Impact of γ-irradiation and SBR content in the compatibility of aminated (PVC/LLDPE)/ZnO for improving their AC conductivity and oil removal

In some cases, blends containing PVC and LLDPE show low compatibility. Adding styrene-butadiene rubber to the PVC/LLDPE mixtures leads to a noticeable increase in tensile strength and compatibility of the blends. Also, an improvement in tensile strength is observed after incorporating SBR compatibilizer resulting in entirely different gamma irradiation doses. Without a compatibilizer, the mixture exhibits a distributed PVC and LLDPE phase with variable sizes and shapes; even a sizable portion of the domains resemble droplets. Styrene butadiene rubber (SBR) and gamma radiation make mixtures of (PVC/LLDPE) more compatible. The SEM study of the blends demonstrated that adding the compatibilizer resulted in finer blend morphologies with less roughness. At the same time, gamma irradiation reduced this droplet and gave a more smooth surface. Poly(vinyl chloride) (PVC) was chemically modified with four different amino compounds, including ethylene diamine (EDA), aniline (An), p-anisidine (pA) and dimethyl aniline (DMA) for improving the electric conductivity and oil removal capability of the blend polymer. All ionomers were prepared by nucleophilic substitution in a solvent/non-solvent system under mild conditions. This work novelty shows a sustainable route for producing oil adsorption materials by recycling plastic waste. After the amination process of poly(vinyl chloride) the oil adsorption was significantly enhanced.

The manufacturing of irradiated recycled (PVC/LLDPE)-ZnO blend. The waste PVC and LDPE are soaked in silicon oil and heated for 3 h. the aim of this step is to remove any excess filler and pigment that could be presented in the waste plastic. The color of silicon oil changed, and the resultant particles were pelletized after melting. The pelletizing of PVC and LLDPE was finally dried in the oven at 50 °C for approximately 12 h. The components of PVC, LLDPE, SBR, and ZnO were manually premixed in a container; Table 1 lists the actual formulation of the samples. An extruder with twin screws was used in a melting-mixing process to create all of the blends. The temperatures from the hopper to the die were maintained at 160-290 °C, and the screw speed was kept at roughly 200 rpm. The samples were extruded and then placed in a heated mold to produce a sheet of (PVC/LLDPE)ZnO samples. The obtained sample was exposed to (0, 10 and 20) kGy of gamma radiation. www.nature.com/scientificreports/ AC conductivity. LCR bridge model Hioki 3532 was used to measure the sample (PVC/LLDPE)/ZnO impedance Z and the phase angle between the applied AC voltage and the resulting current in the samples of irradiated and chemical modified (PVC/LLDPE)ZnO for AC conductivity measurement σAC(ω). The frequency ranged from Hz to 600 Hz. The variation in AC conductivity with a frequency at ambient temperature on an ln-ln scale. The impedance Z, sample capacitance Cp, and loss tangent Tanδ were measured using a programmable automatic 3532 LCR meter. The resistance R was parallel to all values of capacitance Cp was taken from the bridge's screen. The equation was used to calculate the total conductivity σt (w).
where L is the distance between the two electrodes (the sample thickness), Z is the sample's impedance, and A is the cross-sectional area of the sample. Using the relation, the AC conductivity σAc(w) is calculated as follows: where σ DC (w) is termed as the DC conductivity.
Gamma (γ) irradiation. Films were irradiated by γ-radiation with range doses (0, 10, 20) kGy, using a Co 60 source of γ-radiation. The gamma irradiator is housed in a shielding building that is constructed upon a ground of standard density concrete (2.36 g/cc), with a thickness of about 120 cm, so that no one receives more than 10 mR of radiation during 40 h/week, or the maximum dose rate would not exceed 0.2 mR on all accessible when 1,000,000 curie cobalt radiation source is utilized.
Simulation procedure of electric field distribution. Starting with the cable's copper core and moving outward to its outer semiconductor layer, the electric field distribution was investigated. A steady 2Uo = 24 kV 50 Hz AC power supply was applied to the cable layers (Uo is the cable's rated line to neutral voltage). The effects of electric fields were then studied using COMSOL Multiphysics. In this work, a single-core 22 kV insulated underground cable was the compression sample. The analysis uses the copper conductor with a radius of 4.165 mm, the inner semiconductor with a diameter of 4.95 mm, the insulator with a diameter of 10.45 mm, and the extrinsic semiconductor with a diameter of 11.25 mm. All radii have been calculated starting from the copper conductor's center.
Characterization. Using an Intron mechanical testing machine, specimens' tensile characteristics in the dumbbells' shape were measured under ASTM D638 (model 5569). A 10 mm/min crosshead speed was used to measure the tensile strength and elongation. Using a Mettler Toledo 823e DSC, differential scanning calorimetry was used to measure the glass transition temperature (Tg) (Mettler Toledo International Inc., USA). In aluminum pans, samples weighing about 10 mg were preheated between 100 and 190 °C at a rate of 10 °C/min with an isothermal hold period of two minutes at 190 °C. Samples were then cooled to 100 °C once more and then heated to 100 °C at a rate of 5 °C/min. As a guide, an empty pan was used. Before the runs, liquid nitrogen was utilised to chill the samples. Infrared spectroscopy using the Fourier transform (FTIR) FTIR research was conducted utilising a Bomem-MB102 spectrometer (ABB-Bomem, USA). The spectrum was recorded between 4000 and 650 cm1 with a 4 cm-1 resolution. With a 10 kV accelerating voltage, a SEM (JSM-7500F, JEOL, Japan) was used to observe the morphology of dynamic fatigue fracture of SBR. The specimens were treated with gold spraying before being observed and then adhered to the conductive tapes. The Philips PW 1830 diffractometer was used to carry out the XRD. The X-ray beam was operated at 40 kV and 30 mA with nickel-filter Cu K (= 0.1541 nm) radiation. From 5 to 85, corresponding data were gathered in 0.02 step increments. One method is Fourier-transform infrared spectroscopy (FTIR/ATR) to produce an infrared spectrum of solid samples.

Results and discussions
Effect of irradiation dose and SBR content as the compatibilizer of PVC and LLDPE. This article investigated the SBR influence and gamma irradiation doses on the compatibility of PVC and LLDPE compounds. Irradiations of immiscible blend polymers are mainly compatibilized after irradiation 21 . Numerous studies have shown that γ-rays penetrate deeper and produce radicals that trigger cross-linked processes. Compared with E-Beam radiation, γ-ray has higher penetration power [22][23][24][25] . The negative charge particles of E-Beam radiation limit its penetration power [26][27][28][29][30] .
Morphological Properties of irradiated (PVC/LLDPE)ZnO blends. Figure 1 displays how the gamma radiation doses and SBR content affect the compatibility of PVC and LLDPE. Differing SBR compatibilizer concentrations produce completely distinct morphologies. Without a compatibilizer, the mixture exhibits a dispersed PVC and LDPE phase with variable sizes and shapes; even a sizable portion of the domains resemble droplets. SBR compatibilizers resulted in PVC domains with common conditions and essentially consistent measures. The compatibilizers employed have a significant impact on the PVC domain sizes. It is generally acknowledged that a compatibilizer plays two critical roles in managing a blend's morphology: coalescence prevention and interfacial tension reduction. Due to the compatibilizers' role in steric stability, it is assumed that the homogeneity of the PVC domains' size and shape generated by their addition results from a decrease in coalescence. The blank samples (0 kGy) contain more droplet matrix with more cavities, as seen in Fig. 1. The blends' SEM analysis showed that the SBR compatibilizer's addition and the irradiation method produced finer blend morphologies with less roughness. In PVC/LLDPE blends, the SBR compatibilizer reduced droplet coalescence and aided in stabilising fine morphology. The compatibility between LLDPE and PVC matrixes was significantly improved www.nature.com/scientificreports/ by the SBR compatibilizer level of 3 wt%. Additionally, gamma irradiation slightly improves compatibility rather than just the SBR impact. The coalescence of recently produced droplets becomes more significant when SBR concentration increases.
Mechanical properties of irradiated (PVC/LLDPE)ZnO blends. Due to their low interphase adhesion and high interfacial tension, PVC and LLDPE form incompatible combinations, as reported in several academic publications [31][32][33] . The mechanical properties of PVC and LLDPE are almost inferior 33 and can be improved by the SBR addition and gamma irradiation process. Figure 2 demonstrates how the SBR and irradiation processes improve the blends' tensile strength and elongation. This result is due to the increased compatibility of PVC with LLDPE. Based on ASTM standards, a stress test was plotted in Fig. 2a on different contents of SBR compatibilizer and gamma irradiation doses. The force strength of (PVC/LLDPE)ZnO samples is enhanced after adding SBR and exposure to gamma radiation than blank samples. The compatibilizer (SBR) has a good effect on interfacial bonding after the irradiation process and increases the force strength of the (PVC/LLDPE)ZnO blends. The addition of SBR increases the force strength and exhibits superior material strength after gamma irradiation due to gamma irradiation-induced crosslinking of SBR 34 . In Fig. 2b the elongation (mm) is increase about 21%, 30% and 52% with SBR content increase from 1%, 2% and 3% at 0 kGy, respectively. This difference is due to the SBR chains made plasticizer effect in blends sample. Based on the definition of plasticization, the elongation should increase with an increase in the plasticizer concentration [35][36][37][38] . After the gamma irradiation process, the elongation is decreased. For example, at 3% SBR the elongation decreased from 11 to 16.8% for irradiation doses at

Amine-functionalized of PVC in irradiated (PVC/LLDPE)/ZnO blend. Poly(vinyl chloride) (PVC)
was chemically modified with four different amino compounds, including ethylene diamine (EDA), aniline (An), p-anisidine (pA) and dimethyl aniline (DMA) for improving the electric conductivity and oil removal capability of the blend polymer. The chemical structure and the proposed mechanism of PVC amination are represented in Fig. 3. After amination reactions, all samples of modified (PVC/LLDPE)ZnO-b exhibit coloration degree varying from brown to dark brown. All ionomers were prepared by nucleophilic substitution in a solvent/non-solvent system at mild conditions (Table 1) 41 . This dechlorination process is responsible for forming short polymeric chains containing C=O and -CH=CH-moieties. As irradiation of (PVC/LLDPE)ZnO-b progresses, the formation of the C=O and -CH=CH-becomes noticeably significant. Therefore, FTIR spectroscopy was used to examine the growth of the absorption peaks corresponding to the C=O and -CH=CH-groups www.nature.com/scientificreports/ two peaks located at 1566 cm -1 and 820 cm -1 are assigned to bending vibration of (N-H) and (C-N) bonds, respectively. The peak located at 1330 cm -1 corresponds to the stretching vibration of (C-N) bonds in PVC/ LLDPE)ZnO-EDA sample. In addition, the broad beak located at 3410 cm -1 corresponds to the starching vibration of (N-H) in primary amine. The broadening peak of 3410 cm -1 is due to the intramolecular hydrogen bonds excited between NH 2 groups, as represented in Fig. 3b. Also, the broad peak of 3410 cm -1 confirms the in situ cross-linked reactions take placed in PVC/LLDPE)ZnO-EDA sample. Figure 4c shows the characteristic peaks   Figure 4d shows the characteristic FTIR peaks of (PVC/LLDPE)ZnO-pA located at 1609 cm -1 and 1047 cm -1 that assignment to the stretching and bending vibration of C-O and N-H bonds in p-anisidine molecules. Figure 4e show the characteristic FTIR peaks of (PVC/LLDPE) ZnO -DMA located at 1223 cm -1 that assignment to the stretching vibration of C-N of tertiary amine and 1612 cm -1 that that assignment to the stretching vibration of C=C of a benzene ring with no NH peak observed for dimethyl aniline molecules. Figure 5a shows the XRD pattern of virgin LLDPE in the blank sample of (PVC/LLDPE)ZnO-b has appeared at 20.51° and 23.18°, which are assigned to the 110 and 200 reflections of LLDPE. At the same time, the XRD pattern of virgin PVC film at 2θ ~ 17° and 26° does not appear. This could be due to the gamma irradiation that may cause dechlorination (-HCl) of PVC molecules 42 Figure 5b-e shows the XRD pattern of (PVC/ LLDPE)ZnO-b modified chemically by the nucleophilic substitution process. Compared to Fig. 1a, the intensities of the diffraction peaks significantly changed after chemical modification. Figure 3b shows the XRD peaks of (PVC/LLDPE) ZnO -EDA sample that almost exhibit only two peaks at 7.02° and 17.3°. Figure 5c shows the XRD peaks of (PVC/LLDPE)ZnO-An, which show the sharp characteristic peaks of aniline molecules with high crystallinity at 16.38°2 9 . www.nature.com/scientificreports/ effect of compatibilizing agent (SBR) as a plasticizer, limiting the glassy temperature of PVC 43 . Figure 6b shows the DSC curve of (PVC/LLDPE) ZnO -EDA sample that exhibited a peak abroad at 82 °C, corresponding to the moisture content. The results indicated that amination reactions by EDA is an effective method to increase the hydrophilicity of PVC. In addition, the increased melting point (310 °C) of (PVC/LLDPE) ZnO-EDA sample is due to the intramolecular H bonds established after chemical modification as confirmed by FTIR data. Figure 4 c-d exhibit the DSC of the three ((PVC/LLDPE)ZnO-An, (PVC/LLDPE) ZnO-pA and (PVC/LLDPE) ZnO-DMA)) samples with single Tg at the temperature of (98, 88 and 95) °C, respectively. PVC has Tg at a temperature of 93.5 °C according to the DSC data found in the literature [44][45][46] . This fact reinforces the plasticizing effect induced by p-anisidine, especially the percent of 5 w% of ZnO it could increase the Tg when it acts as a filler 47,48 . Furthermore, when aniline and N, N, dimethyl aniline were reacted with PVC molecules caused an increase in their Tg due to the restriction on the free rotation and hence restricted segmental motion 49 Fig. 7b. All of these modified structural parameters seem to be influenced by oil adsorption capacity. This highlights that the distribution of amine sites on the adsorbents is critical to high castor oil adsorption performance. Figure 7c highlights that the aromatic benzene ring in (PVC/LLDPE)ZnO-DMA gives hydrophobic sites on the surface of the adsorbent is critical to the high performance of motor oil adsorption and water repellent.

The XRD analysis of modified (PVC/LLDPE)ZnO.
The electric conductivity of aminated modified PVC. Figure 8a represents the electrical conductivity irradiated blank (PVC/LLDPE)ZnO-b and modified aminated sample. It is observed that the (PVC/LLDPE) ZnO-pA blend had higher electrical conductivity than other samples at any given frequency despite the increased electrical conductivity of the PVC with the increase in frequency. The increase in the modfied blend's conductivity could be attributed to the formation of amine sites which may be in the protonation state. The protonation is chemically formed intermolecular and intramolecular H-bonds as an inorganic doping process: the protonated of amine groups is known to be more conducting due to a high degree of conjugation. The permittivity ε' and dielectric loss ε" for aminated modified PVC samples were represented in Fig. 8b,c over a frequency range 0.01 Hz up to 600 Hz. The measurements were carried out at room temperature (25 ± 1 °C). From Fig. 8b This increase in ε' & ε" with the incorporation amino groups is due to the rise in dipoles-dipoles interactions and intramolecular H bonds which leads to an increase in the orientation polarization and also to the presence of interfacial polarization. The blend plastic used to manufacture medium voltage cables has many advantages like a low dissipation factor of about 0.03% at 20 °C, a low dielectric constant of 2.2-2.5, good thermo-mechanical properties and a high operating temperature of about 90 °C 50 . The aged samples show increasing dielectric constant and dielectric loss 51 . In our samples, dielectric loss is more minor for neat samples (PVC/LLDPE)ZnO-b. After chemical modification, the dielectric loss is increased without the aging process. It means that the existence of nanoparticles 52 and amine sites on the sample blend will increase dielectric loss. Therefore it is possible to postulate that chemical modification will increase the dielectric constant and dielectric loss.
Simulation and modeling of electric field distribution of aminated modified PVC. The cable was a single core 22 kV shielded underground medium voltage cable. COMSOL Multiphysics was used to simulate the electric field distribution in Medium Voltage Cables in this study. The electric field distribution has been studied, starting from the copper core to the outer semiconductor layer of the cable. Figure 9a shows that at 1 mm of arc length, the distribution of the electric field inside (PVC/LLDPE)ZnO-b sample marked cables is non-uniform. For (PVC/LLDPE)ZnO-pA sample, as shown in Fig. 9b the electric field distribution is starting to become uniform and gradually decreases from the inside to the outside. This is because the p-anisidine filled (PVC/LLDPE)ZnO-pA sample preserves a uniform electrical field and reduces electrostatic tension, increasing relative permittivity values for inner semiconductors and outer semiconductors from 2.05 to 2. 23 www.nature.com/scientificreports/

Conclusions
The amination of a non-functional PVC matrix was performed using a simple chemical reaction process between four different amine reagents and PVC to develop an adsorbent for oil removal from aqueous phases. PVC and LLDPE blends were successfully compatibilized by SBR with ionizing irradiation, namely gamma irradiation in the dose of 0, 10 and 20 kGy. The tensile and stress tests indicated a remarkable improvement in mechanical properties after the gamma irradiation process with increasing SBR content. In particular, the elongation (mm) is increase about 21%, 30% and 52% with SBR content increase from 1%, 2% and 3% at 0 kGy, respectively. The use of SBR prevents the aggregate formation and the ZnO domain is a remarkably uniform distribution, thus indicating a better particle dispersion. The FT-IR and XRD results confirm the aminated characteristics of the (PVC/LLDPE)ZnO. DSC revealed decreased Tg of PVC and a decrease in their melting points with the degree of crystallinity of (PVC/LLDPE)ZnO blends due to the formation of less perfect crystals resulting from the amination modification of PVC. At the same time, the melting point of LLDPE is split into two peaks due to the presence of both irradiated and non-irradiated regions, providing two LLDPE regions. The modified blends show a significant enhancement of oil removal compared to the unmodified sample. The electrical conductivity of modified blends increases with the frequency. The increase in electrical conductivity of the target polymer, PVC, is mostly due to the dehydrochlorination process (Supplementary Video S1).

Data availability
The data that support the findings of this study are available from the corresponding author upon reasonable request. www.nature.com/scientificreports/