The data given in this table indicate that the Young’s modulus
decreased by a factor of 1.5 after 60 h under irradiation. A good
agreement was obtained between the values given by DMTA and
those calculated from the AFM indentation measurements. These
sets of data confirmed that notable chain-scissions reactions
occurred, even at the extreme surface of the polymer. Whatever the
investigated scale, the mobility increased with irradiation time.
Chain-scissions provoke an increase of the chain mobility and are
not expected to provoke an increase of the Young’s modulus for
example, the increase of the mechanical properties of celluloid that
was monitored by microhardness and AFM should then be linked to
the loss of the plasticizer during irradiation. A chemi-crystallization
process could also lead to an increase of the mechanical properties.
Any change in crystallinity of the irradiated samples was checked
by DSC analysis (not shown) but as no changes of crystallinity and
no new crystallites were observed, this hypothesis of chemi-crystallization
was ruled out.