Técnicas FT-IR (UATR, PAS e MIC, com objetiva ATR) foram escolhidas para a caracterização da superfície da borracha de EPDM vulcanizada, após tratamento em plasma de Ar/O2 e N2/H2/Ar gerado em micro-ondas. Após tratamento, grupos oxigenados foram detectados por UATR e MIC/FT-IR, com objetiva ATR para as duas misturas gasosas, e possíveis grupos nitrogenados foram inseridos na superfície das amostras tratadas com plasma de N2/H2/Ar. A análise MIC/FT-IR sugeriu a formação de grupos em uma camada mais externa, para as amostras tratadas com plasma de N2/H2/Ar, sendo possível observar a redução na intensidade das bandas da absorção do CH2 e CH3, o que pode estar relacionado ao fato de o nitrogênio ser um gás menos permeável que o oxigênio. Diferentes velocidades, 0,05 cm.s-1 e 0,2 cm.s-1, foram utilizadas na análise PAS para avaliar a superfície após tratamento, e apenas para a velocidade 0,05 cm.s-1 com plasma de Ar/O2 alterações espectroscópicas foram detectadas. A redução na medida de ângulo de contato e o aumento na resistência ao descascamento da colagem indicaram melhoras nas propriedades adesivas da superfície. Falhas de adesão foram observadas entre a interface do filme de adesivo de PU e da borracha de EPDM, e confirmados por UATR/FT-IR.

The FT-IR techniques UATR, PAS and MIC with ATR objective were chosen to characterize the surface of EPDM rubber vulcanized after treatment in Ar/O2 or N2/H2/Ar plasma generated in a microwave oven. After treatment, oxygenated groups were detected by UATR and MIC-FT-IR, with ATR objective for the two gas mixtures, and possible nitrogenous groups were inserted on the surface after the plasma treatment with N2/H2/Ar. The MIC/FT-IR analysis suggested that groups were formed on an outermost layer, inferred from a reduced intensity of the CH2 and CH3 absorption bands for the treatment in N2/H2/Ar plasma, probably because nitrogen is less permeable than oxygen. Different speeds with PAS analyses (0.05 cm.s-1 and 0.2 cm.s-1) were used to evaluate the surface after treatment. Only for the speed 0.05 cm.s-1 in Ar/O2 plasma were spectroscopic changes detected. The decrease in the contact angle and the increased resistance to peel indicated improvements in the bonding adhesive properties of the surface. Bonding failure was observed between the adhesive PU film and the EPDM rubber, which was confirmed by UATR/FT-IR.

ABSTRACT: The surface of vulcanized ethylene propylene diene terpolymers (EPDM) was modified by Ar and N2, microwave generated plasma in order to improve adhesion properties. Surface modification was characterized by universal attenuated total reflectance Fourier Transform Infrared (UATR/FT-IR), because it presented lower interference of ingredients of EPDM formulation when compared with other techniques used for the attenuated total reflectance (ATR) to different crystals (ATR/KRS-5 and ATR/Ge). Oxygenated groups were introduced on the surface after treatments which were formed when the activated surface was exposed to the plasma gas. In treatments with nitrogen, oxygen groups and probable nitrogen groups were formed on the surface and could be identified by FT-IR. Reduction in the measurement of the contact angle and an increase in the work of adhesion and in the peel strength (EPDM X Polyurethane (PU)) were observed after the treatment resulted in the improvement of the adhesion properties of the modified surface.