Thermal and Mechanical Properties of PET Copolymer Containing Bis(dimethyl hydroxyethyl) Tetraspiro Undecane

Abstract

PET-BDHTU copolymers containing bis(dimethyl hydroxyethyl) tetraspiro undecane (BDHTU) were prepared with various BDHTU concentrations. The glass transition temperature of copolymer was increased from 70 degrees C for PET to 93 degrees C for PET-BDHTU copolymer containing 20 mol% of BDHTU. The heat deflection temperature was increased from 60 degrees C to 69 degrees C with the same BDHTU concentration. The impact strength was also increased from 8.4 J/m for PET to 13.2 J/m for PET-BDHTU copolymer containing 5 mol% of BDHTU. The effect of BDHTU on the Young's modulus was not observed, but the yield stress decreased from 66.3 MPa for PET to 21.9 MPa at 20 mol% loading of BDHTU. These resulted from the difficulty of the segmental motion of the main chain of the copolymer due to the bulky and rigid structure of tetraoxaspiro undecane of BDHTU. The optical transparency of copolymer was not changed with BDHTU concentration.