Strength of Sulfur-Linked Elastomers

1996 ◽  
Vol 69 (4) ◽  
pp. 577-590 ◽  
Author(s):  
H. Chun ◽  
A. N. Gent
Keyword(s):  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Crack Propagation ◽  
Test Temperature ◽  
Effective Rate ◽  
Master Curves ◽  
Universal Form ◽  
Wlf Equation ◽  
Test Conditions

Abstract Fracture energies have been determined for tearing through a sheet of a polysulfide elastomer, and for peeling apart two sheets bonded together with sulfur interlinks. Measurements were made over wide ranges of rate of crack propagation and test temperature. By shifting curves at various temperatures along the rate axis, using shift factors aT calculated from the “universal” form of the WLF equation, master curves were obtained for tear and peel energy vs. rate of tear or peel at the glass transition temperature Tg about −55°C. These master curves of strength vs. effective rate of crack propagation at Tg were closely similar to those obtained previously for several hydrocarbon elastomers: BR, SBR and EPR; interlinked with C-C bonds. Thus, under comparable test conditions the strength of the present polysulfide elastomer with sulfur crosslinks is similar to that for hydrocarbon elastomers with C-C crosslinks. The question then arises: Why are sulfur-vulcanized elastomers stronger in common experience than peroxide-cured ones? Possible reasons are discussed.

Measurement of Stress-Optical Coefficients of COC’s with Different Composition

2006 ◽  
Vol 326-328 ◽  
pp. 183-186 ◽  
Author(s):  
Jong Sun Kim ◽  
Kyung Hwan Yoon ◽  
Julia A. Kornfield
Keyword(s):  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Extreme Values ◽  
Frequency Region ◽  
Master Curves ◽  
Type Device ◽  
The Difference ◽  
Optical And Mechanical Properties ◽  
Cyclic Olefin Copolymers

Rheo-optical and mechanical properties of Cyclic Olefin Copolymers(COC’s) with different composition have been investigated across the glass transition temperature. Accurate measurement of stress or strain-optical coefficients and elastic modulus data across the glass transition are essential for predicting optical anisotropy in many optical products like pickup lenses and waveguides in LCD backlight unit since the material of these products have both flow and thermal history from the melt to glass. To obtain stress-optic behavior in the wide frequency region including rubbery, glassy and glass transition regime, extensional bar-type device was used. A shear-sandwich tool was used in the melt region. Master curves for modulus, stress-optical and strain-optical coefficients have been obtained in wide frequency region. The stress-optical coefficients of COC’s with mol fraction of norbornene, 60 ~ 70%, showed almost constant between -8 and -9 Br at glassy region and between +920 and +1,160 Br in the melt region. Even though the glass transition temperature showed the difference of 35, the stress-optical coefficients of COC’s with different composition showed almost same extreme values

Critical Cooling Rate Vs. Reduced Glass Transition: Scaling Factors and Master Curves

1998 ◽  
Vol 554 ◽  
Author(s):  
N. Clavaguera ◽  
M. T. Clavaguera-Mora
Keyword(s):  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Cooling Rate ◽  
Glass Formation ◽  
Supercooled Liquid ◽  
High Viscosity ◽  
Master Curves ◽  
Critical Cooling Rate ◽  
Equilibrium Solidification

AbstractThe aim of the present paper is to analyse the glass formation and stability of bulk metallic glasses. Attention is focused to metallic alloys as systems which may develop a large glassforming ability. Glass formation when quenching from the liquid state is discussed in terms of the thermodynamics and kinetics of the stable/metastable competing phases. Thermodynamics is required to relate glass transition temperature, Tg, to the energetics of the supercooled liquid. Kinetic destabilisation of equilibrium solidification and, consequently, glass forming ability are favoured by the high viscosity values achieved under continuous cooling. The relative thermal stability of the supercooled liquid depends on the thermodynamic driving force and interfacial energy between each competing nucleating phase and the molten alloy. It is shown that the quantities representative of the process, once scaled, have a temperature dependence that is mostly fixed by the reduced glass transition temperature, Tgr= Tg/Tm, Tm being the melting temperature. Based on the classical models of nucleation and crystal growth, the reduced critical cooling rate is shown to follow master curves when plotted against Tgr. Experimental trends for specific systems are compared to predicted values from these master curves.

A Novel Poly(Ionic Liquid) as the Thermal Insulating Material

2020 ◽  
Vol 13 (3) ◽  
pp. 241-247
Author(s):  
Wenxin Wei ◽  
Guifeng Ma ◽  
Hongtao Wang ◽  
Jun Li
Keyword(s):  
Thermal Conductivity ◽  
Ionic Liquid ◽  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Flame Resistance ◽  
Insulating Material ◽  
Low Thermal Conductivity ◽  
Thermal Insulating ◽  
Poly Ionic Liquid

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.

Sign in / Sign up

Export Citation Format

Share Document