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

Research output: Contribution to journalResearch articleContributedpeer-review


  • Christian Mielke - , Leibniz Institute of Polymer Research Dresden, TUD Dresden University of Technology (Author)
  • Justus Kuhnigk - , University of Bayreuth (Author)
  • Doris Pospiech - , Leibniz Institute of Polymer Research Dresden (Author)
  • Hartmut Komber - , Leibniz Institute of Polymer Research Dresden (Author)
  • Regine Boldt - , Leibniz Institute of Polymer Research Dresden (Author)
  • Albena Lederer - , Leibniz Institute of Polymer Research Dresden, University of Stellenbosch (Author)
  • Miroslawa El Fray - , West Pomeranian University of Technology (Author)
  • Tobias Standau - , University of Bayreuth (Author)
  • Holger Ruckdaeschel - , University of Bayreuth (Author)
  • Volker Altstaedt - , University of Bayreuth (Author)
  • Brigitte Voit - , Chair of Organic Chemistry of Polymers, Leibniz Institute of Polymer Research Dresden, TUD Dresden University of Technology (Author)


Poly(butylene terephthalate) (PBT) is difficult to foam due to its unfavorable rheological behavior (low melt strength, no strain hardening). In particular, a high expansion and a homogeneous cell morphology are difficult to achieve. This can be altered successfully by addition of multifunctional chain extenders. Chain extenders cause nondefined and rarely understood changes in the polymer architecture usually described as branching. In this contribution, the synthesis of two series of PBT copolyesters with defined short-chain branched units is presented. Dilinoleic derivatives with linear C-9 and C-7 alkyl side chains are employed to reflect short-chain branches and are incorporated into PBT in various molar ratios. Characterization by NMR spectroscopy and size exclusion chromatography demonstrates the random chain structure and high molar masses of the terpolyesters. Incorporation of dilinoleic derivatives results in the reduction of PBT crystallinity, decreased glass transition temperatures, and altered rheological behavior, in particular of extensional rheology characterized by strain hardening. The comparison to control copolyesters without branches proves that strain hardening is caused by the branches. A higher concentration of branches induces stronger strain hardening, resulting in successful foaming. It is demonstrated that the new terpolyesters have properties comparable with PBT treated with chain extenders.


Original languageEnglish
Article number2200208
Number of pages15
JournalMacromolecular materials and engineering
Issue number9
Early online dateJun 2022
Publication statusPublished - Sept 2022

External IDs

Scopus 85131593144
ORCID /0000-0002-4531-691X/work/148608030



  • Batch foaming, Branching, Fatty acid, Poly(butylene terephthalate), Rheology, Structure-property relationships