Rheological/thermal properties of poly(ethylene terephthalate) modified by chain extenders of pyromellitic dianhydride and pentaerythritol

Due to low molecular weight and wide molecular weight distribution, polyethylene terephthalate (PET) shows weak melt strength properties. In this study, the synergistic effect of using different types of chain extenders and catalyst on rheological behavior of PET has been investigated. Long-chain branching is known as a suitable method for developing the structure of PET during reactive melt processing. Thus,pyromellitic dianhydride(PMDA) and pentaerythritol (PENTA) were added to the fiber grade PET. The best formulation was determined based on rheological results, which revealed an improvement in both storage modulus and complex viscosity of PMDA-modified samples. Samples containing 1.5% PMDA and 0.5% PENTA exhibited the best rheological properties. Also, dibutyltin dilaurate (DBTDL) acted as an accelerator for chain extension reaction during reactive melt blending. Subsequently, the rheological properties were improved by increasing the chain extending rate. Moreover, thermal properties such as crystallization and melting temperatures and the degree of crystallinity for modified PET were investigated by differential scanning calorimetry.

Automated summary

This study investigated the synergistic effect of different chain extenders and catalysts on the rheological behavior of PET, finding that a combination of PMDA and PENTA at 1.5% and 0.5% respectively resulted in the best rheological properties for modified PET. Additionally, DBTDL acted as an accelerator for chain extension reaction, improving the rheological properties of PET by increasing the chain extending rate. Thermal properties of modified PET were also studied using differential scanning calorimetry.