Mar 14, 2014
Improving graphene/polymer segregated composites for electromagnetic interference shielding
Using graphene to build up segregated conductive networks in polymer matrices provides an opportunity in electromagnetic interference shielding applications. Nevertheless, irreversible agglomeration of graphene often occurs during the chemical reduction of graphene oxide and seriously degrades the electromagnetic interference shielding effectiveness (EMI SE). Reporting in Nanotechnology, researchers at Sichuan University in China have developed an in situ technique to prepare graphene/polymer composites with more appealing properties.
Conductive polymer composites with a segregated structure have high electrical conductivity at low conductive filler loadings. This is due to the formation of effective conductive paths through the distribution of major fillers at the interfaces of polymer matrix domains. The integration of graphene provides additional properties ideal for electromagnetic interference shielding, but to overcome agglomeration complicated procedures and toxic reagents are required.
Using an in situ thermal reduction technique, the researchers have prepared a graphene/polymer composite that exhibits EMI SE at an ultralow graphene loading. Ultrahigh molecular weight polyethylene (UHMWPE) with high melt viscosity is chosen as the model polymer and the graphene networks are constructed in situ during hot compaction. This prevents the irreversible agglomeration of graphene and no toxic reagent is needed.
The as-prepared composite exhibits a typical segregated network structure with graphene squeezed along specific paths instead of a uniform distribution throughout the whole polymer matrix. The well defined graphene networks lead to an ultralow percolation threshold of 0.063 vol% and saturated electrical conductivity of 3.4 S/m–1. Excellent EMI SE as high as 28.3–32.4 dB is achieved at an ultralow graphene loading of 0.660 vol%, which means there is only 0.15–0.06% electromagnetic radiation transmitting through the shielding material. An absorption dominant shielding mechanism rather than reflection is detected in the composite.
The in situ thermal reduction technique provides a facile and environmentally friendly approach to fabricate conductive polymer composites with very high EMI SE, even with ultralow graphene loading. The absorption dominant shielding mechanism in this work is very important for the potential application of such segregated composites as absorption materials in automotive, consumer and medical electronics.
More information can be found in the journal Nanotechnology 25 145705.
Split-press-merge process aligns graphene nanosheets in composites (Apr 2013)
New material filters and polarizes terahertz radiation (Apr 2012)
Graphene-based remote controlled actuators put to the test (Jan 2012)
About the author
Ding-Xiang Yan is a PhD candidate at the College of Polymer Science and Engineering at Sichuan University, supervised by Jun Lei and Zhong-Ming Li. His research focuses on conductive polymer composites for multifunctional applications.