Effects of the electron‐beam absorption dose on the glass transition,thermal expansion,dynamic mechanical properties,and water uptake of polycardanol containing epoxy groups cured by an electron beam

In this study, the glass transition, thermal expansion, dynamic mechanical properties, and water‐uptake behaviors of diepoxidized polycardanol (DEPC) cured by electron‐beam radiation in the presence of cationic photoinitiators were investigated. How the type and concentration of cationic photoinitiators and the electron‐beam absorption dose influenced the properties of the cured DEPC was also studied. Two types of cationic photoinitiators, triarylsulfonium hexafluorophosphate (simply referred to as phosphate type or P‐type) and triarylsulfonium hexafluoroantimonate (simply referred to as antimonate type or Sb‐type), were used. Electron‐beam absorption doses of 200, 300, 400, and 600 kGy were applied to the uncured diepoxidized cardanol (DEC) samples, respectively. It was revealed that the Sb‐type photoinitiator was preferable to the electron‐beam curing of DEC; this led to a lower photoinitiator concentration and/or a lower electron‐beam absorption dose compared to that in the phosphate‐type photoinitiator. As a result, the variations in the glass‐transition temperature, coefficient of thermal expansion, storage modulus, and water uptake of the cured DEPC were quite consistent with each other. We found that the optimal conditions for the enhanced properties of DEPC by electron‐beam curing were an Sb‐type photoinitiator at 2 wt % and an electron‐beam absorption dose of 600 kGy. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42570.