| Abstract: | The 73/27 4‐hydroxybenzoic acid (HBA)/2‐hydroxy‐6‐naphthoic acid (HNA) copolyester was prepared by the inclusion of two crosslinkable oligomers. These systems were synthesized by melt polymerization and characterized using differential scanning calorimetry, thermogravimetric analysis, polarized optical microscope and wide‐angle X‐ray diffraction. The transition from thermoplastic to thermosetting character occurred when 10 wt% or above of oligomer was added to the 73/27 HBA/HNA random mixture. The melt rheology of the HBA/HNA copolyesters containing two oligomers was investigated. The copolyesters displayed an increase in complex viscosity and transition from liquid‐like to solid‐like behavior as the oligomer content increased, and finally there was no melting transition when the oligomer content reached 10 wt%. Shear storage modulus measured by a dielectric mechanical analysis decreased slightly with increasing oligomer content. An adhesive test using an aluminum sheet revealed an increase in the lap shear strength up to 5 wt% of oligomer content without a significant reduction in shear storage modulus. On the other hand, the 73/27 HBA/HNA containing 10 wt% oligomer displayed a dramatic decrease in lap shear strength. Copyright © 1999 John Wiley & Sons, Ltd. |
