Vikal Mittal, S Kim, Sandra Neuhofer, Christian Paulik,
"Polyethylene/graphene nanocomposites: effect of molecular weight on mechanical, thermal, rheological and morphological properties"
, in Colloid and Polymer Science, Vol. 294, Seite(n) 691, 1-2016, ISSN: 0303-402X
Original Titel:
Polyethylene/graphene nanocomposites: effect of molecular weight on mechanical, thermal, rheological and morphological properties
Sprache des Titels:
Englisch
Original Kurzfassung:
Three different polyethylene samples (molecular
weights PE1 < PE2 < PE3) were synthesized using coordina-
tion polymerization, in order to study the effect of the varia-
tion in molecular weight on the properties of the nanocompos-
ites, using thermally reduced graphene as filler. The polymer
samples had similar crystal structure but had 61, 56, and 52 %
degree of crystallinity respectively. For PE1, the degree of
crystallinity enhanced on adding 2 and 4 % graphene due to
nucleation induced by the graphene nanoplatelets; however,
the crystallinity was observed to decrease in PE2 and PE3.
Peak melting points also exhibited similar trend, although
the overall change was limited to 3
?
4 °C. The filler was ob-
served to be in the form of stacks with few platelets distributed
uniformly in the matrices, and the degree of dispersion was
better in PE1 composites. Due to efficient heat transfer to the
filler platelets owing to their better dispersion in PE1, the
highest extent of improvement in the initiation of degradation
temperatures was observed. PE1 composite with 4 % filler
fraction was observed to be have initiation delayed by
?
40 °C as compared to pure polymer. Due to the higher degree
of crystallinity, PE1 had higher tensile modulus of 1334 MPa,
which was improved to maximum extent of 35 % in the com-
posite with 4 % filler content. Thus, the mechanical properties
were enhanced due to combination of crystallinity and filler
effect. The peak stress as well as elongation of the composites
was improved in most cases as compared to pure polymers.
The high temperature modulus of the composites was also
improved on addition of graphene, with PE1 composites
exhibiting the highest magnitude of modulus. The PE1 com-
posites also exhibited lowest melt viscosity among the com-
posites probably due to the lower degree of entanglements,
which indicated ease of processing similar to the pure
polymer.