A Comprehensive Study of Structural, Thermal, and Dielectric Properties of Melt-Processed Polypropylene/ Ni 0.9 Zn 0.1 Fe 2 O 4 Nanocomposites

: This article explores the processing of structural, thermal, and dielectric properties of polypropylene (PP) polymer nanocomposites modified with Ni 0.9 Zn 0.1 Fe 2 O 4 . The PP/Ni 0.9 Zn 0.1 Fe 2 O 4 nanocomposites are manufactured by the melt-processing method using a Brabender Polyspeed B. The XRD and FTIR structural investigations assure good incorporation of Ni 0.9 Zn 0.1 Fe 2 O 4 into the PP matrix. It should be noted that adding Ni 0.9 Zn 0.1 Fe 2 O 4 NPs to the PP polymer matrix enhances the polymer’s thermal stability. Utilizing the Coats–Redfern model, kinetic thermodynamic parameters such as activation energy (Ea), enthalpy ( ∆ H), entropy ( ∆ S), and Gibbs free energy ( ∆ G*) are deduced from TGA data. The dielectric results showed an increase in ε (cid:48) with the introduction of nanoparticles into the PP matrix. As the content of Ni 0.9 Zn 0.1 Fe 2 O 4 NPs in these nanocomposite films increases, the loss tangent values decrease at higher frequencies while increasing at lower frequencies. The estimated ε s and ε ∞ of PP nanocomposites using Cole–Cole plots reveal an improvement when NPs are added to PP. We believe that the proposed work suggests a relevant step towards the practical application of PP/Ni 0.9 Zn 0.1 Fe 2 O 4 nanocomposites.


Introduction
The thermal, mechanical, and electrical properties of polymer nanocomposites have generated great interest in academic research [1][2][3][4].Polymer nanocomposites can have enhanced thermal stability, improved heat resistance, and higher thermal conductivity.The thermal conductivity of polymer nanocomposites can be increased by the addition of nanoparticles with high thermal conductivity, such as graphene, carbon nanotubes, or metal particles.Surprisingly, even small amounts of nanofillers can revolutionize the properties of polymer composites compared to pure polymer [5][6][7][8][9].Therefore, polymer nanocomposites have found wide application in many fields, including electromagnetic shielding, charge storage capacitors, microwave absorbers [10][11][12], EM detectors [13], optical integrated circuits, sensors, medical devices, aerospace, packaging materials, consumer goods, and so on [14].Various scientific methodologies can be used to adapt the physical properties of polymeric nanomaterials for a specific application.The physical and chemical properties of polymer nanocomposites are related to the shape, size, and content of the nanoparticles [15][16][17][18][19][20][21][22][23][24].Since it offers amazing properties that can be used in catalysis, biomedicine, high-density information storage devices, transformer cores, electromagnetic interference (EMI) suppressors, rod antennas, gas detecting, and environmental remediation, nano-ferrite is subject to substantial research [25][26][27][28][29].
Polypropylene (PP) is readily available and cost-effective from refineries across the world.Its low density makes it easy to process using melt-processing methods [30][31][32][33].
Furthermore, its high chemical resistance makes PP ideal for packaging, automobiles, and other applications [34][35][36].Therefore, scientists have been actively studying polypropylene nanocomposites to enhance the physical properties of pure PP [35,[37][38][39][40][41][42][43][44][45][46][47][48][49][50][51][52][53][54].There are research works related to the preparation and investigation of thermal and dielectric properties of polypropylene nanocomposites.This is an active area of research with great potential for developing new materials with improved properties.Siddiqui et al. [40] successfully manufactured new magnetic bionanocomposites of graphene bonded to magnetically modified polypropylene (as the polymer matrix).The overall conductivity of the composites was significantly improved.Rheological experiments demonstrated that increasing the nanofiller concentration led to an enhancement of viscoelastic characteristics, exhibiting more solid-like behavior.The dispersion of the nanofillers within the PP matrix created conductive connections, resulting in innovative PP/MCNC composites with an 800% increase in shielding efficiency compared to pure PP.Bendaoued et al. [43] demonstrated that nanofillers were synthesized using the sol-gel process and incorporated as fillers in polypropylene composites to enhance the thermal, rheological, and interfacial compatibility of the final material.The addition of nano-TiO 2 improved the thermal degradation stability of polypropylene.The results revealed that incorporating nano-TiO 2 into the polypropylene matrix increased the degree of crystallinity.Due to its superior thermal and viscoelastic properties, including high storage and loss moduli and degree of crystallinity, the nanocomposite PP@5% TiO 2 is a suitable candidate for application in the manufacture of recycled wind turbine blades.Rishaban et al. [42] referred to the significantly improved mechanical and thermal stability of the created polymer/multi-layered graphene nanocomposites.P. Tambe et al. [32] demonstrated that the NaOH-treated halloysite nanotubes (H.N.Ts) are superior fillers for reinforcing the PP matrix.This modification is cost-effective for the industry because NaOH is available in large quantities at a lower cost than other synthetic organic modifiers.In comparison to clean PP and H.N.Ts-filled PP nanocomposites, the mechanical characteristics enhancement is greatest for the 3 wt.%NaOH-treated H.N.Ts-filled PP nanocomposites.Uo Uyor et al. [39] studied the mechanical, thermal, and dielectric properties of sandwich-structured BN-BaTiO 3 -BN/PP nanocomposites.Hydrothermal and assembly processes were used to create the BN-BaTiO 3 -BN sandwich nanoparticles.A rheometer prepared the nanocomposites using the melt compounding process.The prepared PP nanocomposites exhibited improved thermal properties above 20 • C. Additionally, the dielectric constant increased by nearly 132%, from 2.02 at 100 Hz for pure PP to 4.68 for PP/5BN-15BT nanocomposite.Moreover, the nanocomposite maintained a low loss of approximately 0.05 at 100 Hz.L.G. Furlan et al. [38] discussed the role of processing conditions on the thermal and mechanical properties of PP nanocomposites.Using a co-rotating twin-screw extruder, polypropylene montmorillonite (PP-MMT) nanocomposites were fabricated.Their findings demonstrated that a medium shear intensity profile, as opposed to a high one, produced a greater improvement in mechanical properties.The dispersion and interaction of MMT particles within the PP matrix influenced the reinforcement effect.Patil et al. [35] studied the mechanical and thermal properties of polypropylene (PP)/multiwall carbon nanotubes (MWCNTs) nanocomposites.They fabricated the nanocomposites using compression molding equipment.The mechanical and thermal behavior of the nanocomposites was then evaluated using ASTM standards.The results revealed that adding MWCNTs to the PP matrix enhanced both mechanical and thermal properties.The highest tensile strength (62.80%) was measured at 1.2 wt.% MWCNT loading.At 1.5 wt.%, impact strength and hardness increased by 82.14% and 12.44%, respectively.However, low weight percent increases were accompanied by subsequent drops in glass transition temperature.
The addition of Ni 0.9 Zn 0.1 Fe 2 O 4 nanoparticles as a nanofiller to a polypropylene (PP) polymer matrix can have significant impacts on the structure, thermal, and dielectric properties of the resulting composite material.Ni 0.9 Zn 0.1 Fe 2 O 4 nanoparticles exhibit ferrimagnetic behavior [55], possess high thermal stability [56], and have higher dielectric constants [57] compared to the polymer matrix.Therefore, the introduction of Ni 0.9 Zn 0.1 Fe 2 O 4 nanoparticles can improve the thermal stability and dielectric constant of the composite.
The mechanisms by which nanoparticles influence the thermal and dielectric properties of polymers are still not fully understood.Further research is needed to elucidate these mechanisms, which will enable the rational design of nanocomposites with desired properties.Therefore, in current research, PP/Ni 0.9 Zn 0.1 Fe 2 O 4 nanocomposites were synthesized using the melt-processing method.The aim of this research is to investigate the effect of adding Ni 0.9 Zn 0.1 Fe 2 O 4 nanoparticles (NPs) to the PP matrix on the structural, thermal, and dielectric properties.XRD and FTIR analysis to confirm the dispersion and interaction between the NPs and the polymer.The addition of NPs has improved the thermal resistance of the polymer, potentially leading to applications in high-temperature environments.Using TGA data and the Coats-Redfern model, the activation energy, enthalpy, entropy, and Gibbs free energy associated with the thermal degradation process were determined.The introduction of NPs influences the dielectric constant (ε') and loss tangent of the material.By analyzing the Cole-Cole plots, the static and high-frequency permittivities (ε s and ε ∞ ) of the nanocomposites were estimated, potentially leading to advancements in electrical insulation or dielectric materials.

Sample Preparation and Characterization Techniques
According to Reference [58], Ni 0.9 Zn 0.1 Fe 2 O 4 nanoparticles were synthesized using the green sol-gel autocombustion process.Nanocomposites composed of PP and Ni 0.9 Zn 0.1 Fe 2 O 4 nanoparticles were then successfully fabricated via the melt-processing technique.The ratios of Ni 0.9 Zn 0.1 Fe 2 O 4 were 0.0, 5.0, 10, and 15 wt%, as shown in Table 1.The PP and nanoparticles were pre-dried to remove any moisture that could affect the processing and final properties of the nanocomposite.A Brabender Polyspeed B was the specific type of internal mixer used to mix the molten polymer with the nanoparticles under controlled temperature and pressure.After mixing, the molten mixture was shaped into disk shapes using a compression molding technique.The nanocomposites were stored in a desiccator to minimize moisture absorption before characterization.Structural analyses of the prepared nanocomposites were conducted using a Bruker AXS D8 Advance diffractometer (Berlin, Germany) equipped with CuKα radiation (λ = 0.154060 nm) and a collimator size of 480 µm.A high-performance FE-SEM Quanta FEG 250 provided high-resolution imaging and analysis of the polymer nanocomposite morphology.High-resolution imaging of materials and particle size at the nanoscale was achieved using a JEM-2100 instrument (JEOL Ltd., Tokyo, Japan).Functional group identification, molecular composition determination, and investigation of chemical bonding within the polymer nanocomposites were performed using a JASCO FT/IR-6100 (JASCO, Tokyo, Japan) spectrometer.Thermogravimetric analysis (TGA) of a polymer nanocomposite was conducted using an SDT Q600 TGA/DSC (TA Instruments, New Castle, DE, USA) analyzer with a heating rate of 10 • C/min.The dielectric properties of the polymer nanocomposites were recorded over a wide frequency range (20 Hz-2.0 MHz) using a Keysight E4980 LCR meter (Octopart, New York, NY, USA).The thickness of the composite samples was 2.0 mm.The electrodes were coated with gold and had an across-section area of 3.14 cm 2 .The samples were pre-dried to remove moisture prior to dielectric properties measurements.[63,64].Furthermore, the shift of major Ni 0.9 Zn 0.1 Fe 2 O 4 nanoparticle peaks in the nanocomposite diffraction patterns towards lower angles due to crystal lattice changes confirms the successful formation of PP nanocomposites.Ni 0.9 Zn 0.1 Fe 2 O 4 nanoparticles in polypropylene matrix induce strain in the lattice due to a mismatch in thermal expansion or processing stresses.This strain disrupts atomic arrangement, increasing interplanar spacing and shifting diffraction peaks to lower angles.Moreover, as the concentration of nanoparticles increases in the nanocomposite, the probability of interaction and stress transfer between the nanoparticles and the polymer matrix also increases.This can lead to a more pronounced lattice strain in the nanoparticles, resulting in a larger peak shift at higher weight percentages [65].Some of the major peaks are indexed with Miller indices, as shown in the figure .achieved using a JEM-2100 instrument (JEOL Ltd., Tokyo, Japan).Functional group identification, molecular composition determination, and investigation of chemical bonding within the polymer nanocomposites were performed using a JASCO FT/IR-6100 (JASCO, Tokyo, Japan) spectrometer.Thermogravimetric analysis (TGA) of a polymer nanocomposite was conducted using an SDT Q600 TGA/DSC (TA Instruments, New Castle, DE, USA) analyzer with a heating rate of 10 °C/min.The dielectric properties of the polymer nanocomposites were recorded over a wide frequency range (20 Hz-2.0 MHz) using a Keysight E4980 LCR meter (Octopart, New York, NY, USA).The thickness of the composite samples was 2.0 mm.The electrodes were coated with gold and had an across-section area of 3.14 cm 2 .The samples were pre-dried to remove moisture prior to dielectric properties measurements.110), ( 040), ( 130), ( 111), ( 131), (060), and (220), respectively [44,[59][60][61][62].The XRD patterns of PP/Ni0.9Zn0.1Fe2O4nanocomposites reveal the predominant peaks of PP along with additional peaks at 36°, 43°, 57.26°, and 62.90°, indicating the presence of Ni0.9Zn0.1Fe2O4nanoparticles within the nanocomposites and confirming the formation of PP/Ni0.9Zn0.1Fe2O4nanocomposite films [63,64].Furthermore, the shift of major Ni0.9Zn0.1Fe2O4nanoparticle peaks in the nanocomposite diffraction patterns towards lower angles due to crystal lattice changes confirms the successful formation of PP nanocomposites.Ni0.9Zn0.1Fe2O4nanoparticles in polypropylene matrix induce strain in the lattice due to a mismatch in thermal expansion or processing stresses.This strain disrupts atomic arrangement, increasing interplanar spacing and shifting diffraction peaks to lower angles.Moreover, as the concentration of nanoparticles increases in the nanocomposite, the probability of interaction and stress transfer between the nanoparticles and the polymer matrix also increases.This can lead to a more pronounced lattice strain in the nanoparticles, resulting in a larger peak shift at higher weight percentages [65].Some of the major peaks are indexed with Miller indices, as shown in the figure.XRD peak broadening in PP/Ni 0.9 Zn 0.1 Fe 2 O 4 polymer nanocomposites can be attributed to several factors related to the size and strain of the crystalline phases, as well as the presence of multiple phases.According to the Scherrer equation, smaller crystallites diffract X-rays less efficiently, leading to broader peaks in the XRD pattern.This broadening effect becomes more pronounced as the crystallite size in both the PP matrix and the Ni 0.9 Zn 0.1 Fe 2 O 4 nanofillers decreases.Strain within the crystal lattice caused by imperfections, dislocations, or interfacial stresses between the PP and Ni 0.9 Zn 0.1 Fe 2 O 4 phases can also broaden the XRD peaks.The presence of non-uniform phases or mixed phases within the nanocomposite can contribute to peak broadening.This can arise from incomplete mixing of the PP and Ni 0.9 Zn 0.1 Fe 2 O 4 components [66].

FTIR Analysis
One of the suitable techniques for studying such changes in these nanocomposite films is FTIR spectroscopy.Figure 2 illustrates the corresponding FTIR spectra within the range of 4000-400 cm −1 wavenumber for PP and its nanocomposites modified with different ratios of 5, 10, and 15 wt% Ni 0.9 Zn 0.1 Fe 2 O 4 NPs.All spectra were quite similar, with each displaying the characteristic peaks of PP [44,[67][68][69].In the spectrum of PP, the vibrations of asymmetric CH 3 , asymmetric CH 2 , stretching CH 3 , symmetric bending CH 3 , rocking CH 3 or wagging CH, rocking CH 3 or stretching C-C, rocking CH 3 or rocking CH, and stretching C-C were attributed to the peak locations detected at wavenumbers of 2949, 2916, 2867, 1454-1375, 1165, 997, 972, 840, and 807 cm −1 , respectively [67].
tributed to several factors related to the size and strain of the crystalline phases, as well as the presence of multiple phases.According to the Scherrer equation, smaller crystallites diffract X-rays less efficiently, leading to broader peaks in the XRD pattern.This broadening effect becomes more pronounced as the crystallite size in both the PP matrix and the Ni0.9Zn0.1Fe2O4nanofillers decreases.Strain within the crystal lattice caused by imperfections, dislocations, or interfacial stresses between the PP and Ni0.9Zn0.1Fe2O4phases can also broaden the XRD peaks.The presence of non-uniform phases or mixed phases within the nanocomposite can contribute to peak broadening.This can arise from incomplete mixing of the PP and Ni0.9Zn0.1Fe2O4components [66].

FTIR Analysis
One of the suitable techniques for studying such changes in these nanocomposite films is FTIR spectroscopy.Figure 2 illustrates the corresponding FTIR spectra within the range of 4000-400 cm −1 wavenumber for PP and its nanocomposites modified with different ratios of 5, 10, and 15 wt% Ni0.9Zn0.1Fe2O4NPs.All spectra were quite similar, with each displaying the characteristic peaks of PP [44,[67][68][69].In the spectrum of PP, the vibrations of asymmetric CH3, asymmetric CH2, stretching CH3, symmetric bending CH3, rocking CH3 or wagging CH, rocking CH3 or stretching C-C, rocking CH3 or rocking CH, and stretching C-C were attributed to the peak locations detected at wavenumbers of 2949, 2916, 2867, 1454-1375, 1165, 997, 972, 840, and 807 cm −1 , respectively [67].In the spectra of PP nanocomposites, additional peaks appear at wavenumbers of 1645 and 460 cm −1 , which were assigned to the N-H band and octahedral complexes of the spinel cubic structure, respectively [58,63].These extra peaks, observed in the nanocomposites, confirm the incorporation of Ni0.9Zn0.1Fe2O4NPs in the PP matrix, in agreement with the XRD results.The peak at 1645 cm −1 is assigned to the N-H stretching vibration of adsorbed amine groups on the polypropylene matrix interacting with the Ni sites in the spinel.This suggests that there is a chemical bonding interaction between the amine groups on the polypropylene and the Ni atoms in the NPs.This type of interaction can lead to improved compatibility and dispersion of the NPs within the matrix, enhancing the mechanical and physical properties of the composite material.The peak at 460 cm −1 is assigned to the Fe-O vibrations in the octahedral sites of the spinel structure.The presence of Zn dopant ions can potentially affect these vibrations, leading to a shift in the peak position or intensity.This suggests that the Zn dopant ions may be influencing the local In the spectra of PP nanocomposites, additional peaks appear at wavenumbers of 1645 and 460 cm −1 , which were assigned to the N-H band and octahedral complexes of the spinel cubic structure, respectively [58,63].These extra peaks, observed in the nanocomposites, confirm the incorporation of Ni 0.9 Zn 0.1 Fe 2 O 4 NPs in the PP matrix, in agreement with the XRD results.The peak at 1645 cm −1 is assigned to the N-H stretching vibration of adsorbed amine groups on the polypropylene matrix interacting with the Ni sites in the spinel.This suggests that there is a chemical bonding interaction between the amine groups on the polypropylene and the Ni atoms in the NPs.This type of interaction can lead to improved compatibility and dispersion of the NPs within the matrix, enhancing the mechanical and physical properties of the composite material.The peak at 460 cm −1 is assigned to the Fe-O vibrations in the octahedral sites of the spinel structure.The presence of Zn dopant ions can potentially affect these vibrations, leading to a shift in the peak position or intensity.This suggests that the Zn dopant ions may be influencing the local bonding environment around the Fe atoms in the NPs.This could, in turn, affect the interaction between the NPs and the polypropylene matrix.

TEM Microscopy
TEM image and electron diffraction of a selected area of Ni 0.9 Zn 0.1 Fe 2 O 4 NPs are shown in Figure 3.As shown in the figure, nanoparticles have a spherical shape with an average crystal size of 29 nm, and some appear as dark regions due to the agglomeration of nanoparticles.Agglomeration is caused by the magneto-static interaction between particles.
Furthermore, the agglomeration phenomenon can be explained as nanoparticles having a permanent magnetic moment, which is directly proportional to their volume [58,70].
teraction between the NPs and the polypropylene matrix.

TEM Microscopy
TEM image and electron diffraction of a selected area of Ni0.9Zn0.1Fe2O4NPs are shown in Figure 3.As shown in the figure, nanoparticles have a spherical shape with an average crystal size of 29 nm, and some appear as dark regions due to the agglomeration of nanoparticles.Agglomeration is caused by the magneto-static interaction between particles.Furthermore, the agglomeration phenomenon can be explained as nanoparticles having a permanent magnetic moment, which is directly proportional to their volume [58,70].We compared the information obtained from electron diffraction (Figure 3b) with the bulk crystallographic data obtained from XRD.This showed a confirmation of the crystal structure obtained from XRD.

FESEM Microscopy
Figure 4 illustrates the FESEM images of PP/Ni0.9Zn0.1Fe2O4nanocomposite films to investigate the morphology of the nanocomposites.The FESEM micrographs show a good distribution of Ni0.9Zn0.1Fe2O4nanoparticles within the PP matrix, although some agglomeration is present.The appearance of agglomeration in the FE-SEM results (yellow circles) agrees well with the TEM results shown in Figure 3a.This suggests a good interaction between the Ni0.9Zn0.1Fe2O4and the PP polymer matrix, confirming the formation of nanocomposites.This finding is consistent with the XRD and FTIR results [63,64].We compared the information obtained from electron diffraction (Figure 3b) with the bulk crystallographic data obtained from XRD.This showed a confirmation of the crystal structure obtained from XRD.

TEM Microscopy
TEM image and electron diffraction of a selected area of Ni0.9Zn0.1Fe2O4NPs are shown in Figure 3.As shown in the figure, nanoparticles have a spherical shape with an average crystal size of 29 nm, and some appear as dark regions due to the agglomeration of nanoparticles.Agglomeration is caused by the magneto-static interaction between particles.Furthermore, the agglomeration phenomenon can be explained as nanoparticles having a permanent magnetic moment, which is directly proportional to their volume [58,70].We compared the information obtained from electron diffraction (Figure 3b) with the bulk crystallographic data obtained from XRD.This showed a confirmation of the crystal structure obtained from XRD.

FESEM Microscopy
Figure 4 illustrates the FESEM images of PP/Ni0.9Zn0.1Fe2O4nanocomposite films to investigate the morphology of the nanocomposites.The FESEM micrographs show a good distribution of Ni0.9Zn0.1Fe2O4nanoparticles within the PP matrix, although some agglomeration is present.The appearance of agglomeration in the FE-SEM results (yellow circles) agrees well with the TEM results shown in Figure 3a.This suggests a good interaction between the Ni0.9Zn0.1Fe2O4and the PP polymer matrix, confirming the formation of nanocomposites.This finding is consistent with the XRD and FTIR results [63,64].[63,71].As the nanoparticle loading increases (10 wt% and 15 wt%), the interfacial interaction between the nanoparticles and the polypropylene matrix becomes more significant compared to low loadings (5 wt%).This interaction can act as a barrier to the diffusion of volatile decomposition products, hindering the degradation process and leading to an increase in peak temperature.In comparison to pure PP, the addition of nanoparticles in the polymer matrix improved the thermal characteristics of polymer nanocomposite, as listed in Table 2.The high crosslinking density and secondary connections conferred upon Ni 0.9 Zn 0.1 Fe 2 O 4 NPs with the polymer chains can be attributed to the enhancement of the thermal stability of the nanocomposites.Also, the incorporation of nanoparticles into the polymer matrix restricted polymer chain movement, reduced free radical exchange and hence decreased heat degradation [63,72].

Thermogravimetric Analysis
Figure 5 presents TGA/DTG plots of PP/Ni0.9Zn0.1Fe2O4nanocomposite films.It is clear that each curve exhibits a single degradation stage with a peak temperature within the range of 467-499 °C.The peak temperature is slightly affected by the addition of Ni0.9Zn0.1Fe2O4NPs to the PP matrix.As the Ni0.9Zn0.1Fe2O4NPs concentration increases, the mass losses of PP/Ni0.9Zn0.1Fe2O4nanocomposite films decrease, which is consistent with previous research [63,71].As the nanoparticle loading increases (10 wt% and 15 wt%), the interfacial interaction between the nanoparticles and the polypropylene matrix becomes more significant compared to low loadings (5 wt%).This interaction can act as a barrier to the diffusion of volatile decomposition products, hindering the degradation process and leading to an increase in peak temperature.In comparison to pure PP, the addition of nanoparticles in the polymer matrix improved the thermal characteristics of polymer nanocomposite, as listed in Table 2.The high crosslinking density and secondary connections conferred upon Ni0.9Zn0.1Fe2O4NPs with the polymer chains can be attributed to the enhancement of the thermal stability of the nanocomposites.Also, the incorporation of nanoparticles into the polymer matrix restricted polymer chain movement, reduced free radical exchange and hence decreased heat degradation [63,72].The degree of conversion (α) can be used to express the reaction rate using the following Equation (1) [73]: where m i , m f , and m t are the initial, final, and current sample mass at the instant t.
The Coats-Redfern approximation method is a powerful tool for analyzing thermogravimetric analysis (TGA) data, particularly in the context of studying thermal decomposition processes [6,[74][75][76][77][78][79].Therefore, we use this method to determine the kinetics parameters of the TGA thermal decomposition stage shown in Figure 5.
where E a , R, A, and ϕ are the activation energy, the real gas constant, the reaction rate constant, and the heating rate, respectively.Equation ( 2) states that straight-line results from versus 1000 T with a slope and intercept directly proportional to the E a and A, respectively as depicted in Figure 6.Estimated activation energies of the nanocomposites are reduced as Ni 0.9 Zn 0.1 Fe 2 O 4 NPs are added, indicating that Ni 0.9 Zn 0.1 Fe 2 O 4 NPs have a significant impact on the PP.Additionally, the following well-known formulae [78,80,81] were used to compute the changes in entropy (∆S*), enthalpy (∆H*), and Gibbs free energy (∆G*) of the activation: where T p is the peak temperature of the DTG curve, k B is the Boltzmann constant, and h is the Plank constant.Entropy (∆S * ) and enthalpy (∆H * ) provide information on the system's level of order, total thermal motion, and Gibbs or free energy (∆G * ) provides information on the stability of the system.The degree of conversion (α) can be used to express the reaction rate using the following Equation (1) [73]: where , , and  are the initial, final, and current sample mass at the instant .The Coats-Redfern approximation method is a powerful tool for analyzing thermogravimetric analysis (TGA) data, particularly in the context of studying thermal decomposition processes [6,[74][75][76][77][78][79].Therefore, we use this method to determine the kinetics parameters of the TGA thermal decomposition stage shown in Figure 5.
where Ea, R, A, and  are the activation energy, the real gas constant, the reaction rate constant, and the heating rate, respectively.Equation ( 2) states that straight-line results from plotting  − ( ) versus with a slope and intercept directly proportional to the  and A, respectively as depicted in Figure 6.Estimated activation energies of the nanocomposites are reduced as Ni0.9Zn0.1Fe2O4NPs are added, indicating that Ni0.9Zn0.1Fe2O4NPs have a significant impact on the PP.Additionally, the following wellknown formulae [78,80,81] were used to compute the changes in entropy (ΔS*), enthalpy (ΔH*), and Gibbs free energy (ΔG*) of the activation: where Tp is the peak temperature of the DTG curve, kB is the Boltzmann constant, and h is the Plank constant.Entropy (ΔS * ) and enthalpy (ΔH * ) provide information on the system's level of order, total thermal motion, and Gibbs or free energy (ΔG * ) provides information on the stability of the system.The values of the computed thermodynamic parameters (E a , ∆S * , ∆H * , and ∆G * ) are listed in Table 3 in accordance with the Coats-Redfern method.It is evident that as the Ni 0.9 Zn 0.1 Fe 2 O 4 NP concentrations rise, the values of all thermodynamic parameters fall.This can be explained by noting that when NPs rise, random macromolecule chain scission prevails in polymeric matrices, and activation energy decreases.Additionally, each sample has negative entropy, indicating ordered systems and potentially more ordered activated states that could result from the chemisorption of other light sources.The values of E a , ∆S * , ∆H * , and ∆G * in our work are less than in [74].

Dielectric Measurements
Figure 7 illustrates the frequency dependence of the real dielectric constant (ε ) of PP and its nanocomposites at room temperature in the frequency range 20 Hz ≤ f ≤ 2 MHz.Over most of the frequency range studied, the dielectric constants of the polymer nanocomposites were almost frequency-independent.Polarizations relate to the PP matrix, Ni 0.9 Zn 0.1 Fe 2 O 4 NPs, and PP-NPs interfaces in this study, although the nonpolar character of PP may have a major effect on the tiny dielectric response at the applied frequency range.Some polymer nanocomposites have previously shown the same characteristic [39,[82][83][84].The dependence of ε on Ni 0.9 Zn 0.1 Fe 2 O 4 NPs concentration exhibited an enhancement with rising NP concentrations for weight ratios ranging from 0 to 15 wt%.This strong dependence of ε on nanofiller concentration has already been found for nanocomposites [63,64,[85][86][87][88][89][90][91].The good interaction between NPs and the PP matrix is confirmed via such behavior.Basically, it can be attributed to the formation of microcapacitor networks in the PP matrix as the content of the nanofiller rises.The accumulation of charge carriers in the interior surface of the PP matrix may also be the cause of this increase, as shown by the Maxwell-Wagner-Sillars effects [64,92,93].The 15 wt% modified film has a lower dielectric constant than other nanocomposite films, which could be because of cluster formation [6]. Figure 8 shows the variation in dielectric loss (log(ε″)) with angular frequency log(ω) for PP/Ni0.9Zn0.1Fe2O4nanocomposites films at room temperature.Generally, every specimen behaves in the same way as depicted, decreasing as frequency rises and then increasing at higher frequencies.The minimum dielectric loss shifts to higher frequencies as Ni0.9Zn0.1Fe2O4Nps content increases.Equation 6 [94] gives the frequency-dependence re- Figure 8 shows the variation in dielectric loss (log(ε )) with angular frequency log(ω) for PP/Ni 0.9 Zn 0.1 Fe 2 O 4 nanocomposites films at room temperature.Generally, every specimen behaves in the same way as depicted, decreasing as frequency rises and then increasing at higher frequencies.The minimum dielectric loss shifts to higher frequencies as Ni 0.9 Zn 0.1 Fe 2 O 4 Nps content increases.Equation (6) [94] gives the frequency-dependence relationship of ε : where where ε s , ε ∞ , n, N, e, k β , T, τ o , and W m , are static permittivity, infinity permittivity, number of electrons, the concentration of localized sites, elementary charge, Boltzmann's constant, absolute temperature, relaxation time, the energy required to move an electron from one site to the infinite, and angular frequency.By applying this model to our results and fitting a portion of the data in the frequency range of 20 Hz to 84 kHz to a linear equation, we may find the values of W m presented in Table 3.Generally, the values of W m tabulated in Table 3 are greater than those of PVC/NiO (0.025-0.027 eV) [92] but lower than those of Polyester/Ni 0.5 Zn 0.5 Fe 2 O 4 (0.16-0.43 eV) [64], and their values grew as the Ni 0.9 Zn 0.1 Fe 2 O 4 Nps concentration increased.The variation in the tangent loss (tan(δ)) of PP loaded with different weight ratios of Ni0.9Zn0.1Fe2O4NPs at room temperature in the frequency range 20 Hz to 2 MHz is displayed in Figure 9.The measured values of tan(δ) of PP nanocomposites are frequencydependent at all frequency ranges, as can be seen.For PP, the tangent loss initially has high values at low frequencies and rapidly decreases as the frequency rises to 4226 Hz; thereafter, the tangent loss increases.Tan(δ) for the PP is consistent with the strong conductivity at high frequencies associated with charge carrier hopping or tunneling [63,64].The trendlines of the nanocomposites feature two regions: the first region shows a decrease in tan (δ) with frequency due to a reduction in dielectric dispersion or because the nanocomposite films' crystallinity has improved [95], while the second region exhibits an increase in loss tangent with frequency.The nanocomposite films' minimal loss tangents are, respectively, at 0.6325, 1.416, and 1.5 MHz and 5, 10 and 15 wt%.The variation in the tangent loss (tan(δ)) of PP loaded with different weight ratios of Ni 0.9 Zn 0.1 Fe 2 O 4 NPs at room temperature in the frequency range 20 Hz to 2 MHz is displayed in Figure 9.The measured values of tan(δ) of PP nanocomposites are frequencydependent at all frequency ranges, as can be seen.For PP, the tangent loss initially has high values at low frequencies and rapidly decreases as the frequency rises to 4226 Hz; thereafter, the tangent loss increases.Tan(δ) for the PP is consistent with the strong conductivity at high frequencies associated with charge carrier hopping or tunneling [63,64].The trendlines of the nanocomposites feature two regions: the first region shows a decrease in tan (δ) with frequency due to a reduction in dielectric dispersion or because the nanocomposite films' crystallinity has improved [95], while the second region exhibits an increase in loss tangent with frequency.The nanocomposite films' minimal loss tangents are, respectively, at 0.6325, 1.416, and 1.5 MHz and 5, 10 and 15 wt%.Ni0.9Zn0.1Fe2O4NPs at room temperature in the frequency range 20 Hz to 2 MHz is displayed in Figure 9.The measured values of tan(δ) of PP nanocomposites are frequencydependent at all frequency ranges, as can be seen.For PP, the tangent loss initially has high values at low frequencies and rapidly decreases as the frequency rises to 4226 Hz; thereafter, the tangent loss increases.Tan(δ) for the PP is consistent with the strong conductivity at high frequencies associated with charge carrier hopping or tunneling [63,64].The trendlines of the nanocomposites feature two regions: the first region shows a decrease in tan (δ) with frequency due to a reduction in dielectric dispersion or because the nanocomposite films' crystallinity has improved [95], while the second region exhibits an increase in loss tangent with frequency.The nanocomposite films' minimal loss tangents are, respectively, at 0.6325, 1.416, and 1.5 MHz and 5, 10 and 15 wt%.   3 are obtained by fitting these semicircles.According to Table 3, the values of ε ∞ and ε s for films made of PP/Ni 0.9 Z 0.1 Fe 2 O 4 nanocomposites are greater than those of PP, confirming that the addition of NPs increased the dielectric constant of PP.
. 2024, 8, x FOR PEER REVIEW 12 of 18 The Cole-Cole curves of PP/Ni0.9Z0.1Fe2O4nanocomposite films at room temperature are revealed in Figure 10.The semicircle on each Cole-Cole graph represented relaxation processes.As a result, the values of static permittivity (εs), infinity permittivity (ε∞), and dielectric intensity (Δε) that are given in Table 3 are obtained by fitting these semicircles.According to Table 3, the values of ε∞ and εs for films made of PP/Ni0.9Z0.1Fe2O4nanocomposites are greater than those of PP, confirming that the addition of NPs increased the dielectric constant of PP.The values of Z' fall with frequency and attain nearly minimal constant values at high frequencies, which can be explained in part by charge carrier hopping or tunneling.The polymer nanocomposite films' improved crystallinity, which results in less hopping interchain and intrachain ion movements, caused the inclusion of nanoparticles to also provide an improvement in Z' values [99].
Ni 0.9 Z 0.1 Fe 2 O 4 is a spinel ferrite with good electrical conductivity due to the presence of mixed valence states (Fe 2+ and Fe 3+ ) and the hopping mechanism of charge carriers.When incorporated into the PP matrix, it creates conductive pathways, reducing the overall impedance of the composite and thereby increasing Z'.Meanwhile, the interface between the Ni 0.9 Z 0.1 Fe 2 O 4 nanoparticles and the PP matrix creates an additional layer with unique electrical properties.This interfacial region can exhibit polarization under an applied electric field, contributing to the overall impedance response and potentially increasing Z'.Moreover, the presence of Ni 0.9 Z 0.1 Fe 2 O 4 nanoparticles can trap mobile ions and electrons within the PP matrix, preventing them from accumulating at the electrode interfaces.This reduces space charge buildup, which can contribute to leakage current and lower Z' values [100].The values of Z' fall with frequency and attain nearly minimal constant values at high frequencies, which can be explained in part by charge carrier hopping or tunneling.The polymer nanocomposite films' improved crystallinity, which results in less hopping interchain and intrachain ion movements, caused the inclusion of nanoparticles to also provide an improvement in Z' values [99].

Conclusions
The successful synthesis of PP/Ni 0.9 Zn 0.

Figure 1
Figure 1 demonstrates the XRD spectra of polypropylene doped with Ni 0.9 Zn 0.1 Fe 2 O 4 nanoparticles at different weight ratios: 0.0, 5.0, 10, and 15 wt%.The diffraction pattern of PP exhibits characteristic peaks at 14.11 • , 16.78 • , 18.47 • , 19.84 • , 21.10 • , 21.84 • , and 25.21 • , corresponding to the lattice planes of the monoclinic crystals of (110), (040), (130), (111), (131), (060), and (220), respectively [44,59-62].The XRD patterns of PP/Ni 0.9 Zn 0.1 Fe 2 O 4 nanocomposites reveal the predominant peaks of PP along with additional peaks at 36 • , 43 • , 57.26 • , and 62.90 • , indicating the presence of Ni 0.9 Zn 0.1 Fe 2 O 4 nanoparticles within the nanocomposites and confirming the formation of PP/Ni 0.9 Zn 0.1 Fe 2 O 4 nanocomposite films[63,64].Furthermore, the shift of major Ni 0.9 Zn 0.1 Fe 2 O 4 nanoparticle peaks in the nanocomposite diffraction patterns towards lower angles due to crystal lattice changes confirms the successful formation of PP nanocomposites.Ni 0.9 Zn 0.1 Fe 2 O 4 nanoparticles in polypropylene matrix induce strain in the lattice due to a mismatch in thermal expansion or processing stresses.This strain disrupts atomic arrangement, increasing interplanar spacing and shifting diffraction peaks to lower angles.Moreover, as the concentration of nanoparticles increases in the nanocomposite, the probability of interaction and stress transfer between the nanoparticles and the polymer matrix also increases.This can lead to a more pronounced lattice strain in the nanoparticles, resulting in a larger peak shift at higher weight percentages[65].Some of the major peaks are indexed with Miller indices, as shown in the figure.

Figure 1
Figure1demonstrates the XRD spectra of polypropylene doped with Ni0.9Zn0.1Fe2O4nanoparticles at different weight ratios: 0.0, 5.0, 10, and 15 wt%.The diffraction pattern of PP exhibits characteristic peaks at 14.11°, 16.78°, 18.47°, 19.84°, 21.10°, 21.84°, and 25.21°, corresponding to the lattice planes of the monoclinic crystals of (110), (040), (130), (111), (131), (060), and (220), respectively[44,[59][60][61][62].The XRD patterns of PP/Ni0.9Zn0.1Fe2O4nanocomposites reveal the predominant peaks of PP along with additional peaks at 36°, 43°, 57.26°, and 62.90°, indicating the presence of Ni0.9Zn0.1Fe2O4nanoparticles within the nanocomposites and confirming the formation of PP/Ni0.9Zn0.1Fe2O4nanocomposite films[63,64].Furthermore, the shift of major Ni0.9Zn0.1Fe2O4nanoparticle peaks in the nanocomposite diffraction patterns towards lower angles due to crystal lattice changes confirms the successful formation of PP nanocomposites.Ni0.9Zn0.1Fe2O4nanoparticles in polypropylene matrix induce strain in the lattice due to a mismatch in thermal expansion or processing stresses.This strain disrupts atomic arrangement, increasing interplanar spacing and shifting diffraction peaks to lower angles.Moreover, as the concentration of nanoparticles increases in the nanocomposite, the probability of interaction and stress transfer between the nanoparticles and the polymer matrix also increases.This can lead to a more pronounced lattice strain in the nanoparticles, resulting in a larger peak shift at higher weight percentages[65].Some of the major peaks are indexed with Miller indices, as shown in the figure.

Figure 3 .
Figure 3. Images of (a) HRTEM and (b) electron diffraction of selected area for Ni 0.9 Zn 0.1 Fe 2 O 4 NPs.

Figure 4
Figure4illustrates the FESEM images of PP/Ni 0.9 Zn 0.1 Fe 2 O 4 nanocomposite films to investigate the morphology of the nanocomposites.The FESEM micrographs show a good distribution of Ni 0.9 Zn 0.1 Fe 2 O 4 nanoparticles within the PP matrix, although some agglomeration is present.The appearance of agglomeration in the FE-SEM results (yellow circles) agrees well with the TEM results shown in Figure3a.This suggests a good interaction between the Ni 0.9 Zn 0.1 Fe 2 O 4 and the PP polymer matrix, confirming the formation of nanocomposites.This finding is consistent with the XRD and FTIR results[63,64].

Figure 5
Figure 5 presents TGA/DTG plots of PP/Ni 0.9 Zn 0.1 Fe 2 O 4 nanocomposite films.It is clear that each curve exhibits a single degradation stage with a peak temperature within the range of 467-499 • C. The peak temperature is slightly affected by the addition of Ni 0.9 Zn 0.1 Fe 2 O 4 NPs to the PP matrix.As the Ni 0.9 Zn 0.1 Fe 2 O 4 NPs concentration increases, the mass losses of PP/Ni 0.9 Zn 0.1 Fe 2 O 4 nanocomposite films decrease, which is consistent with previous research [63,71].As the nanoparticle loading increases (10 wt% and 15 wt%), the interfacial interaction between the nanoparticles and the polypropylene matrix

Figure 7 .
Figure 7.The plot of ε against the frequency for PP/Ni 0.9 Zn 0.1 Fe 2 O 4 nanocomposites.

Figure 9 .
Figure 9.The frequency dependence of tan(δ) of PP/Ni 0.9 Zn 0.1 Fe 2 O 4 nanocomposites films.The Cole-Cole curves of PP/Ni 0.9 Z 0.1 Fe 2 O 4 nanocomposite films at room temperature are revealed in Figure 10.The semicircle on each Cole-Cole graph represented relaxation processes.As a result, the values of static permittivity (ε s ), infinity permittivity (ε ∞ ), and dielectric intensity (∆ε) that are given in Table3are obtained by fitting these semicircles.According to Table3, the values of ε ∞ and ε s for films made of PP/Ni 0.9 Z 0.1 Fe 2 O 4 nanocomposites are greater than those of PP, confirming that the addition of NPs increased the dielectric constant of PP.

Figure 12
Figure 12 depicts the variation in the AC impedance (Z') of the PP/Ni0.9Zn0.1Fe2O4nanocomposite within the frequency range of 20 Hz ≤  ≤ 2 MHz at room temperature.The values of Z' fall with frequency and attain nearly minimal constant values at high frequencies, which can be explained in part by charge carrier hopping or tunneling.The polymer nanocomposite films' improved crystallinity, which results in less hopping interchain and intrachain ion movements, caused the inclusion of nanoparticles to also provide an improvement in Z' values[99].

Figure 12 depicts
Figure 12 depicts the variation in the AC impedance (Z') of the PP/Ni 0.9 Zn 0.1 Fe 2 O 4 nanocomposite within the frequency range of 20 Hz ≤ f ≤ 2 MHz at room temperature.The values of Z' fall with frequency and attain nearly minimal constant values at high frequencies, which can be explained in part by charge carrier hopping or tunneling.The polymer nanocomposite films' improved crystallinity, which results in less hopping interchain and intrachain ion movements, caused the inclusion of nanoparticles to also provide an improvement in Z' values[99].Ni 0.9 Z 0.1 Fe 2 O 4 is a spinel ferrite with good electrical conductivity due to the presence of mixed valence states (Fe 2+ and Fe 3+ ) and the hopping mechanism of charge carriers.When incorporated into the PP matrix, it creates conductive pathways, reducing the overall impedance of the composite and thereby increasing Z'.Meanwhile, the interface between the Ni 0.9 Z 0.1 Fe 2 O 4 nanoparticles and the PP matrix creates an additional layer with unique

Figure 12
Figure 12 depicts the variation in the AC impedance (Z') of the PP/Ni0.9Zn0.1Fe2O4nanocomposite within the frequency range of 20 Hz ≤  ≤ 2 MHz at room temperature.The values of Z' fall with frequency and attain nearly minimal constant values at high frequencies, which can be explained in part by charge carrier hopping or tunneling.The polymer nanocomposite films' improved crystallinity, which results in less hopping interchain and intrachain ion movements, caused the inclusion of nanoparticles to also provide an improvement in Z' values[99].

Figure 12 .
Figure 12.The plot of the real part of AC impedance versus frequency of PP/Ni0.9Z0.1Fe2O4nanocomposites.

Figure 12 .
Figure 12.The plot of the real part of AC impedance versus frequency of PP/Ni 0.9 Z 0.1 Fe 2 O 4 nanocomposites.

1
Fe 2 O 4 nanocomposites was achieved and confirmed via structural techniques involving XRD, FTIR, and SEM.Further, TEM, XRD, and TEM findings revealed an average crystal size of approximately 29 nm for the Ni 0.9 Zn 0.1 Fe 2 O 4 nanoparticles.TEM images also confirmed the spherical morphology and lack of aggregation of the nanoparticles.FESEM micrographs demonstrated the successful incorporation of the Ni 0.9 Zn 0.1 Fe 2 O 4 NPs into the polymer matrix.TGA/DTG analysis showed improved thermal characteristics and reduced weight loss.However, the peak temperature range shifted between 468 and 499 • C upon introducing Ni 0.9 Zn 0.1 Fe 2 O 4 NPs.Kinetic and thermodynamic parameters, including activation energy, enthalpy, entropy, and Gibbs free energy, were determined from TGA/DTG data using the Coats-Redfern equation.Notably, the values of Ea, ∆S, ∆H, and ∆G* decreased with increasing Ni 0.9 Zn 0.1 Fe 2 O 4 content.Dielectric loss and AC impedance exhibited dependence on both frequency and composition.The real part of the complex permittivity (e') increased with the addition of Ni 0.9 Zn 0.1 Fe 2 O 4 NPs.Cole-Cole analysis revealed a single relaxation semicircle and provided values for ε s , ε ∞ , ∆ε , τ 0 , and f o .The combination of dielectric and magnetic properties of PP/Ni 0.9 Zn 0.1 Fe 2 O 4 nanocomposites suggests potential use in electromagnetic interference (EMI) shielding materials.Author Contributions: Conceptualization, T.A.M.T., M.T. and A.I.; methodology, T.A.M.T. and M.T.; formal analysis, T.A.M.T. and M.T.; investigation, T.A.M.T. and M.T.; resources, T.A.M.T., M.T. and A.I.; data curation, T.A.M.T., M.T. and A.I.; writing-original draft preparation, T.A.M.T., M.T. and A.I.; writing-review and editing, T.A.M.T., M.T. and A.I.; visualization, T.A.M.T., M.T. and A.I.; supervision, T.A.M.T., M.T. and A.I.; project administration, T.A.M.T., M.T. and A.I.; funding acquisition, T.A.M.T., M.T. and A.I.All authors have read and agreed to the published version of the manuscript.Funding: This research received no external funding. 3 •9H 2 O, M.W 404, ALPHA CHEMIKA, Maharashtra, India 99%), nickel nitrate AR (Ni(NO 3 ) 2 •6H 2 O, M.W 290.8, Nile Company, Cairo, Egypt, 99%), zinc nitrate AR (Zn(NO 3 ) 2 • 6 H 2

Table 2 .
TGA data of polypropylene loaded with Ni 0.9 Zn 0.1 Fe 2 O 4 .