Rubber, vulcanized or thermoplastic. Determination of low-temperature brittleness

2015 ◽  
Keyword(s):  
Low Temperature

The experimental determination of hydromagnesite precipitation rates at 22.5–75ºC

2014 ◽  
Vol 78 (6) ◽  
pp. 1405-1416 ◽  
Author(s):  
U.-N. Berninger ◽  
G. Jordan ◽  
J. Schott ◽  
E. H. Oelkers
Keyword(s):  
Low Temperature ◽  
Experimental Determination ◽  
Closed System ◽  
Equilibrium Constants ◽  
Magnesium Silicate ◽  
Silicate Mineral ◽  
Dissolution Rates ◽  
Dissolution And Precipitation

Natural hydromagnesite (Mg5(CO3)4(OH)2·4H2O) dissolution and precipitation experiments were performed in closed-system reactors as a function of temperature from 22.5 to 75ºC and at 8.6 < pH < 10.7. The equilibrium constants for the reaction Mg5(CO3)4(OH)2·4H2O + 6H+ = 5Mg2+ + 4HCO3– + 6H2O were determined by bracketing the final fluid compositions obtained from the dissolution and precipitation experiments. The resulting constants were found to be 1033.7±0.9, 1030.5±0.5 and 1026.5±0.5 at 22.5, 50 and 75ºC, respectively. Whereas dissolution rates were too fast to be determined from the experiments, precipitation rates were slower and quantified. The resulting BET surface areanormalized hydromagnesite precipitation rates increase by a factor of ~2 with pH decreasing from 10.7 to 8.6. Measured rates are approximately two orders of magnitude faster than corresponding forsterite dissolution rates, suggesting that the overall rates of the low-temperature carbonation of olivine are controlled by the relatively sluggish dissolution of the magnesium silicate mineral.

STUDIES ON REACTIONS RELATING TO CARBOHYDRATES AND POLYSACCHARIDES.: PART XXVI. STRUCTURE OF ACETONE GLYCEROL

1930 ◽  
Vol 2 (1) ◽  
pp. 35-41 ◽  
Author(s):  
Harold Hibbert ◽  
J. G. Morazain
Keyword(s):  
Low Temperature ◽  
Methyl Ether ◽  
Neutral Medium ◽  
Satisfactory Explanation ◽  
Isopropylidene Glycerol

The condensation of acetone with glycerol has been carried out in a neutral medium, at a low temperature, and the product shown to consist entirely of the five-membered isopropylidene-glycerol ketal. Based on this fact, the use of the substance for the determination of the structure of fats is therefore warranted. Isopropylidene-glycerol and its acetate readily hydrolyse on heating with water.No satisfactory explanation can, as yet, be offered for the non-formation of the six-membered ketal under the conditions outlined.Acetone, as previously shown by other workers, is capable of forming a six-membered cyclic ketal with glycerol-β-methyl ether, dihydroxy acetone, pentaerythritol and certain carbohydrates.

3D Freeze Printing: Development of an Experimental Setup and Determination of 3D Printing Parameters

2020 ◽  
Author(s):  
Halil Tetik ◽  
Dong Lin
Keyword(s):  
3D Printing ◽  
Low Temperature ◽  
Temperature Gradient ◽  
Freeze Casting ◽  
Printing Process ◽  
Print Head ◽  
Freezing Temperatures ◽  
Fabrication Parameters ◽  
Printing Parameters

Abstract 3D freeze printing is a hybrid manufacturing method composed of freeze casting and inkjet-based printing. It is a facile method to fabricate lightweight, porous, and functional structures. Freeze casting is a well-known method for fabricating porous bodies and is capable of manipulating the micro-structure of the resulting product. Freeze casting simply involves solidification of a liquid suspension using low temperature and sublimation of the solvent using low temperature and pressure. After the sublimation of the solvent crystals, we obtain a porous structure where the pores are a replica of solvent crystal. Making use of the temperature gradient, as seen in unidirectional and bidirectional freeze casting, during the solidification with low temperature values, the solvent crystals grow along the temperature gradient. Furthermore, by manipulating the freezing kinetics during solidification, we can have a control on the average pore size distribution. For instance, when lower freezing temperatures result in finer pores with higher amount, higher freezing temperatures result in coarser pores with less amount. Also, the use of some additives inside the suspension leads to changes in the morphology of the solvent crystals as well as the resulting pores. However, the macro-structure of the fabricated body is highly dependent on the mold used during the process. In order to eliminate the dependency on the mold during the freeze casting process, our group recently combined this technique with inkjet-based 3D printing. With inkjet-based 3D printing, we fabricated uniform lines from single droplets, and complex 3D shapes from the lines. This provided us the ability of tailoring the macro structure of the final product without any dependency on a mold as seen in freeze casting. As a result of the 3D freeze printing process, we achieved fabricating lightweight, porous, and functional bodies with engineered micro and macro-structures. However, achieving fine droplets, and uniform lines by merging the droplets requires a good combination of fabrication parameters such as pressure adjustment inside the print head, print head speed, jetting frequency. Also, fabricating complex shapes from uniform lines requires well-adjusted parameters such as line thickness and layer height. In this study, we briefly explained the mechanics of the 3D freeze printing process. Following that we presented the development process of an open-source inkjet-based 3D printer. Finally, we explained the determination of inkjet dispensing and 3D printing parameters required for a high-quality 3D printing. During our experiments for the determination of fabrication parameters, we used a nanocellulose crystals-based ink due to its low cost and ease of preparation.

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