Tailoring Hydrophobic PDMS –Polyesters: Effects of Molecular Weight and Dispersant on Structure and Thermal Properties

ABSTRACT A series of hydrophobic polyester blends based on poly(ethylene terephthalate) (PET) was prepared via an in situ melt‐blending process during polycondensation, incorporating terephthalic acid (TPA), ethylene glycol (EG), and PDMS of different molecular weights (6000, 60,000, and 100,000 g/mol) via the TPA‐based polycondensation method. Magnesium stearate (SMg) was employed as a dispersant to enhance the hydrophobicity of the resulting modified polyesters. The effects of PDMS molecular weight on the structural, morphological, and thermal properties of the resulting blends were systematically investigated using Fourier‐transform infrared (FTIR) spectroscopy, x‐ray diffraction (XRD), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC). The results revealed that increasing PDMS molecular weight improved the toughness, initial thermal decomposition temperature ( T d5 ), water contact angle, and surface gloss of the PDMS‐modified polyesters, while reducing their crystallinity. The sample containing the highest PDMS molecular weight exhibited the greatest thermal stability, with a decomposition temperature of 396°C. Among all compositions, the M60 PDMS‐modified polyester demonstrated an optimal balance between mechanical strength and thermal stability, indicating its potential for high‐performance hydrophobic material applications.