Poly(ethylene terephthalate) terpolyesters containing isophthalic and 5‐tert‐butylisophthalic units

Abstract

Poly(ethylene terephthalate-co-isophthalate-co-5-tert-butylisophthalate) (PETI t BI) terpolymers were investigated with reference to poly(ethylene terephthalate) (PET) homopolymer and poly(ethylene terephthalate-co-isophthalate) (PETI) copolymers. Three series of PETI t BI terpolyesters, characterized by terephthalate contents of 90, 80, and 60 mol %, respectively, with different isophthalate/5-tert-butylisophthalate molar ratios, were prepared from ethylene glycol and mixtures of dimethyl terephthalate, dimethyl isophthalate, and 5-tert-butylisophthalic acid. The composition of the terpolymers and the composition of the feed agreed. All terpolymers had a random microstructure and number-average molecular weights ranging from 10,000 to 20,000. The PETI t BI terpolyesters displayed a higher glass-transition temperature and a lower melting temperature than the PETI copolymers having the same content of terephthalic units. Thermal stability appeared essentially unchanged upon the incorporation of the 5-tert-butylisophthalic units. The PETI t BIs were crystalline for terephthalate contents higher than 80 mol %, and they crystallized at lower rates than PETI. The crystal structure of the crystalline terpolymers was the same as that of PET with the 1,3-phenylene units being excluded from the crystalline phase. Incorporation of isophthalate comonomers barely affected the tensile modulus and strength of PET, but the brittleness of the terpolymers decreased for higher contents in 5-tert-butylisophthalic units.

Poly(ethylene terephthalate) copolymers that contain 5‐tert‐butylisophthalic acid and 1‐3/1‐4‐cyclohexanedimethanol: Synthesis, characterization, and properties

“…Because the content of t BI in the copolymer was <20% in this work and the T g of poly(ethylene 5tert-butylisophthalate) was reported about 998C only, the contribution of t BI units for increasing T g of the final copolymer was limited. [16][17][18] However, when the polyester contained 10 mol % t BI, the T g of the polyester was 3-48C higher than that of the polyester without added t BI. Such a change in the T g with copolymerization is exactly the same as that observed for PET copolymers that contain t BI units.…”

“…[9][10][11][12][13][14][15] This trend is reversed, however, when the isophthalic units are replaced by t BI units. [16][17][18][19] The variation of the T g with the content of t BI unit along the five series (CHDM contents ¼ 0, 5, 10, 15, and 20%) is compared in Table I, revealing that a nearly linear trend is followed in every case. DSC analysis revealed that the T g increased slightly and steadily along the series with the content of t BI units.…”

“…The utilization of isophthalic acid with bulky side groups that enhance chain stiffness is considered to be a valuable alternative. [16][17][18][19] Thus, enhancement of T g of a wide variety of polycondensates, including polyamides and polyesters, by 5-tert-butylisophthalic units ( t BI) has been reported. 8,9 Furthermore, a series of PETrelated copolyesters prepared from ethylene glycol, terephthalic acid, and 5-tert-butylisophthalic acid has been claimed to exhibit a reduced tendency to crystallize and to have a higher T g than PET.…”

Synthesis and Thermal Properties of Liquid Crystalline Thermoset containing Rigid-Rod Epoxy

“…However, it could not be explained by crystalline versus amorphous phase differences because the homopolymer of PET used had a 50 2 C higher thermal stability than the PENT homopolymer [25]. Furthermore, the direct comparison of thermal stability of amorphous poly (ether ether ketone) (PEEK) and semi-crystalline PEEK with 33% crystallinity results revealed no difference in degradation temperature (500 2 C for both) even though tensile modulus and other physical properties 94 S. H. CHO ET AL.…”

Poly(ethylene isophthalate)s: effect of the tert-butyl substituent on structure and properties

“…This work evidenced the strong repressing influence of the 5-tert-butyl isophthalate units on the 'crystallizability' of PET, and showed that the T g of the copolymer increased with the content of these units in the copolymer. PET terpolymers containing both isophthalate and 5-tert-butyl isophthalate units were also investigated and found to have intermediate properties, which could be tuned by adjusting the terpolymer composition [7].…”