Dielectric properties and electromagnetic interference shielding effectiveness of graphene-based biodegradable nanocomposites Sima Kashi a , Rahul K. Gupta a, ⁎, Thomas Baum b , Nhol Kao a , Sati N. Bhattacharya a a Rheology and Materials Processing Centre (RMPC), School of Engineering, RMIT University, Melbourne, Victoria 3000, Australia b Electrical and Computer Engineering, School of Engineering, RMIT University, Melbourne, Victoria 3000, Australia HIGHLIGHTS • Electrical permittivity and conductivity of PLA and PBAT and therefore their EMI SE enhanced markedly with GNP embedding. • Variations of complex permittivity of PLA and PBAT with GNP loading were suc- cessfully modelled by Sihvola's mixing rule. • For both PLA and PBAT, electrical perco- lation occurred at GNP loading of be- tween 6 and 9 wt% (3.5 and 5.3 vol%). • PLA nanocomposites with 9 – 15 wt% GNPs had higher dielectric loss values compared to PBAT nanocomposites. • PLA/GNP nanocomposites exhibited sig- nificantly higher potential for EMI absorp- tion than PBAT/GNP nanocomposites. GRAPHICAL ABSTRACT abstract article info Article history: Received 9 April 2016 Received in revised form 30 June 2016 Accepted 13 July 2016 Available online 14 July 2016 Graphene nanoplatelets (GNPs) were dispersed in poly lactide (PLA) and poly(butylene adipate-co-terephthal- ate) (PBAT) via melt-mixing. Effect of GNP incorporation on electromagnetic properties and electromagnetic in- terference shielding effectiveness (SE) of PLA and PBAT was investigated and the two systems were systematically compared. Furthermore, applicability of Sihvola's mixing rule of complex electrical permittivity to these nanocomposites was studied. GNP addition significantly enhanced permittivity of both polymers. Dielec- tric constants of PLA and PBAT nanocomposites had comparable values. However, above 6 wt% GNPs, PLA nano- composites showed significantly higher dielectric loss than PBAT nanocomposites, even though pure PLA had lower dielectric loss than pure PBAT. This was attributed to the dispersion state of GNPs in the two matrices, de- tected in morphological studies. SE of both polymers increased with GNP addition due to enhancement of their dielectric properties. The difference in dielectric loss of the two systems was revealed in their ability to attenuate the radiation by absorption. At 15 wt% GNPs, 1 mm-thick PLA/GNP nanocomposite had an effective absorbance of 70%. This value was only 43% for PBAT/GNP nanocomposite. Variations of polymers' permittivities with GNPs were successfully modelled by Sihvola's rule. While both systems returned close values for model's fitting param- eters, it better fitted PBAT/GNP nanocomposites. © 2016 Elsevier Ltd. All rights reserved. Keywords: Electromagnetic interference shielding Dielectric properties Poly lactide Poly (butylene adipate-co-terephthalate) Graphene nanoplatelet Nanocomposite Materials and Design 109 (2016) 68–78 ⁎ Corresponding author. E-mail address: rahul.gupta@rmit.edu.au (R.K. Gupta). http://dx.doi.org/10.1016/j.matdes.2016.07.062 0264-1275/© 2016 Elsevier Ltd. All rights reserved. Contents lists available at ScienceDirect Materials and Design journal homepage: www.elsevier.com/locate/matdes