Two crystal populations with different melting/reorganization kinetics of isothermally crystallized polyamide 6

Abstract

Differential scanning calorimetry and fast scanning chip calorimetry heating experiments were carried out in a wide range of rates of temperature change from 0.2 to 60,000 K s−1 for isothermally crystallized polyamide 6. Multiple melting peaks were observed. With increasing heating rate, the highest‐temperature endotherm shifts toward lower temperatures and finally disappears due to suppression of the reorganization. The critical heating rate to suppress reorganization was 15–50 times higher than the critical cooling rate to cause complete vitrification. On heating at rates higher than the critical heating rate to suppress reorganization, there were observed two melting processes of different kinetics. Four possible assignments were considered regarding the two crystal populations. These are (i) crystals grown during primary and secondary crystallization, (ii) crystals grown in the bulk and nucleated at the surface/substrate, (iii) crystals, which are subjected to different local stress originating from heterogeneities in interlamellar regions, and (iv) the crystal/mesophase polymorphism. © 2016 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2016, 54, 2126–2138

Crystallization/Melting Kinetics and Morphological Analysis of Polyphenylene Sulfide

“…Fast scanning calorimetry (FSC) is a powerful method to overcome this limitation and to investigate melting and crystallization kinetics in a wide temperature range without unwanted crystallization during temperature scanning . Researchers have also succeeded in analyzing melting and/or crystallization kinetics of polyethylene (PE), polyamide 6 (PA6), poly(ether ether ketone) (PEEK), poly(butylene terephthalate) (PBT), and poly(trimethylene terephthalate) (PTT) . Regarding PPS, the crystallization behavior was reported using DSC and small‐angle X‐ray scattering (SAXS) .…”

Crystallization kinetics of poly(butylene terephthalate) and its talc composites

“…(11) and (12), the cooling rate dependence of total enthalpy change in Figure 8 is fitted by the following function: Then, taking into account, eqs.…”

“…4 Nevertheless, the temperature range for direct isothermal crystallization studies using conventional calorimeters is, for most polymers, limited to regions close to the melting temperature, where crystallization is reasonably slow. 9 FSC has in the past been proven successful to achieve the goal for polyamide (PA), 11 poly ether ether ketone (PEEK), 12 polyethylene (PE), [13][14][15] poly (ethylene terephthalate) (PET), 16,17 isotactic polypropylene (iPP), [18][19][20][21] isotactic polystyrene (iPS), 22 poly L-lactic acid (PLLA), 23 PBT, [24][25][26][27] or poly (E2caprolactone) (PCL), [28][29][30][31] to name a few. Fast scanning calorimetry (FSC) is a powerful method to overcome this limitation and to investigate nucleation and crystal growth kinetics without unwanted crystallization during cooling.…”

Comparing Crystallization Kinetics between Polyamide 6 and Polyketone via Chip‐Calorimeter Measurement

“…Marand and co‐workers have reported that the lowest‐temperature peak was the melting of crystals formed during secondary crystallization, the middle‐temperature peak was the melting of primary crystallization, whereas the highest‐temperature peak was the melting of reorganized crystals . There exist other explanations for the low‐temperature melting peaks . Anyway, the heating curves shown in Figure reveal that the heating faster than 2000 K s −1 can effectively suppress the highest melting peak caused by the reorganization of PA crystals.…”