The objective of this research was to prepare elastomer has multiple properties that can be used in different applications. The purpose of this research was to create an elastomer with diverse qualities that can be employed in a variety of applications. At the same time the elastomer is based on environmentally friendly, low-cost materials. It is critical to use a sustainable preparation technique free of harmful chemicals and additives to achieve a product with high purity and no contaminants. The properties of elastomer created from the cross-linking chemical bonds and flexibility from the stretched hydrogen bonds. When mixing CMC with acrylic acid AA monomer hydrogen bonds was created between them (Fig. 1 step 1). The addition of TA in the reaction medium as a cross-linker creates more hydrogen bonds as seen in Fig. 1 (step2). When CMC, AA monomer, and TA mixture solution was irradiated by gamma radiation, Fig. 1 (step3). The exposure of these ingredient to radiation AA can undergo polymerization under the influence of gamma radiation. In the presence of CMC, this polymerization process can lead to the formation of crosslinked networks between the CMC, TA molecules and PAA polymer chains. This can result in the formation of a three-dimensional structure frame work with potentially altered properties compared to the original CMC and AA. At the same time AA can generate ester bonds by reacting with -OH on the cellulose backbone of CMC. This reaction can result in the incorporation of acrylic acid moieties into the CMC polymer chain.
3.1. Solvent resistance
The solvent resistance of elastomers[26], or the capacity of elastomeric materials to endureexposure to various solvents, is of great importance in many industries and applications. Elastomers are commonly used in applications where they come into contact with different chemicals, such as in seals, gaskets, O-rings, and hoses. Solvents can have varying chemical compositions and properties, and some solvents may cause swelling, degradation, or other adverse reactions in elastomers. Solvent resistance ensures that the elastomer remains chemically compatible, allows for longer service life, and reduces the need for frequent replacements or repairs.By selecting the appropriate solvent-resistant elastomer for a specific application, industries can enhance reliability, efficiency, and safety in their operations.
Table 1 shows the soluble fraction (%) of CMC/PAA/TA in different solvents. As seen in Table 1, CMC/PAA/TAelastomer has high resistance to solvent such as acetone, benzene, HCl, and DMF. About 5.45% was soluble in HNO3 and 14% was soluble in ethanol aftersoaking for two weeks.It clear that from the obtained data, the prepared elastomer possesses high resistivity to many deferent type of solvents as shown from the table.
Table (1): Soluble fraction (%) after two weeks of CMC/PAA/TA in different solvents
Solvents
|
weight dry
(g)
|
weightsoaking
(g)
|
soluble fraction
(%)
|
Acetone
|
1.17
|
1.19
|
~ 0
|
Benzene
|
1.08
|
1.07
|
0.92
|
Nitric acid
|
1.1
|
1.04
|
5.45
|
Hydrochloric acid
|
1.07
|
1.05
|
1.86
|
N,N-Dimethylformamide
|
1.21
|
1.22
|
~ 0
|
Ethanol
|
1.07
|
0.92
|
14
|
3.2. XRD analysis
Figure (2) depicts the XRD pattern of CMC/PAA/TA. The diffractogram reflected the amorphous structure of the prepared CMC/PAA/TA elastomer has a broad peak at 2θ = 22.0o. A diffraction peak at 28.0o, which confirmed some crystallinity in the polymeric structure that may be due to the arrangement on the crystal domain.
3.3. Flame retardant of the prepared elastomer
Limiting oxygen index LOI is the lowest oxygen percentage in an oxygen-nitrogen mixture that is just enough to enable combustion of the specimen following ignition, indicating the capacity of materials to tolerate fire.[27]. The higher the LOI values, the greater the capacity to withstand fire and the more difficult it is to ignite materials. The flammability properties of CMC/PAA/TAelastomer is examined by LOI. It was found that the elastomer has a LOI value of 30%. Because TA has a strong carbon-forming ability and anti-oxidant capacity, its presence improves the flame retardancy of CMC/PAA/TA elastomer [48].
3.4. FT-IR analysis
FTIR spectra of CMC/PAA/TA elastomer before and after exposure to 1864 kGy of gamma rays were investigated in Figure (3). One of the prominent spectral characteristics found in the CMC/PAA/TA FTIR spectrum is a band centered at 3040 cm− 1, due to O-H stretching vibrations of carboxylic group(Fig. 3A). The asymmetric stretching vibrations of C-H appears at 2931 cm− 1[28, 29], which confirmed by the bending vibration band at 1042 cm−1.The band at 1735 cm− 1due to C = O stretching vibrations[30].The splitting pattern of C = O may be related to the influence of hydrogen bonds. The band at 1138 cm− 1 is caused by C-O stretching vibrations in ether linkages between aromatic rings in lignin. The intensity of the O-H and -CH bands increased while C = O decreased after exposure to 1864 kGy of gamma rays for CMC/PAA/TA (Fig. 3B), which may be due to a little degradation in the matrix [31].
3.5. Thermal properties of prepared elastomer
Figure 4 shows of CMC/PAA/TA before and after exposure to 1864 kGy of gamma rays. Under a nitrogen atmosphere, the specimens were tested at temperatures ranging from 30oC to 600oC at a constant rate of 20oC/min.The TGA curves reveal that all specimens had three separate stages of weight reduction. The first stage of the thermogram of CMC/PAA/TA (Fig. 4A) shows the evaporation of partially physically bound water at 200.60 oC, whereas the second stage at 282.77 oC shows the disintegration of CMC and PAA side chains. The final stage, at 395.97 oC, reveals the disintegration of the polymer's primary chain. For CMC/PAA/TA after exposure to 1864 kGy of gamma rays (Fig. 4B), the same behavior was observed. A negligible change was observed that means the CMC/PAAc keep its thermal characteristic after exposure to gamma rays up to1864 kGy. It must be noted that the investigation of the influence of gamma radiation was chosen up to 1864 kGy only as a limited example for the study.
3.6. Mechanical properties
The mechanical properties of elastomers are of significant importance due to their direct impact on the performance and functionality of elastomeric materials in various applications. Elastomers should possess sufficient strength to withstand the loads and forces they encounter during use. An elastomer's tensile stress is commonly defined by its tensile strength, which is the greatest stress or force that the material can sustain before failing or breaking[32]. Elastomers are known for their high tensile strength. Elastomers often face challenges such as tearing due to contact with rough surfaces, sharp edges, or repeated friction. Good tear resistance ensures that elastomers can withstand the application-specific forces without developing cracks or ruptures. Young's modulus, also referred to as the modulus of elasticity, is an indicator of the stiffness or rigidity of a material. Young's modulus is an essential mechanical property in materials science and engineering as it helps engineers and designers understand and predict how materials will respond to applied forces. Elongation percent indicates the maximum amount of deformation a material can undergo before it breaks or fails. It is a measure of the material's ductility or ability to be drawn into a wire-like shape without breaking. The stress/strain curve of CMC/PAA/TA was examined in Fig. 5, and Table 2 summarizes the data. CMC/PAA/TA displayed good mechanical properties,, as indicated in Table, where the tensile strength is ~ 3.376 MPa, Yong's Modules is ~ 0.595 MPa, tear strength is 33.754 N/mm, and the elongation percent is ~ 501.689%.The mechanical properties of CMC/PAA/TA after exposure to gamma rays at an irradiation dose of 1864 kGy were investigated as obtained in Fig. 6 and the analyzed data was performed in Table 3. As explained in Table 3, the tensile strength is ~ 3.087 MPa, Yong's Modules is ~ 0.606 MPa, the tear strength is 30.87 N/mm, and the elongation percent is ~ 468.461%. The result is considered excellent, CMC/PAA/TA elastomer kept good mechanical properties after exposure to a high radiation dose, 1864 kGy. This means the CMC/PAA/TA elastomer resists the gamma radiation at least up to the studied value
Table (2): Mechanical properties data of CMC/PAA/TA
No.
|
Force @ Peak (N)
|
Elong. @ Peak (mm)
|
Elong. @ break(mm)
|
Tensile Stress
(MPa)
|
Yong's Modules
(MPa)
|
Tear strength
(N/mm)
|
Elong. @ break(%)
|
1
|
88.358
|
84.451
|
85.377
|
3.465
|
0.475
|
34.65
|
569.178
|
2
|
97.107
|
74.65
|
75.657
|
3.597
|
0.601
|
35.966
|
504.383
|
3
|
80.664
|
72.289
|
73.504
|
3.227
|
0.556
|
32.265
|
490.027
|
4
|
80.339
|
64.198
|
66.475
|
3.214
|
0.748
|
32.136
|
443.167
|
Maximum
|
97.107
|
84.451
|
85.377
|
3.597
|
0.748
|
35.966
|
569.178
|
Minimum
|
80.339
|
64.198
|
66.475
|
3.214
|
0.475
|
32.136
|
443.167
|
Mean
|
86.617
|
73.897
|
75.253
|
3.376
|
0.595
|
33.754
|
501.689
|
Table (3) Mechanical properties data of CMC/PAA/TA after exposure to gamma rays at irradiation dose of 1864 kGy.
No.
|
Force @ Peak (N)
|
Elong. @ Peak (mm)
|
Elong. @ break(mm)
|
Tensile Stress
(MPa)
|
Yong's Modules
(MPa)
|
Tear strength
(N/mm)
|
Elong. @ break(%)
|
1
|
77.801
|
69.611
|
70.867
|
3.112
|
0.554
|
31.121
|
472.444
|
2
|
56.317
|
61.215
|
63.661
|
2.537
|
0.76
|
25.368
|
424.407
|
3
|
84.695
|
69.014
|
70.485
|
3.388
|
0.595
|
33.878
|
469.9
|
4
|
82.787
|
75.56
|
76.064
|
3.311
|
0.515
|
33.115
|
507.091
|
Maximum
|
84.695
|
75.56
|
76.064
|
3.388
|
0.76
|
33.878
|
507.091
|
Minimum
|
56.317
|
61.215
|
63.661
|
2.537
|
0.515
|
25.368
|
424.407
|
Mean
|
75.400
|
68.85
|
70.269
|
3.087
|
0.606
|
30.87
|
468.461
|
It can be noted that the resistance of CMC/PAA/TA elastomer to gamma radiation where it mainly keeps its properties through the investigated radiation dose, 1864 kGy. The reasons of this behavior may due to the chemical structure of the elastomer; the tightly bonded molecular structures tend to be more resistant to radiation. Also, the highly cross-linked structure makes the material more stable and less susceptible to radiation-induced degradation. The inclusion of TA in the matrix may enhance the radiation resistance due to stearic hindrance of catechol groups of its structure. TA is considered as antioxidant and radical scavenger [33], which can scavenge free radicals generated by radiation, preventing them from causing chain scission or other forms of degradation. By comparing the obtained properties data ofCMC/PAA/TA elastomer with acrylic rubber (ACM) properties[34–36], it can be noted that CMC/PAA/TA superior properties, particularly chemical and physical strength, and flame resistance. Additionally, when compared with ACM elastomer lacks gamma radiation protection and fire retardant properties.