Influence of the Reinforcement Structure on the Thermal Conductivity and Surface Resistivity of Vinyl Ester Composites Used on Explosion-Proof Enclosures of Electrical Equipment
Abstract
:1. Introduction
- development of the composite structure and manufacturing technology (taking into account the potential application),
- conducting thermal tests,
- determination of surface resistivity,
- determination of strength characteristics (flexural strength, flexural modulus, strain, and interlayer shear strength),
- verification pressure tests of the enclosure.
2. Materials for Research and Methodology
2.1. Materials for Research
2.2. Thermal Properties Research
2.3. Surface Resistivity
2.4. Mechanical Tests
- flexural strength:
- flexural modulus:
3. Results and Discussion
3.1. Thermal Conductivity
3.2. Surface Resistivity
3.3. Strength Results
3.4. Enclosures Design and Pressure Tests
4. Conclusions
- The S4 structure is characterized by the highest tested thermal properties, surface resistive, flexural strength, and modulus. It is related to the 800 g/m2 quadriaxial reinforcement material used.
- Interlayer shear strength of S4 structure is 19 MPa lower than that of composite S1. This is due to the impregnation of the fabric. Glass fabrics of 550 g/m2 are much easier to impregnate than 800 g/m2, using the technology of hand-up lamination with a vacuum. The structure S1 also showed a higher strain than S4, which is a better solution assuming the target application.
- The lowest values of the glass composites (structures S1, S2, S3), flexural strength, and modulus are characteristic of the composite with the S3 structure. Composite S2 shows properties that average the structures S1 and S3. The structure S3 was characterized by the lowest value of inter-layer shear. It is related to the layout, type, and several number layers of reinforcement.
- Composites with S1, S2, and S3 structures are characterized by lower values of the thermal conductivity coefficient and higher surface resistivity than S4. It is related to the properties of glass, which plays an important role here. Graphite introduced into the vinyl ester resin significantly increases the specific heat and thermal conductivity and lowers the surface resistivity.
- The developed procedure for determining the specific heat based on the rule of mixtures allows approximating the value of specific heat by approx. 10% for composites reinforced with fabrics. For composites reinforced with fabric and mat or only mat, the approximate value is approx. 5%.
- The designed and made an explosion-proof enclosure for electrical devices made of S1 composite with a wall thickness of 7 mm, withstands an internal pressure of 8 bar. The composite showed no damage. Leaks having a significant impact on pressure resistance were observed at the connection enclosure–lid. This requires the design of a different, more airtight joint sealing system.
Author Contributions
Funding
Institutional Review Board Statement
Informed Consent Statement
Data Availability Statement
Conflicts of Interest
References
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S1 | S2 | S3 | S4 | ||||
---|---|---|---|---|---|---|---|
Material | Number of Layers | Material | Number of Layers | Material | Number of Layers | Material | Number of Layers |
Glass triaxal 550 g/m2 (0/45/90) | 13 | Glass triaxal 550 g/m2, (0/45/90) | 3 | Glass mat 450 g/m2 | 16 | Carbon quadrax 800 g/m2 (0/−45/90/45) | 9 |
Glass mat 450 g/m2 | 7 | ||||||
Glass triaxial 550 g/m2, (0/45/90) | 3 | ||||||
Σ13 ~7 mm | Σ13 ~7 mm | Σ16 ~7 mm | Σ9 ~7 mm |
Property | Standard | Unit | Modified POLIMAL-VE-11 MAT |
---|---|---|---|
Density | ISO 1183-1 | g/cm3 | 1.55 |
Gel time at 25 °C | ISO 2535 | min | 25 |
Flammability class | EN 60695-11-10:2014-02 | - | V0 |
Flexural strength | ISO 178 | MPa | 50.61 |
Flexural modulus | ISO 527 | MPa | 5271.6 |
Strain at break | ISO 527 | % | 1.34 |
Specific heat | ISO 11357-4:2013 | J/gK | 2.46 |
Thermal conductivity coefficient | - | W/mK | 5.64 |
Surface resistivity | IEC 61340-2-3 | Ω | 5.19 × 103 |
Structures | Surface Resistivity, Ω |
---|---|
S1 | 3.36 × 103 |
S2 | 3.15 × 103 |
S3 | 2.85 × 103 |
S4 | <103 |
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Szymiczek, M.; Buła, D.; Koczwara, J. Influence of the Reinforcement Structure on the Thermal Conductivity and Surface Resistivity of Vinyl Ester Composites Used on Explosion-Proof Enclosures of Electrical Equipment. Materials 2022, 15, 5190. https://0-doi-org.brum.beds.ac.uk/10.3390/ma15155190
Szymiczek M, Buła D, Koczwara J. Influence of the Reinforcement Structure on the Thermal Conductivity and Surface Resistivity of Vinyl Ester Composites Used on Explosion-Proof Enclosures of Electrical Equipment. Materials. 2022; 15(15):5190. https://0-doi-org.brum.beds.ac.uk/10.3390/ma15155190
Chicago/Turabian StyleSzymiczek, Małgorzata, Dawid Buła, and Jacek Koczwara. 2022. "Influence of the Reinforcement Structure on the Thermal Conductivity and Surface Resistivity of Vinyl Ester Composites Used on Explosion-Proof Enclosures of Electrical Equipment" Materials 15, no. 15: 5190. https://0-doi-org.brum.beds.ac.uk/10.3390/ma15155190