Dimethyl Isophthalate Research Articles

Biochemical pathway and degradation of phthalate ester isomers by bacteria

Degradation of dimethyl isophthalate (DMI) and dimethyl phthalate ester (DMPE) was investigated using microorganisms isolated from mangrove sediment of Hong Kong Mai Po Nature Reserve. One enrichment culture was capable of utilizing DMI as the sole source of carbon and energy, but none of the bacteria in the enrichment culture was capable of degrading DMI alone. In co-culture of two bacteria, degradation was observed proceeding through monomethyl isophthalate (MMI) ester and isophthalic acid (IPA) before the aromatic ring opening. Using DMI as the sole carbon and energy source, Klebsiella oxytoca Sc and Methylobacterium mesophilicum Sr degraded DMI through the biochemical cooperation. The initial hydrolytic reaction of the ester bond was by K. oxytoca Sc and the next step of transformation was by M. mesophilicum Sr, and IPA was degraded by both of them. In another investigation, a novel bacterium, strain MPsc, was isolated for degradation of dimethyl phthalate ester (DMPE) also from the mangrove sediment. On the basis of phenotypic, biochemical and 16S rDNA gene sequence analyses, the strain MPsc should be considered as a new bacterium at the genus level (8% differences). This strain, together with a Rhodococcus zopfii isolated from the same mangrove sediment, was able to degrade DMPE aerobically. The consortium consisting of the two species degraded 450 mg/l DMPE within 3 days as the sole source of carbon and energy, but none of the individual species alone was able to transform DMPE. Furthermore, the biochemical degradation pathway proceeded through monomethyl phthalate (MMP), phthalic acid (PA) and then protocatechuate before aromatic ring cleavage. Our results suggest that degradation of complex organic compounds including DMI and DMPE may be carried out by several members of microorganisms working together in the natural environments.

Thermal behavior and morphology of polycaproamide (PCA)/cationic dyeable polycaproamide (CD‐PCA) polyblended filaments

AbstractPolycaproamide (PCA) polymer and cationic dyeable polycaproamide (CD‐PCA) polymer were blended mechanically in the proportions of 75/25, 50/50, and 25/75 in a melt twin‐screw extruder to prepare three PCA/CD‐PCA polyblended polymers. Blends of PCA and CD‐PCA were spun into filaments. The molar ratio of 5‐sodium sulfonate dimethyl isophthalate (5‐SSDMI) for CD‐PCA polymer was 1.99%. This study investigated the physical properties of PCA/CD‐PCA polyblended filaments using gel permeation chromatograph (GPC), nuclear magnetic resonance (NMR), gas chromatography (GC), potentiometer, thermogravimetric analysis (TGA), a rheometer, differential scanning calorimetry (DSC), the density gradient method, wide‐angle X‐ray diffraction (WAXD), extension stress‐strain measurement, and scanning electron microscope (SEM). Flow behavior of PCA/CD‐PCA polyblends exhibited positive‐deviation blends (PDB), and the 50/50 blend of PCA/CD‐PCA showed a maximum value of the melt viscosity. Experimental results of the DSC indicated PCA and CD‐PCA molecules easily formed miscible domains. The crystallinities of PCA/CD‐PCA polyblended filaments decreased as the 5‐SSDMI content increased. Tenacities/densities of PCA/CD‐PCA polyblended filaments were also found to decline as the 5‐SSDMI content increased. The surface of PCA/CD‐PCA polyblended filament exhibited a uniform morphology from the SEM data. PCA and CD‐PCA polymers were proved to be a compatible system. The weight loss percentages of the PCA/CD‐PCA polyblended filaments increased as the 5‐SSDMI content increased in aqueous NaOH solution. The porous morphology of a larger size from 0.01 to 2 μm in diameter was observed after alkali treatment of PCA/CD‐PCA polyblended filament. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 1220–1226, 2005

Synthesis and characterization of bisester-amide segments of uniform and random length

The synthesis and characterization of bisester-oligoamides segments with varying segment length that can be used in segmented block copolymers were studied. The bisester-oligoamides segments were made form diamines and terephthalate or isophthalate esters. The diamines used were p-xylylene diamine, m-xylylene diamine and hexamethylene diamine. The esters used are dimethyl terephthalate, diphenyl terephthalate, dimethyl isophthalate and diphenyl isophthalate. Uniform bisester-diamide, bisester-(tetra-amides) and bisester-(hexa-amide) segments were synthesized in steps and characterized by 1H NMR, MALDI-TOF and DSC. The uniformity of these segments was studied by MALDI-TOF. With the uniform amide segments and polypropylene oxide segments, block copolymers were prepared by high temperature melt polymerization. The amide segment length distribution, which is susceptible to randomization was studied. The analysis of the amide segment distribution after hydrolysis of the ester-linkage groups was by MALDI-TOF. The amide segments were found to have the same narrow distribution as the starting bisester-oligoamide, which strongly supports the fact that randomization of the amide segments during melt polymerization does not take place. The uniformity of the amide segments is, therefore, preserved during high temperature melt polymerization.

Study of the glycolysis of PET by oligoesters

A series of oligoesters was synthesized via the transesterification of dimethyl isophthalate with neopentyl glycol or tetraethylene glycol and the esterification of adipic acid with neopentyl glycol or tetraethylene glycol under diol/diester or diol/diacid molar ratios sufficient to limit molecular weight increasing. These oligoesters were used to depolymerize poly(ethylene terephthalate) (PET) in the presence of zinc acetate to yield new types of glycolysates. The oligoesters and the glycolysates are characterized by 1H NMR, size exclusion chromatography (SEC), differential scanning calorimetry (DSC), thermogravimetric analyses and matrix assisted laser desorption/ionisation time of flight mass spectrometry (MALDI-TOF MS). These analyses revealed the structure of the different glycolysates.

Transformation of dimethyl phthalate, dimethyl isophthalate and dimethyl terephthalate by Rhodococcus rubber Sa and modeling the processes using the modified Gompertz model

Phthalate ester isomers, including dimethyl phthalate (DMP), dimethyl isophthalate (DMI) and dimethyl terephthalate (DMT), were found to be transformed by Rhodococcus rubber Sa isolated from a mangrove sediment using DMT as a carbon source initially. At a concentration of 80 mg l(-1), transformation of DMP, DMI and DMT was achieved in 9, 1 and 5 days, respectively. During the hydrolytical transformation of DMP, DMI and DMT, their corresponding intermediates were identified as mono-methyl phthalate (MMP), mono-methyl isophthalate (MMI) and mono-methyl terephthalate (MMT), suggesting that transformation of all three isomers followed an identical biochemical pathway of de-esterification. However, none of the produced monoesters was further transformed by R. rubber Sa and they accumulated in the Culture media during incubation. It seems that further transformation of monoesters require a set of hydrolytic enzymes different from those involved in the first transformation reaction. Kinetics of DMT, DMI and DMP transformation was well described by the modified Gompertz model independent of the individual Substrate condition or a mixture of the three isomers. Both DMI and DMT were easier transformed substrates than DMP, resulting in higher maximum transformation rate (R-m) and shorter lag time phase (lambda) derived from the modified Gompertz model. The modified Gompertz model based on one-substrate system can be used in fitting transformation kinetics of mixture substrate system. Our data suggest that degradation of phthalate diesters involves different enzymes in the hydrolysis of the two identical ester groups. (c) 2005 Elsevier Ltd. All rights reserved.

Synthesis and thermal properties of randomly branched poly(butylene isophthalate) containing sodium sulfonate groups

Randomly branched poly(butylene isophthalate) samples containing sodium sulfonate groups were prepared from dimethyl isophthalate, 3,5-bis(carbomethoxycarbonyl) benzene sulfonate, tris(hydroxyethyl) isocyanurate, and 1,4-butanediol, according to the well-known two-stage polycondensation procedure. The polymers, containing various amounts of branching units and ionic groups, demonstrated to be soluble in the most common organic solvents, an evidence that gelation was not reached under the polymerization conditions adopted. The thermal behavior was examined by thermogravimetric analysis and differential scanning calorimetry. The sulfonate as well as the branching units had only a limited effect on the thermal stability, which slightly decreased with respect to pure poly(butylene isophthalate). The analysis carried out using DSC technique showed that the Tm of the copolymers decreased with increasing counit content, differently from Tg, which, on the contrary, increased. Baur's equation was found to describe well the Tm-composition data. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 1374–1379, 2006

Thermodynamics of complexation of dimethyl esters of tere-, iso-, and phthalic acids with alpha- and beta-cyclodextrins.

Thermodynamics of inclusion of alpha- and beta-cyclodextrins (CDs) with three diester precursors of polyesters, dimethyl terephthalate (DMT), dimethyl isophthalate (DMI), and dimethyl phthalate (DMP) were studied with different fluorescence spectroscopy techniques. The stoichiometry, association constants, and other thermodynamics parameters were investigated from the fluorescence intensity decrease that takes place upon CD addition and temperature changes. Apart from DMP, which did not form a complex with alphaCD, all other systems showed 1:1 stoichiometry complexes with different stabilities. The complexes formed with the DMT guest are the most stable, whereas the stability constant for DMP:betaCD is the lowest. Binding constants are also larger for complexes formed with betaCD than for those formed with alphaCD. Fluorescence polarization, quenching, and lifetime measurements provide information about the structure of the complexes formed. This geometry explains the values of enthalpy and entropy changes during complexation. Van der Waals interactions seem to be involved in the formation of these complexes.

Hydrogenation of Dicarboxylic Acid Diesters to Corresponding Dialdehydes over ZrO<sub>2</sub> Based Catalysts (Part 2) Analysis of Catalyst Surface Using Diffuse Reflectance FT-IR and CP/MAS <sup>13</sup>C-NMR Spectroscopy

The adsorption species on ZrO2 or Cr-ZrO2 catalyst in the hydrogenation of dimethyl benzenedicarboxylates as well as benzoic acid were characterized by diffuse reflectance FT-IR and CP/MAS 13C-NMR spectroscopy. Benzoic acid and dimethyl terephthalate were adsorbed as the monocarboxylate species with weak bonding to the catalyst with lower polarization at a carbonyl group similar to that of free benzoic acid. In contrast, dimethyl phthalate was adsorbed only as the dicarboxylate species. Dimethyl isophthalate was adsorbed as both mono- and dicarboxylic species. Formation of dicarboxylate adsorption species will greatly hinder the hydrogenation of dimethyl benzenedicarboxylates. In addition, the methoxycarbonyl group was more favorable for the adsorption to form the carboxylic active species than the formyl group in the interaction of Cr-ZrO2 catalyst with terephthalaldehydic acid methyl ester. A reaction mechanism for the hydrogenation is also proposed.

Wplyw chemicznej modyfikacji poli(tereftalanu butylenu) na wlasciwosci elastyczne

Poly(butylene terephthalate) (PBT) modification consisted in preparing the copolymers in which dimethyl isophthalate (DMI) and/or oligo(oxytetramethylene)diol (PTMOG) of molecular weight 1000 g/mol (Table 1) were used as modifying comonomers. DMI, disturbing the chain structure regularity, decreased the crystallinity degree of PBT, while PTMOG increased the chain flexibility. Mechanical properties (static and dynamic ones) as well as thermal properties of modified PBT were tested (Table 2). The effect of polycondensation duration on limiting viscosity number (Fig. 1) and the effect of modified PBT composition on its melting point (Fig. 2) and yield point (Fig. 3) were presented. Glass transition temperature, melting point and entalphy of melting (Fig. 4) were determined using DSC method. The effect of a temperature on dynamic properties of modified PBT (Figs. 5 and 6) was described. It was found that using of cheap and easily available comonomers let improve PBT flexibility (including impact strength). Their optimal parts in the products of modifications have been found (either 6 wt. % of DMI or a system: 6 wt. % of DMI + 6 wt. % of PTMOG or 20 wt. % of PTMOG).

Thermal and Mechanical Properties of Polyblends of Polycaprolactam with Cationic Dyeable Poly(ethylene terephthalate)

One Polycaprolactam (PCPL) polymer and three cationic dyeable poly(ethylene terephthalate) (CD-PET) polymers were blended mechanically in the proportions of 90/10, 80/20, 70/30, 60/40, 50/50, 40/60, 30/70, 20/80, 10/90 in a melt twin-screw extruder to prepare twenty-seven PCPL/CD-PET polyblended polymers. The molar ratios of 5-sodium sulfonate dimethyl isophthalate (5-SSDMI) for three CD-PET polymers were 2, 6 and 10%, respectively. This study investigated the thermal and mechanical properties of PCPL/CD-PET polyblended materials using gel permeation chromatograph (GPC), nuclear magnetic resonance (NMR), gas chromatography (GC), potentiometer, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), scanning electron microscope (SEM), extension stress-strain measurement, density gradient method and rheometer. Experimental results of the thermal properties indicated PCPL and CD-PET molecules easily formed individual domains. PCPL and CD-PET polymers were proved to be immiscible system even when CD-PET possessed higher 5-SSDMI content. Rheological behaviour of PCPL/CD-PET polyblends exhibited negative-deviation blends (NDB). The measurements of densities showed linear variation with the blend ratio of PCPL/CD-PET polyblends. The SEM pictures displayed the blend ratio of PCPL/CD-PET was 50/50, the morphological aggregation of a larger size from 3 to 5 μm in diameter was observed. Experimental results of the mechanical properties indicated the 50/50 blend of PCPL/CD-PET showed a minimum tensile strength.

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

AbstractPoly(ethylene terephthalate‐co‐isophthalate‐co‐5‐tert‐butylisophthalate) (PETItBI) terpolymers were investigated with reference to poly(ethylene terephthalate) (PET) homopolymer and poly(ethylene terephthalate‐co‐isophthalate) (PETI) copolymers. Three series of PETItBI 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 PETItBI 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 PETItBIs 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. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 124–134, 2003

Analysis of physical properties of PET/CD‐PET polyblend hollow fiber and its kinetics of alkaline hydrolysis

AbstractCationic dyeable poly(ethylene terephthalate) (CD‐PET) was formed by copolymerizing dimethylterephthalate (DMT),5‐sodium sulfonate dimethyl isophthalate (SIPM) with a molar ratio of 2% and ethylene glycol (EG). Blends of regular poly(ethylene terephthalate) (PET) and CD‐PET were spun into hollow fibers. The fibers were then treated with aqueous NaOH. This study investigated the physical properties of PET/CD‐PET polyblend hollow fibers and their kinetic behavior of alkaline hydrolysis using differential scanning calorimetry (DSC), wide‐angle X‐ray diffraction (WAXD), the density gradient method, a gel permeation chromatograph (GPC), a rheometer, and regression analysis of the statistical method. For the alkaline hydrolysis kinetics equation of PET, CD‐PET, and PET/CD‐PET polyblend materials: − dW/dt = KCαAβ, β values of chip and POY/ FOY hollow fibers are equal to 1. Moreover, R2 of the kinetics equation of chip/POY/FOY for a from 1.09–1.35/1.08–1.32/1.06–1.29 were better than those of a = 1. Experimental results indicate that the rate constant of alkaline hydrolysis was CD‐PET hollow fiber > PET/CD‐PET polyblend hollow fibers > PET hollow fiber and FOY > POY > > Chip. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 3601–3610, 2002

Physical Properties of R-PET/CD-PET Polyblended Hollow Filaments and Their Kinetics of Alkaline Hydrolysis

Cationic dyeable poly(ethylene terephthalate) (CD-PET) was formed by copolymerizing dimethylterephthalate (DMT),5-sodium sulfonate dimethyl isophthalate (SIPM) with a molar ratio of 2% and ethylene glycol (EG). Blends of regular poly(ethylene terephthalate) (R-PET) and CD-PET were spun into hollow filaments. The filaments were then treated with aqueous NaOH. This study investigated the physical properties of R-PET/CD-PET polyblended hollow filaments and their kinetic behavior of alkaline hydrolysis using differential scanning calorimetry (DSC), wide angle x-ray diffraction (WAXD), the density gradient method, gel permeation chromatography (GPC), rheometer measurement and statistical analysis using the regression method. Experimental results indicate that the rate constant of alkaline hydrolysis was CD-PET hollow filaments >R-PET/CD-PET polyblended hollow filaments > R-PET hollow filaments. For the alkaline hydrolysis kinetics equation of R-PET, CD-PET/R-PET polyblended and CD-PET hollow filaments: −dW/dt=KCαAβ, β is equal to 1. Moreover, R2 of the kinetics equation for α from 1.06∼1.29 was better than that of α=1.

Synthesis, Structure, and Properties of Core-Terminated Hyperbranched Polyesters Based on Dimethyl 5-(2-Hydroxyethoxy)isophthalate

The molecular weight of hyperbranched polyesters, prepared by condensation polymerization of the AB2 monomer dimethyl 5-(2-hydroxyethoxy)isophthalate in the presence of either a B3 core (trimethyl 1,3,5-benzenetricarboxylate) or a B2 core (dimethyl isophthalate), was controlled by varying the core-to-monomer ratio. During polymerization polycondensation, cyclization and core-termination reactions occurred in competition. The polyester's weight-average molecular weight continued to increase even after complete consumption of the A groups by cyclization and core termination, which is postulated to result from a redistribution of polymer chains by ester−ester interchange reactions. The polymers are soluble in common organic solvents, and solutions have characteristically low intrinsic viscosities. The physical characterization of these polymers is reported.

Studies on the chemical, physical and mechanical properties of high-solids clearcoats prepared from hydroxyl-terminated isophthalate-based oligoesters and a melamine resin

A series of high-solids (solvent-free) clearcoats was prepared from hydroxyl-terminated isophthalate-based oligoesters and the hexakis(methoxymethylol)melamine resin (HMMM). The oligoesters, which were used as binders, were prepared via a transesterification reaction of dimethyl isophthalate (DI) under various molar ratios R (=mol ratio diols/diester) with a mixture of 1,6-hexanediol (HD) and 2-methyl-1,3-propanediol (MP). Mixtures of the two diols of different composition R d (=mol ratio HD/MP), were used as well. An attempt was made to investigate and correlate the chemical, physical and mechanical properties of the formulated solvent-free clearcoats to: (a) the amount of the cross-linker (melamine resin); (b) the curing conditions (time and temperature); (c) the synthetic parameters applied in the preparation (via transesterification) of the oligoesters (e.g. excess of the diols in reaction with the DI and the molar ratio between the two diols, the species of the Lewis acid catalyst). The properties of all the new formulated high-solids clearcoats were compared to those of a reference clearcoat and their cross-linking was correlated to their chemical structure and composition as well as to their T g values. It was found that the R and R d values applied in the synthesis of the oligoesters (binders) significantly affected the performance of their corresponding clearcoats. More specifically, the clearcoats obtained from binders where 3< R<4, combined an enhanced processability, higher values of non-volatiles (∼80%) (lower VOC content) and better or comparable chemical, physical and mechanical properties (e.g. impact resistance, gasoline resistance, mar resistance, flexibility and pencil hardness) upon comparison to those of the reference clearcoat.

Polyether‐amide segmented copolymers based on ethylene terephthalamide units of uniform length

AbstractSegmented copolymers were synthesized using the crystallizable bisesterdiamide segment (N,N′‐bis(p‐carbomethoxybenzoyl)ethanediamine) T2T‐dimethyl (a one‐and‐a‐half repeating unit of nylon 2,T) and poly(tetramethyleneoxide) segments. Poly(tetramethyleneoxide) (PTMO) is amorphous and has a low Tg. The segment length was varied from 650 to 2800 g/mol by extending PTMO650 using dimethyl isophthalate. The polymers were synthesized in the melt, and test samples were prepared by injection molding. The melting behavior, as well as the torsion modulus spectrum as a function of temperature, were studied using DSC and DMA, respectively. The T2T‐PTMO polymers were found to have sharp glass (Tg) and flow transitions (Tfl), and the modulus at the rubbery plateau appeared to be virtually temperature independent. The Tg value was found to be independent of the diamide concentration, thus indicating that the T2T segments were fully crystallized. The Tfl was found to decrease with increasing soft segment length; this was ascribed to a “solvent” effect of the amorphous phase of the crystalline T2T units. The difference between the melting and crystallization temperatures was found to be low, thus suggesting that on cooling, there is a high rate of crystallization. When ethanediol was added as a T2T segment extender, amide‐ester‐amide segments were introduced. These amide‐ester‐amide segments form a separate lamellar phase with a much higher melting temperature (&gt;300°C). It was found that the crystallization rate of the T2T units was enhanced by the presence of the amide‐ester‐amide segments, indicating that upon cooling, the crystallized amide‐ester‐amide segments form the nucleation sites for the nonextended T2T segments. © 2001 John Wiley &amp; Sons, Inc. J Appl Polym Sci 80: 1173–1180, 2001

Studies on the synthesis of hydroxyl-terminated isophthalate-based oligoesters via transesterification reaction

A series of isophthalate-based oligoesters was synthesized via the transesterification reaction of dimethyl isophthalate (DI) with various aliphatic diols under different diol(s)/diester molar ratios. The effect of a series of reaction parameters, such as the diols/diester molar ratio, the molar ratio of the diols in the reaction mixture, the species of the diol, the reaction time, the heating procedure, and the species and the amount of the Lewis acid catalyst, on the physical state, the polydispersity, the Mn, the viscosity and the non-volatiles by weight (NVW) of the synthesized oligoesters was studied. A new synthetic procedure for the synthesis of high-solids liquid oligoesters in high yields and high conversions via the transesterification reaction is proposed. The properties of a reference solid oligoester (RefOL) derived from the reaction of DI with the 1,6-hexanediol (HD) (mol ratio DI/HD=1/1.43), were compared to those of a high-solids liquid oligoester (L-311) prepared from the transesterification of DI with a mixture of HD and 2-methyl-1,3-propanediol (MP) (mol ratio DI/HD/MP=1/1.50/1.50). The new high-solids liquid oligoester (L-311) presented more enhanced physical properties than its solid counterpart and owing to its improved processability is expected to be a very promising candidate when used as a binder for the preparation of mar-resistant clearcoats or pigmented coatings.

Segmented copolyetheresteraramids with extended poly(tetramethyleneoxide) segments

Segmented copolymers with crystallizable uniform p-phenyleneterephthalamide ester units and soft poly(tetramethyleneoxide) (PTMO) segments were synthesized by polycondensation. Long PTMO (>1000g/mol) segments are known to crystallize around room temperature which reduces the low temperature flexibility of the copolymers. The PTMO crystallization was reduced by incorporating chemical irregularity. PTMO1000–9000 segments having a reduced tendency to crystallize are formed by extending PTMO650 or PTMO1000 with dimethyl terephthalate or dimethyl isophthalate. Furthermore modified PTMO segments (PTMOm: 15wt% of methyl side groups) were used. The thermal and dynamic mechanical properties of the copolymers were studied with DSC and DMA, respectively. In addition, the PTMO crystallization was studied with synchrotron WAXS measurements. PTMOm segments melt about 20°C lower than PTMO. PTMO1000, DMT and DMI extended PTMO1000 and PTMOm strain crystallize reversibly, while PTMO1400 and longer strain crystallize irreversibly. Reversible strain-induced crystallization of the PTMO phase gives the polymers a relatively high tensile strength combined with a good recovery from tensile deformation. The glass transition temperature of the polymers is not increased by incorporation of the stiff terephthalic or isophthalic units in the PTMO phase. The p-phenyleneterephthalamide ester units crystallize fast and nearly completely due to their uniform length. Even at a concentration of only 3wt% of p-phenyleneterephthalamide ester units dimensionally stable polymers with a relatively high melting temperature were formed.

Synthesis and crystallization behaviors of modified PET copolymers

A series of random copolyesters having various compositions were synthesized by bulk copolymerization of bishydroxyethyl terephthalate (BHET) with 1,4-cyclohexane dimethanol (CHDM) or dimethyl isophthalate (DMI). CHDM and DMI content was less than 10 wt%. For the synthesized copolyesters, isothermal crystallization rate, melting behavior, and equilibrium temperature were investigated by calorimetry and by Avrami and Hoffman-Weeks equation. Crystalline lattice and morphology were studied by WAXD and SEM. Regardless of the composition, the value of the Avrami exponent was about 3, which indicates that crystallization mechanism of the copolyester was similar to those of PET homopolymer. Incoporation of CHDM or DMI units in PET backbone decreased the crystallization rate of the copolyesters. Surface free energy of copolyesters was evaluated using the newly proposed equation. The value of surface free energy was about 189×10−6 J2/m4 regardless of comonomer contents. This result is in good agreement with that of PET homopolymer.

Thermal behavior and tensile properties of poly(ethylene terephthalate-co-ethylene isophthalate)

Poly(ethylene terephthalate) (PET) and poly(ethylene isophthalate) (PEI) homopolymers were synthesized by the two-step melt polycondensation process of ethylene glycol (EG) with dimethyl terephthalate (DMT) and/or dimethyl isophthalate (DMI), respectively. Nine copolymers of the above three monomers were also synthe- sized by varying the mole percent of DMI with respect to DMT in the initial monomer feed. The thermal behavior was investigated over the entire range of copolymer com- position by differential scanning calorimetry (DSC). The glass transition (Tg), cold crystallization (Tcc), melting (Tm), and crystallization (Tc) temperatures have been determined. Also, the gradually increasing proportion of ethyleno-isophthalate units in the virgin PET drastically differentiated the tensile mechanical properties, which were determined, and the results are discussed. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 78: 200 -207, 2000