Solvent‐induced modifications in polyester yarns. I. Mechanical properties

The mechanical properties of polyester (PET) yarns, fine filament, and microdenier (original and heat‐set), treated with a trichloroacetic acid–chloroform (TCAC) mixture were investigated. The treatments were carried out in an unstrained state with various concentrations of the TCAC reagent at room temperature. The TCAC treatment on PET yarns resulted in notable changes in the tensile behavior. The TCAC‐treated yarns exhibited higher extensibility and work of rupture without much loss in strength. The improvement in elongation was less in the case of heat‐set polyester yarns due to solvent treatment. The depression of the glass transition temperature (T_g) of TCAC‐treated PET yarns, even at the minimum concentration, showed its effectiveness to plasticize the fibers and the closeness of the solubility parameter of TCAC and PET. The T_g depression favors molecular relaxation, which has resulted in a higher shrinkage percentage of TCAC‐treated PET yarns and the effective shrinkage was reached more easily for the original fine‐filament polyester (FFP) and microdenier polyester (MDP) yarns at the lowest concentration. The effects of the concentration of TCAC on the strength, elongation, yield behavior, and work of rupture on PET were also investigated. A significant plastic flow was observed in the TCAC‐treated yarns. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1500–1510, 2003     

Structural investigations of poly(ethylene terephthalate)‐graft‐polystyrene copolymer films

Structural investigations of poly(ethylene terephthalate)‐graft‐polystyrene (PET‐g‐PS) films prepared by radiation‐induced grafting of styrene onto commercial poly(ethylene terephthalate) (PET) films were carried out by FTIR, X‐ray diffraction (XRD), and differential scanning calorimetry (DSC). The variation in the degree of crystallinity and the thermal characteristics of PET films was correlated with the amount of polystyrene grafted therein (i.e., the degree of grafting). The heat of melting was found to be a function of PET crystalline fraction in the grafted films. The grafting is found to take place by incorporation of amorphous polystyrene grafts in the entire noncrystalline (amorphous) region of the PET films and at the surface of the crystallites. This results in a decrease in the degree of crystallinity with the increase in the degree of grafting, attributed to the dilution of PET crystalline structure with the amorphous polystyrene, without almost any disruption in the inherent crystallinity. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 1949–1955, 2002; DOI 10.1002/app.10515     

Studies on acrylic acid–grafted polyester fabrics by electron beam preirradiation method. I. Effects of process parameters on graft ratio and characterization of grafting products

Polyester fabrics were preirradiated by electron beam in air and then grafted by acrylic acid (AA) without excluding oxygen. Effects of preirradiation dose, monomer concentration, reaction temperature, storage time, sulfuric acid, and Mohr's salt were investigated in detail and are discussed. The results suggest that it is practicable and effective to graft AA onto polyester fabrics by means of the preirradiation method. FTIR and SEM were used to characterize AA‐grafted polyester fabrics. A new band appearing at 1546 cm^?1 in the FTIR spectrum implies that AA was indeed introduced onto PET macromolecules. Changes of the diameter and the surface structure of fabric fibers presented in SEM micrographs make it clear that a layer of grafted poly(acrylic acid) was formed on the surface of these PET fibers. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 3931–3938, 2003     

Preparation and properties of water‐soluble polyester surfactants. III. Preparation and wetting properties of polyethylene glycol–polydimethylsiloxane polyester surfactants

A novel series of water‐soluble polyethylene glycol–polydimethylsiloxane (PEG–Silicone) polyesters was prepared by reacting organopolysiloxane with hydroxyl‐terminated polyester. The polyesters are obtained by the polymerization of maleic anhydride (MA) and PEGs (number‐average molecular weights M _n = 2000–10,000). FTIR, ¹H‐NMR, and elemental analysis were employed to characterized the structures of these compounds. These compounds exhibit good surface activities such as surface tension and low foaming. The influence of the PEG–Silicone polyester surfactants introduced at various concentrations (0.1–2 wt %) was examined by the contact angle method. The measurements performed with various solid substrates indicated that, at comparable concentrations, the PEG–Silicone polyester surfactants were shown to be more efficient for wetting PET and glass. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 1236–1241, 2003     

Miscibility study on blend of thermotropic liquid crystalline polymers and polyester

The miscibility of thermotropic liquid crystalline polymers (TLCPs) and polyester blends was investigated with thermal and morphological analyses, as well as transesterification. TLCPs composed of 80 mol % para‐hydroxybenzoate (PHB) and 20 mol % poly(ethylene terephthalate) (PET) or 60 mol % PHB and 40 mol % PET, and polyesters such as PET and poly(ethylene 2,6‐naphthalate) (PEN) were melt blended in an internal mixer. DSC analyses were performed to investigate the thermal transition behavior and to obtain thermodynamic parameters. All the blends showed only a single glass‐transition temperature, which means they are partially miscible in the molten state. The Flory–Huggins interaction parameter was calculated employing the Nishi–Wang approach, and negative values were obtained except for the P(HB8‐ET2)/PEN blends. Transesterification was investigated using ¹H‐NMR, and the change of chemical shift compared to pure PET or P(HB‐ET)s was observed in the P(HB‐ET)/PET blends. An intermediate chemical shift value (4.83 ppm) was observed in the P(HB6‐ET4)/PEN blends, which indicates transesterification occurred. The fractured surface morphology of scanning electron micrographs showed that the interfaces between the LC droplets and matrix were not distinct. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1842–1851, 2003     

A Comprehensive Study on Physical,Mechanical, and Thermal Properties of Poly(Ethylene Terephthalate) Filled by Micro‐ and Nanoglass Flakes

Polyethylene terephthalate (PET) composites containing micro‐ and nanoglass flakes were prepared by melt blending. The percentage of nanoglass flakes was varied from 0.5, 1, 2, and 3 wt% and the concentration of microglass flakes was 1, 3, and 5 wt%. The effect of glass flake on morphology, physical, mechanical, and thermal properties of PET was studied using scanning electron microscopy (SEM), energy‐dispersive X‐ray analysis (EDXA), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), dynamic mechanical thermal analysis (DMTA), X‐ray diffraction (XRD), and tensile test. The observations showed that both types of particles were dispersed in PET, homogeneously, though microglass flakes had better dispersion compared with their nanosized counterparts. According to DSC thermogram, the crystallization rate and temperature of PET increased with incorporation of both types of glass flakes. The crystallization rate of PET was increased from 31.41% to 34.25% with the addition of 1 wt% of nanoglass flakes. Moreover, the onset of thermal degradation increased more than 9°C with the addition of micro‐ and nanoglass flakes. Based on the mechanical viewpoint, the Young's modulus of PET was improved by the addition of both micro‐ and nanoglass flakes. On the other hand, the tensile strength of PET was decreased from 45.4 MPa to 31.3 MPa using 1 wt% of nanoglass flakes. According to X‐ray diffractometry, using of micro‐ and nanoglass flakes resulted in the decrement of PET crystallites. Whereas, the size of crystallites was lower than microglass flakes, in the case of using nanoglass flakes. J. VINYL ADDIT. TECHNOL., 26:380–389, 2020. © 2019 Society of Plastics Engineers     

Melt blending of poly(ethylene terephthalate) with polypropylene in the presence of silane coupling agent

A silane coupling agent (SCA) was used as a compatibilizer for polypropylene–poly(ethylene teraphthalate) (PP–PET) blends with 20, 40, 50, and 60% PET compositions by weight. PP–PET mixtures were blended with and without an SCA by a single‐screw extruder. The effect of silane modification on the tensile and impact properties of the blends was investigated. The morphology and thermal behavior of the blends were examined with scanning electron microscopy (SEM) and differential scanning calorimetry (DSC), respectively. The presence of the SCA used in this work extensively improved the mechanical properties of the blends. Mechanical properties were found to be highly dependent on the numbers of extrusions. SEM studies showed that substantially different morphology with better adhesion existed when SCA‐treated blends were compared to nontreated PP–PET blends. The presence of individual melting temperatures of the polymers in all compositions with no significant T_m depression indicated that PET and PP were crystallized separately. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1039–1048, 2003     

Characterization of ramie yarn treated with sodium hydroxide and crosslinked by 1,2,3,4‐butanetetracarboxylic acid

Ramie yarns were treated with various concentrations of NaOH at room temperature and subsequently crosslinked with 1,2,3,4‐butanetetracarboxylic acid (BTCA). The microstructure and tensile properties of the treated yarns were characterized. X‐ray diffraction (XRD) and FTIR were used to study the crystalline structure of the resultant ramie yarns. The results showed that the maximum change in the structure of the alkali‐modified ramie took place at 16% NaOH, which would completely transform cellulose I to cellulose II. At the same time, the crystallinity index and fiber orientation decreased to the minimum value while the absorption properties were enhanced. The average degree of polymerization (DP ) of the treated ramie yarns slightly decreased after NaOH treatment. Tensile properties including tenacity, breaking elongation, and modulus of the treated yarns were also investigated. Scanning electron microscopy (SEM) was used to investigate the breakage of the treated yarns. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1857–1864, 2004     

Study on the grafting of PET onto the glass fiber surface during in situ solid‐state polycondensation

An in situ solid‐state polymerization process was developed to produce long glass fiber reinforced poly(ethylene terephthalate) (PET) composites. As reported in our last article, one advantage of this new process is that the good wetting of reinforcing fiber can be obtained for using low‐viscosity oligomer as raw materials. In this article, the grafting of PET macromolecular chain onto the surface of reinforcing glass fiber during in situ solid‐state polycondensation (SSP) will be investigated, which was believed to be another advantage for this new process and should be very important for thermoplastic composite. The reinforcing glass fiber after removing ungrafted PET from a long glass fiber reinforced PET composite by solvent extraction was investigated by SEM, pyrolysis‐gas chromatography mass spectrometry (Py‐GC/MS), DSC, and FTIR. The information from morphology of SEM photos of glass fiber surface, the spectrum of Py‐GC/MS, the melt peak at differential scanning calorimetric (DSC) curve, and the spectrum of Fourier transform infrared Raman spectroscopy (FTIR) gave a series evidence to prove the presence of grafted PET layer on the surface of silane‐coupling‐treated glass fiber. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 775–781, 2006     

A comparative study of structure–property relationships in highly oriented thermoplastic and thermotropic polyesters with different chemical structures

Structure and properties of commercially available fully oriented thermoplastic and thermotropic polyester fibers have been investigated using optical birefringence, infrared spectroscopy, wide‐angle X‐ray diffraction and tensile testing methods. The effect of the replacement of p‐phenylene ring in poly(ethylene terephthalate) (PET) with stiffer and bulkier naphthalene ring in Poly(ethylene 2,6‐naphthalate) (PEN) structure to result in an enhanced birefringence and tensile modulus values is shown. There exists a similar case with the replacement of linear flexible ethylene units in PET and PEN fibers with fully aromatic rigid rings in thermotropic polyesters. Infrared spectroscopy is used in the determination of crystallinity values through the estimation of trans conformer contents in the crystalline phase. The analysis of results obtained from infrared spectroscopy data of highly oriented PET and PEN fibers suggests that trans conformers in the crystalline phase are more highly oriented than gauche conformers in the amorphous phase. Analysis of X‐ray diffraction traces and infrared spectra shows the presence of polymorphic structure consisting of α‐ and β‐phase structures in the fully oriented PEN fiber. The results suggest that the trans conformers in the β‐phase is more highly oriented than the α‐phase. X‐ray analysis of Vectran® MK fiber suggests a lateral organization arising from high temperature modification of poly(p‐oxybenzoate) structure, whereas the structure of Vectran® HS fiber contains regions adopting lateral chain packing similar to the room temperature modification of poly(p‐oxybenzoate). Both fibers are shown by X‐ray diffraction and infrared analyses to consist of predominantly oriented noncrystalline (63–64%) structure together with smaller proportion of oriented crystalline (22–24%) and unoriented noncrystalline (12–15%) structures. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 142–160, 2006     

Molecular structure and orientation of gel‐spun polyethylene fibers

Characterization of molecular structure and orientation of six commercially available gel‐spun polyethylene fibers have been carried out using infra‐red and Raman spectroscopy, thermal and X‐ray diffraction analysis, together with optical microscopy techniques. Thermal and X‐ray diffraction analysis revealed the existence of highly oriented orthorhombic and monoclinic crystallites together with a highly oriented intermediate phase known as pseudohexagonal mesophase structure. The results suggest the existence of a three‐phase structure consisting, at room temperature, of orthorhombic and monoclinic polymorphic crystallites, oriented noncrystalline and un‐oriented noncrystalline (amorphous) phases, respectively. The crystallinity measurements have been carried out using density, thermal and X‐ray diffraction analysis together with infra‐red and Raman spectroscopy techniques whereas the molecular orientation measurements have been carried out using birefringence and polarized IR spectroscopy, respectively. The results obtained from density, thermal analysis, and Raman spectroscopy based on a simple two‐phase modeling approach lead to the overestimated amorphous fractions and appears to ignore the presence of an intermediate phase known as oriented noncrystalline structure. X‐ray analysis has also been used for the measurement of the apparent crystallite sizes. The birefringence values have been used to determine the overall orientation parameters whereas the dichroic measurements of IR bands have been used to determine the crystalline and oriented noncrystalline orientation parameters. The results show that the orthorhombic and monoclinic phases are more highly oriented than the oriented pseudohexagonally packed noncrystalline chains. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 1317–1333, 2006     

Treatment of PET nonwoven with a water vapor or carbon dioxide plasma

Gas plasma treatment of poly(ethylene terephthalate) nonwoven (NW–PET) was used to increase the hydrophilicity of single‐ and multilayer NW–PET. NW–PET was treated with a pulsatile CO₂ or with a pulsatile H₂O glow discharge. X‐ray photoelectron spectroscopy (XPS) showed significantly more oxygen with CO₂ glow‐discharge‐treated NW–PET than with H₂O glow‐discharge‐treated‐NW–PET surfaces. Moreover, the introduction rate of oxygen at a single layer of NW–PET was higher for a CO₂ than for a H₂O glow‐discharge treatment. Titration data revealed significantly higher surface concentrations of carboxylic groups for CO₂ glow‐discharge NW–PET than for H₂O glow‐discharge‐treated NW–PET. Mass spectrometry analysis revealed that the entire internal surface of a single layer of NW–PET was modified. XPS and contact measurements confirmed the modification of the internal surface of multilayers of NW–PET. H₂O and CO₂ glow‐discharge‐treated substrates consisting of six layers of NW–PET had a nonuniform surface concentration of carboxylic acid groups as determined with titration experiments. The outside layers of the substrate contained a higher surface concentration of carboxylic acid groups than did the inside layers. XPS analysis and titration data showed that the rinsing of H₂O and CO₂ glow‐discharge‐treated NW–PET with water changed the surface composition considerably. Part of the carboxylic acid group‐containing species were washed off. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 75: 480–494, 2000     

Study of the crystal structure of P(HBA/HNA)/PET blend fibers

The crystal structure of p‐hydroxybenzoate/2‐hydroxy‐6‐naphthoic acid copolyester [P(HBA/HNA)]/poly(ethylene terephthalate) (PET) blend (ACPET) fiber was studied with wide‐angle X‐ray diffraction and differential scanning calorimetry. The results showed that crystallites of P(HBA/HNA) and PET were formed in ACPET fibers; that is, some crystallites of ACPET fiber were composed of PET chains, and others were composed of P(HBA/HNA) chains. The thermal behaviors of the crystals of each component in the blend fiber were different from those of each corresponding pure component. For the fibers heat‐treated at 300 and 350°C, the degree of supercooling of P(HBA/HNA) segments in the blend fibers was the same as that of P(HBA/HNA) fiber, but the degree of supercooling of PET in the blend fibers was distinctly higher than that of pure PET fibers. Evidently, the aforementioned changes were attributable to the blending of PET with P(HBA/HNA). © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 83: 394–400, 2002     

Reaction and miscibility of two diepoxides with poly(ethylene terephthalate)

Poly(ethylene terephthalate) (PET) was melt‐blended at 270°C with two epoxy monomers, diglycidyl ether of bisphenol A (DGEBA) and 3,4‐epoxycyclohexyl‐methyl‐3,4‐epoxycyclohexyl carboxylate (ECY). Intermediate proportions of the epoxy in the range of 20–0.5 wt % were used. If the epoxy monomers were added in a high proportion (10–20%), a large fraction did not react with PET. Calorimetric experiments showed that the unreacted fractions of both epoxies were miscible with the amorphous phase of the polyester. Only one glass‐transition temperature was detected. It was depressed as the epoxy content was increased. The transition was broad when the PET component was crystalline, and it was narrow when the PET component was made amorphous by quenching of the blend. These features were confirmed by dynamic thermal mechanical analysis. As is often the case for crystalline blends, the crystallization and melting temperatures decreased when the proportion of the epoxy was increased. Concerning the reactivity of the epoxy with PET, the behavior differed according to the nature of the epoxy. The DGEBA monomer showed a low reactivity. It was not effective for the chain extension of PET, and no increase in the intrinsic viscosity was observed under the experimental conditions. However, some functionalization of the chain ends may be possible at a high concentration of the epoxy. ECY was more reactive, and the molecular weight of the processed PET increased, although the value of the commercial untreated polyester was not attained. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1995–2003, 2003     

Graft copolymerizaztion of methyl acrylate onto chitosan initiated by potassium diperiodatocuprate (III)

A novel redox system, potassium diperiodatocuprate [Cu (III)–chitosan], was employed to initiate the graft copolymerization of methyl acrylate (MA) onto chitosan in alkali aqueous solution. The effects of reaction variables such as monomer concentration, initiator concentration, pH and temperature were investigated. By means of a series of copolymerization reactions, the grafting conditions were optimized. Cu (III)–chitosan system was found to be an efficient redox initiator for this graft copolymerization. The structures and the thermal stability of chitosan and chitosan‐g‐poly(methyl acrylate) (PMA) were characterized by infrared spectroscopy (IR) and thermogravimetric analysis (TGA). In this article, a mechanism is proposed to explain the formation of radicals and the initiation. Finally, the graft copolymer was used as the compatibilizer in blends of poly(vinyl chloride) (PVC) and chitosan. The scanning electron microscope (SEM) photographs and differential scanning calorimetry (DSC) thermograms indicate that the graft copolymer improved the compatibility of the blend. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 2283–2289, 2003     

Morphology and properties of poly(ethylene terephthalate) and thermoplastic polyester elastomer blends modified in the melt by a diisocyanate chain extender and filled with a short glass fiber

The structural features and rheological, mechanical, and relaxation properties of poly(ethylene terephthalate) (PET) blends with 7–50 wt % polyester thermoplastic polyester elastomer (TPEE), a block copolymer of poly(butylene terephthalate) and poly(tetramethylene oxide), chemically modified by a diisocyanate chain extender (CE) and reinforced with 30% glass fibers (GF) were studied. The composites were obtained by reactive extrusion with a twin‐screw reactor–mixer with a unidirectional rotation of screws. The molecular–structural changes in the materials were judged against data provided by differential scanning calorimetry, scanning electron microscopy, relaxation spectrometry, and rheological analysis of the melts. Regardless of the TPEE concentration in the blends with GF‐reinforced PET, the addition of CE resulted in the growth of the indices of the mechanical properties at straining, bending, and impact loading and an increase in the melt viscosity. In addition, an increase in the average length of short GFs in the composites and an intensification of interphase adhesion in the polyester binder–GF surface system were observed. The introduction of CE promoted a slowdown in PET crystallization in the composites and intensified the interphase adhesion in the binder–GF system at temperatures higher and lower than the PET glass‐transition temperature. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45711.     

Real‐time FTIR and WAXS studies of drawing behavior of poly(ethylene terephthalate) films

The development of molecular orientation and crystallization was studied during uniaxial drawing of poly(ethylene terephthalate) (PET) films, which was immediately followed by subsequent taut annealing at the drawing temperature. The behavior was monitored in real time throughout the drawing and annealing using dynamic FTIR spectroscopy and in situ WAXS measurements using the Daresbury Synchrotron Radiation Source. Films were drawn at 80 and 85°C at varying strain rates (0.001–0.7 s⁻¹). The true stress–strain behavior was determined at each of the drawing conditions and the density and optical anisotropy of unloaded samples was measured. The IR spectra were analyzed using curve reconstruction procedures developed previously, and they showed that orientation of the phenylene groups and the trans glycol conformers occurred before significant gauche–trans conformational changes could be seen. The onset of crystallization, defined as the point that the crystalline 1 05 reflection could be first observed using WAXS, was not found to correlate with any specific change in the proportions of trans and gauche isomers nor with any feature on the stress–strain curve. However, it was clear that, for these comparatively low strain rates, crystallization occurred during the drawing process while the crosshead was moving and the draw ratio was increasing. The orientation of the crystallites was calculated from the 1 05 reflection observed in a tilted film, transmission geometry. The crystallites were found to form at a draw ratio of about 2.5 with high orientation values (P₂ > 0.8) that increased during drawing and annealing to P₂ values of 0.95, irrespective of the drawing conditions. Semiquantitative measurements of crystallinity showed that the fraction of crystalline material that developed during drawing decreased with increasing strain rate. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 79: 1825–1837, 2001     

Polymaleamide–polymaleimide networks

Polymaleamide–polymaleimide networks were obtained as films by the thermal treatment of mixtures with different ratios of an aliphatic–aromatic polymaleamide (PMA) and 4,4′‐bis(maleimidodiphenylmethane) (BMI), in N‐methyl‐2‐pyrolidinone (NMP) as a solvent. The polymaleamides were synthesized by ring‐opening polyaddition of 1,6‐hexamethylene–bisisomaleimide with 4,4′‐diaminodiphenylmethane in NMP at room temperature. The networks are infusible and insoluble in organic solvents; therefore, they were studied by solid‐state techniques such as IR, DSC, thermooptical analysis (TOA), TG/DTG analysis, and TEM. Thermal treatment of pure PMA and BMI occurs with the formation of crosslinked structures as proved by IR spectra. DSC and TOA curves show the appearance of chemical interactions between PMA and BMI in cured films and the formation of ordered morphologies, especially when BMI is the major component. TG/DTG and TEM results supported these observations. The PMA–polymaleimide network films present electrical insulator properties superior to individual polyamides or polyimides. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 779–788, 2004     

Alkali treatment of jute fibers: Relationship between structure and mechanical properties

The mechanical properties of tossa jute fibers were improved by using NaOH treatment process to improve the mechanical properties of composites materials. Shrinkage of fibers during this process has significant effects to the fiber structure, as well as to the mechanical fiber properties, such as tensile strength and modulus. Isometric NaOH‐treated jute yarns (20 min at 20°C in 25% NaOH solution) lead to an increase in yarn tensile strength and modulus of ∼ 120% and 150%, respectively. These changes in mechanical properties are affected by modifying the fiber structure, basically via the crystallinity ratio, degree of polymerization, and orientation (Hermans factor). Structure–property relationships, developed for cellulosic man‐made fibers, were used with a high correlation factor to describe the behavior of the jute fiber yarns. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 71: 623–629, 1999     

The glass transition,crystallization, and melting characteristics of a class of polyester ionomers

The glass transition temperature (T_g), crystallization, and melting character of a class of random polyester ionomers (polymer containing < 10 mol % ionic groups) were investigated. The nonlinear change of the T_g and crystallization and melting behavior were characterized using differential scanning colorimetry (DSC). The ionomers are derived from polyethylene terephathalate (PET) modified through copolycondensation with a fully neutralized sulfonate moiety (sodiosulfo) isophthalate (Na‐SIP). Significant and systematic changes in the glass transition temperature and thermal characteristics upon addition of Na‐SIP on the PET backbone were observed, indicating strong association and interaction on the ionic species. At Na‐SIP levels ≥ 4 mol %, the turn of the the glass transition temperature was found, and the same results were obtained for the samples treated either by quenching or dissolution, suggesting the presence of reversible crosslink and aggregation of the ionic species within the organic matrix. When crystallized from the healing or cooling the samples during the DSC nonisothermal crystallization run at a 10°C/min, the enthalpy of the cold crystallization and melting showed an obvious decrease with the increase of Na‐SIP content, and changes of the crystal temperature had an analogy to those of the T_g. A tune of the crystal temperature was found at Na‐SIP levels ≥ 3 mol % (see Figs. 4 , 5 , and 7 ). The experimental data were discussed in the context of the restricted mobility model of the aggregation in the ionomers. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 3660–3666, 2002