Modification of epoxy polymer by plasticizing, blending, or reinforcing

Epoxy polymer (EP) was modified by incorporation of DBP, PVC, PVA, and glass fiber reinforcement. The morphology of the unmodified polymer and the various blends was studied by SEM, dispersive X-ray analysis, and DSC. Results indicated that EP and DBP are miscible in the proportions used in this work (up to 10% of DBP). PVA added to cured EP in a concentration of 10% occurs as a separate phase. The morphology of EP–PVC blends is relatively complex: EP and PVC are immiscible at low concentration of the second component (up to 10% of PVC), but become mutually and increasingly more miscible as the concentration of PVC increases. Incorporation of DBP into EP causes a marked reduction in the heat distortion temperature (HDT), whereas addition of PVC has only a moderate effect. Modified EP containing small amounts of DBP (up to 4%) has moderately lower bond strength than the unmodified polymer, as evidenced by lower ultimate tensile strength of the adhesion sandwich specimens mounted on aluminum substrate. However, as the concentration of DBP in the blend increases, the ultimate tensile strength is slightly higher than that of the unmodified EP. Blending of EP with PVC, PVA, and glass fibers has generally a detrimental effect on the ultimate tensile strength. Outdoor exposure for 100 days (between January and April) generally caused deterioration of the tensile strength of all samples. EP-based blends containing DBP, however, had better resistance to deterioration in outdoor exposure than the other blends, including unmodified EP.