Crosslink density of oligourethane diols cured with amino resin at different temperatures

✍ Scribed by Haseebuddin, Syed; Raju, K. V. S. N.; Yaseen, M.

• Publisher: John Wiley and Sons
• Year: 1997
• Tongue: English
• Weight: 258 KB
• Volume: 44
• Category: Article
• ISSN: 0959-8103
• DOI: 10.1002/(sici)1097-0126(199712)44:4<453::aid-pi848>3.0.co;2-f

✦ Synopsis

Oligourethane diols were crosslinked with melamine formaldehyde (N, N,N@,N@,NA,NA-hexakis (butoxymethyl)-2,4,6-triamino-1,3,5-triazine). Their Ðlms were wetted with dichloromethane and the increase in dimensions of the swollen Ðlm under equilibrium swelling conditions was used to calculate crosslink density by using the FloryÈRehner equation. The molar mass between two crosslinks was also determined. The crosslink density of the coating is found to be M 1 c inÑuenced by a trans-etheriÐcation reaction as well as by self-condensation of the crosslinker. In formulations containing primary hydroxylated diol a major part of the crosslinker is consumed in a trans-etheriÐcation reaction, whereas a part of the crosslinker undergoes self-condensation in formulations containing secondary hydroxylated diols. The aromatic nature of 4-methyl-m-phenylene diisocyanate (TDI) imparts rigidity while the aliphatic nature of 5-isocyanato-1-(isocyanatomethyl)-1,3,3-trimethylcyclohexane (IPDI) results in Ñexibility of the backbone. The formulations containing 30% crosslinker and cured at 140¡C for 20 min are found to undergo completion of the major part of the reaction, indicating ideal conditions for their crosslinking from a commercial point of view.