All sources 100 Internet sources 55
[18]
iopscience.iop.org/article/10.1088/1757-899X/223/1/012006/pdf 2.6% 10 matches[22]
www.aensiweb.net/AENSIWEB/aejsa/aejsa/2014/99-103.pdf 1.7% 10 matches[25]
journals.sagepub.com/doi/abs/10.1177/0095244316639634 2.0% 7 matches[27]
https://www.sciencedirect.com/science/article/pii/S0142941811001188 1.8% 7 matches[28]
https://rd.springer.com/content/pdf/10.1007/s10853-015-9188-5.pdf 1.9% 5 matches[38]
https://www.researchgate.net/publication..._Rubber_Vulcanizates 1.1% 4 matches[39]
mss-nde.uoi.gr/publications-pdf/journal-...tor System. .pdf 0.8% 5 matches[41]
https://link.springer.com/content/pdf/10.1007/978-3-319-48806-6_5.pdf 1.1% 3 matches[42]
www.scielo.br/scielo.php?script=sci_arttext&pid=S0104-14282017000200116 1.0% 3 matches[43]
www.ukm.my/jsm/pdf_files/SM-PDF-43-2-2014/11 Wirach.pdf 1.0% 3 matches[44]
downloads.hindawi.com/journals/jpol/2013/279529.xml 1.0% 3 matches[45]
www.tandfonline.com/doi/citedby/10.1080/10236660802190104?scroll=top&needAccess=true 1.0% 2 matches[46]
https://www.scientific.net/KEM.751.320 0.9% 2 matches[47]
www.oalib.com/paper/3078170 0.9% 2 matches[48]
pubs.acs.org/doi/full/10.1021/bm0201284?src=recsys 0.9% 2 matches[49]
pubs.acs.org/doi/abs/10.1021/bm030058g 0.9% 2 matches[50]
koreascience.or.kr/article/ArticleFullRecord.jsp?cn=HKGMCJ_2014_v49n2_117 0.9% 2 matches[51]
https://patents.google.com/patent/JP2011231205A/ja 0.9% 2 matches[52]
web.usm.my/sanggarsanjung/default.asp?tag=2009&cat=B&sesid=3&t=AS 0.9% 2 matches[53]
www.tandfonline.com/doi/citedby/10.1080/10236660903072797?scroll=top&needAccess=true 0.9% 2 matches[54]
www.ukm.my/jsm/english_journals/vol43num2_2014/vol43num2_2014p241-245.html 0.9% 2 matches
1 documents with identical matches
[58]
download.portalgaruda.org/article.php?ar...NE RUBBER BLENDS 0.7% 3 matches[60]
https://www.scribd.com/document/354830512/NR-chitosan-SBR 0.7% 3 matches[61]
www.tandfonline.com/doi/ref/10.1080/03602559.2012.671414 0.6% 2 matches13.8%
Results of plagiarism analysis from 2017-12-06 08:20 UTCThe effect of the addition of alkanolamide on properties of carbon-filled natural rubber (SMR-L) compounds cured using .pdf
[63]
https://www.sciencedirect.com/science/article/pii/S0142941810000693 0.5% 2 matches[64]
https://www.hindawi.com/journals/jpol/2013/279529/ 0.7% 2 matches[65]
material.eng.usm.my/images/Staf/Acad/cv_acad/CV_Nadras.pdf 0.7% 2 matches[66]
https://wenku.baidu.com/view/615d5069561252d380eb6ebd.html 0.6% 1 matches[67]
https://www.intechopen.com/books/elastom...from-electrospinning 0.6% 1 matches[68]
https://link.springer.com/article/10.1007/s00289-016-1746-8 0.6% 1 matches[69]
www.tandfonline.com/doi/ref/10.1080/09276440.2017.1241559?scroll=top 0.6% 3 matches[70]
https://www.sciencedirect.com/science/article/pii/S1002072110604772 0.6% 1 matches[71]
www.tandfonline.com/doi/full/10.1179/1432891715Z.0000000001468 0.5% 2 matches[73]
https://link.springer.com/content/pdf/10.1007/s40090-016-0107-7.pdf 0.4% 4 matches[74]
https://www.researchgate.net/publication...es_of_Natural_Rubber 0.3% 1 matches[75]
www.tandfonline.com/doi/full/10.1080/03602559.2012.671414?scroll=top&needAccess=true 0.4% 1 matches[76]
https://link.springer.com/article/10.1007/s10973-015-5011-4 0.4% 1 matches[77]
https://www.deepdyve.com/lp/elsevier/eff...ielectric-hAh1ot5SY8 0.4% 1 matches[78]
https://www.researchgate.net/publication...ybutadiene_Compounds 0.4% 1 matches[80]
https://www.researchgate.net/publication...mers_by_Carbon_Black 0.3% 1 matches[82]
www.tandfonline.com/doi/full/10.1080/03602559.2013.769577?src=recsys 0.3% 1 matches[83]
https://www.sciencedirect.com/science/article/pii/S0360319915017310 0.2% 2 matches[84]
https://www.scribd.com/document/15012862...al-Rubber-Composites 0.2% 1 matches[85]
https://www.deepdyve.com/lp/wiley/proper...silica-or-qQw0EP0GiY 0.2% 1 matches[86]
https://www.deepdyve.com/lp/elsevier/eff...al-rubber-mGxxNez7RC 0.2% 1 matches[89]
www.google.com/patents/US6191194 0.3% 1 matches[91]
https://www.sciencedirect.com/science/article/pii/S2351978915005600 0.2% 1 matches[92]
https://www.sciencedirect.com/science/article/pii/S0142941898000750 0.2% 1 matches[93]
https://www.researchgate.net/publication...urface_active_agents 0.2% 1 matches
1 documents with identical matches
[96]
https://www.sciencedirect.com/science/article/pii/S0143974X01000955 0.2% 1 matches0.1% 1 matches
[98]
https://link.springer.com/article/10.1007/s11244-017-0816-y 0.1% 1 matches[99]
https://www.researchgate.net/profile/Nik...n=publication_detail 0.2% 1 matches[100]
https://link.springer.com/article/10.1007/s00289-016-1812-2 0.2% 1 matches[101]
https://www.tandfonline.com/doi/full/10.1080/09276440.2017.1241559 0.2% 1 matches7 pages, 4858 words
PlagLevel: selected / overall
257 matches from 102 sources, of which 91 are online sources.
Settings
Data policy: Compare with web sources, Check against my documents, Check against my documents in the organization repository, Check against organization repository, Check against the Plagiarism Prevention Pool
--Material properties
The effect of the addition of alkanolamide on properties of carbon
black-
fi
lled natural rubber (SMR-L) compounds cured using various
curing systems
Indra Surya
a, H. Ismail
b,*aDepartment of Chemical Engineering, Engineering Faculty, University of Sumatera Utara, Medan, 20155, Sumatera Utara, Indonesia bSchool of Materials and Mineral Resources Engineering, Universiti Sains Malaysia, Engineering Campus, Nibong Tebal, 14300, Penang, Malaysia
a
i
r
n
t
f
i
o
c
l
e
Article history:
Received 25 November 2015 Accepted 12 January 2016 Available online 21 January 2016
Keywords:
The properties of carbon black (CB)- lled natural rubber (SMR-L) compounds, with and without thefi addition of Alkanolamide (ALK), based on various curing systems such as ef cient, semi-ef cient andfi fi conventional vulcanisation systems were investigated. The ALK loading was xed at 5.0 phr. It was foundfi that ALK gave improvements to the cure rate, torque difference, crosslink density, ller dispersion, rubberfi
[27]
efiller interaction and reinforcing ef ciency of CB.fi ALK also enhancedthe tensile modulus, hardness,
resilience,tensile strength and elongation at breakof CB- lled SMR-L vulcani sates for each curing sys-fi
[39]
tem. The degree of improvement ofcure characteristics and mechanical propertiesdepended on the level of sulphur andthe ratio of accelerator to sulphurin each system.Scanning electron microscopy (SEM) proved that the CB- lled SMR-L vulcanisates with ALK for each curing system displayed a greater matrixfi tearing line and surface roughness due to greater rubberefiller interaction.
©2016 Elsevier Ltd. All rights reserved.
1. Introduction
Through vulcanisation, weak and plastic raw rubbers are hard-ened or cured by sulphur and converted into strong elastic rubber vulcanisates. When vulcanisation was rst discovered, the sulphurfi
reaction with sulphur alone took several hours to be completed. Utilisation of accelerators (organic sulphur donor ingredients), with the combination of other ingredients such as zinc oxide and fatty acids, allowed the sulphur reaction to be accomplished in a shorter time and was recognised as accelerated sulphur vulcanisation [1e3]. Based on the level of sulphur and the ratio of accelerator to sulphur, accelerated sulphur vulcanisation can be classi ed intofi
three categories: ef cient (EV), semi-ef cient (semi-EV) and con-fi fi
ventional (CV) vulcanisation or curing systems.
The strength and elasticity of a rubber vulcanisate can be further enhanced by the addition of reinforcing ller. Carbon black (CB) andfi
silica are the most popular reinforcing llers for rubbers, and havefi
been widely employed in the rubber industry. CB is commonly utilised for producing black rubber products, while silica is used in coloured products. Sometimes, they are also utilised in
combination form (as hybridfiller) for the purpose of achieving their synergistic effect in order to produce better overall mechan-ical properties[4]. However, at a relatively higher loading of CB or silica, the ller particles tend to form agglomerates and will reducefi
the properties of the rubber vulcanisates. Practically, to overcome the ller dispersion problem, special additives such as processingfi
aids, dispersant aids, etc. are utilised.
In our previous work[5], the preparation and application of [73]
Alkanolamide (ALK) in silica-filled SMR-L compounds was re-ported. The ALK enhanced the tensile properties and hardness of the silica- lled SMR-L vulcanisates. The enhancement of thesefi
properties was attributed to the improvement of silica dispersion and the excelling crosslink density that stemmed from the
incor-[18]
poration of ALK.The results also indicated that ALK couldfunction as an accelerator and internal plasticiser.
The comparison of ALK and aminopropyltriethoxy Silane [41]
(APTES)-silane coupling agent on the properties ofsilica- lledfi [18]
SMR-L compounds was also reported[6].Due to its combined andunique function as an accelerator and internal plasticiser, ALK produced a higher reinforcingef ciencyfi than APTES at a similar loading.
A further study regardingthe effect of ALK loading on properties [18]
ofCB- lled SMR-L,fi epoxidised natural rubber (ENR) and styrene
*Corresponding author.
E-mail addresses:ihana @usm.myfi ,profhana @gmail.comfi (H. Ismail).
Contents lists available at ScienceDirect
Polymer Testing
j o uh ro nma ewl pw aw g. ece o:l ms e/ lv oi ec ar .t e / p o l y t e s t
http://dx.doi.org/10.1016/j.polymertesting.2016.01.014 0142-9418/©2016 Elsevier Ltd. All rights reserved.
Polymer Testing 50 (2016) 276 282e
butadiene rubber (SBR) compounds revealed that ALK gave cure enhancement, better filler dispersion and greaterrubberefiller interaction to three different types of rubbers[7]. ALK enhanced the mechanical properties, especially up to 5.0 phr of ALK in SMR-L and SBR compounds, and at 1.0 phr of ALK in ENR-25 compound.
It is important to further investigate the applicability of ALK as a new rubber additive in rubber vulcanisation. Hence, through the examination of the properties of CB- lled SMR-L compounds in thefi
presence of ALK, the applicability of ALK in vulcanisation of
CB-filled SMR-L compounds with various curing systems was stud-[39]
ied.This study focusedon the cure characteristics and mechanical properties ofCB- lled SMR-L compounds with and without ALK,fi
which were cured by EV, semi-EV and CV systems.
2. Experimental
2.1. Materials
NR grade SMR-L was used and obtained from Guthrie (M) Sdn. Bhd., Seremban, Malaysia, and N330-grade CB was supplied by the Cabot Corporation. Other compounding ingredients such as sulphur (S), zinc oxide (ZnO), stearic acid, N-isopropyl-N'-phenyl-p-phenylenediamine (IPPD), benzothiazyl disul de (MBTS) werefi
supplied by Bayer Co. (M) Sdn. Bhd.[18], Petaling Jaya, Selangor, Malaysia.The ALK was synthesised in the laboratory using Re nedfi
Bleached Deodorized Palm Stearin (RBDPS) and diethanolamine. The reaction procedures and molecular characterisations of the ALK were given in our previous report[5]. The molecular structure of ALK is presented in Fig. 1.
2.2. Compounding
The EV, semi-EV and CV vulcanisation recipes were applied in rubber compounding. The compounding procedure was performed on a two-roll mill (Model XK-160). Table 1 displays the compound formulation of CB- lled SMR-L compounds with ALK and withoutfi
ALK at various curing systems.
2.3. Cure characteristics
The cure characteristics of the CB- lled SMR-L compounds withfi
and without ALK at various curing systems were obtained using a Monsanto Moving Die Rheometer (MDR 2000), which was employed to determine the scorch time (ts2), cure time (t90) and torque difference (MHdML) according to ISO 3417.[18]Samples of the respective compounds were tested at150 C. The CB- lled SMR-L[58]
fi
compounds were subsequently compression-moulded using a stainless steel mould at150 C,with a pressure of 10 MPa, and applying a laboratory hot-press based on respective curing times.
2.4. Measurement of crosslink density
Swelling tests on the CB- lled SMR-L vulcanisates were per-fi [22]
formed in toluene in accordance with ISO 1817.The cured test pieces (30 mm5 m2 mm) were weighed using anm electric balance and swollen in toluene until equilibrium, which took 72 h
[22]
at room temperature.The samples weretaken out from the liquid,
thetoluene was removed from thesample surfaces and the weight was determined.The samples were then dried in an oven at 60 C
[22]
until constant weight was obtained.The swelling results wereused
to calculate the molecular weight betweentwo crosslinks (Mc) y b applying the Flory Rehner equatione [8].
Mc¼ volume fraction of therubberin the swollen specimen,Qmis the weight increase of thevulcanisatein toluene and
c
is the interac-tion parameter of the rubber network solvent (ec
ofSMR-[22]
L¼0.393).The crosslink density is given by;
Vc¼
1
2Mc (3)
2.5. Tensile, hardness and resilience properties
Dumbbell-shaped samples were cut from the moulded sheets. Tensile tests were performedat a cross-head speed of 500 mm/min [83]
using an Instron 3366 universal tensile machine, according to ISO 37.The tensile strength (TS), stress at 100% elongation (M100), stress at 300% elongation (M300) and elongation at break (EB) were determined. The hardness measurements of the samples were performed according to ISO 7691-I, using a Shore A type manual
[22]
durometer.The resilience was studied byusing a Wallace Dunlop [99]
Tripsometer, according toBS 903 Part A8.The rebound resilience was calculated according toEquation(4).
% Resilience¼ ð1cos½q [22]
2Þ=ð 1 cosq1Þ 100 (4)
where
q
1is the initial angleof displacement (45) andq
2is the maximum rebound angle.[96]
2.6. Scanning electron microscopy (SEM) analysis
The tensile fractured surfaces of the CB- lled SMR-L with andfi
without ALK at various curing systems were examined by using a Zeiss Supra-35VPscanning electron microscope (SEM) to obtain informationregarding thefiller dispersion, rubberefiller interac-tion and to detect the possible presence of micro-defects.The
Fig. 1.Molecular structure of Alkanolamide.
Table 1
Stearic acid 2.0 2.0 2.0
IPPD 2.0 2.0 2.0
MBTS 3.0 1.5 0.8
S 0.8 1.5 2.5
CB N330 30.0 30.0 30.0
ALK 0.0; 5.0 0.0; 5.0b 0.0; 5.0[25]
a parts per hundred parts of rubber.
b5.0 phr was the optimum loading of ALK for CB- lled SMR-L compound with a
fi semi-EV recipe[7].
fractured pieces were coated with a layer of gold to eliminate electrostatic charge build-up during analysis.
[60]
2.7. Measurement of rubberefiller interaction
The rubberefiller interactions weredetermined by swelling the curedCB- lled SMR-Lfi compounds in toluene, according to ISO1817. Test pieces with dimensions of (30 mm5 m2 mm) were m [63]
prepared from the moulded sheets. The initial weights were recorded prior to testing. The test pieces were then immersed in toluene and conditioned at room temperature in a dark environ-ment for 72 h. After the conditioning period, the weights of the swollen test pieces were recorded. The swollen test pieces were then dried in the oven at 70C for 15 min and were allowed to cool
at room temperature for another 15 min before the nal weightsfi
were recorded. The Lorenz and Park's equation [91e1 ] was applied in this study. The swelling index was calculated according to Equation(5).
Qf [84]
=Qg¼aezþb (5)
where thesubscripts f and greferredto lled and gum vulcanisates,fi [27]
respectively; z wasthe ratio by weight offiller to hydrocarbon rubber in the vulcanisate;while a and b were constants. The lower the Qf/Qg value, the greater the rubberefiller interaction becomes. In this study, the weight of the toluene uptake per gram of hy-drocarbon rubber (Q) was calculated based on Equation(6).
Q¼ Swollen½ Dried weight=½Initial weight
100=Formula weight (6)
3. Results and discussion
3.1. The cure characteristics and crosslink density
The cure characteristics of CB- lled SMR-L compounds, withfi
and without the presence of ALK at various curing systems, are shown inFigs. 2 and 3andTable 2. The addition of 5.0 phr of ALK into the CB- lled SMR-L compound for each curing system caused afi
decrease in scorch and cure times and an increase of torque dif-ference. Since amine is an ingredient of accelerators and also an accelerator activator[12], the amine part of ALK, together with ZnO and fatty acid, activated the MBTS-accelerator more pronouncedly and, consequently, improved the rate of sulphur reaction of
CB-filled SMR-L compounds. The increase of torque difference value was attributed to the additional function of ALK, as an internal
plasticiser agent, which plasticised and sof tened thefilled com-[38]
pounds.This resulted in reduced viscosity and improved process-[38] abilitydue to the CB dispersion and SMR-L CB interactione .The SMR-L CB interaction may bee de nedfi as additional physical
[38]
crosslinks[13,14]and, together with sulphide crosslinks, contrib-utedto total crosslink density[15,16] of the CB- lled SMR-L com-fi
[38]
pound.Degree of crosslink density of a rubber vulcanisate was indicated by its own torque difference value[17 20]e . The higher the torque difference value, the higher the degree of crosslink density.
It was also observed that the scorch times of CB- lled com-fi
pounds, with and without ALK, decreased when the curing system [18]
was changed from EV to Semi-EV and CV.All curing systems used MBTS asthe accelerator, and itwas functionally classi edfi as a primary accelerator which usually provides scorch delay to a
rub-[18]
ber compound [21].The lower theamountof MBTS, the lower was the scorch safety.This explained why the scorch times tended to slightly decrease when the curing system was changed through the above sequence.
When the curing system was changed from EV to Semi-EV and CV, the cure time and torque difference tended to increase. A possible explanation may be due to the effect of sulphur content of each curing system. The EV system possesses the least amount of sulphur and the CV system possesses the greatest. The higher amount of sulphur requires longer time to complete the sulphur-isation, or crosslinking reaction, hence it produces higher crosslink density. This explains why the cure time and torque difference of the CB- lled SMR-L compounds, with and without ALK, increasedfi
in sequence: EV, Semi-EV and CV.
Fig. 4 displays the crosslink density of CB- lled SMR-L com-fi
pounds, with and without the presence of ALK, for various curing systems. The crosslink density was determined by the Flor-y Rehner approach [Eq.e (1)]. The addition of 5.0 phr of ALK into the CB- lled SMR-L compounds increased the crosslink density. Thisfi
observation was in line with the data in Table 2. Torque difference
Fig. 2.Scorch times (ts2) of the CB- lled SMR-L compounds at various curing systems.fi
Fig. 3.Cure times (t90) of the CB- lled SMR-L compounds at various curing systems.fi
Table 2
Torque difference properties of the CB- lled and un lled SMR-L compounds atfi fi various curing systems.
Curing systems Loading of ALK (phr) Torque difference properties
MH, dN.m ML, dN.m MHdML, dN.m
EV 0.0 7.69 0.29 7.40
5.0 8.95 0.22 8.73
SemieEV 0.0 8.43 0.33 8.10
5.0 9.93 0.30 9.63
CV 0.0 10.55 0.20 10.35
5.0 12.64 0.19 12.45
values of CB- lled compounds with ALK were higher than those offi [100]
CB- lled compounds without ALK.fi This indicated that the crosslink density ofCB- lled compounds with ALK was higher than that offi
CB- lled compounds without ALK.fi
The crosslink density of the lled compounds with and withoutfi
ALK increased when the curing system was changed from EV to Semi-EV and CV. This was simply due to the sulphur content of each curing system. A curing system with higher sulphur content would produce a higher crosslink density[22].
3.2. The ller dispersionfi
The degree of CB dispersion in SMR-L compounds using various curing systems, due to the addition of ALK, can be quantitatively determined by Equation (7) [5 7,23,24]e .
L¼hrmr (7)
where:
h
r ¼[MLf/MLg], and mr¼[MHf/MHg];[74]where MLfand MHf werethe minimum and maximum torques of thefilled compounds, andMLgand MHgwerethe minimum and the maximum torques of the un lled/gum rubber compound.fi A lower value of L, at a particular CB loading, meant a better degree of CB dispersion. The cure characteristics of gum compounds of SMR-L using different curing systems (i.e. EV, Semi-EV and CV; MLGand MHG) were 0.05, 0.07 and 0.05 (MLG); and 4.85, 4.88 and 5.91 (MHG), respectively.Fig. 5 presents the values of L for CB dispersion in the SMR-L [39] phase, with and without ALK, using various curing systems.It can be seen that theL values of CB- lled compounds with ALK werefi lower than thoseof CB- lled compounds without ALK.fi The reduced
values of L indicated that ALK had improved the CB dispersion through its plasticisation effect in CB- lled SMR-L compounds.fi
The L values of CB- lled compounds, with and without ALK,fi
decreased from EV to Semi-EV and CV. This meant that the degrees of CB dispersion were the lowest in EV and the highest in CV. This phenomenon was also attributed to the sulphur content, since CB reacts with sulphur during the curing process and forms CB-sulphur bonds that link the rubber chains and tie thefiller onto the rubber[25]. This is rubber- ller crosslinking which is consid-fi
ered as another type of crosslink to the rubber system, and de nedfi
as coupling bonds[25,26]. The higher the sulphur content, the higher the solubility of CB in the sulphur phase, and hence the higher the degree of CB dispersion.
3.3. The rubberefiller interaction
Improved filler dispersion means greater rubberefiller in-teractions. Based on Lorenz and Park's equation (Equation(5)), the rubberefiller interaction of CB- lled SMR-L compounds at variousfi
[39]
curing systems is presented inFig. 6.It can be seen that theQf/Qg values decreasedwith the addition ofALK for all various curing systems. The decreased Qf/Qg indicated that the rubberefiller interaction in CB- lled SMR-L systems became greater, which wasfi
attributed to the capability of ALK to plasticise and soften the
CB-filled SMR-L compounds and, therefore, improving the CB dispersion.
The rubber- ller interaction of thefi filled SMR-L compounds, with and without ALK, was enhanced from EV, Semi-EV and CV. Again, this wasattributed to the sulphur content of thecuring [97]
system.The higher the sulphur content, the more pronounced the sulphur CB interaction, and hence the better the CB dispersion ande the greater the SMR-L-CB interaction.
[78]
3.4. The reinforcing ef ciency (RE)fi
The degree of reinforcement provided by the filler can be calculated through its reinforcingef ciency (fi RE), which in its simplest form, was given by Equation(8) [6].
RE¼ MHMðLÞf MHðMLÞg=ðMHMLÞg (8)
in which:
(MHML)f¼difference in torque value of lled compoundfi (MHML)g ¼ difference in torque value of un lled/gumfi compound
A higher RE value meant greater rubber- ller interaction, whichfi Fig. 4.Crosslink density of the CB- lled SMR-L compounds at various curing systems.fi
Fig. 5.The L values of CB- lled SMR-L compounds at various curing systems.fi Fig. 6.The Qf/Qg values of CB- lled SMR-L compounds at various curing systems.fi
was influenced by the degree offiller dispersion. The improved
filler dispersion provided a greater surface area for rubberefiller
interactions. RE of CB on SMR-L compounds, with and without ALK, at various curing systems is shown in Fig. 7.
As presented in Fig. 7, ALK increased the RE of CB on SMR-L compounds. This was attributed to the combined effects of better
filler dispersion and greater rubberefiller interaction.
The RE values of CB, with and without ALK, were the lowest in EV and were the highest in CV. This was due to the lowest degree of CB dispersion and the weakest rubber- ller interaction in EV, andfi
the highest degree of CB dispersion and the greatest rubber- llerfi
interaction in CV.
3.5. The mechanical properties
Table 3 showed the mechanical properties of CB- lled SMR-L,fi
with and without the addition of ALK, for various curing systems. Obviously,the tensile modulus (M100 and M300), hardness, resil-[27]
ience,tensile strength and elongation at breakwere signi cantlyfi
increased using various curing systems with the addition of ALK. Tensile modulus and hardness of a rubber vulcanisate are mainly dependent on the degree of crosslinking [27,28]. Resilience is enhanced, to some extent, as the crosslink density rises [21,29]. Hence, the enhancements of M100, M300, hardness and resilience were attributed to the enhancement of crosslink density, as dis-played inFig. 4.
The enhancement in tensile strength was attributed to a higher RE, or the combined effects of betterfiller dispersion and greater rubberefiller interaction. This explanation was in line with the results inFigs. 5 7e and the SEM micrographs later inFig. 8. The micrographs of CB- lled SMR-L vulcanisates with ALK exhibitedfi
greater matrix tearing lines and surface roughness. This indicated greater rubberefiller interaction which altered the crack paths, leading to increased resistance to crack propagation, thus causing an increase in tensile strength.
The elongations at break of CB- lled SMR-L compounds withfi
ALK were higher than those of CB- lled compounds without ALK.fi
Again, this was attributed to the function of ALK as an internal plasticiser agent which modi ed thefi flexibility of CB- lled SMR-Lfi
vulcanisates. The ALK provided a free volume which allowed more
flexibility for the SMR-L chains to move.
The mechanical properties of CB- lled SMR-L vulcanisates, withfi
and without ALK, of the CV system were the greatest due to the highest degree offiller dispersion, greatest rubber- ller interaction,fi
and hence highest RE. The mechanical properties of CB- lled SMR-Lfi
vulcanisates, with and without ALK, of the EV system were the lowest due to the lowest degree of filler dispersion, weakest rubber- ller interaction, and hence lowest RE.fi
[73]
3.6. Scanning electron microscopy (SEM) study
Fig.8 displays the SEM micrographs of fractured surfaces of the vulcanisates of CB- lled SMR-L, with and without ALK, for variousfi
curing systems, taken at 300magni cation. It can be clearlyfi
observed that the CB- lled SMR-L vulcanisates with 5.0 phr of ALKfi
for each curing system (micrographs of Fig. 8(b), (d) and (f)) exhibited greater matrix tearing lines and surface roughness compared to those of CB- lled SMR-L vulcanisates without ALKfi
(Fig. 8(a), (c) and (e)). This indicated betterfiller dispersion and greater rubberefiller interaction, and the micrographs of the tensile fractured surfaces were in good agreement with the graphs in Figs. 5 and 6, which showed the lower L and Qf/Qg values of
CB-filled SMR-L compounds with ALK. An enhancement in rupture energy, due to a greater rubberefiller interaction, was responsible for the roughness and the matrix tearing line of the fractured sur-face. The micrographs of the tensile fractured surfaces were in good agreement with the results obtained by other researchers [30,31] who reported that an increase in rupture energy was responsible for the roughness and the matrix tearing line of the fractured surfaces.
4. Conclusions
From this study, the following conclusions were drawn:
1. Alkanolamide increased the cure rate, torque difference value, crosslink density, degree of filler dispersion, rubberefiller interaction and reinforcing ef ciency of ef cient, semi-ef cientfi fi fi
and conventional curing systems of carbon black- lled naturalfi
rubber (SMR-L) compounds.
2. Alkanolamide also improved the tensile modulus, hardness, resilience, tensile strength and elongation at break of the ef -fi
cient, semi-ef cient and conventional curing systems of carbonfi
black- lled natural rubber (SMR-L) compounds.fi
3. Degree of improvement of the cure characteristics and me-chanical properties of carbon black- lled natural rubber (SMR-fi
L) compounds with Alkanolamide depended on the curing
Fig. 7.Reinforcing ef ciency of the CB- lled SMR-L compounds at various curingfi fi systems.
Table 3
The mechanical properties of CB- lled SMR-L compounds at various curing systems.fi
Curing systems Loading of ALK (phr) Mechanical properties
M100 (MPa) M300 (MPa) TS (MPa) EB (%) Hardness (Shore A) Resilience (%)
EV 0.0 1.12±0.19 4.28±0.16 23.8±0.7 880.4±19.5 48±0.4 55.1±0.5
system, especially the level of sulphur and ratio of accelerator to sulphur of each curing system.
[27]
4.Morphological studies of the tensile fractured surfaces ofcarbon black- lled natural rubber (SMR-L) vulcanisates of each curingfi
system with Alkanolamide exhibited a greater matrix tearing line and surface roughness due to greater rubberefiller interaction.
Acknowledgements
[43]
The authors would like to thankUniversiti Sains Malaysia for providing the research facilities for carrying out the experiment
[91]
and for making this research work possible. One of the authors (Indra Surya)is grateful to the Directorate Generalof Higher Edu-cation (DIKTI) Tahun Anggaran 2011, Ministry of EduEdu-cation and Culture (Kemdikbud) of the Republicof Indonesia, forthe award of a scholarship under thefifth batch of the Overseas Postgraduate Scholarship Program.
References
[1] M. Morton, Introduction to Rubber Technology, Reinhold Pub. Corp., New York, 1959.
[2] M. Morton, Rubber Technology, Van Nostrand Reinhold Company, New York, 1987.
[25]
[3] M. Akiba, A.Hashim,Vulcanization and crosslinking in elastomers, Prog. Polym. Sci. 22 (1997) 475 521e .
[22]
[4] N. Rattanasom, T. Saowapark, C.Deeprasertkul,Reinforcement of natural rubber with silica/carbon black hybridfiller, Polym.Test. 26 (2007) 369 377e . [5] I. Surya, H. Ismail, A. Azura, Alkanolamide as an accelerator, ller-dispersantfi and a plasticizer in silica- lled natural rubber compounds, Polym. Test. 32fi (2013) 1313 1321e .
[85]
[6] I. Surya, H. Ismail, A.Azura, The comparison of alkanolamide andsilane coupling agent on the properties of silica- lled natural rubberfi (SMR-L) com-pounds, Polym.Test. 40 (2014) 24 32e .
[45]
[7] I. Surya, H. Ismail, A.Azura, The effect of alkanolamide loading onproperties of carbonblack- lled natural rubber (SMR-L),fi epoxidised natural rubber (ENR), and styrene-butadiene rubber (SBR) compounds, Polym.Test. 42 (2015) 208 214e .
[8] P.J. Flory, J. Rehner Jr., Statistical mechanics of crosslinked polymer networks II. Swelling, J. Chem. Phys. 11 (1943) 521.
[69]
[9] O. Lorenz, C.Parks, The crosslinking ef ciencyfi of some vulcanizing agents in natural rubber, J.Polym. Sci. 50 (1961) 299 312e .
[10] H. Ismail, M. Nasaruddin, U. Ishiaku, White rice husk ash lled natural rubberfi compounds: the effect of multifunctional additive and silane coupling agents, Polym. Test. 18 (1999) 287 298e .
[41]
[11] H. Ismail, S. Shaari, N.Othman, The effect of chitosan loading on the curing characteristics, mechanical and morphological properties ofchitosan- lledfi natural rubber (NR), epoxidised natural rubber (ENR) and styrene-butadiene rubber (SBR) compounds, Polym.Test. 30 (2011) 784 790e .
[12] H. Long, Basic Compounding and Processing of Rubber, Rubber Division, American Chemical Society Inc. The University of Akron, Ohio, USA, 1985. [13] B. Boonstra, G. Taylor, Swelling offilled rubber vulcanizates, Rubber Chem.
Technol. 38 (1965) 943 960e .
[92]
[14] R. Nunes, J. Fonseca, M.Pereira, Polymere fi llerinteractions and mechanical properties of a polyurethane elastomer, Polym.Test. 19 (2000) 93e103. [15] G. Kraus, Reinforcement of Elastomers, John Wiley&Sons Inc., New York,
1965.
[89]
[16] K. Polmanteer, C.Lentz,Reinforcement studies-effect of silica structure on properties and crosslink density, Rubber Chem.Technol. 48 (1975) 795 809e .
[69]
[17] B. Boonstra, H. Cochrane, E.Dannenberg,Reinforcement of silicone rubber by particulate silica, Rubber Chem.Technol. 48 (1975) 558 576e .
[18] H. Cochrane, C. Lin, The in uence of fumed silica properties on the processing,fl curing, and reinforcement properties of silicone rubber, Rubber Chem. Tech-nol. 66 (1993) 48 60e .
[19] H. Ismail, C. Ng, Palm oil fatty acid additives (POFA's): preparation and application, J. Elastom. Plast. 30 (1998) 308 327e .
[25]
[20] P. Teh, Z. Mohd Ishak, A. Hashim, J. Karger-Kocsis, U.Ishiaku,Effects of epoxidized natural rubber as a compatibilizer in melt compounded natural rubber organoclay nanocomposites, Eur.e Polym. J. 40 (2004) 2513 2521e . [21] B. Rodgers, Rubber Compounding: Chemistry and Applications, CRC, New
York, 2004.
[22] H. Ismail, I. Salmiah, Y. Tsukahara, Palm oil fatty acid as an activator in carbon black lled natural rubber compounds: effect of vulcanization system, Polym.fi Int. 44 (1997) 523 529e .
[66]
[23] B.Lee,Reinforcement of uncured and cured rubber composites and its rela-tionshipto dispersive mixing-an interpretation of cure meter rheographs of carbon black loaded SBR and cis-polybutadiene compounds, Rubber Chem. Technol. 52 (1979) 1019 1029e .
[24] P. Pal, S. De, Effect of reinforcing silica on vulcanization, network structure, and technical properties of natural rubber, Rubber Chem. Technol. 55 (1982) 1370 1388e .
[25] M.Q. Fetterman, The unique properties of precipitated silica in the design of high performance rubber, Elastomerics 116 (1984) 18 31e .
[26] M. Fetterman, Precipitated silica coming of age, Rubber World 194 (1986)e Fig. 8.SEM micrographs of the failed fracture of CB- lled SMR-L vulcanisate at a magni cation of 300 ; (a) 0.0 phr ALK (EV), (b) 5.0 phr ALK (EV), (c) 0.0 phr ALK (semi-EV), (d)fi fi d d d 5.0 phr ALK (semi-EV), (e) 0.0 phr ALK (CV), (f) 5.0 phr ALK (CV).d d d
38 40e .
[27] D.L. Hertz Jr., S.E. INC, Theory&practice of vulcanization, Elastomerics (November 1984) 1 7e.
[25]
[28] H. Ismail, H.Chia,The effects of multifunctional additive and epoxidation in silica lledfi natural rubber compounds, Polym.Test. 17 (1998) 199 210e . [29] W. Hofmann, F. Bayer, Vulcanization and vulcanizing agents, Maclaren (1967)
143 147e .
[28]
[30] H. Ismail, M. Mathialagan, Comparative study on the effect of partial replacement of silica or calcium carbonate by bentonite on the properties of EPDM composites, Polym.Test. 31 (2012) 199 208e .
[28]
[31] H. Nabil, H. Ismail, A.Azura,Compounding, mechanical and morphological properties ofcarbon-black- lledfi natural rubber/recycled ethylene-propylene-diene-monomer (NR/R-EPDM) blends, Polym.Test. 32 (2013) 385 393e .
