Flexible epoxy composite coatings modified by reactive rubber with improvements in water and corrosive resistances

Epoxy composites were modified by reactive polybutadiene, and their resistance to T-bend and liquid permeation was evaluated to develop flexible epoxy composite coatings with good resistance to corrosive media. The composites’ resistance to bending on galvanic sheets was improved with the addition of up to around 15 wt.% amino liquid polybutadiene (ALPB) as reflected by the cross-section images after bending tests and bending times at break. The initial impedance increased with the addition of up to 15 wt.% ALPB in the composites, whereas the resistance reduced in a much slow rate with immersion time for the sample containing ALPB at around 10 wt.%. This result suggested that their resisting ability depended on the amount and dispersion of ALPB. The Rc and Cc parameters from the electrochemical impedance spectroscopy measurements revealed that the improvement in resistance to electrolyte resulted from the compactness increment at certain range of ALPB additions, which was also supported by their water uptake trends. Moreover, the addition of ALPB above 20% resulted in severe aggregations and phase separations. The resulting reduced compactness reflects the fact that the excessive reactive rubber addition leads to the negative effects on their resisting ability upon both T-bend and liquid permeation.