1. Chemical Structure 

- Para-aramid: The polymer chains have para-linked benzene rings (positions 1 and 4), resulting in a highly linear and rigid structure.  

- Meta-aramid: The polymer chains have meta-linkedbenzene rings (positions 1 and 3), leading to a more flexible and branched structure.  

2. Mechanical Properties

- Para-aramid:  

 - Extremely high tensile strength (stronger than steel by weight).  

 - High modulus (stiffness).  

 - Excellent impact and cut resistance.  

- Meta-aramid:  

 - Lower tensile strength compared to para-aramid.  

 - More flexible and softer.  

 - Better drape and comfort in fabrics.  

3. Thermal & Flame Resistance

- Para-aramid:  

 - High resistance to heat (~500°C decomposition), but may char at extreme temperatures.  

 - Does not melt but degrades at very high temps.  

- Meta-aramid:  

 - Superior flame resistance—self-extinguishing when exposed to fire.  

 - Forms a protective char layer, maintaining insulation.  

 - Commonly used in firefighting gear and thermal insulation.  

4. Applications

- Para-aramid (Kevlar, Twaron):  

 - Bulletproof vests, armor, helmets.  

 - High-strength ropes, cables, and composites (e.g., aerospace).  

 - Reinforced tires (e.g., racing tires).  

- Meta-aramid (Nomex, Teijinconex):  

 - Fire-resistant clothing (firefighters, military, racing suits).  

 - Electrical insulation (e.g., transformer insulation).  

 - Heat-resistant filters and protective gear.  

5. Chemical & Environmental Resistance

- Para-aramid:  

 - Resistant to most organic solvents but degrades in strong acids/bases.  

 - Sensitive to UV degradation (requires coatings for outdoor use).  

- Meta-aramid:  

 - Better resistance to acids and chemicals.  

 - More resistant to UV and long-term environmental exposure.  

Summary

| Property         | Para-aramid (Kevlar) | Meta-aramid(Nomex) |  

|-------------------|-------------------------|------------------------|  

|Linkage     | Para (1,4)              | Meta (1,3)             |  

| Strength     | Very high               | Moderate               |  

| Flexibility    | Rigid                     | Flexible               |  

|Flame Resistance | Good, but chars     | Excellent, self-extinguishing |  

| Main Uses          | Armor, composites      | Fireproof clothing, insulation |