Structure–Property–Processing Relations of Short‐Chain Branched Poly(butylene terephthalate) (PBT) with Biobased Comonomers

Poly(butylene terephthalate) (PBT) is difficult to foam due its unfavorable rheological behavior (low melt strength, no strain hardening). In particular, a high expansion and homogeneous cell morphology are achieve. This can be altered successfully by addition of multifunctional chain extenders. Chain extenders cause nondefined rarely understood changes in the polymer architecture usually described as branching. this contribution, synthesis two series PBT copolyesters with defined short-chain branched units presented. Dilinoleic derivatives linear C9 C7 alkyl side chains employed reflect branches incorporated into various molar ratios. Characterization NMR spectroscopy size exclusion chromatography demonstrates random structure masses terpolyesters. Incorporation dilinoleic results reduction crystallinity, decreased glass transition temperatures, behavior, particular extensional rheology characterized hardening. The comparison control without proves that hardening caused branches. A higher concentration induces stronger hardening, resulting successful foaming. It demonstrated new terpolyesters have properties comparable treated