Influence of Branch Side‐Chains on the Foaming Properties of Thermoplastic Polyether Ester Elastomers in Supercritical <scp> CO ₂ </scp>

ABSTRACT Ester‐based polymers are widely used in numerous applications today. However, thermoplastic polyether ester elastomer (TPEE), despite being an ester‐based elastomer, is typically unsuitable for lightweight applications due to its limited foamability, caused by low melt strength and a narrow molecular weight distribution. This study performed a series of TPEE modifications using a methyl‐branched diol (neopentyl glycol) as the monomer and a tri‐block polymer (ENHOL BE‐3520) as the soft segment. Adjustments to the methyl‐branched diol content notably impacted the thermal properties of the TPEE. All modified samples demonstrated decomposition temperatures exceeding 300°C at 5% weight loss, and melting temperatures ranging from 159°C to 219°C. Tensile strengths varied between 14.66 and 22.96 MPa, while the foam samples achieved expansion rates of 1.50% to 2.45% at temperatures 5°C below the melting point, and 2.19% to 3.88% at 10°C below the melting point. These modifications resulted in TPEE foams with enhanced mechanical properties and stable structures, significantly expanding their potential applications.