Polyamidien

Polyamidien, commonly referred to as polyamides, are a broad family of polymers in which amide linkages join monomer units in the main chain. The best-known examples include aliphatic polyamides such as nylon, produced by polycondensation of diamines with dicarboxylic acids or by polymerization of lactams, and aromatic polyamides (aramids) such as poly(p-phenylene terephthalamide).

Structure and synthesis: The repeating unit contains an amide bond (-CO-NH-). Production routes include step-growth polycondensation and ring-opening polymerization of lactams. Depending on monomer structure, polyamidien can be semi-crystalline or amorphous and exhibit a range of thermal and mechanical properties.

Properties: Polyamidien typically offer high tensile strength and modulus, good wear resistance, and chemical stability. They can be engineered for stiffness and high-temperature performance. Aliphatic polyamides tend to absorb moisture, which can raise glass transition temperatures and affect dimensional stability, while aromatic polyamides generally provide higher heat resistance and stiffness but may be more brittle.

Variants and examples: Nylon-6 and Nylon-66 are widely used aliphatic polyamiden. Aramids such as poly(p-phenylene terephthalamide) are known for exceptional heat resistance and impact strength. Bio-based polyamiden from renewable feedstocks (for example PA11 derived from castor oil) illustrate sustainability options.

Applications and processing: Polyamidien are used as fibers for textiles and carpets, as engineering thermoplastics in automotive, electronics, and consumer goods, and in packaging. They are processed by extrusion, injection molding, and blow molding. Drying prior to processing is often important to minimize hydrolysis and moisture-related property changes.

Environmental and sustainability: Recyclability varies by type and application. Mechanical and chemical recycling pathways exist, and life-cycle assessments are increasingly used to guide material selection and end-of-life strategies. Some polyamidien are derived from renewable resources, contributing to reduced fossil-resource reliance.