Radiation‐induced crosslinking of acetylene‐impregnated polyesters. II. Effects of preirradiation crystallinity,molecular structure,and postirradiation crosslinking on mechanical properties

Electron beam‐irradiated crosslinking has been studied in a series of acetylene‐impregnated polyesters and amorphous copolyesters, including poly(ethylene terephthalate) (PET), poly(butylene terephthalate) (PBT), poly(cyclohexane dimethylene terephthalate) (PCDT), and poly(cyclohexane dimethylene terephthalate‐co‐ethylene terephthalate) (P(CDT‐co‐ET)) having 29 and 60 wt % ethylene terephthalate (ET). The extent of crosslinking was observed by gel fraction measurements and was found to be significantly influenced by the aliphatic chain content of the polyesters (PET < PBT < PCDT). In addition, as the preirradiation crystallinity of the polyesters was reduced, the extent of acetylene‐enhanced crosslinking was greatly raised. Decreases in the postirradiation crystalline melting temperature and degree of crystallinity were observed in all the polyesters, using differential scanning calorimetry measurements. Particularly significant findings have been the shift in the glass‐transition temperatures (Tg) to higher temperatures and the decrease in loss tangents at higher temperatures, both of which confirm that crosslinking has taken place. The storage moduli (E′) in the rubbery plateau region of PCDT and P(CDT‐co‐ET) were significantly affected by irradiation dose. Increased network tightness in postirradiated PBT and PCDT films was also inferred from melt‐rheology measurements, in which stress relaxed more slowly following a stepped strain. Improvements in the mechanical properties of the irradiated polyesters and copolyesters were clearly evidenced by the increased modulus at higher temperatures, observed using dynamic mechanical thermal analysis and melt‐rheology methods. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 4476–4490, 2006     

Surface grafting polymerization of N‐vinyl‐2‐pyrrolidone onto a poly(ethylene terephthalate) nonwoven by plasma pretreatment and its antibacterial activities

The objective of this research was the surface grafting polymerization of biocompatible monomer N‐vinyl‐2‐pyrrolidone (NVP) onto a plasma‐treated nonwoven poly(ethylene terephthalate) (PET) substrate with ultraviolet (UV)‐induced methods. The effects of various parameters, such as the monomer concentration, reaction time, initiator (ammonium peroxodisulfate) concentration, and crosslinking agent (N,N′‐methylene bisacrylamide) concentration, on the grafting percentage were studied. The grafting efficiency of the modified nonwoven PET surfaces reached a maximum at 50 min of UV irradiation and with a 30 wt % aqueous NVP solution. After the plasma activation and/or grafting, the hydrophobic surface of the nonwoven was modified into a hydrophilic surface. NVP was successfully grafted onto nonwoven PET surfaces. The surface wettability showed that the water absorption of NVP‐grafted nonwoven PET (NVP‐g‐nonwoven PET) increased with increasing grafting time. NVP‐g‐nonwoven PET was verified by Fourier transform infrared spectra and scanning electron microscopy measurements. An antibacterial assessment using an anti‐Staphylococcus aureus test indicated that S. aureus was restrained from growing in NVP‐g‐nonwoven PET. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 803–809, 2006     

Strain‐induced crystallization in uniaxially drawn PETG plates

The copolyester poly(ethylene glycol‐co‐cyclohexane‐1,4‐dimethanol terephthalate) (PETG) is used industrially as an uncrystallizable polymer, whereas PET is an inherently crystallizable polymer. Nevertheless, a crystalline phase could appear in the material. To create a strain‐induced crystalline phase in an initially amorphous PETG material, plates were placed in the heating chamber of a tensile machine at 100°C and uniaxially drawn to obtain different samples with various draw ratios. During DSC analysis of highly drawn samples, perturbations of the baseline appear above the glass‐transition temperature, consisting of weak exothermic and endothermic phenomena. Comparison of DSC and X‐ray diffraction analysis of drawn PETG and PET shows that a strain‐induced crystalline phase appears in this copolyester. A spherulitic superstructure could also appear after lengthy annealing. Analysis of this semicrystalline material allowed estimation of the degree of crystallinity, about 3% after a drawing at high draw ratio and about 11% for undrawn annealed material. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 3405–3412, 2001     

Radiation grafting of acrylic acid/N‐vinyl pyrrolidone binary mixture onto poly(ethylene terephthalate) fabric and growth of human mesenchymal stem cell

Radiation grafting of acrylic acid (AA)/N‐vinyl pyrrolidone (NVP) binary mixture onto poly(ethylene terephthalate) (PET) knittings was investigated by preirradiation technique. The influence of the grafting conditions, such as monomer composition, reaction temperature, and the effect of storage time with temperature after irradiation on the degree of grafting was determined. ATR‐FTIR spectroscopy analysis of the grafted knittings confirmed the existence of amide group of NVP in the knittings. The concentration of peroxides and effect of storage time on peroxide concentration were also determined by 2,2‐Diphenyl‐1‐picrylhydrazyl at different temperatures. There was an increase in surface roughness of grafted PET in comparison to virgin PET as determined by atomic force microscopy and scanning electron microscopy. The grafted knittings were subsequently immobilized with collagen Type I which was further apt for the study of growth and morphology of human mesenchymal stem cell (hMSC). The immobilization of collagen on PET knittings has provided an excellent surface for the growth of hMSCs. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Microstructural modifications in uniaxially hot‐drawn polycyclohexylene terephthalate films

Semi‐aromatic thermoplastic polycyclohexylene terephthalate (PCT), initially wholly amorphous, was uniaxially drawn to study microstructural modifications as the appearance of the strain‐induced (S.I.) crystalline phase. Polyethylene terephthalate (PET) and poly(ethylene glycol‐co‐cyclohexane‐1,4‐dimethanol terephthalate) (PETG) are considered as reference materials in this work. In polycyclohexylene terephthalate (PCT) the presence of a saturated ring (which is not quite as rigid as the aromatic ring) modifies the characteristics of both thermal and S.I. crystallization. Samples with various draw ratios (drawing of PCT films is performed at T > T_g) were analyzed by Modulated Differential Scanning Calorimetry, wide angle X‐ray scattering, and birefringence measurements. In drawn PCT films, an S.I. crystalline phase appears continuously with the draw ratio and reaches 35%. For this polymer and for the highest draw ratio, the “true” amorphous fraction practically disappears. The material is composed only of the S.I. crystalline phase and the “rigid” amorphous phase. Polym. Eng. Sci. 44:509–517, 2004. © 2004 Society of Plastics Engineers.     

Synthesis of pH‐responsive polyethylene terephthalate track‐etched membranes by grafting hydroxyethyl‐methacrylate using atom‐transfer radical polymerization method

pH‐responsive polyethylene terephthalate (PET) track‐etched membranes were synthesized by grafting 2‐hydroxyethyl‐methacrylate (HEMA) on the surface of the membrane via atom transfer radical polymerization. The controllability of grafting polymerization of HEMA on membrane surface is systematically investigated. The pH‐responsive characteristics of PET‐g‐poly(2‐hydroxyethyl‐methacrylate) (PHEMA) gating membranes with different grafted PHEMA chain lengths are measured by tracking the permeation of water solution with different pH values. The results show that the grafting polymerization is controllable, and the permeation of grafted membranes is affected by the grafted PHEMA chain lengths on the surface of membrane. The results also demonstrate that the grafted PET membranes exhibit reversible pH‐response permeation to environmental pH values. Desired pH‐responsive membranes are obtained by controlling the grafted PHEMA chain lengths via atom transfer radical polymerization method. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40912.     

Poly(ethylene terephthalate)/poly(ethylene glycol‐co‐1,3/1,4‐cyclohexanedimethanol terephthalate)/clay nanocomposites: Effects of biaxial stretching

In this study, we fabricated poly(ethylene terephthalate) (PET)/clay, PET/poly(ethylene glycol‐co‐1,3/1,4‐cyclohexanedimethanol terephthalate) (PETG), and PET/PETG/clay nanocomposite plates and biaxially stretched them into films by using a biaxial film stretching machine. The tensile properties, cold crystallization behavior, optical properties, and gas and water vapor barrier properties of the resulting films were estimated. The biaxial stretching process improved the dispersion of clay platelets in both the PETG and PET/PETG matrices, increased the aspect ratio of the platelets, and made the platelets more oriented. Thus, the tensile, optical, and gas‐barrier properties of the composite films were greatly enhanced. Moreover, strain‐induced crystallization occurred in the PET/PETG blend and in the amorphous PETG matrix. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42207.     

Gamma radiation‐induced graft copolymerization of styrene onto poly(ethyleneterephthalate) films

Gamma radiation‐induced graft copolymerization of styrene onto poly(ethylene terephthalate) (PET) films was studied using simultaneous irradiation technique. The effects of grafting conditions on the degree of grafting were investigated. The grafting conditions include monomer concentration, irradiation dose, dose rate, and the type of solvent. Moreover, the effect of the addition of crosslinking agents [i.e., divinylbenzene (DVB) and triallyl cyanurate (TAC)] having various concentrations were also investigated. The degree of grafting was found to be greatly dependent on the grafting conditions. Of the three diluents employed, methylene chloride was found to drastically enhance the degree of grafting. The order of dependence of the initial rate of grafting on the monomer concentration was found to be 2.2. The grafted PET films were identified by FTIR spectroscopy and characterized by X‐ray diffraction (XRD). © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 77: 1003–1012, 2000     

Effect of winding speed on the structure and properties of as‐spun poly(trimethylene 2,6‐naphthalenedicarboxylate) fibers as compared to poly(ethylene terephthalate) fibers

We present a comparative study of melt spinning of poly(trimethylene 2,6‐naphthalenedicarboxylate) (PTN) and poly(ethylene terephthalate) (PET) fibers with respect to the effect of winding speed (2000–6000 m/min): Structural changes were followed by X‐ray analysis, calorimetry, and measurements of density, boiling water shrinkage, and birefringence. As‐spun PTN fibers exhibited a low degree of crystallinity at relatively low speeds (< 2000 m/min). An increase in winding speed up to 6000 m/min only resulted in a minor enhancement of crystallinity and orientation. The small change of structural parameters accounted for the fact that tenacity and modulus did not rise significantly with increasing winding speed, contrary to the PET fibers. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 2489–2497, 2002     

Surface structures of solvent‐cast films prepared from poly(ethylene oxide)‐segmented nylons

The surface structures of three kinds of poly(ethylene oxide)‐segmented nylon (PEO‐Ny) films prepared by the solvent‐cast method were investigated with electron spectroscopy for chemical analysis (ESCA). The PEO‐Ny's used were high‐crystalline PEO‐segmented poly(iminosebacoyliminohexamethylene), low‐crystalline PEO‐segmented poly(iminosebacoylimino‐m‐xylene), and amorphous PEO‐segmented poly(iminoisophthaloyliminomethylene‐1,3‐cyclohexylenemethylene), and the PEO contents in the bulk polymers were approximately 10 wt %. The ESCA results showed that the PEO segment was enriched on the top surfaces of all the films, and the degrees of enrichment were different. The mechanism of the PEO enrichment was examined. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 10–16, 2002     

Crystallization kinetics of poly(1,4‐butylene‐co‐ethylene terephthalate)

The crystallization kinetics of poly(butylene terephthalate) (PBT), poly(ethylene terephthalate) (PET), and their copolymers poly(1,4‐butylene‐co‐ethylene terephthalate) (PBET) containing 70/30, 65/35 and 60/40 molar ratios of 1,4‐butanediol/ethylene glycol were investigated using differential scanning calorimetry (DSC) at crystallization temperatures (T_c) which were 35–90 °C below equilibrium melting temperature . Although these copolymers contain both monomers in high proportion, DSC data revealed for copolymer crystallization behaviour. The reason for such copolymers being able to crystallize could be due to the similar chemical structures of 1,4‐butanediol and ethylene glycol. DSC results for isothermal crystallization revealed that random copolymers had a lower degree of crystallinity and lower crystallite growth rate than those of homopolymers. DSC heating scans, after completion of isothermal crystallization, showed triple melting endotherms for all these polyesters, similar to those of other polymers as reported in the literature. The crystallization isotherms followed the Avrami equation with an exponent n of 2–2.5 for PET and 2.5–3.0 for PBT and PBETs. Analyses of the Lauritzen–Hoffman equation for DSC isothermal crystallization data revealed that PBT and PET had higher growth rate constant G_o, and nucleation constant K_g than those of PBET copolymers. © 2001 Society of Chemical Industry     

Thermal properties and crystalline structure of liquid crystalline poly(ethylene terephthalate‐co‐2(3)‐chloro‐1,4‐phenylene terephthalate)

Thermal properties and crystalline structure of liquid crystalline (LC) poly(ethylene terephthalate‐co‐2(3)‐chloro‐1,4‐phenylene terephthalate) [copoly(ET/CPT)] were investigated using differential scanning calorimetry (DSC), thermogravimetry (TGA), limiting oxygen index (LOI) measurement, electron dispersive X‐ray analysis (EDX), X‐ray diffractometry, and infrared spectrometry (IR). The thermal transition temperatures of copoly(ET/CPT) were changed with the composition. Copoly(ET/CPT) showed two thermal decomposition steps and the residues at 700°C and LOI values of copoly(ET/CPT) were almost proportional to its chlorine content. The activation energy of thermal decomposition of LC units was very low compared to that of poly(ethylene terephthalate)(PET) units. Crystal structure of copoly(ET/CPT) (20/80) was of triclinic system with the lattice constants of a = 9.98 A?, b = 8.78 A?, c = 12.93 A?, α = 97.4°, β = 96.1°, and γ = 90.8°, which is very close to that of poly(chloro‐p‐phenylene terephthlate) (PCPT) with the lattice constants of a = 9.51 A?, b = 8.61 A?, c = 12.73 A?, α = 96.8°, β = 95.4°, and γ = 90.8°. When copoly(ET/CPT)(50/50) was annealed at 220°C in vacuum, crystallization induced sequential reordering (CISR) was not observed but the heat of fusion was slightly increased due to the increase of the trans isomer content in PET units. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 1286–1294, 2002; DOI 10.1002/app.10451     

Chemical grafting of aniline and o‐toluidine onto poly(ethylene terephthalate) fiber

Graft copolymerization of poly(aniline) and poly(o‐toluidine) onto poly(ethylene terephthalate) fiber was conducted by using peroxydisulfate as a lone initiator under nitrogen atmosphere at various experimental conditions in aqueous hydrochloric acid medium. The grafting of poly(aniline) and poly(o‐toluidine) onto poly(ethylene terephthalate) fiber was verified by recording cyclic voltammetry of the grafted fiber, conductivity measurements, and thermal analysis. Graft parameters—such as % grafting, % efficiency, and the rate of grafting—were followed. Grafting was always accompanied by homopolymerization. The rate of homopolymerization was also followed in all experimental conditions. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 73: 121–128, 1999     

Insights into process–structure–property relationships of poly(ethylene terephthalate) industrial yarns by synchrotron radiation WAXD and SAXS

Synchrotron radiation wide angle X‐ray diffraction (WAXD) and small angle X‐ray scattering (SAXS) were performed to study the structures of four typical types of poly(ethylene terephthalate) (PET) industrial yarns. Three‐dimensional structural models of the yarns and comprehensive insights into the process–structure–property relationships were gained. High spinning speed, low draw ratio, and high heat‐setting temperatures lead to HMLS yarns with high crystallinity, high amorphous orientation, densely packed lamellar stacks, and a small tilting angle of crystalline lamellae. High draw ratio tends to result in PET industrial yarns with large long period and a large tilting angle of lamellae. Heat‐setting process has a significant influence on the amorphous orientation and crystalline structures, such as crystallinity, crystallite size, as well as crystal grain number. Compared with other structure characteristics, amorphous orientation plays a more important role in determining the tenacity, initial modulus, part load elongation, ultimate elongation, as well as shrinkage of PET industrial yarns. The crystal grain number seems to have an effect on the initial modulus, while the long period influences the elongation of the yarns to some extent. In addition, the small tilting angle of crystalline lamellae may relate to the dimensional stability of PET yarns. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42512.     

The effect of N,N-dimethylformamide and polymer grafting on the morphology of polyester fibers in fabric substrate

Photo-induced graft polymerization of acrylic acid (AA) and methyl acrylate (MA) in the liquid and vapor phase, respectively, onto N,N-dimethyformamide (DMF)-pretreated poly(ethylene terephthalate) (PET) fibers in fabric substrate was studied. The effect of various synthesis conditions and DMF pretreatment on the graft yields on PET was investigated. The internal morphology and properties of DMF-pretreated and grafted PET fibers in the fabric were characterized using density and birefringence measurements, differential thermal analysis (DTA), Fourier transform infrared spectroscopy (FTIR), dyeing methods, and critical dissolution times. The grafting was promoted by increasing DMF pretreatment temperature and the amount of DMF retention in the PET. Increasing biacetyl and monomer flow time and irradiation time enhanced grafting. DMF pretreatment resulted in increases in total void content, degree of crystallinity, trans-isomer content, chain folding, segmental mobility, and molecular packing of the PET, but caused decreases in its amorphous orientation, intermolecular forces, and individual void size through longitudinal shrinkage, lateral swelling, and removal of oligomers. Subsequent graft copolymerization led to further changes in the internal morphology and properties of the PET. PET grafted with AA had a higher cohesive energy density, lower degree of molecular packing, and larger individual void size, but less total void content, lower segmental mobility, less chain orientation, and a lower degree of crystallinity. PET grafted with MA showed increases in total void content, individual void size, segmental mobility, and molecular packing, but showed decreases in chain orientation and degree of crystallinity. © 1996 John Wiley & Sons, Inc.     

Controlling sandwich‐structure of PET microcellular foams using coupling of CO2 diffusion and induced crystallization

Controlling sandwich‐structure of poly(ethylene terephthalate) (PET) microcellular foams using coupling of CO₂ diffusion and CO₂‐induced crystallization is presented in this article. The intrinsic kinetics of CO₂‐induced crystallization of amorphous PET at 25°C and different CO₂ pressures were detected using in situ high‐pressure Fourier transform infrared spectroscopy and correlated by Avrami equation. Sorption of CO₂ in PET was measured using magnetic suspension balance and the diffusivity determined by Fick's second law. A model coupling CO₂ diffusion in and CO₂‐induced crystallization of PET was proposed to calculate the CO₂ concentration as well as crystallinity distributions in PET sheet at different saturation times. It was revealed that a sandwich crystallization structure could be built in PET sheet, based on which a solid‐state foaming process was used to manipulate the sandwich‐structure of PET microcellular foams with two microcellular or even ultra‐microcellular foamed crystalline layers outside and a microcellular foamed amorphous layer inside. © 2011 American Institute of Chemical Engineers AIChE J, 58: 2512–2523, 2012     

Poly(ethylene‐co‐methacrylic acid)–lithium ionomer as a compatibilizer for poly(ethylene terephthalate)/linear low‐density polyethylene blends

Poly(ethylene terephthalate) (PET)/linear low‐density polyethylene (LLDPE) blends (75/25), with contents of poly(ethylene‐co‐methacrylic acid) partially neutralized with lithium (PEMA–Li) that were systematically changed from 0 to 45% relative to the LLDPE, were obtained by direct injection molding in an attempt to (1) ameliorate the performance of the binary blend and (2) find the best compatibilizer content. PEMA–Li did not modify the PET or LLDPE amorphous‐phase compositions or the crystalline content of PET. However, PEMA–Li did lead to a nucleation effect and to the presence of a second smaller and less perfect crystalline structure. PET induced a fractional crystallization in LLDPE that remained in the presence of PEMA–Li and reduced the crystallinity of LLDPE. The ternary blends showed two similar dispersed LLDPE and PEMA–Li phases with small subparticles, probably PET, inside. The compatibilizing effect of PEMA–Li was clearly shown by the impressive increase in the break strain, along with only small decreases in the modulus of elasticity and in the tensile strength. With respect to the recycling possibilities of LLDPE, a ternary blend with the addition of 22.5% PEMA–Li, which led to very slight modulus and yield stress decreases with respect to the binary blend and a break strain increase of 480%, appeared to be the most attractive. However, the highest property improvement appeared with the addition of 37.5% PEMA–Li, which led to elasticity modulus and tensile strength decreases of only 9%, along with a very high break strain increase (760%). © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1322–1328, 2003     

Synthesis of well‐defined responsive membranes with fixable solvent responsiveness

A versatile method is described to synthesize a new family of solvent‐responsive membranes whose response states can be not only tunable but also fixable via ultraviolet (UV) irradiation induced crosslinking. The atom transfer radical polymerization (ATRP) initiator 2‐bromoisobutyryl bromide was first immobilized on the poly(ethylene terephthalate) (PET) track‐etched membrane followed by room‐temperature ATRP grafting of poly(2‐hydroxyethyl methacrylate) (PHEMA) and poly(2‐hydroxyethyl methacrylate‐co‐2‐(dimethylamino)ethyl methacrylate) (P(HEMA‐co‐DMAEMA)) respectively. The hydroxyl groups of PHEMA were further reacted with cinnamoyl chloride (a photosensitive monomer) to obtain photo‐crosslinkable PET‐g‐PHEMA/CA membrane and PET‐g‐P(HEMA/CA‐co‐DMAEMA) membrane. The length of grafted polymer chains was controllable by varying the polymerization time. X‐ray photoelectron spectroscopy, Fourier transform infrared spectroscopy in attenuated total reflection and thermogravimetric analysis were employed to characterize the resulting membranes. The various membrane surface morphologies resulting from different states of the grafted chains in water and dimethylformamide were characterized by scanning electron microscopy. It was demonstrated that the grafted P(HEMA/CA‐co‐DMAEMA) chains had more pronounced solvent responsivity than the grafted PHEMA/CA chains. The surface morphologies of the grafted membranes could be adjusted using different solvents and fixed by UV irradiation crosslinking. © 2014 Society of Chemical Industry     

Radiation‐induced graft copolymerization of acrylic acid/acrylonitrile onto LDPE and PET films and its biodegradability

Graft copolymerization of acrylic acid/acrylonitrile (AAc/AN) comonomer onto low‐density poly(ethylene) (LDPE) and poly(ethylene terephthalate) (PET) films using direct radiation grafting technique has been investigated. The effect of different reaction conditions on the grafting yield was studied. The structure of the grafted films at different compositions was characterized by FTIR, TGA, SEM, and XRD. Biodegradation of grafted LDPE and PET was investigated by burial method in two types of Egyptian soils (agricultural and desert soils). The bacteria responsible for biodegradation were isolated and characterized, and the capacities for the growth on these polymers as substrates were compared. The isolates from agricultural soil were characterized as Pseudomonas, Alcaligenes, Bacillus, Proteus, and Enterobacter, whereas the isolates from desert soil were characterized as Alcaligenes, Bacillus, and Pseudomonas. The highest degradation rate was found to be achieved using agricultural soil. It is found that the isolated strains belonging to the genus Pseudomonas were mainly responsible for the degradation of both polymers. It has also been found that the increase of AAc ratio in the composition increases the hydrophilicity of the films and the degradation rate. PET polymer is generally found to be more resistant to the biodegradation than LDPE in the two types of soils tested. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Non‐isothermal cold crystallization kinetics and morphology of PET + SAN blends

The influence of small amounts of poly(styrene‐co‐acrylonitrile) (SAN) on the non‐isothermal cold crystallization behavior and morphology of poly(ethylene terephthalate) (PET) was investigated by dynamic‐mechanical thermal analysis, differential scanning calorimetry (DSC), optical microscopy, and scanning electron microscopy. The results indicated that SAN had a limited solubility in the amorphous phase of PET although in a larger scale a phase separation occurred. The addition of 1 wt % of SAN promoted a significant reduction in the crystallization rate of PET, acting as an antinucleating agent. The kinetics parameters were determined applying both the Ozawa and Mo approaches. Mo's model described the crystallization evolution better than the Ozawa one because it is possible to analyze the kinetic parameters in similar range of crystallinity degrees. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010