Laminate prepared from epoxy-boroxine and phenolphthalein polycarbonate has high mechanical strength at elevated temperature and is resistant to impact, fire, and high-energy thermal radiation. Polycarbonate is prepared by reaction of phenolphthalein with phosgene in presence of amine catalyst and immiscible organic solvent phase

Fohlen, G. M.

Parker, J. A.

Sawko, P. M.

English

NASA Technical Reports Server

August 1973	 B73-10341 
•	 NASA TECH BRIEF 
Ames Research Center
	
-4 
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 National Technical Information 
Service, Springfield, Virginia 22151. Requests for individual copies or questions relating to the Tech Brief program may 
be directed to the Technology Utilization Office, NASA, Code KT, Washington, D.C. 20546. 
Transparent Polymeric Laminates 
The problem: 
To develop transparent polymeric materials which 
have high mechanical strength at elevated temper-
atures and are resistant to impact, fire, and high-
energy thermal radiation. 
The solution: 
A laminate prepared from an epoxy-boroxine and 
a phenolphthalein polycarbonate. 
How it's done: 
The polycarbonate is prepared by the reaction of 
phenolphthalein with phosgene in 'the presence of an 
amine catalyst and an immiscible organic solvent 
phase. The solvent, such as methylene chloride, dis-
solves the polymer as it forms; the polymer is isolated 
from the organic solvent phase by precipitation with 
methanol or acetone. Polymers with average molec-
ular weights of 40,000 to 100,000 are obtained. 
The polymer, swollen by the addition of up to 40% 
of acetone which reduces the glass transition temper-
ature, is molded at 230°C and 7 MN/m2. The trans-
parent panels are then vacuum-dried at 150°C until 
the volatile content is as low as 2% by weight, as in-
dicated by thermogravimetric analysis. Samples pre-
pared in this manner show no tendency to undergo 
solvent crazing, and the thermal properties are little 
affected by the small amounts of retained solvent. 
Windows about 3.2 to 6.6 mm thick from this polymer 
have also been formed directly from the dry polymer 
powder by a high-speed impact press.
The epoxy-boroxine polymer is prepared from the 
diglycidyl ether of bisphenol-A (DGEBA) and about 
5 to 6.5 parts per hundred of trimethoxyboroxine 
(TMB) as catalyst. The DGEBA is brought to 40° 
—45°C, the TMB is added, and the mixture is grad-
ually degassed in a vacuum chamber. The material is 
then poured into prewarmed metal molds and heat 
cured for a specified time—temperature cycle; it is 
cooled slowly before being removed from the molds. 
Curved sheets can be obtained by bending flat poly-
mer sheets at temperatures above 150°C. 
Structural laminates are formed by bonding the 
two polymers described above with an interlayer ifim 
of ethylene-propylene-vinyl acetate terpolymer ad-
hesive; other interlayers may be useful. 
The epoxy-boroxine polymer is thermochemically 
stable to 400° C, gives a char yield of about 35%, and 
has a tensile strength of 92 MN/M2
 at 24°C. The 
phenolphthalein polycarbonate has a glass transition 
temperature of 280°C, a char yield of about 54%, and 
about four times the fuel-fire burn-through resistance 
of the conventional acrylate window. Moldings of the 
neat polycarbonate have initial tensile strengths at 
room temperature of about 110 to 138 MN/M 2
 and 
as much as 41.4 MN/M2
 at 200°C; the impact 
strength is six times that of the boroxine. By utilizing 
these two polymers in the form of a laminate, the 
composite system may provide operational capability 
at 260° C, fuel-fire resistance, and high-speed bird-
impact resistance; it may also be an effective barrier 
against high-energy -thermal radiation. 
(continued overleaf) 
This document was prepared under the sponsorship of the National 	 Government assumes any liability resulting from the use of the' 
-	 Aeronautics and Space Administration. Neither the United States 	 information contained in this document, or warrants that such use 
Government nor any person acting on behalf of the United States 	 will be free from privately owned rights.
https://ntrs.nasa.gov/search.jsp?R=19730000341 2020-03-17T07:01:43+00:00Z
Note: 
Requests for further information may be directed 
to:
Technology Utilization Officer 
Ames Research Center 
Moffett Field, California 94035 
Reference:TSP 73-10341 
Patent status: 
Inquiries concerning rights for the commercial use
of this invention should be addressed to: 
NASA Patent Counsel 
Mail Code 200-1A 
Ames Research Center 
Moffett Field, California 94035 
Source: John A. Parker, George M. Foblen, 
and Paul M. Sawko
Ames Research Center 
(ARC-10783)
is 
., 
B73-10341	 Category 04


Transparent polymeric laminates

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