NITRILE BUTADIENE RUBBER/CARBON NANOTUBES NANOCOMPOSITES : ROLE OF POLYMER-TO-FILLER GRAFTING REACTIONS.

1. NITRILE BUTADIENE RUBBER/CARBON NANOTUBES NANOCOMPOSITES :
ROLE OF POLYMER-TO-FILLER GRAFTING REACTIONS.
P. Verge1, S. Peeterbroeck2, L. Bonnaud2, Ph. Dubois1,2
1.Center of Innovation and Research in MAterials & Polymers (CIRMAP), University of Mons, 20 Place du Parc, B-7000 Mons – Belgium
2. Materia Nova Research Center, Parc Initialis, B-7000 Mons - Belgium
INTERACTIONS BETWEEN NBR AND CARBON NANOTUBES
Morphological analyses (TEM) of 3%wt CNTs/NBR
18%wt ACN 34%wt ACN 44%wt ACN
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PHYSICAL INTERACTIONS
Chemical structure of Nitrile Butadiene Rubber (NBR)*
Rubber component Polar component
Characterization by bound rubber tests
Experimental conditions: Solvent :chloroform
16 hours magnetic stirring
Centrifugation : 4000 rpm for 20 minutes
Drying under vacuum
CNT
CNTuedriedresid
m
mm
Qads


Thermogravimetric analysis (TGA) on the dried supernatant (containing
solubilized NBR and grafted CNTs) (v=20°C/min, under He)
Amount of grafted CNTs
1.38%wt
- Thermal degradation
N

N
C + H - Chain scissions
- Thermomechanical degradation
Polymer-to-filler grafting reaction due the formation of free
radicals during blending process
CHEMICAL INTERACTIONS
Polymer-to-filler adsorption due to their affinity
More NBR is adsorbed when it contains more ACN More CNTs are grafted when they are mixed with a high
ACN content NBR
Schematic representationBetter CNTs dispersion in NBR with higher ACN content
Materials and methods: Nitrile Butadiene Rubber (NBR) is supplied by Lanxess. Carbon nanotubes (CNTs) are supplied by Nanocyl and used as
received. NBR and CNTs are mixed together (60rpm, 50°C, 10min) with vulcanization agents in an internal mixer. Compounds are then vulcanized at
190°C during 15 minutes.
Evidence of the good CNTs dispersion by electrical
measurements
COMPARISON TO THE STATE OF THE ART
EFFECTS ON THE DISPERSION OF CNT IN NBR
Percolation
threshold varies
with ACN content
Authors highly thank the « La Wallonie » for the financial support in the frame of the project Plan Marshall-NANOCOMPO.
CIRMAP thanks the Belgian Federal Government Office Policy of Science (SSTC) for general support in the frame of the
PAI-6/27.
It was shown that during the blending process, the polymer chains are grafted onto the CNT surface via a free-
radical mechanism. Indeed, NBR generates free-radicals from its ACN units upon heating and/or shearing . As a
result of the high inherent affinity between the CNTs and ACN units, and due to the formation of ACN-based free-
radicals leading to NBR-grafting on CNTs, increasing the ACN relative content along NBR chains triggers higher
polymer-grafting on the nanotube surface. As a result, it has been shown by both electrical measurements and
morphological analyses that the CNT bundles are more intensively disrupted and the individualized nanotubes more
finely dispersed in NBR at higher ACN relative content.
As the process conditions monitor the polymer-grafted rates, they also affect the properties of the materials.