The semi-crystalline polymer Polyethylene (PE) is today the dominant insulation material for high voltage cables. The insulation efficiency of PE can however be further improved by the addition of inorganic nanoparticles (MgO, Al2O3, ZnO) [1-3]. Furthermore, PE’s with bimodal chain-length distributions (i.e. both long and short chains) often have improved mechanical as well as electrical properties as compared to unimodal PE . It is known that the redistribution of water influences the conductivity of PE-nanocomposites  and that the fraction of tie-chains and entanglements bridging the PE crystal lamellae influences the properties of pure PE [6,7], but a significant part of the underlying physics needs further study. An increased knowledge in this field is crucial for the development of the next generation of high voltage cables, which are envisioned to transmit energy over large distances with highly reduced energy losses.
We are intending to use large scale atomistic and coarse-grained simulations techniques (including both molecular dynamics Monte- Carlo simulations) for explaining why the properties of PE are affected by both the nanoparticles and the bimodality of the molar mass distribution. The gained knowledge is important for the process of tailor-making the polymer to obtain optimum properties for the given application. Coarse Graining codes will be used to obtain coarse-grained potentials based on atomistic Molecular Dynamics (MD) and Monte Carlo (MC) simulations. Having the coarse grained potentials, MD/MC simulations will be performed for predicting morphology and structure/property relationships for semi-crystalline polymers and polymeric nanocomposites. Electrical and mechanical properties as well as transport properties (diffusion/solubility) will also be examined.
This research propagates according to two different lines:
(1) The electrical performance (HVDC) of branched polyethylene (with and without metal oxide nanoparticles), also including low molar mass impurities such as water and by- products from crosslinking is one focus system. Our division has conducted research, mostly experimental and more lately theoretical (using various simulation methods) resulting in 30 scientific papers. It is fair to say that this research is in the absolute research frontier. We hold also several patents which shows that the research is close to result in practical application – insulation of ultra-high voltage DC cables; then latter being very important for distributing solar-based electrical power.
(2) The mechanical performance of multimodal polyethylene systems. This is a very urgent area, which will provide extremely important information that will form a base for further development of ultra-high fracture tough polyethylene to be used in the green development of our energy system. We have a long tradition in this type of research. Prof. Ulf Gedde was one of the principal scientist to provide this way of thinking in the 1980s which finally lead to the Borstar material group (Borealis, Sweden). We have published probably of the order of 50 scientific papers, mostly experimental. The very novel type of modelling here proposed is in the absolute research frontier.