Influence of copolymeric poly(diethylene glycol) terephthalate on the thermal stability of poly(ethylene terephthalate)

Abstract

synopsisCopolymers of poly(ethy1ene terephthalate) (PET) containing 1-24% poly(diethy1ene glyco1)terephthalate (PDEGT) were prepared and characterized by infrared spectra. The energy and entropy of activation for the thermal degradation were measured for these copolymers and for the PDEGT. These activation energies and entropies were found to decrease steadily with increasing diethylene glycol content. From these measurements the mechanism of degradation of PDEGT was found to be different from that of PET. Fibers prepared from seven different copolymeric compositions were heat-aged a t 121OC and 204°C for 24 hr. From the changes observed in intrinsic viscosity, per cent ether, hydroxyl and carboxyl endgroups during heat aging it became apparent that the mechanisms for decomposition are operative below melt temperatures and can rapidly destroy such copolymers.

Poly(ethylene-co-ethyleneoxyethylene terephthalate)s: synthesis and non-isothermal crystallization behavior

“…Estimated from the measured heat of fusion against the heat of fusion (117.6 J/g) of the fully crystallized PET polymer 5) .…”

“…In conclusion, the non-isothermal crystallization in the PEOET copolyesters follows a nucleation and growth mechanism compared to those of the PET homopolymer, regardless of the DEG contents. Estimated from the measured heat of crystallization against the heat of fusion (117.6 J/g) of the fully crystallized PET polymer 5) . b)…”

“…Under that polycondensation condition, the ethyleneoxyethylene unit (1CH 2 CH 2 OCH 2 CH 2 1) is known to react with the polymer backbone because of the dimerization of the EG component which is a side reaction. Commercial grades of PET always contain 2 -4 mol-% of this ethyleneoxyethylene unit [3][4][5] . The presence of ethyleneoxyethylene units suppresses the melting point, the glass transition temperature, and the crystallization rate [6][7][8][9][10][11] .…”

Poli(tereftalato de etileno), PET: uma revisão sobre os processos de síntese, mecanismos de degradação e sua reciclagem

“…Consequentemente, uma variedade de co-monômeros são usados na síntese do PET: 1,3-propanodiol, 1,4-butanodiol, ácido isoftálico, ácido 2,6-naftalenodicarboxílico, ciclohexanodimetanol e dietileno glicol [25,27,[41][42][43][44][45] . A Figura 3 ilustra a estrutura de alguns co-polímeros do PET.…”

“…Através desta propriedade é possível reduzir a "bruma" formada durante o resfriamento das garrafas PET no processo de injeção-sopro [44,69,70] . Por outro lado, as unidades de DEG são conhecidas por induzirem a degradação térmica e termo-oxidativa do PET [2,45,69] , consequentemente, as unidades de DEG influenciam negativamente no processo de reciclagem de PET.…”