Electrical Breakdown Properties of Clay-Based LDPE Blends and Nanocomposites

Mostafa Eesaee,Davide Fabiani,Nicole R Demarquette,Eric David

doi:10.1155/2018/7921725

Abstract

Microstructure and electrical breakdown properties of blends and nanocomposites based on low-density polyethylene (LDPE) have been discussed. A series of LDPE nanocomposites containing different amount of organomodified montmorillonite (clay) with and without compatibilizer have been prepared by means of melt compounding. Two sets of blends of LDPE with two grades of Styrene-Ethylene-Butylene-Styrene block copolymers have been prepared to form cocontinuous structure and host the nanoreinforcement. A high degree of dispersion of oriented clay was observed through X-ray diffraction, scanning, and transmission electron microscopy. This was confirmed by the solid-like behavior of storage modulus in low frequencies in rheological measurement results. An alteration in the morphology of blends was witnessed upon addition of clay where the transportation phenomenon to the copolymer phase resulted in a downsizing on the domain size of the constituents of the immiscible blends. The AC breakdown strength of nanocomposites significantly increased when clay was incorporated. The partially exfoliated and intercalated clay platelets are believed to distribute the electric stress and prolong the breakdown time by creating a tortuous path for charge carriers. However, the incorporation of clay has been shown to diminish the DC breakdown strength of nanocomposites, mostly due to the thermal instability brought by clay.

Highlights

It has been more than eight decades that synthetic polymers have been used as solid electrical insulating materials because of their excellent dielectric properties, the most important of which is the high dielectric breakdown strength
In reality the mechanism of dielectric breakdown is more complicated in many polymers and preexisting discontinuities contribute to the cumulative breakdown
Extensive works have been done to understand the behavior of polymers towards electrical breakdown which has led to considering several factors such as thickness, surrounding medium, pressure, and temperature, all along with the complicated morphology and structure of polymers which make the understanding of breakdown process very difficult

Summary

Introduction

It has been more than eight decades that synthetic polymers have been used as solid electrical insulating materials because of their excellent dielectric properties, the most important of which is the high dielectric breakdown strength. Electrons will multiply as a result of the ionization of the collision process, electronic conduction takes place, and breakdown occurs This mechanism is known as avalanche process [1, 2] and the dielectric strength is defined as the highest voltage the insulator withstands before breakdown divided by its thickness. Considerable attentions must be paid to tailor the interface with proper physical and chemical methods to obtain improved dielectric breakdown properties [18, 19] Another well-established approach to develop new materials is polymer blending [20]. In a narrow range of composition with proper processing, the blend microstructure can turn into cocontinuous, distinguished by a mutual interpenetration of the two components This type of microstructure is well-known for its tunable and substantial combination of functional and structural properties but is hard to achieve [22]. The possibility of using a binary blend to achieve a tailored dispersion of nanoclays to result in an improved AC and DC electrical breakdown was evaluated

Experimental

Results and Discussion

Conclusion