scholarly journals Physical Properties and Non-Isothermal Crystallisation Kinetics of Primary Mechanically Recycled Poly(l-lactic acid) and Poly(3-hydroxybutyrate-co-3-hydroxyvalerate)

Polymers ◽  
2021 ◽  
Vol 13 (19) ◽  
pp. 3396
Author(s):  
Luboš Běhálek ◽  
Jan Novák ◽  
Pavel Brdlík ◽  
Martin Borůvka ◽  
Jiří Habr ◽  
...  
Keyword(s):  
Lactic Acid ◽  
Physical Properties ◽  
Structural Changes ◽  
The Other ◽  
Half Time ◽  
Crystallisation Kinetics ◽  
Isothermal Crystallisation ◽  
Melt Crystallisation ◽  
Kinetics Of ◽  
Crystallisation Rate

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.

Structure of [(CH3)2NH2]2CoCl4 at elevated temperatures

1999 ◽  
Vol 55 (5) ◽  
pp. 752-757 ◽  
Author(s):  
Amir H. Mahmoudkhani ◽  
Vratislav Langer
Keyword(s):  
Crystal Structure ◽  
Hydrogen Bonding ◽  
Phase Transitions ◽  
Physical Properties ◽  
Electric Conductivity ◽  
Title Compound ◽  
Structural Changes ◽  
Elevated Temperatures ◽  
The Other ◽  
Cell Parameters

The crystal structure of the title compound, dimethylammonium tetrachlorocobaltate(II), has been determined at four temperatures between 297 and 366 K, in order to investigate possible phase transitions at 313 and 353 K [Kapustianik, Polovinko & Kaluza et al. (1996). Phys. Status Solidi A, 153, 117–122]. We found that there is no significant change either in the hydrogen-bonding network or in the cell parameters, apart from a linear dilatation with temperature. This study reveals that the anomalous variation in electric conductivity and some of the other physical properties of the compound cannot be explained by structural changes.

Studies of isothermal crystallisation kinetics of sunflower hard stearin-based confectionery fats

2013 ◽  
Vol 139 (1-4) ◽  
pp. 184-195 ◽  
Author(s):  
Miguel A. Bootello ◽  
Richard W. Hartel ◽  
Madeline Levin ◽  
Jose M. Martínez-Blanes ◽  
Concepción Real ◽  
...  
Keyword(s):  
Crystallisation Kinetics ◽  
Confectionery Fats ◽  
Isothermal Crystallisation ◽  
Kinetics Of

Non-Isothermal Crystallisation Kinetics of Polyamide 6/Mesoporous Silica Nanocomposites

2007 ◽  
Vol 15 (7) ◽  
pp. 561-567
Author(s):  
Qingyuan Hu ◽  
Xiangling Ji ◽  
Yunfeng Lu
Keyword(s):  
Differential Scanning Calorimetry ◽  
Mesoporous Silica ◽  
Polyamide 6 ◽  
Nucleating Agents ◽  
Scanning Calorimetry ◽  
Crystallisation Kinetics ◽  
Silica Nanocomposites ◽  
Crystallisation Process ◽  
Isothermal Crystallisation ◽  
Kinetics Of

Non-isothermal crystallisation kinetics of a polyamide 6/mesoporous silica nanocomposite (PA6-MS) has been investigated by differential scanning calorimetry (DSC) at different cooling rates. Mandelkern, Jeziorny-Ziabicki and Ozawa methods were applied to describe this crystallisation process. The analyses show that the mesoporous silica particles act as nucleating agents in the composite and that the Avrami exponent n varies from 3.0 to 4.6. The addition of mesoporous silica influenced the mechanism of nucleation and the growth of polyamide 6 (PA 6) crystallites.

Non-Isothermal Crystallisation Kinetics of In Situ Prepared Poly(ɛ-caprolactone)/Surface-Treated SiO2 Nanocomposites

2007 ◽  
Vol 208 (4) ◽  
pp. 364-376 ◽  
Author(s):  
Alexandros A. Vassiliou ◽  
George Z. Papageorgiou ◽  
Dimitrios S. Achilias ◽  
Dimitrios N. Bikiaris
Keyword(s):  
Crystallisation Kinetics ◽  
Sio2 Nanocomposites ◽  
Isothermal Crystallisation ◽  
Kinetics Of

scholarly journals Structural Changes During Air Drying of Fruits and Vegetables

2003 ◽  
Vol 9 (3) ◽  
pp. 201-206 ◽  
Author(s):  
I. N. Ramos ◽  
T. R.S. Brandão ◽  
C. L.M. Silva
Keyword(s):  
Physical Properties ◽  
Structural Changes ◽  
Fruits And Vegetables ◽  
Particle Density ◽  
Drying Process ◽  
Air Drying ◽  
New Approach ◽  
Volume Porosity ◽  
Textural Attributes ◽  
Kinetics Of

This work aims at reviewing structural changes occurring in convective air drying of fruits and vegetables. These include changes in physical properties, such as volume, porosity and bulk and particle density, which directlyaffect textural attributes of the products. Models relating with water content physical properties are also summarised. At microscopic level, the phenomena observed byprevious authors is described, focusing on shrinkage. In particular, a new approach on modelling kinetics of microstructural modifications is presented. Although the air drying process is relatively well studied, there is a lack of research concerning changes in structural properties. Modelling mass transfer during drying frequently does not include those effects and, there has not been established a standard methodologyfor predictive purposes. Correlating microstructure, texture measurements and sensoryanalysis would be an attractive area to be exploited for drying processes of fruits and vegetables. Although this is a wide working field, much is still to be done.

scholarly journals Correction: Ahmad, I.A., et al. Non-Isothermal Crystallisation Kinetics of Carbon Black-Graphene-Based Multimodal-Polyethylene Nanocomposites. Nanomaterials, 2019, 9, 100

Nanomaterials ◽  
2019 ◽  
Vol 9 (3) ◽  
pp. 392 ◽  
Author(s):  
Ibrahim Ahmad ◽  
Hyun-Kyung Kim ◽  
Suleyman Deveci ◽  
R. Kumar
Keyword(s):  
Carbon Black ◽  
Crystallisation Kinetics ◽  
Isothermal Crystallisation ◽  
Kinetics Of ◽  
Published Paper

In the published paper [1], there was a typo error mistake in Equation (5), which was supposed to be expressed as “ log Z t + n log t = log K T − m log Φ ” instead of “log Zt + n log t = log KT − ml” [...]

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