Post on 22-Dec-2015
Aromatic Polyamides“Aramids”
Beth NeilsonCH 392N
February 19, 2009
Outline
• Definition / Invention
• Preparation
• Physical properties
• Fiber spinning
• Applications
• Federal Trade Commission definition for aramid fiber: A manufactured fiber in which the fiber-forming substance is a long-chain synthetic polyamide in which at least 85% of the amide (-CO-NH-) linkages are attached directly between two aromatic rings
• Invention– DuPont – Morgan, Kwolek et. al.– Japan, Netherlands
ArHN C
O
Ar* *n
Aramids
C
O
H2N R
Amide Aromatic Aromatic polyamide
• Homopolymer repeat units:
• AB homopolymers – Type 3
• AABB homopolymers – Types 1 and 2
• Copolymers
HN Ar
HN Ar CC
O
HN Ar C
1 2 3
O O
Chemical Structure
Yang, H. H. Aromatic High-Strength Fibers, Wiley: New York, 1989.
ArHN C Ar* *
n
O
• Aromatic units
NN
O N
X
N
Chemical Structure
Backbone:X
X= Alkyl, Aryl, Halogen,Alkoxy, Cyano, Acetyl, Nitro
HN X
HN
X = ether, sulfide, sulfone, ketone, amine,isopropylidine, ethylene, fumaryl, azo
Pendent Groups:
Bridging Units:
Yang, H. H. Aromatic High-Strength Fibers, Wiley: New York, 1989.
• AB Homopolymers
Ar C
O
XCX
O
H2N Arn NH2 + n
HN Ar
HN C* Ar C *
O O
nA A B B
HX +
• AABB Homopolymers
– Polycondensation of diacid halides with diamines
• Solution polycondensation
• Interfacial polycondensation
• Melt or vapor phase polymerization
Preparation
Lin, J.; Sherrington, J. C. Adv. Polym. Sci. 1994, 111, 177.
H2N Ar C
O
Xn *HN Ar C
O
*n
+ HX
A B
Ar C ClCCl
O
H2N Arn NH2 + n
HN Ar
HN C* Ar C *
O O
nA A B B
HCl +O
• Diamine and diacid chloride – DuPont– Low temperature
– Monomer purity and concentration
– Amide solvent (NMP, HMPA, DMA)
N CH3
O
DimethylacetamideN-methylpyrrolidone Hexamethylphosphoramide
N
O
P
O
N
N
NCH3
CH3
CH3H3C
H3C
H3C
H3C
CH3
Solution Polycondensation
Lin, J.; Sherrington, J. C. Adv. Polym. Sci. 1994, 111, 177.
• Poly(m-phenylene isophthalamide) Nomex®
• Kwolek, S. L.; Morgan, P. W.; Sorenson, R. W. U.S. Patent 1 199 458, November 13, 1962.
• DuPont, 1967
HN
HN C C **
O O
n
+
H2N NH2
Cl Cl
O O
Amide Solvent
Solution Polycondensation
• Poly(p-phenylene terephthalamide) (PPTA) Kevlar®
• DuPont – Bair, Blades, Morgan, Kwolek
• AKZO – Leo Vollbracht, Twaron®
Solution Polycondensation
Kwolek, S. L. U.S. Patent 3 819 587, 1974.Blades, H. U.S. Patent 3 869 429, 1975.Bair, T. I.; Morgan, P. W. U.S. Patent 3 673 143, 1972.
NH2H2N +
HN
HN* C
O
C
O
*n
HMPA/NMP2:1
-15o CLiCl or CaCl2
Cl
Cl
O
O
• Higashi synthesis - phosphorus-containing activating agent
Ar CP(OPh)3 /
N
NMP/LiClO Ar CP
N
Ar'O OAr'
H P H
N
OAr'Ar'O
OAr'
H2N Ar' NH2
C Ar*
O
CHN
O
Ar'HN *n
+ HO P(OAr')222 Ar'OH +
OAr'
C OHHO
O O
C
O
O
O
Advantages:• Eliminates acid chloride
starting material• Can tune reactivity by
changing Ar’
Solution Polycondensation
Lin, J.; Sherrington, J. C. Adv. Polym. Sci. 1994, 111, 177.Odian, G. Principles of Polymerization, 4th Ed. Wiley: New York, 2004.
• Silylated diamine with diacid chloride
H2N Ar NH2
Me3SiClAr NN
Ar'(COCl)2
HN Ar*
HN C
O
Ar' C *
O
n
H SiMe3
HMe3Si
Me3SiCl +
•Increases reactivity of aromatic diamine•Faster reaction
•Elimination of Me3SiCl rather than HCl
•Higher molecular weight
Solution Polycondensation
Lin, J.; Sherrington, J. C. Adv. Polym. Sci. 1994, 111, 177.
• Copolymers– Copolymerization of three or more aromatic diamines
and diacid halides.
– Improved solubility, thermal properties, fiber properties
– Technora®
Solution Polycondensation
HN
HN* C
O
C
O
*HN O
HN
m n
• Preparation of AABB homopolymers, copolymers
• Aromatic diamine with diacid halide
• High molecular weight– Low temperature
– Monomer stoichiometry, purity, concentration
– Solvent
– Salt concentration
– Monomer structure (silylated amines)
– Reagents (triarylphosphites, pyridine)
Solution Polycondensation Summary
• High thermal stability (Td ≥ 400°C)
• High tenacity (tensile strength)• Chemical resistance • Unique solution properties
– Low solubility– Liquid crystallinity in p-aramids due to chain rigidity
• Structure dependent– Meta vs. para linkages– Structure of aromatic backbone
Physical Properties
Yang, H. H. Aromatic High-Strength Fibers, Wiley: New York, 1989.Hearle, J. S. High Performance Fibers, Woodhead Publishing Limited: Cambridge, 2001.
• Liquid crystal – substance that has properties of both a solid and a liquid– Thermotropic – phase transition occurs with
temperature change
– Lyotropic • Liquid crystallinity occurs only in solution• Varies as a function of polymer concentration and
temperature
Liquid Crystallinity
Odian, G. Principles of Polymerization, 4th Ed. Wiley: New York, 2004.
• In solution of proper concentration, liquid crystalline domains form, in which there is a high degree of order of the solute molecules. – Para linkages result in rod-like extended chain structure.
– Hydrogen bonding
• Crystallization from liquid crystal solutions results in polymers with highly ordered extended-chain morphology
• Gives rise to polymers with higher strength and modulus
Liquid Crystallinity of p-Aramids
Odian, G. Principles of Polymerization, 4th Ed. Wiley: New York, 2004.
Dry-jet Wet Spinning
• Spinning Solution– 10-20 wt% polymer
– 100% H2SO4 (H2O free)
• Elongation aligns crystalline domains
• Precipitates out of coagulation bath
• Crystallinity of solution is translated to fiber
Aramid Fiber Spinning
Hearle, J. S. High Performance Fibers, Woodhead Publishing Limited: Cambridge, 2001.
• Tenacity and Modulus
– Spinning and drawing conditions
• Wet vs. dry
• Heat treatment
– Polymer composition
– Molecular weight
Properties of Aramid Fibers
Yang, H. H. Aromatic High-Strength Fibers, Wiley: New York, 1989.
Kevlar®HN
HN* C
O
C
O
*n
http://en.wikipedia.org/wiki/Aramid#Major_industrial_uses
Applications of Aramids
HN
C
O
C*
HN
O
* n
Nomex® Technora®
HN
HN* C
O
C
O
*HN O
HN
m n
Applications of Aramids
Applications of Aramids
Hearle, J. S. High Performance Fibers, Woodhead Publishing Limited: Cambridge, 2001.