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.

Absorption dominant

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.

Further reading

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)