Chemical modification as a strategy to modulate properties of oxypropylated products

Abstract

Nowadays a great interest is devoted to the production and use of biobased products. The main scope of the oxypropylation process is to obtain polyols, in the form of viscous liquids, which can be interesting co-monomers to produce polyurethanes and polyesters. Due to the high hydroxyl content of natural polymers (suitable substrates to be oxypropylated), the generated polyols are multifunctional, hence most adequate to be used in rigid polyurethane foam formulations. Additionally, their properties can be modulated through chemical modification, thus opening new avenues for their exploitation. Following that strategy, an oxypropylated product (IOH of 350) used as a model polyol, was modified by reacting it with a mixture containing phenyl isocyanate (PI) and toluene diisocyanate (TDI) at PI/TDI molar ratios of 100/0, 80/20, 50/50, 20/80 and 0/100. This chemical system was chosen in order to guarantee a homogeneous medium during the course of the reaction. Syntheses were performed in dichloromethane solution at room temperature under nitrogen, using DBTDL as catalyst, with a reaction time of 6 hours. Kinetics was followed by FTIR in transmittance mode using a liquid cell equipped with NaCl windows. For that purpose, sample aliquots were taken from the reaction medium at time intervals of 10 minutes during the first hour, 30 minutes during the second hour and at one hour intervals until the end of the reaction. After the established reaction time of 6 hours, residual isocyanates were neutralized with methanol and the final product purified, dried and characterized by FTIR and DSC.To FCT (project PTDC/CTM/71491/2006_FCOM-01-0124-FEDER-007156) and LSRE (strategic project PEst-C/EQB/LA0020/2011)