1st type- low density poly(ethene), (ldpe) - the chains are not organised well, so the density and strength are lowered.
2nd type - high density poly(ethene), (hdpe)
Zieglar - Natta catalysts -- catalysts where the polymer molecule grew outward from the catalyst surface.
Isotactic forms -- a polymer chain with the methyl groups in the same orientation, strong and rigid
Atactic form -- the methyl groups are arranged at random, soft and flexible
Crystalline -- the chains are closely packed in a regular way. The higher the order, the more crystalline. The stronger and less flexible the polymer is, because the polymer chains pack closer together so the intermolecular forces are greater.
Amorphous regions -- areas of polymer where crystallinity is low.