title: FT-IR and FT-Raman studies of cross-linking processes with Ca²⁺ ions, glutaraldehyde and microwave radiation for polymer composition of poly(acrylic acid)/sodium salt of carboxymethyl starch - In moulding sands, Part II.
abstract: The hardening process of moulding sands on quartz matrices bound by polymer binders containing carboxyl and hydroxyl groups can be carried out by using physical (microwave radiation, thermal holding) and chemical (Ca(2+) cations, glutaraldehyde) cross-linking agents. The highest hardening level obtain moulding sand samples containing binders in a form of the aqueous composition of poly(acrylic acid)/sodium salt of carboxymethyl starch (PAA/CMS-Na) within the microwave radiation field, for which the bending strength is of 1.6 MPa value even after 24h from ending the agent activity. The authors focused, in this study, on finding the reason of this effect. It was shown, by means of the FT-IR and FT-Raman spectroscopic methods, that the chemical adsorption process activated by microwaves plays an essential role. The applied microwaves activate the polar groups present in the polymer composition structure as well as the quartz crystals surfaces (silane groups). Then the chemical adsorption occurs in the binder-matrix system within the microwave radiation field and intermolecular lattices are formed with a participation of hydrogen bridges (SiOH⋯OC, SiOH⋯OH) and COSi type bonds.
authors.affiliation: AGH - University of Science and Technology, Faculty of Foundry Engineering, Reymonta 23, 30 059 Krakow, Poland. Electronic address: beata.grabowska@agh.edu.pl.
authors.forename: Beata
authors.initials: B
authors.lastname: Grabowska
authors.affiliation: AGH - University of Science and Technology, Faculty of Materials Science and Ceramics, Mickiewicza 30, 30-059 Krakow, Poland.
authors.forename: Maciej
authors.initials: M
authors.lastname: Sitarz
authors.affiliation: AGH - University of Science and Technology, Faculty of Foundry Engineering, Reymonta 23, 30 059 Krakow, Poland.
authors.forename: Ewa
authors.initials: E
authors.lastname: Olejnik
authors.affiliation: AGH - University of Science and Technology, Faculty of Foundry Engineering, Reymonta 23, 30 059 Krakow, Poland.
authors.forename: Karolina
authors.initials: K
authors.lastname: Kaczmarska
authors.affiliation: Cracow University of Technology, Faculty of Chemical Engineering and Technology, Department of Chemistry and Technology of Polymers, Warszawska 24, 31-155 Krakow, Poland.
authors.forename: Bozena
authors.initials: B
authors.lastname: Tyliszczak
keywords: Cross-linking; Microwave radiation; Moulding sands; Polymer binders; Spectroscopy