All sources 61 Internet sources 38
[8] www.tandfonline.com/doi/pdf/10.1080/03602550802539155?needAccess=true 3.2% 12 matches
[12] www.tandfonline.com/doi/pdf/10.1081/PTE-200065172?needAccess=true 3.0% 14 matches
[14] https://vdocuments.site/properties-of-hv...erthermoplastic.html 2.3% 11 matches
[17] journals.sagepub.com/doi/pdf/10.1177/0095244305046487 1.6% 7 matches
[20] www.refdoc.fr/Detailnotice?cpsidt=16437065 1.3% 9 matches
[21] masshp.net/journal/all journal/2005/23 hanafi ismail 184-194.pdf 1.4% 7 matches
[23] core.ac.uk/display/15403493 1.4% 5 matches
[24] https://bioresources.cnr.ncsu.edu/BioRes..._Composites_3178.pdf 0.9% 5 matches
[28] https://www.researchgate.net/publication...NR_Vulcanized_Blends 1.2% 3 matches
[30] iom3.tandfonline.com/doi/full/10.1080/03602550500210067 0.8% 5 matches
[32] www.tandfonline.com/doi/figure/10.1080/03602550802539155 1.1% 2 matches
[33]
www.scirp.org/reference/ReferencesPapers.aspx?ReferenceID=466944 1.2% 5 matches
1 documents with identical matches
[35] onlinelibrary.wiley.com/doi/10.1002/app.1994.070540602/full 1.2% 5 matches
[38] https://www.science.gov/topicpages/h/hydroliquefaction solvent-induced scission.html 0.5% 3 matches
[39] onlinelibrary.wiley.com/doi/10.1002/app.1994.070540603/full?scrollTo=references 1.0% 4 matches
[40] onlinelibrary.wiley.com/doi/10.1002/vnl.20277/full?scrollTo=footer-citing 0.7% 2 matches
[41] https://www.researchgate.net/publication...s_of_PPEPDMNR_blends 0.4% 4 matches
[42] www.tandfonline.com/doi/full/10.1080/03602550500373675?scroll=top&needAccess=true 0.5% 2 matches
[43] https://www.science.gov/topicpages/d/dehydrogenation.html 0.3% 3 matches
[44] www.tandfonline.com/doi/pdf/10.1080/03602550802539270 0.5% 3 matches
[45] www.tandfonline.com/doi/pdf/10.1080/00914030500306461?needAccess=true 0.3% 2 matches
[46] journals.sagepub.com/doi/pdf/10.1177/0731684406055454 0.4% 2 matches
[47] masshp.net/journal/all journal/2005/23 ABS hanafi ismail 184-194.pdf 0.3% 2 matches
[48] www.tandfonline.com/doi/pdf/10.1080/03602550701575920 0.3% 2 matches
[49] www.scielo.br/scielo.php?script=sci_arttext&pid=S0104-14282015000400382&lng=en 0.3% 3 matches
[50] https://www.science.gov/topicpages/a/amk blending testing.html 0.3% 2 matches
15.6%
Results of plagiarism analysis from 2017-12-06 05:18 UTCProperties of Polypropylene PP Ethylene Propylene Diene Terpolymer EPDM Natural Rubber NR Vulcanized Blends The Effect.pdf
[51]
www.tandfonline.com/doi/figure/10.1081/PTE-200065172 0.4% 1 matches
1 documents with identical matches
[53] https://link.springer.com/content/pdf/10.1007/s13726-014-0223-1.pdf 0.3% 1 matches
[54] https://www.sciencedirect.com/science/article/pii/S2351978915000128 0.3% 2 matches
[55] https://www.sciencedirect.com/science/article/pii/S0142941801001015 0.3% 1 matches
[56] https://patents.google.com/patent/US20160039980A1/en 0.3% 2 matches
[59] https://books.google.co.uk/patents/US5021500 0.2% 2 matches
[60]
cat.inist.fr/?aModele=exportN&cpsidt=16437065 0.3% 1 matches
1 documents with identical matches
[62]
https://www.researchgate.net/publication...DM-NR_ternary_blends 0.2% 1 matches
1 documents with identical matches
[64] https://www.sciencedirect.com/science/article/pii/S0969806X05000095 0.2% 1 matches
[65] https://link.springer.com/article/10.1023/A:1010144205297 0.2% 1 matches
[66] https://www.researchgate.net/publication...ffect_of_blend_ratio 0.2% 1 matches
[67] https://www.sciencedirect.com/science/article/pii/S0141391098000809 0.2% 1 matches
10 pages, 5294 words
PlagLevel: selected / overall
188 matches from 68 sources, of which 52 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
--Full Terms & Conditions of access and use can be found at http://www.tandfonline.com/action/journalInformation?journalCode=lpte20
Download by: [National Cheng Kung University] Date: 29 August 2016, At: 01:[33]10
Polymer-Plastics Technology and Engineering
ISSN: 0360-2559 (Print) 1525-6111 (Online) Journal homepage: http://www.tandfonline.[28]com/loi/lpte20
Properties of Polypropylene (PP
)/Ethylene-Propylene
Diene Terpolymer (EPDM)/Natural
Rubber (NR) Vulcanized Blends
:
The Effect of
N,N-m-Phenylenebismaleimide (HVA-2) Addition
Halimatuddahliana & H. Ismail
To cite this article: Halimatuddahliana & H.[28] Ismail (2008) Properties of Polypropylene (PP)/ Ethylene-Propylene Diene Terpolymer (EPDM)/Natural Rubber (NR) Vulcanized Blends[33]: The Effect of N,N-m-Phenylenebismaleimide (HVA-2) Addition, Polymer-Plastics Technology and Engineering, 48:1, 25-33, DOI: 10.1080/03602550802539155
To link to this article: http://dx.doi.org/10.1080/03602550802539155
Published online: 17 Dec 2008.
Submit your article to this journal
Article views: 66
View related articles
Properties
of Polypropylene
(PP)/Ethylene-Propylene
Diene
Terpolymer
(EPDM)/Natural
Rubber
(NR) Vulcanized
Blends:
The Effect
of
N
,
N
-
m
-Phenylenebismaleimide
(HVA-2)
Addition
[33]
Halimatuddahliana
1and H. Ismail
[32] 21Department of Chemical Engineering, Universitas Sumatera Utara, Indonesia 2School of Materials and Mineral Resources Engineering, Universiti Sains Malaysia,
Penang, Malaysia
This paper discusses process development, tensile properties, morphology, oil resistance, gel content, and thermal properties of polypropylene (PP)/ethylene-propylene diene terpolymer (EPDM)/ natural rubber (NR) vulcanized blends with the addition of N,N-m-phenylenebismaleimide (HVA-2) as acompatibilizer.Blends were prepared in several blend ratios in a Haake Polydrive with tempera-ture and rotor speed of 180C and 50 rpm, respectively. Results indi-cated that the combination of dicumyl peroxide (Dicup) with HVA-2 shows high torque development and stabilization torque as
[23]
compared to the blend with Dicup vulcanization alone.In terms of tensile properties, the combination of Dicup with HVA-2 shows higher tensile strength, tensile modulus (M100), elongation at break,
oil resistance, and gel contentin all blend ratios compared to similar
[23] vulcanized blends with Dicup without HVA-2 addition. Scanning electron microscope (SEM) micrographsof the blends support that the cross-linking and compatibilizationoccur during the process of
[20]
thevulcanized blend containing HVA-2. In the case of crystallinity of the blends,the addition of HVA-2 in Dicup vulcanized blend revealed a tendency for the percentage of crystallinity (Xc) to
[8]
decrease.The addition of HVA-2 in Dicup vulcanizationalso pro-duced blends with good thermal stability dealing with the so-called coagent bridge formation.
Keywords Crystallinity; Dicup; EPDM; HVA-2; Natural rubber; Polypropylene; Thermal stability
INTRODUCTION
There are large combinations of thermoplastics and elastomers that are commercially available. The PP=
EPDM blends are the most commonly used types of blends. However, replacement of EPDM with NR in the PP EPDM blends has been considered due to the=
reduction of the cost. It has also been observed that the partial replacement of EPDM by NR exhibits lower properties of PP EPDM blends= [1][12]
. Therefore, dynamic
vulcanization has been introduced in the PP EPDM NR= =
blend to improve the properties of such blends. Some investigations have been reported regarding the dynamic vulcanization of thermoplastic elastomer, especially on PP EPDM blends, and most of the investigations focused=
on the processing and the improvements on mechanical and physical properties of the blends[2–7]. Dynamic vulcani-zation has also been introduced in the PP EPDM NR= =
blend using sulfur[8] and dicumyl peroxide (Dicup)[9][12]to improve the properties ofsuch blends.
The presence of Dicup in the blends is to produce [12]
reactive radicals upon decomposition at elevated tempera-turevia exothermic reaction that is beneficial in a rubber compound.It is generally agreed that for the peroxide vul-canization of polyolefin and rubber, cross-links or chain scission may occur simultaneously. According to Ho et al.[10]the polymer free radicals in PP induced by the peroxide decomposition lead to predominantly scission reaction, whereas in rubber, vulcanized properties of blends are determined by cross-link structures that form[11,12].
Coagents, in the other hand, can be used to compou nd [8]
elastomers, thermoplastics, and thermop lastic elastomer= blends with and without the presence of accelerators or
[8]
peroxide.Investigatons have been reported regarding the use of coagent, especially HVA-2 and accelerators[13–15]. The addition of HVA-2 for peroxide cure is to eliminate [8]
practically all of the problems once con sidered to be asso-ciated with peroxide cu re.According to Dikland et al.[16] and McElwee and Lohr[17], peroxide-coagent system can be visualized in a way similar to that which was postulated for the sulfurization of the rubber molecules by the action of accelerators. After decomposition of peroxide mole-cules, macroradicals are formed and subsequently the coagent incorporation process is expected to initiate by the vulcanization system. The polyfunctional molecules in coagent can also be incorporated into the cross-link [40]
Address correspondence to H.Ismail,School of Materials and Mineral Resources Engineering, Universiti Sains Malaysia, 14300 Nibong Tebal, Penang, Malaysia.E-mail: hanafi@eng.usm.my
Polymer-Plastics Technology and Engineering, 48: 25–33, 2009 Copyright#Taylor & Francis Group, LLC
ISSN: 0360-2559 print/1525-6111 online DOI: 10.1080/03602550802539155
structures during vulcanization, forming a so-called coagent bridge.
Keller[18]has suggested briefly that the process initiates
viathermal decompostition of the peroxide and how the coagent affects the reaction. A generalized scheme is shown as foll ows:
ð Þ1 Peroxide! heat2R Peroxide decomposition
ð Þ2 R!þP PþRH H abstraction
ð Þ3 2P!PP Cross-link
ð Þ4 P!þR PR No cross-link
ð Þ5 P!P0þP¼ Scission
The cross-link is completed when the polymer radicals combine as in Reaction (3). If a coagent is present in the compound, Reactions (4) and (5) are repressed because the coagent rapidly combines with P to produce stable radicals. The polyfunctional nature of the coagent
[42]
also enhances Reaction (2). In addition, the presence of a reactive olefinic site as in the terpolymer shifts Reac-tion (2) from the polymer backbone to thependant unsa-turation, thus intensifying Reaction (3) and suppressing Reaction (5).
A previous paper[19][8]reported that in terms of tensile properties and degree of cross-linking, the presence of HVA-2 in Dicup vulcanization significantly affects the extent of recombination ofmacroradical s (from chain scis-sion)and improves the cross-lininghe atefficiency, which can be attributed to the formation of coagent bridge in
[38]
PP EPDM NR blends= = . It was concluded that the sup-pression of chain scission and the formation ofcoagent bridges contributes to an improvement of the cross-linking
[32]
efficiency.This paper discussesthe role of HVA-2 in Dicup vulcanization of PP EPDM NR blends and how it can= = influence theprocess development, tensile properties, mor-phology,oil resistance, gel content, and thermal properties ofPP EPDM NR blends.= =
EXPERIMENTAL
[21]
Materials
Polypropylene (PP) homopolymer used in this study was an injection-molding grade, supplied by Titan PP Polymers (M) Sdn Bhd, Johor, Malaysia (TITANPRO 6331 grade), with a melt flow index (MFI) value of 14 gr 10 min at= 230C and 2.16 kg.[44]Ethylene-propylene diene terpolymer (EPDM-EPT 3072E), with Mooney Viscosity ML (1þ4) at 100C of 74 was purchased from Luxchem Trading Sdn. Bhd. Natur al rubber (NR-HSL) with Mooney vis-cosity ML (1þ4) at 100C of 73 was obtained from Hokson Rubber Trading Sdn. Bhd, Seremban. Dicumyl peroxide
[53]
(Dicup) was purchased from Aldrich. The coagent used for the blend was N,N-m-phenylenebismaleimide
(HVA-2), a free radical cross-linking agent from DuPont DowElastomer.
Preparation and Processing [12]
Studies were conducted on PP EPDM NR blends= = con-sisting of two systems viz.blend with Dicup vulcanization and blend with the combination of Dicup vulcanization and HVA-2, where each blend covered diff erent blend compositions viz. 50 40 10,= = 50 30 20,= = 50 20 30,= =
50 10 40, and 50 0 50. Blends were prepared by melt mix-= = = =
ing in an internal mixer, Haake Polydrive with Rheomix R600 610, at temperature and rotor speed of 180= C and 50 rpm, respectively. Table 1 shows the mixing sequence of components in preparation of the PP EPDM NR= =
[8]
blends. During blending, thermoplastics (PP) were first loaded into the internal mixer and pre-mixed for2 min
fol-[8]
lowedby the rubbers (EPDM and NR).Mixing times were determined based on the recorded torque at stable value confirming the homogeneous mixing of the blends. For the dynamic vulcanization process, Dicup was added at 5 min of mixing and the mixin g time was set for 8 min. The corresponding blends with combination of Dicup and HVA- 2 had mixing time further increased to 10 min. The samples were then sheeted by passing through a 2 roll-mill and allowed to cool at room temperature.
Tensile Properties [12]
Tensile tests were carried out according to ASTM D412 [55]
on an Instron machine; 2-mm thick dumbbell specimens were cut from the molded sheets with a Wallace die cutter.
TABLE 1
Mixing sequence of components in preparation of the PP EPDM NR blends= =
0 PP loading PP loading
2 Rubbers addition Rubbers addition
5 DCP addition
þantioxidanta DCP and HVA-2addition
þantioxidanta
aIrganox 1010 (0.4 phr).
bBased on the rubbers content (EPDM and NR). cBased on the NR content.
The specimen was tested using a constant rate (50 mm=
min) at room temperature of 25C.[17]The results were quoted based on the average value of five specimens tested for each blendsyst em.
Morphology Studies [12]
Morphological evaluations of PP EPDM NR surfaces= = were done using ascanning electron microscope (SEM), model Stereoscan 200 Cambridge.The vulcanized samples were etched with nitric acid for 2 days, washed with water,
[8]
and then dried. All the samples were mounted on alumi-numstubs and sputter-coated with a thin layer of gold to
[8] avoid electrostatic charging during examination. The examinations were done within24 h of preparation.
Swelling Test [8]
Determination of the swelling index was carried out according to ASTM D471.The specimens with dimensions of 30 mm5 mm2 mm were cut and weighed using an electrical balance. The test pieces were then immersed in oil (IRM 903) for 48 h at room temperature. The samples were then removed from oil, wiped with tissue paper to remove excess liquid from the surface, and weighed. The swelling index of the blends was then calculated as follow:
Swelling index¼
[54] W2
W1
100% ð Þ1
WhereW1andW2are weight ofspecimenbefore and after
immersion, respectively.
Gel Content
The degree of cross-linking in the rubber was measured after extraction in boiling cyclohexane for 8 h. The samples were dried at 80C for 30 min and subsequently weighed. The percentage of gel content of the blends was then calcu-lated as follows:
% gel content¼
[44] Wg
Wo100% ð Þ2
Where Wg and W0are sample weights after and before extraction, respectively.
Differential Scanning Calorimetry (DSC) Study [44]
Thermal analysis measurements of selected blend sys-tems were performed using a DSC-7 Perkin Elmer
differen-[17]
tial scanning calorimeter.The samples were programmed and heated at 20C min to about 200= C and maintained at this temperature for 10 min to ensure acomplete melting
[17]
of the crystals.The melting temperature(Tm)and the heat of fusion( Hf)D were measured during the heating cycle. The parameter percentage of crystallinit y (Xc) was calcu-lated by dividing the measuredDHf by theDHf of 100%
polypropylene. The DHf for polypropylene as a fully crystalline material is 209 J g= [20].
Thermogravimetric Analysis (TGA)
[17]
Thermogravimetric analysis of the blends was carried out using a Perkin Elmer Pyris 6 TGA analyzer at tempera-tures be tween 30 and 600C at nitrogen airflow of 50 ml=min and a heating rate of 20C min= .
Ageing Test
[17]
The ageing test was done according to ASTM D573. Dumbbell specimen s were hung in an air oven at the [17]
temperature of 100C for72 h.At the end of the test period, the specimens were removed from the oven, cooled at room temperature, and allowed to rest for at least 16 h before
[12]
determination of tensile properties.Retention in properties was calculated as
Properties retention %ð Þ A O= ¼100% ð Þ3
Where Ais the value after ageing, andOis the original value.
RESULTS AND DISCUSS ION
[12]
Process Development
The torque developments of selected Dicup vulcaniza-tionof PP EPDM NR blends= = with and without HVA-2 addition are shown in Fig.1. A sharp increase in the torque value was observed immediately after the addition of Dicup and HVA-2 after five min. Upon the completion of mixing, the torque starts to decrease gradually due to a decrease in the viscosity to more stable values. For the Dicup vulcanized blends containing HVA-2, the torques stabilizes at a higher value than Dicup vulcanized blend without HVA-2. The increase of torque is associated with the interruption exerted on the rotor by the extended cross-linking on deformability of macromolecules. This indicates that the viscosity of the blend increases as cross-linking took place. Besides cross-link formation, the pres-ence of HVA-2 in the Dicup vulcanization blend is also related to an increasing adhesion between the dispersed phase and the matrix. According to Dahlan et al.[21], the highest torque indicates the strongest interaction between the phases of the blend. In this case, the increase in adhesion can be explained by a radical-induced cross-linking by HVA-2. As mentioned before, in the presence of peroxide in the blends, chain scissions become the domi-nant reaction for PP. However, when a multifunctional monomer (such as HVA-2) is used as a coagent, the rate of chain scission reactions will be reduced because of stabilization of macroradicals[16,18]. Therefore, cross-link reactions are favored and also lead to the formation of coagent bridges betw een rubber and plastic.
The comparison of stabilization torque values between Dicup vulcanized blend with HVA-2 and vulcanized blend without HVA-2 are presented as a function of blend com-positions in Fig. 2. It shows that the Dicup vulcanized blend with HVA-2 exhibi ts higher stabilization torque compared with the Dicup vulcanized blend only. In this case, the extended cross-linking and inhibition of chain scission by HVA-2 led to an increase in viscosity of the blend and hence the torque. With the addition of HVA-2 in Dicup vulcanization, even though the radicals are formed by peroxide, the coagent is sufficient to bridge and stabilize the PP macroradicals. As the coagent was added, a dramat ic increase of melt viscosity was obtained. This implies that macroradicals formed by peroxide are
[66]
mostly reacted with HVA-2.Furthermore,the stabilization torque increases with the increase ofNR content.This indi-cates that the effect of HVA-2 on the Dicup vulcanized blend was more significant than on the NR richer blend.
Tensile Properties
The effect of Dicup vulcanization combined with HVA-2 addition on tensile strength of PP EPDM NR blends as= =
compared with the Dicup vulcanized blend alone is presented in Fig. 3. The tensile strength of PP EPDM NR= =
NR blends registers a marked improvement with the com-bination of Dicup and HVA-2. Here, the cross-link becomes more pronounced in the blend with the combi-nation of Dicup and HVA-2 as indicated in Fig. 3. The data demonstrates that the Dicup vulcanized of 50 0 50= =
PP EPDM NR blend gave the highest value in tensile= =
strength, 13.5 MPa to 18.2 MPa, which is about a 35%
[14]
increase.This can be attributed to theextensive cross-link formation in the vulcanized blends by the addition of HVA-2.The increase of the cross-linking efficiency in the presence of coagents in the peroxide vulcanization was also reported by Dikland et al.[16][12]. As mention ed before, the coagent affecting molecular structure of the cross-links where the coagent molecules can be incorporatedinto the cross-link structure during vulcanization of rubber forming is a so-called coagent bridge. The suggested reaction sequence of cross-linking in rubber phase due to the com-bination of Dicup and HVA-2 is shown in Fig. 4. In addition, the presence of coagent molec ules in Dicup vulca-nization have also suppressed unwanted side reactions, such as chain scission of PP[16]. So, the previous obser-vation suggested that the HVA-2 in Dicup vulcanization acted as an effective compatibilizer to increase the adhesion between the phases due to production of a coagent bridge. The increased interfacial adhesion, which facilitates the stress transfer mechanism within the blend, is also expected, and hence the improvement of tensile stren gth occurred.
The introduction of HVA-2 on the Dicup vulcanization [24]
blend has also slightlyincreased the tensile modulus of the blends, as can be seen in Fig. 5. The Dicup vulcanized (50 0 50) blend containing HVA-2 generated the highest= =
tensile modulus (M100) of 10.3 MPa, increasing 7.3%from the blend without HVA-2 addition (9.5 MPa). Here again, the formation of extensive cross-linking and compatibiliza-tion improved the stiffness of the blend. This finding was
FIG. 1. The torque development of Dicup vulcanization of PP= EPDM NR blends with and without HVA-2 addition.=
FIG. 2. The comparison of stabilization torque between Dicup vulcanization with and without HVA-2 addition.
[30]
FIG. 3. The effect ofDicup vulcanizationþHVA-2 addition ontensile strengthof PP EPDM NR blends.= =
[38]
due to the formation of the interfacial cross-linking via formation of acoagent bridge.
Figure 6 shows the comparison ofelongation at break of [14]
Dicup vulcanized blends with and without HVA-2 [14]
addition.It can be seen that the elongation at break of the vulcanizedblend containing HVA-2 is higher than that without HVA-2 for each blend composition.This is clearly due to the inherent ductility as a result of the presence of a coagent bridge, which increases the deformability of the
molecules. In addition, the improvement of elongation at break may also be caused by the restriction of the chain scission by the addition of HVA-2. The intr oduction of HVA-2 in Dicup vulcanization results in the recombination and functionalization of macroradicals competing with the degradation of tertiary alkyl radicals of PP. This indicates that the cross-linking predominates over chain scission, resulting in greater resistance at break. Further, the addition of HVA-2 in Dicup vulcanized blend has
FIG. 4. Reaction sequence of crosslinking in rubber phase by peroxide and HVA-2[11].
FIG. 5. The effect of Dicup vulcanizationþHVA-2 addition on tensile modulus (M100) f P=EPDM NR blends.o=P
FIG. 6. The effect of Dicup vulcanizationþHVA-2 addition on elonga-tion at break of PP EPDM NR blends.= =
improved interfacial adhesion between phases due to the low interfacial tension leading to better and finer disper-sion and reduction in the dispersed size as will be discussed in the following section.
Morphology Study
[20]
Figures 7a–d compares the extracted surface morpholo-gies of Dicup vulcanized PP EPDM NR= = blends with and
[20]
without HVA-2 addition. Through the addition of HVA-2 invulcanized blends (Figs.7b and d), the particles are smaller, better dispersed, and more evenly distributed in the PP matrix as compared to Dicup vulcanized blends alone (Figs. 7a and c). It is apparent from the micr ographs that the numbers of holes due to the extraction of rubber particles are reduced significantly. This observation indicates that the combination of Dicup vulcanization with HVA-2 has cross-linked the rubber phase and increased interfacial adhesion resulting from the formation of the coagent bridge. After the cross-linking of the rubber particles, the tendency of the rubber particles to dissolve by the solvent decrease.
Although a detailed distribution analysis on the [8]
dispersed particles was not carried out in this work, the decrease of the dimens ion and number of voids could be explained by the production of coagent bridge between PP and rubberin PP EPDM NR blends= = under dynamic cross-linking conditions. The same observation was obtained by Wu[22], who indicated that if the graft
copolymer of plastic and rubber was produced predomi-nantly at an early stage in the dynamic cross-linked pro-cess, it would play a role of compat ibilizer to reduce the dimension and number of the particles dramatically. There-fore, this morphology shows evidence for the improvement of the properties of Dicup vulcanized blend with HVA-2.
Swelling Index
The result of oil resistance of Dicup vulcanized blend with and without HVA-2 addition based on the swelling index after oil immersion at room temperature for 48 h is presented in Table 2. It is obvious that the oil resistance increased for Dicup vulcanized blend containing HVA-2 as indicated by the low values of swelling index compared to Dicup vulcanized blend alone. The magnitude of decrease in swelling index of the blend increases with increasing NR content. The higher magnitude changes are observed in the Dicup vulcani zed 50 0 50= =
PP EPDM NR blend as shown in Table 2. This indicates= =
that cross-li nk formation in NR richer content is more pre-dominant. These values represent tight cross-linking of the rubber chains, therefore less oil penetrated into the rubber particles.
Gel Content
[20]
The effect of HVA-2 addition on theDicup vulcaniza-tion on the percentage ofgel content of PP EPDM NR= = blend is depicted in Table 3.The amount of gel content determined after Soxhlet extraction of uncross-linked rub-ber phase is in agreement with those determined from swelling index. Gel is formed when a strong interaction between components of the blend exists. It is an indicator of cross-links and compatibilization formed in the blend. Upon addition of HVA-2 in the Dicup vulcanized blend,
[38]
there is an increase in percentage of gel. This is again associated with the increase ofcross-lin k efficiencydue to the formation of acoagent bridge by HVA-2.
FIG. 7. SEM micrographs of extracted surface PP EPDM NR= = blends: (a) Dicup vulcanized 50 30 20, (b) Dicup vulcanized 50 30= = = = 20þHVA-2, (c) Dicup vulcanized 50 0 50, and (d) Dicup vulcanized= = 50 0 50= = þHVA-2.
TABLE 2
Comparison of the swelling index between dicup vulcanized PP EPDM NR blends with and without= =
HVA-2 addition
Thermal Analysis
Differential Scanning Calorimetry (DSC)
Figure 8 presents the DSC scan of Dicup vulcanized blends with and without addition of HVA-2 for two dif-ferent blend compositions of PP EPDM NR blends.= =
The DSC outputs show characteristics corresponding to the PP phase, where it is mostly governed by crystall ine PP alone. This is because rubber is an amorphous poly-mer[23]. However, in the Dicup vulcanized 50=30=20 PP EPDM NR blend with HVA-2, a small peak in the= =
shoulder of the endothermic peak is observed, implying that the shape of the melting endothermic was modified by HVA-2 addition. As can be seen, the sharp endo-thermic peak of Dicup vulcanized 50 30 20 PP EPDM= = = =
NR blend without HVA-2 was broadened with HVA-2. This indicates that the chain scission of PP in EPDM [43] molecule was limited by the addition of HVA-2. In addition, the small shoulder in the 50 30 20 PP EPDM= = = = NR endothermic peakmay be related to the formation of a newcrystal and change in crystal structure by HVA-2. However, this peak disappeared in the 50 0 50 PP= = =
EPDM NR blend.=
The detailed thermal properties of such blends derived from DSC scan thermograms are tabulated in Table 4.
The PP melting peak (T ) of Dicup vulcanized blend ism
shifted toward higher temperatures by the presence of HVA-2, indicating an effective cross-linking of the rubbers. Theoretically, in the thermodynamic sense, the chain scis-sion reactions cause a decrease in the melting temperature by increasing the melt entropy[24]. In this case, melting tem-perature (T ) can be affected by the effect of scission andm
cross-linking of PP molecules. Therefore, these results con-firm that the cross-linking was predominant over the chain scission.
The analysis of the DSC traces further reveal that the presence of HVA-2 in Dicup vulcanization has a significant nucleating effect on the blend. The coagent bridge on the PP rubber interface can improve the phase adhesion, cre-=
ating additional links between the phases that may contrib-ute to a more effective transmission of stress. However, as can be seen in Table 4, the percentage of crystallinity of the Dicup vulcanized blend decreases with the addition of HVA-2. A cross- linked structure produced under dynamic vulcanization may restrict the spherulitic growth and hence decrease the degree of crystallinity of PP[25]. Here, the reduction of pe rcentage of crystallinity, which leads to the increase of network, was due to the extended cross-linking by HVA-2. Furthermore, the incorporation of the coagent bridge between the phases might cause the restric-tion of the mobility of the PP segment, leading to the lack alignment in the crystal lattice , thus reducing percen tage of crystallinity.
Thermogravimetric Analysis
Thermograms of Dicup vulcanized PP EPDM NR= =
blends with and without HVA-2 addition are shown in Fig. 9. It can be observed that a slower degradation of the Dicup vulcanized blend containing HVA-2 over the Dicup vulcanized blend alone took place. Here, the degradation temperatures of the Dicup vulcanized blends containing HVA-2 were shifted to slightly higher TABLE 3
Gel content of selected cicup vulcanized PP EPD M NR= =
blend with and without HVA-2 addition Gel content ( )%
FIG. 8. The effect of Dicup vulcanizationþHVA-2 addition on DSC scansof PP EPDM NR blends.= =
TABLE 4
Thermal properties of selected dicup vulcanized PP EPDM NR blends containing HVA-2 derived from= =
DSC scan thermogram as compared without HVA-2
PP EPDM NR= =
Dicup vulcanized blendþHVA-2
50 30 20= = 161.6 34.9 16.7
50 0 50= = 160.3 35.8 17.12
[56]
temperature.This is due to the presence ofHVA-2, which formed a coagent bridge during processing that hinders easy transport of thermal energy acrossthe material during heating and subsequently protects the blend from degra-dation.This can slow down the formation of degradation
[14]
products.The initial decomposition temperatureincreased with the addition of HVA-2, whichis due to the predomi-nanteffect of HVA-2in NR.
The effect of HVA-2 addition on thethermal stability of [30]
Dicup vulcanized PP EPDM NR blends= = is depicted in Fig.10. It is clear that the percentage of weight loss of the Dicup vulcanized blends containing HVA-2 at any tem-perature is lower than those of the blend without HVA-2. This is observed from the curves, where the Dicup vulca-nized blends co ntaining HV A-2 lie above the blends with-out HVA-2 for every percentage of weight loss (20 to 90%). Here, HVA-2 brings out stability in the phase due to the introduction of cross-links as well as formation of intramolecular cross-linking (coagent bridge)[16]. This could also be understood by SEM analysis, where the mor-phology of the vulcanized blend containing HVA-2 shows
more stable morphology, which is responsible for enhanc-ing the thermal stability of the systems. Therefore, it is observed that when compared with the Dicup vulcanized blend alone, Dicup vulcanization combined with HVA-2 system demonstrated better thermal stability.
Heat Resistance
The percentage of retention of tensile strength and elon-gation at break of blends after hot air ageing for 72 h (100C) is shown in Table 5.[14]The deteriorationof the tensile properties of theDicup vulcanized blend containing HVA-2 after ageing has been monitored. The related results, given in Table 5, demonstrate that the Dicup vulcanized blend containing HVA-2 shows higher retention, which is a hint for good heat resistance compared to Dicup vulca-nized alone. According to the work that has been done by McElwee and Lohr[18], vulcanized blends lead to an increase in the cross-linking density and restrict ion of degradation and hence in tensile properties. The higher the cross-linking level, the smaller the amount of oxygen that penetrates into the rubber particles, resulting in the increase of the percentage of retention. The cross-linking process protected these polymers from extended oxidation. This effect is more pronounced for richer NR content and indicates further cross-linking in the NR phase. Here, the presence of Dicup combined with HVA-2 reduces the NR
[67]
degradation during ageing.The HVA-2 is also capable of reacting with the polymer radicals formed by chain scission during blending because thechain scissions are correlated with oxidation processes.
CONCLUSION
The formation of the coagent bridge and the inhibition of chain scission by HVA-2 in Dicup vulcanization lead to an increase in the viscosity of the PP EPDM NR blend,= =
[20]
FIG. 9. The effect of HVA-2 addition onDicup vulcanized blend on the TGA scan of PP EPDM NR blends.= =
FIG. 10. The effect of HVA-2 addition on Dicup vulcanized blend on the thermal stability of PP EPDM NR blends.= =
TABLE 5
Percentage of retention of tensile and elongation at break of cicup vulcanized blends with and without addition
HVA-2
which subsequently increased the stabilization torque of [23]
the blend. The incorporation of HVA-2 in vulcanized blends increases tensile properties,oil resistance, and gel
[21]
content. The SEMmicrographs from the surface extraction of the blendsalsosupport that thecoagen t bridge occurred during Dicup vulcanization ofPP EPDM NR= = containing HVA-2. Meanwhile, the incorporation of HVA-2 in the Dicup vulcanization blend decreased the percentage of the crystallinity of blend. In addition, the presence of HVA-2 in the blends slows down the degradation and consequently produces a heat stable blend.
REFERENCES
1. Halimatuddahliana; Ismail, H. Polym. Plast. Tech. Eng.2004,43, 357. 2. Coran, A.Y.; Patel, R. Rubb. Chem. Technol.1980,53, 141.
3. Lopez-Manchado, M.A.; Arroyo, M. Rubb. Chem. Technol.2001,74, 11.2 4. Sabet, S.A.; Puydak, R.C.; Rader, C.P. Rubb. Chem. Technol.1996,
69, 476.
5. Ellul, M.D. Rubb. Chem. Technol.2003,76, 202.
6. Xiao, H.; Huang, S.; Jiang, T.; Cheng, S. J. Appl. Polym. Sci.2002,83, 15. 3 7. Sariatpanahi, H.; Nazokdast, H.; Dabir, B.; Sadaghiani, K.;
Hemmati, M. J. Appl. Polym. Sci.2002,86, 3148.
8. Ismail, H.; Halimatuddahliana; Akil, H. Md. J. Solid State Sci. Technol. Lett.2004,11(2), 105.
9. Halimatuddahliana; Ismail, H.; Akil, H. Md. Inter. J. Polym. Mater. 2004,54, 1169.
10. Ho, R.M.; Su, A.C.; Wu, C.H.; Chen, S.I. Polym.1993,34, 3264.
[59]
11. Coran, A.Y. In:Encyclopedia of Polymer Science and Engineering, ark,M H.F.; Bikales, N.M.; Overberger, C.G.; Menges, G.; Kroschwitz, J.I.,
[59]
Eds., 2nd Ed., Canada:John Wiley and Sons, Inc., 1989, 17, 666. 12. Dluzneski, P.R. Rubb. Chem. Technol.2001,74, 451.
13. Inoue, T.J. Appl. Polym. Sci.1994,54, 709. 14. Inoue, T.J. Appl. Polym. Sci.1994,54, 723.
15. Ishikawa, M.; Sugimoto, M.; Inoue, T.J. Appl. Polym. Sci.1996,62, 1495.
16. Dikland, H.G.; Does, V.D.; Bantjes, A. Rubb. Chem. Technol.1992, 66, 196.
17. McElwee, C.B.; Lohr, J.E. Rubber World2001,225, 41. 18. Keller, R.C. Rubb. Chem. Technol.1988,61, 238.
19. Halimatuddahliana; Ismail, H.; Akil, H. Md. Polym. Plast. Tech. Eng. 2005,44, 1217.
20. Greco, R.; Manacarella, C.; Martuscelli, E.; Ragosta, G. Polym.1987, 28, 1929.
21. Dahlan H.M.; Khairul Zaman, M.D.; Ibrahim, A. J. Appl. Polym. Sci.2000,78, 1776.
22. Wu, S. Polym. Eng. Sci.1987,27, 334.
23. Kim, B.C.; Hwang, S.S.; Lim, K.Y.; Yoon, K.J. J. Appl. Polym. Sci. 2000,78, 1267.
24. Stojanovic, Z.; Kacarevic-Popovic, Z.; Galovic, S.; Milicevic, D.; Suljovrujic, E. Polym. Degrad. Stab.2005,87, 279.
25. Saroop, M.; Mathur, G.N. J. Appl. Polym. Sci.1999,71, 151.
![FIG. 4.Reaction sequence of crosslinking in rubber phase by peroxide and HVA-2 [11]](https://thumb-ap.123doks.com/thumbv2/123dok/3907867.1860189/8.595.158.424.81.352/fig-reaction-sequence-crosslinking-rubber-phase-peroxide-hva.webp)
