ISSN:
0022-3832
Schlagwort(e):
Chemistry
;
Polymer and Materials Science
Quelle:
Wiley InterScience Backfile Collection 1832-2000
Thema:
Chemie und Pharmazie
,
Physik
Notizen:
When the acetate groups of polyvinyl acetate are removed and subsequently restored, the viscosity of the polymer is usually decreased. It is found that after such processing, vinyl acetate polymers prepared at a given temperature approach a maximum viscosity regardless of the viscosity of the original resins. This maximum is increased by lowering the temperature of polymerization and is different for other vinyl esters. The extent of degradation is negligible at low conversions. It is concluded that this phenomenon is characteristic of the monomer. The chemical bond responsible for the degradation has many of the properties of ester linkages. The resins degrade with both bases and acids although the latter catalyst sometimes requires the presence of water. They also degrade when heated in a solution of pyridine, acetic acid and acetic anhydride. The extent of degradation closely parallels the degree of hydrolysis. It is suggested that these ester linkages are formed during polymerization as a result of transfer with the carbon-hydrogen bonds of the acetate groups of both monomer and polymer. Evidence of another transfer reaction involving the vinyl group, but having no bearing on the degradation, is also advanced. If polyvinyl acetate is alcoholized with an acid catalyst, in the absence of water, the processed resin may have a higher viscosity than would be the case with an alkaline catalyst. How much higher is governed by the type of initiator used in the polymerization. This suggests that polymer molecules may be united under these conditions, but the nature of the reaction is obscure.
Zusätzliches Material:
2 Ill.
Materialart:
Digitale Medien
URL:
http://dx.doi.org/10.1002/pol.1952.120080405
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