Organic mechanisms Low density poly(ethene), LDPE The manufacture of low density poly(ethene) is...
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Organic mechanisms Low density poly(ethene) , LDPE • The manufacture of low density poly(ethene) is carried out at very high pressure (1000 – 3000atm) at a temperature of about 500K Ex: R – O-O – R -> 2RO free radical formation RO + H 2 C = CH 2 -> R – O – CH 2 – CH 2 propagation R – O – CH 2 – CH 2 + H 2 C = CH 2 -> R – O – CH 2 – CH 2 – CH 2 – CH 2 Termination takes places when two radical combines
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High density poly(ethene), HDPE HDPE is produced by polymerizing ethene at a low temperature ( 350K) and pressure ( 1 – 50atm) using a Ziegler – Naha catalyst. The catalyst is a suspension of titanium (iv) chloride together with an alkyl aluminium compound (Al(C 2 H 5 ) 3 ). The result of polymer consist mainly of linear chains with very little branching. This gives it a higher density 0.96gcm -3 and a more rigid structure as the chains can fit together more closely. It is used to make containers and pipes
Transcript of Organic mechanisms Low density poly(ethene), LDPE The manufacture of low density poly(ethene) is...
Organic mechanismsLow density poly(ethene) , LDPE• The manufacture of low density poly(ethene) is
carried out at very high pressure (1000 – 3000atm) at a temperature of about 500K
Ex: R – O-O – R -> 2RO free radical formationRO + H2C = CH2 -> R – O – CH2 – CH2 propagationR – O – CH2 – CH2 + H2C = CH2 -> R – O – CH2 – CH2 – CH2 – CH2
Termination takes places when two radical combines
Low density poly(ethene) , LDPE
• An average polymer molecule with about from 4 x 103 to 4 x 104 carbon atoms with many short branches which affect both degree of crystalize and density of material
High density poly(ethene) , HDPE
• HDPE is produced by polymerizing ethene at a low temperature ( 350K) and pressure ( 1 – 50atm) using a Ziegler – Naha catalyst. The catalyst is a suspension of titanium (iv) chloride together with an alkyl aluminium compound (Al(C2H5)3).
• The result of polymer consist mainly of linear chains with very little branching. This gives it a higher density 0.96gcm-3 and a more rigid structure as the chains can fit together more closely. It is used to make containers and pipes
