Compatibilized natural rubberrecycled ethylene-propylene-diene rubber blends by biocompatibilizer
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1.3% 4 matches
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1.3% 7 matches
1.6% 4 matches [45]
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1.6% 9 matches
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Results of plagiarism analysis from 2017-12-06 08:31 UTC Compatibilized natural rubber recycled ethylene propylene diene rubber blends by biocompatibilizer.pdf Date: 2017-12-06 08:28 UTC
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0.3% 1 matches 13 pages, 6100 words PlagLevel: selected / overall 314 matches from 107 sources, of which 90 are online sources. Settings
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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
International Journal of Polymer Analysis and Characterization
ISSN: 1023-666X (Print) 1563-5341 (Online) Journal homepage: http://www.tandfonline.com/loi/gpac20 Compatibilized natural rubber/recycled ethylene-propylene-diene rubber blends by biocompatibilizer Nabil Hayeemasae, Indra Surya & Hanafi Ismail
To cite this article: Nabil Hayeemasae, Indra Surya & Hanafi Ismail (2016): Compatibilized natural rubber/recycled ethylene-propylene-diene rubber blends by biocompatibilizer, International Journal of Polymer Analysis and Characterization, DOI: 10.1080/1023666X.2016.1160970
To link to this article: http://dx.doi.org/10.1080/1023666X.2016.1160970
Accepted author version posted online: 03 Mar 2016. Published online: 03 Mar 2016.
Submit your article to this journal Article views: 14 View related articles View Crossmark data INTERNATIONAL JOURNAL OF POLYMER ANALYSIS AND CHARACTERIZATION http://dx.doi.org/10.1080/1023666X.2016.1160970 Compatibilized natural rubber/recycled ethylene-propylene-diene rubber blends by biocompatibilizer
Nabil Hayeemasae
[60] compatibility two blending components where a strong interfacial adhesion between matrices is of interest .
1
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CONTACT Nabil Hayeemasae Department of Rubber Technology and Polymer Science, Faculty of Science nabil.h@psu.ac.th
studied the effect of
5
[ ]
Currently, the demand for utilization of renewable resources for the production of biosustainable materials is increasing in research areas and manufacturing. One of the renewable resources that are of great relevance to Thailand and the neighboring countries is the growth of palm oil industry. Palm oil is a renewable and sustainable source of fatty acids that represent raw materials that can replace the activator used in rubber compounding. For example, Ismail and Anuar
4 Homogeneous distribution of R-EPDM and their respective compatibility have been a [60] potent challenge in such blend .
[ ]
cure and mechanical properties are difficult to attain due to the differenallenge for the blends based on NR-EPDM. The key factors for improving the performance of rubber blends are
a
3 However, satisfactory state of
[ ]
The blending of NR and R-EPDM has been studied previously.
the straight reprocessing of EPDM become more complicated. This polymeric material cannot return to the ecological environment through biological degradation and is most often discarded after a cer - tain period of time. Recycling of EPDM rubber is an interesting topic in connection with the continu- ous market growth of EPDM. To solve this environmental issue, waste EPDM has been used in an effort to create value-added rubber materials based on a blend of natural rubber (NR) and recycled EPDM (R-EPDM).
2 The cross-linked EPDM is thermoset and insoluble; thus, it causes
1 It represents 7% of world rubber consumption, and it is most widely used for non-tire rubber. [ ]
[ ]
Introduction Ethylene-propylene-diene rubber (EPDM) has been the fastest growing rubber among the synthetic rubbers since its introduction in 1963.
ARTICLE HISTORY Submitted 19 February 2016 Accepted 1 March 2016 KEYWORDS Biocompatibilizer; mechanical properties; natural rubber; recycled ethylene-propylene-diene rubber
ABSTRACT Biocompatibilizer-based refined, bleached, deodorized palm stearin was successfully used as compatibilizer for natural rubber/recycled ethylene– propylene–diene rubber (NR/R-EPDM) blends. It seems effective in improving the state of cure, tensile properties, as well as the swelling resistance and morphology of the blends, indicating an improvement in compatibility between the NR matrix and R-EPDM rendered by biocompatibilizer. This was clearly verified by the dynamic mechanical properties of the blends. The dynamic responses obtained were clearly corresponding to the swelling result. It proves that the cross-link density plays a major role in the changes of storage modulus and degree of entanglement.
c a Department of Rubber Technology and Polymer Science, Faculty of Science and Technology, Prince of Songkla University, Pattani Campus, Pattani, Thailand; b Department of Chemical Engineering, Faculty of Engineering, University of Sumatera Utara, Medan, Sumatera Utara, Indonesia; c School of Materials and Mineral Resources Engineering, Engineering Campus, Universiti Sains Malaysia, Nibong Tebal, Penang, Malaysia
, and Hanafi Ismail
b
, Indra Surya
6 palm oil as an activator in NR compound. It was presented that this material can be replaced the stea-
[96] ric acid to activate the vulcanization process .
2.0
1.2 Sulfur
1.2
1.2
1.2
2.0 CBS
2.0
2.0
1.8
5.0 Stearic acid
5.0
5.0
5.0
30.0 ZnO
30.0
1.8
1.8
30.0
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3 Note. SMR L, L Grade Standard Malaysian Rubber L; R-EPDM, recycled ethylene-propylene-diene rubber; ZnO, zinc oxide; CBS, N- cyclohexyl-benzothiazyl-sulfenamide.
1.8 N330
2
1
30.0 Bio-compatibilizer –
30.0
30.0
30.0
30.0
70.0 R-EPDM
In palm oil industry, crude palm oil (CPO) is extracted from fresh palm (Elaeis guineensis) and it can be used as raw material for manufacturing of refined palm oil. The CPO has to undergo extensive processing before it reaches the consumer. Refined, bleached, and deodorized palm stearin (RBDPS) is derived from the refinery process of CPO that has been used mainly in shortening and margarines.
8 The idea of this study is to use the alkanolamid RBDPS as a biocompatibilizer [56] for NR/R-EPDM blends . Several methods of mixing and functioon have been reported to
10
[ ]
reactive mixing,
9
[ ]
[56] improve the compatibility in the rubber blends such as the usird polymers ,
[ ]
[ ]
7 Fids or their methyl esters (triglyceride) can react with primary and [69] secondary amito produce the corresponding alkanolamides .
[ ]
Generalfatty acid compositions of RBDPS consist of highly saturated and triglyceride contents.
viable material, RBDPS has been widely used in many industries, especially in food industry. However, the applicaf this material in rubber matrices are still largely unexplored.
6 The cost of the RBDPS is cheaper when compared to the major component. Being an economically
[ ]
radiation curing,
11
70.0
3 The N330-grade carbon
70.0
70.0
Amount (phr) Materials and ingredients: Compound designation Control Bio-C1 Bio-C2 Bio-C3 SMR L
12 It was carried out at atmospheric pressure in a 1,000 mL reaction vessel fitted with a Table 1. Formulation of the blends.
[ ]
black was supplied by Malayan Carbon (M) Ltd, Malaysia. Other compounding ingredients, such as zinc oxide, stearic acid, N-cyclohexyl-benzothiazyl-sulfenamide (CBS), and sulfur were purchased from Bayer (M) Ltd. Synthesis of biocompatibilizer based refined, bleached, deodorized palm stearin Biocompatibilizer-based RBDPS can be synthesized according to the optimum conditions described by Surya et al.
[ ]
to name a few. But no reports are available on the detailed investiga-
. The carbon black content in R-EPDM was 29.33%. The physical characteristic of R-EPDM has been reported in our previous study.
3
was in irregular and rough shape and was broken by a mechanical crusher. The specific gravity of the R-EPDM was found to be 1.06 g cm
Precision Technology Co . Ltd. , Taiwan, to obtain particles approximately 10–200 µm in size. R-EPDM [70]
The R-EPDM was ground into a powder form using table-type pulverizing from Rong Tsong [70]
Experimental details Materials The formulation used for blending is presented in Table 1. Natural rubber (SMR L grade) was supplied ardec Berhad, Selangor, Malaysia. Recycled ethylene-propylene-diene rubber (R-EPDM) Penang, Malaysia.
[56]
tions concerning the use of biocompatibilizer-based RBDPS known as alkanolamide to improve the compatibility in such blends . With the surface chemistry of biocompatibilizer-based RBDPS and its waxy appearance in nature, it is believed to improve the dispersion and compatibility of the blends.6 stirrer. First, sodium methoxide was added in the ethanol and stirred in the reaction flask. The mixture of RBDPS and diethanolamine were then added in the solution and mildly stirred (1 mol of RBDPS always contents 3 mol of the corresponding diethanolamine, sodium methoxide, and ethanol, respectively). Next, the mixture was heated, and the reaction temperature was kept constant at 70°C for 5 h. The resultant mixture was extracted with diethyl ether and washed with saturated sodium chloride solution. Finally, the crude product was purified with anhydrous sodium sulfate and concentrated by a rotary evaporator. The final product was then characterized for their respective
[102] functional groups using Fourier transform infrared spectroscopy (FT-IR ). The reaction procedure
and 550 to 4000 cm
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[92] universal tensile machine Instron 3366 to determine the tensile properties such as tensile strength , elongation at break , stress at 100 % (M100), and 300% (M300) elongation. The hardness Figure 1. Proposed chemical reaction of bio-compatibilizer based RBDPS, adapted from Surya et al. [ ] 12 D
1 . Tensile tests were carried out with a
[64] tests were performed at a cross-head speed of 500 mm min
Measurement of tensile properties Dumbbell-shaped samples were cut from the molded sheets ag to ASTM: D412-06ae2. Tensile
1 , respectively.
1
of biocompatibilizer-based RBDPS is shown in . Biocompatibilizer-based RBDPS is in a Figure 1 cream-colored and waxy appearance and is to be used as an additive to improve the compatibility for NR/R-EPDM blends. Preparation of the Our previous work
spectrum resolution and the scanning range were 4 cm
1 Fourier transform infrared The FTIR spectra of the biocompatibilizer-based RBDPS was analyzed using Perkin–Elmer Spectrum One FTIR spectrometer and attenuated total reflection (ATR) technique was adopted . The selected
ð Þ
100 ðtc 90 ts 2 Þ
CRI ¼ [33]
) according to ASTM: D2084-11 samples of the respective blends were tested at 150°C. The cure rate index of the blends was calculatedows:
90
), and curing time (tc
2
lizer. The entire amount of additives as well as NR and R-EPDM were prepared in a laboratory-sized two-roll mill (model XK-160) at ambient temperature. The resulting blends were later tested for its curing characteristics using a Monsanto Moving Die Rheometer (MDR 2000). The compounds were subsequently compression-molded using a stainless steel mold at 150°C with a pressure of 10 MPa using a laboratory hot-press based on respective curing times. Curing characteristics The curing characteristics of the rubber blends were obtained by using a Monsanto Moving Die Rheometer (MDR 2000), which was used to determine torques, scorch time (ts
[70] satisfactory properties . Thus, this blend ratio was selected to further study the effect of biocompatibi -
3 has reported that the blend ratio at 70/30 (phr/phr) of NR and R-EPDM provided
[ ]
6 measurements of the samples were done according to ASTM: D2240-05(2010) using a manual durometer type Shore A. Measurement of swelling behavior Swelling tests were done in toluene in accordance to ASTM: D471-12a. Vulcanized test pieces of
[45] dimension 30 � 5 � 2 mm
e
), V s is the molar volume of the toluene (V s ¼ 106
.4 cm [33]
3
mol 1 ), V r is the volume fraction of the polymer in the swollen specimen , Q m is the weight increase of the blends in toluene, and is the interaction v parameter of the rubber network-solvent ( of NR v
¼ 0 . 393 and of R-EPDM v ¼ 0.49).
The degree [45] of cross-linking density is given by :
V
c ¼
1
2M
c
ð Þ
5 Scanning electron microscopy The examination of tensile fractured surfaces was carried out using a scanning electron microscope (SEM) model Zeiss Supra-35VP to obtain information on the possible presence of micro-defects. The fractured pieces were coated with a layer of gold palladium to eliminate electrostatic charge build-up during examination. Dynamic mechanical analysis Dynamic mechanical properties were measured by using dynamic mechanical analyzer (Mettler Toledo, DMA 861
), supplied by Mettler-Toledo (M) Sdn. Bhd. The samples were subjected to a cyclic tensile strain with force amplitude of 0.1 N at a frequency of 10 Hz. Storage modulus ( ), loss modulus E′ ( ), and damping factor (tan ) were determined in the temperature range from 100 to 60°C at a E″ d
, ρ of R-EPDM ¼ 1. 06 g cm
heating rate of 2°C min
1 .
Results and discussion FT-IR analysis of biocompatibilizer Typical infrared spectrum of biocompatibilizer-based RBDPS is shown in . The wavenumber Figure 2 and its respective assignments are also listed in . The strong and broad band at 3370 cm Table 2
[63] 1 is an
1
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1
6 [6
[46] 3
3
3 were weighed using an electrical balance and swollen in toluene until equilibrium, which took 72 h at room temperature . The samples were taken out from the liquid,
¼ q
[33] the toluene was removed from the samples' surface, and the weight was determined. Calculation of
the changes in mass is as follows
Swelling ¼ [33]
ðW
2 W
1 Þ W
1 � ð Þ 100
2 where W
1 is the iass of specimen (g) and W
2 is the mass of specimen (g) after immersion in toluene. The swelling results were also used to calculate the molecular weight between cross-links
[45] (M c
) by applying the Flory–Rehner equation: [ ]
13 M c
p
4 where is the density of the rubber (ρ of NR q ¼ m
V
s
V
1 3 = r
ln 1 ð V r Þ þ V r
þ vV
2 r
ð Þ
3 V
r ¼
1 1 þ Q
m
ð Þ
3 ]
6
[54] NR and R-EPDM enhanced significantly when the biocompatibilizer is added to the blends .
) increased with further increase of the biocompa- tibilizer. As mentioned in the preceding section, the biocompatibilizer was synthesized from RBDPS and diethanolamine. The structure of biocompatibilizer is similar to amine-based accelerator. There - fore, it could enhance the cross-link density to the blends leaimprove the maximum torque. Similar observation was found for the torque differM
H
L
ng.
[ ]
16 The total cross-linking is contributed [54] lfidic cross-links and physical cross-links
[ ]
17
; this finding could indicate that the cure compati-
The responsible amine content in biocompatibilizer also fastened the scorch and cure times of the [54] blends, indicating that biocompatibilizer could act as a co-curing agent or secondary accelerator in the curing process of NR/R-EPDM blends . Amine is an alkaline substance that increases the pH of Figure 2. FT-IR spectrum of bio-compatibilizer based RBDPS.
improved the processability of the blends. Biocompatibilizer used in this study originated from waxy RBDPS; it was then acting as internal plasticizer resulting to lower the viscosity and improve the pro - cessability of the blends. The maximum torque (M
Table 2. The wavenumbers of functional groups of bio-compatibilizer based RBDPS. [ ] 14 Wavenumber (cm 1 ) Assignments
3370 O–H stretch
2922 Unsaturated (C=C) 2852 Saturated (CH 3 )1615 C= O stretch
1364 CH 3 Umbrella mode
1248 C–N stretch
719 CH 2 rockingD o w n lo ad ed b y [ U n iv er si ti S ai n s M al ay si a] a t
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H
[ ]
saturated and unsaturated portions exist in the molecule .
=
[ ]
14 The umbrella mode at 1364 cm 1
con- firms the presence of a methyl group (CH
3
) that attached to the carbon atom. The (CH
2
) rocking band at 719 cm
1
means that there are more than four methylene atoms in a row in the molecule. The C
O stretch is at 1615 cm
is commonly considered to be a representative of the uncured stock's elastic modulus and also provides valuable information about a compound's processability.
1
, and the amide C–N stretch is at 1248 cm
1 .
[ ]
12 The obtained spectrum is clearly corresponding to the functional groups presented in biocompatibilizer-based RBPDS.
Curing characteristics Curing characteristics of control and compatibilized blends are tabulated in . It was observed Table 3 that the minimum torque (M
L
) decreased with the addition of biocompatibilizer. M
L
[38] ber compound more basic character will then enhance the cure rate since acidic materi to retard the effect of the accelerator .
5.27
15.85
16.46
16.89
16.93 ts 2
1.85
1.33
1.30
1.12 tc 90
8.27
5.31
4.99 CRI
17.54
15.58
25.12
25.18
25.84 Figure 3. Tensile strength of control and compatibilized NR/R-EPDM blends.
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17.53 M H –M L
17.18
[ , ] 12 18
21
According to Bateman,
[ ]
19
and Ismail and Ng,
[ ]
20 a certain
[38] organic substance containing nitrogen atoms promotes the curing process of olefinic rubber, com - prising sulfur and primary accelerators, through the formation of complexes that are responsible for the fission of the sulfur molecules to form cross-links between the linear rubber chains. It is
[38] expected that the amine content of the biocompatibilizer would accelerate the cure and is responsible for enhancing the cure rate and the cure state of the blends .
Tensile properties and swelling results [64]
Figure 3 shows the effect of biocbilizer content on the tensile strengths and elongation at break of the blends . It was observed that the tensile strength increased up to the maximum level of 2 phr and [62]
then decreased with further increases in the biocompatibilizer content . According to Hertz,
[ ]
and Ismail and Chia,
16.61
[ ]
22
the tensile streng as tensile strength increase, whereas viscous loss pro- perties, such as hysteresis, decrease.
[ ]
23 Further increases in the cross-link density will then produce [62] a vulcanizate that tends toward brittle behavior . Thus, at a higher cross-link density, such elastic properties as mentioned earlier begin to decrease.
Another possible reason might be due to the highly dispersed carbon black, arising from the inter - action of biocompatibilizer and carbon black in the blends. As can be seen in , Figure 4 the ethanol is released during the curing process of the blends that has brought to the reactive amine group ready to couple with the available carboxylic group and/or hydroxyl group in carbon black while the non-polar hydrocarbon of biocompatibilizer interacts physically through dipole interaction with the long chain of Table 3. Curing characteristics of control and compatibilized NR/R-EPDM blends.
Curing characteristics Control Bio-C1 Bio-C2 Bio-C3 M L
0.76
0.72
0.65
0.60 M H
6
- tion of the biocompatibilizer itself acting as an internal plasticizer of the blends . Biocompatibilizer is a
Sample codes M100 (MPa) M300 (MPa) Hardness (shore A) Swelling (%) Cross-link density ( 10 � 5 mol cm 3 ) Control 2.11 � � � � �
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0.05 7.21 0.17 65 0.7 167.43 1.72 43.67 0.55
0.03 6.77 0.11 67 0.8 169.25 1.45 42.18 0.74 Bio-C3 1.85 � � � � �
0.05 6.73 0.20 66 0.6 178.27 1.24 41.03 0.60 Bio-C2 1.78 � � � � �
0.04 8.31 0.09 65 0.4 177.40 0.77 41.36 0.42 Bio-C1 1.77 � � � � �
Table 4. Tensile modulus, hardness property, swelling and cross-link density of control and compatibilized NR/R-EPDM blends.
ted.
Figure 4. Possible mechanism between bio-compatibilizer and carbon black in the blends.
� obtained from the SEM results are significantly in agreement with the results on the tensile strength. The surface roughness and tearing lines were observed in the control blend ( ), meaning more Figure 5a energy was needed to break the sample. However, rougher surfaces and number of tear lines were more pronounced and visible in the blends with the biocompatibilizer of 1 and 2 phr, respectively (Figure 5b and c). The sample had altered the crack path, which led to more resistance for crack propagation and,
Tensile-fractured surfaces Figure 5 illustrates the SEM micrographs of the tensile-fractured surfaces of the control and compatibilized NR/R-EPDM blends at a magnification of 100 . The micro-fractured surfaces
[54]
to more responsible amine content in biocompatibilizer that acts as a co-curing agent or secondary accelerator in the curing process of NR/R-EPDM blends .The swelling uptake and cross-link density of the control and compatibilized blends determined by equilibrium swelling method in toluene is also shown in . It is widely accepted that the swelling Table 4 is directly correlated to the cross-link density of a network chain, with less solvent uptake or penetration into the blends indicating higher cross-link density. The swelling percentage decreased toward the addition of biocompatibilizer. This revealed that the compatibilized blends contained more cross-links than the control counterpart. The increment of cross-link density could be attributed
23 Further increases in the cross- [62] link density produce a vulcanizate that tends towards brittle behavior. This observation was also found for the hardness property of the blends where the trend was similar to that of tensile modulus.
[ ]
Table 4 shows the tensile modulus (M100 and M300), hardness, swelling, and cross-link density of control and compatibilized blends. Stress at 100 and 300% elongation exhibited lower value when bio - compatibilizer was added but increased with further increase the biocompatibilizer content. The lower tensile modulus when biocompatibilizer was added is attributed to the softening effect of the biocom - patibilizer itself. As the biocompatibilizer is waxy and solid material, modulus upon increasing biocompatibilizer content is due to the improved cross-link density.
waxy and solid material derived from RBDPS, a type of natural oil. Although biocompatibilizer has a smaller molecular size compared to NR and R-EPDM, it could provide a monolayer in the rubber compound that then gives a free volume, allowing more mobility/flexibility for the rubber chains. Increasing the biocompatibilizer content has the same effect as an increase in free volume of the blends.
[64]
Surprisingly, incremental small amount of biocompatibilizer (1–3 phr) into the NR/R-EPDM [64] blends resulted in improving the elongation at break of the blends . This can be attributed to the func
6 hence, resulted in higher tensile strength. The development in the micro-fractured surface of this blend might be attributed to the formation of more cross-links of compatibilized blends. However, the micro-fractured surface of the compatibilized blends tended to be smoother and had a smaller cracking area when the biocompatibilizer content went beyond 2 phr ( ). The reduction in the tearing Figure 5d lines with higher biocompatibilizer (3 phr) was responsible for the tensile strength results, which indicated that lower energy was required to initiate the crack or reduce the ability of the matrix to deform when subjected to strain. This is simply due to more pronounced plasticizing or lubricating effect of the excessive biocompatibilizer. Similar observations were reported elsewhere,
[ , ] 10 24
D o w n lo ad ed b y [ U n iv er si ti S ai n s M al ay si a] a t
1
2
4 A p ri l
2
8
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�
con- cerning the dependence of micro-fractured surfaces and tensile properties in conjunction with the use of compatibilizers in rubber blends. Dynamic mechanical properties Figure 6a shows the storage modulus (E′) as a function of temperature of control and compatibilized blends. The raw output is also summarized in . The curves show three separated regions: a Table 5 glassy region where the segmental mobility and molecular chains are restrained, a transition zone where a considerable decrease in the values with increasing the temperature, and a rubbery region E′ or flow region ( ) where a drastic drop in the modulus is a function of temperature. At Figure 6a
Figure 5. SEM micrographs obtained from tensile fractured surfaces of the NR/R-EPDM blends: control (a), Bio-C1 phr (b), Bio-C2 phr (c) and Bio-C3 phr (d) at 100 magnifications.
of storage modulus in compatibilized blends can be also influenced by the improved interaction between carbon black and biocompatibilizer as depicted in Figure 4 . The presence of active amine
[55] responsible for the higher cross-link density of the compatibilized blends . Besides, an augmentation
[55] evant explanation is therefore associated to the highee of cross-linking assisted by the addition of biocompatibilizer . It is well elucidated earlier that the amine contained in biocompatibilizer is
[ , ] 10 25 A rel-
[55] storage modulus is directly related to the degree of y and, thus, cross-link density .
[45] presented temperature (25°C), the findings clearly revealed that the storage modulus ( ) of ce
6 process, forming highly dispersed carbon black. As a result, the storage modulus increased with an increase in biocompatibilizer content.
Dependence of loss modulus ( ) as a function of temperature is shown in . The loss E″ Figure 6b modulus ( ) peak generally reflects the energy loss in internal motion per unit deformation of the E″ polymer chains.
48.50 Bio-C3 24.15 324.28 0.4090
00 max ) and damping factor (tan δ max ) and the glass transition temperature (T g ) of control and compatibilized NR/R-EPDM blends.
Sample codes E (MPa) E
00 max (MPa) tan δ max T g (°C) with respect to tan δ max Control
21.65 721.18 0.5073
50.67 Bio-C1 22.85 462.07 0.4367
50.10 Bio-C2 23.26 403.17 0.4054
46.98
Figure 6. Dependence of storage modulus (a), loss modulus (b) and damping factor (c) as a function of temperatures and apparent activation energy and degree of entanglement (d) of control and compatibilized NR/R-EPDM blends.
D o w n lo ad ed b y [ U n iv er si ti S ai n s M al ay si a] a t
2 :0
8
2
4 A p ri l
2
1
Table 5. Storage modulus (E ) at 25°C, maximum loss modulus (E
are greatly influenced by higher cross-linking of compatibilized blends. Generally, any type of molecular interactions that manipulate the molecular motion leads to shift to a higher temperature. Besides, the
[ ]
g
26 As shown in , the compatibilized blends exhibited comparatively lower Table 5
maximum loss modulus peak than control blends and it decreased with an increase in the biocompa - tibilizer content. This is simply due to the decrease in energy loss being raised from the higher degree of cross-linking of the compatibilized blends. This finding corresponds to the damping characteristics of the blends as shown in . Figure 6c Damping characteristic is a crucial parameter related to the study of viscoelastic behavior of the rubber vulcanizate. It is obvious that the value of tan d
max
(see ) Table 5 decreased with increasing the content of biocompatibilizer. Higher cross-linking toward the addition of biocompatibilizer strongly affects the reduction of damping characteristic (tan d
max
) in the blends containing higher biocompatibilizer content. The glass transition temperature (T
) of control and compatibilized blends given by tan d
g
max
are tabulated in . It can be seen that Table 4 T
g
of these two blends gradually increased in the presence of biocompatibilizer. The T
g
of control and compatibilized blends increased from 50.67°C (control) to 50.10°C (Bio-C1), 48.50 (Bio-C2), and 46.98°C (Bio-C3), respectively. The changes of
T
6
T
a
a
) for glass transition temperature can be determined from Equation (7). This expression represents a linear fit with the slope equal to 2.303 RT
g
/E
a when log is plotted against g T / – T T .
The apparent activation energy (E
a
) values for glashat the Figure 6d E
a
increased with an increase in the biocompatibilizer. This indicates that the mobility of the rubber chain is decreased in the presence
[33] of biocompatibilizer, arising from the shifting of T g to higher temperatures. Thus, higher apparent
activation energy (E
a ) is essential to mobilize the rubber chains in the range of glassy region.
Correlation of the apparent activation energy (E
) and the molecular mobility can be extensively clarified by the peak height of damping factor (tan d as depicted in ). The higher the tan Table 5 d
g
max
, the higher the peak height is. Here, the damping peak appears in the range of the glassy region where the material changes from a rigid to a rubbery state, contributing to the movement of small groups and molecular chains within the polymeric structure that are initially frozen. Therefore, lowering of the peak height can be attributed to the lowering of the mobility of the polymer chains. Consequently, with this effect, it is concluded that the molecular restriction increases with an increase in the content of the biocompatibilizer, corresponding to higher apparent activation energy (E
a
) described in the preceding discussion. Degree of entanglement The degree of entanglement ( ) of the rubber blends can be acquired from dynamic mechanical N analyzer. The storage modulus output can be applied for determining the entanglement density. Calculation of degree of entanglement is expressed as follows:
[ ]
E
6RT ð Þ
8 where E′ is the storage modulus obtained from the plateau region of E′ as a function of temperature, R D o w n lo ad ed b y [ U n iv er si ti S ai n s M al ay si a] a t
2 :0
8
2
4 A p ri l
2
1
. T is the temperature which viscosity ( ) also reaches its maximum point. The apparent acti- g vation energy (E
7 where is absolute temperature and T T is defined as the VFT temperature, which is roughly 50°C below the T
g
a
, increased slightly with the addition of biocompatibilizer. The small increment of this value might be due to the compromising effect between the plasticizing nature of biocompatibilizer and the formation of the proposed interaction (see ). A monolayer of waxy-appearance bio Figure 4 - compatibilizer provides free volume, thus allowing the mobility for the rubber chains. This has brought the compromise between mobility and/or immobility in the rubber chains that resulted in a small increase in the T
g eventually.
Apparent activation energy for glass transition According to Manzur and Hernández-Sánchez,
[ ]
27
both storage modulus ( ) and loss modulus ( ) E′ E″ are related to the viscosity of the blend by the following relation: g
¼ ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi E ð Þ
2
þ E
00
ð Þ
2
2pf s ð Þ
6 Here, the viscosity ( ) value is used to calculate the apparent activation energy ( g E
) for the glass transition of a polymer. It represents the potential energy barrier that the motion of the chain segments has to overcome for the transition to take place,
ð Þ
[ ]
27
and this can be determined from the non-Arrhenius behavior of viscosity using Vogel–Fulcher–Tammann (VFT) equation:
[ ]
28
g g ¼ exp 2 303
:
RT
g
T �
E
a
ð T T
Þ � �
6 control and compatibilized blends is also shown in . A higher degree of entanglement occurs Figure 6d with increasing the content of the biocompatibilizer. This is simply due to the cure compatibility between highly unsaturated NR and highly saturated EPDM. It generally leads to superior mechanical properties of the vulcanizates caused by even distribution of cross-link density. The available amine content in biocompatibilizer is responsible on the enhancement of cross-linking distribution. As a result, the blends revealed superior degree of entanglement with an increase in the content of the biocompatibilizer. Conclusions The reactive amine–contained biocompatibilizer has a strong influence on the promotion of y dispersed carbon black to the blends. This can be clearly seen frenhancement of overall tensile
[65] properties, swelling resistance, and morphology as well as the cure and dynamic mechanical properties of the blends. The compatibilized NR/R-EPDM blends impart higher values of tensile
[6] Technical Report of Refined. Bleached Deodorized Palm Stearin. Available at: http://www.bepcthai.com/our- products.html (accessed on February 18, 2016). [7] Man, Y. C., T. Haryati, H. Ghazali, and B. Asbi. 1999. Composition and thermal profile of crude palm oil and its products. . 76:237–242. J. Am. Oil. Chem. Soc [8] Adewuyi, A., R. A. Oderinde, B. Rao, and R. Prasad. 2012. Synthesis of alkanolamide: A nonionic surfactant from the oil of . . 15:89–96. Gliricidia sepium J. Surfact. Deterg [9] Chang, Y. W., Y. S. Shin, H. Chun, and C. Nah. 1999. Effects of trans-polyoctylene rubber (TOR) on the properties [51] of NR/EPDM blends . . 73:749–756. J. Appl. Polym. Sci
1
2
4 A p ri l
2
8
2 :0
D o w n lo ad ed b y [ U n iv er si ti S ai n s M al ay si a] a t
Int. J. Polym. Anal. Charact. 20:406–413. [12] Surya, I., H. Ismail, and A. R. Azura. 2013. Alkanolamide as an accelerator, filler-dispersant and a plasticizer in [63] silica-filled natural rubber compounds . . 32:1313–1321. Polym. Test [13] Flory, P. J., and J. Rehner Jr. 1943. Statistical mechanics of cross-linked polymer networks II . Swelling. J. Chem. [101] Phys. 11:521–526.
[11] Rahman, W., J. Alam, and M. R. Khan. 2015. Effect of manganese on radiation vulcanization of natural rubber.
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[96][65] strength, hardness, and elongation at break than the control blends. The storage modulus increased
[4] Suma, N., R. Joseph, and K. George. 1993. Improved mechanical properties of NR/EPDM and NR/butyl blends by [60] precuring EPDM and butyl . . 49:549–557. J. Appl. Polym. Sci
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[3] Nabil, H., H. Ismail, and A. Azura. 2013. Compounding, mechanical and morphological properties of carbon- [87] black-filled natural rubber/recycled ethylene-propylene-diene-monomer (NR/R-EPDM) blends . . Polym. Test 32:385–393.[1] Sutanto, P., F. Laksmana, F. Picchioni, and L. Janssen. 2006. Modeling on the kinetics of an EPDM devulcanization [88] in an internal batch mixer using an amine as the devulcanizing agent . . 61:6442–6453. Chem. Eng. Sci
References
) whereas a higher molecular restriction for NR/R-EPDM blends was found in the rubbery region, as evidently shown in degree of entanglement. The dynamic responses obtained from storage modulus, degree of entanglement, and apparent activation energy are clearly corresponding to the swelling result. It proves that the cross-link density plays a major role in the changes of storage modulus and degree of entanglement irrespective of the methods of the determination.
a
when the content of biocompatibilizer was increased. At the glassy region, compatibilized blends disclosed lower chains mobility as confirmed by higher apparent activation energy (E
g
of the blends by presenting higher T
g
with increasing content of biocompatibilizer whereas reverse trend was found for loss modulus and damping behavior (tan d). Biocompatibilizer also affected the T
6
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