Oligomers are prepared by heating solid ethylene-propylene rubber in container that retains solid and permits liquid product to flow out as it is formed. Molecular weight and viscosity of liquids can be predetermined by process temperature. Copolymers have low viscosity for given molecular weight

Humphrey, M. F.

Ingham, J. D.

Rhein, R. A.

English

NASA Technical Reports Server

September 1975	 B75-10207 
NASA TECH BRIEF 
NASA Pasadena Office 
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. 
Liquid Ethylene-Propylene Copolymers 
A new class of oligomers has been produced by 
thermally degrading commercially-available ethylene-
propylene rubber (EPR). It has been found that EPR 
does not melt when subjected to elevated tempera-
tures, but rather it partially degrades to liquid 
oligomers. The molecular weight and the viscosity of 
these liquids can be predetermined by the process 
temperature. 
One advantage of the oligomeric ethylene-
propylene copolymers is their low viscosity for a given 
molecular weight, as compared to analogous oligo-
meric poly(isobutylene). This makes them easier to 
use in processing. In addition, the ethylene-propylene 
copolymers contain an oiefinic unsaturation of 
approximately 2 equivalents/ mole. This feature 
facilitates their use as precursors to hydroxyl 
prepolymers capable of curing to elastomers by the 
use of standard methods. 
The new oligomers are prepared by heating solid 
EPR in a container that retains the solid and permits 
the liquid product to flow out as it is formed. In a 
typical experimental procedure, a Vycor tube 2.5 cm 
in diameter and 50 cm long is fitted in the cover of a 
500-ml resin kettle. A loose-fitting disk-shaped plug is 
held in the tube by a constriction, located about 9 cm 
from the bottom of the tube, and the tube is filled with 
borosilicate Raschig rings to approximately 13 cm 
above the disk. A condenser connects the top of the 
tube to a collecting flask. 
Small pieces of EPR are introduced into the Vycor 
tube, and a tube furnace is used to heat them to 350° 
C. A nitrogen counterflow is introduced into the resin 
kettle, up the tube, and out of the condenser. As the 
degradation proceeds, liquid oligomer is collected in
the resin kettle, solid EPR remains in the tube, and 
volatile byproducts are carried out through the 
condenser to the collecting flask. 
With an EPR sample of 210 g, the yield is 179 g 
(84.7 percent) of oligomer and 20 g of volatile 
product. Alternate experimental procedures have 
been used with temperatures up to 600° C; the best 
yield was 92.8 percent at 430° C. Oligomer molecular 
weights achieved varied from around 1,400 to 8,300, 
and unsaturation varied from 1.62 to 2.52 
equivalents/ mole, both depending upon the experi-
mental conditions. 
Note: 
Requests for further information may be directed 
to:
Technology Utilization Officer 
NASA Pasadena Office 
4800 Oak Grove Drive 
Pasadena, California 91103 
Reference: TSP75- 10207 
Patent status: 
Inquiries concerning rights for the commercial use 
of this invention should be addressed to: 
Patent Counsel 
NASA Pasadena Office 
4800 Oak Grove Drive 
Pasadena, California 91103 
Source: Robert A. Rhein, John D. Ingham,
and Marshall F. Humphrey of 
Caltech /JPL
(NPO-13555) 
Category: 04 (Materials) 
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=19750000207 2020-03-19T20:27:14+00:00Z



Liquid ethylene-propylene copolymers

Abstract

Similar works

Full text

Available Versions

NASA Technical Reports Server