Properties of Polypropylene (PP)/Ethylene-Propylene Diene Terpolymer (EPDM)/Natural Rubber (NR) Vulcanized Blends: The Effect of N,Nm-Phenylenebismaleimide (HVA-2) Addition
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Results of plagiarism analysis from 2017-12-06 05:18 UTC Properties of Polypropylene PP Ethylene Propylene Diene Terpolymer EPDM Natural Rubber NR Vulcanized Blends The Effect.pdf Date: 2017-12-06 05:14 UTC
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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 Sensitivity: Medium Bibliography: Consider text Citation detection: Reduce PlagLevel Whitelist: --
Polymer-Plastics Technology and Engineering [28]
ISSN: 0360-2559 (Print) 1525-6111 (Online) Journal homepage: http://www.tandfonline. 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[28]
To cite this article: Halimatuddahliana & H. Ismail (2008) Properties of Polypropylene (PP)/
[33]
Ethylene-Propylene Diene Terpolymer (EPDM)/Natural Rubber (NR) Vulcanized Blends : The
Effect of N,N-m-Phenylenebismaleimide (HVA-2) Addition , Polymer-Plastics Technology and
Engineering , 48: 1, 25-33, DOI: 10.1080/03602550802539155To 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 Citing articles: 1 View citing articles ISSN: 0360-2559 print/1525-6111 online DOI: 10.1080/03602550802539155
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 #
[11,12] .
[8]
and dicumyl peroxide (Dicup)
[9] to
[12] ie the properties of such blends.
The presence of Dicup in the blends is to produce [12] reactive radicals upon decomposition at elevated tempera- ture via exothermic reaction that is beneficial in a rubber compound . It is generally aat 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 retermined by cross-link structures that form
Coagents, in the other hand, can be used to compou nd [8] elastomers, thermopls, and thermop lastic elastomer = blends with and witthe presence of accelerators or
[2–7]
[8] e 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 iration 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
. Dynamic vulc = = sing sulfur
= on the processing and the improvements on mechanical and physical properties of the blends
of Polypropylene (PP)/Ethylene-Propylene Diene Terpolymer (EPDM)/Natural Rubber (NR) Vulcanized Blends: The Effect of N,N-m-Phenylenebismaleimide (HVA-2) Addition
investigations have been reported regarding the dynamic vulcanization of thermoplastic elastomer, especially on PP EPDM blends, and most of the investigations focused
vulcanization has been introduced in the PP EPDM NR = = blend to improve the properties of such blends. Some
[33]
Halimatuddahliana
1 [32] and H. Ismail
2
1 Department of Chemical Engineering, Universitas Sumatera Utara, Indonesia
2 School 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 a compatibilizer. Blends were
prepared in several blend ratios in a Haake Polydrive with tempera- ture and rotor speed of 180
100 ), elongation at break, oil resistance, and gel content in all blend ratios compared to similar [23] vulcanized blends with Dicup without HVA-2 addition. Scanning electron microscope (SEM) micrographs of the blends support that the cross-linking and compatibilization occur during the process of [20] the vulcanized blend containing HVA-2 . In the case of crystallinity of the blends, the aof HVA-2 in Dicup vulcanized blend revealed a tendency he percentage of crystallinity (Xc) to [8] decrease. The addition of HVA-2 in Dicup vulcanization also 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 served that the partial replacement of EPDM bexhibits lower properties of PP EPDM blends
=
[1][12]
. Therefore, dynamic
C 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 (M structures during vulcanization, forming a so-called coagent bridge.
Keller
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,
loaded into the internal mixer and pre-mixed for 2 min fol- [8] lowed by 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
blends. During blending, thermoplastics (PP) were first
[8]
= =
C and 50 rpm, respectiTable 1 shows the mixing sequence of components preparation of the PP EPDM NR
R600 610, at temperature and rotor speed of 180 =
= = = = = = 50 10 40, and 50 0 50. Blends were prepared by melt mix- = = = = ing in an internal mixer, Haake Polydrive with Rheomix
dies were conducted on PP EPDM NR blends con- = = of two systems viz. blend with Dicup vulcanization
Tensile Properties [12]
Preparation and Processing [12]
used for the blend was -phenylenebismaleimide N,N-m (HVA-2), a free radical cross-linking agent from DuPont Dow Elastomer.
(Dicup) was purchased from Aldrich. The coagent
[53]
C of 73 was obtained from Hokson Rubber Trading Sdn. Bhd, Seremban. Dicumyl peroxide
cosity ML (1 4) at 100 þ
C of 74 was purchased from Luxchem Trading Sdn . Bhd. Natur al rubber (NR-HSL) with Mooney vis-
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 tests were carried out according to A412 [55] on an Instron machine; 2-mm thick dumbbell specimens were cut from the molded sheets with a Wallace die cutter .
[44]
a
a Irganox 1010 (0.4 phr). b Based on the rubbers content (EPDM and NR). c Based on the NR content.
10 Dump
9 —
8 Dump —
7 — —
6 — —
a
DCP and HVA-2 addition þ antioxidant
5 DCP addition þ antioxidant
TABLE 1 Mixing sequence of components in preparation of the
2 Rubbers addition Rubbers addition
) PP loading PP loading
c
) Blend with combination of DCP and HVA-2 (3 phr
b
Vulcanized with DCP (1 phr
Operation Time (min)
PP EPDM NR blends = =
C and 2. 16 kg. Ethylene-propylene diene terpolymer (EPDM-EPT 3072E), with Mooney Viscosity ML (1 4) þ at 100
(M) Sdn Bhd, Johor , Malaysia (TITANP31 grade), with a melt flow index (MFI) value of 230
[18]
þ P ! P
4 P
ð Þ
! P P Cross-link
ð Þ 3 2P
þ RH H abstraction
2 R
Peroxide decomposition ð Þ
2R
heat
1 Peroxide !
ð Þ
has suggested briefly that the process initiates via thermal decompostition of the peroxide and how the coagent affects the reaction. A generalized scheme is shown as foll ows:
þ R
! P R No cross-link
Materials Polypropylene (PP) homopolymer used in this study was an injection-molding grade, supplied by Titan PP Polymers
also enhances Reaction (2). In addition, the presence
= = EXPERIMENTAL [21]
= = influence the process development, tensile properties , mor- phology, oil resistance, gel content, and thermal properties of PP EPDM NR blends.
[32] efficiency. This paper discusses the role of HVA-2 in Dicup vulcanization of PP EPDM NR blends and how it can
[38] PP EPDM NR blends . It was concluded that the sup- = = pression of chain scissiovement of the cross-linking
[8] properties and degree of cross-linking, the presence of HVA-2 in Dicup vulcanization significantly affects the extent of recombination of macroradical s (from chain scis- sion) and improves the cross-lining he at efficiency, which can be attributed to the formation of coagent bridge in
[19] reported that in terms of tensile
A previous paper
of a reactive olefinic site as in the terpolymer shifts Reac- tion ( 2) from the polymer backbone to the pendant unsa- turation, thus intensifReaction ( 3) and suppressing Reaction (5).
[42]
ð Þ
to produce stable radicals. The polyfunctional nature of the coagent
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
¼
þ P
0
! P
5 P
26 HALIMATUDDAHLIANA AND H. ISMAIL
HVA-2 ADDITION TO PP/EPDM/NR BLENDS
the specimens were removed from the oven, cooled at room temperature, and allowed to rest for at least 16 h before
D
The parameter percentage of crystallinit y (Xc) was calcu- lated by dividing the measured Hf by the Hf of 100 % polypropylene. The Hf for polypropylene as a fully
D 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 600
C at nitrogen airflow of
50 ml min and a heating rate of 20 = C min .
= ng Test
[17] he ageing test was done according to ASTM D573 .
Dumbbell specimen s were hung in an air oven at the [17] temperature of 100
C for 72 h. At the end of the test period,
[12]
[17]
determination of tensile properties. Retention in properties
was calculated as Properties retention % 100 %
3 ð Þ ¼ A O
= ð Þ Where is the value after ageing, and is the original A O value .
[12] Process Development The torque developments of selected Dicup vulcaniza- tion of 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 adcan be explained by a radical-induced cross- liny 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.
27
[17] of the crystals . The melting temperature (Tm) and the heat of fusion ( Hf) were measured during the heating cycle.
The specimen was tested using a t rate (50 mm = min) at room temperature of 25
RESULTS AND DISCUSS ION
C min to about =
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 20
C. The results were quoted
based on the average value of five specimens tested for each blend syst em. Morphology Studies
[12] Morphological evaluations of PP EPDM NR surfaces = = were done using a scanning electron microscope (SEM), model Stereoscan 200 Cambridge. Thcanized samples
were etched with nitric acid for 2 dayshed with water,
[8]
and then dried. All the samples were mounted on alumi-
num stubs and sputter-coated with a thin layer of gold to [8] avoid electrostatic charging during examination . The examinations were done within 24 h of preparation.
Swelling Test [8]
Determination of the swelling index was carried out according to ASTM D471. The specimens with dimensions
of 30 mm 5 m m
2 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 indee blends was then calculated as follow:
Swelling index ¼ [54]
W
2 W
1 ð Þ 100%
1 Where W
1 and W
2 are weight of specimen before 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 80
C for 30 min and subsequently weighed.
The percentage of gel content of the blends was then calcu- lated as follo
2 Where W
% gel content ¼ [44]
W g
W o
ð Þ 100%
g and W are sample weights after and before extraction, respectively .
Differential Scanning Calorimetry (DSC) Study [44]
omplete melting 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
[16][12]
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 of Dicup vulcanization HVA-2 addition on tensile þ strength of PP EPDM NR blends . = = [38] 28 HALIMATUDDAHLIANA AND H.
= = 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
5. The Dicup vulcanized (50 0 50) blend containing HVA-2 generated the highest
The introduction of HVA-2 on the Dicup vulcanization [24] blend has also slightly increased the tensile modulus of the blends, as can be seen in Fig.
. 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 e
[16]
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
coagent affecting molecular structure of the cross-links where the coagent molecules can be incorporated into the cross-link structure during vulcanization of rubber forming is a so-called coagent bridge. The suggested reaction
. As mention ed before, the
presence of coagents in the perulcanization was also reported by Dikland et al.
[66]
formation in the vulcanized blends by the addition of HVA-2 . The increase of the cking efficiency in the
increase. This can be attributed to the extensive cross-link
[14]
= = strength, 13.5 MPa 2 MPa, which is about a 35%
= = PP EPDM NR blve the highest value in tensile
= = 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
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
cates that the effect of HVA-2 on the Dicup vulcanized blend was more significant than on the NR richer blend. Tensile Properties
torque increases with the increase of NR content. This indi-
mostly reacted with HVA-2. Furthermore, the stabilization
ISMAIL on of a coagent bridge.
Figure 6 shows tharison of elongation at break of [14]
Dicup vulcanized with and without HVA-2 [14] addition. It can be seen that the elongation at break of the vulcanized blend 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 vulcanization HVA-2 addition on tensile þ modulus (M 100 ) o f P P = = EPDM NR blends.
FIG. 6. The effect of Dicup vulcanization HVA-2 addition on elonga- þ tion at break of PP EPDM NR blends. = =
29
HVA-2 ADDITION TO 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.
1.25 = = 50 30 20
TABLE 2 Comparison of the swelling index between dicup vulcanized PP EPDM NR blends with and without
= = HVA-2 addition
Swelling index Blend ratio (PP EPDM NR)
= = Dicup vulcanization
Dicup vulcanization þ HVA-2 50 40 10
1.28
1.31
FIG. 7. SEM micrographs of extracted surface PP EPDM NR = = blends: (a) Dicup vulcanized 50 30 20, (b) Dicup vulcanized 50 30 = = = =
1.28 = = 50 20 30
1.42
1.38 = = 50 10 40
1.45
1.36 = = 50 0 50
1.46
1.31 = =
20 HVA-2, (c) Dicup vulcanized 50 0 50, and (d) Dicup vulcanized þ = = 50 0 50 HVA-2. = = þ
associated with the increase of cross-lin k efficiency due to the formation of a coagent bridge by HVA-2.
Morphology Study [20]
[22]
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 in vulcanized 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 les, the tendency of the rubber particles to dissolve e 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 rubber in PP EPDM NR blends under
= = dynamic cross-linking conditions. The same observation
was obtained by Wu
, 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.
there is an increase in percentage of gel. This is again
Swelling 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 the Dicup vulcaniza- tion on the percentage of gel 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]
30 HALIMATUDDAHLIANA AND H. ISMAIL
HVA-2 ADDITION TO PP/EPDM/NR BLENDS
DH f (J g)
95.5 = = 50 0 50
92.6
96.5 = =
[41] FIG. 8. The effect of Dicup vulcanization HVA-2 addition on DSC þ scans of 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
= = blend Melting temperature, T m (
C) Fusion enthalphy,
= %
Dicup vulcanization þ HVA-2 50 30 20
Crystallinity, X c ( )
% Dicup vulcanized blend 50 30 20 158
38.9 18.61 = = 50 0 50 157.4
36.1
17.25 = =
Dicup vulcanized blend HVA-2 þ 50 30 20 161.6
34.9
16.7 = = 50 0 50 160.3
35.8
17.12 = =
31
91.1
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 detailed thermal properties of such blends derived from DSC scan thermograms are tabulated in Table 4.
= = 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
20 =30=
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 peak may be related to the formation of a new crystal and change in crystal structure by HVA-2.
However, this peak disappeared in the 50 0 50 PP = = = EPDM NR blend.
The PP melting peak (T ) of Dicup vulcanized blend is m shifted toward higher temperatures by the presence of HVA-2, indicating an effective cross-linking of the rubbers.
% Blend ratio (PP EPDM NR)
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 and m 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 ( )
= = Dicup vulcanization
[56]
63 = = 50 20 30
Blend ratio (PP EPDM NR)
= = Tensile strength
Elongation at break Tensile strength
Elongation at break 50 40 10
51
55
85
69 = = 50 30 20
52
57
76
55
% Dicup vulcanization
55
71
62 = = 50 10 40
58
55
69
68 = = 50 0 50
60
64
65
67 = =
Dicup vulcanization þ HVA-2
HVA-2 Retention ( )
temperature. This is due to the presence of HVA-2, which
(100
formed a coagent bridge during processing that hinders easy transport of thermal energy across the material during heating and subsequethe formation of degradation
[14]
products. The initial decomposition temperature increased
fect of HVA-2 in NR.
The effect of HVA-2 addition on the thermal 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
[14]
TABLE 5 Percentage of retention of tensile and elongation at break of cicup vulcanized blends with and without addition
C) is shown in Table 5. The deterioration of the tensile
properties of the Dicup 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 the chain 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 on Dicup 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. = =
32 HALIMATUDDAHLIANA AND H. ISMAIL
33 HVA-2 ADDITION TO PP/EPDM/NR BLENDS 9. Halimatuddahliana; Ismail, H.; Akil, H. Md. Inter. J. Polym. Mater. which subsequently incrhe stabilization torque of
[23] 2004 , 54 , 1169.
the blend. The iration of HVA-2 in vulcanized
1993
34 10. Ho, R.M.; Su, A.C.; Wu, C.H.; Chen, S.I. , , 3264. blends increases troperties, oil resistance, and gel [59]
Encyclopedia of Polymer Science and Engineering [21]
11. Coran, A.Y. In: , ark, M content . The SEM micrographs from the surface extraction
H. F.; Bikales, N.M.; Overberger, C.G.; Menges, G.; Kroz, J.I., [59] of the blends also support that the coagen t bridge occurred Eds., 2nd Ed., Canada: John Wiley and Sons, Inc . , 1989, 17, 666.
2001
74 12. Dluzneski, P.R. Rubb. Chem. Technol. , , 451. during Dicup vulcanization of PP EPDM NR containing
= =
54 13. Inoue, T.J. Appl. Polym. Sci. 1994 , , 709.
HVA-2. Meanwhile, the incorporation of HVA-2 in the 1994
54 14. Inoue, T.J. Appl. Polym. Sci. , , 723.
Dicup vulcanization blend decreased the percentage of
1996
62
15. Ishikawa, M.; Sugimoto, M.; Inoue, T.J. Appl. Polym. Sci. , ,
the crystallinity of blend. In addition, the presence of 1495. HVA-2 in the blends slows down the degradation and
16. Dikland, H.G.; Does, V.D.; Bantjes, A. Rubb. Chem. Technol. 1992 ,
66 , 196.
consequently produces a heat stable blend.
2001 225 17. McElwee, C.B.; Lohr, J.E. Rubber World , , 41. 1988
61 18. Keller, R.C. Rubb. Chem. Technol. , , 238.
REFERENCES 19. Halimatuddahliana; Ismail, H.; Akil, H. Md. Polym. Plast. Tech. Eng.
2004 43 2005
44 1. Halimatuddahliana; Ismail, H. Polym. Plast. Tech. Eng. , , 357. , , 1217.
53 2. Coran, A.Y.; Patel, R. Rubb. Chem. Technol. 1980 , , 141.
20. Greco, R.; Manacarella, C.; Martuscelli, E.; Ragosta, G. Polym. 1987 ,
3. Lopez-Manchado, M.A.; Arroyo, M. Rubb. Chem. Technol. 2001, 74, 11.
2
28 , 1929. 1996
4. Sabet, S.A.; Puydak, R.C.; Rader, C.P. Rubb. Chem. Technol. , 21. Dahlan H.M.; Khairul Zaman, M.D.; Ibrahim, A. J. Appl. Polym.
69 2000
78 , 476. Sci. , , 1776.
2003
76 5. Ellul, M.D. Rubb. Chem. Technol. , , 202.
22. Wu, S. Polym. Eng. Sci. 1987 , 27 , 334.
6. Xiao, H.; Huang, S.; Jiang, T.; Cheng, S. J. Appl. Polym. Sci. 2002, 83 , 15.
3
23. Kim, B.C.; Hwang, S.S.; Lim, K.Y.; Yoon, K.J. J. Appl. Polym. Sci.7. Sariatpanahi, H.; Nazokdast, H.; Dabir, B.; Sadaghiani, K.; 2000
78 , , 1267. 2002
86 Hemmati, M. J. Appl. Polym. Sci. , , 3148.
24. Stojanovic, Z.; Kacarevic-Popovic, Z.; Galovic, S.; Milicevic, D.;
8. Ismail, H.; Halimatuddahliana; Akil, H. Md. J. Solid State Sci. Suljovrujic, E. Polym. Degrad. Stab. 2005 , 87 , 279.
2004
11 1999
25. Saroop, M.; Mathur, G.N. J. Appl. Polym. Sci. , , 151.
71 Technol. Lett. , (2), 105.