Changes in moisture effective diffusivity and glass transition temperature of paddy during drying

Objective: A new poly(ionic liquid)(PIL), poly(p-vinylbenzyltriphenylphosphine hexafluorophosphate) (P[VBTPP][PF6]), was synthesized by quaternization, anion exchange reaction, and free radical polymerization. Then a series of the PIL were synthesized at different conditions. Methods: The specific heat capacity, glass-transition temperature and melting temperature of the synthesized PILs were measured by differential scanning calorimeter. The thermal conductivities of the PILs were measured by the laser flash analysis method. Results: Results showed that, under optimized synthesis conditions, P[VBTPP][PF6] as the thermal insulator had a high glass-transition temperature of 210.1°C, high melting point of 421.6°C, and a low thermal conductivity of 0.0920 W m-1 K-1 at 40.0°C (it was 0.105 W m-1 K-1 even at 180.0°C). The foamed sample exhibited much low thermal conductivity λ=0.0340 W m-1 K-1 at room temperature, which was comparable to a commercial polyurethane thermal insulating material although the latter had a much lower density. Conclusion: In addition, mixing the P[VBTPP][PF6] sample into polypropylene could obviously increase the Oxygen Index, revealing its efficient flame resistance. Therefore, P[VBTPP][PF6] is a potential thermal insulating material.

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High-temperature carbon plastics based on thermoreactive polyimide binder

Voprosy Materialovedeniya ◽

10.22349/1994-6716-2020-103-3-89-102 ◽

2020 ◽

pp. 89-102

Author(s):

M. I. Valueva ◽

I. V. Zelenina ◽

M. A. Zharinov ◽

M. A. Khaskov

Keyword(s):

Glass Transition ◽

High Temperature ◽

Transition Temperature ◽

Glass Transition Temperature ◽

Strength Properties ◽

High Glass Transition Temperature ◽

Reinforced Plastics ◽

Carbon Plastics ◽

Fundamental Possibility ◽

Fiber Reinforced Plastics

The article presents results of studies of experimental carbon plastics based on thermosetting PMRpolyimide binder. Сarbon fiber reinforced plastics (CFRPs) are made from prepregs prepared by melt and mortar technologies, so the rheological properties of the polyimide binder were investigated. The heat resistance of carbon plastics was researched and its elastic-strength characteristics were determined at temperatures up to 320°С. The fundamental possibility of manufacturing carbon fiber from prepregs based on polyimide binder, obtained both by melt and mortar technologies, is shown. CFRPs made from two types of prepregs have a high glass transition temperature: 364°C (melt) and 367°C (solution), with this temperature remaining at the 97% level after boiling, and also at approximately the same (86–97%) level of conservation of elastic strength properties at temperature 300°С.

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Studies on the Modification of Commercial Bisphenol-A-Based Epoxy Resin Using Different Multifunctional Epoxy Systems

Applied Mechanics ◽

10.3390/applmech2020023 ◽

2021 ◽

Vol 2 (2) ◽

pp. 419-430

Author(s):

Ankur Bajpai ◽

James R. Davidson ◽

Colin Robert

Keyword(s):

Mechanical Properties ◽

Glass Transition ◽

Transition Temperature ◽

Glass Transition Temperature ◽

Bisphenol A ◽

Epoxy Resin ◽

Tensile Fracture ◽

Chemical Structures ◽

Amino Phenol ◽

Epoxy Systems

The tensile fracture mechanics and thermo-mechanical properties of mixtures composed of two kinds of epoxy resins of different chemical structures and functional groups were studied. The base resin was a bi-functional epoxy resin based on diglycidyl ether of bisphenol-A (DGEBA) and the other resins were (a) distilled triglycidylether of meta-amino phenol (b) 1, 6–naphthalene di epoxy and (c) fluorene di epoxy. This research shows that a small number of multifunctional epoxy systems, both di- and tri-functional, can significantly increase tensile strength (14%) over neat DGEBA while having no negative impact on other mechanical properties including glass transition temperature and elastic modulus. In fact, when compared to unmodified DGEBA, the tri-functional epoxy shows a slight increase (5%) in glass transition temperature at 10 wt.% concentration. The enhanced crosslinking of DGEBA (90 wt.%)/distilled triglycidylether of meta-amino phenol (10 wt.%) blends may be the possible reason for the improved glass transition. Finally, the influence of strain rate, temperature and moisture were investigated for both the neat DGEBA and the best performing modified system. The neat DGEBA was steadily outperformed by its modified counterpart in every condition.

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