A unique combination of excellent mechanical, thermal and barrier properties has
made graphene a multifunctional reinforcement for polymers. The goals of this
research were to prepare exfoliated functionalized graphene sheets (FG) from
expanded graphite, the uniform dispersion of these graphene sheets in the nylon 12
matrix, and understanding the effect of graphene on mechanical, thermal and barrier
properties of nylon 12. FG were successfully prepared from various methods and
was confirmed by XPS and TEM analysis. FG were melt blended with nylon 12 and
their dispersion in the matrix was characterized by SEM. Crystallization behaviour of
Nylon 12/ FG was investigated by means of differential scanning calorimetery (DSC).
Non isothermal crystallization analysis revealed that the addition of only 1wt% FG in
nylon 12 improved its crystallinity to about 67%. Application of Avrami analysis; to
study isothermal crystallization kinetics; disclosed an unchanged nucleation
mechanism and growth geometry. Polarized optical microscopy (POM) results
indicated that FG did act as nucleating agent but hindered the formation of larger
size crystals. Study of mechanical performance revealed that the incorporation of
very small amount (about 0.6wt %) of the FG caused a significant improvement in
ultimate tensile strength, elongation, impact strength and toughness of the nylon 12.
With 0.6wt% FG ultimate tensile strength and elongation at break of the nylon 12 is
improved by ～ 35% and ～200%, respectively. FTIR confirmed the hydrogen
bonding between nylon 12 and FG, which contributed towards strengthening of the
interface. The KIc of the nylon 12 is ～1.28 MPa.m0.5 and the incorporation of 0.6wt%
FG causes a significant increase of 72 % (～2.2 MPa.m0.5). 0.6wt% FG causes also
a significant improvement of 175 % in impact failure energy of the nylon 12. The
incorporation of FG caused the increase in amount of γ phase of nylon12 and
decreased its crystal size which could be the direct reason for the enhancement of
the toughness. Nano-graphite, MWCNTs and carbon black were surface
functionalized and their effect on the toughness was investigated. The results proved
graphene to be the best nanofiller among three for the toughening of nylon 12.
Oxygen and water permeability of nylon 12 was decreased to ~40%, implying the
high aspect ratio of graphene which forced the permeant to pass through longer
A Doctoral Thesis. Submitted in partial fulfillment of the requirements for the award of Doctor of Philosophy of Loughborough University.