Enhancing the melt crystallization of polymers, especially slow crystallizing polymers like PLLA and PET

2020 ◽  
Vol 3 (1) ◽  
Author(s):  
Alan E. Tonelli
Keyword(s):  
Melt Crystallization ◽  
Crystallization Of Polymers ◽  
Crystallizing Polymers

scholarly journals Enthalpy Relaxation, Crystal Nucleation and Crystal Growth of Biobased Poly(butylene Isophthalate)

Polymers ◽  
2020 ◽  
Vol 12 (1) ◽  
pp. 235 ◽  
Author(s):  
Silvia Quattrosoldi ◽  
René Androsch ◽  
Andreas Janke ◽  
Michelina Soccio ◽  
Nadia Lotti
Keyword(s):  
Glass Transition ◽  
Low Temperature ◽  
Crystal Nucleation ◽  
Melt Crystallization ◽  
Nucleation Behavior ◽  
Low Temperature Annealing ◽  
Poly Ethylene Terephthalate ◽  
Lamellar Crystals ◽  
Poly Ethylene ◽  
Crystallizing Polymers

The crystallization behavior of fully biobased poly(butylene isophthalate) (PBI) has been investigated using calorimetric and microscopic techniques. PBI is an extremely slow crystallizing polymer that leads, after melt-crystallization, to the formation of lamellar crystals and rather large spherulites, due to the low nuclei density. Based upon quantitative analysis of the crystal-nucleation behavior at low temperatures near the glass transition, using Tammann’s two-stage nuclei development method, a nucleation pathway for an acceleration of the crystallization process and for tailoring the semicrystalline morphology is provided. Low-temperature annealing close to the glass transition temperature (Tg) leads to the formation of crystal nuclei, which grow to crystals at higher temperatures, and yield a much finer spherulitic superstructure, as obtained after direct melt-crystallization. Similarly to other slowly crystallizing polymers like poly(ethylene terephthalate) or poly(l-lactic acid), low-temperature crystal-nuclei formation at a timescale of hours/days is still too slow to allow non-spherulitic crystallization. The interplay between glass relaxation and crystal nucleation at temperatures slightly below Tg is discussed.

Effect of Electrical Aging on the Trap Parameter of HVAC XLPE Cable Insulation

2014 ◽  
Vol 672-674 ◽  
pp. 769-772
Author(s):  
Wei Wei Li ◽  
Qiang Shi ◽  
Chi Wu
Keyword(s):  
Crystallization Process ◽  
Melt Crystallization ◽  
Depolarization Current ◽  
Cable Insulation ◽  
Trap Charge ◽  
Xlpe Cable ◽  
Trap Parameter ◽  
Start Up ◽  
Electrical Aging ◽  
Two Peaks

The effect of electrical aging on the trap parameter of HVAC XLPE cable insulation was investigated in this work. Thermally Stimulated Current (TSC) was used to measure depolarization current. The variation of trap parameter was calculated by means of start-up method based on the Gaussian fitting curve of TSC data. It was found that, the activation energy and the amount of trap charge obtained from TSC peak at 243K and 348K were increased after electrical aging, which may be benefit to characterize the degree of aging. The amount of trap charge in the two peaks increases as the increase of oxide dipole after electrical aging. And charge trapped described by the TSC peak at melting temperature increased after aging. It is considered that the increase of charge in the TSC peak can be attributed to the release of trap charge in the melt crystallization process, which corresponds to the α relaxation process in XLPE insulation.

The effect of aliphatic chain length on thermal properties of poly(alkylene dicarboxylate)s

e-Polymers ◽  
2007 ◽  
Vol 7 (1) ◽  
Author(s):  
Corrado Berti ◽  
Annamaria Celli ◽  
Paola Marchese ◽  
Elisabetta Marianucci ◽  
Giancarlo Barbiroli ◽  
...  
Keyword(s):  
Thermal Properties ◽  
Three Dimensional ◽  
The Other ◽  
Aliphatic Chain ◽  
Melting Temperatures ◽  
Avrami Analysis ◽  
Isothermal Analysis ◽  
Dimensional Growth ◽  
Crystallizing Polymers ◽  
Crystalline Forms

AbstractSome poly(alkylene dicarboxylate)s, derived from ethanediol or 1,4- butanediol and different diacids, have been synthesized and analyzed by DSC to determine the correlations existing between the thermal properties and the length of the aliphatic chain. The polymers show crystallization and melting temperatures and enthalpies which increase as the polymethylene segments lengthen, due to the formation of more stable crystals. The samples derived from ethanediol are peculiar; they show reorganization processes during the melting and the melting temperatures are notably higher with respect to those of the other polyesters. This behavior is discussed. Isothermal analysis highlights that poly(alkylene dicarboxylate)s are fast crystallizing polymers. The Avrami analysis suggests a crystallization mechanism characterized by heterogeneous nucleation and three dimensional growth; secondary crystallizations is present only in the samples characterized by short -(CH2)- sequences, due to the reorganization of less perfect crystalline forms. A comparative study between the crystallization rates as a function of the undercooling is reported.

scholarly journals The Effect of WS2 Nanosheets on the Non-Isothermal Cold- and Melt-Crystallization Kinetics of Poly(l-lactic acid) Nanocomposites

Polymers ◽  
2021 ◽  
Vol 13 (13) ◽  
pp. 2214
Author(s):  
Mohammed Naffakh ◽  
Pablo Rica ◽  
Carmen Moya-Lopez ◽  
José Antonio Castro-Osma ◽  
Carlos Alonso-Moreno ◽  
...  
Keyword(s):  
Lactic Acid ◽  
Transition Metal Dichalcogenides ◽  
Crystallization Rate ◽  
Melting Behavior ◽  
Hybrid Nanocomposites ◽  
Melt Crystallization ◽  
Heating Rates ◽  
Solution Blending ◽  
New Perspective ◽  
Ws2 Nanosheets

In the present work, hybrid nanocomposite materials were obtained by a solution blending of poly(l-lactic acid) (PLLA) and layered transition-metal dichalcogenides (TMDCs) based on tungsten disulfide nanosheets (2D-WS2) as a filler, varying its content between 0 and 1 wt%. The non-isothermal cold- and melt-crystallization and melting behavior of PLLA/2D-WS2 were investigated. The overall crystallization rate, final crystallinity, and subsequent melting behavior of PLLA were controlled by both the incorporation of 2D-WS2 and variation of the cooling/heating rates. In particular, the analysis of the cold-crystallization behavior of the PLLA matrix showed that the crystallization rate of PLLA was reduced after nanosheet incorporation. Unexpectedly for polymer nanocomposites, a drastic change from retardation to promotion of crystallization was observed with increasing the nanosheet content, while the melt-crystallization mechanism of PLLA remained unchanged. On the other hand, the double-melting peaks, mainly derived from melting–recrystallization–melting processes upon heating, and their dynamic behavior were coherent with the effect of 2D-WS2 involved in the crystallization of PLLA. Therefore, the results of the present study offer a new perspective for the potential of PLLA/hybrid nanocomposites in targeted applications.

Sign in / Sign up

Export Citation Format

Share Document