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Chain extension and degradation during reactive processing of PET in the presence of triphenyl phosphite
Author(s) -
Cavalcanti F.N.,
Teófilo E.T.,
Rabello M.S.,
Silva S.M.L.
Publication year - 2007
Publication title -
polymer engineering and science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.503
H-Index - 111
eISSN - 1548-2634
pISSN - 0032-3888
DOI - 10.1002/pen.20912
Subject(s) - materials science , degradation (telecommunications) , polymer , polymer degradation , extender , ethylene , rheometer , chemical engineering , work (physics) , humidity , polymer chemistry , organic chemistry , composite material , chemistry , mechanical engineering , computer science , thermodynamics , telecommunications , catalysis , physics , rheology , polyurethane , engineering
Poly(ethylene terephthalate) (PET) is chemically degraded during processing and/or using by a number of sources including temperature, humidity, and ultraviolet radiation. As a consequence, a large loss in engineering properties is observed when PET products are recycled. To overcome this problem, various types of chain extenders were developed in an attempt to recover the polymer molecular sizes by chemical reactions during processing. This work investigates the use of triphenyl phosphite (TPP) as a chain extender of virgin and recycled PET. Compounds with 1 and 3% of TPP were prepared and processed under various conditions using a torque rheometer. An increase in torque during mixing was associated with chain extension reactions whereas the observed decrease in torque afterwards was due to chemical degradation. The optimum processing conditions were reached (260°C, 1% chain extender), with a maximum in chain extension and a minimum in subsequent degradation. An important finding of this work was that the chemical degradation of chain extended PET occurs very easily during storage and it was considered to be a result of the influence of by‐products of TPP reaction with PET. The extraction of these products with acetone was shown to be quite effective, with a considerable stability during storage. This work also showed that the recycled PET is much less able to react with TPP in comparison with the virgin polymer. POLYM. ENG. SCI., 47:2155–2163, 2007. © 2007 Society of Plastics Engineers