Procedure for preparing thin films for infrared spectrophotometric analysis involves pressing of a neat mixture of reactants between nonreactive thin polymer films with noninterfering absorption bands. Pressing is done under a pressure that gives desirable thickness. Following this process, the film sandwich is cut to accommodate the laboratory instrument

Garrard, G. G.

Houston, D. W.

English

NASA Technical Reports Server

)lymer Film 
Metal Plate 
Sample Mix 
(Reactants)
November 1970
	 Brief 70-10551 
NASA TECH BRIEF 
NASA Tech Briefs announce new technology derived from the U.S. space program. They are issued to encourage commercial 
application. Tech Briefs are available on a subscription basis from the Clearinghouse for Federal Scientific and Technical 
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be directed to the Technology Utilization Division, NASA, Code UT, Washington, D.C. 20546. 
Preparation of Thin Polymer Films for Infrared Reaction Rate Studies 
Press Plate
Diagram of Sample Preparation Setup 
A method of preparing thin films for studying 
reaction rates of polymer systems has been developed 
using infrared spectrophotometric techniques. The 
preparation procedure is similar to that applied in 
the formulation of many different composites, and 
may be modified for most general laboratory analyses 
where infrared spectrophoto metric methods are used. 
The procedure involves the pressing of a neat 
("as is") mixture of reactants between nonreactive 
thin polymer films with absorption bands that will 
not interfere with those being investigated. Prior 
methods, with the sample being on or between salt
plates or in solution, imposed limitations such as too 
great a film thickness prevented the use of strong 
absorbers; path length could not be reproduced; and 
materials in solution were influenced by the concentra-
tion. The use of controlled conditions to press viscous 
liquids between solid films to prepare sample, and 
"holder", for infrared spectrophoto metric analysis 
appears to be novel. 
One example where film thickness is important is 
in the reaction of isocyanates with polyols. Sample 
reactants are mixed and placed between two thin 
polymer films, as shown in the figure. Films should be 
(continued overleaf) 
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selected which are thin enough not to interfere in the 
area of the spectrum being investigated. Polyethylene 
is excellent since it does not interfere with isocyanate, 
epoxy, or carbonyl group frequencies at 4.4, 10.8, or 
5.8 microns respectively. The films are then pressed be-
tween very flat plates under a pressure that gives the 
desirable thickness and fulfills other conditions. Nor-
mally the base materials are prepolymers or have 
physical properties capable of maintaining the film. 
Following the pressing process, the film "sandwich" 
is cut to accommodate the instrument.
Note: 
No further documentation is available. Specific 
questions, however, may be directed to: 
Technology Utilization Officer 
Manned Spacecraft Center, Code BM7 
Houston, Texas 77058 
Reference: B70-10551 
Patent status: 
No patent action is contemplated by NASA. 
Source: D. W. Houston and G. G. Garrard of 
North American Rockwell Corp. 
under contract to 
Manned Spacecraft Center 
(MSC-15893)
. 
[I: 
Brief 70-10551	 Category 04


Preparation of thin polymer films for infrared reaction rate studies

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