Acceleration of crystallisation rate in injection moulded PLLA by stereocomplex formation

The physical properties and non-isothermal melt- and cold-crystallisation kinetics of poly (l-lactic acid) (PLLA) and poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) biobased polymers reprocessed by mechanical milling of moulded specimens and followed injection moulding with up to seven recycling cycles are investigated. Non-isothermal crystallisation kinetics are evaluated by the half-time of crystallisation and a procedure based on the mathematical treatment of DSC cumulative crystallisation curves at their inflection point (Kratochvil-Kelnar method). Thermomechanical recycling of PLLA raised structural changes that resulted in an increase in melt flow properties by up to six times, a decrease in the thermal stability by up to 80 °C, a reduction in the melt half-time crystallisation by up to about 40%, an increase in the melt crystallisation start temperature, and an increase in the maximum melt crystallisation rate (up to 2.7 times). Furthermore, reprocessing after the first recycling cycle caused the elimination of cold crystallisation when cooling at a slow rate. These structural changes also lowered the cold crystallisation temperature without impacting the maximum cold crystallisation rate. The structural changes of reprocessed PHBV had no significant effect on the non-isothermal crystallisation kinetics of this material. Additionally, the thermomechanical behaviour of reprocessed PHBV indicates that the technological waste of this biopolymer is suitable for recycling as a reusable additive to the virgin polymer matrix. In the case of reprocessed PLLA, on the other hand, a significant decrease in tensile and flexural strength (by 22% and 46%, respectively) was detected, which reflected changes within the biobased polymer structure. Apart from the elastic modulus, all the other thermomechanical properties of PLLA dropped down with an increasing level of recycling.

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Stereocomplex formation between enantiomeric poly(lactic acid)s. 4. Differential scanning calorimetric studies on precipitates from mixed solutions of poly(D-lactic acid) and poly(L-lactic acid)

Macromolecules ◽

10.1021/ma00020a027 ◽

1991 ◽

Vol 24 (20) ◽

pp. 5657-5662 ◽

Cited By ~ 166

Author(s):

Hideto Tsuji ◽

Suong Hyu Hyon ◽

Yoshito Ikada

Keyword(s):

Lactic Acid ◽

Poly Lactic Acid ◽

Differential Scanning Calorimetric ◽

Mixed Solutions ◽

Stereocomplex Formation ◽

Calorimetric Studies

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Precise Control of Molecular Weight and Stereospecificity in Lewis Pair Polymerization of Semifluorinated Methacrylates: Mechanistic Studies and Stereocomplex Formation

Macromolecules ◽

10.1021/acs.macromol.0c00553 ◽

2020 ◽

Vol 53 (12) ◽

pp. 4659-4669 ◽

Cited By ~ 5

Author(s):

Xing Wang ◽

Miao Hong

Keyword(s):

Molecular Weight ◽

Mechanistic Studies ◽

Precise Control ◽

Stereocomplex Formation

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EFFECTS OF ADMIXTURES ON THE CRYSTALLISATION RATE OF GYPSUM A BATCH CRYSTALLISATION STUDY

REAKTOR ◽

10.14710/reaktor.8.2.85-93 ◽

2017 ◽

Vol 8 (2) ◽

pp. 85

Author(s):

S. Muryanto ◽

H. M. Ang

Keyword(s):

Equilibrium Concentration ◽

Crystallization Rate ◽

Supersaturated Solution ◽

Different Types ◽

Different Temperatures ◽

Copper Zinc ◽

Time Required ◽

Crystallisation Rate ◽

Zinc Concentrate ◽

Concentrate Production

This paper descripbes a study on the effects of admixtures on the crystallization rate of gypsum. Two different types of biodegradable admixtures commonly used as flotation agent in copper/zinc concentrate production, namely, sodium isopropyl xanthate (=SIPX) and isopropyl thionocarbamate were investigated in this study. A laboratory batch crystallizer was used in this study, and the experiments were run using seeded method. The rate of desupersaturation or the time required to reach the equilibrium concentration was compared for varying admixture oncentrations. It was discovered that the added seed crystals started growing imediately upon addition into the supersaturated solution, i.e. there was no induction time.Results of this batch crystallizationstudy suggest that addition of admixtures individually or in combination, significantly affects the crystallization kinetics and in particular, reduces the rate of crystallization of gypsum. Activation energies were determined using three different temperatures, and the values obtained mostly agreed with other published values, i.e. 60.00 ± 3.00, 57.39 ± 2.87, and 37.65 ±1.88 kj/mol, for pure gypsum, isopropyl yhionocarbamate, and SIPX, respectively.Keywords : activation energy; admixtures; CaSO4.2H2O; crystallization, gypsum; reaction rate

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