Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Patent
1984-09-11
1985-11-12
Lee, Lester L.
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
525436, 528179, 528182, 528185, 528352, 528353, C08G 7310
Patent
active
045529310
ABSTRACT:
A process of endcapping a polyimide system with an endcapping agent in order to achieve a controlled decrease in molecular weight and melt viscosity along with predictable fracture resistance of the molded products is disclosed. The uncapped system is formed by combining an equimolar ratio of 4,4'-bis(3,4-dicarboxyphenoxy) diphenylsulfide dianhydride (BDSDA) and 1,3-bis(aminophenoxy)benzene (APB) dissolved in bis(2-methoxyethyl)ether. The endcapped system is formed by dissolving APB in bis-(2-methoxyethyl)ether, adding the endcapping agent, and then adding the BDSDA. By varying the amount of endcapping from 0 to 4%, molecular weight is decreased from 13,900 to 8660. At a processing temperature of 250.degree. C., there is a linear relationship between molecular weight and viscosity, with the viscosity decreasing by two orders of magnitude as the molecular weight decreased from 13,900 to 8660. A greater drop in viscosity is noted at higher temperatures. Apparent viscosity as a function of molecular weight at 250.degree. C. and at 280.degree. C. is depicted in FIG. 2. Reducing the molecular weight also results in a linear decrease in the fracture resistance from 4100 J/m.sup.2 to 296 J/m.sup.2, as shown in FIG. 1.
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Burks Harold D.
St. Clair Terry L.
Lee Lester L.
Manning John R.
Nelson Wallace J.
Osborn Howard J.
The United States of America as represented by the Administrator
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