Effect of D‐lactide content of annealed poly(lactic acid) on its thermal, mechanical, heat deflection temperature, and creep properties

Tábi, Tamás; Wacha, András; Hajba, Sándor

doi:10.1002/app.47103

Cited by 18 publications

(21 citation statements)

References 44 publications

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“…Also a small exothermic peak was visible just prior to melting, representing the solid-phase recrystallization of the less ordered a 0 crystal form into the more ordered a form [26]. This suggests that the crystal structure of the PLLA developed during annealing consists mainly of the less ordered a 0 crystal form, since it is difficult to develop the more ordered a crystal form in low D-lactide PLA grades (like PLLA) due to its lower T cc compared to higher D-lactide PLA grades [41]. Moreover, although by applying annealing temperatures above 100°C, the more ordered a could also develop [42], but due to the nucleating effect of EVA on PLA, the cold crystallization temperatures shifted to even lower temperatures as it was discussed previously (Fig.…”

Section: Resultsmentioning

confidence: 99%

The application of the synergistic effect between the crystal structure of poly(lactic acid) (PLA) and the presence of ethylene vinyl acetate copolymer (EVA) to produce highly ductile PLA/EVA blends

Tábi

2019

J Therm Anal Calorim

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In this paper, we produced ethylene vinyl acetate copolymer (EVA)-filled poly(lactic acid) (PLA) blends by extrusion and injection moulding. We annealed the injection-moulded specimens at 80°C, 100°C, 120°C and 140°C to produce various crystal structures in PLA. Then we investigated the cross-effect between the crystal structure of PLA and the presence of EVA on the mechanical, impact, calorimetric, thermomechanical and heat deflection temperature properties of the blends. We found a synergistic toughening effect between the crystal structure of PLA that developed during annealing and the presence of dispersed EVA particles in the PLA matrix. The blend had a very high impact strength of over 65 kJ m-2 , which is three times higher than the impact strength of acrylonitrile butadiene styrene copolymer (* 20 kJ m-2), and thus it is very promising for technical applications.

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Section: Resultsmentioning

confidence: 99%

The application of the synergistic effect between the crystal structure of poly(lactic acid) (PLA) and the presence of ethylene vinyl acetate copolymer (EVA) to produce highly ductile PLA/EVA blends

Tábi

2019

J Therm Anal Calorim

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“…For extrusion foaming of PLA with a physical blowing agent, density reduction can be made most successfully with CO 2 [15]. The resulting density range is lower than 0.1 g/cm 3 , although for this, both the PLA raw material (e.g., with a chain-extender [16], a nucleating agent [17], or by post-production heat-treatment [18]) and the processing equipment need to be modified [19].…”

Section: Introductionmentioning

confidence: 99%

Development of Poly (Lactide Acid) Foams with Thermally Expandable Microspheres

Kmetty

Litauszki

2020

Polymers

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This study presents the investigation of different content of thermally expandable microsphere (EMS) type of a physical blowing agent added to polylactic acid (PLA). The effects of the different doses of EMS, processing temperatures, and d-lactide content of the polylactic acid were analyzed for foam properties and structures. We characterized the different PLAs and the physical blowing agent with different testing methods (gel permeation chromatography, rotational rheometry, isothermal thermogravimetric analysis, and thermomechanical analysis). The amounts of the foaming agent were 0.5, 1, 2, 4, 8 wt%, and processing temperatures were 190 °C, 210 °C, and 230 °C. The foam structures were produced by twin-screw extrusion. We used scanning electron microscopy to examine the cell structure of the foams produced, and carried out morphological and mechanical tests as well. The result of extrusion foaming of PLA using different amounts of EMS shows that an exponentially decreasing tendency of density reduction can be achieved, described by the following equation, ρ(x ) = 1.062 · e − x 7.038 + 0.03 (R2 = 0.947) at 190 °C. With increasing processing temperature, density decreases at a lower rate, due to the effect that the microspheres are unable to hold the pentane gas within the polymer shell structure. The d-lactide content of the PLAs does not have a significant effect on the density of the produced foam structures.

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“…Its glass transition temperature is around 50-55°C depending on D-Lactide content and molecular weight. It has a slow crystallization rate because of its low crystallinity, which is the reason for its low HDT [2][3][4][5].…”

Section: Introductionmentioning

confidence: 99%

“…Fig 5. The product stuck into the mold and the critical locations in the mold cavity where this phenomenon is initiated…”

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confidence: 99%

The Effect of Processing Parameters and Calcium-stearate on the Ejection Process of Injection Molded Poly(Lactic Acid) Products

Tábi

Pölöskei

2021

Period. Polytech. Mech. Eng.

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We investigated the ejection/demolding of continuous production of injection molded Poly(Lactic Acid) tensile testing specimens and analyzed the effect of 1 wt% Calcium-Stearate additive as demolding agent (sliding or mold release agent) on this process. We demonstrated that the Poly(Lactic Acid) specimens could get stuck in the mold or even break during demolding during continuous injection molding in a certain type of mold, which has a low draft angle and varying cavity width along the flow path. The standard dumbbell-shaped tensile testing specimen is produced in such a mold. Demolding was rated with the use of a high-speed camera into three categories (problem-free demolding / stuck, but demolded undamaged product / stuck and damaged product). Moreover, the ejector force required to push the product out of the cavity was monitored over 30 continuous injection molding cycles. We also investigated the effect of processing parameters, such as injection rate (screw speed), holding pressure, holding time, mold temperature, melt temperature, backpressure, screw rotational speed, and pre-process drying (drying or not drying the pellets before injection molding). We managed to avoid product breakage during demolding with the proper settings of certain process parameters and the use of Calcium-Stearate, an effective demolding agent. This ensured problem-free demolding and thus continuous injection molding.

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Effect of D‐lactide content of annealed poly(lactic acid) on its thermal, mechanical, heat deflection temperature, and creep properties

Cited by 18 publications

References 44 publications

The application of the synergistic effect between the crystal structure of poly(lactic acid) (PLA) and the presence of ethylene vinyl acetate copolymer (EVA) to produce highly ductile PLA/EVA blends

The application of the synergistic effect between the crystal structure of poly(lactic acid) (PLA) and the presence of ethylene vinyl acetate copolymer (EVA) to produce highly ductile PLA/EVA blends

Development of Poly (Lactide Acid) Foams with Thermally Expandable Microspheres

The Effect of Processing Parameters and Calcium-stearate on the Ejection Process of Injection Molded Poly(Lactic Acid) Products

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