Investigation of interpolymer complexation between Carbopol and various grades of polyvinylpyrrolidone and effects on adhesion strength and swelling properties

Purpose. To investigate the interpolymer complexation between Carbopol 934P (CP) and various grades of polyvinylpyrrolidone (PVP) (K90, K32, C15, and VA/S-630). Methods. Amount of fresh and dried CP-PVP complexes, water retai ning capacity, apparent density, pH, conductivity, FTIR, swelling and adhes ion strength were studied. Results. Interpolymer complexation occurred betw een CP and all the PVP, but most significantly with PVP K90. Maximum amount of fresh and dried CP-PVP K32 complexes were obtained at a weight ratio of 1:1. On the contrary, CP concentration was linearly related to amount of C P-PVP K90 complexes produced and their water retaining capacity were all ab ove 97%. Increase in CP concentration caused a decrease in pH, but an incre ase in conductivity for all the CP-PVP complexes. The apparent density of t he filtrate of CP-PVP K90 complex was the lowest and its IR spectrum was si milar to that of pure PVP K90, indicating that all the CP has interacted wi th the PVP K90. Discs of physical mixtures of CP-PVP K90 swelled gradually and reached a maximum after 20-30 hr, while discs of solid complex swelled readily and reached a maximum within 20 hr. Adhesion strength was directly correlated to CP content. However, adhesion strength of solid CP-PVP K90 co mplex was lower than the physical mixture of the pure polymers. Conclusion. Interpolymer complexation occurred between CP and PVP but to a different e xtent for the various grades of PVP. Complexation was most prominent betwee n CP and PVP K90.