REACTION OF POLY(VINYL ALCOHOL) AND DIALDEHYDES DURING GEL FORMATION PROBED BY H-1-NMR - A KINETIC-STUDY

Proton n.m.r. has been used to study the reaction between poly(vinyl a lcohol) (PVA) and two different dialdehyde crosslinkers during gel for mation (gels for improved oil recovery applications). The rate of form ation of covalent bonds between PVA and glutaraldehyde in acidic salin e water solutions was found to be of first order with respect to both the Hf concentration and the formal dialdehyde concentration. The acti vation energy was found to increase with increasing dialdehyde concent ration and increasing pH (3.2-4.7). The corresponding reaction rate of formation of covalent bonds between PVA and butenedial in the PVA/2,5 -dimethoxy-2,5-dihydrofuran system at the same pH and temperature was found to be an order of magnitude less. Also, the activation energy wa s higher by approximately 50% as compared with the PVA/glutaraldehyde system. Possible reaction pathways for the generation of PVA-dialdehyd e gels are discussed. (C) 1997 Elsevier Science Ltd.