608Jourmal of Donghua University (Eng. Ed.) Vol, 24. No. 5 (2007)stability as expected. At first, the trimethylene moietiesphenyl and acyI is ruptured, and l, 3 - propanediolbound to the macromolecular core by ether bonds aredibenzoate (MW = 284) is formed. Secondly, the linkugeruptured cleaved. It is worth noting that the temperaturebetween alky-oxygen of ester bond and trimethylene isabove 550C，macromolecular chain of PTT drastically splitruptured, the more steady diallylterephthalate (MW = 246)out, and the small debris could be produced.could be prodluced. Thirdly, the linkage between one endFor the heterochain polyester whose backbone chainof alky-oxygen of ester bond and trimethylene are rupturedincludes non carbon atom ( oxygen atom)， the bondand the elimination takes place, monopropenyl p-phthalatebetween carbon atom and oxygen atom is weaker than the(MW = 206) is produced. Other elimination could be led tobond between carbon atom and carbon atom. Thus thea series of fragments, including benzene. The free radicalbond between carbon atom and oxygen atom is prone tosubstitutions are also known to occur in pyrolytic reaction.rupture.For the ester being heated, the linkage spliAn example of this type is the formation of biphynyl frombetween alkyl and oxygen is easier than the linkage splitbenzene. This reaction can be viewed as an oxidationbetween acyl and oxygen. During PTT pyrolysis process,because of the hydrogen elimination.PTT is peeled off, and come into being dimmer.In order to facilitate the discussion a general schemeSequentially, intermediate could be ulteriorly crackedillustrating the principal fragmentation pathways of PTT isaccording to three mode. Firstly, the linkage betweendepicted in Fig. 4.-0- -CH,- -CH,;一CH-一o- -CMW=284H,C==CH一-CH,- - 0-C一0- -CH,- -CH= =CH,C,H,O，MW=246-O- -CH,- -CH;-CH,- O- -CH,C- -CH- -CH2- -0- --C-0--CH-CH;-CH, .C;H2O,MW=456H- -0-CH,-CH,MW=2080H- -0-C- -0--CH_-CH=CH,H一-0-C-C,HO,I C,H.O,MW=206MW=] 66H- -0- -C-0- -CH,- -CH- -CH,--0-HC.H,O2C,H,O,MW=164MW=122H一-0-CC- -0- -CH.- -CH=CH2C,H.OCiH,oO2MW=162\V= 106? C.H。OXO-口<，H，MW=78MW=230MW=154Fig.4 A general scheme of fragmentation pathways for PTT中國(guó)煤化工CNMHGJoumal of Donghua University ( Eng. Ed.) Vol.24, No.5 (2007) 609propanediol dibenzoute could be adopted.3 ConclusionReferencesThe polymer network remains essentially intact until350C. Between 550C and 750C，drastic changes occur,[1 ] Pyda M, Boller A, Grebowicz J, el al. Heat Capacity ofin that the network collapses， ester bond couldPolytrimethylene Terephthalate [J]. J Polym Sci. Pt Bdestroyed and a lot of fragments could be formed. ThePolym Phys Ed, 1998, 36(14): 2499- 2511[ 2 ] Zhang Chang-ming, Zhang Hao-hong, Yang Jian-li, et al.pyrolysis mechanism contributesStudy on Depolymerisation of Poly ( Trimethylenescissions as a successive removal of the monomer units fromTerephthalate) in Supercritical Methanol by GPC - HPLC -the polymeric chain. The chain scissions are followed byIR [J]. Polymer Degradation and Stability, 2004, 86(3):the elimination reaction, linkage action and secondary461 -466.reactions, which bring about a variety of compounds.[ 3 ] Chen Yu-jun, Hou Gong. Study on Heat Degradation ofSome fragments including benzene, toluene,Poly(Trimethylene Terephthalate) [J]. Polyester Industry,dimethylbenzene, styrene, benzaldehyde, ethenylmethyl-2005，18(2): 27 - 30(in Chinese).benzene, acetophenone, benzoic acid, biphenyl, biphenyl,[ 4] Chen Ke-quan, Zhou Yan, Zhang Biao. Study on Thermaldiphenylmethane, 4 - methyl - 1， 1’ - biphenyl,Decomposition of Poly( Trimethylene Terephthalate) Resinbenzophenone, terphenyl are the common pyrolysates o[J]. Polyester Industry ,2004, 17(3); 13 - 17(in Chinese).polyester(PET, PTT and PBT).[5 ] Qian He-sheng. Thermal Decomposition of Poly ( p-In order to qualitatively identify PTT, most importantphenylene Terephthalamide ) by Pyrolysis Gas-Chromatography[J]. Synthetic Fiber, 2005, 34(11): 2,fragmentscomprising 2- propenyI benzoate,15 -18,22(in Chinese). .monopropenyl p-phthalate, diallylterephthalate and 1,3-中國(guó)煤化工MCNMHG