testare cauciuc

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43Revista de Pielarie Incaltaminte 111(2011)

INTRODUCERE

Vulcanizarea este procesul prin care amestecul decauciuc este transformat dintr-un material plastic ntr-unul cu proprieti elastice sau ntr-un material dur.Exist mai multe posibiliti de reticulare a cauciucului.Vulcanizarea cu sulf a fost prima metod de reticularedescoperit i n prezent este nc cea mai cunoscut.

INTRODUCTION

Vulcanisation is the process by means of whichrubber blend is changed from essentially a plasticmaterial to either an elastic or a hard material. Thereare several possibilities for the crosslinking of rubber.Sulphur vulcanisation was the first to be discovered andstill is today's most common cure system. Other

CHARACTERISTICS OF NATURAL RUBBER BLENDS VULCANIZED WITH ELECTRON BEAM ANDMICROWAVE

CARACTERISTICILE UNOR AMESTECURI DE CAUCIUC NATURAL VULCANIZATE CU ELECTRONI ACCELERAII MICROUNDE

1* 2 1Elena MANAILA , Maria Daniela STELESCU , Gabriela CRACIUN

1National Institute for Laser, Plasma and Radiation Physics, Electron Accelerators Laboratory, 409 Atomitilor St., 077125 Magurele, Romania,email: [email protected]

2National Research and Development Institute for Textile and Leather Leather and Footwear Research Institute, 93 Ion Minulescu St.,Bucharest, Romania, email: [email protected]

CHARACTERISTICS OF NATURAL RUBBER BLENDS VULCANIZED WITH ELECTRON BEAM AND MICROWAVEABSTRACT. This paper presents the effect of the polyfunctional monomers (PFMs) triallyl cyanurate (TAC), triallyl isocyanurate (TAIC), trimethylopropanetrimethacrylate (TMPT) and zinc diacrylate (ZDA) on the mechanical properties of the NR (natural) rubber crosslinked by electron beam (EB) and microwave

processing. The control samples were obtained by crosslinking with benzoyl peroxide in a hydraulic press at 160C. The most effective polyfunctional monomerwhich led to getting the best properties was TMPT followed by ZDA. The results indicate that the application of new technologies will lead to a significantimprovement in physical and mechanical properties of finished products and to optimizing the curing stage, the most important operation of the technologicalprocess for obtaining elastomeric materials.KEY WORDS: natural rubber, cross-linking, electron beam, microwave, polyfunctional monomers.

CARACTERISTICILE UNOR AMESTECURI DE CAUCIUC NATURAL VULCANIZATE CU ELECTRONI ACCELERAI I MICROUNDEREZUMAT. Aceast lucrare prezint efectul monomerilor polifuncionali trialilcianurat (TAC), trialilizocianurat (TAIC), trimetil-propan-trimetacrilat (TMPT) idiacrilat de zinc (ZDA) asupra proprietilor mecanice ale cauciucului natural (NR) reticulat prin iradiere cu electroni accelerai (EA) i microunde (MU). Probelemartor au fost obinute prin reticulare cu peroxid de benzoil la temperatura de 160C ntr-o pres hidraulic. Monomerul polifuncional care a condus la obinereacelor mai bune caracteristici a fost TMPT urmat de ZDA. Datele obinute ne indic faptul c aplicarea metodei inovative de reticulare prin iradiere cu EA i MU vaconduce la o mbuntire semnificativ a proprietilor fizico-mecanice ale produselor finite i la optimizarea etapei de vulcanizare, care este cea mai importantoperaie din fluxul tehnologic de obinere a materialelor elastomerice.CUVINTE CHEIE: cauciuc natural, reticulare, peroxid, electroni accelerai, microunde, monomeri polifuncionali.

LES CARACTRISTIQUES DES MLANGES DE CAOUTCHOUC NATUREL VULCANISS PAR FAISCEAU D'ELECTRONS ET MICRO-ONDES

RSUM. Cet article prsente l'effet des monomres polyfonctionnels triallyl cyanurate (TAC), triallyl isocyanurate (TAIC), trimthyl-propane-trimthacrylate(TMPT) et diacrylate de zinc (ZDA) sur les proprits mcaniques du caoutchouc naturel (NR) rticul par irradiation avec des lectrons acclrs (EA) et avec desmicro-ondes (MO). Les chantillons de contrle ont t obtenus l'aide de rticulation parperoxyde de benzoyle une temprature de 160C dans une pressehydraulique. Le monomre polyfonctionnel qui a conduit l'obtention des meilleures caractristiques a t TMPT suivi de ZDA. Les donnes indiquent quel'application de la mthode novatrice de rticulation par irradiation avec EA et MO conduira une amlioration significative des proprits physiques etmcaniques des produits finis et d'optimiser la phase de vulcanisation, qui est l'opration la plus importante du processus technologique d'obtention des matriauxlastomriques.MOTS CLS: caoutchouc naturel, rticulation, peroxyde, lectrons acclrs, micro-ondes, monomres polyfonctionnels.

*Correspondence to Elena MANAILA, National Institute for Laser, Plasma and Radiation Physics, Electron Accelerators Laboratory, 409 Atomitilor St., 077125

Magurele, Romania, email: [email protected]


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Alte sisteme de reticulare, precum cele bazate peutilizarea peroxizilor, a radiaiei ultraviolet, a riniloretc., au fost descoperite ulterior i au ctigat o mai mareimportan odat cu dezvoltarea progresiv acauciucurilor sintetice [1]. Tehnologia de reticulare curadiaii (electroni accelerai, microunde, radiaii gamma)a aprut ca o alternativ la tehnicile obinuite utilizatepentru prelucrarea materialelor din cauciuc i prezintmulte avantaje fa de acestea [2]. Vulcanizarea cuelectroni accelerai (EA) a condus la obinerea unorrezultate superioare comparativ cu tehnicile convenionalede vulcanizare deoarece: polimerul nu mai este degradatdatorit temperaturilor nalte deoarece reticularea cu EAare loc la temperatura camerei, nu mai are loc degenerareaoxidativ observat n reticularea clasic, se realizeazlegturi C-C care sunt foarte puternice, un grad mare dereticulare, ciclurile de reticulare sunt extrem de scurte,productivitatea este foarte mare, se preteaz foarte binela tratarea produselor subiri, pierderea de material estefoarte mic [3, 4]. Avantajele utilizrii microundelor (MU)sunt urmtoarele: transfer rapid de energie, nclzireselectiv i n volum, randament mare de nclzire [5-7].Cu toate acestea, vulcanizarea cauciucului natural (NR)cu ajutorul radiaiilor nu s-a utilizat pe scar larg datoritcosturilor mari legate de procesul de iradiere, dar idatorit calitilor slabe ale produselor conferite detratamentul cu radiaii. Vulcanizarea cu radiaii a NR adevenit un proces industrial atunci cnd, prin utilizareaunor sensibilizatori, doza de radiaii a sczut. Literaturade specialitate sugereaz c utilizarea unor monomeripolifuncionali (MP) adecvai [8-10] poate conduce att lascderea dozei de radiaii, ct i la obinerea proprietilorfizice dorite [11-14].

Ideea acestei lucrri este aceea de a combinaefectele iradierii cu EA, a nclzirii cu MU i a utilizrii MPpentru a reduce doza de iradiere cu EA i pentru a aducembuntiri semnificative proprietilor produselor dincauciuc natural. Am ales pentru acest studiu cauciuculnatural, datorit numeroaselor lui aplicaii. Pentruexemplificare, amintim doar c ntre 65 % i 70 % dinproducia total de cauciuc natural este folosit ca materieprim pentru producerea anvelopelor de maini [15].

Materiale

n studiu s-au utilizat urmtoarele materiale:cauciucul natural Crep (vscozitatea Mooney

PARTEA EXPERIMENTAL

44Leather and Footwear Journal 11 (2011) 1

vulcanisation systems, i.e. peroxides, ultraviolet light,resins, etc. were later discovered and gained moreimportance with the progressive development ofsynthetic rubbers [1]. Radiation technology (electron

beam, microwave, gamma rays) has emerged as one ofthe foremost techniques for the processing of rubbermaterials and has many advantages over otherconventional methods [2]. Electron beam (EB)vulcanization has demonstrated extremely positiveresults compared to the conventional curing systemsuch as: no polymer degradation due to hightemperature, as EB cross-linking occurs at roomtemperature, no oxidative degeneration in polymers asobserved in classical cross-linking, direct cross-linkingby C-C linkage by EB, extremely strong bonds, highdegree of cross-linking, extremely short curing cycles,

very high productivity, perfect for thin products, lowermaterial waste [3, 4]. The advantages of usingmicrowaves (MW) can be summarized as follows: rapidenergy transfer, volumetric and selective heating, veryhigh heating rate [5-7]. However, the radiation cross-linking of NR was not used in larger technicalapplications because of the high cost of irradiation tobring about vulcanization and the low quality ofproducts from the radiation cross-linked NR. Theradiation cross-linking of NR became an industrialprocess when the radiation dose decreased with the

use of some sensitizers. Reported papers suggest thatappropriate polyfunctional monomers (PFMs) inpolymer matrix [8-10] could be used to obtain desiredrubber physical properties at lower irradiation doses[11-14].

The main idea of this paper is to combine theeffects of EB irradiation, MW heating and PFMs in orderto reduce the required electron beam dose level and toimprove the natural rubber properties. We chose tostudy natural rubber, due to its numerous applications.For example, between 65% and 70% of the totalproduction of natural rubber is used as raw material forcar tires [15].

Materials

The following materials were used in the study:natural rubber Crep 1X (Mooney viscosity is 74

EXPERIMENTAL

E. MANAILA, D.M. STELESCU, G. CRACIUN


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74 ML la 100C, coninutul de materii volatile 0,32%,1+4coninutul de azot 0,38%, coninutul de cenu 0,22%,coninutul de impuriti 0,021%);trialilcianurat TAC DL 70 (coninutul de cenu

3

26%, densitate 1,34 g/cm , conine agent activ 70% isilice activ 30%);trialilizocianurat TAIC DL 70 (densitate 1,343g/cm , pH 2,6);trimetilpropan-trimetacrilat TMPT DL 75

3(coninutul de cenu 22%, densitate 1,36 g/cm ,conine agent activ 75 3%, pH 9,2);diacrilat de zinc ZDA GR 75 (conine agent activ

375 3%, densitate 1,23 g/cm );peroxidul de benzoil Perkadox 14-40B-GB

3(densitate 1,60 g/cm , coninutul de oxigen activ 3,8%,coninutul de peroxid 40%).

Pregtirea probelor

Amestecurile s-au realizat prin tehnica amestecrii peun val de laborator cu nclzire electric. Pentru obinereaamestecurilor de cauciuc natural cu monomeripolifuncionali, materialele componente au fost adugate nurmtoarea ordine: 100 phr NR i 3 phr monomerpolifuncional (TAC, TAIC, TMPT i respectiv ZDA). Parametriiprocesului au fost: temperatura 25-50C, fricia 1:1:1, timpultotal de amestecare 5 minute. Plcile necesare pentrurealizarea determinrilor fizico-mecanice s-au obinut cu

ajutorul unei prese hidraulice la 110 5C i 150 MPa. Probelemartor pentru vulcanizarea cu peroxid de benzoil au fostobinute n mod similar cu obinerea probelor pentru iradiere,cu urmtoarea diferen: s-au adugat 8 phr peroxid debenzoil ca agent de vulcanizare i probele au fost vulcanizatentr-o pres hidraulic la 160C; timpul de vulcanizare a fostdeterminat cu ajutorul reometrului Monsanto.

Instalaiile experimentale i iradierea probelor

Problele de cauciuc au fost supuse urmtoarelormetode de vulcanizare:

Vulcanizarea clasic cu peroxid de benzoil (PB-V) la temperatura de 160C i presiune de 150 MPa,utiliznd o pres hidraulic electric.Vulcanizarea cu EA (EA-V) i vulcanizarea cu

EA+MU (EA+MU-V), utiliznd o instalaie experimentalcare permite iradierea separat i succesiv sausimultan cu EA i MU.

Instalaia experimental are urmtoarelecomponente principale: o surs de EA, o surs de MU

45Revista de Pielarie Incaltaminte 11 (2011) 1

ML at 100C, 0.32% volatile materials content, 0.38%1+4nitrogen content, 0.22% percentage of ash, 0.021%impurities content);triallylcyanurate TAC DL 70 (2% percentage of

3

ash, density 1.34 g/cm , 30% active synthetic silica);triallylisocyanurate TAIC DL 70C (pH 2.6,

3density 1.34 g/cm );trimethylopropane-trimethacrylate TMPT DL

375 (22% percentage of ash, pH 9.2, density 1.36 g/cm ,75 3% active ingredient);zinc-diacrylate ZDA GR 75 (75 3% active

3ingredient, density 1.23 g/cm );dibenzoyl peroxide Perkadox 14-40B (1.603g/cm density, 3,8% active oxygen content, 40%

peroxide content, pH=7).

Preparation of the Samples

Blends were prepared on an electrically heatedlaboratory roller mill. For preparation of NR withpolyfunctional monomers, the blend constituents wereadded in the following sequence and amounts: 100 phrNR and 3 phr polyfunctional monomers (TAC, TAIC,TMPT and ZDA respectively). Process variables:temperature 25-50C, friction 1:1.1, and total blendingtime 5 min. Plates required for physico-mechanicaltests were obtained by pressing in a hydraulic press at

110 5C and 150 MPa. Dibenzoyl peroxide vulcanizedsamples ware prepared similarly to the experimentalones with the following specifications: 8 phr ofdibenzoyl peroxide as vulcanizing agent was added andthe blend vulcanization was achieved in a hydraulicpress at 160C; the vulcanization time was measured bymeans of Monsanto Rheometer.

Experimental Installations and Sample Irradiation

The rubber samples were subjected to thefollowing vulcanization methods:

Conventional vulcanization with benzoylperoxide (BP-V) at 160C and 150 MPa by using anelectrical hydraulic presser;EB vulcanization (EB-V) and EB+MW

vulcanization (EB+MW-V) with an experimentalinstallation that permits separate and successive orsimultaneous EB and MW processing.

The experimental installation consists mainly of

the following units: an accelerated electron beam

CHARACTERISTICS OF NATURAL RUBBER BLENDS VULCANIZED WITH ELECTRON BEAM AND MICROWAVE


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de 2,45 GHz i o cavitate rectangular multimod,utilizat drept camer de reacie. Ca surs de EA s-afolosit acceleratorul de electroni ILU-6M cu energia de1,8 MeV i puterea de 10,8 kW. Acesta se afl laInstitutul de Proiectare si Cercetare Electric dinBucureti, Romnia. ILU-6M este un accelerator de tiprezonator, care opereaz la 1155 MHz i caregenereaz un fascicol pulsat de electroni cu duratapulsului de 0,375 ms pn la o intensitate a curentuluide vrf de 0,32 A i o intensitate medie a curentului de6 mA. Seciunea transversal a fascicolului de EAscanat la fereastra de ieire este de 1100 mm x 65 mm.Efectele EA sunt corelate cu doza absorbit (D),

-1exprimat n Gray sau J kg . Doza absorbit pe osingur trecere a conveiorului prin fascicol se poateajusta n intervalul 12,5 kGy pn la 50 kGy. Pentru a fitratate cu EA sau EA+MU, probele de cauciuc s-au

tiat n foi de 2 mm grosime, ntre care s-au pus foi depolietilen pentru a minimiza oxidarea. Straturi decte trei foi s-au iradiat prin trecerea repetat aacestora cu ajutorul conveiorului pe sub fascicolulscanat de EA generat de acceleratorul ILU-6M.

n Figura 1 este prezentat fotografia probelorde cauciuc - sandwich, aflate pe conveiorulacceleratorului chiar n momentul n care acesta seafl n trecere prin fascicol.


source, a microwave source of 2.45 GHz and a

multimode rectangular cavity used as reaction

chamber. As accelerated electron beam source is used

the electron accelerator ILU-6M of 1.8 MeV and 10.8

kW output power. It is placed at Electrical Project andResearch Institute from Bucharest, Romania. The ILU-

6M is a resonator-type accelerator, operating at 1155

MHz. This accelerator generates electron beam pulses

of 0.375 ms duration, up to 0.32 A current peak

intensity and up to 6 mA mean current intensity. The

cross-sectional size of the scanned EB at the ILU-6M

vacuum window exit is 1100 mm x 65 mm. The EB

effects are related to the absorbed dose (D), expressed-1in Gray or J kg . The single pass dose with conveyor

under the ILU-6M scanner is adjustable from 12.5 kGy

to 50 kGy. For EB and EB+MW treatments the rubbersamples were cut as compressed sheets of 2 mm thick

in the polyethylene foils to minimize oxidation. The

layers of three sandwiched sheets were irradiated by

repeatedly passing on a conveyor under the ILU-6M

scanner.Figure 1 presents the photograph of sandwiched

rubber sheets under EB scanner of ILU-6M.

Figure 1. Photograph of sandwiched rubber sheets under EB scanner of ILU-6MFigura 1. Fotografia probelorde cauciuc- sandwich aflate sub baleiorul acceleratorului ILU-6M



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Mechanical Properties

The tensile strength was measured on dumb-bellshaped specimen according to ISO 37/2005. Tearstrength was performed according to SR EN

12771/2003 using angular test pieces (type II). Thetesting of samples was carried out with the testingspeed 460 mm/min. at room temperature with aSchoppler machine. Elasticity was evaluated with aSchob test machine using 6 mm thick samples,according to ISO 46662/1986.

Polyfunctional monomers are effective on

modification of polymer material by crosslinking.Generally speaking, there are two factors which affectthe functionality of polyfunctional monomers inpolymer: one is the unsaturation of polyfunctionalmonomers and the other is the solubility ofpolyfunctional monomers in polymer [16]. Thepolyfunctional monomers can participate in a numberof radical reaction mechanisms, including grafting andradical addition. These polyfunctional monomers canbe grouped according to their influence on cure kineticsand ultimate physical-mechanical properties. Type I

polyfunctional monomers are highly reactive andincrease both the rate and state of cure (acrylate,methacrylate, or maleimide functionality). Type IIpolyfunctional monomers are based on allyl reactive sitesand increase the state of cure only. Monomeric formsinclude allyl containing cyanurates, isocyanurates andphthalates. For elastomers with high reactivity or highunsaturation levels such natural rubber, type I is bestsuited for increasing tensile strength, modulus andminimizing compression set. For elastomers with lowerreactivity or a fully saturated structure such as chlorinated

polyethylene, type II may be best to improve physical-mechanical properties [17, 18].

In our study we used four polyfunctional monomers:TAC (triallylcyanurate) and TAIC (triallylisocyanurate) oftype I, and TMPT (trimethylopropane trimethacrylate) andZDA (zinc diacrylate) of type II.

The EB and EB + MW irradiation methods, appliedto the above mentioned rubber types, is based on ourresearch reported in [6], that demonstrated an

RESULTS AND DISCUSSIONS

Determinarea proprietilor mecanice

Rezistena la rupere a fost msurat utilizndepruvete n form de halter conform ISO 37/2005.Rezistena la sfiere a fost efectuat conform SR EN

12771/2003 utiliznd epruvete unghiulare (tip II).Determinrile au fost efectuate cu viteza de testare de460 mm/min. la temperatura camerei cu un aparatSchoppler. Elasticitatea a fost evaluat cu un aparat detestare Schob utiliznd epruvete cu grosimea de 6 mm,conform ISO 46662/1986.

Monomerii polifuncionali sunt eficieni atunci

cnd se dorete modificarea unui material polimeric prinreticulare. Se cunosc doi factori care pot afectafuncionalitatea MP n polimer. Acetia sunt nesaturareaMP i solubilitatea lui n polimer [16]. MP pot participaactiv ntr-un numr de mecanisme de reacie radicalice,incluznd grefarea i adiia radicalic. Aceti monomeripolifuncionali pot fi clasificai, n funcie de influena pecare o au asupra cineticii reaciilor sau proprietilor fizico-mecanice. Monomerii polifuncionali de tipul I suntputernic reactivi i conduc att la creterea vitezei dereticulare, ct i la creterea gradului de reticulare (sunt de

tip acrilat, metacrilat sau maleimide). Monomeriipolifuncionali de tipul II sunt cei bazai pe poziiile reactiveale gruprii alil i care cresc doar gradul de reticulare.Tipurile de monomeri care includ grupri alil conincianurai, izocianurai i ftalai. n cazul elastomerilor cureactivitate mare sau un grad mare de nesaturare, cumeste cazul cauciucului natural, tipul I de MP este cel maipotrivit pentru c mbuntete rezistena la rupere,modulul i reduce deformarea permanent lacompresie. Pentru elastomerii cu reactivitate sczutsau avnd o structur saturat cum ar fi polietilena

clorurat, MP de tipul II sunt cei mai potrivii pentru ambunti proprietile fizico-mecanice [17, 18].

n cazul studiului nostru am utilizat patru MP: doide tipul I, respectiv TAC (trialilcianurat) i TAIC(trialilizocianurat) i doi de tipul II, respectiv TMPT(trimetilpropan-trimetacrilat) i ZDA (acrilat de zinc).

Metoda de iradiere combinat cu EA i MU aprobelor de cauciuc de tipul celor menionate mai susare la baz studii efectuate anterior [6], care au

REZULTATE I DISCUII



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important reduction of EB absorbed dose by MWadditional use to EB energy.

The mechanical properties of samples aresummarized in Tables 1-4.

demonstrat o reducere semnificativ a dozei de EA prinutilizarea adiional a energiei MU la cea a EA.

Proprietile mecanice ale probelor supuse unuiastfel de tratament sunt sintetizate n Tabelele 1-4.

Table 1: Physical-mechanical characteristics of blends: NR+TACTabelul 1: Caracteristicile mecanice ale probelor NR+TAC

Tensile strength, N/mm2

Rezistena la rupere, N/mm2

Alungirea la rupere, %Elongation at break, %

Residual elongation, %

Alungirea remanent, %

Tear strength, N/mm

Rezistena la sfiere, N/mm

Modulul 100%, , N/mm

BP vulcanization

Vulcanizare cu PB

EB vulcanization

Vulcanizare cu EA

EB+MW vulcanization

Vulcanizare combinat

EA+MU

Mechanical characteristics

Caracteristici mecanice

NR - P

5 Mrad

10 Mrad

5 Mrad + 55

50

44

44

42

0.9

0.8

0.9

4.6

87

487

300

935

5

15

8

19

2 9.5 14.5 11

-

0.3

0.4

0.19

100% Modulus, N/mm 2

2

Elasticity, %

Elasticitate, %

Table 2: Physical-mechanical characteristics of blends: NR+TAICTabelul 2: Caracteristicile mecanice ale probelor NR+TAIC



Alungirea la rupere, %

Elongation at break, %

Residual elongation, %Alungirea remanent, %

Tear strength, N/mm



NR - P

BP vulcanization

Vulcanizare cu PB

EB vulcanization

Vulcanizare cu EA

EB+MW vulcanization

Vulcanizare combinat

EA+MUMechanical characteristics

Caracteristici mecanice

5 Mrad

10 Mrad

5 Mrad + 55


2

Elasticity, %

Elasticitate, %

68

42

42

50

-

0.4

0.4

0.21

0.96

0.7

2.2

4.8

87

387

647

850

9 11 13 15

2.5 7 13 13



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Analiznd rezultatele caracteristicilor mecaniceobinute la probele reticulate cu EA n comparaie cucele ale amestecurilor reticulate cu peroxid n prezena


Analyzing the mechanical characteristicsobtained from the EA cross-linked samples comparedwith those of cross-linked with peroxide mixtures in the





Residual elongation, %

Alungirea remanent, %

Tear strength, N/mm



BP vulcanization

Vulcanizare cu PB

EB vulcanization

Vulcanizare cu EA

EB+MW vulcanization

Vulcanizare combinatEA+MU

Mechanical characteristicsCaracteristici mecanice

NR - P

5 Mrad

10 Mrad

5 Mrad + 55


2

Elasticity, %

Elasticitate, %

68

48

53

48

-

0.4

0.4

0.29

0.82

3.6

8.3

8.7

60

673

727

785

3

9

7

14

1.39 13.5 21 13

Table 3: Physical-mechanical characteristics of blends: NR+TMPTTabelul 3: Caracteristicile mecanice ale probelor NR+TMPT

Table 4: Physical-mechanical characteristics of blends: NR+ZDATabelul 4: Caracteristicile mecanice ale probelor NR+ZDA





Residual elongation, %Alungirea remanent, %

Tear strength, N/mm



BP vulcanization Vulcanizare cu PB

EB vulcanization Vulcanizare cu EA

EB+MW vulcanizationVulcanizare combinat

EA+MU

Mechanical characteristics Caracteristici mecanice

NR - P

5 Mrad10 Mrad

5 Mrad + 55

100% Modulus, N/mm 2 2

Elasticity, %Elasticitate, %

66

46

50

50

-

0.39

0.51

0.26

1.3

0.99

3

3.7

140

340

607

675

2

10

6

11

4.5 7.5 18 18



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presence of the same types of MP the following can beobserved:

- significant improvements in tensile strength(between 130% for NR+TAIC and NR+ZDA at 10 Mrad,

and 912% for NR+TMPT at 5 Mrad;- elongation at break increases, for allpolyfunctional monomers type, the smallest increasebeing 142% for NR+ZDA at 5 Mrad and highest 1112%for NR+TMPT at 10 Mrad;

- tear strength increases with radiation dose,(between 180% for NR+TAIC at 5 Mrad, and 1410% forNR+TMPT at 10 Mrad;

- for all samples a decrease in elasticity wasnoticed.

Relatively low residual elongation values indicatea good return to its original shape after applying a force,and therefore an efficient curing for all samples. Inconclusion, even at a dose of 5 Mrad an efficientcrosslinking of NR was achieved. The polyfunctionalmonomer influence on these parameters for thesamples vulcanized with EB is the following: TMPT >ZDA > TAC > TAIC.

Comparing the mechanical characteristicsobtained from the EA+MW cross-linked samples withthose cross-linked with peroxide mixtures in thepresence of the same types of MP a significantimprovement can be observed in tensile strength (up to

411% for NR+TAC, 400% for NR+TAIC, 960% forNR+TMPT and 184% for NR+ZDA), in elongation atbreak (up to 974% for NR+TAC, 877% for NR+TAIC,1208% for NR+TMPT and 382% for NR+ZDA) and tearstrength (up to 450% for NR+TAC, 420% for NR+TAIC,835% for TMPT and 300% for NR+ZDA). The order ofinfluence of polyfunctional monomers on the studiedparameters for EA+MW is identical to that in the case ofirradiation with EA (TMPT > ZDA > TAC > TAIC).

Improved characteristics of hardened mixtureswith EA and EA + MW from the hardened peroxide are

due, on the one hand, to the advantages of acceleratedelectrons (the process is very fast, and due to highpenetration power of radiation there is an effective anduniform curing), and on the other hand, to theadvantages of microwave (promote a narrowdistribution of the molecular masses, as the cross-linking occurs simultaneously in the bulk of materialbecause of the microwave interaction with all materialunder irradiation; promote fast cross-linking processes)[3, 6]. Also, due to reduced processing time, thermal

acelorai tipuri de MP, se poate observa:- mbuntirea semnificativ a rezistenei la

rupere (cu 130% pentru NR+TAIC i NR+ZDA iradiate cu10 Mrad, i cu 912% pentru amestecurile NR+TMPT

iradiate cu 5 Mrad);- creterea alungirii la rupere pentru toateamestecurile iradiate, cea mai mic cretere fiind de142% pentru amestecurile NR+ZDA, iar cea mai marede 1112% pentru amestecurile de NR+TMPT);

- creterea rezistenei la sfiere cu doza deiradiere (cuprins ntre 180% pentru amesteculNR+TAIC iradiat cu 5 Mrad, i cu 1410% pentruamestecul NR+TMPT iradiat cu 10 Mrad);

- scderea elasticitii pentru toate probele iradiate.Valorile relativ sczute ale alungirii remanente

indic o foarte bun revenire la forma iniial dupaplicarea unei fore, deci o vulcanizare eficient pentrutoate probele. n concluzie, chiar i la o doz de 5 Mrads-a realizat o reticulare eficient a NR. Influenamonomerilor polifuncionali asupra acestor parametripentru vulcanizarea cu EB scade n ordinea TMPT > ZDA> TAC > TAIC.

Comparnd rezultatele caracteristicilor mecaniceobinute pentru probele reticulate cu EA+MW i respectivcu peroxizi n prezena acelorai tipuri de MP, se observ ombuntire semnificativ a rezistenei la rupere (de pnla 411% pentru NR+TAC, 400% pentru NR+TAIC, 960%

pentru NR+TMPT i 184% pentru NR+ZDA), a alungirii larupere (de pn la 974% pentru NR+TAC, 877% pentruNR+TAIC, 1208% pentru NR+TMPT i 382% pentruNR+ZDA) i a rezistenei la sfiere (de pn la 450% pentruNR+TAC, 420% pentru NR+TAIC, 835% pentru NR+TMPT i300% pentru NR+ZDA). Ordinea influenei MP asupraparametrilor studiai n cazul tratamentului combinatEA+MU este identic cu cea din cazul iradierii cu EA (TMPT> ZDA > TAC > TAIC).

mbuntirea caracteristici lor amestecurilorreticulate cu EA i EA+MW fa de cele reticulate cu

peroxid se datoreaz pe de o parte avantajelor adusede EA (procesul este foarte rapid, datorit puterii maride penetrare a radiaiilor, are loc o vulcanizare eficienti uniform n toat masa elastomerului), iar pe de altparte avantajelor aduse de microunde (realizeaz odistribuie ngust a maselor moleculare deoareceprocesul de reticulare i grefare se iniiaz simultan ntoat masa sistemului ca efect direct al proprietiimicroundelor de a interaciona cu tot volumul dematerial supus iradierii; realizeaz o accelerare a



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degradation, which can occur when keeping theelastomer at high temperatures of about 160C for 10-30 min., is removed.

Analyzing the influence of polyfunctional

monomers type on characteristics, it can be seen thatthe best results were obtained using TMPT followed byZDA (Type I curing coagents). Type I polyfunctionalmonomers are highly reactive and increase the rate andstate of cure. Type II (TAC and TAIC) polyfunctionalmonomers increase only the state of cure. Also, theinfluence of polyfunctional monomers on the increaseof the mechanical characteristics is determined by thereactivity, the number of reactive groups (functionality):TMPT has functionality three and ZDA has functionalitytwo [17-18].

The study demonstrated that mechanicalproperties such as tensile strength, elongation at breakand tearing strength improved as a function ofincreased irradiation dosage and polyfunctionalmonomers type. Comparing mechanical parameters ofthe samples obtained by EB vulcanization and EB+MWvulcanization with those vulcanized with dibenzoylperoxide, it is easy to notice a higher efficiency.

Improvement in tensile strength, elongation at breakand tearing strength is considerable for TMPT and ZDA(type I polyfunctional monomers) whereas onlymarginal improvements are seen for TAC and TAIC (typeII polyfunctional monomers).

Crosslinking by EB and MW also shows a series ofadvantages, such as: reduced crosslinking time andpower expenditure, no polymer degradation due tohigh temperature as EB cross-linking occurs at roomtemperature, the process is very fast and can beprecisely controlled, the electron beam can be steeredvery easily to meet the requirements of various

geometrical shapes of the products to be cured, veryhigh productivity, perfect for thin products [3, 6].

CONCLUSIONS

REFERENCES

1. Stelescu, M.D., Characteristics of Silicone Rubber Blends, Revista de Pielarie Incaltaminte (Leather and Footwear

Journal), 2010, 10, 3.2. Bhattacharya, A., Prog. Polym. Sci., 2000, 25, 371-401.

procesului de reticulare) [3, 6]. De asemenea, datoritreducerii timpului de procesare, se nltur degradareatermic care poate aprea n cazul meninerii elastomeruluila temperaturi de cca 160C timp de 10-30 min.

Analiznd influena tipului de MP asupracaracteristicilor se poate observa c cele mai bune rezultates-au obinut prin utilizarea TMPT urmat de ZDA (coageni dereticulare de tip I). Monomerii polifuncionali de tipul I suntfoarte reactivi i cresc viteza i gradul de reticulare.Monomerii polifuncionali de tipul II (TAC i TAIC) cresc doargradul de reticulare. De asemenea, influena monomerilorpolifuncionali la creterea proprietilor mecanice estedeterminat i de reactivitatea lor, de numrul de grupereactive: TMPT are funcionalitatea trei, iar ZDA arefuncionalitatea doi [17-18].

Studiile demonstreaz c proprietile mecanicecum ar fi rezistena la rupere, alungirea la rupere irezistena la sfiere prezint mbuntiri semnificative

n funcie de doza de iradiere i tipul de MP utilizat. Sepoate observa cu uurin eficiena crescut avulcanizrii cu EA i EA+MU fa de vulcanizarea cuperoxid prin compararea parametrilor mecanici aiprobelor astfel vulcanizate. mbuntirea rezistenei la

rupere, alungirii la rupere i rezistenei la sfiere esteconsiderabil n cazul utilizrii MP de tipul I (TMPT i ZDA)i mai mic n cazul utilizrii MP de tipul II (TAC i TAIC).

Vulcanizarea cu EA i MU prezint o serie deavantaje fa de vulcanizarea clasic, cum ar fi: timpul devulcanizare redus, apariia procesului de degradare apolimerului datorit temperaturii este evitat deoarecetratamentul cu radiaii are loc la temperatura camerei,procesul este foarte rapid i poate fi precis controlat,fascicolul de EA poate fi uor direcionat i adaptatcerinelor geometrice i formelor produsului careurmeaz a fi vulcanizat, productivitate ridicat, este

foarte potrivit pentru vulcanizarea produselor subiri[3, 6].

CONCLUZII




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3. MGM Rubber Company-Research and Development, Electron Beam Radiation Technology for Curing, 2007,http://www.mgmrc.com/ebeam-trech.htm.

4. Holl, P., Rad. Phys. and Chem., 1995, 46, 46, 953-958.5. Leprince, P., Marec, J., Plasma Technology, M. Capitelli, G. Borke (eds.), Plenum Press, New York, 1992, 167-183.

6. Martin, D., Ighigeanu, D., Mateescu, E., Craciun, G., Ighigeanu, A., Rad. Phys. Chem.,2002, 65, 1, 63-65.7. Martin, D., Jianu, A. and Ighigeanu, D., IEEE Transactions on Microwave Theory and Techniques, 2001,49, 3, 542-544.8. Makuuchi, K., Yoshii, F., Gunewardena, J. A., Rad. Phys. Chem., 1995, 46, 46, 979-982.9. Vijayabaskar, V., Bhowmick, A. K.,J. Appl. Polym. Sci.,2005, 95, 435.10. Yasin, T., Ahmed, S., Ahmed, M., Yoshii, F., Rad. Phys. Chem., 2005, 73, 3, 155-158.11. Hafezi, M., Khorasani, S.N., Ziaei, F.,J. Polymer Eng., 2007, 27, 3, 165-181.12. Banik, I., Bhowmick, A.K., Rad. Phys.Chem., 2000,58, 293-298.13. Bhattacharya, A., Prog.Polym. Sci., 2000, 25, 371-401.14. Bohm, G.A., Tveekrem, J.O.,Rub. Chem. Tech.,1982,55, 575-668.15. Davidescu, C.M., Applications of Polymers (in Romanian), 1992, Technical University of Timisoara Press, Timisoara.16. Yunshu, X., Yoshii, F., Makuuchi, K.,J. Macromol. Sci.(Pure Appl. Chem.), 1995, A32, 10, 1801-1808.17. Henning, S.K., Wire & Cable Technology International, 2008, Vol. XXXVI, No. 3.18. Boye, W.M., Proceedings of the 57th International Wire & Cable Symposium, 2008, 335-341.


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