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.

scholarly journals Crystallization Kinetics Of Coconut Oil Based On Gompertz Model

2018 ◽  
Vol 1 (1) ◽  
pp. 1-7
Author(s):  
Mursalin Mursalin
Keyword(s):  
Cooling Rate ◽  
Crystallization Kinetics ◽  
Crystallization Temperature ◽  
Induction Time ◽  
Coconut Oil ◽  
Gompertz Model ◽  
Maximum Increase ◽  
Critical Cooling Rate ◽  
Increase Rate ◽  
Kinetics Of

The cooling rate and temperature of crystallization has been proven to be very influential on the rate of crystal formation oil. Oil crystallization kinetics can be measured by monitoring changes in the solid fat content(SFC) of oil during cooling process.  In this study, SFC measuredusing pulsed Nuclear Magnetic Resonance (pNMR). Four levels of cooling rates and temperature crystallization studied. Crystallization kinetics parameters were measured by applying the model of Gompertz. Gompertz model used to explain the induction time, the increase in the maximum rate of crystallization and the crystalline polymorphic. Crystallization was done by heating the oil at a temperature of 70°C for 10 minutes prior to rapid cooling to 29°C. Then, rate of cooling from 29°C to the crystallization temperature (critical cooling rate) was set below 2°C/minutes. During the process, the oil was stirred at 15 rpm. Solid fraction was measured periodically since the crystallization temperature was reached until maximum solid fraction was achieved.  The results showed that the Gompertzmodel able to quantitatively describe the crystallization kinetics of coconut oil. Lower critical cooling rate reduces the induction time of crystallization but accelerate the maximum increase rate of crystallization. Crystallization temperature has a negative correlation with the induction time and the maximum increase rate of crystallization. In the crystallization of coconut oil, critical cooling rate and crystallization temperature are only influence on the thermodynamics and kinetics of crystallization but not on its polymorphic formation.

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.

Non-Isothermal Crystallization Kinetics of Graphene Oxide-Carbon Nanotubes Hybrids / Polyamide 6 Composites

2019 ◽  
Vol 41 (3) ◽  
pp. 394-394
Author(s):  
Zhi Qiang Wang Zhi Qiang Wang ◽  
Yong Ke Zhao and Xiang Feng Wu Yong Ke Zhao and Xiang Feng Wu
Keyword(s):  
Carbon Nanotubes ◽  
Graphene Oxide ◽  
Cooling Rate ◽  
Crystallization Kinetics ◽  
Isothermal Crystallization ◽  
Crystallization Rate ◽  
Polyamide 6 ◽  
Degree Of Crystallinity ◽  
Isothermal Crystallization Kinetics ◽  
Kinetics Of

The hybrids combined by nano-materials with different dimensions usually possess much better enhancement effects than single one. Graphene oxide-carbon nanotubes hybrids / polyamide 6 composites has been fabricated. The non-isothermal crystallization kinetics of the as-prepared samples was discussed. Research results showed that increasing the cooling rate was in favor of increasing the crystallization rate and the degree of crystallinity for the as-prepared samples. Moreover, the crystallization rate was first decreased and then increased with increasing the hybrids loading. Furthermore, the crystallization mechanism was changed with increasing the crystallization temperature and the cooling rate. The nucleation and growth modes of the non-isothermal crystallization could be classified into three different types, according to the Ozawa’s theory. These complicated results could be attributed to the important role of crystallization rate as well as the simultaneous hindering and promoting effects of the as-prepared hybrids. This work has reference values for understanding the crystallization kinetics of the polyamide 6-based composites.

Morphology, Crystalline Structure and Isothermal Crystallization Kinetics of Polybutylene Terephthalate/Montmorillonite Nanocomposites

2005 ◽  
Vol 13 (1) ◽  
pp. 61-71 ◽  
Author(s):  
Defeng Wu ◽  
Chixing Zhou ◽  
Xie Fan ◽  
Dalian Mao ◽  
Zhang Bian
Keyword(s):  
Activation Energy ◽  
Crystallization Kinetics ◽  
Crystallization Temperature ◽  
Isothermal Crystallization ◽  
Polymer Chains ◽  
Isothermal Crystallization Kinetics ◽  
Clay Particles ◽  
Nucleation Sites ◽  
Kinetics Of ◽  
Montmorillonite Nanocomposites

The melt intercalation method was employed to prepare poly(butylene terepathalate)/montmorillonite nanocomposites, and their microstructure was characterized by wide angle X-ray diffraction and transmission electron microscopy. The XRD results showed that the crystalline plane such as (010), (111), (100) was smaller than that of pristine PBT, which indicates that the crystallite size of PBT in the nanocomposites could be diminished by adding clay. Moreover, the isothermal crystallization kinetics of PBT and PBT/MMT nanocomposites was investigated by differential scanning calorimetry (DSC). During isothermal crystallization, the development of crystallinity with time was analysed by the Avrami equation. The results show that very small amounts of clay dramatically increased the rate of crystallization and high clay concentrations reduced the rate of crystallization at the low crystallization temperatures. At low concentrations of clay, the distance between dispersed platelets was large so it was relatively easy for the additional nucleation sites to incorporate surrounding polymer, and the crystal nucleus was formatted easily. However, at high concentrations of clay, the diffusion of polymer chains to the growing crystallites was hindered by large clay particles, despite the formation of additional nucleation sites by the clay layers. At the higher crystallization temperature, the crystallization of the nanocomposites was slower than that of the pure PBT under the experimental conditions, which means that with the increase in chains mobility at the high crystallization temperature, the crystal nuclei are harder to format, and the hindering effect of clay particles on the polymer chains was stronger than the nucleating effect of the layers. In addition, the activation energies of crystallization for PBT and its nanocomposites were calculated by the Arrhenius relationship, and the results showed that the nanocomposites with a low clay content had the lower activation energy values than PBT, while high amounts of clay increased the activation energy of PBT.

Optimization of melting conditions for the analysis of crystallization kinetics of poly(3-hydroxybutyrate)

e-Polymers ◽  
2009 ◽  
Vol 9 (1) ◽  
Author(s):  
Maria Laura Di Lorenzo ◽  
Pawel Sajkiewicz ◽  
Arkadiusz Gradys ◽  
Paola La Pietra
Keyword(s):  
Melting Point ◽  
Polymer Chain ◽  
Crystallization Kinetics ◽  
Crystallization Temperature ◽  
Degree Of Crystallinity ◽  
Thermal Treatments ◽  
Constant Rate ◽  
Kinetics Of ◽  
Final Degree ◽  
Melting Conditions

AbstractStudies of kinetics of polymer crystallization are generally performed by heating the material above the melting point, in order to erase previous thermal and mechanical history, followed by rapid cooling to the desired crystallization temperature or by cooling at a constant rate. For poly(3-hydroxybutyrate) this procedure implies some degradation of the polymer chain, which starts below the onset of melting. In this article the effects of melting conditions on the subsequent crystallization kinetics are discussed. It is shown that in order to sufficiently cancel memories of previous crystalline order of the analyzed PHB, it is necessary to bring the material at a temperature higher than 192 °C. Thermal treatments conducted at lower temperatures are not sufficient to destroy all solid aggregates, and crystallization of PHB has an anticipated onset of crystallization due to nucleation occurring via self-seeding. The chain degradation attained upon exposure at high temperatures has much lesser influence on crystallization kinetics than incomplete melting, with some effects detectable on the spherulitic morphology and on the final degree of crystallinity.

Study on Crystallization Kinetics of Gypsum Prepared by Bittern under 30oC and Different Stirring Speed

2014 ◽  
Vol 962-965 ◽  
pp. 731-735
Author(s):  
Bi Jun Luo ◽  
Dan Wu ◽  
Hai Hong Wu ◽  
Tao Wang ◽  
Xi Ping Huang
Keyword(s):  
Experimental Data ◽  
Crystallization Kinetics ◽  
Calcium Sulfate ◽  
Particle Number ◽  
Particle Number Density ◽  
Crystal Growth Rate ◽  
Number Density ◽  
Relationship Of ◽  
The Relationship ◽  
Kinetics Of

Crystallization kinetics experiment of calcium sulfate dehydrates, which is prepared by bittern under 30oC and different stirring speed conditions, is carried out. According to the results of the experimental data, the relationship of nucleus particle-number density n0 and crystal growth rate G with the residence time, temperature and the stirring speed is summarized. Also, the crystallization kinetics formula under 30oC and different stirring speed is given.

Crystallization kinetics of amorphous Ga–Sb–Te chalcogenide films: Part I. Nonisothermal studies by differential scanning calorimetry

2004 ◽  
Vol 19 (10) ◽  
pp. 2929-2937 ◽  
Author(s):  
Chain-Ming Lee ◽  
Yeong-Iuan Lin ◽  
Tsung-Shune Chin
Keyword(s):  
Activation Energy ◽  
Differential Scanning Calorimetry ◽  
Crystallization Kinetics ◽  
Crystallization Temperature ◽  
Ternary Phase Diagram ◽  
Film Deposition ◽  
Rate Dependency ◽  
Scanning Calorimetry ◽  
Kinetics Parameters ◽  
Kinetics Of

Nonisothermal crystallization kinetics of amorphous chalcogenide Ga–Sb–Te films with compositions along the pseudo-binary tie-lines connecting Sb7Te3−GaSb and Sb2Te3–GaSb of the ternary phase diagram were investigated by means of differential scanning calorimetry. Powder samples were prepared firstly by film deposition using a co-sputtering method; the films were then stripped from the substrate. The activation energy (Ea) and rate factor (Ko) were evaluated from the heating rate dependency of the crystallization temperature using the Kissinger method. The kinetic exponent (n) was deduced from the exothermic peak integrals using the Ozawa method. The crystallization temperature (Tx = 181 to 327 °C) and activation energy (Ea= 2.8 to 6.5 eV) increased monotonically with increasing GaSb content and reached a maximum value in compositions located at the vicinity of GaSb. The kinetic exponent is temperature dependent and shows higher values in the SbTe-rich compositions. Promising media compositions worthy of further studies were identified through the determined kinetics parameters.

Study on the Crystallization Kinetics of Polymer Thin Films

2012 ◽  
Vol 466-467 ◽  
pp. 102-105
Author(s):  
Yi Jin Ren
Keyword(s):  
Thin Film ◽  
Growth Rate ◽  
Film Thickness ◽  
Crystallization Kinetics ◽  
Crystallization Time ◽  
Crystal Thickness ◽  
Polymer Thin Film ◽  
Crystal Growth Mechanism ◽  
The Relationship ◽  
Kinetics Of

The crystallization kinetics of polymer thin film has a great difference from that in the bulk. Generally, the growth rate of the crystal confined in thin film reduces with decreasing film thickness, which is believed that the interaction between chains and substrate is responsible for the decrease of the growth rate. In addition, the ratio of film thickness over crystal thickness is also a key parameter in determining the growth rate. The relationship between the crystal lateral size and the crystallization time also dominates the crystal growth mechanism in polymer thin film.

Effects of Attapulgite on the Isothermal Crystallization Behavior of Poly(Butylene Succinate-co-Butylene Adipate)

2013 ◽  
Vol 791-793 ◽  
pp. 56-59
Author(s):  
Zhi Guo Qi ◽  
Jin Nan Chen ◽  
Bao Hua Guo ◽  
Yu Zhang
Keyword(s):  
Crystallization Kinetics ◽  
Crystallization Temperature ◽  
Isothermal Crystallization ◽  
Crystallization Behavior ◽  
Growth Form ◽  
Crystallization Rate ◽  
Melt Mixing ◽  
Butylene Succinate ◽  
Isothermal Crystallization Kinetics ◽  
Kinetics Of

Poly (butylene succinate-co-butylene adipate)/attapulgite nanocomposites were prepared by melt mixing in a HAAKE mixer. The crystallization kinetics of PBSA and its nanocomposites was studied under isothermal conditions by differential scanning calorimetr. The isothermal crystallization kinetics results indicated that attapulgite can induce heterogeneous nucleation, resulting in an improvement on the crystallization temperature and crystallization rate. Both the PBSA and its nanocomposites were correlated to the spherulitic growth form.

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