Title

Damping Properties Of Aliphatic Polyurethanes From 4,4'-Dicyclohexylmethane Diisocyanate

Report Number

WL-TR-91-3078 Volume III, p. GDF-1 thru GDF-12

Creator

Lee, John D.

Lee, Gilbert F.

Hartmann, Bruce

Corporate Author

Nonmetallic Materials Branch, Code R31, Naval surface Warfare Center

Date

1991

Date Issued

1991-08

Extent

12

Identifier

ADA241313

Format

1 online resource

Abstract

Polyurethanes cover a wide range of damping properties
depending in large part on their two-phase morphology. Hard segment crystallinity was proposed to be the dominant factor in determining these properties. The evidence for this conjecture came from a comparison of a system in which hard segment crystallinity was present with a system where crystallinity was inhibited by using a different chain extender. To verify our assumption, in this work crystallinity was inhibited not by changing the chain extender but by changing the diisocyanate from the aromatic 4,4'-diphenylmethane diisocyanate or MDI to the cycloaliphatic 4,4'-dicyclohexylmethane diisocyanate or H12MDI. Prepolymers of poly{tetramethylene ether glycol) {PTMG) of four different molecular weights {650, 1000, 2000, 2900) with H12MDI were synthesized and chain extended with 1,4 butanediol. Measurements of the dynamic mechanical properties of these materials verified the assumption that hard segment crystallinity is the dominant factor in determining the damping characteristics of polyurethanes. All non-crystalline hard segment systems have very similar properties regardless of the diisocyanate type or the chain extender type.

Description

Polyurethanes cover a wide range of damping properties
depending in large part on their two-phase morphology. Hard segment crystallinity was proposed to be the dominant factor in determining these properties. The evidence for this conjecture came from a comparison of a system in which hard segment crystallinity was present with a system where crystallinity was inhibited by using a different chain extender. To verify our assumption, in this work crystallinity was inhibited not by changing the chain extender but by changing the diisocyanate from the aromatic 4,4'-diphenylmethane diisocyanate or MDI to the cycloaliphatic 4,4'-dicyclohexylmethane diisocyanate or H12MDI. Prepolymers of poly{tetramethylene ether glycol) {PTMG) of four different molecular weights {650, 1000, 2000, 2900) with H12MDI were synthesized and chain extended with 1,4 butanediol. Measurements of the dynamic mechanical properties of these materials verified the assumption that hard segment crystallinity is the dominant factor in determining the damping characteristics of polyurethanes. All non-crystalline hard segment systems have very similar properties regardless of the diisocyanate type or the chain extender type.

Distribution Classification

1

Distribution Conflict

No

DTIC Record Exists

No

Illinois Tech Related

No

Photo Quality

Not Needed

Report Availability

Full text available

Type

article

Is Part Of

Proceedings of Damping '91: 13-15 February 1991 San Diego, California (GCA-1 through JCB-17)