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Description of the Yield State of Bioplastics on Examples of Starch-Based Plastics and PLA/PBAT Blends

Fras T., Nishida M., Rusinek A., Pęcherski R. B., Fukuda N.

Engineering Transactions

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2014

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Vol. 62, iss. 4

329–-354

EN

The present work concerns the description of the yield state of biodegradable materials. As examples, biodegradable polymers are chosen – cornpole CRP-M2, starch fatty acid ester, and PLA/PBAT, poly(lactic acid) (PLA) blended with poly(butylene adipate/terephthalate) (PBAT) [1, 2]. These biodegradable, plant-derived bioplastics are a promising alternative to petroleum-based plastics. To describe the onset of plasticity in the bioplastics under discussion, Burzyński ’s hypothesis of material effort has been applied [3, 4]. The applied criteria account for the strength differential effect and for the shear correction resulting from the difference between experimental and theoretical values obtained as a result of the Huber-Mises approach [5, 6]. In general, these properties of yield state are characteristic for polymers. The description of yield state for bioplastics is an issue that has hardly been investigated, which illustrates the novel nature of this paper where this topic is discussed.

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Effect of Dialkyl Peroxide Blending on Tensile Properties of PLA/PBAT Polymer Alloys

Nishida M., Ichihara H., Watanabe H., Fukuda N., Ito H.

Engineering Transactions

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2012

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Vol. 60, iss. 2

171-171

EN

Poly(lactic acid) (PLA) and poly(butylene adipate/terephthalate) (PBAT) were used for polymer alloys, and the e?ects of the mixing ratio of PLA and PBAT and the addition of dialkyl peroxide (compatibilizing agent) were examined. The stress-strain curves of PLA/PBAT and PLA/PBAT/dialkyl peroxide specimens were measured using a tensile split Hopkinson bar (Kolsky Bar) method and a universal testing machine. The mixing ratio of PLA and PBAT and the dialkyl peroxide addition a?ected the shape of the stress-strain curve behavior. Regardless of the strain rate, the yield stress decreased and the elongation at break and strain energy increased with increasing PBAT content when the dialkyl peroxide was used. At high strain rate, the dialkyl peroxide addition increased the elongation at break and the strain energy, and changed the fracture surface to a whitened form that was markedly uneven. This result could explain the improvement in the Izod impact strength.

3

Evaluation of dynamic compressive properties of PLA/PBAT polymer alloys using split Hopkinson pressure bar method

Nishida M., Ichihara H., Fukuda N.

Engineering Transactions

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2011

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Vol. 59, iss. 1

23-30

EN

Poly(lactic acid) (PLA) is a biodegradable biomass polymer. Polymer blends or polymer al- loys have been used to overcome its brittleness. Because poly(butylene/adipate/terephthalate) (PBAT) is a ductile and biodegradable polymer, PLA/PBAT polymer alloys can potentially exhibit high impact strengths. Di?erent mixing ratios of PLA/PBAT (80:20, 70:30 and 60:40) and the addition of dialkylperoxide as compatibilizing agent for each mixing ratio have been examined. The stress-strain curves of the PLA/PBAT specimens (observed using a scanning electron microscope) were measured using a split Hopkinson pressure bar (Kolsky bar) and a universal testing machine. The PBAT ratios and addition of dialkylperoxide a?ected the stress-strain curves. Yield stress decreased with increasing PBAT ratios. Addition of dialkylper- oxide did not change the yield stress of specimens when PLA:PBAT = 80:20. At high strain rates, the addition of dialkylperoxide clearly reduced yield stress and Young’s modulus when PLA: PBAT = 70:30 and 60:40.