May 22 2003
Background
Polyaramid Polymetaphenylene Isopthalamide or Nomex ® is an infusible, wholly aromatic polymer that can strictly be described as nylon I,I - but rarely is. Manufactured only as a fibre (by solution spinning), it has a very high thermal stability and temperature and flame resistance. In contrast to its chemical isomer Kevlar®, the tensile properties of Polyaramid Polymetaphenylene Isopthalamide or Nomex ® are similar to those of normal textile fibres but its hydrolysis resistance in hot wet conditions is better (than Kevlar’s). Its radiation resistance is also very good.
Forms
The Polyaramid Polymetaphenylene Isopthalamide or Nomex ® fibre is converted into a number of fibre-based forms, including : calendered and uncalendered papers, pressboards of three different densities and honeycomb. The last is made from Nomex® paper coated in a phenolic resin. Other forms include felts.
Applications
Applications of Polyaramid Polymetaphenylene Isopthalamide or Nomex ® include protective clothing (e.g. for firefighters and racing drivers), process equipment and insulation and filtration media.
Polyaramid is quite extensively used in composites, which are lighter than those based on carbon fiber and electrical insulation.
Its mechanical properties are mostly inferior; more precisely it has a high specific tensile strength close to that of carbon fiber composites, but relatively low strength in compression.
Nomax is used in protective clothing e.g. firefighters uniform Image Credit: ShutterStock: mat277
Explanation of Type Numbers
| . |
. |
| T410 |
Calendered Paper |
| T411 |
Un-calendered Paper |
| T418 |
Calendered Paper, containing 50% mica |
| T992 |
Low Density Pressboard |
| T993 |
Medium Density Pressboard |
| T994 |
High Density Pressboard |
Key Properties
The key properties of Polyaramid Polymetaphenylene Isopthalamide or Nomex ® are tabulated below.
Table 1. Key properties
| Chemical Resistance |
| Acids - concentrated |
Fair |
| Acids - dilute |
Good |
| Alcohols |
Good |
| Alkalis |
Fair - Good |
| Aromatic hydrocarbons |
Good |
| Greases and Oils |
Good |
| Ketones |
Good |
| Physical Properties |
| Density ( g.cm-3 ) |
1.38 |
| Limiting oxygen index ( % ) |
29 |
| Radiation resistance - Alpha |
Good |
| Water absorption - equilibrium ( % ) |
9 |
| Thermal Properties |
| Coefficient of thermal expansion ( x10-6 K-1 ) |
20 |
| Specific heat ( J.K-1.kg-1 ) |
1200 |
| Thermal conductivity ( W m-1 K-1 ) |
0.13 @ 23 |
| Upper working temperature ( °C ) |
200 - 300 |
| Properties Polyaramid Film |
| Property |
|
|
Value |
| Material |
|
|
T410 |
T411 |
T418 |
| Density |
g.cm-3 |
|
0.72-1.05 |
0.3 |
1.1 |
| Dielectric Constant @ 60 Hz |
|
|
1.6 - 3.4 |
1.2 |
2.5 |
| Dielectric Strength @ 130 µm thick |
KV.mm-1 |
|
17-55 |
9-18 |
33-63 |
| Dissipation Factor @ 60 Hz |
|
|
0.004-0.007 |
0.003 |
0.003 |
| Elmendorf Tear Strength |
N.mm-1 |
|
14-39 |
7 |
14-22 |
| Extension to break - Longitudinal |
% |
|
11-22 |
3 |
2.5 |
| Extension to break - Transverse |
% |
|
8-17 |
5 |
2.5 |
| Initial Tear Strength |
g.µm-1 |
|
12-32 |
2-4 |
6-10 |
| Limiting Oxygen Index |
% |
|
29-32 |
29 |
63 |
| Shrinkage @ 300 °C |
% |
|
0.3-2 |
|
0.2-0.3 |
| Tensile strength - Longitudinal |
MPa |
|
85-130 |
6 |
40 |
| Tensile strength - Transverse |
MPa |
|
35-75 |
3 |
30 |
| Thermal Conductivity @ 23 °C |
W.m-1.K-1 |
|
0.1-0.16 |
|
|
| Properties Polyaramid Honeycomb |
| Property |
|
Value |
| Cell Size |
mm |
6 |
5 |
3 |
5 |
| Compressive Strength |
MPa |
0.7 |
1.1 |
2.2 |
3.8 |
| Core Density |
g.cm-3 |
0.024 |
0.032 |
0.048 |
0.064 |
| Plate Shear Modulus - Longitudinal |
MPa |
25 |
34 |
52 |
70 |
| Plate Shear Modulus - Transverse |
MPa |
14 |
20 |
29 |
35 |
| Plate Shear Strength - Longitudinal |
MPa |
0.7 |
1.1 |
1.8 |
2.5 |
| Plate Shear Strength - Transverse |
MPa |
0.35 |
0.6 |
0.9 |
1.1 |
| Wall Thickness |
mm |
0.05 |
0.05 |
0.05 |
0.08 |
| Properties Polyaramid Sheet |
| Property |
|
|
Value |
| Material |
|
|
T992 |
T993 |
T994 |
| Density |
g.cm-3 |
|
0.5 |
0.83 |
1.14 |
| Dielectric Constant @ 60 Hz |
|
|
1.7 |
~3.5 |
~4.4 |
| Dielectric Strength @ 3 mm thick |
KV.mm-1 |
|
15-32 |
~33-66 |
~25-70 |
| Dissipation Factor @ 60 Hz |
|
|
0.02 |
~0.09 |
~0.02 |
| Extension to break - Longitudinal |
% |
|
3 |
5.5 |
|
| Extension to break - Transverse |
% |
|
4 |
7 |
|
| Limiting Oxygen Index |
% |
|
29 |
32 |
|
| Tensile strength - Longitudinal |
MPa |
|
14.5 |
56 |
120 |
| Tensile strength - Transverse |
MPa |
|
11 |
32 |
70 |
| Thermal Conductivity @ 23 °C |
W.m-1.K-1 |
|
0.07 |
|
|
| Properties Polyaramid Fibre |
| Property |
|
|
|
|
Value |
| Specific Modulus |
cN/tex |
|
|
|
1100 |
| Specific Tenacity |
cN/tex |
|
|
|
35 - 44 |
| Density |
g.cm-3 |
|
|
|
1.38 |
| Extension to break |
% |
|
|
|
16 - 25 |
| Properties Polyaramid Chopped Fibre |
| Property |
|
|
|
|
Value |
| Specific Modulus |
cN/tex |
|
|
|
1100 |
| Specific Tenacity |
cN/tex |
|
|
|
35 - 44 |
| Density |
g cm-3 |
|
|
|
1.38 |
| Extension to break |
% |
|
|
|
16 - 25 |
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