The Effect of Molecular Complexes of Lactam-Containing and Proton-Donor Substances on the Adhesion Properties of Adhesive Composites

Abstract

The results of investigating the effect of a molecular complex (MC) based on a lactam-containing product and a hydroxyl-containing compound on the adhesion properties of elastomeric adhesives are set out. The MCs comprise binary melts based on triatomic alcohol (TA) and ε-caprolactam. An MC was introduced into an adhesive based on chloroprene rubber in different ratios together with the isocyanate 4,4’-methylenediphenyl diisocyanate (MDI). The adhesion activity of the MC was assessed from the bond strength between the elements in rubber–cord composites (a rubber compound based on BNKS-40AMN nitrile butadiene rubber + cord coated with a rubber mix based on general-purpose rubbers according to GOST 6768-75). Comparison of the IR spectra (FSM 1201 IR Fourier spectrometer) of the MC and its individual constituents makes it possible to suggest the presence of hydrogen bonds in the MC. Analysis of NMR spectra (Bruker Avance-400 NMR spectrometer) of the MC showed the absence of new chemical bonds between its components. Theoretically, a binary MC introduced into an adhesive composite together with isocyanate should promote an increase in the bond strength between the substrates through the formation of urethane groups. The results of testing the MC in the composition of adhesives showed that a higher bond strength is possessed by rubber–cord specimens with a ratio of TA and ε-caprolactam of 2:1. The introduction of an MC together with MDI leads to a 25% increase in adhesion strength in the adhesive joint.