The Interaction of Polyvinylalcohol/Acetate with CA, C₃A and C₃S in MDF Materials, as Described by Spin-Propagation Across Heterogeneous Interfaces

Abstract

Proton relaxation times, measured both in the laboratory T₁(H) and in the rotating T₁p(H) frame, were exploited for the study of the intimacy of the polymer matrix to the inorganic components in MDF cements. The spectra were detected, under high resolution conditions, by polarization transfert to ¹³C nuclei. The spin-diffusion phenomena across the heterogeneous interface, equilibrating with time the excited spin populations in the hydrogen containing phases, was followed from the point of view of the polymer. In particular, MDF composites based on aluminate cement and a polyvinylalcohol/acetate copolymer were compared with silicon based composites. In general, the behavior of the composite based on CA highlights the better mixing and interaction between the phases as compared to C₃A and C₃S MDF materials. The spectra were also run in order to observe the atomic environments of the carbon nuclei. An analysis of the intramolecular hydrogen bonds showed a stronger modification in the sample containing CA than in those containing C₃A or C₃S. Deacetylation occurred, and interaction was observed between acetate groups and the calcium and aluminum ions. An extended interphase was identified in the composite containing CA.