Novel Thermoplastic Material Concepts for High Voltage Cable Insulation - Engineering Immiscible Blends for a Sustainable Future
Doctoral thesis, 2021

To cope with our growing demand for energy in a sustainable way, efficient long-distance power transmission via high voltage direct current (HVDC) cables is crucial – these cables facilitate the integration of renewable energy into our power networks. For reliable and efficient power transmission, underground and undersea cables require robust insulation materials that possess a high level of mechanical integrity, a low direct-current (DC) electrical conductivity and a high thermal conductivity at the elevated temperatures experienced during cable operation. There is growing interest in thermoplastic materials that fulfill these requirements since thermoplastics offer the possibility for mechanical recycling by melt-reprocessing, and allow for more energy efficient cable production.

In this thesis, it is shown that thermoplastic blends of low-density polyethylene (LDPE) and isotactic polypropylene (iPP) can be engineered towards HVDC cable insulation applications despite the immiscibility between LDPE and iPP. Reactive compounding was explored as a strategy for compatibilising iPP and LDPE, resulting in a material concept that exhibited good thermomechanical properties while maintaining low DC electrical conductivity and thermoplasticity. Blends comprising iPP, LDPE and a styrenic copolymer were also investigated. This led to another thermoplastic material concept where the blend composition could be tuned to simultaneously attain appropriate mechanical stiffness, DC electrical conductivity and thermal conductivity. Further, the addition of aluminium oxide nanoparticles was found to reduce the already low DC electrical conductivity of such blends. The novel material concepts described in this thesis may facilitate the design of thermoplastic insulation materials for HVDC cables of the future.




high-voltage power cable insulation

polymer blends


Opponent: Professor Magnus Kristiansen, FHNW Institute of Polymer Nanotechnology, Switzerland


Yingwei Ouyang

Chalmers, Chemistry and Chemical Engineering, Applied Chemistry

Recyclable Polyethylene Insulation via Reactive Compounding with a Maleic Anhydride-Grafted Polypropylene

ACS Applied Polymer Materials,; Vol. 2(2020)p. 2389-2396

Journal article

Y. Ouyang, A. M. Pourrahimi, I. Östergren, M. Mellqvist, J. Ånevall, A. Soroudi, A. Lund, X. Xu, T. Gkourmpis, P.-O. Hagstrand, C. Müller. Highly Insulating Thermoplastic Blends Comprising a Styrenic Copolymer for Power Cable Insulation

A. Soroudi, Y. Ouyang, F. Nilsson, I. Östergren, X. Xu, M. Hedenqvist, C. Müller. Highly Insulating Thermoplastic Nanocomposites based on a Polyolefin Ternary Blend for HVDC Power Cables

Samarbetsövningar för plast – för en hållbar framtid

Om du arbetat i grupp har du förmodligen lagt märke till att människor är olika, och att det påverkar både gruppdynamiken och hur bra resultatet blir. Samma sak gäller polymerer, de långa molekyler som till exempel plast består av. Genom att blanda två olika polymerer kan vi skapa ett nytt material som har fler goda egenskaper än var polymer för sig. Men det fungerar inte om inte polymererna kan samarbeta, vilket är fallet för lågdensitetspolyeten (LDPE) och polypropen (PP). De gillar helt enkelt inte varandra.

Denna avhandling beskriver hur LDPE och PP, genom att blandas med ytterligare polymerer, kan bilda fungerande ”lag” av polymerer. När gruppdynamiken är rätt blir resultatet ett nytt material som kan lämpa sig för en så krävande tillämpning som isoleringsmaterial till högspänningskablar, som i sin tur är nödvändiga för att transportera elektricitet från vindturbiner långt ut i havet eller solceller i öknen till våra hem. Förutom att bidra till ett fungerande kabelnätverk, som är nödvändigt för skiftet från fossila till förnybara bränslen, bidrar dessa nya material också till en minskad resursåtgång genom en mer energisnål tillverkningsprocess jämfört med konventionella kabelmaterial. De kan också enkelt återvinnas genom att smältas ner och formas om till nya produkter. (Översättning: Emmy Järsvall och Anja Lund)

Matchmaking Plastics for a Sustainable Future

In group work, you have probably noticed how different people can be, how that affects group dynamics and how well a team functions. Polymers (long molecules found for example in plastics) behave similarly. When mixing two different polymers, we can create materials that combine some of the properties of both polymers. However, this is not necessarily so if the polymers are not fond of each other, as is the case for low density polyethylene (LDPE) and polypropylene (PP).

In this thesis, LDPE and PP are mixed together with other polymers to obtain “teams” of polymers with the right group dynamics, delivering materials with a combination of properties that could be suitable as insulation materials for high voltage power cables. Robust insulation of these cables is crucial for reliable and efficient transport of electricity from wind turbines far out at sea or solar cells in deserts to our homes, which is important as we shift from fossil fuels to renewables to sustainably cope with our increasing demand for energy. In addition to improving cable performance, the material concepts explored in this thesis facilitate recycling by remelting of the insulation layer at the end of life of cables, which can further enhance their contribution towards a sustainable future.

Subject Categories

Polymer Chemistry

Materials Engineering

Textile, Rubber and Polymeric Materials

Chemical Sciences

Driving Forces

Sustainable development


Chalmers Materials Analysis Laboratory

Areas of Advance

Materials Science



Doktorsavhandlingar vid Chalmers tekniska högskola. Ny serie: 5025





Opponent: Professor Magnus Kristiansen, FHNW Institute of Polymer Nanotechnology, Switzerland

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