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.
Highlights
ethylene propylene diene terpolymers (EPDM) rubber became an interesting alternative as a thermal protection for rocket motors because of its low density, low processing cost and because it does not produce toxic compounds while burning, showing advantages in relation to nitrile butadiene rubber (NBR), the copolymer, which is normally used for this application (Moraes et al, 2007a)
Study by FT-IR Technique and Adhesive Properties of Vulcanized EPDM Modified with Plasma 67. In this analysis we present the study of surface modification by microwave plasma system, the EPDM rubber with known diene and ethylene content, in which new active groups incorporated on the surface were characterized by UATR, and the evaluation of the adhesion (EPDM versus PU) through T-peel strength of the adhesive joint and goniometry
Bands that characterize the EPDM rubbers are found in their wavenumbers, attributed to their vibrational modes: asymmetrical stretching of the CH2 group at 2,920 cm-1, symmetrical stretching at 2,850 cm-1, asymmetrical and symmetrical bending of CH3 at 1,460 cm-1 and 1,377 cm-1, respectively, and in plain bending or rocking (ρ) of CH2 at 721 cm-1 (Awaja et al, 2009; Babbit, 1978; Basak et al, 2010)
Summary
EPDM rubber became an interesting alternative as a thermal protection for rocket motors because of its low density, low processing cost and because it does not produce toxic compounds while burning, showing advantages in relation to nitrile butadiene rubber (NBR), the copolymer, which is normally used for this application (Moraes et al, 2007a). With the purpose of improving this characteristic, surface treatment is required (Rapra Review Reports, 2002), without modifying the bulk properties of the polymer (Hegemann et al, 2003; Viadaurre et al, 2002). Plasma treatments are alternatives to reach these characteristics, besides being harmless to the environment (Costa et al, 2008). The disadvantage of plasma is that it requires a vacuum system, increasing the cost of the treatment (Moraes et al, 2007b). The consulted literature mentions some studies in which plasma treatments were used in EPDM and the characterization of the effect on the surface of the elastomer, approaching, in some cases, the sensitivity of the techniques used (Moraes et al, 2007a; Grythe and Hansen, 2006; Awaja et al, 2009)
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