Ammeline–melamine–formaldehyde resins. Preparation and properties

Ammeline–melamine–formaldehyde resins (AMF Resins) containing 5–100 mol % of ammeline, were synthesized by polymerization of the preformed sodium salt of ammeline, melamine, and formaldehyde in basic medium by three methods. These resins, when cured, constitute a new class of thermosets. The rate of hydroxymethylation of the amino groups of the ammeline salt with formaldehyde was somewhat larger then that of the amino groups on melamine. At higher pH values ammeline insolubility was not a problem. The AMF resin composition was approximately equal to the mol ratio of the components originally charged. Both ammeline and melamine were consumed over the entire reaction period. Thus, it is possible to make approximately uniform random ammeline-melamine-formaldehyde resins (AMF) with any mol ratio of ammeline salt to melamine. By controlling the pH of the solution from which the resins were isolated, the (SINGLE BOND) O⁻ Na⁺/(SINGLE BOND) OH ratio could be varied. Resin melting points varied widely with the mol fraction of ammeline and the (SINGLE BOND) O⁻ Na⁺/(SINGLE BOND) OH ratio. AMF resin solubilities, shelf lives, cloud points, and water tolerance depended upon the method of preparation, pH, and other factors. The sodium salt of ammeline was hydroxymethylated in water more readily than ammeline. More highly methylolated ammeline species were readily formed in solution but upon precipitation only bis-N-hydroxymethylammeline was isolated. © 1996 John Wiley & Sons, Inc.     

Macromol. Biosci. 1/2013

Front Cover: Highly aligned 3D silk scaffolds using directional freezing in a custom designed chamber was demonstrated. The method is versatile and holds potential to produce complex, multicomponent aligned structures for various tissue engineering and biomedical applications, needing immediate cell alignment to mimic native tissue hierarchy and function. Further details can be found in the article by B. B. Mandal, E. S. Gil, B. Panilaitis, and D. L. Kaplan* on page 48 .