As many other TP, PET was demonstrated to be partially miscible
with epoxy resins,ER[3–5]. In this respect, to dissolve the amorphous
PET is desirable. To obtain epoxy materials, preferably adhesives and
reinforced composites, ER must react with proton-donor substances
called hardeners. The reaction between ER and hardeners leads to
crosslinked networks with excellent thermal resistance and resistance
to water and organic solvents, good adhesion to different
substrates, high Tg, tensile strength and modulus, etc. [6–9]. The
brittle fracture and low impact strength are the disadvantages of
epoxies. The addition of initially soluble TP is consciously used to
improve the toughness of epoxy materials [10–21]. The cited
references comment DGEBA modified ER having weight average
molecular mass, Mw, within the range 340–390 kg kmol1
. We also
used such ER in this study. A more extended reference list of TP
modified epoxies can be found in some reviews, e.g., [10,11], where
higher functionality ERwere discussed togetherwith those based on
DGEBA. The hardeners for TP modified epoxies are typically
aromatic diamines, which react with DGEBA at relatively high
temperatures. It is known that higher temperature facilitates the
solubility of a polymer in solvents, as well as the mutual solubility
between two polymers [22]. DDS was used as a hardener, while the
TP modifier was a recycled PET from the bottle industry.