INTRODUCTİON

As well as known the different sources of radiation can affect the characteristics of a nano-reinforced polymeric composite by inducing chain scission, cross-linking, free radical formation, and affecting the dispersion and alignment of nanoparticles in the polymer matrix. The extent of these effects depends on the type and intensity of radiation used, as well as the type of polymer and nanoparticles used in the composite. The effect of different sources of radiation on the characteristics of a nano-reinforced polymeric composite can vary depending on the type and intensity of radiation used. 1) Ionizing radiation: Ionizing radiation can cause chain scission and cross-linking of polymer chains, leading to changes in the mechanical, thermal, and electrical properties of the composite. The degree of cross-linking depends on the radiation dose and the type of polymer used. In nano-reinforced polymeric composites, ionizing radiation can also affect the dispersion and alignment of nanoparticles in the polymer matrix. 2) UV radiation: UV radiation can cause photodegradation of polymers, leading to a decrease in mechanical strength and toughness. In nano-reinforced polymeric composites, UV radiation can also affect the stability and dispersion of nanoparticles in the polymer matrix. 3) Gamma radiation: Gamma radiation can cause similar effects as ionizing radiation, but with higher energy levels. It can also induce free radical formation, which can lead to chain scission and cross-linking of polymer chains. In nano-reinforced polymeric composites, gamma radiation can affect the dispersion and alignment of nanoparticles in the polymer matrix, as well as their surface chemistry. 4) X-ray radiation: X-ray radiation can also cause chain scission and cross-linking of polymer chains, but with lower energy levels than gamma radiation. It can also induce free radical formation and affect the surface chemistry of nanoparticles in the polymer matrix [1]. The impact of these rays varies depending on the internal chemical composition of the material as well as its physical and mechanical properties [2-8]. In general, when polymeric compounds are subjected to radiation, one or both of the following processes take place, causing a change in their characteristics [9–14]: 

Crosslinking: This process causes molecules to join together, turning a solid material from flexible (ductile) to brittle.

Dissolution: In this process, ionization and irritation take place, and as a result, the primary polymer chain fissions. This process causes reduction of the molecular weight exponentially with radiation dose due to the disintegration.

 In order to understand the effect of radiation on the molecules of the material, this study intends to investigate the effects of several radiation sources (Co⁶⁰, Sr⁹⁰) on a polymeric composite supported by different proportions of nano-Alumina and its mechanical, structural, and spectral features (IR spectrum). 

MATERIALS AND METHODS 

The manual casting procedure was utilized to construct the polymeric composite models, beginning by preparing the basic materials that would be used in their production.

Matrix Material

Unsaturated Polyester Resin manufactured by the Saudi Company (SIR) was used for this purpose. Polyester resins are thermosetting polymers and readily polymerize at ambient temperature. By adding specific reinforcing elements (fibers, wires, and powders), their characteristics can be enhanced [9]. Table 1 shows the characteristics of the unsaturated polyester used in the research mentioned by the manufacturer.

Reinforcement Materials

The first step: Alumina nanoparticles were used to reinforce the polymer with different proportions shown in Table 2. Whereas, the used alumina particles were prepared by (Allied High Tech) production company (USA), and the granular size was (50nm), density (3.97 gm/cm³), and melting point (2323K).

The second step: Prepare the molds according to (ASTM) standards as in the following:

• Create glass molds for the examinations being studied with dimensions that adhere to international standards, as stated in Table 3.

• Clean the molds well

• Then, dry the molds well.

The molds are painted from the inner surface with Vaseline to ensure they do not stick when pouring.

The third step: Models can be manufactured after the molds are completed by following several steps: -

a) Starting with an addition ratio of 0.4%, mix the polymer with the reinforcement phase, then stir with a glass rod to ensure homogeneity. Next, add the reinforcing material using the weight ratios shown in Table 2, continuing the stirring process. Finally, add the hardener using an addition rate of (2%), and thoroughly mix for no more than three minutes to prevent rapid hardening before casting the mold. It is important to note that mixing all the materials with the hardener and accelerator at once runs the risk of causing violent decomposition.

b) The is then covered for 24 hours to harden.

c) To finish the production process, place the samples into an oven set at less than 100 °C for 24 hours to perform the treatment process. Then, the irradiation was carried out for all the polymeric samples under the same conditions so that the model was left at a distance of (10) cm in the air and for a while (1,2,3) day, equivalent to a radiation dose for the Co⁶⁰ source of Gy / h (0.78,1.6,2.5), respectively. After that, the Sr⁹⁰ source was used to irradiate the samples with the same time range and radiation doses Gy / h (1.7, 2.1, 3.4). The samples are prepared to undergo all testing after the irradiation process.

Characterization

To determine the success of the manufactured models, the following examinations must be carried out.

Atomic Force Microscopy- AFM

Using an atomic force microscope, the topography of the surfaces (AA 3000 SPM) is to be studied and examined. This technology uses cutting-edge, sophisticated technical procedures to enlarge the image of the material’s surface. The AFM is characterized by the ability to magnify objects by up to (5×102–108) times and optical microscopy’s high resolving power of (0.1–1.0) nm [15]–[18]. Since it gives us incredibly exact data on surface roughness and grain size, atomic force microscopy is typically employed to measure a variety of physical parameters [19]–[23].

Fourier Transform Infrared spectroscopy- FTIR

An infrared spectrophotometer of Japanese origin (the FT-IR In infrared spectrophotometer Shimadzu 8400) was used to record the spectra. To conduct the examination, a powder of a drug was mixed with the sample to be analyzed by IR (KBr). The powder is formed into discs, after which the examination is carried out with a range of (400–4000) cm^-1.

Mechanical Testing

Because polymers function in dual ways having great strength while also being prone to deformation and impacted by environmental factors, the mechanical characteristics are among the most crucial ones that help people understand models made from polymer-based materials. The mechanical characteristics of molecules are influenced in one way or another by strong and secondary bonds. The following are the key mechanical tests being researched [24-28].

 Hardness Test (Brinell)

This is considered as one of the most fundamental mechanical tests, as hardness measures a material’s resistance to scratching or penetration. The hardness of the created models was measured using the rebound method with a Swedish hardness tester that could be programmed. These are displayed on the device screen employed for reading the average hardness values [29].

Impact Strength Testing

The Impact Strength Testing shows the strength of polymeric materials by calculating the energy required to break the sample under stress and at high speeds. The following relationship can express the Impact Strength [30].

Impact resistance = Energy required to break (KJ) / Cross-sectional area of the sample (m2)

An impact strength testing device manufactured by (Testing Machines INC, Amityville, New York) was used to conduct this test. The test was implemented at room temperature.

RESULTS AND DISCUSSION

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Effect of Irradiation on Atomic Force Microscopy

Figs. 1, 2, 3, and 4 depict the effects of radiation from both sources on the topography of the surface. When composite A was exposed to radiation from different sources, there was no difference in the effects on the rate of granular size distribution or the surface roughness, as depicted in Figs. 1 and 2. The effect of the (Sr⁹⁰) source on composite B was more substantial than the effect of the (Co⁶⁰) source on the same composite. Here, it was noticed that the roughness rate increased, while there was no discernible difference in the distribution of granular sizes after exposure to radiation from both sources as demonstrated in Figs. 3 and 4. 

The Effect of Irradiation with Different sources on the Infrared Spectrum

The data values in Table 4 show that time has a negative effect on the flexibility and dissociation of the polymer, as was observed when composite (A) was subjected to a dose of radiation for a variable duration, such as 1, 2, or 3 days. It was noted that on the first day of exposure of the composite to the radiation source (Sr⁹⁰) that the (OH) group appeared at the frequency (3545-3414) cm^-1 and the group (CH) appeared at the frequency (3064) cm^-1, while the exposure for one day to the source (Co⁶⁰) the (OH) group appeared at the frequency of (3545-3416) cm^-1 and the (CH) group disappeared. This indicates dissociation of the polymer as shown in Figs 5 and 6. On the second day, when the polymer composite (A) was exposed to a source (Sr⁹⁰), it was noticed that the (OH) group appeared at the frequency (3547-3412) cm^-1, while when the polymer was exposed to a source (Co⁶⁰), this group appeared as (3545-3416) cm^-1. In terms of beam intensity, the remaining bundles were all very similar. The (OH) group appeared on the third day at a frequency (3545-3419) cm^-1 when exposed to the source (Sr⁹⁰), whereas this group appeared at a frequency (3553-3414) cm^-1 when exposed to the cobalt source. This difference in band intensity was due to the creation of free radicals, interaction of the hydrogen ion with oxygen radicals, and subsequent formation of peroxides. 

According to Table 5, the dissociation process of the polymer composite (B) after exposure to both of the investigated sources differs noticeably. The appearance of the (CH) group as depicted in Figs. 7 and 8 as a result of the hydrogen ion’s dissociation and its association with the oxygen free radical, causes the polymer to break down. This is the same as what occurred when exposed to a cobalt source, but with different beam intensities. The key findings on the second day of exposure to both sources were the appearance of a group (CH) at the frequency (3063-3028) cm^-1 when exposed to a source (Sr⁹⁰), and the appearance of a group (CH) at the frequency (3063-3028) cm^-1 when exposed to a source (Sr⁹⁰) for the group (CH). 

Effect of irradiation with different sources on the hardness

Figs. 9 and 10 which show how irradiation with various sources affects the behavior of hardness also demonstrate a decrease in hardness values for both composites when the exposure time is extended at irradiation with (Sr⁹⁰) and (Co⁶⁰) sources. This can be explained by the fact that on the first day of exposure, the bonds between the molecules of the composite materials (A, B) were under tension, which causes an interpretation of the movement of these molecules. As a result, on the third day of exposure, the composite material was complicated and had high hardness values relative to the hardness of the models. The complicated material (dissolution of the polymeric chains) is caused by a decrease in the bonding forces between the molecules.

Effect of irradiation time on impact strength

The properties of the composites (A) and (B) are significantly impacted by exposure duration following irradiation with both sources, as illustrated in Figs. 11 and 12. Yet, the Impact (Sr⁹⁰) source had the most notable impact because it was consistently more effective than the cobalt source. As a result, it was observed that a given chemical can behave either as a material with great strength or as a malleable material, depending on the external factors influencing it. It was found that when exposed to both sources, a material that is brittle on day one may behave as a high-strength material that may bend plastically on day three. This is due to the fact that the breaking energy increases This agrees with the researcher [31].

CONCLUSION

All composites’ roughness and particle size distribution change as the radioactive source’s potency increases.

For varied irradiation durations of polymer-based composites, the infrared spectrum was changed by the irradiation, which resulted in the disappearance of the (CH) beam when exposed to a source of weak activity, such as (Co⁶⁰), as opposed a source of (Sr⁹⁰), which is highly effective.

When exposed to highly effective sources and with an increase in exposure time, the impact resistance of the composite improves and its hardness values decrease.

Increasing the percentage of nano powder addition to the composite improves the mechanical

Acknowledgments

I extend my thanks and appreciation to the laboratories of the Department of Physics, Chemistry, and Mechanical Engineering for assisting in accomplishing the requirements of this work.

CONFLICT OF INTEREST

The authors declare that there is no conflict of interests regarding the publication of this manuscript.