Addition vs Condensation Polymerization: Key Differences Explained
Addition polymerization joins monomers by adding them across a double bond, forming one continuous chain without any by-products. Condensation polymerization builds chains by reacting monomers and kicking out small molecules like water or methanol.
People mix them up because both make “plastics,” yet the grocery bag (addition) and the compostable fork (condensation) behave differently. Spotting the tiny recycling code or sniffing for that “wet” smell from condensation polymers flips the perspective instantly.
Key Differences
Addition uses unsaturated monomers (think ethylene), produces no waste, and yields thermoplastics. Condensation needs at least two functional groups per monomer, ejects by-products, and often creates thermosets or nylons. The first is like snapping LEGO bricks; the second is welding them while dripping molten metal.
Which One Should You Choose?
Pick addition for cheap, flexible packaging like polyethylene bags. Choose condensation when you need strength, heat resistance, or biodegradability—e.g., PET bottles or medical sutures. Your application decides the chemistry.
Examples and Daily Life
HDPE milk jugs: addition. Polyester fleece jacket: condensation. Silicone phone case: condensation. PVC garden hose: addition. Memorize two items in each category and you’ll never confuse them again.
Does recycling differ between the two?
Yes. Addition polymers like HDPE melt and remold easily. Condensation polymers often need chemical recycling or degrade thermally first.
Can one plastic use both methods?
No. Each polymer is made by one route only, though blends can combine both types in the final product.