Hybrid uv-curved coatings containing montmorillonites
|Roberta Bongiovanni 1, Daniele Mazza , Aldo Priola , Silvia Ronchetti , Elisa A. Turcato|
1. Politecnico di Torino - Dipartimento di Scienze dei Materiali e Ingegneria Chimica, C.so Duca degli Abruzzi 24, Torino 10129, Italy
This work describes the preparation and characterisation of new coatings based on UV-curable resins intercalated into phyllosilicates.
The UV-curing process was employed to produce such materials in form of films, as it is a fast and environmentally friendly technique.
Two types of montmorillonites were used: a montmorillonite in the sodium form (Cloisite® Na+ CEC = 92.6 meq/100 g) and an organophilic montmorillonite (Cloisite® 30B CEC = 90 meq/100 g, where the functionalisation is made with a dihydroxyethyl octadecyl methyl ammonium chloride). The fillers were dispersed in 3,4-epoxycyclohexylmethyl-3’,4’-epoxycyclohexilcarboxylate, (CE) or in a waterborne polyurethane acrylate resin (Ucecoat 6558 by UCB) at a maximum concentration of 5% w/w, with the aid of an ultrasonic bath. The mixtures containing the oligomer together with the clay were then added of the proper photoinitiator at 2-4% w/w. They were exposed to UV light and films 200 micron thick were obtained. Before and after the photopolymerization, the hybrid systems were investigated by XRD analysis. The system made of CE and Cloisite® 30B showed the expected intercalation with an increase of the interlamellar spacing d001 from 18.5Å of the powder to 34.6Å in the CE oligomer. Similar results were obtained with the Cloisite Na+ in the acrylic system: the interlamellar spacing d001 moved from 12.1 Å of the powder to 18.6 Å in the oligomer.A further confirmation of the intercalation was obtained by TEM analysis.
After the UV-curing no further change in intercalation occurred. The presence of the organophilic montmorillonite affected the polymerisation process of the epoxy oligomers which react via a cationic mechanism. The decrease of the conversion rate in the cationic polymerisation of CE was due to the basicity of the quaternary ammonium salts impurities in the clay: they reduced the activity of the photoinitiator acid fragments produced under irradiation.
Presentation: oral at E-MRS Fall Meeting 2005, Symposium E, by Roberta Bongiovanni
See On-line Journal of E-MRS Fall Meeting 2005
Submitted: 2005-05-19 15:16 Revised: 2009-06-07 00:44