Hydrophobic epoxy resins modified by low concentrations of comb-shaped fluorinated reactive modifier

Abstract

Novel comb-shaped fluorinated (meth)acrylate copolymer was synthesized and used as reactive modifier for epoxy resins. The chemical structure of the comb-shaped fluorinated reactive modifier (CFRM) was characterized by GPC, FTIR and 1HNMR. In addition, a random fluorinated reactive modifier (RFRM) which possessed the same chemical composition but random structure was developed as a contrast modifier. Thorough performances of the modified thermosets modified with these two modifiers were investigated. Surface energy, surface composition and surface morphology were investigated by means of contact angle test, X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM). Compared to the CFRM with RFRM, epoxy thermosets modified with CFRM performed lower surface energy, higher fluorine atomic concentration at the surface and rougher surface morphology. The thermosets modified with CFRM possessed even lower surface energy (18.32 mN/m) than polytetrafluoroethylene (18.50 mN/m) with just adding 0.05 wt% fluorine component (DFHMA structural unit), indicating its high efficiency and effectivess in improvement of surface hydrophobicity. Tensile strength tests and glass transition determined by dynamic mechanical thermal analysis (DMTA) showed that both tensile strength and Tg decreased slightly by incorporation of the two reactive modifier since the sofer segments were incorporated. And thermosets modified with CFRM performed slightly lower Tg than that of RFRM. The influence of the reactive modifier on Shore D hardness and thermal stabilities was not significant due to the low concentrations. The incorporation of the CFRM was more advantageous to lowering water absorption while the optical transmittance deteriorated. The hydrophobic epoxy resins modified with comb-shaped fluorinated reactive modifier might have the potential application in anti-fouling coatings and other occasions requiring low surface energy.