TiO₂-Enhanced Palm Oil Methyl Ester Nanofluid for Transformer Insulation: Experimental Evidence on Dielectric Strength and Stability

Alternative liquid insulating materials are attracting increasing attention for transformer applications because the electrical, physical, and chemical stability of an insulating fluid directly affects its suitability under operating conditions. The reviewed study experimentally investigates palm oil methyl ester (POME) modified with titanium dioxide (TiO₂) nanoparticles at concentrations of 0.05 g/L and 0.10 g/L. The researchers compare the formulations with pure POME using AC breakdown voltage testing before and after thermal ageing, together with Weibull statistical analysis, FTIR spectroscopy, density measurement, and viscosity characterization. The results show substantial improvement in breakdown voltage after TiO₂ addition, while density and viscosity changes remain relatively modest under the investigated conditions.

Bibliographic Information

Item	Information
Article Title	Experimental investigation of palm oil methyl ester nanofluid as a liquid insulating material
Authors	Yusri Jumat; Yanuar Z. Arief; Hendri Masdi; Valentine M. A. A. Jabu; Sharifah M. W. Masra; Nurul I. Hashim; S. K. Sahari; N. Junaidi; S. Rufus; Hamzah Eteruddin; Sinka Wilyanti
Journal	Teknomekanik
Volume	9
Issue	3
Publication Year	2026
Pages	285–301
DOI	https://doi.org/10.24036/teknomekanik.v9i3.52872
Publisher	Universitas Negeri Padang
License	Creative Commons Attribution 4.0 International (CC BY 4.0)
ISSN	e-ISSN: 2621-8720 p-ISSN: 2621-9980
Keywords	AC breakdown voltage, FTIR spectra, nanofluid, palm oil methyl ester, physicochemical properties
Official Article Page	https://teknomekanik.ppj.unp.ac.id/index.php/teknomekanik/article/view/528

Highlights

TiO₂ nanoparticles were incorporated into POME at concentrations of 0.05 g/L and 0.10 g/L.
The 0.10 g/L TiO₂ formulation produced the highest initial mean AC breakdown voltage of 33.17 kV.
The reported initial breakdown-voltage improvement reached approximately 72% relative to pure POME.
After 50 hours of thermal ageing, the 0.10 g/L formulation retained an average breakdown voltage of 24.44 kV.
Weibull statistical analysis showed conformity of the breakdown-voltage data to the Weibull distribution.
TiO₂ increased density and viscosity in a concentration-dependent manner.
The reported kinematic-viscosity values remained between 8.85 and 9.52 cSt.
FTIR analysis indicated that the principal chemical structure of POME remained stable after nanoparticle addition and thermal ageing.

1. Research Background

Transformer insulating liquids perform an essential electrical function by providing insulation against electrical breakdown while also participating in the thermal management of transformer systems. The study identifies mineral oil as a conventional insulating liquid but discusses concerns associated with its petroleum origin, non-renewable character, environmental contamination following leakage, and difficult disposal.

Palm oil methyl ester (POME) is investigated as an alternative base fluid because of its renewable and biodegradable characteristics. However, the paper also recognizes that vegetable-oil-based insulating fluids can exhibit higher viscosity and lower thermal stability than mineral oil. These characteristics can influence fluid movement and heat dissipation in transformer applications.

The study therefore investigates nanoparticle modification of POME using titanium dioxide (TiO₂). The authors focus on relatively low concentrations of 0.05 g/L and 0.10 g/L and examine whether these additions can improve dielectric strength while maintaining suitable physicochemical characteristics.

The research gap addressed by the study concerns the electrical performance and stability of TiO₂-POME nanofluids under thermal stress. To investigate this issue, the researchers combine AC breakdown-voltage measurements before and after thermal ageing with Weibull statistical analysis and physicochemical characterization through FTIR, density, and viscosity measurements.

2. Research Objective

To evaluate the electrical and physicochemical properties of POME nanofluids modified with TiO₂ nanoparticles as potential liquid dielectric insulation materials.
To investigate the AC breakdown voltage of POME containing 0.05 g/L and 0.10 g/L TiO₂ before and after thermal ageing.
To compare the dielectric performance of TiO₂-POME nanofluids with pure POME.
To characterize the density and viscosity of the tested fluids.
To investigate the chemical structure of POME and TiO₂-POME nanofluids using FTIR spectroscopy.
To apply statistical analysis, including normality testing and Weibull distribution analysis, to the AC breakdown-voltage data.

3. Why This Research Matters

Addresses the development of alternative insulating fluids. The study experimentally evaluates POME as a potential alternative liquid insulation material for transformer applications.
Investigates dielectric-strength enhancement. The incorporation of TiO₂ substantially increased the measured AC breakdown voltage, particularly at the 0.10 g/L concentration.
Examines performance after thermal ageing. The study does not rely only on initial dielectric-strength measurements but also evaluates the fluids after 50 hours of thermal ageing.
Combines electrical and physicochemical characterization. AC breakdown voltage, Weibull analysis, FTIR, density, and viscosity are considered together.
Investigates low nanoparticle concentrations. The research focuses on 0.05 g/L and 0.10 g/L TiO₂ rather than relying on high nanoparticle loading.
Provides experimental evidence for further research. The findings provide a basis for continued investigation of TiO₂-modified POME under broader and longer-term transformer operating conditions.

4. Research Methodology

The study adopted an experimental engineering approach to evaluate the dielectric and physicochemical behavior of TiO₂-modified POME. The research workflow involved nanofluid preparation, thermal ageing, AC breakdown-voltage testing, statistical analysis, FTIR characterization, and density and viscosity measurements.

Nanofluid Preparation

The researchers treated POME before preparing the nanofluid. Cetyltrimethylammonium bromide (CTAB) was used as a surfactant. The paper reports a 1:2 mass ratio involving CTAB and TiO₂, using 0.01 g CTAB and 0.02 g TiO₂. A 1000 ml POME and CTAB mixture was initially magnetically stirred at 1200 rpm for 30 minutes, followed by an additional one hour of stirring after nanoparticle addition.

The mixture was subsequently subjected to probe sonication at 40 kHz and 300 W for two hours at 50°C. The sonication procedure incorporated 30-minute intervals and 10-minute breaks to avoid overheating. The prepared fluid was then oven-dried for 48 hours at 85°C with the lid open to minimize residual moisture.

Experimental Formulations

Sample	TiO₂ Concentration
Pure POME	0 g/L
POME + TiO₂	0.05 g/L
POME + TiO₂	0.10 g/L

Thermal Ageing

Accelerated thermal ageing was conducted to investigate the behavior of the oil samples under thermal stress. The reported results compare unaged samples with samples subjected to 50 hours of thermal ageing. The paper describes the ageing process using a thermal oven but does not state a numerical ageing temperature in the accessible methodological description.

AC Breakdown Voltage Test

The AC breakdown-voltage test was conducted at the UNIMAS High Voltage AC Laboratory using a spherical-electrode test cell. The paper states that the test cell was in accordance with IEC 60156. AC breakdown voltage was used to evaluate the dielectric strength of the tested insulating fluids.

Normality and Weibull Analysis

The AC breakdown-voltage data were subjected to normality testing. The researchers also applied Weibull distribution analysis to characterize the statistical breakdown behavior and determine percentile breakdown voltages, including U1%, U10%, U50%, and U63.2%.

Density and Viscosity Measurement

An Anton Paar DMA 35 density meter was used for density measurement. Dynamic viscosity was measured using an IKA ROTAVISC lo-vi viscometer at 40°C. Kinematic viscosity was calculated using dynamic viscosity and fluid density.

FTIR Characterization

FTIR spectroscopy was performed using a Shimadzu IRAffinity-1 spectrometer. The samples were examined over the 400–4000 cm⁻¹ range to characterize chemical structure and functional groups and to assess changes associated with nanoparticle addition and thermal ageing.

5. Key Findings

TiO₂ Substantially Increased AC Breakdown Voltage

Pure POME exhibited an initial average AC breakdown voltage of 19.27 kV. The addition of 0.05 g/L TiO₂ increased the average breakdown voltage to 25.85 kV, corresponding to a reported increase of approximately 34%. The 0.10 g/L formulation achieved 33.17 kV, representing an increase of approximately 72% relative to the pure-POME value.

The 0.10 g/L Formulation Provided the Highest Initial Performance

Among the investigated formulations, the POME nanofluid containing 0.10 g/L TiO₂ produced the highest measured initial breakdown voltage. The result indicates a strong concentration-dependent improvement within the two concentrations investigated in the study.

Thermal Ageing Reduced Breakdown Voltage

Thermal ageing reduced the AC breakdown voltage of all tested fluids. Pure POME decreased from 19.27 kV before ageing to 15.40 kV after 50 hours. The corresponding average breakdown-voltage values for the 0.05 g/L and 0.10 g/L TiO₂ formulations after ageing were 20.68 kV and 24.44 kV, respectively.

Weibull U50 Values Confirmed the Improvement

For the unaged samples, the Weibull U50 values were 19.309 kV for pure POME, 26.038 kV for POME with 0.05 g/L TiO₂, and 33.349 kV for POME with 0.10 g/L TiO₂.

After 50 hours of ageing, the corresponding U50 values were 15.671 kV, 20.935 kV, and 24.801 kV. The reported values demonstrate that both TiO₂ formulations retained higher Weibull median breakdown voltages than aged pure POME.

Breakdown Data Showed Statistical Consistency

The reported Anderson–Darling normality tests produced p-values above 0.05 for all investigated sample and ageing conditions. The paper therefore reports conformity to a normal distribution for the AC breakdown-voltage datasets.

Weibull analysis also showed conformity of the datasets to the Weibull distribution. The reported p-values for the unaged samples were 0.17323 for pure POME, at least 0.25 for 0.05 g/L TiO₂-POME, and 0.2247 for 0.10 g/L TiO₂-POME. The aged samples were also reported to conform to the Weibull distribution.

FTIR Indicated Preservation of the Chemical Structure

The FTIR spectra exhibited characteristic POME features at 2927.94 cm⁻¹, 1739.79 cm⁻¹, and 1172.72 cm⁻¹. These were associated with C–H stretching, C=O stretching, and C–O stretching, respectively.

The study reports that the major chemical structure remained stable after nanoparticle addition and thermal ageing. The absence of new peaks was interpreted by the authors as evidence that no new chemical reaction occurred during nanofluid preparation.

Density Increased Slightly with TiO₂ Addition

Pure POME had a reported density of 0.86478 g/cm³. The density increased to 0.8658 g/cm³ for the 0.05 g/L TiO₂ formulation and 0.86634 g/cm³ for the 0.10 g/L formulation.

The reported density changes were small, with the increase becoming slightly greater at the higher TiO₂ concentration.

Viscosity Increased with TiO₂ Concentration

The measured dynamic viscosity of pure POME was 7.65 mPa·s. The value increased to 7.87 mPa·s at 0.05 g/L TiO₂ and 8.25 mPa·s at 0.10 g/L TiO₂.

The corresponding calculated kinematic viscosities were 8.85 cSt, 9.09 cSt, and 9.52 cSt for pure POME, 0.05 g/L TiO₂-POME, and 0.10 g/L TiO₂-POME, respectively. The paper reports that all tested values remained below 12 cSt.

Higher TiO₂ Concentration Produced Greater Dielectric Improvement

Within the concentration range examined, increasing TiO₂ concentration from 0.05 g/L to 0.10 g/L resulted in a further increase in the measured breakdown voltage. The authors associate this improvement with nanoparticle-related charge-trapping effects and interactions at the nanoparticle–fluid interface.

6. Scientific Contribution

Experimental evaluation of TiO₂-POME dielectric behavior. The study provides experimental measurements of AC breakdown voltage for POME modified with two low TiO₂ concentrations.
Integration of electrical and physicochemical characterization. The research combines breakdown-voltage testing with Weibull analysis, FTIR spectroscopy, density measurement, and viscosity measurement.
Evaluation before and after thermal ageing. The comparison between unaged and 50-hour aged samples provides information about the retention of dielectric strength under the investigated thermal-stress condition.
Identification of the stronger tested formulation. The 0.10 g/L TiO₂-POME formulation produced the highest initial mean and Weibull U50 breakdown voltages among the investigated samples.
Evidence of limited physicochemical change. Although TiO₂ addition increased density and viscosity, the measured changes remained relatively small under the experimental conditions.
Contribution to renewable insulating-fluid research. The findings provide an experimental basis for further studies of POME-based nanofluids as alternative liquid insulation materials.

7. Industrial Implications

Potential for transformer insulation research. The improved AC breakdown voltage indicates that TiO₂-POME formulations deserve further investigation for transformer insulation applications.
Promising dielectric performance at low nanoparticle concentration. The highest tested concentration, 0.10 g/L, produced the strongest initial breakdown-voltage performance in the study.
Thermal-ageing performance remains relevant. The 0.10 g/L formulation retained an average breakdown voltage of 24.44 kV after 50 hours of thermal ageing.
Viscosity remained within the limit used in the study. The measured kinematic viscosity values ranged from 8.85 to 9.52 cSt and remained below the 12 cSt limit discussed by the authors.
Renewable material platform. POME provides the base fluid investigated in this research and is described in the paper as renewable and biodegradable.
Further qualification is necessary. The experimental results do not by themselves establish long-term field performance, complete transformer compatibility, or commercial deployment readiness.

8. Research Limitations

Only two TiO₂ concentrations, 0.05 g/L and 0.10 g/L, were investigated.
The thermal-ageing investigation reported in the study was based on a 50-hour ageing period and therefore does not establish long-term operational durability.
The authors explicitly state that zeta-potential measurements, particle-size distribution, and extended sedimentation tests with photographic evidence were not performed.
The stability of nanoparticle dispersion was evaluated through indirect evidence, including narrow density variation, statistical consistency of breakdown-voltage measurements, and FTIR observations.
The reported physicochemical characterization focused on density, viscosity, and FTIR rather than a complete set of properties required for comprehensive transformer-fluid qualification.
Direct experimental comparison with commercial mineral insulating oil was not performed in the study.
The proposed nanofluids were not tested inside a working transformer.
The study does not establish large-scale manufacturing compatibility or long-term field performance.

9. Future Research Opportunities

Quantify dispersion stability. Future studies should perform zeta-potential measurements, particle-size characterization, and extended sedimentation experiments to provide direct quantitative evidence of nanofluid stability.
Extend thermal-ageing duration. Longer ageing periods would provide stronger evidence regarding the durability of the improved dielectric properties.
Investigate broader TiO₂ concentrations. Additional concentrations could clarify the relationship between nanoparticle loading and dielectric, rheological, and stability characteristics.
Expand physicochemical characterization. Future work can investigate additional parameters required for comprehensive assessment of insulating liquids under transformer operating conditions.
Perform direct comparisons with established insulating fluids. Experimental comparisons with conventional and alternative transformer insulating liquids would provide a clearer performance benchmark.
Conduct long-duration practical testing. Testing under more realistic operating conditions would help determine whether the laboratory improvements remain stable during prolonged electrical and thermal stress.
Investigate transformer-level compatibility. Future studies should examine the behavior of the optimized formulation within transformer systems rather than evaluating the fluid only as an isolated laboratory sample.

10. Potential for Public Policy Citation

The article does not present a dedicated public-policy analysis. Nevertheless, its findings may be relevant to research and development policies concerning renewable materials, biodegradable electrical insulation, and sustainable power infrastructure. The study experimentally evaluates a palm-oil-derived insulating fluid and demonstrates that TiO₂ modification can substantially affect its dielectric strength.

The findings may therefore provide technical evidence for supporting further research into renewable insulating materials. However, policy decisions concerning standards, procurement, deployment, or replacement of established transformer insulating fluids require broader evidence than the results reported in this single experimental study.

Any policy interpretation should therefore distinguish between laboratory evidence of improved breakdown-voltage performance and full qualification for practical transformer operation. The article itself identifies the need for further long-term stability and large-scale compatibility research.

11. Who Should Read This Paper?

Researchers in high-voltage engineering and dielectric materials.
Electrical engineers working on transformer insulation systems.
Researchers investigating natural ester and vegetable-oil-based insulating fluids.
Nanofluid researchers studying dielectric and physicochemical properties.
Researchers investigating TiO₂-modified insulating liquids.
Graduate students studying transformer insulation and dielectric breakdown.
Engineers investigating renewable and biodegradable alternatives to conventional insulating oils.
Researchers applying Weibull analysis to dielectric breakdown data.

12. Frequently Asked Questions (FAQ)

What is the main purpose of the study?

The study evaluates TiO₂-modified palm oil methyl ester as a potential liquid dielectric insulation material by examining its AC breakdown voltage and selected physicochemical properties before and after thermal ageing.

Which TiO₂ concentrations were investigated?

The researchers investigated 0.05 g/L and 0.10 g/L TiO₂ in POME, with pure POME serving as the reference fluid.

Which formulation produced the highest breakdown voltage?

The POME nanofluid containing 0.10 g/L TiO₂ produced the highest initial mean AC breakdown voltage, reaching 33.17 kV.

How much did the breakdown voltage increase?

The initial average breakdown voltage increased from 19.27 kV for pure POME to 25.85 kV for the 0.05 g/L formulation and 33.17 kV for the 0.10 g/L formulation. The paper reports these improvements as approximately 34% and 72%, respectively.

What happened after thermal ageing?

After 50 hours of thermal ageing, the average breakdown voltage decreased to 15.40 kV for pure POME, 20.68 kV for the 0.05 g/L TiO₂ formulation, and 24.44 kV for the 0.10 g/L TiO₂ formulation.

What were the Weibull U50 values?

For unaged samples, the reported U50 values were 19.309 kV for pure POME, 26.038 kV for 0.05 g/L TiO₂-POME, and 33.349 kV for 0.10 g/L TiO₂-POME. After 50 hours of ageing, the values were 15.671 kV, 20.935 kV, and 24.801 kV, respectively.

Did TiO₂ change the viscosity?

Yes. Dynamic viscosity increased from 7.65 mPa·s for pure POME to 7.87 mPa·s at 0.05 g/L TiO₂ and 8.25 mPa·s at 0.10 g/L TiO₂. The corresponding kinematic viscosity values were 8.85 cSt, 9.09 cSt, and 9.52 cSt.

Did TiO₂ change the density?

Yes, but only slightly under the investigated conditions. Density increased from 0.86478 g/cm³ for pure POME to 0.8658 g/cm³ at 0.05 g/L TiO₂ and 0.86634 g/cm³ at 0.10 g/L TiO₂.

What did the FTIR analysis show?

The FTIR analysis showed characteristic POME peaks at 2927.94 cm⁻¹, 1739.79 cm⁻¹, and 1172.72 cm⁻¹. The authors report that the principal chemical structure remained stable after nanoparticle addition and thermal ageing.

Was the nanofluid experimentally tested?

Yes. The study used laboratory AC breakdown-voltage testing, thermal ageing, FTIR spectroscopy, density measurement, viscosity measurement, and statistical analysis of the breakdown-voltage data.

Does the study prove that TiO₂-POME is ready for commercial transformer applications?

No. The study provides experimental evidence of improved dielectric performance under the investigated laboratory conditions, but it does not establish long-term field performance, complete transformer compatibility, or commercial deployment readiness.

What is the principal limitation of the study?

A major limitation is that the investigation is limited to selected laboratory conditions, two TiO₂ concentrations, and a 50-hour thermal-ageing period. The authors also identify the need for quantitative stability measurements and longer-term studies.

13. Final Thoughts

This study presents an experimental investigation of TiO₂-modified palm oil methyl ester as a potential liquid insulating material. Its strongest result is the substantial improvement in AC breakdown voltage achieved after the addition of TiO₂. The 0.10 g/L formulation produced the highest initial mean breakdown voltage of 33.17 kV, compared with 19.27 kV for pure POME.

The thermal-ageing results provide an important additional dimension to the investigation. Although ageing reduced the breakdown voltage of all formulations, the TiO₂-containing samples retained higher average values than aged pure POME. The 0.10 g/L formulation retained 24.44 kV after 50 hours, compared with 15.40 kV for aged pure POME.

The physicochemical measurements show a concentration-dependent increase in density and viscosity, while the FTIR results indicate preservation of the principal chemical structure of the fluid. Taken together, the findings indicate that TiO₂ can improve the measured dielectric performance of POME without producing large changes in the specific physical and chemical characteristics examined in this study.

Nevertheless, the results should be interpreted within the experimental scope of the paper. The study does not establish long-term field performance or complete transformer-system qualification. Further work involving quantitative nanofluid stability measurements, longer thermal ageing, broader characterization, direct comparison with established insulating liquids, and transformer-level validation is necessary before practical deployment can be assessed.

14. Suggested Citations

Teknomekanik (UNP) Style

Y. Jumat, Y. Z. Arief, H. Masdi, V. M. A. A. Jabu, S. M. W. Masra, N. I. Hashim, S. K. Sahari, N. Junaidi, S. Rufus, H. Eteruddin, and S. Wilyanti, "Experimental investigation of palm oil methyl ester nanofluid as a liquid insulating material," Teknomekanik, vol. 9, no. 3, pp. 285–301, 2026, https://doi.org/10.24036/teknomekanik.v9i3.52872.

APA (7th Edition)

Jumat, Y., Arief, Y. Z., Masdi, H., Jabu, V. M. A. A., Masra, S. M. W., Hashim, N. I., Sahari, S. K., Junaidi, N., Rufus, S., Eteruddin, H., & Wilyanti, S. (2026). Experimental investigation of palm oil methyl ester nanofluid as a liquid insulating material. Teknomekanik, 9(3), 285–301. https://doi.org/10.24036/teknomekanik.v9i3.52872

IEEE Style

Harvard Style

Jumat, Y., Arief, Y.Z., Masdi, H., Jabu, V.M.A.A., Masra, S.M.W., Hashim, N.I., Sahari, S.K., Junaidi, N., Rufus, S., Eteruddin, H. and Wilyanti, S. (2026) 'Experimental investigation of palm oil methyl ester nanofluid as a liquid insulating material', Teknomekanik, 9(3), pp. 285–301. doi:10.24036/teknomekanik.v9i3.52872.

Vancouver Style

Jumat Y, Arief YZ, Masdi H, Jabu VMAA, Masra SMW, Hashim NI, Sahari SK, Junaidi N, Rufus S, Eteruddin H, Wilyanti S. Experimental investigation of palm oil methyl ester nanofluid as a liquid insulating material. Teknomekanik. 2026;9(3):285–301. doi:10.24036/teknomekanik.v9i3.52872.

Chicago (Author–Date)

Jumat, Yusri, Yanuar Z. Arief, Hendri Masdi, Valentine M. A. A. Jabu, Sharifah M. W. Masra, Nurul I. Hashim, S. K. Sahari, N. Junaidi, S. Rufus, Hamzah Eteruddin, and Sinka Wilyanti. 2026. "Experimental Investigation of Palm Oil Methyl Ester Nanofluid as a Liquid Insulating Material." Teknomekanik 9 (3): 285–301. https://doi.org/10.24036/teknomekanik.v9i3.52872.

MLA (9th Edition)

Jumat, Yusri, et al. "Experimental Investigation of Palm Oil Methyl Ester Nanofluid as a Liquid Insulating Material." Teknomekanik, vol. 9, no. 3, 2026, pp. 285–301. https://doi.org/10.24036/teknomekanik.v9i3.52872.

15. Editorial Note

This Engineering Research Insights review has been prepared for scholarly communication based on the published research article. The scientific discussion is derived from the article itself, while the bibliographic information is based on the official Teknomekanik article page and the publication record of the article.

This review is intended to help researchers, engineers, graduate students, and other readers understand the study's research background, objectives, methodology, principal findings, scientific contribution, and limitations. It should not be considered a substitute for the original publication.

Readers are strongly encouraged to consult the original article and cite the original publication whenever its methods, data, findings, or concepts are used in academic publications, theses, dissertations, technical reports, or other scholarly works.

Original article: https://teknomekanik.ppj.unp.ac.id/index.php/teknomekanik/article/view/528

16. SEO Meta Description

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