Caraterização composicional do AES - um copolímero de enxertia de poli(estireno-co-acrilonitrila) em poli(etileno-co-propileno-co-dieno)

Abstract

O objetivo deste trabalho é a caracterização do AES, um copolímero de enxertia de poli(estireno-co-acrilonitrila), SAN, em poli(etileno-co-propileno-co-dieno), EPDM. Para tanto, o AES foi submetido à extração seletiva de seus componentes: o SAN livre, o EDPM livre, e o copolímero de enxertia EPDM-g-SAN. O AES e suas frações foram caracterizados por espectroscopia de infravermelho, análise elementar, calorimetria diferencial de varredura e ressonância magnética nuclear, RMN¹H e RMN13C. O AES analisado apresenta a seguinte composição em massa: 65% de EPDM-g-SAN, 13% de EPDM livre e 22% de SAN livre. O EPDM apresenta 69,8% em massa de etileno, 26,5% em massa de propileno e 4,6% em massa do dieno, 2-etilideno-5-norboneno, ENB. O SAN apresenta razão em massa acrilonitrila/estireno de 28/72 e distribuição randômica de comonômeros de estireno e acrilonitrila. Estes resultados são concordantes com a composição do AES fornecida pelo fabricante, indicando que a metodologia proposta é adequada.

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“…The EPDM phases of all blends present a glass transition temperature at lower temperatures than the EPDM phase of AES (Figure 6(b)). This behavior was also observed in earlier work of our research group for polyhydroxybutyrate/AES blends,32 PMMA/AES blends 15, in situ polymerized polystyrene (PS)/AES 33 and PS/EPDM 34. This shift to lower temperatures is attributed to the phase inversion of the EPDM phase of AES due to AES dissolution in methyl methacrylate monomer and its in situ polymerization.…”

“…EPDM is the matrix in AES (Figure 7(a)), whereas SAN and EPDM‐g‐SAN chains constitute the dispersed phase (Figure 7(a)). In the blends, EPDM becomes the dispersed phase (Figure 7(b)), and the release of the SAN chains from the elastomeric phase can contribute to the decreases in the EPDM glass transition temperatures 15. This behavior in blends of a rubbery phase dispersed in glassy material is common and attributed to hydrostatic dilatational thermal stresses generated within the rubber particles because of the differences in the thermal expansion between the rubber and the glass matrix.…”

“…The spectra of the three fractions present the similar bands. The spectra present the characteristic absorption bands of polyolefin (1377 cm −1 ), intense bands of symmetric deformation of CH 3 (1464 cm −1 ), two characteristic absorption bands of symmetric and antisymmetric stretching of EPDM (2860 and 2950 cm −1 ),16, 22 and characteristic absorption bands of poly(methyl methacrylate) (1724 and 1390 cm −1 ) 23. In these spectra, the absorption bands of the acrylonitrile group of SAN (2237 cm −1 ) was not observed for the 6.9EPDM blend, because of the low SAN contents.…”

“…The global composition of AES is 50 wt% of SAN and 50 wt% of EPDM. The EPDM of AES contains 68.9 wt% of ethylene, 26.5 wt% of propylene and 4.6 wt% of 2‐ethylidene‐5‐norbornene (ENB) as diene 16…”

“…In this system, the graft copolymer EPDM‐ g ‐SAN molecules act as compatibilizers between SAN and EPDM phases. Turchet15 prepared PMMA/AES blends by mechanical mixing and obtained a toughened blend with 30 wt% of AES. This blend exhibited an increase of 990% in impact resistance, in comparison with PMMA, and this result is due to SAN compatibilizing effect, improving adhesion and dispersion of EPDM particles in the PMMA matrix.…”