| Feature | Addition Polymerization | Condensation Polymerization |
|---|---|---|
| Monomer requirement | Unsaturated (C=C) | Bifunctional (2 reactive groups) |
| Mechanism | Chain-growth | Step-growth |
| Byproduct | None | Small molecule (H2O, HCl, etc.) |
| Product formula | Same as monomer | Different from monomer |
| MW build-up | Rapidly from start | Slowly; needs >99% conversion for high MW |
| Thermal type | Usually thermoplastic | Thermoplastic OR thermosetting |
| Key examples | HDPE, LDPE, PVC, Teflon, PS, PAN | Nylon-6,6, Nylon-6, Dacron, Bakelite, Melamine-HCHO |
| Catalyst/Initiator | Free radical, Ziegler-Natta | Acid/base catalyst |
| Chain transfer | Possible (causes branching) | Not applicable |
| Atom economy | 100% (no byproduct) | < 100% (loses H2O per bond) |
Nylon-6,6 vs Dacron Comparison:
| Feature | Nylon-6,6 | Dacron (PET) |
|---|---|---|
| Monomer 1 | Hexamethylenediamine (NCCCCCCN) | Ethylene glycol (OCCO) |
| Monomer 2 | Adipic acid (OC(=O)CCCCC(=O)O) | Terephthalic acid (OC(=O)c1ccc(C(=O)O)cc1) |
| Linkage | Amide (–CO–NH–) | Ester (–COO–) |
| Polymer type | Polyamide | Polyester |
| Uses | Fibers, tire cords, fabrics | Clothing fibers, plastic bottles |
| Thermal | Thermoplastic | Thermoplastic |