Benzothiazyl Disulfide-Accelerated Vulcanization of Carbon Black Loaded Natural Rubber

1963 ◽  
Vol 36 (3) ◽  
pp. 863-874
Author(s):  
M. L. Studebaker ◽  
L. G. Nabors
Keyword(s):  
Carbon Black ◽  
Surface Chemistry ◽  
Natural Rubber ◽  
Surface Area ◽  
Crosslink Density ◽  
Lithium Aluminum Hydride ◽  
Analytical Procedure ◽  
Aluminum Hydride ◽  
Lithium Aluminum ◽  
Mercaptan Sulfur

Abstract Sulfur group analyses of reinforced MBTS accelerated vulcanizates reveal chemical differences which can be related to the surface chemistry of the carbon blacks. The analytical procedure is based on the treatment of the vulcanizate with lithium aluminum hydride followed by potentiometric titration of sulfide and mercaptan sulfur. The polysulfide crosslink density and the values of x in the R—S—Sx—S—R polysulfides are dependent upon the quinone content of the carbon black. Both the quinone content and the surface area of a carbon black appear to determine its influence on the disappearance of free sulfur and the apparent crosslinking of the vulcanizate.

Use of Lithium Aluminum Hydride in the Study of Surface Chemistry of Carbon Black

1963 ◽  
Vol 36 (3) ◽  
pp. 729-739 ◽  
Author(s):  
D. Rivin
Keyword(s):  
Carbon Black ◽  
Surface Chemistry ◽  
Lithium Aluminum Hydride ◽  
Carbonic Acid ◽  
Surface Acidity ◽  
Sodium Bicarbonate Solution ◽  
Aluminum Hydride ◽  
Lithium Aluminum ◽  
Surface Groups ◽  
Carbon Blacks

Abstract Considerable interest has been focused in recent years on the effects of carbon black surface chemistry on its properties in rubber and other polymer systems. Methods have been developed in our laboratory for the quantitative characterization and description of the surface chemistry of carbon blacks. The total surface acidity as given by the active (acidic) hydrogen is determined by reaction with strongly basic lithium aluminum hydride in diethyl carbitol, or by equilibration with aqueous alkali under nitrogen. Exclusion of oxygen is essential since carbon blacks readily undergo base catalyzed oxidation. Selective neutralization techniques are employed to further differentiate between strong and weak surface acids. For example, using aqueous sodium bicarbonate solution, only those acids stronger than carbonic acid will be neutralized. Strong acids, as determined by bicarbonate neutralization, are shown to be aromatic carboxyl groups, while weak acids determined by difference between total acidity and strong acid content are phenols and hydroquinone derivatives. Neutral quinone and lactone surface groups are quantitatively determined by chemical reduction with lithium aluminum hydride, or alternatively by analysis of their thermal decomposition products (carbon monoxide and dioxide, hydrogen, and water) obtained on vacuum pyrolysis of carbon black. The distribution of neutral and acidic surface groups on representative channel, furnace, and thermal black is discussed in terms of the state of oxidation of the individual carbons.

Vulcanization. Part III. Rapid Methods for Characterizing Rubber Networks

1964 ◽  
Vol 37 (3) ◽  
pp. 668-672 ◽  
Author(s):  
A. Y. Coran
Keyword(s):  
Thin Films ◽  
Crosslink Density ◽  
Lithium Aluminum Hydride ◽  
Aluminum Hydride ◽  
Lithium Aluminum ◽  
Chemical Bonds ◽  
Equilibrium Swelling ◽  
Before And After ◽  
The Difference

Abstract Equilibrium swelling determinations have long beea used as a means of estimating crosslink density, usually through the Flory-Rehner equation. Most of the reported methods for determining equilibrium swelling in rubber vulcanizates have required long periods of swelling before equilibrium was reached, due to the fact that thick specimens were used. The method presented here makes use of thin films as specimens for swelling, and equilibrium can be reached in periods of one to five minutes. In addition, the use of thin films makes possible the semiquantitative determination of the types of chemical bonds responsible for the crosslinks in rubber vulcanizates. In thin films the reaction of polysulfide crosslinks with lithium aluminum hydride (in benzene-tetrahydrofuran) is rapid. The determination of crosslink density after such a reduction is indicative of only those crosslinks which are not reducible by the hydride and the difference between crosslink densities before and after the reduction is a measure of the number of crosslinks of the polysulfidic type. The work described here has been limited to natural rubber gum stocks. The methods used are undoubtedly applicable to other types of stocks, though in some instances a certain amount of modification will be required.

The Preparation of Specifically Deuterated trans- Cinnamyl Alcohol and trans- Cinnamic Acid

1973 ◽  
Vol 51 (13) ◽  
pp. 2102-2104 ◽  
Author(s):  
Donald G. Lee ◽  
James R. Brownridge
Keyword(s):  
Cinnamic Acid ◽  
Triple Bond ◽  
Lithium Aluminum Hydride ◽  
Aluminum Hydride ◽  
Lithium Aluminum ◽  
Cinnamyl Alcohol ◽  
Partial Reduction ◽  
Work Up

The reduction of ethyl phenylpropiolate by lithium aluminum hydride results in partial reduction of the triple bond to give trans-cinnamyl alcohol. If ethyl phenylpropiolate is reduced by LiAlD4 followed by work-up with acetone and H2O the product is the specifically labeled compound, trans-3-phenyl-2-propen-1-ol-1,1,2-d3. If the ester is reduced with LiAlH4 followed by work-up with acetone-d6 and D2O the product is trans-3-phenyl-2-propen-1-ol-O,3-d2. Oxidation of these two products by sodium ruthenate leads to formation of trans-cinnamic acid-α-d and trans-cinnamic acid-β-d, respectively.

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