Synthesis of aromatic hyperbranched polyester (HBPE) and its use as a nonmigrating plasticiser

A series of aromatic hyperbranched polyesters (HBPEs) were synthesised through one-pot reaction of benzene-1,2,4-tricarboxylic anhydride, diethylene glycol, and methanol. The molecular structure of HBPEs was characterised by ¹H-NMR, Fourier transform infrared spectroscopy, gel permeation chromatography, differential scanning calorimetry (DSC), and thermogravimetric analysis. HBPE was used as plasticiser for poly(vinyl chloride) (PVC), and compared with traditional plasticiser bis(2-ethylhexyl) phthalate (DOP). When the plasticiser concentration in PVC was below 40wt-%, HBPE showed better plasticisation efficiency than DOP, with enhanced impact strength and ultimate elongation. Volatility and extractability tests for PVC films indicated that there was no migration if HBPE was used as plasticiser, even under very harsh conditions, while the migration in PVC films plasticised by DOP was much greater, indicating that HBPE could be used as a substitution for DOP to lower the potential health risk from migrating phthalates during the use of PVC products.