Influence of Thermal History on the Glass Transition of Poly(Phenylene Sulfide)

1990 ◽  
Vol 215 ◽  
Author(s):  
Pengtao Huo ◽  
Peggy Cebe
Keyword(s):  
Heat Capacity ◽  
Amorphous Phase ◽  
High Performance ◽  
Amorphous Polymer ◽  
Degree Of Crystallinity ◽  
Heat Of Fusion ◽  
Scanning Calorimetry ◽  
High Performance Polymer ◽  
Rigid Amorphous Phase ◽  
Rigid Amorphous

AbstractPPS is increasingly interesting as a high performance polymer material. Recently, Cheng, et al. [1] reported observation of rigid amorphous phase (RAP) in the amorphous phase of semicrystalline PPS using differential scanning calorimetry. Using the heat of fusion from DSC to obtain the degree of crystallinity of the semicrystalline samples, a simple rule of mixtures was applied to calculate the change in heat capacity step. The heat capacity decreased much more than could be accounted for using the measured crystallinity. Thus, these authors assumed the existence of a rigid amorphous phase which did not become liquid-like at Tg. The ratio of heat capacity step at Tg of semicrystalline PPS to that of the purely amorphous polymer was used to find the fraction of amorphous chains that do become liquid-like at Tg. The amount of RAP was then obtained by assuming a three phase model.

Studies of the Physical Properties of Cycloaliphatic Epoxy Resin Reacted with Anhydride Curing Agents

2017 ◽  
Vol 737 ◽  
pp. 248-255 ◽  
Author(s):  
Tae Hee Kim ◽  
Dae Yeon Kim ◽  
Choong Sun Lim ◽  
Bong Kuk Seo
Keyword(s):  
Physical Properties ◽  
Reaction Kinetics ◽  
Epoxy Resin ◽  
High Performance ◽  
Industrial Applications ◽  
Scanning Calorimetry ◽  
Low Viscosity ◽  
High Performance Polymer ◽  
Curing Agents ◽  
The Impact

The preparation of high performance epoxy composites for industrial applications has been extensively researched. In this report, we study the change in physical properties and reaction kinetics between epoxy resin and curing agents of similar geometry. For the experiments, celloxide 2021P, an epoxy resin having low viscosity, was blended with three different curing agents: methylhexahydropthalic acid, methyltetrahydropthalic acid, and 5-norbornene-2, 3-dicarboxylic anhydride. The amount of 1, 2-dimethylimidazole catalyst was controlled, and the highest heat flow temperature (Tpeak) was observed at around 145 °C. The impact on reaction kinetics relative to the change in heating rate was studied with differential scanning calorimetry (DSC) for each of the curing agents. The glass transition temperature (Tg) of each composition was measured with a second DSC cycle. The prepared epoxy compositions were thermally cured in a metallic mold to provide pure epoxy resins without fillers. Finally, the flexural strengths of these resins were compared to each other. The authors believe that insights into choosing an appropriate epoxy binder are useful when it comes to the overall preparation of high performance polymer composites.

scholarly journals Long-Term Physical Aging Tracked by Advanced Thermal Analysis of Poly(N-Isopropylacrylamide): A Smart Polymer for Drug Delivery System

Molecules ◽  
2020 ◽  
Vol 25 (17) ◽  
pp. 3810
Author(s):  
Anna Czerniecka-Kubicka ◽  
Iwona Zarzyka ◽  
Marek Pyda
Keyword(s):  
Drug Delivery ◽  
Thermal Analysis ◽  
Heat Capacity ◽  
Glass Transition ◽  
Physical Aging ◽  
Amorphous Polymer ◽  
Recovery Process ◽  
Scanning Calorimetry ◽  
Smart Polymer ◽  
Structural Recovery

Poly(N-isopropylacrylamide) (PNIPA), as a smart polymer, can be applied for drug delivery systems. This amorphous polymer can be exposed on a structural recovery process during the storage and transport of medicaments. For the physical aging times up to one year, the structural recovery for PNIPA was studied by advanced thermal analysis. The structural recovery process occurred during the storage of amorphous PNIPA below glass transition and could be monitored by the differential scanning calorimetry (DSC). The enthalpy relaxation (recovery) was observed as overshoot in change heat capacity at the glass transition region in the DSC during heating scan. The physical aging of PNIPA was studied isothermally at 400.15 K and also in the non-isothermal conditions. For the first time, the structural recovery process was analyzed in reference to absolute heat capacity and integral enthalpy in frame of their equilibrium solid and liquid PNIPA.

scholarly journals An insight on the process–property relationships of melt spun polylactic acid fibers

2019 ◽  
Vol 89 (23-24) ◽  
pp. 4959-4966 ◽  
Author(s):  
AM Ali ◽  
HM El-Dessouky
Keyword(s):  
Polylactic Acid ◽  
High Performance ◽  
Polarized Light ◽  
Degree Of Crystallinity ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
Laser Diffractometry ◽  
Wide Range ◽  
Innovative Materials ◽  
The Degree Of Crystallinity

Polylactic acid (PLA) fibers are receiving growing interest as one of the recent innovative materials being developed for various applications. The inherent biodegradability of PLA makes it highly attractive for the biomedical and health care sectors. PLA fibers need to be partially and/or highly oriented to allow high performance and readiness for a wide range of manufacturability. In this study, the structure and properties of PLA fibers, manufactured at different spinning speeds, were studied. Laser diffractometry, polarized light microscopy, differential scanning calorimetry (DSC) and X-ray diffraction (XRD) were used to determine the diameter, birefringence, molecular orientation, enthalpy and degree of crystallinity of as-spun and drawn PLA fibers. The results of DSC and XRD showed that the degree of crystallinity of the PLA fibers is significantly improved for the drawn PLA fibers compared to the as-spun fibers and leveled off in the case of changing the take-up speeds of drawn fibers.

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