Rheological Characteristics of Gum Elastomers

1976 ◽  
Vol 49 (1) ◽  
pp. 52-63 ◽  
Author(s):  
N. Nakajima ◽  
E. A. Collins
Keyword(s):  
Deformation Rate ◽  
Viscoelastic Properties ◽  
Time Pressure ◽  
Pressure Time ◽  
Ultimate Properties ◽  
Rupture Energy ◽  
Rate Plot ◽  
As Stress ◽  
Temperature Time

Abstract A systematic characterization of gum elastomers may be done by measuring viscoelastic and ultimate properties. The viscoelastic properties of amorphous elastomers can be reduced to a master curve by means of the temperature-time, pressure-time, and strain-time correspondence principles. If a structure, e.g. crystallinity, develops with a change of temperature, pressure, or strain, such structural change may be regarded as a deviation. The ultimate properties may be represented either as stress-strain at break, modulus-strain at break, rupture-energy-deformation-rate, or stress-at-break-deformation-rate and strain-at-break-deformation-rate. The modulus-strain-at-break plot shows promise for interpreting mill processability in terms of the basic rheological properties. The rupture-energy-deformation-rate plot supplies a useful quantitative input for mill mixing.

Time in International Organizations and International Organizations in Time

2019 ◽  
Author(s):  
Eugénia C. Heldt
Keyword(s):  
International Organizations ◽  
Path Dependence ◽  
Time Pressure ◽  
Temporal Dimension ◽  
Incremental Change ◽  
Critical Junctures ◽  
Pressure Time ◽  
Multilateral System ◽  
System Time ◽  
Over Time

Time plays a central role in international organizations (IOs). Interactions among actors are embedded in a temporal dimension, and actors use formal and informal time rules, time discourses, and time pressure to obtain concessions from their counterparts. By the same token, legacies and innovations within and outside IOs can be examined as a dynamic process evolving over time. Against this background, this chapter has a twofold aim. First, it examines how actors use time in IOs with a particular focus on multilateral negotiations to justify their actions. Drawing on international relations studies and negotiation analysis, this piece explores six different dimensions of time in the multilateral system: time pressure, time discourse, time rules, time costs, time horizons, and time as a resource. Second, this chapter delineates the evolution of IOs over time with the focus on innovations that emerge to adapt their institutional system to new political and economic circumstances. This piece looks particularly at endogenous and exogenous changes in IOs, recurring to central concepts used by historical institutionalism, including path dependence, critical junctures, and sequencing. This allows us to map patterns of incremental change, such as displacement, conversion, drift, and layering.

scholarly journals Synthesis and Characterization of Co-Mo/γ-Alumina Catalyst from local Kaolin clay for Hydrodesulfurization of Iraqi Naphtha

2021 ◽  
Vol 11 (1) ◽  
pp. 84-106
Author(s):  
Nada Sadoon Ahmed zeki ◽  
Sattar Jalil Hussein ◽  
Khalifa K. Aoyed ◽  
Saad Kareem Ibrahim ◽  
Ibtissam K. Mehawee
Keyword(s):  
Surface Area ◽  
Sulfur Removal ◽  
Sulfuric Acid Concentration ◽  
Bet Surface Area ◽  
X Ray Diffraction ◽  
X Ray ◽  
Mo Catalyst ◽  
Pressure Time ◽  
Al2o3 Catalyst

This work deals with the hydrodesulfurization of three types of naphtha feedstocks; mixednaphtha (WN), heavy naphtha (HN) & light naphtha (LN) with a sulfur content of 1642.1,1334.9 & 709 ppm respectively, obtained from Missan refinery using prepared Co-Mo/γ-Al2O3catalyst. The Iraqi white kaolin was used as a starting material for the preparation of γ-Al2O3support, transferring kaolin to meta-kaolin was studied through calcination at differenttemperatures and durations, kaolin structure was investigated using X-Ray diffractiontechniques.High purity 94.83%. Crystalline γ-Al2O3 with a surface area of 129.91 m2/gm, pore volume0.9002 cm3/g was synthesized by extraction of Iraqi kaolin with H2SO4 at different acid to clayweight ratios, acid concentrations & leaching time. Ethanol was used as precipitating agent; theresultant gel was dried and calcined at 70OC, 10 hrs & 900 OC, 2 hrs respectively.The effects of different parameters on the average crystallinity and extraction % ofsynthesized γ-Al2O3 were studied like; acid: clay ratio, sulfuric acid concentration, leachingtime, leaching temperature & kaolin conversion to metakaolin. Characterization of prepared γ-Al2O3 & Co-Mo catalyst were achieved by X-ray diffraction, FTIR-spectra, texture properties& BET surface area, BJH N2 adsorption porosity, AFM, SEM, crush strength & XRF tests. Co-Mo/ γ-Al2O3 catalyst with final loading 5.702 wt% and 21.45 wt% of Co and Mo oxidesrespectively was prepared by impregnation methods.The activity of prepared Co-Mo/γ-Al2O3 catalyst after moulding to be tested forhydrodesulfurization (HDS) of naphtha feedstock W.N, H.N & L.N was performed using apilot hydrotreating unit at petroleum research & development centre, at different operatingconditions. Effects of temperature, LHSV, pressure, time & pore size distribution were studied,the best percentage of sulfur removal is increased with decreasing LHSV to 2 hr-1 as a generaltrend to be 89.71, 99.72, 99.20 % at 310oC for the whole naphtha, heavy naphtha and lightnaphtha feedstocks respectively, at 34 bar pressure and 200/200 cm3/cm3 H2/HC ratio.

Characterization of viscoelastic properties of polymeric materials through nanoindentation

2005 ◽  
Vol 45 (2) ◽  
pp. 130-136 ◽  
Author(s):  
G. M. Odegard ◽  
T. S. Gates ◽  
H. M. Herring
Keyword(s):  
Viscoelastic Properties ◽  
Polymeric Materials

Towards mechanical characterization of granular biofilms by optical coherence elastography measurements of circumferential elastic waves

Soft Matter ◽  
2019 ◽  
Vol 15 (28) ◽  
pp. 5562-5573 ◽  
Author(s):  
Hong-Cin Liou ◽  
Fabrizio Sabba ◽  
Aaron I. Packman ◽  
Alex Rosenthal ◽  
George Wells ◽  
...  
Keyword(s):  
Elastic Waves ◽  
Viscoelastic Properties ◽  
Mechanical Characterization ◽  
Optical Coherence ◽  
Model Based

This paper presents a metrology approach combining optical coherence elastography measurements of circumferential elastic waves and model-based inverse analyses to nondestructively characterize the viscoelastic properties of soft spherical gels.

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