Different between Polyester and Lylon?!

ok, due to the work limit, I will explain as simple as possible.
(if you have any problems, send the questions through e-mail)

1. Polyester and Nylon are polymers. They are manufactured through condenstaion polymerization.

Polyester is formed by mixing a diol and a dicarboxylic acid. eg,
Terylene, a polyester which is made by benzene-1,2-dicarboxylic acid and enthane-1,2-diol. (monomers)

(n+1) R(OH)2 + n R´(COOH)2 ---> HO[ROOCR´COO]nROH + 2n H2O
R=CH2CH2 R'=CH2CH2CH2CH2
water is produced after the polymerization.

Nylon is formed normally by mixing a diamine and a dicarboxylic acid.
(or Diamine and acyl halide) eg. Nylon-6,6, a polymer made by hexane-1,6-diamine and hexanedioic acid. (monomers)

n HOOC(CH2)4COOH + n H2N(CH2)6NH2 ==
[-CO(CH2)4CONH(CH2)6NH-]n + nH2O

n ClOC(CH2)4COCl + n H2N(CH2)6NH2 ==
[-CO(CH2)4CONH(CH2)6NH-]n + nHCl

Chemical properties.

(1) Insulators of electricity.
Nylon and Polyester are insulator of electricity. Because they haven't any
available pi electrons for conducting electricity. Also, they do not contain
any charges under standard condition.

(2) Strength
Compare with Nylon, Polyester has relatively lower tensile strength.
Because the chain of Polyester is non-polar, even though there are some
polarized CO double bonds, they cannot interact with each other by means
of hydrogen bond. In Nylon, the N-H bonds in diamine and CO bonds in
dicarboxylic acids are polar. they can interact with each other in different chains. Therfore, Nylon can form hydrogen bonds between different chains.
Since polyester chains can only attract each other by weak van der waals' force. Therefore, the strength of Nylon is stronger due to the presence of hydrogen bond.

2008-05-30 17:25:28 補充：
(3) Ductility and Meleability
Since Nylon chains hold together by means of hydrogen bonds, so Nylon is
relatively stronger than Polyester. Therefore, Nylon becomes less ductile than
Polyester due to the difference in Bonding.

2008-05-30 17:25:46 補充：
(4) Melting and Boiling points
Nylon has higher melting and Boiling point because intermolecular hydrogen
bonds are hold between different chains. Compare with polyester, which
hold by weak intermolecular force only, Nylon requires more energy to
decompose the bonding of Nylon.

2008-05-30 17:26:16 補充：
(5) Chemical stability.
Nylon will decompose
automatically under the acidic and alkaline medium. Because nylon contains amide lingkage respectively, it undergoes alkaline hydrolysis and acidic hydrolysis.

[-CO(CH2)4CONH(CH2)6NH-]n + nH3O+ == n HOOC(CH2)4COOH + n +H3N(CH2)6NH3+

2008-05-30 17:26:21 補充：
[-CO(CH2)4CONH(CH2)6NH-]n + nOH- == n -OOC(CH2)4COO- + n H2N(CH2)6NH2