photochemical change (e.g. photo-rearrangement) in that
molecule. Photo-degradation changes the polymer structure
by the scission of bonds, which then substantially
changes the mechanical properties of polymers.
The aromatic rings and ester groups make up the molecules
of the polyester. The C–O bond in the ester group,
with the bond dissociation energy of 351.69 kJ/mol and
corresponding wave length of 340 nm, which falls in the
scope of 315–400 nm (the UV lamp wavelength range in
the research), may be photo-degraded by the UV
irradiation.
The glass fibre contains many oxides, such as Si–O, Al–
O, Mg–O etc. The bonds in the oxides may be broken by
corresponding waves in the UV ray.