Study On The Synthesis Of Active Group-Terminated Polyether And Its Application In Toughening Epoxy Resin

Multi-mercapto-terminated polyether (MTPE) is a novel mercapto-terminated polymer with polyether structure as its backbone. Owing to its excellent flexibility and ageing properties such as oil resistance, chemical resistance and ultraviolet resistance, MTPE is recognized as an ideal material utilized to prepare sealants and adhesives. Polyether is first halogenated and then reacts with MSH (such as NaSH and KSH) and M₂S_x to obtain MTPE via chlorine-removing reaction. During the reaction, MSH melts and is apt to assemble together, which results in difficult control of the reaction. Therefore, it is of great significance to study systematically the synthesis of MTPE and its application in sealants and adhesives.MTPE was synthesized first by the reaction of hydroxyl-terminated polypropylene with epichlorohydrin and then reacted with NaSH and Na2Sx in solvent of alcohols.. The structure of chlorine-substituted polyether and MTPE were characterized by NMR . The remained epoxy group content in the reacting system was measured by hydrochloric acid -acetone method to trace the reaction process. The SH group content in MTPE was tested by argentimetry and the molecular weight of reactants was also determined by GPC. The processing stability of synthesis of MTPE was studied . The influence of MTPE, on the physical properties and bonding property of epoxy systems (E51/TETA, T-31 or 593) was studied in order to compare with commercial polyetheramine (D-2000).Results showed that alcohols were an ideal solvent for chlorine-removing reaction smoothly and NaSH and Na2Sx could disperse evenly in alcohol. The etherification of epichlorohydrin is first order reaction and the constant A is 0.995476 and active energy Ea is 21.700538 kJ. The SH group content of resultant MTPE reached its maximum when the reactant concentration, -SH/-Cl ratio and reaction time were adjusted carefully, taking account of the possibility of side reaction.As a toughening agent, MTPE is better than polyether amine in both TETA and T-31, 593 cured epoxy systems. MTPE-introduced systems had better physical properties and bonding properties than PEA introduced-ones.The toughening of epoxy system (E51/DETDA) with silylated polyurethane (SPU) was also studied in this paper. SPU was first prepared and then was used in epoxy system (E51/DETDA). The compatibility, morphology and microstructure of the epoxy system were studied by DMTA and SEM and the tensile, flexural, impact strength of the system were tested. Results showed that micro-phase separation took place clearly in SPU added epoxy system. The tensile, flexural, impact strength reached maximum when SPU content is 10～12 phr. Therefore, SPU is a reinforcing agent as well as a toughening agent for epoxy system.