Rapid visual and simple quantitative tests indicate the degree of cure of particular epoxy resin binders in prepreg stock. It is possible that these tests may be extended to a number of different epoxy formulations

Ladaki, M.

Nigh, W. G.

English

NASA Technical Reports Server

February 1968	 1	 1 Brief 68-10043 
NASA TECH BRIEF	
-I& 
NASA Tech Briefs are issued to summarize specific innovations derived from the U.S. space program, 
to encourage their commercial application. Copies are available to the public at 15 cents each 
from the Clearinghouse for Federal Scientific and Technical Information, Springfield, Virginia 22151. 
Cure of Epoxy Resins Determined by Simple Tests 
A rapid visual test and a simple quantitative test 
have been devised to give indications of the degree of 
cure of particular epoxy resin binders in prepreg stock 
(sheets of fabric impregnated with a resin in a partially 
cured condition, known as the B stage). Stacked layers 
of the prepreg sheets are normally formed into lami-
nates (such as for printed circuit boards) under con-
trolled pressure, temperature, and time to ensure proper 
bonding between the individual prepreg sheets. If the 
cure of the stock prepreg material is in an advanced 
(overcured) stage, it will not be possible to obtain 
satisfactory bonding. 
Visual (Qualitative) Test. Samples of the prepreg 
material, approximately I inch square, are immersed 
in an aqueous morpholine solution at room tempera-
ture for 5 minutes. The samples are then rinsed in 
clear water and inspected visually. 
Normal prepreg samples (representing particular 
epoxy compositions) exhibited a milky white appear-
ance: highly overcured prepreg material remained 
almost clear. A definite gradation of cloudiness cor-
responding to the degree of overcure was observed 
between these two extremes. 
Quantitative Test. Small weighed samples of the 
prepreg material (representing specific epoxy composi-
tions) are extracted with reagent grade acetone at
room temperature, air dried at the same temperature, 
and reweighed. The weight loss calculated on a resin 
content basis was found to decrease in a consistent 
and repeatable manner as the degree of cure increased 
for the particular samples evaluated. 
Notes: 
I. It is possible that these tests may be extended to a 
number of different epoxy formulations. In some 
cases, solvents other than acetone may be required 
for the quantitative test. 
2. Details concerning these tests may be obtained 
from:
Technology Utilization Officer 
Marshall Space Flight Center 
Huntsville, Alabama 35812 
Reference: B68-10043 
Patent status: 
No patent action is contemplated by NASA. 
Source: M. Ladaki and W. G. Nigh 
of North American Aviation, Inc. 
under contract to 
Marshall Space Flight Center 
(MFS-13131 & 13132) 
Category 03 
This document was prepared under the sponsorship of the National 
Aeronautics and Space Administration. Neither the United States 
Government nor any person acting on behalf of the United States
Government assumes any liability resulting from the use of the 
information contained in this document, or warrants that such use 
will be free from privately owned rights.
https://ntrs.nasa.gov/search.jsp?R=19680000043 2020-03-12T05:46:34+00:00Z


Cure of epoxy resins determined by simple tests

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