The crystallization of<scp>PA11</scp>,<scp>PA12</scp>, and their random copolymers at increasing supercooling: From eutectic segregation to mesomorphic solid solutions

Verkinderen, Olivier; Baeten, Dorien; Puyvelde, Peter Van; Goderis, Bart

doi:10.1002/pcr2.10216

Cited by 9 publications

(25 citation statements)

References 46 publications

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“…Most of the high-temperature crystallization rate minima in polymers have been found at the transition between two polymorphic phases. In addition to our work on precision polyethylenes with halogens and long-spaced polyacetals, minima have been found in polyamides, , polyesters, − polyketones, syndiotactic polystyrene, isotactic polypropylenes, , dendron-like giant molecules, and amphiphilic molecular brushes of poly(ethylene oxide) and n -alkyl side chains . Minima that appear in the low-temperature region approaching the glass transition have been interpreted as a change from heterogeneous to homogeneous nucleation. − …”

Section: Introductionmentioning

confidence: 70%

“…Prior rate minima or discontinuities found in the temperature gradient of the crystallization rate of precision polyethylenes and in other semicrystalline polymers have been invariably associated with a polymorphic transition. ,− The minima displayed by PEBs in Figure are of interest because PEB does not undergo any apparent polymorphic transition in the whole range of T c analyzed. Such continuous isomorphic behavior and the characteristics of the rate minima, namely a temperature gradient that becomes positive approaching the melting point of a thinner metastable crystal structure, are equivalent to the minimum of the crystallization rate found in long-chain n -alkanes by Ungar and Keller. − …”

Section: Resultsmentioning

confidence: 99%

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Crystallization Rate Minima of Poly(ethylene brassylate) at Temperatures Transitioning between Quantized Crystal Thicknesses

et al. 2022

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Poly(ethylene tridecanodiate), also known as poly-(ethylene brassylate) (PEB), is a short−long aliphatic polyester obtained from a renewable source. Cooled from the melt by differential scanning calorimetry or by fast scanning calorimetry, PEBs in a range of molar mass between 27000 and 188000 Da display single crystallization exotherms. On heating, PEBs exhibit two major melt-recrystallization events at ∼40 and ∼60 °C prior to their final melting at ∼70 °C. WAXD patterns collected in situ during heating rule out any polymorphic transition, but SAXS patterns collected at the isothermal crystallization temperatures below and above the highest melt-recrystallization event (∼60 °C) indicate a step increase by one repeating unit of the crystal thickness. The overall isothermal crystallization rate displays two minima at the same temperatures where melt-recrystallization was observed on heating. The minima correspond to the transition between 2−3 repeats (T c = 40 °C) and between 3−4 (T c = 60 °C) monomer repeats in the crystal thickness. A minimum also occurs at the same temperature in the isothermal linear growth rates and is accompanied by a minimum in nucleation density. The observed rate minima at the transition between crystals differing by a quantized thickness are equivalent to the behavior of n-alkanes and low-M w PEO fractions and are also explained by the manifestation of self-poisoning. At T c approaching a rate minimum from above, PEB stems with noninteger repeats attach temporarily to the integer lateral growing surface halting productive growth until they detach or expand to complete the layer. Hence, for this type of polyester, it is the length of the stem approaching the growing surface rather than stems with a different conformation that drives self-poisoning.

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Section: Introductionmentioning

confidence: 70%

Section: Resultsmentioning

confidence: 99%

Crystallization Rate Minima of Poly(ethylene brassylate) at Temperatures Transitioning between Quantized Crystal Thicknesses

et al. 2022

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“…47 The T m of the as-received endcapped PA12 is rather low for laterally extended 5 repeating unit thick lamellar but too high to be due to 4 repeating unit thick crystals, of which the predicted T m by Verkinderen et al is 175.6 °C. 46 Therefore, endcapped PA12 seems to contain 5 repeating unit thick crystals with limited lateral dimensions. 46 After melting and cooling at 10 °C/min, the crystals are only 4 repeating units thick, judging from the melting peak temperature in the second heating run, reducing the crystal thickness to 61.5 Å.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

Memory Effects in the Quiescent Crystallization of Polyamide 12: Self-Seeding, Post-Condensation, Disentangling, and Self-Nucleation beyond the Equilibrium Melting Temperature

et al. 2023

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This paper addresses the role of memory effects from earlier thermal protocols on the non-isothermal crystallization behavior of polyamide 12 (PA12). It turns out that memory effects can induce differences in crystallization temperatures as large as 30 °C when cooled from the melt at 10 °C/min. DSC experiments reveal that memory effects in PA12 result from (1) self-nucleation by the action of crystalline residues (self-seeding), (2) chemical post-condensation, and (3) polymer chain disentangling and re-entangling. Self-nucleation and disentangling facilitate crystallization, while melt post-condensation and re-entangling hamper it. It was demonstrated that repeated crystallization stimulates disentangling and that re-entangling in the liquid state proceeds more rapidly the higher the temperature. Effects due to solid-state post-condensation are very intriguing and particularly relevant to laser sintering based additive manufacturing. It was observed that solid-state post-condensation at 175 °C for 1 h negatively affects crystallization in a subsequent heating/cooling cycle but that solid-state annealing at 175 °C for 20 h leads to an enhanced crystal perfection and chain rearrangements whose non-crystalline self-nucleating remnants in the melt at 240 °C need more than 1 h to relax and no longer stimulate crystallization during cooling. Importantly, 240 °C is higher than the equilibrium melting temperature of PA12.

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“…Based on the advanced thermal analysis system (ATHAS) databank and literatures, the T 0 m for PA12 is recommended to be 267 C (500 K). 33,34 Based on Equation (3), the f local exhibits two local minima as a function of ψ, which are observed in Figure 2. It is observed that the trend of the free local energy density differs with temperature.…”

Section: Mathematical Modelmentioning

confidence: 99%

“…Hence, with polyamides experiencing lamellar thinning during crystallization, 32 the Hoffman‐Weeks relation is not suitable for determining the equilibrium melting temperature for PA12. Based on the advanced thermal analysis system (ATHAS) databank and literatures, the

T_{m}^{0}

for PA12 is recommended to be 267°C (500 K) 33,34 …”

Section: Mathematical Modelmentioning

confidence: 99%

Investigation of polyamide 12 isothermal crystallization through the application of the phase‐field model

Teo

Tran

Chen

et al. 2022

Polymers for Advanced Techs

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Crystallization of polyamide 12 (PA12) is an essential process requiring thorough investigation for evaluating the mechanical properties after the polymer parts are manufactured. The change in crystallization temperature results in different crystallization behaviors for PA12. Hence, the crystal morphology of PA12 achieved provides important information about crystallization behavior, especially for those produced through additive manufacturing due to its heterogenous cooling rate in a single print bed. Considering the need of investigating PA12 crystallization using phase‐field modeling, this paper aims to simulate the spherulite morphology of PA12 undergoing isothermal crystallization. This model is compared with the spherulite morphologies obtained from the optical microscopy test. The model shows that PA12 spherulites have thicker dendrites when the isothermal temperature is higher. The present phase‐field model can determine the spherulite morphologies of bulk printed PA12 based on the crystallization condition and be used to evaluate the properties of the printed part.

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The crystallization ofPA11,PA12, and their random copolymers at increasing supercooling: From eutectic segregation to mesomorphic solid solutions

Cited by 9 publications

References 46 publications

Crystallization Rate Minima of Poly(ethylene brassylate) at Temperatures Transitioning between Quantized Crystal Thicknesses

Crystallization Rate Minima of Poly(ethylene brassylate) at Temperatures Transitioning between Quantized Crystal Thicknesses

Memory Effects in the Quiescent Crystallization of Polyamide 12: Self-Seeding, Post-Condensation, Disentangling, and Self-Nucleation beyond the Equilibrium Melting Temperature

Investigation of polyamide 12 isothermal crystallization through the application of the phase‐field model

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