scholarly journals Continuous Two-Domain Equations of State for the Description of the Pressure-Specific Volume-Temperature Behavior of Polymers

Polymers ◽  
2020 ◽  
Vol 12 (2) ◽  
pp. 409 ◽  
Author(s):  
Jian Wang ◽  
Christian Hopmann ◽  
Malte Röbig ◽  
Tobias Hohlweck ◽  
Cemi Kahve ◽  
...  
Keyword(s):  
Cooling Rate ◽  
Specific Volume ◽  
Equations Of State ◽  
Amorphous Polymer ◽  
Glassy State ◽  
Acrylonitrile Butadiene Styrene ◽  
Crystalline Polymer ◽  
Polymer Processing ◽  
Pvt Behavior ◽  
Fitting Accuracy

The two-domain Schmidt equation of state (EoS), which describes the pressure-specific volume–temperature (pvT) behavior of polymers in both the equilibrium molten/liquid state and non-equilibrium solid/glassy state, is often used in the simulation of polymer processing. However, this empirical model has a discontinuity problem and low fitting accuracy. This work derived a continuous two-domain pvT model with higher fitting accuracy compared with the Schmidt model. The cooling rate as an obvious influencing factor on the pvT behavior of polymers was also considered in the model. The interaction parameters of the equations were fitted with the experimental pvT data of an amorphous polymer, acrylonitrile-butadiene-styrene (ABS), and a semi-crystalline polymer, polypropylene (PP). The fitted results by the continuous two-domain EoS were in good agreement with the experimental data. The average absolute percentage deviations were 0.1% and 0.16% for the amorphous and semi-crystalline polymers, respectively. As a result, the present work provided a simple and useful model for the prediction of the specific volume of polymers as a function of temperature, pressure, and cooling rate.

Crystallization Behaviour of Polytetrafluoroethylene over very Large Cooling Rate Domains

2013 ◽  
Vol 747 ◽  
pp. 201-204
Author(s):  
Nicolas Bosq ◽  
Nathanaël Guigo ◽  
Nicolas Sbirrazzuoli
Keyword(s):  
Cooling Rate ◽  
Glassy State ◽  
Crystalline Polymer ◽  
Sem Analysis ◽  
Scanning Calorimetry ◽  
Theoretical Dependence ◽  
Cooling Rates ◽  
Fast Scanning Calorimetry ◽  
Wide Range ◽  
Fast Cooling

Polytetrafluoroethylene (PTFE) is a semi-crystalline polymer that demonstrates a very fast crystallization process on cooling. This study investigates the nonisothermal PTFE ultra-fast crystallization over a wide range of cooling rates via conventional Differential Scanning Calorimetry (DSC), Fast Scanning Calorimetry (FSC) and Ultra-Fast Scanning Calorimetry (UFSC). A new knowledge about crystallization kinetics of PTFE is obtained from the data obtained under very fast cooling rates. The shift of the melting peak to lower temperature shows that the crystals formed under fast cooling rates are slightly less stable than those produced under slower cooling rates. SEM analysis allows to observe these differences in crystal morphologies. According to the results, the crystallization is still present even for the fastest cooling rate employed and in consequences it is impossible to reach a metastable glassy state. The effective activation energy (Eα) displays a variation with the relative extent of crystallization (α) that is characteristic of a transition of PTFE crystallization from regime II to regime III around 312°C. Following the Hoffman-Lauritzen theory the Eα dependency obtained from the crystallizations under the different cooling rates was fitted in order to study the theoretical dependence of the growth rate.

Observing the relaxation of molecular orientation in sheared liquid crystalline polymer solutions

1990 ◽  
Vol 48 (4) ◽  
pp. 1092-1093
Author(s):  
Wendy Putnam ◽  
Christopher Viney
Keyword(s):  
Molecular Orientation ◽  
Liquid Crystalline Polymer ◽  
Liquid Crystalline ◽  
Crystalline Polymer ◽  
Polymer Processing ◽  
Molecular Alignment ◽  
Global Alignment ◽  
Shear Direction ◽  
Axial Strength ◽  
Strength And Stiffness

Liquid crystalline polymers (solutions or melts) can be spun into fibers and films that have a higher axial strength and stiffness than conventionally processed polymers. These superior properties are due to the spontaneous molecular extension and alignment that is characteristic of liquid crystalline phases. Much of the effort in processing conventional polymers goes into extending and aligning the chains, while, in liquid crystalline polymer processing, the primary microstructural rearrangement involves converting local molecular alignment into global molecular alignment. Unfortunately, the global alignment introduced by processing relaxes quickly upon cessation of shear, and the molecular orientation develops a periodic misalignment relative to the shear direction. The axial strength and stiffness are reduced by this relaxation.Clearly there is a need to solidify the liquid crystalline state (i.e. remove heat or solvent) before significant relaxation occurs. Several researchers have observed this relaxation, mainly in solutions of hydroxypropyl cellulose (HPC) because they are lyotropic under ambient conditions.

The effect of cooling rate on crystallization behavior and tensile properties of CF/PEEK composites

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Guangming Dai ◽  
Lihua Zhan ◽  
Chenglong Guan ◽  
Minghui Huang
Keyword(s):  
Cooling Rate ◽  
Crystallization Temperature ◽  
Crystallization Behavior ◽  
Crystalline Polymer ◽  
Scanning Calorimetry ◽  
Nonisothermal Crystallization ◽  
Cooling Rates ◽  
Control Range ◽  
Temperature Range ◽  
Transverse Tensile

Abstract In this study, the differential scanning calorimetry (DSC) tests were performed to measure the nonisothermal crystallization behavior of carbon fiber reinforced polyether ether ketone (CF/PEEK) composites under different cooling rates. The characteristic parameters of crystallization were obtained, and the nonisothermal crystallization model was established. The crystallization temperature range of the material at different cooling rates was predicted by the model. The unidirectional laminates were fabricated at different cooling rates in the crystallization temperature range. The results showed that the crystallization temperature range shifted to a lower temperature with the increase of cooling rate, the established nonisothermal crystallization model was consistent with the DSC test results. It is feasible to shorten the cooling control range from the whole process to the crystallization range. The crystallinity and transverse tensile strength declined significantly with the increase of the cooling rate in the crystallization temperature range. The research results provided theoretical support for the selection of cooling conditions and temperature control range, which could be applied to the thermoforming process of semi-crystalline polymer matrixed composites to improve the manufacturing efficiency.

Study of the Influence of Surface Mold Deposits on the Demolding Stage of the Injection Molding Process of Thermoplastics

2006 ◽  
Author(s):  
Mikae¨l Chailly ◽  
Vincent Gilbert ◽  
Jean-Yves Charmeau ◽  
Yves Bereaux
Keyword(s):  
Amorphous Polymer ◽  
Infrared Camera ◽  
Acrylonitrile Butadiene Styrene ◽  
Injection Molding Process ◽  
Mold Surface ◽  
Molding Process ◽  
Injection Process ◽  
Molded Parts ◽  
Styrene Acrylonitrile ◽  
Thermal Influence

Due to increasing expectings from the market, the aspect of molded parts has to be improved. Some of the defects observed such as scratches on these parts is related to the demolding stage. To limit this, we investigated the influence on demolding forces using various surface deposits on the mold surface, mainly PVD and PACVD deposits : Chromium nitrium (CrN), Titane nitrium (TiN), Diamond like Carbon (DLC), glassy deposit (SiOx), Chromium and polished steel on an cube-shaped insert in an instrumented mold (with force sensors). Injection campaign was led on three polymers which differ in terms of nature : an amorphous polymer (polycarbonate), a semi-crystalline one (polybutylene terephatalate) and one mix of copolymers (styrene acrylonitrile/ acrylonitrile butadiene styrene). We studied the evolution of these forces through the demolding stage. This allowed us to evaluate the work energy necessary to eject the part from the insert, and to correlate those data to shrinkage of the polymer part, adhesion between polymer and mold surface and friction coefficient between those surfaces during the demolding stage. We also measured the influence the surface temperature of the part just before the demolding stage thanks to an infrared camera to investigate the thermal influence of these deposits in the injection process. Our results show an influence of deposits on demolding forces which is strongly dependent on nature of the polymer (of course) but also on its chemical nature. They also have a slight influence on temperature of the part even if they are only a few microns thick. We therefore developped a method to evaluate surface deposits and their impact on demolding forces, in terms of adhesion polymer/treament and friction.

Effect of polymer donor aggregation on the active layer morphology of amorphous polymer acceptor-based all-polymer solar cells

2020 ◽  
Vol 8 (16) ◽  
pp. 5613-5619 ◽  
Author(s):  
Lu Zhang ◽  
Zicheng Ding ◽  
Ruyan Zhao ◽  
Feng Jirui ◽  
Wei Ma ◽  
...  
Keyword(s):  
Solar Cells ◽  
Phase Separation ◽  
Active Layer ◽  
Amorphous Polymer ◽  
Polymer Solar Cells ◽  
Crystalline Polymer ◽  
Dominant Factor ◽  
Polymer Acceptor ◽  
Aggregation Tendency

The aggregation tendency in solution of polymer donors is the dominant factor in the phase separation of semi-crystalline polymer donor/amorphous polymer acceptor blends in all-PSCs.

The Experimental Prediction of the Lifetime of Acrylonitrile Butadiene Styrene (ABS) by the Energetic Method

2019 ◽  
Vol 820 ◽  
pp. 147-158
Author(s):  
Abderrazak En-Naji ◽  
Nadia Mouhib ◽  
Fatima Majid ◽  
Hicham ElKihal ◽  
Mohamed El Ghorba
Keyword(s):  
Amorphous Polymer ◽  
Energy Parameter ◽  
Acrylonitrile Butadiene Styrene ◽  
Tensile Tests ◽  
Experimental Models ◽  
Uniaxial Tensile ◽  
Unified Theory ◽  
Theoretical Evaluation ◽  
Life Fraction ◽  
Butadiene Styrene

In this paper, we are dealing with the study of the mechanical behavior of an amorphous polymer, acrylonitrile butadiene styrene "ABS". In fact, uniaxial tensile tests on rectangular specimens containing a combined defect, with simple and double notches, has been done. The proposed approach develop a method, based on energy parameter, to calculate the evolution of damage over the materials’ life. This method can be used to predict quantitatively the risk of sudden rupture in a structure. Therefore, the damage evaluation based on the residual energy method was compared to the unified theory one for different loading levels. The prediction of damage by experimental models has led to the determination of the three stages of damage evolution, which are the initiation, propagation and complete deterioration of the material. Thus, the concept of reliability is used to specify the critical life fraction, which is similar to the notch depth (βc) of a modeled defect as a combined defect on an ABS sample. In addition, the unified theory was used in this work, to define on the one hand, the parameter of damage which is the internal variable which describes the failure level of the structure in function of life fraction, on the other hand, for the theoretical evaluation of the level of damage. Finally, we have proved that the theoretical and experimental results show a good agreement.

scholarly journals Phase Structure Recording in a Nematic Side-Chain Liquid-Crystalline Polymer

Polymers ◽  
2020 ◽  
Vol 12 (2) ◽  
pp. 356 ◽  
Author(s):  
Ivan Budagovsky ◽  
Aleksey Kuznetsov ◽  
Sergey Shvetsov ◽  
Mikhail Smayev ◽  
Alexander Zolot’ko ◽  
...  
Keyword(s):  
Liquid Crystalline ◽  
Modulation Depth ◽  
Glassy State ◽  
Continuum Theory ◽  
Crystalline Polymer ◽  
Optical Nonlinearity ◽  
Side Chain ◽  
Phenyl Benzoate ◽  
Chain Polymer ◽  
Methylene Groups

Dye-doped nematic side-chain liquid-crystalline polymers possess extraordinary large optical nonlinearity and ability to store the induced orientational deformations in a glassy state, which makes them a very promising material for photonic applications. In this study, the phase structures were generated and recorded in the bulk of a 50-μm layer of a nematic liquid-crystalline side-chain polymer, containing polyacrylate backbone, spacer having five methylene groups, and phenyl benzoate mesogenic fragment. The polymer was doped with KD-1 azodye. The director field deformations induced by the light beam close to the TEM01 mode were studied for different geometries of light–polymer interaction. The phase modulation depth of 2π was obtained for the 18-μm spacing between intensity peaks. The experimental data were analyzed based on the elastic continuum theory of nematics. The possibility to induce and record positive and negative microlenses in the polymer bulk was shown experimentally.

Kinetic immiscibility of crystalline polymer/amorphous polymer blends

Polymer ◽  
1997 ◽  
Vol 38 (9) ◽  
pp. 2171-2174 ◽  
Author(s):  
Arun K. Nandi ◽  
Pralay Maiti
Keyword(s):  
Polymer Blends ◽  
Amorphous Polymer ◽  
Crystalline Polymer
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