Glass Transitions in Polymer-Plasticizer Systems

1956 ◽  
Vol 29 (2) ◽  
pp. 492-503
Author(s):  
L. Breitman
Keyword(s):  
Low Temperature ◽  
Dibutyl Phthalate ◽  
Supercooled Liquids ◽  
Glass Transitions ◽  
Volume Increase ◽  
Temperature Coefficients ◽  
Dibutyl Sebacate ◽  
Apparent Activation Energies ◽  
Coefficient Of Viscosity ◽  
Polymer Interaction

Abstract A summary of the investigation with the three types of diluent can he made with reference to Table VI. Hydrocarbon oils are more effective low-temperature plasticizers the lower their temperature coefficient of viscosity. Dibutyl sebacate is representative of crystallizing diluents. Such compounds are ineffective low temperature plasticizers unless, (a) at equilibrium, favorable thermodynamic parameters permit their existence as liquids in the polymer, or (b) the plasticizers tend to exist as the nonequilibrium, supercooled, liquids in the transition temperature region of the polymer. Particularly desirable are liquids with low apparent activation energies of viscosity and high miscibility with polymer. The four ester plasticizers, tributoxyethyl phosphate, dibutyl phthalate, dioetyl adipate, and dioctyl sebacate, have temperature coefficients of viscosity corresponding to a virtually common activation energy of 4.5 kilocalories. Here, the magnitude of diluent-polymer interaction, as indicated by volume increase measurements, dictates the order of effectiveness of the ester.

scholarly journals THE EFFECT OF RENNIN UPON CASEIN

1927 ◽  
Vol 10 (6) ◽  
pp. 987-1005 ◽  
Author(s):  
Vladimir Pertzoff
Keyword(s):  
Low Temperature ◽  
Free Enzyme ◽  
The Other ◽  
Temperature Coefficients ◽  
Temperature Levels ◽  
Two Temperature

1. The preparation and purification of paracasein was described and certain criteria for the absence of free enzyme provided for. 2. The solubility of purified paracasein in water at low temperature was studied, and found practically identical with the solubility of casein. 3. The capacity of paracasein to bind base was investigated by means of its solubility in NaOH at 5° and at 23° ± 2°C., and found to be distinctly different from that of casein. 4. At these two temperature levels paracasein had a 1.5 greater capacity to bind base than casein. The equivalent combining weights of paracasein and casein were found to stand each to the other, apapproximately, as 2 to 3. 5. This relationship suggested that the temperature coefficients of the solubility of paracasein and casein in NaOH are identical. 6. This evidence indicates that paracasein is a modification of casein, distinguishable by physicochemical means.

scholarly journals Material Discovery and High Throughput Exploration of Ru Based Catalysts for Low Temperature Ammonia Decomposition

Materials ◽  
2020 ◽  
Vol 13 (8) ◽  
pp. 1869 ◽  
Author(s):  
Katherine McCullough ◽  
Pei-Hua Chiang ◽  
Juan D. Jimenez ◽  
Jochen A. Lauterbach
Keyword(s):  
Low Temperature ◽  
High Throughput ◽  
Bimetallic Catalysts ◽  
Active Sites ◽  
Operating Conditions ◽  
Ammonia Decomposition ◽  
Turnover Frequency ◽  
Surface Sites ◽  
Equivalent Number ◽  
Apparent Activation Energies

High throughput experimentation has the capability to generate massive, multidimensional datasets, allowing for the discovery of novel catalytic materials. Here, we show the synthesis and catalytic screening of over 100 unique Ru-Metal-K based bimetallic catalysts for low temperature ammonia decomposition, with a Ru loading between 1–3 wt% Ru and a fixed K loading of 12 wt% K, supported on γ-Al2O3. Bimetallic catalysts containing Sc, Sr, Hf, Y, Mg, Zr, Ta, or Ca in addition to Ru were found to have excellent ammonia decomposition activity when compared to state-of-the-art catalysts in literature. Furthermore, the Ru content could be reduced to 1 wt% Ru, a factor of four decrease, with the addition of Sr, Y, Zr, or Hf, where these secondary metals have not been previously explored for ammonia decomposition. The bimetallic interactions between Ru and the secondary metal, specifically RuSrK and RuFeK, were investigated in detail to elucidate the reaction kinetics and surface properties of both high and low performing catalysts. The RuSrK catalyst had a turnover frequency of 1.78 s−1, while RuFeK had a turnover frequency of only 0.28 s−1 under identical operating conditions. Based on their apparent activation energies and number of surface sites, the RuSrK had a factor of two lower activation energy than the RuFeK, while also possessing an equivalent number of surface sites, which suggests that the Sr promotes ammonia decomposition in the presence of Ru by modifying the active sites of Ru.

The Master Equation for the Dissociation of a Dilute Diatomic Gas. X. How Rotation Causes Low Arrhenius Temperature Coefficients

1973 ◽  
Vol 51 (18) ◽  
pp. 3152-3155 ◽  
Author(s):  
Huw O. Pritchard
Keyword(s):  
Low Temperature ◽  
Temperature Coefficient ◽  
Rate Constants ◽  
Recombination Rate ◽  
Negative Temperature Coefficient ◽  
Negative Temperature ◽  
Equilibrium Form ◽  
Temperature Coefficients ◽  
Recombination Rate Constant ◽  
Arrhenius Temperature

It is shown that previously calculated nonequilibrium rate constants for the dissociation of H2 and D2 appear to approach a rotationally averaged equilibrium expression at low temperature. This equilibrium form of the rate expression itself has an Arrhenius temperature coefficient for dissociation which is significantly less than the dissociation energy, and the corresponding recombination rate constant has a negative temperature coefficient. The reasons for this are explained.

scholarly journals The Effect of Storage-Induced Changes in Ammonia Borane on Hydrogen Release during Its Low-Temperature Thermolysis

Inorganics ◽  
2019 ◽  
Vol 7 (8) ◽  
pp. 96 ◽  
Author(s):  
Oxana V. Komova ◽  
Olga V. Netskina ◽  
Anna M. Ozerova ◽  
Galina V. Odegova ◽  
Sergei S. Arzumanov ◽  
...  
Keyword(s):  
Thermal Analysis ◽  
Low Temperature ◽  
Ammonia Borane ◽  
Analysis Data ◽  
Magic Angle Spinning ◽  
Attenuated Total Reflection ◽  
Hydrogen Release ◽  
Magic Angle ◽  
Apparent Activation Energies ◽  
Angle Spinning

In this paper, low-temperature solid-state processes of the dehydrogenation of ammonia borane (NH3BH3, AB) samples of different purity are compared under the conditions of isothermal heating at 100 °C, as well as in the course of thermal analysis which was also carried out at different rates of heating. The composition of boron-containing impurities was studied by attenuated total reflection Fourier transform infrared spectroscopy (ATR FTIR) and 11B magic angle spinning nuclear magnetic resonance (11B MAS NMR). Accumulation in AB of three- and four-coordinated borate anions upon contact of hydride with air moisture is established. The apparent activation energies were calculated from thermal analysis data, and found to decrease from 174 to 163 kJ/mol as the AB purity decreased from 93% to 79%. This showed itself in a shortening of the induction period during the AB thermolysis under isothermal conditions. The prospects of using the thermal analysis for estimating NH3BH3 reactivity are discussed.

Structures, Dielectric Properties and Luminescence Properties of Nb Doped Li2TiO3 Solid Solution Ceramics

2017 ◽  
Vol 748 ◽  
pp. 137-142 ◽  
Author(s):  
Fei Wang ◽  
Chun Feng Yao ◽  
Qun Zeng ◽  
He Zhou ◽  
Zhi Yong Zhou
Keyword(s):  
Solid Solution ◽  
Dielectric Properties ◽  
Low Temperature ◽  
Solution Method ◽  
Microwave Dielectric Properties ◽  
Luminescence Properties ◽  
Monoclinic Structure ◽  
Small Temperature ◽  
Temperature Coefficients ◽  
Microwave Dielectric

In this article, the low-firing Li2+xNb3xTi1-4xO3(x = 0.01, 0.02, 0.04, 0.06) ceramics with monoclinic structure have been obtained by the traditional solid solution method and their microwave dielectric properties were investigated in detail. The ceramics were finely densified at lower temperatures around 1100 °C and demonstrated favorable dielectric performances including relatively low permittivities (εr) ranging from 19 to 24, high Q×f values up to 60,000 GHz (fres = 7.89GHz) and small temperature coefficients of the resonate frequency (for x = 0.02, τf = 10.4 ppm/ °C; x = 0.06, τf = -11.5 ppm/ °C). Furthermore, the ceramics could be densified at around 900°C with adding low-amount of B2O3. Especially, the 1wt.% B2O3-doped Li2+xNb3xTi1-4xO3 (x = 0.06) ceramics was sintered well-densified at 900°C and presented good microwave dielectric properties with εr ∼ 22.2, Q×f ∼ 44,000 GHz. In addition, these ceramics have luminescence properties, which indicated that the ceramics would be applied in LTCC and/or luminescence applications as new luminescence LTCC (low temperature co-fired ceramics) materials.

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