scholarly journals Fast-Scanning Chip-Calorimetry Measurement of Crystallization Kinetics of Poly(Glycolic Acid)

Polymers ◽  
2021 ◽  
Vol 13 (6) ◽  
pp. 891
Author(s):  
Yongxuan Chen ◽  
Kefeng Xie ◽  
Yucheng He ◽  
Wenbing Hu
Keyword(s):  
Crystallization Kinetics ◽  
Temperature Region ◽  
Glycolic Acid ◽  
Crystal Nucleation ◽  
Side Group ◽  
Half Time ◽  
Temperature Range ◽  
Chip Calorimetry ◽  
Kinetics Of ◽  
Fast Scanning Chip Calorimetry

We report fast-scanning chip-calorimetry measurement of isothermal crystallization kinetics of poly(glycolic acid) (PGA) in a broad temperature range. We observed that PGA crystallization could be suppressed by cooling rates beyond -100 K s−1 and, after fast cooling, by heating rates beyond 50 K s-1. In addition, the parabolic curve of crystallization half-time versus crystallization temperature shows that PGA crystallizes the fastest at 130 °C with the minimum crystallization half-time of 4.28 s. We compared our results to those of poly(L-lactic acid) (PLLA) with nearby molecular weights previously reported by Androsch et al. We found that PGA crystallizes generally more quickly than PLLA. In comparison to PLLA, PGA has a much smaller hydrogen side group than the methyl side group in PLLA; therefore, crystal nucleation is favored by the higher molecular mobility of PGA in the low temperature region as well as by the denser molecular packing of PGA in the high temperature region, and the two factors together decide the higher crystallization rates of PGA in the whole temperature range.

scholarly journals New Insights into Crystallization of Heterophasic Isotactic Polypropylene by Fast Scanning Chip Calorimetry

Polymers ◽  
2020 ◽  
Vol 12 (8) ◽  
pp. 1683
Author(s):  
Daniela Mileva ◽  
Jingbo Wang ◽  
Markus Gahleitner ◽  
Katalee Jariyavidyanont ◽  
René Androsch
Keyword(s):  
Crystallization Kinetics ◽  
Isotactic Polypropylene ◽  
Crystallization Rate ◽  
Crystal Nucleation ◽  
Crystallization Time ◽  
Chip Calorimetry ◽  
The Matrix ◽  
Homogeneous Crystal ◽  
Kinetics Of ◽  
Fast Scanning Chip Calorimetry

The crystallization kinetics of metallocene-catalyzed heterophasic isotactic polypropylene composed of a matrix of isotactic polypropylene (iPP) and rubbery particles made of random ethylene–propylene copolymers (EPC), often denoted as heterophasic iPP copolymers, was analyzed as a function of the cooling rate and supercooling in nonisothermal and isothermal crystallization experiments, respectively. Fast scanning chip calorimetry (FSC) allowed assessing crystallization at processing-relevant conditions, and variation of the content (0–39 wt %) and composition (0–35 wt % propylene counits) of the EPC particles revealed qualitatively new insight about mechanisms of heterogeneous crystal nucleation. For neat iPP homopolymer, the characteristic bimodal temperature dependence of the crystallization rate due to predominance of heterogeneous and homogeneous crystal nucleation at high and low temperatures, respectively, is reconfirmed. At high temperatures, in heterophasic iPP, the here studied ethylene-(C2)-rich EPC particles accelerate crystallization of the iPP-matrix, with the acceleration or nucleation efficacy correlating with the EPC-particle content. The crystallization time reduces by more than half in presence of 39 wt % EPC particles. An additional nucleating effect of the EPC particles on iPP-matrix crystallization is detected after their crystallization, suggesting that liquid/rubbery particles are less effective than solid/semicrystalline particles in affecting crystallization of the surrounding iPP-matrix. At low temperature, homogeneous crystal nucleation in the iPP-matrix outpaces all heterogeneous nucleation effects, and the matrix-crystallization rate is independent of the sample composition. The obtained results lead to the conclusion that the crystallization kinetics of iPP can be affected significantly by the content and composition of EPC particles, even towards superfast crystallizing iPP grades.

Steady-State Crystal Nucleation Rate of Polyamide 66 by Combining Atomic Force Microscopy and Fast-Scanning Chip Calorimetry

2020 ◽  
Vol 53 (13) ◽  
pp. 5560-5571 ◽  
Author(s):  
Rui Zhang ◽  
Evgeny Zhuravlev ◽  
Jürn W. P. Schmelzer ◽  
René Androsch ◽  
Christoph Schick
Keyword(s):  
Atomic Force Microscopy ◽  
Steady State ◽  
Nucleation Rate ◽  
Crystal Nucleation ◽  
Polyamide 66 ◽  
Force Microscopy ◽  
Atomic Force ◽  
Chip Calorimetry ◽  
Fast Scanning Chip Calorimetry

Kinetics of the reaction H + C2H6 → H2 + C2H5 in the temperature region of 1000 K

1984 ◽  
Vol 62 (1) ◽  
pp. 86-91 ◽  
Author(s):  
J.-R. Cao ◽  
M. H. Back
Keyword(s):  
Equilibrium Constant ◽  
Rate Constant ◽  
Temperature Region ◽  
Recent Measurement ◽  
Hydrogen Atoms ◽  
Elementary Reactions ◽  
Temperature Range ◽  
Hydrogen Molecules ◽  
Kinetics Of ◽  
Rate Controlling Step

A system for the measurement of rate constants for elementary reactions of hydrogen atoms in the temperature region of 1000 K is described. The concentration of hydrogen atoms is controlled by the equilibrium constant for dissociation of hydrogen molecules. The kinetics of the rate of conversion of ethane to ethylene in this system has been studied over the temperature range 876–1016 K. The results show that the rate-controlling step is[Formula: see text]and the value obtained for the rate constant is[Formula: see text](R = 1.987 cal mol−1 deg−1). This value is compared with values obtained from other methods over the temperature range 300–1400 K. Combination with a recent measurement of the rate constant for the reverse reaction yields an experimental value for the equilibrium constant for the reaction.

scholarly journals Surface Crystal Nucleation and Growth in Poly (ε-caprolactone): Atomic Force Microscopy Combined with Fast Scanning Chip Calorimetry

Polymers ◽  
2021 ◽  
Vol 13 (12) ◽  
pp. 2008
Author(s):  
Rui Zhang ◽  
Mengxue Du ◽  
Evgeny Zhuravlev ◽  
René Androsch ◽  
Christoph Schick
Keyword(s):  
Radial Symmetry ◽  
Crystal Nucleation ◽  
Melt Crystallization ◽  
Equilibrium Melting Temperature ◽  
Force Microscopy ◽  
Bulk Crystallization ◽  
Atomic Force ◽  
Chip Calorimetry ◽  
Surface Crystal ◽  
Fast Scanning Chip Calorimetry

By using an atomic force microscope (AFM) coupled to a fast scanning chip calorimeter (FSC), AFM-tip induced crystal nucleation/crystallization in poly (ε-caprolactone) (PCL) has been studied at low melt-supercooling, that is, at a temperature typically not assessable for melt-crystallization studies. Nanogram-sized PCL was placed on the active/heatable area of the FSC chip, melted, and then rapidly cooled to 330 K, which is 13 K below the equilibrium melting temperature. Subsequent isothermal crystallization at this temperature was initiated by a soft-tapping AFM-tip nucleation event. Crystallization starting at such surface nucleus led to formation of a single spherulite within the FSC sample, as concluded from the radial symmetry of the observed morphology. The observed growth rate in the sub-micron thin FSC sample, nucleated at its surface, was found being much higher than in the case of bulk crystallization, emphasizing a different growth mechanism. Moreover, distinct banding/ring-like structures are observed, with the band period being less than 1 µm. After crystallization, the sample was melted for gaining information about the achieved crystallinity and the temperature range of melting, both being similar compared to much slower bulk crystallization at the same temperature but for a much longer time.

scholarly journals Pressure- and Temperature-Dependent Crystallization Kinetics of Isotactic Polypropylene under Process Relevant Conditions

Crystals ◽  
2021 ◽  
Vol 11 (9) ◽  
pp. 1138
Author(s):  
Yvonne Spoerer ◽  
Regine Boldt ◽  
René Androsch ◽  
Ines Kuehnert
Keyword(s):  
Injection Molding ◽  
Cooling Rate ◽  
Crystallization Kinetics ◽  
Crystallization Temperature ◽  
Random Copolymer ◽  
Shift Factor ◽  
Temperature Dependent ◽  
Chip Calorimetry ◽  
The Relationship ◽  
Kinetics Of

In this study, a non-nucleated homopolymer (HP) and random copolymer (RACO), as well as a nucleated HP and heterophasic copolymer (HECO) were investigated regarding their crystallization kinetics. Using pvT-measurements and fast scanning chip calorimetry (FSC), the crystallization behavior was analyzed as a function of pressure, cooling rate and temperature. It is shown that pressure and cooling rate have an opposite influence on the crystallization temperature of the materials. Furthermore, the addition of nucleating agents to the material has a significant effect on the maximum cooling rate at which the formation of α-crystals is still possible. The non-nucleated HP and RACO materials show significant differences that can be related to the sterically hindering effect of the comonomer units of RACO on crystallization, while the nucleated materials HP and HECO show similar crystallization kinetics despite their different structures. The pressure-dependent shift factor of the crystallization temperature is independent of the material. The results contribute to the description of the relationship between the crystallization kinetics of the material and the process parameters influencing the injection-molding induced morphology. This is required to realize process control in injection molding in order to produce pre-defined morphologies and to design material properties.

Orientation Induced Nucleation in Polymer Crystallization

1967 ◽  
Vol 40 (3) ◽  
pp. 786-787
Author(s):  
F. L. Binsbergen
Keyword(s):  
Crystallization Kinetics ◽  
Polymer Crystallization ◽  
Morphological Description ◽  
Half Time ◽  
Suitable Temperature ◽  
History Of ◽  
Kinetics Of

Abstract Crystallization kinetics of polymers crystallizing from the melt are influenced by the mechanical history of the sample. Strain free samples show a larger crystallization half time than samples in which the strain has not been completely removed by relaxation at a suitable temperature. A larger number of nuclei has been assumed to be present in strained samples than in strain free ones. This has been called “orientation induced” or “stress induced” nucleation. This communication presents a morphological description of the phenomenon and of the underlying type of nucleation. My observations were made with a microscope (Reichert ‘Zetopan-Pol’) equipped with a hot stage and 24-mm camera, and mainly with the polarizers crossed. For most of my experiments I used polypropylene, but similar phenomena were also observed with several other polymers.

Synthesis and Crystallization Kinetics of Y 2CaA1 4SiO 12 Garnet-Type Glass-Ceramic

2020 ◽  
Author(s):  
Liyuan Wang ◽  
Jiaxi Liu ◽  
Nan Lu ◽  
Zengchao Yang ◽  
Gang He ◽  
...  
Keyword(s):  
Crystallization Kinetics ◽  
Glass Ceramic ◽  
Kinetics Of

Reordering and Crystallization of Silicon Carbide Amorphized by Neutron Irradiation

2000 ◽  
Vol 650 ◽  
Author(s):  
Lance L. Snead ◽  
Martin Balden
Keyword(s):  
Thin Film ◽  
Silicon Carbide ◽  
Crystallization Kinetics ◽  
Neutron Irradiation ◽  
Onset Temperature ◽  
Kinetics Of Crystallization ◽  
Crystallization Onset Temperature ◽  
Crystallization Onset ◽  
Kinetics Of

ABSTRACTDensification and crystallization kinetics of bulk SiC amorphized by neutron irradiation is studied. The temperature of crystallization onset of this highly pure, fully amorphous bulk SiC was found to be between 875-885°C and crystallization is nearly complete by 950°C. In-situ TEM imaging confirms the onset of crystallization, though thin-film effects apparently alter the kinetics of crystallization above this temperature. It requires >1125°C for complete crystallization of the TEM foil. Annealing at temperatures between the irradiation and crystallization onset temperature is seen to cause significant densification attributed to a relaxation, or reordering, of the as-amorphized structure.

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