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 |
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