Development of Cure Bonding between Chlorosulfonyl Polyethylene and Fluoroplastics

Abstract

The cure bonding between chlorosulfonyl polyethylene (CSM) and fluoroplastic (terpolymer of tetrafluoroethylene, hexafluoropropylene and vinylidene fluoride) has been developed. In the case of cure bonding of chlorinated polyethylene by trithiocyanuric acid (TCA), the difference in accelerator, such as tetra-n-butylphosphonium benzotriazolate and 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU) salts, did not influence on cure bonding, however, the presence of water was found important to get high bonding strength. Thus the addition of sodium acetate trihydrate that releases water of crystallization during cure bonding significantly improved the bonding strength.For compounds of conventional CSM having 1 wt% of sulfur in the chlorosulfonyl group as a cross-linking site with sodium acetate trihydrate and TCA, their viscosity became too high to be mill mixed and molded, when an accelerator DBU salt such as formate or benzoate having a melting point below milling temperature, 130 °C, was used. DBU salts having melting points above milling temperature, such as trimellitate and pyromellitate, showed poor cure bonding.A compound of CSM having 0.3 wt% of sulfur in the chlorosulfonyl group with TCA, DBU phenolate and sodium acetate trihydrate was able to be mill mixed, molded and cure bonded. The vulcanizate satisfied the specifications of automotive fuel hoses.