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C¸ETIN et al./Turk J Chem
1281, 1257, 1143, 1079, and 1010 cm−1 were attributed to C-O stretching vibrations. The bands at about
850, 752, and 668 cm−1 probably correspond to C-H out-of-plane bending vibrations (Figure 3, lines a and
b). In air atmosphere, on the other hand, initial weight loss started to be seen at relatively lower temperatures
in the former homopolymer, at about 235 ◦ C, and at higher temperatures, around 270 ◦ C, in the latter. In
the FT-IR spectra of the decomposition products, although some absorption peaks were commonly observed as
those observed in nitrogen atmosphere, numerous peaks concentrated around 1700 and 1540 cm−1 , which were
difficult to interpret, were observed. The formation of carbon dioxide was identically detected with peaks at
about 2360 cm−1 in almost every stage of decomposition in both polymers.
TGA of the graft coproducts involving 39.4% poly(BPCPA) and 34.5% poly(BPCPMA) carried out
in N2 atmosphere demonstrated that the first weight loss started at earlier temperatures compared to the
homopolymers, around 220 ◦ C in the former and at about 240 ◦ C in the latter coproduct. The FT-IR
spectra additionally displayed the absorption bands, besides those similarly observed in the spectra of the
homopolymers, at about 2966 and 2929 cm−1 , attributed to the stretching vibrations of CH3 and CH2 groups,
and at about 1750 and 1730 cm−1 , assigned to stretching vibrations of the C=O group. In air atmosphere,
while a similar decomposition trend was observed in the former, the initial losses in the latter were recorded at
earlier temperatures, around 225 ◦ C. The FT-IR analysis of the decomposition products displayed relatively
broad bands in the spectra compared to those recorded in nitrogen atmosphere. A number of bands that were
very hard to interpret were observed in the spectra of the poly(BPCPA)-PP coproduct (Figure 3, lines c and
d).
The results revealed that the degradations in the products proceeded predominantly by the breaking up
and decomposition of side groups of poly(BPCPA) and poly(BPCPMA) chains, giving mainly carbon dioxide,
aromatic, and vinylic groups. Methyl and methylene groups were also detected in the decompositions of the
coproducts, apparently due to the breaking up of PP chains. Relatively complex mechanisms prevailed in the
decompositions in air atmosphere.
2.2. Mechanical properties of the graft coproducts
The mechanical properties of the graft coproducts were studied to find out the effect of the graft copolymerization
of BPCPA and BPCPMA onto PP. Although considerable improvements were achieved in elastic modulus,
tensile and impact strength of the coproducts decreased with loss of yield stress and loss in percent elongation,
and the breaking of the products showed their brittle nature.
Stress–strain curves of the graft coproducts are given in Figures 4 and 5 in detail. It is visible from the
figures that although the virgin PP material showed a great extent of cold drawing or orientation, we did not
observe any yield stress behavior in the grafted polymers, and percent elongation consistently diminished with
the graft content. Thus, the surface energy values belonging to the coproducts increase consistently and each
coproduct prepared exhibits perfectly the brittle nature (considerable break of the bonds in the structure). In
other words, the grafting of the homopolymers onto the polypropylene deteriorates the molecular structure of
polymer chains, leading to the damage of the rate-dependent (large-scale) viscoelastic deformation or yielding.
It is another probable result obtained from the present work that more crack growth by chain scission (known
as the fracture on the atomic level) may appear in new systems as a result of either the contraction of the
lattice structure or the decrement of the lattice absorption energy along the crack propagation. In more detail,
only the coproduct prepared with 3.7% poly(BPCPA) broke just at the beginning of plastic deformation due
to the considerable shrink of the lattice structure. As is well known, there are two main bonds involved
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