Preparation and properties of natural rubber grafted with poly (Butyl Acrylate-CO-Fluorinated Acrylate)

Abstract

Graft copolymerization of 2,2,2–trifluoroethyl methacrylate (3FMA) onto natural rubber (NR) was synthesized in an emulsion system by using potassium persulfate (K2SO4) as an initiator. Since the polarity of NR and 3FMA monomer was different, the 3FMA monomer could not be directly grafted onto the NR structure. Thus, butyl acrylate (BA) was selected as a co-monomer to enhance the grafting efficiency (GE) of this system. The chemical structure of NR before and after graft copolymerization was detected by using attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) and nuclear magnetic resonance spectroscopy. The effects of initiator concentration, BA/3FMA wt ratio, reaction temperature and reaction time on monomer conversion, grafting properties and GE of the graft NR (GNR) were investigated. The maximum content of NR-g-poly(BA-co-3FMA) at 72.8 wt% was obtained by using 30/70 (w/w) BA/3FMA and 1.5 phr K2SO4 at 60 °C for 8 h. This condition provided GNR with 25.3 mol% grafted 3FMA content and 68.5% GE. The latex of the graft product exhibited the core-shell morphology. The thermal properties, mechanical properties, contact angle and surface energy were analyzed to evaluate the effect of the addition of graft product on the compatibility between NR and poly(BA-co-3FMA) phases in the NR/poly(BA-co-3FMA) films (20/80 (w/w)). The results revealed that the addition of 10 wt% GNR enhanced the compatibility of the polymeric constituents in the films resulting the improved hydrophobicity with high contact angle (109°) and higher toughness. Moreover, the oil swelling resistance of obtained film was higher than that of the commercial self-sealing film using in the laboratory, Parafilm MR.