH

3) substituent in the

bisphenol of PU [33] This indicated that the irradiatedPUs have conjugated structure and are capable of emittingfluorescence light

The light photomicrographs (mag 200x) of the poly-urethane before and after (Figure 6 curve III(a10158401015840)ndash(d10158401015840))gamma irradiation treatment indicate that the polyurethaneacquires color changes under gamma where it turns to yellowafter irradiated in absence of oxygen under vacuumWhile ifthe color of PU turned dark brown it is a probable oxidationof the amine and this indicates the degradation of PU inpresence of oxygen [34 35]The difference in color combinedwith change in the degree of crosslinking and crystallinitywas

observedThis indicated significantly the influence of gammairradiation

44 Effect of Irradiation Doses on the Thermal Stability ofCrosslinked Polyurethane All samples of irradiated and unir-radiated polyurethane thermally coincide until temperature298∘C where TGA data indicate that the MDI-based PUsexhibited better thermal stability and this is attributed to thepresence of biphenyl groups on the main chains [36] Somedifference was observed between 333 and 480∘C as shown inFigure 7 where the thermal stability of radiation crosslinkingpolyurethane is greatly improved The temperatures of 20weight loss for polyurethane irradiated by 50 100 and150 kGy are 39320∘C 3846∘C and 3795∘C respectivelybut the temperature of 20 weight loss of unirradiatedpolyurethane is only 37613∘C This indicated that at 50 kGythe polyurethane is highly thermally stability than the otherdoses Also from TGA curves as shown in Figure 7 only onestep of the thermal decomposition was observed for the PUsamples in the unirradiated PU sample (0 kGy) the weightloss 9478 occurs between 38264 and 42106∘C For theirradiated PU samples which were irradiated with gammaradiation doses 50 100and 150 kGy the weight loss was 90369198 and 9166 respectively This indicated the effect ofradiation on crosslinking of polyurethane The amount ofcarbonized residue (char yield) of these PUs in nitrogenatmosphere was more than 5 at 500∘CThe char yield of PU(0 kGy) is higher than irradiated PU as seen in Figure 7 Thismeans that the radiation crosslinking increases the thermalstability of PU

According to the DTG curve (Figure 8) two steps of thethermal decomposition were observed for the unirradiatedand irradiated PU samples in the first step the thermaldecomposition was at 29932 31125 31425 and 31835∘Cfor 0 50 100 and 150 kGy and this could be attributed tothe decomposition of PU soft segment This indicated thatgamma irradiation crosslinking clearly dominated in the softsegment in overall doses where the crosslinking is believedto be most efficient in the soft phase [37] The secondthermal decomposition step 119879max was at 40807 4146941199 and 40704∘C for 0 50 100 and 150 kGy respec-tively From the previous TGADTG curves the thermalstability of radiation crosslinking polyurethane is improvedgradually and to achieve the best when the radiation dosewas between 50 kGy and 100 kGy this can be attributed tothe degree of crosslinking increased with the increase ofradiation dose However when irradiation dose was 150 kGyits thermal stability is worse than 50 kGy Maybe if theirradiation dose was too high the degradation reactiontakes place leading to the degree of crosslinking dropThe radiation crosslinking of polyurethane is preferred atradiation dose between 50 kGy and 100 kGy as it has the bestdegree of crosslinking and thus has the best heat resistance[38]

5 Conclusion

The FTIR results proved the prepolymerization of PU hap-pened The polymerization of urethane bond was proved by


(a)

(c)

(d)

(a998400)

(b998400)

(c998400)

(d998400)

(b)

Figure 5 SEM of solid PU films after and before irradiated in absence of air surfaces and cross-section of (a a1015840) 0 kGy (b b1015840) 50 kGy (c c1015840)100 kGy and (d d1015840) 150 kGy

the disappearance of the peak of isocyanate group around2270ndash2250 cmminus1 FTIR results proved that all isocyanatespresent in the prepolymer reactants and excess of OH formthe rigid PU Raman spectroscopy showed chemical bandscharacteristic of the molecular structure of polyurethanessuch as the urethane (NndashH) amid II group (1532 cmminus1)and phenol group (1613 cmminus1) X-ray diffraction patterns

showed that the degree of crystallinity is controlled by thegamma irradiation doses The change of crystallinity can beexplained by the degree of crosslinking of the PU samplesbased on radiation crosslinking of soft segments rather thanhard segment The polyurethane turned yellow after beingirradiated in absence of oxygen under vacuum conditionsWhen unirradiated and irradiated PU samples are exposed to


(a) (b) (c) (d)

(I)

(II)

(III)

(a998400998400)

(c998400998400) (d998400998400)

(b998400998400)

(a998400) (b998400) (c998400) (d998400)

Figure 6 The photo of PU sample was observed for irradiated polyurethane (a) 0 kGy (b) 50 kGy (c) 100 kGy and (d) 150 kGy (I) undervisible light (II) under UV irradiation at 365 nm (III) Light photomicrographs (mag 200x) of the irradiated polyurethane (a10158401015840) 0 kGy (b10158401015840)50 kGy (c10158401015840) 100 kGy and (d10158401015840) 150 kGy

UV light (362 nm) it was found that the PUs emitted purplecolor where the intensity of color is increased for irradiatedPU samples depending on the gamma radiation doses Thisindicated that the irradiated PUs have conjugated structureand are capable of emitting fluorescence light According tothe DTG curve the gamma irradiation crosslinking clearlydominated in the soft segment in overall doses TGA curves

showed that the thermal stability is worse than 50 kGyMaybe if the irradiation dose was too high the degradationreaction takes place leading to the degree of crosslinkingdrop The radiation crosslinking of polyurethane is preferredat radiation dose between 50 kGy and 100 kGy as it hasthe best degree of crosslinking and thus has the best heatresistance


150KGy0KGy

100KGy50KGy20

40

60

80

100

Wei

ght l

oss (

)

100 150 200 250 300 350 400 450 50050Temperature (∘C)

Figure 7 TGA curve of the irradiated polyurethane

150KGy

0KGy

Der

iv w

eigh

t (

∘C) 100KGy

50KGy

100 150 200 250 300 350 400 450 50050Temperature (∘C)

Figure 8 DTG curves for irradiated polyurethane

Competing Interests

The authors declare that they have no competing interests

References

[1] Z S Petrovic ldquoPolyurethanes from vegetable oilsrdquo PolymerReviews vol 48 no 1 pp 109ndash155 2008

[2] A V Raghu G S Gadaginamath N T Mathew S B Halligudiand TM Aminabhavi ldquoSynthesis and characterization of novelpolyurethanes based on 441015840-[14-phenylenedi-diazene-21-diyl]bis(2-carboxyphenol) and 441015840-[14-phenylenedi-diazene-21-diyl]bis(2-chlorophenol) hard segmentsrdquo Reactive andFunctional Polymers vol 67 no 6 pp 503ndash514 2007

[3] A V Raghu and H M Jeong ldquoSynthesis characterization ofnovel dihydrazide containing polyurethanes based on N1N2-bis[(4-hydroxyphenyl)methylene] ethanedihydrazide and var-ious diisocyanatesrdquo Journal of Applied Polymer Science vol 107no 5 pp 3401ndash3407 2008

[4] H M Jeong K H Jang and K Cho ldquoProperties of waterbornepolyurethanes based on polycarbonate diol reinforced withorganophilic clayrdquo Journal of Macromolecular Science-Physics Bvol 42 no 6 pp 1249ndash1263 2003

[5] S H Choi D H Kim A V Raghu et al ldquoProperties ofgraphenewaterborne polyurethane nanocomposites cast fromcolloidal dispersion mixturesrdquo Journal of Macromolecular Sci-ence Part B Physics vol 51 no 1 pp 197ndash207 2012

[6] K R Reddy A V Raghu and H M Jeong ldquoSynthesis andcharacterization of novel polyurethanes based on 44rsquo-14-phenylenebis[methylylidenenitrilo]diphenolrdquoPolymer Bulletinvol 60 no 5 pp 609ndash616 2008

[7] A V Raghu G S Gadaginamath S S Jawalkar S B Hal-ligudi and T M Aminabhavi ldquoSynthesis characterizationand molecular modeling studies of novel polyurethanes basedon 221015840-[ethane-12-diylbis(nitrilomethylylidene)]diphenol and221015840-[hexane-16-diylbis(nitrilomethylylidene)] diphenol hardsegmentsrdquo Journal of Polymer Science Part A Polymer Chem-istry vol 44 no 20 pp 6032ndash6046 2006

[8] A V Raghu G S Gadaginamath N Mathew S BHalligudi and T M Aminabhavi ldquoSynthesis characterizationand acoustic properties of new soluble polyurethanes based on221015840-[14-phenylenebis(nitrilomethylylidene)diphenol and 221015840-[441015840-methylene-di-2-methylphenylene-111015840-bis(nitrilomethy-lylidene)]diphenolrdquo Journal of Applied Polymer Science vol106 no 1 pp 299ndash308 2007

[9] A V Raghu G Anita Y M Barigaddi G S Gadaginamathand TM Aminabhavi ldquoSynthesis and characterization of novelpolyurethanes based on 26-bis(4-hydroxybenzylidene) cyclo-hexanone hard segmentsrdquo Journal of Applied Polymer Sciencevol 104 no 1 pp 81ndash88 2007

[10] K R Reddy A V Raghu HM Jeong and Siddaramaiah ldquoSyn-thesis and characterization of pyridine-based polyurethanesrdquoDesigned Monomers and Polymers vol 12 no 2 pp 109ndash1182009

[11] K R Reddy K-P Lee A I Gopalan M S Kim A MShowkat and Y C Nho ldquoSynthesis of metal (Fe or Pd)Alloy(Fe-Pd)-nanoparticles-embedded multiwall carbon nanotubesulfonated polyaniline composites by 120574 irradiationrdquo Journal ofPolymer Science Part A Polymer Chemistry vol 44 no 10 pp3355ndash3364 2006

[12] E C Azevedo G O Chierice S C Neto D S Soboll E MNascimento and C M Lepienski ldquoGamma radiation effectson mechanical properties and morphology of a polyurethanederivate from castor oilrdquo Radiation Effects and Defects in Solidsvol 166 no 3 pp 208ndash214 2011

[13] S Shin and S Lee ldquoThe influence of electron-beam irradiationon the chemical and the structural properties of medical-gradepolyurethanerdquo Journal of the Korean Physical Society vol 67 no1 pp 71ndash75 2015

[14] E C Azevedo EMNascimento GO Chierice S C Neto andC M Lepienski ldquoUV and gamma irradiation effects on surfaceproperties of polyurethane derivate from castor oilrdquo Polimerosvol 23 no 3 pp 305ndash311 2013

[15] C Prisacariu Polyurethane Elastomers From Morphology toMechanical Aspects Springer Vienna Austria 2011

[16] E Adem E Angulo-Cervera A Gonzalez-Jimenez J LValentın and A Marcos-Fernandez ldquoEffect of dose and tem-perature on the physical properties of an aliphatic thermoplasticpolyurethane irradiated with an electron beamrdquo RadiationPhysics and Chemistry vol 112 pp 61ndash70 2015

[17] Q Tian E Takacs I Krakovsky Z E Horvath L Rosta and LAlmasy ldquoStudy on themicrostructure of polyester polyurethaneirradiated in air andwaterrdquo Polymers vol 7 no 9 pp 1755ndash17662015


[18] O I H Dimitry Z I Abdeen E A Ismail and A L GSaad ldquoPreparation and properties of elastomeric polyurethaneorganically modified montmorillonite nanocompositesrdquo Jour-nal of Polymer Research vol 17 no 6 pp 801ndash813 2010

[19] K B H Badri W C Sien M S B Raja Shahrom L C Hao NY Baderuliksan andN R Norzali ldquoFTIR spectroscopy analysisof the prepolymerization of palm-based polyurethanerdquo Journalof Solid State Science and Technology vol 18 no 2 pp 1ndash8 2010

[20] D P Suhas H M Jeong T M Aminabhavi and A V RaghuldquoPreparation and characterization of novel polyurethanes con-taining 441015840-oxy-14-diphenyl bis(nitromethylidine)diphenolschiff base diolrdquo Polymer Engineering amp Science vol 54 no 1pp 24ndash32 2014

[21] O I H Dimitry Z Abdeen E A Ismail and A L G SaadldquoStudies of particle dispersion in elastomeric polyurethaneorganically modified montmorillonite nanocompositesrdquo Inter-national Journal of Green Nanotechnology vol 3 no 3 pp 197ndash212 2011

[22] G A Jeffrey and W Saenger Hydrogen Bonding in BiologicalStructures Springer Science amp Business Media Berlin Ger-many 1991

[23] D J Lyman ldquoPolyurethanes I The solution polymerization ofdiisocyanates with ethylene glycolrdquo Journal of Polymer Sciencevol 45 no 145 pp 49ndash59 1960

[24] K R Reddy A V Raghu andHM Jeong ldquoSynthesis and char-acterization of novel polyurethanes based on 441015840-14-phenyl-enebis[methylylidenenitrilo]diphenolrdquo Polymer Bulletin vol60 no 5 pp 609ndash616 2008

[25] S Parnell K Min and M Cakmak ldquoKinetic studies of poly-urethane polymerization with Raman spectroscopyrdquo Polymervol 44 no 18 pp 5137ndash5144 2003

[26] M Cregut M Bedas A Assaf M-J Durand-Thouand and GThouand ldquoApplying Raman spectroscopy to the assessment ofthe biodegradation of industrial polyurethanes wastesrdquo Envi-ronmental Science and Pollution Research vol 21 no 16 pp9538ndash9544 2014

[27] M M Ghobashy and Z I Abdeen ldquoInfluence of gammairradiation on the change of the characterization of elastomericpolyurethanerdquoAdvanced Science Engineering andMedicine vol8 no 9 pp 736ndash739 2016

[28] G Trovati E A Sanches S C Neto Y P Mascarenhas and GO Chierice ldquoCharacterization of polyurethane resins by FTIRTGA and XRDrdquo Journal of Applied Polymer Science vol 115 no1 pp 263ndash268 2010

[29] JH Yang B CChunY-CChung and JHCho ldquoComparisonof thermalmechanical properties and shape memory effect ofpolyurethane block-copolymers with planar or bent shape ofhard segmentrdquo Polymer vol 44 no 11 pp 3251ndash3258 2003

[30] K M Zia I A Bhatti M Barikani M Zuber and H N BhattildquoXRD studies of polyurethane elastomers based on chitin1 4-butane diol blendsrdquo Carbohydrate Polymers vol 76 no 2 pp183ndash187 2009

[31] V Kovacevic L J Kljajie-Malinovic I Smit M Bravar AAgic and Z Cerovecki ldquoAdhesive composition systems indegradative conditionsrdquo in Adhesion 14 K W Allen Ed vol14 pp 126ndash160 Springer Berlin Germany 1990

[32] C Prisacariu Polyurethane Elastomers From Morphology toMechanical Aspects Springer Science amp Business Media 2011

[33] X Wu Y Wu C Zhang et al ldquoPolyurethanes prepared fromisocyanates containing triphenylamine derivatives synthesisand optical electrochemical electrochromic and memorypropertiesrdquo RSC Advances vol 5 no 72 pp 58843ndash58853 2015

[34] H C Beachell and C P Son ldquoColor formation in poly-urethanesrdquo Journal of Applied Polymer Science vol 7 no 6 pp2217ndash2237 1963

[35] K Nassau ldquoGamma-ray irradiation induced changes in color oftourmalinesrdquo American Mineralogist vol 60 no 7-8 pp 710ndash713 1975

[36] A V Raghu G S Gadaginamath H M Jeong N T MathewS B Halligudi and T M Aminabhavi ldquoSynthesis and charac-terization of novel schiff base polyurethanesrdquo Journal of AppliedPolymer Science vol 113 no 5 pp 2747ndash2754 2009

[37] R A Assink ldquoRadiation crosslinking of polyurethanesrdquo Journalof Applied Polymer Science vol 30 no 6 pp 2701ndash2705 1985

[38] C Zhou Bulk Preparation of Radiation Crosslinking Poly(Urethane-Imide) INTECH 2012

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


organophilic clay They observed the water swell wasdecreased and thermal resistance was increased as thecontent of clay was increased Reinforcement of polyurethaneby composite with inorganic materials has attracted con-siderable attention in various literature because they exhibitthe enhanced performance properties compared withconventional composites Choi et al 2012 [5] preparednanocomposites of waterborne polyurethane (WPU) rein-forced with functionalized graphene sheets (FGSs) Reddyand coworkers prepared a series of novel segmented poly-urethanes (PUs) containing imine units by polyadditionreaction of various diisocyanates like 441015840-diphenyl-meth-ane diisocyanate (MDI) toluene 24-diisocyanate (TDI)isophorone diisocyanate (IDI) and hexamethylene diiso-cyanate (HDI) with 441015840-[14-phenylenebis(methylyliden-enitrilo)]diphenol based diol [6] with 441015840-pyridine-26-di-ylbis[nitrilomethylylidene]diphenol-based diol [10]

Radiation crosslinking polymerization is one of theimportant research fields of radiation polymerization [11]radiation crosslinking modification of polyurethanes is oneof most important aspects [12] In the study of the radia-tion crosslinking polyurethane a lot of work was done inpolyurethane synthesis in its molecular backbone to importsome unsaturated bond and application of 120574-irradiation torealize the radiation crosslinking in order to obtain a bettercrosslinking effects improved thermal stability and otherproperties of polyurethane In another study on the influenceof electron-beam irradiation in air on the chemical andthe structural properties of medical-grade polyurethane theresults showhomogeneous oxidative degradation followed bya decrease in molecular mass and an increase in polydisper-sity [13] The chain scission is common by the irradiationUV and gamma irradiation in air of polyurethane [14] Inthis paper we irradiated polyurethane film in isolated ofair under vacuum conditions Segmented (soft and hard)polyurethanes (PUs) are a class of thermoplastic elastomersthat bridge the gap between rubbers and plastics and could beinfluenced by irradiation [15]The superior properties of PUsoriginate in the thermodynamic incompatibility between thehard segments (HSs) and soft segments (SSs) When PUsare exposed to high energy irradiation the structure andmechanical property may be altered It is of importance fromboth basic and applied viewpoints to determine how themicrostructure and stability could be influenced by irradia-tion Generally PUs have shown higher radiation resistancecompared with other common polymers such as poly-olefins and vinyl polymers [16] However the effects ofirradiation on the microstructure are complex and closelyrelated to the chemical composition irradiation environ-ment and absorbed dose [17]

In this paper radiation was used in crosslinking ofpolyurethane at room temperature under vacuum of air Theradiation crosslinking affects the characterization of polyure-thane like morphology of microstructure as detected by SEMand thermal stability enhancing with irradiation dose besidethe crystanility as observed from TGA and XRD data Theirradiated PU emits purple fluorescence light when exposedto UV lamp (362 nm)

2 Materials and Method

A commercial 441015840-diphenylmethane diisocyanate (MDI)from the market and polyether were obtained from commer-cial suppliers The MDI and polyether were used as receivedToluene was obtained from Sigma-Aldrich Chemical Co

21 Preparation of Polyurethane Thesynthesis procedurewascarried out on the basis of prepolymer method A weighedquantity of dried 1029 g of polyether polyol was mixed wellwith 150mL toluene and charged into a four-necked flaskand equippedwith stirrer thermometer dropping funnel gasinlet and air condenser with a drying tube During flushingwith a slow stream of nitrogen the mixture was heated attemperature of 55 plusmn 5∘C and stirred Then 40mL of 44-diphenylmethane diisocyanate (MDI) was dropped into themixture gradually over a period of 30min With continuousstirring at the end of the reaction (after 6ndash8 h) the finalproduct was a clear yellowish viscous liquid Isocyanate ter-minated polyurethane prepolymer was formed after castingstep

22 Polyurethane Film Preparation For the preparation ofthe polyurethane film the liquid purified prepolymer wascast onto the surface of a glass plate and then left to becured under ambient conditions A combination of abovereactions occurred due to the simultaneous presence of polyolin the reaction system Finally prepolymer chains completelyreact with an equivalent amount of water leading to theformation of crosslinked polyurethaneThen filmswere driedat variable temperatures ranging from 30∘C to 40∘C for 24 hto ensure slow drying in order to completely remove thesolvent Subsequently the films were removed from the moldand stored in a desiccator at room temperature for furthercharacterization

23 Irradiation Conditions Irradiate the samples at doses of0 50 100 and 150 kGy with the 60 Co Indian irradiationfacility gamma rays at a dose rate 205 KGyh All sampleswere irradiated at room temperature in the absent of air Theirradiation facility was constructed by the National Centerfor Radiation Research and Technology (NCRRT) AtomicEnergy Authority of Egypt (AEAE) Cairo

3 Characterizations of the Samples

31 (ATRFTIR)Raman Spectroscopy The probability ofprepolymerization method with isocyanatepolyol group([N=C=OsimOndashH]) was measured using attenuated totalreflectance-Fourier transform infrared ATR-FTIR spec-troscopy Vertex 70 FTIR spectrometer equipped with HYPE-RION series microscope Bruker Optik GmbH EttlingenGermany over the 4000ndash400 cmminus1 range at a resolution of4 cmminus1 Software OPUS 60 (BRUKER) was used for dataprocessing which was baseline corrected by the rubber bandmethod with CO

2bands excludedThe Ramanmeasurement

was carried out with dispersive Raman spectroscopy at laser785 nm and laser power 010MW Senterra Bruker OpticsGermany








1601(CH=N)

3590(N-H)

1718(C=O)

Tran

smitt

ance

()


(a)

(c)

(d)

(b)







0200400600800

1000120014001600

2886

77

1718

31

1613

56

1532

1182

53

880

50 746

3267

812

Ram

an in

tens

ity


(a)

2886

66

1718

32

1613

42

1532

11

1182

42

880

1574

632

678

33


0

500

1000

1500

2000

2500

Ram

an in

tens

ity

(b)

2886

45

1718

25

1613

07

1532

01 11

825

7

880

1274

612

678

04

0

500

1000

1500

2000

Ram

an in

tens

ity


(c)

2887

69

1613

46

1532

25 11

820

1

880

12 746

2167

822


0

500

1000

1500

2000

2500

Ram

an in

tens

ity

(d)


10 20 30 40 50 60 70 80

2120579

150KGy100KGy

50KGy0KGy



(a)(b)

(c)(d)

11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29102120579














5 Conclusion



(a)

(c)

(d)

(a998400)

(b998400)

(c998400)

(d998400)

(b)





(a) (b) (c) (d)

(I)

(II)

(III)

(a998400998400)

(c998400998400) (d998400998400)

(b998400998400)

(a998400) (b998400) (c998400) (d998400)





150KGy0KGy

100KGy50KGy20

40

60

80

100

Wei

ght l

oss (

)

100 150 200 250 300 350 400 450 50050Temperature (∘C)


150KGy

0KGy

Der

iv w

eigh

t (

∘C) 100KGy

50KGy

100 150 200 250 300 350 400 450 50050Temperature (∘C)


Competing Interests


References















































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials










1601(CH=N)

3590(N-H)

1718(C=O)

Tran

smitt

ance

()


(a)

(c)

(d)

(b)







0200400600800

1000120014001600

2886

77

1718

31

1613

56

1532

1182

53

880

50 746

3267

812

Ram

an in

tens

ity


(a)

2886

66

1718

32

1613

42

1532

11

1182

42

880

1574

632

678

33


0

500

1000

1500

2000

2500

Ram

an in

tens

ity

(b)

2886

45

1718

25

1613

07

1532

01 11

825

7

880

1274

612

678

04

0

500

1000

1500

2000

Ram

an in

tens

ity


(c)

2887

69

1613

46

1532

25 11

820

1

880

12 746

2167

822


0

500

1000

1500

2000

2500

Ram

an in

tens

ity

(d)


10 20 30 40 50 60 70 80

2120579

150KGy100KGy

50KGy0KGy



(a)(b)

(c)(d)

11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29102120579














5 Conclusion



(a)

(c)

(d)

(a998400)

(b998400)

(c998400)

(d998400)

(b)





(a) (b) (c) (d)

(I)

(II)

(III)

(a998400998400)

(c998400998400) (d998400998400)

(b998400998400)

(a998400) (b998400) (c998400) (d998400)





150KGy0KGy

100KGy50KGy20

40

60

80

100

Wei

ght l

oss (

)

100 150 200 250 300 350 400 450 50050Temperature (∘C)


150KGy

0KGy

Der

iv w

eigh

t (

∘C) 100KGy

50KGy

100 150 200 250 300 350 400 450 50050Temperature (∘C)


Competing Interests


References















































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




0200400600800

1000120014001600

2886

77

1718

31

1613

56

1532

1182

53

880

50 746

3267

812

Ram

an in

tens

ity


(a)

2886

66

1718

32

1613

42

1532

11

1182

42

880

1574

632

678

33


0

500

1000

1500

2000

2500

Ram

an in

tens

ity

(b)

2886

45

1718

25

1613

07

1532

01 11

825

7

880

1274

612

678

04

0

500

1000

1500

2000

Ram

an in

tens

ity


(c)

2887

69

1613

46

1532

25 11

820

1

880

12 746

2167

822


0

500

1000

1500

2000

2500

Ram

an in

tens

ity

(d)


10 20 30 40 50 60 70 80

2120579

150KGy100KGy

50KGy0KGy



(a)(b)

(c)(d)

11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29102120579














5 Conclusion



(a)

(c)

(d)

(a998400)

(b998400)

(c998400)

(d998400)

(b)





(a) (b) (c) (d)

(I)

(II)

(III)

(a998400998400)

(c998400998400) (d998400998400)

(b998400998400)

(a998400) (b998400) (c998400) (d998400)





150KGy0KGy

100KGy50KGy20

40

60

80

100

Wei

ght l

oss (

)

100 150 200 250 300 350 400 450 50050Temperature (∘C)


150KGy

0KGy

Der

iv w

eigh

t (

∘C) 100KGy

50KGy

100 150 200 250 300 350 400 450 50050Temperature (∘C)


Competing Interests


References















































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials














5 Conclusion



(a)

(c)

(d)

(a998400)

(b998400)

(c998400)

(d998400)

(b)





(a) (b) (c) (d)

(I)

(II)

(III)

(a998400998400)

(c998400998400) (d998400998400)

(b998400998400)

(a998400) (b998400) (c998400) (d998400)





150KGy0KGy

100KGy50KGy20

40

60

80

100

Wei

ght l

oss (

)

100 150 200 250 300 350 400 450 50050Temperature (∘C)


150KGy

0KGy

Der

iv w

eigh

t (

∘C) 100KGy

50KGy

100 150 200 250 300 350 400 450 50050Temperature (∘C)


Competing Interests


References















































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




(a)

(c)

(d)

(a998400)

(b998400)

(c998400)

(d998400)

(b)





(a) (b) (c) (d)

(I)

(II)

(III)

(a998400998400)

(c998400998400) (d998400998400)

(b998400998400)

(a998400) (b998400) (c998400) (d998400)





150KGy0KGy

100KGy50KGy20

40

60

80

100

Wei

ght l

oss (

)

100 150 200 250 300 350 400 450 50050Temperature (∘C)


150KGy

0KGy

Der

iv w

eigh

t (

∘C) 100KGy

50KGy

100 150 200 250 300 350 400 450 50050Temperature (∘C)


Competing Interests


References















































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




(a) (b) (c) (d)

(I)

(II)

(III)

(a998400998400)

(c998400998400) (d998400998400)

(b998400998400)

(a998400) (b998400) (c998400) (d998400)





150KGy0KGy

100KGy50KGy20

40

60

80

100

Wei

ght l

oss (

)

100 150 200 250 300 350 400 450 50050Temperature (∘C)


150KGy

0KGy

Der

iv w

eigh

t (

∘C) 100KGy

50KGy

100 150 200 250 300 350 400 450 50050Temperature (∘C)


Competing Interests


References















































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




150KGy0KGy

100KGy50KGy20

40

60

80

100

Wei

ght l

oss (

)

100 150 200 250 300 350 400 450 50050Temperature (∘C)


150KGy

0KGy

Der

iv w

eigh

t (

∘C) 100KGy

50KGy

100 150 200 250 300 350 400 450 50050Temperature (∘C)


Competing Interests


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



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