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Abstract

The ability of biodegradable materials to be miniaturized and degrade at specific rates when subjected to certain bacterium types and/or a given range of temperatures has led to a newly emerging technology: organic transient bioelectronics. In this work, the electrical characteristics of new natural composite materials are presented. Four types of natural lignocellulosic fibers were used with polypropylene: black pepper, sumac, pomegranate, and lemon. The composites were prepared as flat smooth sheets with thicknesses ∼1 mm. The dielectric constant and the ac conductivity of the prepared samples were determined for the frequency range of 1 KHz to 4 MH. All measurements were performed at room temperature and humidity utilizing parallel plate capacitor technique associated with high precision Hioki IM3536 LCR meter. The frequency response of the composites under study shows similar behavior to that of the pure sample but with various percentage increments. The dielectric constant shows that the consistent dispersion was highly affected by filler content specially at the low frequency side of the spectrum. The maximum recorded increment was around 55% for 30wt.% sumac samples at 1 KHz. The effect of larger filler loading concentration on the incremental change of the ac conductivity was more obvious at higher frequencies.

Keywords

Bio-materials lignocellulosic fibers electrical characteristics dielectric constant electrical conductivity sustainability

Introduction

As green technology and clean energy are becoming fundamental strategies in modern technology, many polymers and their biodegradable composites have been extensively considered and used in the fabrication and enhancing the properties of many electronic systems. The huge abundance of such polymers as well as the several merits they possess opened the door for researchers and manufacturers to exploit the possibilities of using them in new inventions and applications.^1–4 One of the main attractive features of biodegradable composites is the possibility to alter their properties based upon on the filler reinforcement being used to fulfill certain design requirements.^5–8 For example, adding conductive particles to the polymer will result in conductive composite that are widely used in developing wearable electronic devices that need to satisfy certain flexibility requirements. Such devices found many applications in the field of robotics, biomedical, and smart clothes.^9–13

Biodegradable composite materials are aimed to be utilized in various industrial applications where mechanical, physical as well as electrical characteristics are vital in achieving sustainable and successful functional green products. Such integrated features of the materials are responsible for composite behavior regarding deformations, geometrical stability and electrical features for more reliable energy storage materials and they are very important to be investigated for the biodegradable materials before implemented in various products as they will determine the functional requirements for a certain application.^14–20 Natural fibers possess in fact, great potential as reinforcement for different polymers to produce lignocellulosic-polymer composites with superior properties. The natural fibers, on the other hand, are mainly constituted of cellulose, hemicellulose, and lignin. Such constituents highly influence the fibers’ properties.^21–24 Non-structural constituents are also existed such as pectin, wax, and inorganic salts. However, existing of wax and pectin inclusions together with the hydroxyl groups in the natural fibers would weaken their bonding and wetting with the polymer matrices, leading to reduce their compatibility and limiting their use for reinforcement purposes.^21,25–30 Thus, several efforts have been focused on removing the wax and lignin from the fibers’ surfaces utilizing several chemical treatments to facilitate the bonding mission of the hydroxyl groups, or to introduce new coupling agents, and to stop the water absorption capability.

One of the very attractive features of biodegradable composite materials is their ability to degrade at specific controlled rates when subjected to appropriate conditions. This includes certain bacteria types, proper temperature degrees and suitable miniaturization. This feature leads to the newly emerging technology; organic transient bioelectronics.^1,31 The term transient reflects the need of such electronic devices to be built out of specially engineered materials that are programmed to decay within precise period when put to function. Whereas the term bioelectronics refers to that unlike the traditional solid-state silicon-based electronics, the semiconducting materials used are fabricated out of organic materials of living origin. The main expected advantages of bioelectronics systems are to be nontoxic, biocompatible, and biodegradable.^3,32,33 These added values make this new type of electronic systems found very important biomedical applications. Flexibility of the electronic devices in this case is of crucial importance to ensure matching with the structure of the subjected organ. Other fields of interest of transient electronics include, but not limited to, field effect transistors, bio-sensing and actuating, robotics, energy harvesting, and manufacturing of super capacitors.^34,35

On the other hand, the combination and synergy between various parameters on several electrical properties of the biodegradable composites would not only enhance evaluating such composite materials but can also validate their suitability for future sustainable cleaner production. This makes biodegradable composites possible alternative type of materials that can meet the future sustainable green product satisfaction attributes.^8,36–40 Moreover, the dielectric properties of different types of natural fibers and their biodegradable composites have been addressed by many researchers in the literature.^41–45 Among these natural fibers are jute yarn, bamboo, sisal, oil palm, and coconut coir.^42,44,46 In another study,¹² the dielectric characteristics of some of the widely spread natural leaves in the Mediterranean area were investigated. These include lemon leaves, loquat leaves, palm leaves and olive leaves. In all these studies the dielectric characteristics show the same trend; the dielectric constant increases as the filler loading increases and decreases as the applied frequency increases. Whereas the conductivity increases as both the filler loading and the frequency increase.⁴¹ used chicken feather fiber as reinforced fillers to fabricate composites using standard epoxy resin. The reported results show that the dielectric constant was inversely proportional to filler loading and to frequency. Table 1 represents summary of the main results of the electrical properties of some natural fiber reinforced composites.

Table 1.

Electrical property behavior of selected natural fiber reinforced composites under fiber loading and frequency variations.

Ref	Matrix/Filler	Frequency range	Parameters	Effect of increasing the filler content	Effect of increasing the frequency
[4]	Polypropylene/jute yarn	100 Hz to 2 MHz	Dielectric constant	Increased	Decreased
			Loss factor	Increased	Decreased
			Conductivity	Increased	Increased
[47]	Polypropylene/jute/bamboo	1 KHz to 1 MHz	Dielectric constant	Increased	Decreased
			Dissipation factor	Increased	Decreased
			Loss factor	Increased	Decreased
[48]	Polyester/sisal	5 Hz to 20 KHz	Dielectric constant	Increased	Decreased
			Dissipation factor	Increased	Decreased
			Conductivity	Increased	Increased
[41]	Epoxy resin/chicken feather	10 kHz to 5 MHz	Dielectric constant	Decreased	Decreased
[41]	Epoxy resin/chicken feather	10 kHz to 5 MHz	Resistivity	Increased	Decreased
[49]	Polyethylene/sisal	5 Hz to 13 MHz	Dielectric constant	Increased	Decreased
[49]	Polyethylene/sisal	5 Hz to 13 MHz	Resistivity	Decreased	Decreased
[46]	Polyethylene/oil palm	1 KHz	Dielectric constant	Increased	Fixed frequency
[42]	Polypropylene/coconut coir (untreated)	Fixed	Dielectric constant	Increased	Fixed frequency
[44]	Oil palm biomass and biochar	0.2 GHz–10 GHz	Dielectric constant	Studied for fiber alone	Decreased
[12]	Lemon leaves, loquat leaves, palm leaves, olive leaves	10 Hz to 8 MHz	Dielectric constant	Studied for fiber alone	Decreased
			Resistivity		Decreased
			Electric loss tangent		Decreased

Therefore, for better predictions and improvements of the electrical behaviors and the characteristics of the biodegradable composites for reliable and sustainable applications, the polymer-filler synergy should properly be evaluated and examined.

Consequently, this work aims to fabricate new biodegradable materials, which have never been considered in the literature like sumac and black pepper/PP composites, in addition to others like lemon powder and pomegranate powder/PP composites that have never been considered regarding their electrical characteristics. In addition, the work examines various reinforcement conditions on the electrical characteristics of the composites to enhance developing better understanding of their interactions as well as determining the influential parameters on their final electrical behavior trends under various frequency ranges. The work also aims to examine and compare the dielectric constant and the conductivity properties of the bio-based materials with various natural fiber types and fiber loadings to demonstrate their potential for various electronic applications.

The following section, materials and methods, discusses the electric properties under consideration and the measurement technique being used. The physical properties and the manufacturing process of the proposed composites are also discussed in this section. The main results and discussion are presented in Results and Discussion. Conclusions presents the main findings and conclusions of the work.

Materials and Methods

Electric properties

Materials are described to be conductors, semiconductors, or insulators (dielectrics) depending on the concentration of free charge carriers within. Conductors are materials with very high concentrations of free charge carriers, whereas dielectrics are characterized by having relatively low concentration of free charge carriers dominated by bounded charges. When applying an electric field to a dielectric material, electric dipoles are formed because of orientational polarization.⁵⁰ This polarization process provides dielectrics with the ability to store energy. The most important parameters that are best describing how a dielectric material interacts with the applied electric field and thus characterizes its electric properties are; the dielectric constant (ε), also called permittivity, and the conductivity (σ) and its reciprocal resistivity (ρ).^50,51 The relative dielectric constant (ε_r) describes the dielectric material ability to store energy. Dielectric materials with higher relative dielectric constant can store more energy. The conductivity, on the other hand, represents the ability of the material to permit charge carriers to move freely. Increased conductivity of dielectric materials results in higher power losses in the form of heating. As these parameters are highly affected by the frequency of the applied electric field, their values are best presented in graph forms as function of frequency.

Many possible techniques are used to measure the electric properties of dielectric materials. These techniques include using transmission lines, cavity resonators, coaxial cables, and parallel plate capacitors associated with the proper measuring devices.^52,53 Choosing the best measuring technique depends on many factors including the nature of the samples under test and the way it is prepared, whether it is solid, liquid, or powder. Also, it depends on the homogeneity, the linearity, and the dispersive properties of the material. The frequency range within which the study is conducted is another very important factor in determining the suitable measuring technique.

In this research, the parallel-plate capacitor measuring method is used. This method is very useful for measuring the electrical properties for frequencies below 1 GHz range when the samples under test are prepared in the shape of flat sheets with thickness in the range of millimeters. This measuring technique depends on sinusoidal steady state analysis in which the dielectric material under test is surrounded by the parallel plate capacitor. The capacitor is subjected to sinusoidal electric potential with adjustable frequency, resulting in electric current flowing across it. The amplitude and phase of the electric current is then precisely measured. The equivalent admittance (Y) is calculated as the ratio of the measured current to the applied voltage. The admittance is a complex quantity with a real part representing the equivalent conductance (G) and imaginary part representing the equivalent susceptance (B)

Y = G + j B

(1)

The relative dielectric constant and the conductivity are related to the admittance of the dielectric material according to equations (2) and (3), respectively.

ε_{r} = \frac{D}{ε_{o} A} \frac{1}{ω} I m {Y}

(2)

σ = \frac{D}{A} R e {Y}

(3)

where ε_o is the dielectric constant of free space taken as 8.85 × 10⁻¹² F/m, D is the thickness of the dielectric material, also representing the distance between the two parallel plates, A is the area of the plates, and ω is the radian frequency.

Figure 1 shows a simplified schematic of the experimental setup used in performing the dielectric measurements of the samples under test. This setup consists of a parallel silver-plate capacitor, a high precision LCR meter, and a personal computer. The LCR meter used in this setup is the Hioki IM 3536. The LCR meter is connected to the parallel plate capacitor via a special type four-terminal probe (L2000 four-terminal probe) with measurable range from DC to 8 MHz. The measurement results are stored in the form of excel files on a PC for further processing.

Figure 1.

Experimental setup, (a) Schematic diagram of the setup, (b) the devise and specimens.

Samples under study

Four types of plants commonly used in Jordan were purchased from a local market in Amman city. The plants are black pepper seeds, sumac seeds, pomegranate peel, and lemon peel. Samples were dried overnight at 105^oC to reach a constant weight. All the dried samples were then grounded into fine powder of size around 50–120 μm using Ultra Centrifugal Mill ZM 200, RETSCH, Haan, Germany. The fiber size was measured using a scanning electron microscope (SEM) (Quanta™ 450 FEG SEM). The powder of each type was then utilized with polypropylene (PP) polymer for preparing various composites at different filler loading for their electrical properties. Polypropylene was purchased from SABIC Company at Saudi Arabia. Various filler loadings of the natural plant powder with polypropylene (10 wt.%, 20wt.%, and 30wt.%) were then prepared and the compound was mixed by the Haakepolydrive R600 internal mixer. Mixing process was performed for about 6 min with speed of 40 r/min. PP was initially charged into the hot mixer until torque was stabilized. Then, the powder was added into the hot mixer to ensure adequate mixing process. The mixture output was then located into a mold to create sheets of 1 mm thick to make the required specimens. The mold was then located in a hot press for 10 min. After that, a cooling procedure was performed by pressing every sheet between two molds at 25°C for 5 min; finally, various specimens were cut from the sheets. Samples were prepared for three different doping levels as tabulated in Table 2. The dielectric materials under study were prepared in the form of thin smooth sheets with thicknesses in the order of 1 mm. During the tests, these materials were mounted between silver plates using suitable pressure to insure excellent contact. These measurements were conducted at room temperature over the frequency range of 1.0 KHz to 4.0 MHz using Hioki IM 3536V LCR meter. To ensure accurate results three samples of each material under study is prepared and tested. The average of these readings is adopted as the result. Figure 2 represents a flow chart of the composite preparation. Samples of the prepared composites demonstrating the filler size are shown in Figure 3 to demonstrate the effect of filler size on the overall electrical characteristics of the composites.

Table 2.

List of samples under test.

Symbol	Material
BP10	Black pepper with 10% concentration
BP20	Black pepper with 20% concentration
BP30	Black pepper with 30% concentration
So10	Sumac with 10% concentration
So20	Sumac with 20% concentration
So30	Sumac with 30% concentration
Po10	Pomegranate with 10% concentration
Po20	Pomegranate with 20% concentration
Po30	Pomegranate with 30% concentration
Le10	Lemon with 10% concentration
Le20	Lemon with 20% concentration
Le30	Lemon with 30% concentration

Figure 2.

Composite preparations flowchart.

Figure 3.

Scan electron microscope of the prepared samples demonstrating the filler size, (a) sumac, (b) pomegranate, (c) lemon, and (d) black pepper.

Results and discussion

In this section the measurements of the relative dielectric constant and the conductivity of the composite samples under study are represented. Figure 4 shows the behavior of the relative dielectric constant of the BP10, BP20, and BP30 samples in response to frequency variation. The frequency response of the relative dielectric constant of a pure sample is taken as a reference. The measured results show that the additive dopants did not affect the general behavior of the material characteristics. That is, it is almost following the same behavior of the pure sample. However, the dielectric constant shows relatively good increment with increased filler concentration especially at the low frequency side. At 1.0 KHz frequency, samples with 10% filler loading show an increment in the dielectric constant of about 8%. Increasing the filler to 30%, results in an increment in the dielectric constant about 42%. As the frequency was increased to 1.0 MHz, the percentage increment decreased to around 2% for BP10 and 24% for BP30. Table 3 shows a summary of the percentage increment in the value of the relative dielectric constant of the samples under study at selected frequencies.

Figure 4.

Relative dielectric constant of samples BP10, BP20, and PB30 in comparison with pure sample with respect to frequency variations.

Table 3.

Summary of the percentage increment in the value of the relative dielectric constant at selected frequencies.

Sample	Percentage increment
Sample	1 KHz	100 KHz	1.0 MHz
BP10	8%	3%	2%
BP20	18%	7%	4%
BP30	42%	27%	24%
So10	0%	−2%	−2%
So20	19%	14%	12%
So30	55%	40%	31%
Le10	−11%	−7%	−4%
Le20	9%	10%	10%
Le30	13%	17%	20%
Po10	1%	3%	5%
Po20	14%	18%	21%
Po30	22%	27%	31%

Similar behavior was noticed for samples doped with sumac powder (So10, So20, and So30) as shown in Figure 5. Sumac composites with low filler concentration, So10, have almost no effect on the dielectric constant of the pure polymer. When increased to 30% filler loading, sumac composite shows percentage increment in the relative dielectric constant of around 55% at 1.0 KHz and 31% at 1.0 MHz.

Figure 5.

Relative dielectric constant of samples So10, So20, and So30 in comparison with pure sample with respect to frequency variations.

Measured results of the material when doped with pomegranate powder are presented in Figure 6. Unlike black pepper and sumac composites, pomegranate samples show higher increment in the dielectric constant at the high frequency side. When the frequency of the applied electric field is set to 1.0 MHz the percentage increment reaches 5% for Po10 and 31% for Po30. At 1.0 KHz, the percentage increment is 1% for Po10 and 22% for Po30.

Figure 6.

Relative dielectric constant of samples Po10, Po20, and Po30 in comparison with pure sample with respect to frequency variations.

Composites with lemon powder show behavior like that of pomegranate powder composites, as presented in Figure 7. The percentage increment in the value of the dielectric constant was found to increase as the frequency increases. At low filler loading of 10% the relative dielectric constant of lemon reinforced composite was lower than that of the pure sample. As filler loading increased, the dielectric constant increased showing a percentage increment of around 13% at 1.0 KHz and 20% at 1.0 MHz for Le30 samples.

Figure 7.

Relative dielectric constant of samples Le10, Le20, and Le30 in comparison with pure sample with respect to frequency variations.

Figure 8 shows a direct comparison of the relative dielectric constant of the different composites with 30% doping referenced to the pure material. Doping with 30wt. % sumac powder resulted in the maximum increment in the relative dielectric constant while lemon powder resulted in the minimum increment within the frequency range under consideration. Figure 9 represents a comparison among the percentage increments of the dielectric constant of all composites at 1.0 KHz, 100 KHz, and 1.0 MHz.

Figure 8.

Relative dielectric constant of samples with 30% doping in comparison with pure sample with respect to frequency variations.

Figure 9.

Comparison among the percentage increments of the dielectric constant of all composites at 1 KHz, 100 KHz, and 1.0 MHz.

The frequency dependence of the ac conductivity of the same samples of the material under study is investigated under the same previous conditions; frequency range of 1.0 KHz to 4.0 MHz at room temperature and humidity. The ac conductivity of all composites under test show very similar trend as of the pure polymer. At low frequencies the composites behave as good insulators exhibiting very low conductivity. As the frequency of the applied electric field increases, the conductivity increased. The effect of increased filler loading is more obvious at higher frequencies.

Moreover, the measured conductivity of black pepper composites is presented in Figure 10. The conductivity increases as the frequency of the applied electric field increases in a manner like that of the pure polymer. The conductivity of samples with filler loadings 10% and 20% show very small increment compared to the pure polymer. The effect of 30% filler loading is more obvious especially at high frequency side reaching a value of 0.53 mS/m at 4 MHz compared to 0.43 mS/m for pure polymer.

Figure 10.

Conductivity of samples BP10, BP20, and PB30 in comparison with pure sample with respect to frequency variations.

The conductivity of sumac powder composites was found following the same trend as of the pure polymer. The effect of different filler loadings in sumac powder composites over the measured conductivity is clearer than that of black pepper composites as seen in Figure 11. At 4.0 MHz, the measured conductivity of So30, So20, and So10 were around 0.59 mS/m, 0.52mS/m, and 0.46 mS/m, respectively.

Figure 11.

Conductivity of samples So10, So20, and So30 in comparison with pure sample with respect to frequency variations.

The results of the measured conductivity of pomegranate composites are presented in Figure 12. Like sumac composites, variation of pomegranate filler loading results in clear effect on the conductivity measured. At 4.0 MHz, the measured conductivity of Po30, Po20, and Po10 were around 0.55 mS/m, 0.50mS/m, and 0.43 mS/m, respectively.

Figure 12.

Conductivity of samples Po10, Po20, and Po30 in comparison with pure sample with respect to frequency variations.

Measured conductivity of lemon powder composite is represented in Figure 13. For samples with 10% filler loading the measured conductivity was less than that of the pure polymer. However, as filler loading increased to 20% and 30% the conductivity became larger than that of the pure polymer. At 4.0 MHz, the measured conductivity of Le30, Le20, and Le10 were around 0.50 mS/m, 0.45mS/m, and 0.40 mS/m, respectively.

Figure 13.

Conductivity of samples Le10, Le20, and Le30 in comparison with pure sample with respect to frequency variations.

Figures 14(a) and (b) present the frequency dependency of the conductivity and the resistivity of the four different composites under study with 30% filler loading. It is obvious that all composites follow the same trend as the pure polymer with sumac powder composites showing highest conductivity and Limon powder composites being the lowest. To investigate the filler loading effect, Figure 15 shows the conductivity as a function of the filler concentration of all prepared composites at 1.0 MHz and 4.0 MHz.

Figure 14.

(a) Conductivity and (b) resistivity of samples with 30% doping in comparison with pure sample with respect to frequency variations.

Figure 15.

Conductivity as a function of filler loading at 1.0 MHz and 4.0 MHz.

It has been noticed in all cases that the dielectric constant and the conductivity of the composites increased as the filler loading increased. This is mainly due to the expected presence of polar groups of cellulose and water content within these natural fillers.^12,54 With no electric field applied, these polar groups tend to have random directions resulting in a net zero polarization. When applying an electric field, the polar groups are redirected in the same direction of the electric field resulting in an increment in ε_r. When the frequency of the applied electric filed starts increasing, the randomness in the directions of the polar groups will also increase resulting in a decrement in the value of ε_r.

The net current density resulting from applied electric filed consists of three main components: the current density due to the applied source, the effective conduction current density, and the effective displacement current density. Both the effective conduction current density and the displacement current density are directly proportional to the frequency of the applied electric field. As the frequency increases, these two current densities will increase resulting in an increment in the total current density and thus increasing the conductivity of the dielectric composite.

The above results show that the dielectric constant have weak dispersive characteristics over the applied frequency spectrum. A possible reason for this limited effect is the absence of water content due to drying process of filler powders, which leads to relatively lower concentration of polar groups. This leads to low degree of oriented polarization in the composites when exposed to alternating electric field. However, increasing filler loading results in increasing polar group quantities, which leads to an increment in the dielectric constant. The effect of filler loading was more obvious at low frequency range. The maximum measured percentage increment was around 55% for So30 sample at 1.0 KHz. The resistivity of the composites under test shows an inverse relation with frequency over the considered spectrum. It was revealed that increasing the filler loading results in an increment in the conductivity of the composites over that of the pure polymer within the considered frequency spectrum. These observations are consistent with reported electric behavior of various filler reinforced polymer composites as in^4,47,48,55. Table 4 represents a summary of the measured dielectric constant as a function of frequency under different filler content of the composites presented in^4,47,48. The considered range of frequency in study⁴ was from 100 Hz to 2 MHz, whereas it was from 1 KHz to 1 MHz in study⁴⁷ and 5 Hz to 20 KHz in study⁴⁸. These results clearly show that the dielectric constant of the presented composites is proportional to the filler concentration and inversely proportional to the frequency of the applied electric field. This behavior is consistent with the conclusions of the review of the electric properties of filler reinforced polymer composites presented in⁵⁵.

Table 4.

Summary of the dielectric constant measurements presented in the literature.

		Frequency (Hz)				Remarks
		10³	10⁴	10⁵	10⁶	Remarks
[4]	Neat PP	2.7	2.8	2.6	2.6	ε_r increases as the filler concentration increases and decreases as the frequency increases
	19.3% jute	3.6	3.3	3.1	2.7
	37.1% jute	4.5	4.4	3.8	2.6
	55.9% jute	7.2	6.6	5.2	3.2

		Frequency (Hz)
		10³	10⁴	10⁵	10⁶
[47]	Pure polyester	3.2	2.4	2.2	2	ε_r increases as the filler concentration increases and decreases as the frequency increases
	25% jute	3.7	2.8	2.6	2.1
	50% jute	4.3	3.1	2.7	2.2
	75% jute	4.9	3.5	3	2.4

		Frequency (Hz)
		10	10²	10³	10⁴
[48]	Polyester	2.85	2.8	2.75	2.7	ε_r increases as the filler concentration increases and decreases as the frequency increases
	Sisal R10 vol%	3.1	3.1	3.05	2.9
	Sisal R30 vol%	3.25	3.2	3.15	3
	Sisal R40 vol%	3.4	3.35	3.3	3.1
	Sisal R50 vol%	3.5	3.4	3.35	3.15

Conclusions

Studying the electric characteristics of new natural composite materials is of crucial importance to be able to fully utilize them in new emerging industries. Various natural powder-based composites were investigated regarding their electrical behavior. It was revealed that the dielectric constant and the conductivity of the prepared composite materials show consistent trend behavior comparable to the pure samples with respect to frequency variation. Sumac powder composites have demonstrated the maximum increase in both dielectric constant and conductivity. The dielectric constant of So30 powder composites increased by about 55% at 1 KHz frequency and about 31% at 1 MHz. Le30 powder composites showed the minimum increment with 13% at 1 KHz and 20% at 1 MHz. It was also demonstrated that the conductivity of all composites has been increased with increasing the frequency. Sumac powder composites displayed the highest effect regarding enhancing the conductivity property, whilst lemon powder composites have demonstrated the lowest effect. The dielectric constant of the proposed composites showed low dependency on the frequency of the applied electric field within the considered range. The effect of filler loading was more obvious at higher frequencies. The ac conductivity showed high degree of dependency on frequency variations.

Footnotes

Acknowledgement

Authors would like to thank the anonymous reviewers for their valuable comments, which have enhanced the value of the work.

Declaration of conflicting interests

The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

Funding

The author(s) received no financial support for the research, authorship, and/or publication of this article.

Data availability

The raw/processed data required to reproduce these findings cannot be shared at this time as the data also forms part of an ongoing study.

ORCID iD

Faris AL-Oqla

References

Fares

AL-Oqla

. Modern electrical applications of biopolymers. In: Advanced processing, properties, and applications of starch and other bio-based polymers. Amsterdam, Netherlands: Elsevier; 2020, pp. 173–184.

Chen

Qiu

Han

, et al. Piezoelectric materials for sustainable building structures: fundamentals and applications. Renew Sustainable Energ Rev 2019; 101: 14–25.

AL-Oqla

Sapuan

Fares

. Electrical–based applications of natural fiber vinyl polymer composites. In: Natural fibre reinforced vinyl ester and vinyl polymer composites. Amsterdam, Netherlands: Elsevier; 2018, pp. 349–367.

George

Joseph

Nagarajan

, et al. Dielectric behaviour of PP/jute yarn commingled composites: effect of fibre content, chemical treatments, temperature and moisture. Compos A: Appl Sci Manuf 2013; 47: 12–21.

AL-Oqla

. Flexural characteristics and impact rupture stress investigations of sustainable green olive leaves bio-composite materials. J Polym Environ 2021; 29: 892–899.

AL-Oqla

Thakur

. Toward chemically treated low-cost lignocellulosic parsley waste/polypropylene bio-composites for resourceful sustainable bio-products. Int J Environ Sci Technol 2021: 1–10.

Omran

AAB

Mohammed

AABA

Sapuan

, et al. Micro-and nanocellulose in polymer composite materials: a review. Polymers 2021; 13: 231.

Ilyas

Sapuan

Harussani

, et al. Polylactic acid (PLA) biocomposite: processing, additive manufacturing and advanced applications. Polymers 2021; 13: 1326.

Hyland

Hunter

Liu

, et al. Wearable thermoelectric generators for human body heat harvesting. Appl Energ 2016; 182: 518–524.

10.

AL-Oqla

Sapuan

. Advanced processing, properties, and applications of starch and other bio-based polymers. Cambridge, USA: Elsevier, 2020.

11.

AL‐Oqla

. Introduction to Biobased Composites. In: Biobased composites: processing, characterization, properties, and applications. Hoboken, New Jersey: John Wiley & Sons, Inc, 2021, pp. 1–14.

12.

Fares

AL-Oqla

Hayajneh

. Dielectric relaxation of mediterranean lignocellulosic fibers for sustainable functional biomaterials. Mater Chem Phys 2019; 229: 174–182.

13.

Ismail

AL-Oqla

Risby

, et al. On the enhancement of the fatigue fracture performance of polymer matrix composites by reinforcement with carbon nanotubes: a systematic review. Carbon Lett 2022; 1–14. https://doi.org/10.1007/s42823-022-00323-z

14.

Hayajneh

AL-Oqla

Al-Shrida

MAM

. Hybrid green organic/inorganic filler polypropylene composites: morphological study and mechanical performance investigations. E-Polym 2021; 21: 710–721.

15.

Hayajneh

AL-Oqla

Aldhirat

. Physical and mechanical inherent characteristic investigations of various jordanian natural fiber species to reveal their potential for green biomaterials. J Nat Fibers 2021; 1–14. https://doi.org/10.1080/15440478.2021.1944432

16.

AL‐Oqla

Hayajneh

Aldhirat

. Tribological and mechanical fracture performance of Mediterranean lignocellulosic fiber reinforced polypropylene composites. Polym Compos 2021.

17.

AL-Oqla

Al-Jarrah

. A novel adaptive neuro-fuzzy inference system model to predict the intrinsic mechanical properties of various cellulosic fibers for better green composites. Cellulose 2021; 28: 1–12.

18.

AL-Oqla

. Performance trends and deteriorations of lignocellulosic grape fiber/polyethylene biocomposites under harsh environment for enhanced sustainable bio-materials. Cellulose 2021; 28: 2203–2213.

19.

Al-Ghraibah

Al-Qudah

AL-Oqla

. Medical Implementations of Biopolymers. In: Advanced processing, properties, and applications of starch and other bio-based polymers. Amsterdam, Netherlands: Elsevier; 2020, pp. 157–171.

20.

Alaaeddin

Sapuan

Zuhri

MYM

, et al. Development of photovoltaic module with fabricated and evaluated novel backsheet-based biocomposite materials. Materials 2019; 12: 3007.

21.

AL-Oqla

Hayajneh

Fares

. Investigating the mechanical thermal and polymer interfacial characteristics of Jordanian lignocellulosic fibers to demonstrate their capabilities for sustainable green materials. J Clean Prod 2019; 241: 118256.

22.

Alaaeddin

Sapuan

Zuhri

MYM

, et al. Physical and mechanical properties of polyvinylidene fluoride-Short sugar palm fiber nanocomposites. J Clean Prod 2019; 235: 473–482.

23.

AL-Oqla

Alaaeddin

El-Shekeil

. Thermal stability and performance trends of sustainable lignocellulosic olive/low density polyethylene biocomposites for better environmental green materials. Eng Solid Mech 2021; 9: 439–448.

24.

Ilyas

Sapuan

Norrrahim

MNF

, et al. Nanocellulose/starch biopolymer nanocomposites: Processing, manufacturing, and applications. In: Advanced processing, properties, and applications of starch and other bio-based polymers. Amsterdam, Netherlands: Elsevier; 2020, pp. 65–88.

25.

Alaaeddin

Sapuan

Zuhri

MYM

, et al. Lightweight and durable PVDF–SSPF composites for photovoltaics backsheet applications: thermal, optical and technical properties. Materials 2019; 12: 2104.

26.

Alaaeddin

Sapuan

Zuhri

MYM

, et al. Polymer matrix materials selection for short sugar palm composites using integrated multi criteria evaluation method. Composites B: Eng 2019; 176: 107342.

27.

AL-Oqla

Salit

. Materials Selection for Natural Fiber Composites, 1. Cambridge, USA: Woodhead Publishing, Elsevier, 2017.

28.

AL-Oqla

. Investigating the mechanical performance deterioration of Mediterranean cellulosic cypress and pine/polyethylene composites. Cellulose 2017; 24: 2523–2530.

29.

AL-Oqla

. Expert system optimizing model of filament winding process for improved automated composite manufacturing structure. J Ind Eng Int 2021; 17: 34–46.

30.

AL-Oqla

. Effects of intrinsic mechanical characteristics of lignocellulosic fibres on the energy absorption and impact rupture stress of low density polyethylene biocomposites. Int J Sustainable Eng 2021: 1–9.

31.

H-Y

Turng

L-S

, et al. Silver nanowire/thermoplastic polyurethane elastomer nanocomposites: thermal, mechanical, and dielectric properties. Mater Des 2014; 56: 398–404.

32.

Taskin

Ahmad

Wistlich

, et al. Bioactive electrospun fibers: fabrication strategies and a critical review of surface-sensitive characterization and quantification. Chem Rev 2021; 121: 11194–11237.

33.

Song

Qiu

Wang

, et al. Honeycomb structural rGO-MXene/epoxy nanocomposites for superior electromagnetic interference shielding performance. Sustainable Mater Tech 2020; 24: e00153.

34.

Pang

Lee

Suh

K-Y

. Recent advances in flexible sensors for wearable and implantable devices. J Appl Polym Sci 2013; 130: 1429–1441.

35.

Siwal

Zhang

Devi

, et al. Recovery processes of sustainable energy using different biomass and wastes. Renew Sustainable Energ Rev 2021; 150: 111483.

36.

Beluns

Gaidukovs

Platnieks

, et al. From wood and hemp biomass wastes to sustainable nanocellulose foams. Ind Crops Prod 2021; 170: 113780.

37.

Platnieks

Barkane

Ijudina

, et al. Sustainable tetra pak recycled cellulose/Poly (Butylene succinate) based woody-like composites for a circular economy. J Clean Prod 2020; 270: 122321.

38.

Abral

Basri

Muhammad

, et al. A simple method for improving the properties of the sago starch films prepared by using ultrasonication treatment. Food Hydrocolloids 2019; 93: 276–283.

39.

AL-Oqla

Sapuan

. Investigating the inherent characteristic/performance deterioration interactions of natural fibers in bio-composites for better utilization of resources. J Polym Environ 2018; 26: 1290–1296.

40.

AL-Oqla

Sapuan

Jawaid

. Integrated mechanical-economic–environmental quality of performance for natural fibers for polymeric-based composite materials. J Nat Fibers 2016; 13: 651–659.

41.

Zhan

Wool

Xiao

. Electrical properties of chicken feather fiber reinforced epoxy composites. Compos A: Appl Sci Manuf 2011; 42: 229–233.

42.

Lai

Sapuan

Ahmad

, et al. Mechanical and electrical properties of coconut coir fiber-reinforced polypropylene composites. Polymer-Plastic Technol Eng 2005; 44: 619–632.

43.

Dalai

Patra

Parida

. Interpretation of Cole–Cole dielectric dispersion of green composites from medical LINAC modified luffa fiber/PLA. J Mater Sci Mater Electronics 2022: 1–14.

44.

Salema

Yeow

Ishaque

, et al. Dielectric properties and microwave heating of oil palm biomass and biochar. Ind Crops Prod 2013; 50: 366–374.

45.

Zhang

Zheng

. Effect of physiochemical structure on energy absorption properties of plant fibers reinforced composites: dielectric, thermal insulation, and sound absorption properties. Compos Commun 2018; 10: 163–167.

46.

Shinoj

Visvanathan

Panigrahi

. Towards industrial utilization of oil palm fibre: physical and dielectric characterization of linear low density polyethylene composites and comparison with other fibre sources. Biosyst Eng 2010; 106: 378–388.

47.

Jayamani

Hamdan

Rahman

, et al. Comparative study of dielectric properties of hybrid natural fiber composites. Proced Eng 2014; 97: 536–544.

48.

Sreekumar

Saiter

Joseph

, et al. Electrical properties of short sisal fiber reinforced polyester composites fabricated by resin transfer molding. Compo t A: Appl Sci Manuf 2012; 43: 507–511.

49.

Paul

Joseph

Thomas

. Effect of surface treatments on the electrical properties of low-density polyethylene composites reinforced with short sisal fibers. Compos Sci Technol 1997; 57: 67–79.

50.

Balanis

. Advanced engineering electromagnetics. Hoboken, NJ: John Wiley & Sons, 2012.

51.

Jia

Tchoudakov

Segal

, et al. Electrically conductive composites based on epoxy resin with polyaniline-DBSA fillers. Synth Met 2003; 132: 269–278.

52.

Baker-Jarvis

Janezic

DeGroot

. High-frequency dielectric measurements. IEEE Instrumentation Meas Mag 2010; 13: 24–31.

53.

Nelson

. Fundamentals of dielectric properties measurements and agricultural applications. J Microw Power Electromagn Energy 2010; 44: 98–113.

54.

Chen

Y-C

Lin

H-C

Lee

Y-D

. The effects of filler content and size on the properties of PTFE/SiO2 composites. J Polym Res 2003; 10: 247–258.

55.

Pathania

Singh

. A review on electrical properties of fiber reinforced polymer composites. Int J Theoretical App Sci 2009; 1: 34–37.

Revealing the intrinsic dielectric properties of mediterranean green fiber composites for sustainable functional products

Abstract

Keywords

Introduction

Materials and Methods

Electric properties

Samples under study

Results and discussion

Conclusions

Footnotes

Acknowledgement

Declaration of conflicting interests

Funding

Data availability

ORCID iD

References