Zinc Oxide Crosslinking Chemistry of Halobutyl Elastomers—A Model Compound Approach

1984 ◽  
Vol 57 (2) ◽  
pp. 284-290 ◽  
Author(s):  
R. Vukov
Keyword(s):  
Molecular Weight ◽  
Zinc Oxide ◽  
Model Compound ◽  
Low Molecular Weight ◽  
Model Compounds ◽  
High Molecular Weight Product ◽  
Crosslinking Process ◽  
Carbon Carbon Bond ◽  
Crosslinking Reactions ◽  
Molecular Weight Product

Abstract The study of the crosslinking reactions of halobutyl rubbers with zinc oxide, conducted on low molecular weight model compounds, has brought about a thorough understanding of the chemistry of this process. It has been shown that there are two competitive processes taking place, with the major one generating the catalyst for the oligomerization reaction and producing a substantial amount of a monomeric diene. The actual crosslinking process is a cationically induced oligomerization based on carbon-carbon bond formation. The major high molecular weight product is the dimeric hydrocarbon with a small amount of trimeric product also being formed. Both the direct elimination reaction and the crosslinking process lead to the formation of dienic functional groups.

A study of the structure-mesomorphism relationship in some polymers and low-molecular-weight model compounds

1990 ◽  
Vol 26 (11) ◽  
pp. 1259-1265 ◽  
Author(s):  
Joaquin Barbera ◽  
Enrique Melendez ◽  
Fernando Navarro ◽  
Jose L. Serrano
Keyword(s):  
Molecular Weight ◽  
Low Molecular Weight ◽  
Model Compounds ◽  
Weight Model

Uptake and Catabolism of 125l-Thrombin by the Rabbit Thoracic Aorta In Vitro: Permeability of the Endothelium, Intima-Media and Adventitial Layers

1984 ◽  
Vol 52 (02) ◽  
pp. 105-111 ◽  
Author(s):  
Mark W C Hatton ◽  
Sue L Moar
Keyword(s):  
Molecular Weight ◽  
Endothelial Cells ◽  
Vessel Wall ◽  
Antithrombin Iii ◽  
High Molecular Weight Product ◽  
Constant Rate ◽  
Molecular Weight Product ◽  
Media Layer ◽  
Extracellular Proteolysis

SummaryThe uptake, distribution and catabolism of 125I-thrombin has been studied in vitro using normal and ballooned (de-endothelialized) aorta segments at 37° C and at 4° C. In addition to rapid uptake by endothelial cells, 125I-thrombin passed at a slower, and yet constant, rate through the endothelium and accumulated in the intima-medial and adventitial layers. The enzyme, however, was not able to cross the adventitia. Passage through the endothelium was probably intercellular rather than due to transcytosis. Uptake by the intima-media layer of ballooned segments was substantially faster (× 2.5) than by the subendothelial (intima-media) region of normal segments. Once associated with the endothelium and the subendothelial layers, 125I-thrombin was catabolized and radioactive products, which were released from the vessel wall, appeared in the incubation medium. Two possible catabolic routes were identified: 1. the enzyme was recovered as a high molecular weight product (i. e. excluded by Sephadex G-200), due to complex formation with an extracellular vessel wall component and/or plasma antithrombin III. 2. Fragments of the enzyme were recovered which were presumably the products of limited, extracellular proteolysis.

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