The Relationship among Branching Factor, Rheological Properties and Processability of Branched Poly(butylene succinate-co-butylene adipate)
Mitsuhiro Imaizumi, Yoshiro Okino, Masaoki Takahashi, Katsuyuki Yoshikawa
Venture Business Laboratory, Yamagata University
JAPAN

Keywords: Biodegradable plastics , Direct extrusion gas foaming , Long chain branching (LCB)

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Aliphatic polyesters as biodegradable plastics have been studied and their commercial applications are growing progressively. Processability to be applied to conventional forming methods must be an important factor to extend the applicability of biodegradable plastics. It has been known that long chain branching contributes excellent processability of polyethylene. For aliphatic polyesters the introduction of long chain branching is expected to improve their processability.
In this study the molecular structure, viscoelastic properties of melts and processability for direct extrusion gas foaming method were investigated for branched poly (butylene succinate-co- butylene adipate) (PBSA-B) which was copolymerized with a little of multifunctional monomer.
It was found that the introduction of long chain branching improved melt tension of PBSA-B samples. Furthermore they had long relaxation time component in the dynamic viscoelasticity and showed strain hardening in the elongational viscosity measurement, in comparison with linear PBSA.
We were able to obtain biodegradable foamed sheet products having densities of 60 kg/m3 and thicknesses from 1.0 to 3.0mm, while the PBSA-L did not show such good processabilities. In addition, this foamed sheet was stable in the atmosphere for 2 years, but biodegradable in hot compost under aerobic conditions where a large number of microorganisms were present. The biodegradation rate of PBSA-B foamed sheet and PBS-B foamed sheet in hot compost (at 45C) was measured. The percent biodegradation of PBSA-B and PBS-B foamed sheet after 14days was 90wt% and 25wt%, respectively.